The Gram-Negative Bacilli of Medical Importance

Chapter Objectives:

• Learn the Aerobic Gram-Negative Nonenteric Bacilli
  • Pseudomonas
• Learn the related Gram-Negative Aerobic Rods
  
  • Brucella, Francisella tularensis, Bordetella pertussis, Legionella pneumophilia
• Identification and Differential Characteristics of Family Enterobacteriaceae Enterotoxins, Coliforms, Noncoliforms

• Coliform Organisms and Diseases
  • Escherichia coli, Klebsiella
• Noncoliform Lactose-Negative Enterics
  • Proteus, Morganella, Providencia, Salmonella, Shigella, Yersinia, Pasteurella multocida, Haemophilus influenzae

Endotoxin Shock
Gram negative bacteria cell wall:The adverse factor in gram-negative sepsis is the presence of an endotoxin called lipopolysaccharide (when released is a side effect of cell death. It is a pyrogenic and immune stimulating, it is also considered an endotoxin), in the outer membrane of the cell wall. Lipopolysaccharide is a potent immune stimulator. The component that accounts for the most of the adverse effects is lipid A embedded in the external layer of the membrane. This lipid A is activated only after it is liberated by bacteria that are growing or lysed by host defenses and other factors. In general, lipid A triggers the secretion of interleukins, tumor necrosis factor, and other cytokines by Macrophages. Sepsis leads to large release of LPS, and macrophages release cytokines, which cause fever, and low blood pressure, which can in turn cause organ and tissue damage.
Sepsis Symptoms: Nausea, tachycardia, low blood pressure, and fever. Can progress to respiratory failure, coma, heart failure and death. Antibiotics can compound the effects, they can cause the release of more LPS. Resistant to most antibiotics.

Gram-Negative Diseases
Bacteremia(septicemia)-is the proliferation of microorganisms in the blood. The gram-negative bacteria involved are E. Coli, Serratia marcescens, Proteus mirabilis, Enterobacter aerogenes, and Pseudomomas aeruginosa. Symptoms are produced by the endotoxins that are released from bacterial cell walls. The endotoxins eventually cause vasodilation, hypoxia and subsequent cardiovascular shock.

Aerobic Gram-Negative Bacilli
-Pseudomonas-an opportunistic pathogen
-Brucella-zoonotic pathogens
-Bordetella pertussis and Legionella-mainly human pathogens
-Alcaligenes-opportunistic pathogens

Q: What virulence factor is common to all Gram negative bacilli?
a. Capsule
b. Exotoxin
c. Endotoxin
A: Endotoxin

Q: What is the cardinal manifestation of human brucellosis?
a. Vomiting and diarrhea
b. A fluctuating pattern of fever
c. A cough that lasts for months
A: A fluctuating pattern of fever

Pseudomonas aeruginosa


Pseudomonas are a large group of free-living bacteria. They live in soil and sea/fresh water (they use H2O). They also colonize in plants and animals and are frequently found in homes (and flowers at hospitals!). They are small, gram-negative rods that have a single flagellum.

Pseudomonas aeruginosa is an intestinal resident in 10 % of normal people. It is resistant to soaps, dyes, quaternary ammonium disinfectants, drugs and drying (living and metabolizing inside or on). Pseudomonas aeruginosa is a frequent contaminant (they colonized inside) of ventilators, IV solutions, and anesthesia equipment.

Pseudomonas aeruginosa is a common cause of nosocomial infections in hosts with burns, neoplastic disease, and cystic fibrosis. Complications include pneumonia, UTIs, abscesses, otitis, corneal infections, endocarditis, meningitis, and bronchopneumonia.



Pseudomonas aeruginosa is a typical opportunist pathogen (lives in food). It is unlikely to infect a healthy person, thus it's infectiousness usually results from invasive medical procedures or weakened host defenses. Once in the tissues, P. aeruginosa expresses virulence factors including exotoxins, a phagocytosis-resistant slime layer, and various enzymes that degrade host tissues. It also causes endotoxic shock.

Pseudomonas aeruginosa has a grape-like odor, and is greenish-blue in color (pyocyanin). It glows under UV light. Areas infected with P. aeruginosa may appear green due to growth of this pathogen (in the nails). Also, you should not use your mascara too long because this bacteria may form inside the tube.

It is multi-drug resistant, but cephalosporins, aminoglycosides, carbenicillin, polymixin, quinolones, and monobactams can all work.

Of the above antibiotics, only fluoroquinolones can be taken orally. An example is Cipro. Antibiotics are used sparingly in hopes of avoiding development of resistant strains. Most people have IV antibiotics if you have Pseudomonas aeruginosa.

Pseudomonas aeruginosa are an opportunist pathogen, and the most common organism on the planet. They typically like to infect some one with burns, cuts, cystic fibrosis, or indwelling catheter. Sine they are multi-drug resistant it makes sensitivity testing imperative, however, vaccine are being tested for cystic fibrosis patients.

Other Gram-Negative Aerobic Rods

Burkholderia cepacia (don't need to know this one for class)

Burkholderia cepacia is a common isolate from moist environments that plays an important ecological role in controlling fungal disease on plants. It is active in biodegradation of a variety of toxic substances. It also has a potential for opportunistic infections in the respiratory tract, urinary tract, and the skin. Pneumonia caused by B. cepacia holds risks for cystic fibrosis patients, whose disease creates conditions that can favor the entrenchment of pathogens in the lungs.

Finding a successful treatment is a challenge because of its tendency to mutate rapidly and resist antimicrobic drugs. Co-infection with Pseudomonas may lead to severe respiratory compromise and death in 80% of patients.

-Cystic fibrosis patients suffer from a lung condition where mucus collects and creates a protective biofilm tenaciously colonized by pseudomonas.


Burkholderia pseudomallei (don't need to know this one for class)

Burkholderia pseudomallei resides in the soil and water of tropical climates. It causes melioidosis, which is prevalent in many areas of Southeast Asia and parts of Africa, India, and the Middle East.

It is generally acquired through a penetrating injury by a soiled object or inhalation from environmental reservoirs rather than from an infected person. Manifestations of wound infection are localized skin nodules along with symptoms of fever and muscle aches. Lung infection gives rise to bronchitis and pneumonia that is attended by cough and chest pain. Chronic infection may progress to septicemia, endotoxic shock, and abscessed in organs such as the liver and the brain. In persons with compromised immune systems, the infection can cause severe disseminated disease that is occasionally fatal.


Acinetobacter baumanii (don't need to know this one for class)

Acinetobacter baumanii is distributed throughout the world and has recently become a high-profile pathogen in nosocomial and community-acquired infections. It is an extremely resistant bacterium known to survive for months on inanimate objects such as faucets, toilets, bed cloths, doorknobs, sinks, respiratory equipment, and catheters.

It can cause severe infections in wounds, lungs, the urinary tract, burns, and blood. It is been one of the more problematic agents of wound infections seen in military personnel with traumatic injuries in Iraq and Afghanistan. Combat conditions make control and treatment more difficult and increase the risk for bloodstream infections. Another complication is the new occurrence of multidrug-resistant strains that are able to withstand the usual broad-spectrum drugs.

Most infections can be treated with some combination of carbapenems, colistin, polymyxin B, and ampicillin.

Stenotrophomonas maltophilia (don't need to know this one for class)

Stenotrophomonas maltophilia has unique genetic sequences and the presence of unusual fatty acids that prompted its reclassification into this new genus and species. The natural habitat of this bacterium is fresh water and soil associated with plant roots. It is also a member of fecal flora in humans and may be isolated from domestic animals.

It appears in the clinical setting as a contaminant of disinfectants, dialysis equipment, respiratory equipment, water dispensers, and catheters.

It has an ability to lay down biofilms, which protect it against drugs and disinfectants. It is a prominent clinical isolate as well, and is most often found in respiratory soft tissue, blood, spinal fluid, and ophthalmic specimens. Higher rates of infection occur in cancer patients and people with tracheostomies and other indwelling invasive devices.

Although the species is one of the most drug-resistant of bacteria, therapy with a combination of cephalosporins, tetracyclines, fluoroquinolones, or new penicillins are usually effective.

Brucella/Brucellosis


Bruccellosis in Cattle: this disease is also known as "contagious abortion"or "Bangs disease", it is caused by infection by the bacteria Brucella Abortus. This disease causes premature calving or abortion of cattle. Milk produced by the cow my also carry the organism. There is NO treatment!!!

Brucellosis- which causes undulant fever that can last for weeks or months. They are tiny gram negative, aerobic, nonenteric(not usually in stool sample), zoonotic pathogens that may cause fluctuating pattern of fever, chills, sweating aches and fatigue.
Brucella are tiny gram-negative coccobacilli. There are two species...brucella abortus which is common in cattle, and Brucella suis, which is found in pigs. It is associated mostly with those who work in slaughterhouses, work with livestock, or are in the veterinary business.

Infection takes place through contact with the animal's blood, urine, placenta, or the consumption of raw milk or cheese. Brucellosis, malta fever, undulant fever and Bang disease (a zoonosis transmitted to humans from infected animals), fluctuating pattern of fever for weeks to a year. Treatment for brucella is a combination of tetracycline and rifampin or streptomycin. Vaccines for animals are available, but those developed for humans are ineffective or unsafe. Because of this, Brucella could potentially be used as a germ warfare agent.

Q: Brucellosis is spread to humans by human contact with all but which of the following?
a. Blood
b. Urine
c. Cerebrospinal fluid
A: Cerebrospinal fluid

Q: What is the cardinal manifestation of human brucellosis?
a. Vomiting and diarrhea
b.

A fluctuating pattern of fever

Bordetella pertussis


Bordetella Pertussis, a coccobacillus human pathogen, is nonenteric and encapsulated that can be transmitted through direct contact with droplets or inhalation of aerosols.
Pertussis: infection by bordetella pertussis, a highly communicable disease that causes acute respiratory syndrome. Can be life-threatening in infants, but vaccines on the recommended schedule can prevent it. ALSO CALLED WHOOPING COUGH

A minute, encapsulated coccobacillus that causes pertussis or whooping cough, a communicable childhood affliction. It causes acute respiratory syndrome and often severe and life-threatening complications occur in infants under the age of one. There is an upsurge in infections due to worry over the vaccine, due to a possible correlation with autism. The old, whole cell vaccine contained thimerosal, which contains mercury. The new acellular vaccine dose not contain mercury. There is also a booster for teens called Boostrix.

Transmission of bordetella pertussis is by direct contact or inhalation of aerosols. There are 30-50 million cases per year and about 300,000 deaths per year (World Health Organization data). Most deaths occur in children under one year of age. Ninety percent of all cases occur in developing countries. Immunity and vaccine only last a few years.

Bordetella pertussis virulence factors: receptors that recognize and bind to ciliated respiratory epithelial cells. Then toxins destroy and dislodge ciliated cells leading to loss of ciliary mechanism which causes build-up of mucus and blockage of the airways.

The initial phase of pertussis is the catarral stage, marked by nasal drainage, sneezing and cough. As the condition worsens, it enters into the paroxysmal stage where the patient, the child ,experiences recurrent, persistent coughing. The coughs are fits of several abrupt, hacking coughs, followed by a deep inhalation that produces the "whoop" noise.


The vaccine-DTap acellular vaccine contains toxoid and other Ags. This vaccine is given at 2 months, 4 months, 6 months, 12 months and then a booster is given prior to admission to elementary school usually around age 5. Due to the change in disease epidemiology, it is clear that booster doses are necessary--however, older children and adults are not good candidates for the acellular pertussis (aP) vaccine. In response, the CDC has added a new vaccine--Boostrix--recommended just for older children and adolescents age 10-18, that is a combination of diphtheria, tetanus, and pertussis antigen.


These are sounds that no parent wants to hear coming from their child.

www.medscape.com/viewarticle/574587: (guidlines for Tdap vaccines during pregnancy)

Tdap may be substituted for Td during pregnancy if immunization cannot be delayed during pregnancy or when the risk of pertussis is increased.

In such cases, women should be informed of lack of data on safety, immunogenicity, and pregnancy outcomes for pregnant women who received Tdap.

If Tdap is administered during pregnancy, the second or third trimester is preferred unless protection is urgently needed.





















Legionella pneumophila/Legionella/Legionellosis

Legionella is a human pathogen that can cause a type of pneumonia and hospital occurance is eight thousand to eighteen thousand people in the U.S. per year.
Legionella pneumophila is widely distributed in water (tap, cooling towers, spas, ponds, and other fresh waters), and lives in close association with amoebas. In 1976, an epidemic of pneumonia afflicted 200 American Legion members attending a convention in Philadelphia and killed 29. It was traced to contaminated air-conditioning vents in the Legionnaires' hotel.
It is very difficult to grow in a lab, and went unfounded for years until the epidemic on 1976. They test for it now by growing on a selective charcoal-yeast agar which makes white feathery white colonies.

The bacteria can be released during aerosol formation and can often be carried for long distances. Cases have been traced to supermarket vegetable sprayers and the fallout from Mt. St. Helen's volcano.

Legionella pneumophila and Pontiac fever (the two clinical forms for the disease) are most prevalent in males over 50 years of age. It is a common nosocomial disease in elderly patients. Symptoms that commonly occur are fever, cough, diarrhea, and abdominal pain. However, Pontiac fever does not lead to pneumonia and rarely causes death. The pneumonia fatality rate is 3 to 30%. This infection is commonly treated with azithromycin (Zithromax).

Q: How are Legionella species transmitted from their natural habitats to humans?
a. Aerosols
b. Contaminated drinking water
c. By vectors
A: Aerosols

Enterobacteriaceae Family

Enterics are a large family of gram-negative bacteria. Many members inhabit the soil, water, and decaying matter. They are a common occupant of the large bowel of humans and animals. All members are small and have non-sporing rods. They are facultative anaerobes and grow the best in air. They cause diarrhea through enterotoxins and are divided into coliforms (lactose fermenters) and non-coliforms (non-lactose fermenters).

Antigens and virulence factors of Enterobacteriaceae are H (flagellar antigens), K (capsule and/or fimbrial antigens), O (somatic or cell wall antigens), endotoxins, and exotoxins.

Escherichia coli: The most prevalent enteric bacillus

It is the most common aerobic and non-fastidious bacteria in the gut (intestines). Most strains of E. coli are harmless or even beneficial as normal intestinal flora, however some strains such as O157:H7 (see more below) have picked up a phage which encodes a toxin. Others have toxing genes in their genomes that are not derived directly from a phage. It is the number one most common nosocomial infection in hospitals, 50-80% of UTI due to E. coli coming in contact usually by the patient infected. It can cause neonatal meningitis, septicemia, and wound infection.
There are 150 strains; some of them are not infectious and many of them are. The strain developed in cattle intestine and began causing infection in 1982. This strain acquired a virulence plasmid and it made the shigella toxin. It is associated with fast food restaurants and meat recalls. This is why there are now warning labels on meat products.
Antigen and virulence factors of E. coli: O157:H7
H- flagellar Ag
K- capsule or fimbrial Ag
O- somatic or cell wall ag all have
Endotoxin- like lipid A
Enterotoxin- what bacteria puts out

Enterotoxigenic E. coli causes severe diarrhea due to heat-labile toxin (LT) and heat-stable toxin (ST) which stimulate secretion and fluid loss. In this way, it mimics the pathogenesis of cholera. E. coli also has fimbrae.

E. coli causes inflammatory disease of the large intestine, similar to Shigella dysentery. Enteropathogenic strains of E. coli are linked to a wasting from infantile diarrhea. The newest strain, 0157:H7 (aka: EHEC-enterohemorrhagic E. coli), in about 10% of cases, can cause a much more severe form of the disease appears and is known as Hemolytic Uremic Syndrome (HUS). This condition leads to hemolysis and kidney damage, and eventually kidney failure. Antibiotic treatments are often not effective.

Pathogenic strains are frequent agents of infantile diarrhea which is the greatest cause of mortality among babies. E.coli causes 70% of traveler's diarrhea. E.coli causes 50-80% of UTIs. E.coli is an indicator of fecal contamination in water.

Oral antimicrobics may be effective in the early phases of infection. OTC medications that slow gut motility may offer symptom relief, but may also cause the body to retain the pathogen longer. Pepto-Bismol, a bismuth salicylate mixture, counteracts the enteroxin and may also have an antimicrobial effect.


E. coli 0157:H7
Didn't appear until 1982 and since then it has been designated by its antigen profile: O157:H7 (This stands for somatic (O) type 157 and flagellar (H) type 7).


E. coli has a reservoir in the intestine of cattle. Therefore, it can enter the food chain in contaminated beef, water and vegetables. Undercooked or raw hamburger has been implicated in many of the documented outbreaks. This is probably because commercially supplied ground beef is a mixture of meats from potentially hundreds of sources. This means a single animal carrier can potentially become a common source in thousands of pounds of beef. E.coli outbreaks have also implicated alfalfa sprouts, unpasteurized juices, dry-cured salami, lettuce, game meat, cheese curds, and spinach. Infection from toxin-producing strains of E. coli causes severe cramping and diarrhea which is initially watery but becomes grossly bloody. The infectious dose is a mere 100 cells--even a small bit of uncooked meat could contain this amount. Approximately 2000-4000 cases per year are reported to the CDC.

Because one of its effects can lead to intestinal hemorrhage, it is also considered a type of enterohemorrhagic pathogen. These bacteria owe much of their virulence to a cell wall receptor that can fuse with the host cell membrane. This connection creates a direct port into which the bacteria secrete toxins and other proteins directly into the host cell. This type of E-coli has also acquired the gene for shigatoxin from Shigella. The toxin enters the host cell, binds to ribosomes, and disrupts protein synthesis, leading to death and shedding of intestinal cells.

This strain of e-coli causes a range of symptoms and signs, from gastroenteritis and dysentery to fever and acute abdominal pain, similar to shigellosis. In about 10% of cases, a much more severe form of disease called hemolytic uremic syndrome (HUS) appears. This condition is caused by the toxic effect of the bacteria on the blood and kidney, leading to hemolysis and kidney damage and failure.

E. Coli and the Coliform Count

because if its prominence as a normal intestinal bacterium in most humans, E coli is currently on of the indicator of the bacterial to monitor fecal contamination in water, food, and dairy products.

coliforms such as E coli are used because they are present in larger numbers, can survive in the environment, and are easier and faster to detect than true pathogens.

if a certain number of coliforms are detected in a sample. the water is judged unsafe to drink
When they are testing for E-coli, they specifically test for O157:H7. The primary way to rapidly identify it is with selective media in the lab. Testing is performed randomly, and is not required by slaughterhouses and meat suppliers, but it has been successful in identifying pathogens in meats and the recall of millions of pounds of hamburger.
Other Coliforms (Lactose + Enterics)


Klebsiella pneumonia: Often a normal inhabitant of the respiratory tract, Klebsiella has a large capsule which promotes infection by preventing phagocytosis. Klebsiella pneumonia causes pneumonia, meningitis, bacteremia, wound infections and UTIs.




Serratia marcescens-produces a red pigment when grown at room temp. Serratia causes pneumonia, burn and wound infections, septicemia, and meningitis. Interestingly enough this bacteria was once thought so benign that they used it to trace the movements of air currents in hospitals and over cities and even to demonstrate transient bacteremia after dental extraction. Unfortunately, it is fully capable of invading compromised host.

The 2004 flu vaccine was recalled due to contamination with Serratia.




Noncoliforms (Lactose-negative enterics)
Proteus-An opportunist that swarms on surface of moist agar in a cocentric pattern. Can cause UTIs, wound infections, pneumonia, septicemia, and infant diarrhea. Proteus UTIs stimulate renal stones and damage.

Salmonella-
Salmonella is a true enteric pathogen. Salmonella is motile, it ferments glucose and is resistant to chemicals,spore forming, bile and dyes. Salmonella are flagellated and grow readily on most lab media. They also are able to survive outside the host in environments such as fresh water and freezing temps. Along with Shigella, salmonellae have well-developed virulence factors and are not part of the normal flora in humans. The illnesses they cause slow GI involvement and cause diarrhea, but often affect other systems as well.

The most serious of the salmonella genus is S. thyphi (Thyphoid Fever). It enters the digestive system through water or food contaminated by feces, but can occasionally be spread through close personal contact. The ingested bacilli that adhere to the small intestine and cause invasive diarrhea that leads to septicemia. Various Salmonella species can cause gastroenteritis in 2-5 days. ( I don't recommend feeding the seals at the Seaside aquarium in Oregon.)

Salmonelloses other than typhoid fever are called enterc febers, salmonella food poisoning, and gastroenteritis. These diseases are usually less severe. They are more prevalent than typhoid fever, and unlike typoid, all strains are zoonotic in origin. Salmonella are normal intestinal flora in cattle, poultry, rodents and reptiles. Animal products can be easily contaminated during slaughter, collection or processing. Eggs are another problem, since the bacteria may actually enter the egg while the shell is being formed.

MARY MALLON (aka Typhoid Mary)
At one time was dubbed "the most dangerous woman in America" Over the course of her career as a cook, she infected 47 people, three of whom died from the disease. Her fame is in part due to her vehement denial of her own role in causing the disease, together with her refusal to cease working as a cook. She was forcibly quarantined twice by public health authorities and died in quarantine. It was also possible she was born with the disease, as her mother had typhoid fever during her pregnancy.

Shigella-
Shigella is a genus of Gram-negative, non-spore forming rod-shaped bacteria closely related to Escherichia coli and Salmonella. The causative agent of human shigellosis, Shigella cause disease in primates, but not in other mammals. Shigella causes a common but often incapacitating dysentery known as shigellosis. Shigellosis produces H2S or urease, invades the villus of the large intestine. This enters the Peyer's patches, instigates inflammatory response and then endotoxins and exotoxins are released.

Shigellosis is acquired primarily by eating fecal-contaminated foods. It can also be transferred by human-to-human contact because it requires a small dose to be infected (100-200 cells).

Shigellosis is different from salmonellosis in that Shigella invades the villus cells of the large intestine, rather than the small intestine. In addition, it can possibly perforate the intestine or invade the blood. It is a very invasive infection that causes bloody diarrhea. S. dysenteria produces heat-labile exotoxin that has a number of effects, including injury to nerve cells and nerves, and damage to the intestine. The most common symptoms are diarrhea, fever, nausea, vomiting, stomach cramps, flatulence, and straining to have a bowel movement. The stool may contain blood, mucus, or pus.

Treatment is fluid replacement and ciprofloxacin (a fluoroquinolone) and sulfa-trimethoprim. No vaccine is yet available.

Yersinia Pestis-

Yersinia pestis is nonenteric. They are tiny gram-negative rods with unusual bipolar staining and capsules. The virulence factors are their capsule and envelope, proteins protect against phagocytosis and foster intracellular growth. The bacillus also produce coagulase which clogs the esophagus in fleas and obstructs blood vessels in humans. Other factors that contribute to pathogenicity are endotoxin and a highly potent Murine toxin. the word plague conjures up death and morbidity unlike any other infections disease. Although pandemics of plague have probably occured since antiquity, the first one that was reliability chronicled killed an estimated 100 million people in the sixth century. the last great pandemic occured in the late 1800's and was transmitted around the world, primarily by rat-infested ships. The disease was brought to the US through the port of san Franciscoaround 1906. Eventually, infected rats mingles with the native populations of rodents and gradually spread the populations throughout the West and Midwest. The cause of this dread disease is a tiny, harmless-looking gram-negative rod called Yersinal Pestis formerly pasteurella pastis, with unusual bipolar staining and capsules

The plague bacillus exists naturally in many animal hosts. In the US, humans develop the plague through direct contact with wild animals (sylvatic plague) or domestic or semidomestic animals (urban plague) or infected humans. This is found in 200 species of mammals (rodents) without causing disease. Flea vectors are where the bacteria replicates in the gut, coagulase which causes blood clotting that blocks the esophagus; flea becomes ravenous. No human-to-human transmission of the plague has been noted since 1924. Recently Y. pestis has gained attention as a possible biological warfare agent and the CDC has classified it as category A pathogen requiring preparation for a possible terrorist attack. Y. pestis may be afflicting al-qaeda in Algeria.

Pathology of the Plague



3-50 bacilli
The bubonic plague-bacillus multiplies in flea bites, enters the lymphatic system and is stopped at lymph nodes, the infection causes necrosis and swelling called bubo.
Septicemia-progression to massive bacterial growth; virulence factors cause intra-vascular coagulation subcutaneous hemorrhage and purpura (Black plague)
Pneumonia-infection localized to the lungs, highly contagious; fatal without treatment
Treatment: streptomycin, tetracycline, or chloramphenicol




Hemophilus



Tiny gram negative pleomorphic rods. Fastidious, sensitive to drying, temperature that are extreme, and disinfectants. None can grow on blood agar without special techniques, such as chocolate agar. Require hemin, NAD or NADP. Some species are normal colonists of upper respiratory tract or vagina ( H. aegyptius, H. parainfluenza, H ducreyl). Other are virulent species responsible for conjunctivitis, childhood meningitis, and chancroid. People thought it was the cause of the Flu but it really was not.

H. influenzae, is acute bacterial meningitis, epiglottitis, otitis media, pneumonia, and bronchitis(subunit vaccine Hub). H. aegyptius-conjunctivitis, which is pink eye. H. durcreyi-chancroid STD. H. parianfluenzae and H. aphrophilus-normal oral and nasopharngeal flora, infective endocarditis.

Hemophilus aegyptius (Koch-Weeks bacillus)
-Is an agent of communicable conjuctivitis (pinkeye).
-The subconjuctival hemorrhage that accompanies infection imparts a bright pink tinge to the sclera.
-Occurs primarily in children.
-It is distributed worldwide.
-It is spread through contaminated fingers and shared personal items as well as mechanically by gnats and flies.
-Is treated with antibiotic eye drops.


Flash cards for this chapter on www.flashcardexchange.com under Kevin Youngs micro chapter 20


Identifying Gram Negative Bacilli-

IMViC tests- Is used to identify enterics (such as: Klebsiella, Enterobacter, and Escherichia coli). An INViC test can tell the difference between these bacteria. IMViC stands for indole, methyl red, Voges- Proskauer and Citrate.

Indole test- The test organism is inoculated into tryptone broth (a source of tryptophan- an amino acid). An Indole positive bacteria will cleave to tryptophan and produce tryptophanase. When Kovac's reagent is added to a broth with indole in it the solution turns dark pink. It must be read by 48 hrs. of incubation. The acid pH of E. coli can limit its growth.


Methyl Red and Voges-Proskauer tests- The methyl red and Voges-Proskauer tests start with a single tube of broth which is inoculated. After 24-48 hours, the tube is split into two. Use one tube for the methyl red test and the other for the Voges-Proskauer test. The media for this test has glucose and peptone. All enterics digest glucose but they have different ending enzymes. These tests determine the ending enzymes for the bacteria being tested. If the pH drops (like when testing E.coli) and the pH indicator methyl red is added to the broth it becomes red.
Klebsiella and Enterobacter produce neutral products with the bacteria is not inhibited so it attacks the peptone found in the broth. This causes the pH to rise and the methyl red indicator to turn the broth yellow.
The reagents for the Voges-Proskauer test is the Barritt's A and Barritt's B reagents. If acetyl methyl carbinol is present in the broth it turns a pink color within 20-30 min. E. coli won't produce acetyl methyl carbinol. However, Enterobacter and Klebsiella will.


Citrate test- This tests determines if bacteria can grow utilizing citrate as its sole carbon and energy source by using Simmon's media. If the bacteria is citrate positive it will be blue, but if the bacteria is citrate negative the broth will be green. Enterobacter and Klebsiella are citrate positive and E. coli is negative.


Oxidase test- This tests a bacteria's ability to produce the enzyme cytochome c oxidase. Pseudomonas aeruginosa, Neisseria gonorrhoeae and Campylobacter jejuni are oxidase-positive. During the cellular respiration of these bacteria oxidation reduction reactions are done until it reaches the final electron acceptor (often oxygen).

Questions: Q&A Page~~Home Page~~Top of Page

1. A classic symptom of pertussis is
a. labored breathing
b. paroxysmal coughing
c. convulsions
d. headache

2. The bubo of bubonic plague is a/an
a. ulcer where the flea bite occurred
b. granuloma in the skin
c. enlarged lymph node
d. infected sebaceous gland

3. Which of the following represents a major difference between Salmonella and Shigella infections?
a. mode of transmission
b. likelihood of septicemia
c. the portal of entry
d. presence/absence of fever and diarrhea

4. Which gram negative disease can you be a carrier of and have no signs of the disease?
a. Shigella
b. Typhoid
c. Yersinia pestis
d. Serratia

5. This bacteria was the cause of the recall on the 2004 flu vaccine.
a. Serratia marcescens
b. Proteus
c. E. coli 0157:H7
d. Klebsiella pneumoniae

6. This opportunistic bacteria will swarm on the surface of moist agar in certain intervals and produce patterns of rings (wave-like patterns) due to their motility.
a. Serratia marcescens
b. Klebsiella pneumonae
c. Proteus
d. Shigella

7. This type of bacteria has acquired the gene for shiga toxin from Shigella. The toxin enters the host cell, binds to ribosomes, and disrupts protein synthesis, leading to death and shedding of intestinal cells.
a. E-coli O157:H7
b. Citrobacter
c. Serratia
d. Providencia

8. Noncoliform opportunists include all of the following except
a. Proteus
b. Morganella
c. Serratia
d. Providencia

9. Infection that imparts a bright pink tinge to the sclera is a result of which of the following?
a. Haemophilus aegyptius
b. Haemophilus chancroid
c. Pasteurella multocida
d. Typhoid fever

10. Which of the following is the bacteria that is the majority of nosocomial infections?
a. Salmonella
b. Klebsiella
c. Escherichia coli
d. Enterobacter

11. A unique characteristic of many isolates of Pseudomonas useful in identification is_____
a. fecal odor
b. fluorescent green pigment
c. drug resistance
d. motility

12. Complications of typhoid fever are________
a. neurological damage
b. intestinal perforation
c. liver abscesses
d. b and c

13. For the past several weeks, Josh has been suffering from chills, profuse sweating, and headaches. He works in a small-town veterinary clinic that specializes in treating farm animals. What species has he probably been infected with?

14. Jebediah recently traveled to Mexico. After drinking the tap water there, he became sick with diarrhea, fever, and vomiting. What species has he most likely been infected with?

15. Just in case you were tempted to do so … don’t eat foods contaminated by rodent feces! They may carry this pathogenic species, which is also associated with poorly cooked beef, unpasteurized fresh milk, homemade ice cream made with raw eggs, and Caesar salad. What is it?

16. Jack works as a janitor at the local hospital. His main duty is to clean the bathrooms, including disinfect the sinks and soap dishes and mop the floors. What contaminant may he come into contact with from the bathroom fixtures, the soap dishes, and the mop?

17. Almost all cases of this infection occur in developing countries, especially in babies under one year old. What infection is it?

18. Joe is a 60-year-old male who works as a produce manager at the local grocery store. As part of his job he regularly sprays down the fruits and vegetables in the produce section. Recently he’s been out sick with a rising fever, cough, diarrhea, and abdominal pain. What species may he have been infected with?

19. This opportunistic pathogen forms a mucus-y and stringy colony due to its thick capsule. It’s a normal inhabitant of respiratory tract, and a frequent cause of nosocomial pneumonia. What is it?

20. This species is not highly invasive, and is rather an opportunistic pathogen. That’s why it likes to prey on people having invasive medical procedures, and grows biofilms on ventilators, IVs, and anesthesia equipment. What is it?

21. Jeremiah’s favorite food is a big, juicy hamburger. He cooks himself one every day. Yesterday he forgot to wash his hands after handling the meat. He cooked his burger, ate it, then licked his fingers hungrily to enjoy the taste there, too. Today he’s been experiencing a high fever, watery diarrhea and severe cramps. What species has he likely been infected with?

22. This bacteria can enter through damaged skin or mucous membranes of the digestive tract, conjunctiva, and respiratory tract. It manifests itself in a fluctuating pattern of fever, giving the illness its common name, undulant fever. What species is it?

23. This species loves moist environments, such as sponges, washcloths, contact lenses, and mascara wands. What is it?

24. The likelihood of being infected by this species may be lessened by chlorinating drinking water and regularly cleaning swimming pools and other artificial aquatic habitats. What species is it?

25. Jackie has a urinary tract infection that has progressed to kidney stones. Her doctor sent a urine specimen to the lab, where a culture of it produced rings in a distinct concentric pattern. What species caused her UTI and kidney stones?

26. This species is used as an indicator of fecal contamination in water, food, and dairy products. The rationale is that if this species is present, then fecal pathogens like Salmonella, viruses, or even pathogenic protozoa may also be present. What species is it?

27. Which species doesn’t belong in this group: Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Proteus?

28. Joni is a six-year-old girl who has caught a case of conjunctivitis, which has caused redness in her sclera. Her doctor prescribed her with antibiotics drops to place in the infected area. What is the common name of her illness, and what species has she been infected with?

29. The vaccine for this gram-negative species is administered in a five-dose series with the DT vaccine. What species is it?

30. This disease causes 25,000 deaths/year worldwide. Humans are its exclusive hosts, and asymptomatic carriers are important in spreading the disease. Even six weeks after convalescence, the bacillus is still shed by half of recovered patients. A woman named Mary, who worked as a cook in New York in the early 1900s, was one such asymptomatic carrier. What is the disease, and what species causes it?

31. Along with cholera and yellow fever, what disease is one of the internationally quarantinable diseases?

32. On a selective medium called rainbow agar, this strain produces black colonies, while other strains of the same species do not. What species is it?

33. Jason is an alcoholic and was hospitalized recently for a liver transplant. The day after the surgery, the nurse noticed an intense red pigment discoloring some of Jason’s ventilator tube. What enteric species is he in danger of being infected by?

34. Which of the following is mis-matched:
a. Pseudomonas aeruginosa - contaminates IVs and ventilators
b. Bordetella pertussis - transmitted through inhaled droplets or aerosols
c. Legionella pneumophilia - transmitted through eating fecally contaminated foods
d. E. coli O157:H7 - most likely found in raw hamburger

35. Characteristics of this opportunistic pathogen species include a single polar flagellum, a grape-like odor, and a greenish-blue pigment that glows under UV light. What is it?

36. Both Janet and Jonathan had bladder catheters put in during a hospital visit. Which of them is more likely to develop a urinary tract infection, and what gram-negative species is most likely to cause it?

37. Which of the following ways can humans NOT be infected with the plague?
a. By handling animal skins that carry the plague bacillus
b. Through sexual contact with a person infected with the plague
c. Through bites from infected human fleas
d. By inhaling droplets transmitted by an infected person
e. By handling infected animals

38. Which of the following doesn't belong in this group: Serratia marcescens, Escherichia coli, Klebsiella pneumoniae, Salmonella, and Enterobacter?

39. This disease differs form salmonellosis in that it invades the large intestine rather than the small intestine. It causes an incapacitating dysentery marked by crippling abdominal cramps and frequent defecation of watery stool filled with mucus and blood. The small infectious dose of 100-200 cells is acquired primarily by eating fecally contaminated foods. What disease is it?

40. Which of the following pathogenic strains of Escherichia coli is mis-matched?
a. Enterotoxigen E. coli - has fimbriae to provide adhesion to the small intestine
b. Enteroinvasive E. coli - causes invasion and ulceration of the mucosa of the small intestine
c. Enteropathigenic E. coli - wasting form of infantile diarrhea
d. E. coli O157:H7 - causes hemorrhage that leads to kidney damage

41. Although the name of this bacteria means "blood-loving," it can't grow on blood agar alone, rather it needs chocolate agar and Fildes medium. What is it?

42. What species doesn't belong in this group: Bordetella pertussis, Escherichia coli, Haemophilus influenzae, Salmonella typhi, and Yersinia pestis?

43. Cultivation of this species requires special media such as charcoal agar, where feathery growth is indicative of its motility. What is the species?

44. When a plague epidemic occurs, which of the following strategies is NOT used to control infection?
a. Quarantining infected individuals
b. Making the vaccine available widespread to the human population where infection is centered
c. Trapping and poisoning rodents near urban and suburban communities
d. Dusting rodent burrows with insecticide to kill fleas

45. John recently visited Lava Hot Spring and spent some time soaking in the hot tubs. Afterwards he noticed his back had broken out in an itchy rash. What gram-negative species had he been infected by?

46. Which of the following is E. coli O157:H7 NOT likely to be found in?
a. raw hamburger
b. unpasteurized fruit juices
c. lettuce
d. custards
e. dry-cured salami

47. This species most commonly infects cattle, and when it's transmitted to humans, it's usually in people who work in slaughterhouses or veterinary clinics or who handle livestock. What is it?

48. Jimmy is two years old and has developed a hacking cough that produces a "whooping" sound when he inhales. What species has he been infected with?

49. A unique characteristic of many isolates of Pseudomonas useful in identification is:
a. fecal odor
b. fluorescent green pigment
c. drug resistance
d. motility

50. Human brucellosis is also known as
a. Bang disease
b. undulant fever
c. rabbit fever
d. Malta fever

51. Francisella tularensis has which portal of entry?
a. tick bite
b. intestinal
c. respiratory
d. all of the above


52. A classic symptom of pertussis is
a. labored breathing
b. paroxysmal coughing
c. convulsions
d. headache

53. The severe symptoms of pertussis are due to what effect?
a. irritation of the glottis by the microbes
b. pneumonia
c. the destruction of the respiratory epithelium
d. blocked airways
e. both c and d are involved

54. Eschericia coli displays which antigens?
a. capsular
b. somatic
c. flagellar
d. all of the above

55. Which of the following is not an opportunistic enteric bacterium?
a. E. coli
b. Klebsiella
c. Proteus
d. Shigella

56. Which of the following represents a major difference between Salmonella and Shigella infections?
a. mode of infection
b. likelihood of septicemia
c. the portal of entry
d. presence/ absence of fever and diarrhea

57. Complications of typhoid fever are
a. neurological damage
b. intestinal perforation
c. liver abscesses
d. b and c

58. Shigella is transmitted by
a. food
b. flies
c. feces
d. all of the above

59. Haemophilus influenza is ___ and requires special ____ for growth.
a. motile, temperature
b. encapsulated, minerals
c. intracellular, sample swabs
d. fastidious, blood factors

60. Which of the following is not associated with H. influenza infections? a. fever
b. flu
c. stiff neck
d. headache

61. Which of the following are primarily zoonoses?
a. tularemia
b. salmonellosis
c. shigellosis
d. brucellosis
e. pasteurellosis
f. bubonic plague

Key Definitions:


Endotoxin: structural component of Gram-negative outer membranes. Also called Lipid A (part of a lipopolysaccharide)

Enteric:Microorganisms that inhabit the intestines

Iatrogenic: in infection occuring as a result of a medical treatment

Catarral Stage: nasal drainage,congestion, sneezing and some coughing, cause from Bordetlla pertussis ( whooping cough).

Coliform-lactose fermenters

Non-Coliform:non lactose fermenters

Paroxysmal Stage: includes recurrent fits of several abbrupt hacking coughs, followed by a "whoop"

Pseudomonas: an opportunistic pathogen

Septicemia: the presence of pathogenic organisms in the blood-stream, leading to sepsis