Chapter 18 Objectives:

****Know the traits of the bacteria (including toxins and other virulence factors), and how

to distinguish them from other bacteria. Know the diseases they cause (symptoms too).****

Lecture recording

The Cocci of Medical Importance

Gram-positive Staphylococcus Staphylococcus aureus and it many diseases	Streptococcus pyogenes
Streptococcus Viridans Streptococci	Streptococcus pneumoniae
Gram-negative -Neisseria Neisseria gonorrhea, N. meningiditis

Streptococcus vs. Staphylococcus

Staphylococcus	Streptococcus
Gram positive	Gram positive
produces catalase	does not produce catalase
arranged in irregular clusters of cells	arranged in long chains of cells
31 species	25 species

The catalase test is also one of the main three tests used by microbiologists to identify species of bacteria. The presence of catalase enzyme in the test isolate is detected using hydrogen peroxide. If the bacteria possess catalase (i.e. are catalase positive), when a small amount of bacterial isolate is added to hydrogen peroxide, bubbles of oxygen are observed.
In microbiology, the catalase test is used to differentiate between bacterial species in the lab. The test is done by placing a drop of hydrogen peroxide on a microscopic slide. Using an applicator stick, a scientist touches the colony and then smears a sample into the hydrogen peroxide drop.

• If bubbles or froth forms, the organism is said to be catalase-positive. staphlococci are catalase-positive.
• If not, the organism is catalase-negative. streptococci are catalase-negative.

While the catalase test alone cannot identify a particular organism, combined with other tests, it can aid diagnosis. The presence of catalase in bacterial cells depends on both the growth condition and the medium used to grow the cells.

Staphylococcus aureus

• structural shape is large, round, opaque colonies of spherical cells, in irregular clusters
• prefers body temperature of 98.6 F or 37.0 C. Although they like warm temperatures, they will die if boiled.
• lives in most environments frequented by humans, and is readily isolated from fomites
• the 3rd most common nosocomial intections occure in the newborn nursery and surgical wards of the hospital
• colonization of some infants begins within hours after birth and continues throughout life
• carriage rate for normal healthy adults varies and tend to be harbored intermittently rather than chronically
• gram positive
• no flagella/lack spores
• may have capsules
• withstands high salt, extremes in PH & high temperatures common in skin/mucous
• facultative anaerobe (with or without oxygen)
• produces catalase (Hydrogen Peroxide will be broke down and bubbles produced)
• 20-60% of adults are carriers
• usually resides in anterior nares, skin, nasopharynx, perineum and intestine
• some strains of this bacterium are commonly referred to as MRSA (methicillin resistant Staphylococcus aureus) MRSA outbreaks have been reported in prision inmates, athletes, and schoolchildren. The infections are spread by coming in contact with skin lesions.
• 95% resistant to Penicillin and ampicillin
• Detection if an individual is suspected to have a staph infection is to collect blood cultures on the individual and incubate the culture for 3-5 days to see if the culture produces any CO2. Another method is to perform a nasal swab and culture the nasal swab on a agar plate.
• a local stpahylococcal infection often presents as an inflamed fibrous lesion enclosing a core of pus called an abscess.

As long as there is people there will always be infections, but there are ways to help prevent infections that everyone can take.

• Good hygiene is the number one way to prevent the spread of infections.
• Proper cleansing of surgical incisions and burns.
• Controlling the risk of outbreaks with people who are at greatier risk for infection. (people who have had a recent surgery, young children and babies.)
• Proper disposal of possible infected dressings, linens.

• Often found in noses due to their salty, warm, and dark atmosphere which is desirable for them.
• inflammation of the hair follicle (folliculitis) or glands (hidradenitis) is the most common superficial, mild infection
• if not taken care of the simple infections can lead to a furuncle (boil) which is when the inflammation of a single hair follicle or sebaceous gland progresses into a large, red, and extremely tender abscess or pustule.
• furuncles usually occur in clusters on parts of the body such as the buttocks, axillae, and the back of the neck, where skin rubs against other skin or clothing.
• a carbuncle is a larger ( sometimes as big as a baseball ) and deeper lesion created by aggression and interconnection of a cluster of furuncles.
• carbuncles are usually found in areas of thick, tough skin such as the back of the neck, these are extremely painful and can be fatal in the elderly when they give rise to systemic disease.
• impetigo is a bullous staphylococcal skin infection not confined to follicles and skin glands, characterized by bubble like epidermal swellings that can break and peel away like a localized form of scalded skin syndrome.

FURUNCLE CARUNCLE




Major Virulence Factors

Enzymes:

Coagulase	coagulates blood plasma *diagnostic tool* (this is a way to differentiate between different staph!!)
Hyaluronidase	digests connective tissue of the host
Staphylokinase	digests blood clots
Lipase	digests oils (allowing colonization of the skin)
Penicillinase	inactivates penicillin (resistance)
DNase	breakdown of DNA

Toxins:

Hemolysins (alpha, beta, delta, and gamma)	lyse red blood cells
Leukocidin	lyses neutrophils/macrophages
Enterotoxins (Intestinal) (A and B)	induces nausea, vomiting, and diarrhea
Exfoliative toxins	cause desquamation of the skin (separation of dermis and epidermis, causes Scalded Skin Syndrome)
Toxic Shock Syndrome toxin	induces fever, vomiting, rash, and organ damage

Diseases:

Furuncle/ Boil- is a skin disease caused by an infection of hair follicles.

Carbuncle- (Think: A CAR is bigger than an animal with FUR) A carbuncle is bigger than a Furuncle, it is contagious and may spread to other parts of the body, or other people. It is made up of many boils.

Impetigo-is a superficial bacterial skin infection. It is most commonly found in children ages 2-6.

Systemic-an infection within a body system.

Osteomyelitis-is an infection of the bone or bone marrow.

Scalded Skin Syndrome-also known as Ritter's disease. It is a dermatological condition. This is the condition where the skin looks like it has been scalded.

Streptococcus

-Gram positive
-spherical/ovoid cocci arranged in long chains.
-does NOT form catalase
-no flagella
-no spores
-has capsules/slime layers
-sensitive to heat, pH, antibiotics
-easy to treat
-25 species
Diagnosis of suspected streptococcal infection is usually made from material of the anterior nasal or nasopharyngeal areas of the throat, or from pus, sputum, spinal fluid, discharges, exudates, urine, blood or milk. As streptococci tend to be fastidious organisms, a rich medium such as Blood Agar is inoculated with the specimen in order to obtain isolated colonies. If the specimen is taken from a site containing a wide variety of indigenous or contaminating organisms (e.g., the rectal area or wounds), media with one or more selective agents are streaked. After incubation, the plates are examined for typical streptococcal colonies which tend to be white, glistening and relatively small.


S. pyogenes

-Group A
-most dangerous group
-humans only reservoir
-Beta (complete) hemolysis
-no vaccines available

Diseases
-Streptococcal pharyngitis (strep throat): Redness, tenderness, and edema in throat; multiplying organisms in the tonsils or pharyngeal mucous membranes, includes fever and body aches, can often feel like an aweful flu. Can lead to scarlet/rheumatic fever if gone untreated.
-Tonsillitis: Inflammation of the tonsils.
-Impetigo: Bubble-like epidermal swellings that can cause yellow crusty sores and possibly separate the epidermis from the dermis.
-Scarlet fever: High fever along with red rash on face, trunk, inner arms/legs, and tongue.
-Erysipelas: Inflammatory disease causing red skin. Like impetigo, but deeper.
-Rheumatic fever: Inflammatory condition of joints and heart.
-Glomerulonephritis: Inflammatory autoimmune condition (kidney glomerulus and tubular epithelia).
-Necrotizing fasclitis: Similar to impetigo. Introduced into small cuts and grows rapidly, damaging tissue and flesh.

-Strep Throat is detected by taking two swabs, one for the right tonsil, and one for the left tonsil, and then swabing the tonsils really good. There is a rapid strep test which dilutes the mucus that is collected on the swab and is run through a test strip. In most cases whether the rapid strep test comes back positive or negative, Doctors will order a back up strep in which the second swab is taken and inoculates a agar plate and allowed to grow for 34 hours to see if colonies of strep grow on the agar.


Streptococcal Hemolysis: Streptococcus pyogenes shows beta hemolysis, while most other strep show alpha (partial) or gamma (none) hemolysis. A group of Streptococcus called the "viridans" streptococci are named after the fact that alpha hemolysis turns the blood agar a greenish color ("viridans" means green).

In this image you can see complete lysis of red blood cells around the Beta symbol (drawn with Streptococcus pyogenes). The alpha symbol appears greenish due to partial red blood cell destruction. The gamma symbol (looks kind of like a "y") shows no hemolysis--the bacteria are just growing on the agar.

S. agalactiae (Group B)
- pregnant women are screened for this prior to the birth of her child
- beta (complete) hemolysis
- can cause meningitis for newborn baby
- mastitis can occur also
- resides in human vagina, pharynx & large intestine
- no vaccine available


S. pneumonia
- cause 60-70 % of all bacterial pneumonias
- fastidious requires blood or chocolate agar
- lack catalase and peroxidases
- dipplococcus grows in groups of two
- treated with penicillin
- has to form a capsule through a virus
to make you sick.
- alpha (partial) hemolysis

Bacterial pneumonia (main cause)
Otitis Media (middle ear infection)
Meningitis (common cause)
Sinusitis

Streptococci viridans
Gram-positive and alpha hemolytic bacteria that grows in pairs and chains. Most of the species are a greenish color on a blood agar. They are mostly found on the teeth. When any type of sugar is fed to them, they produce acid which eats away at your enamel causing cavities. Streptococcus viridans can get into the bloodstream through the oral cavity, urinary tract, and the GI tract. This bacteria can attach to the heart valves and cause ulcerations on the inner walls of the an artery. These risks are from an implied association between dental treatments and endocarditis. This occurs as Streptococci viridans are commonly attached to tooth surfaces and can facilitated to enter the blood system during dental or surgical procedures.

UPDATE FROM AMERICAN HEART ASSOCIATION
For decades, the American Heart Association (AHA) recommended that patients with certain heart conditions take antibiotics shortly before dental treatment. This was done with the belief that antibiotics would prevent infective endocarditis (IE), previously referred to as bacterial endocarditis. IE is an infection of the heart’s inner lining or valves, which results when bacteria enter the bloodstream and travel to the heart. Bacteria normally are found in various sites of the body including on the skin and in the mouth.
The AHA’s latest guidelines were published in its scientific journal, Circulation, in April 2007 and there is good news: the AHA recommends that most of these patients no longer need short-term antibiotics as a preventive measure before their dental treatment.
The American Dental Association participated in the development of the new guidelines and has approved those portions relevant to dentistry. The Infectious Diseases Society of America and the Pediatric Infectious Diseases Society endorsed the guidelines.
The guidelines are based on a growing body of scientific evidence that shows the risks of taking preventive antibiotics outweigh the benefits for most patients. The risks include adverse reactions to antibiotics that range from mild to potentially severe cases. Inappropriate use of antibiotics can also lead to the development of drug-resistant bacteria.
Scientists also found no compelling evidence that taking antibiotics prior to a dental procedure prevents IE in patients who are at risk of developing a heart infection. Their hearts already are often exposed to bacteria from the mouth, which can enter their bloodstream during basic daily activities such as brushing or flossing. The new guidelines are based on a comprehensive review of published studies that suggests IE is more likely to occur as a result of these everyday activities than from a dental procedure.


S. Mutants
Diseases: - produce slime layers that adhere to teeth, they are the basis for dental plaque which becomes niche for various organisms which corrode the tooth by acidic and enzymatic action.

- Can damage heart valves
Neisseria:
The Family Neisseriaceae consists of gram-negative organisms, usually appearing as cocci. Cells of the genus Neisseria tend to be arranged in pairs with each cell flattened where it is in contact with its mate, hence a coffee-bean shape is generally seen and is highly diagnostic in clinical samples. The principal habitats of neisseriae associated with humans are the mucous membranes. Two species are pathogenic: N. meningitidis and N. gonorrhoea, each named after its disease.



N. meninitidis
-Gram-negative
-must enter the bloodstream and then the meninges.
-Sensitive to Penicillin.
-3-30% of the population carries it in the nasopharynx mortality is 15%



Neisseria meningitidis is a causative agent of meningitis, and is responsible for considerable morbidity and mortality throughout the world. Most disease-causing N. meningitidis strains belong to serogroups A, B and C. Serogroup A strains are responsible for epidemic disease in developing countries, and serogroup B and C strains are responsible for outbreaks of meningitis in the developed world.



N.gonorrhoea
- no flagella
- have fimbrae & pili
- not spore forming
- produce catalase & cytochrome oxidase
- do not survive long outside of the host
- strictly a human infection
- infection is asymptomatic in 10% of males and 50% of females.

Neisseria gonorrhoea possesses a typical Gram-negative outer membrane composed of proteins, phospholipids, and lipopolysaccharide (LPS). N. gonorrhoea is a relatively fragile organism, susceptible to temperature changes, drying, UV light, and other environmental conditions. Strains of N. gonorrhoea are variable in their cultural requirements so that media containing hemoglobin, NAD, yeast extract and other supplements are needed for isolation and growth of the organism. Cultures are grown at 35-36 degrees in an atmosphere of 3-10% added CO2.

Gram Staining:
*A note about Gram Staining:
The process is not related to grams when used as a term of weight. Instead, it was named after Danish scientist Hans Christian Gram. The process is as follows (rinse between each step with distilled water)

1. Place bacteria on slide. (May need to be heated to facilitate sticking)

2. Add crystal violet, which will make both specimens appear purple.
3. Add iodine. Both specimens still remain purple

4. Rinse with alcohol or acetone. At this time, the gram-positive sample will remain purple, but the gram-negative sample will become colorless.

5. Add safranin, which will cause the gram-positive sample to remain purple, but the gram-negative sample to turn red.






Gram Positive
- Staphylococcus
- Staphylococcus Aureus and its many diseases
- Streptococcus
- Streptococcus pyogenes , S. pneumoniae, viridans Streptococci

Gram Negative
- Neisseria
- Gonorrhea
- Meningitis




Here are several diseases caused by bacteria and viruses:
Bacteria: Pneumonia, Tetanus, Leprosy, Whooping Cough
Virus: Polio Myelitis, Aids, Influenza, Dengue Fever

Follow this link for more info:
* Diseases caused by bacteria & viruses *

Ecoli Bacteria Avian Flu Virus

Necrotizing Fasciitis
- Here are a few facts about this disease
- A complication of Strepticoccus Pyogenes
- Commonly known as the "flesh-eating disease"
- It is introduced by a cut or abrasion on the skin
- These strains of group A streptoccoci release toxins and enzymes which increase their invasiveness and virulence
- Invades the dermal and epidermal tissues
- As the flesh dies it sloughs off and allows more area for bacteria to invade
- Can lead to death, amputation or disfigurement
- Luckily it is not usually resistant to antibiotics




For more info on necrotizing fasciitis go to: http://www.nnff.org/nnff_factsheet.htm

1. Which of the following are pyogenic cocci?
a. Streptococcus
b. Staphylococcus
c. Neisseria
d. all of these

2. The coagulase test is used to differentiate Staphylococcus aureus from
a. other staphylococci
b. streptococci
c. micrococci
d. enterococci

3. The most severe streptococcal diseases are caused by
a. group B streptococci
b. group A streptococci
c. pneumococci
d. enterococci

4. Rheumatic fever damages the _______, and glomerulonephritis damages the ___________.
a. skin, heart
b. joints, bone marrow
c. heart valves, kidney
d. brain, kidney

5. The term facultative anaerobe describes a bacteria which will survive:
a. Without oxygen
b. Without enrichment media
c. Without blood
d. Phagocytosis

6. In addition to causing pneumonia, S. pnemoniae can frequently cause what other problem?
a. Carbuncles
b. Impetigo
c. Otitis Media
d. Inner ear infections

7. Viridans streptococci commonly cause
a.pneumonia
b.meningitis
c.sub-acute endocarditis
d.otitis media


8.________ hemolysis is the partial lysis of red blood cells due to bacterial hemolysins
a. Gamma
b. Alpha
c. Beta
d. Delta

9. Which infectious agent of those covered in the chapter would most likely be acquired from a contaminated doorknob?
a. Staphylococcus aureus
b. Streptococcus pyogenes

c.

Neisseria meningitidis

d

. Streptococcus pneumoniae

10. What statement is incorrect about Staphylococcus Aureus
a. structural shape is large and round
b. gram negative
c. no flagella
d. commonly known as MRSA

11. Which of these are an exotoxin of S. aureus?
a. blood cell toxins
b. intestinal toxins
c. exfoliative toxin
d. toxic shock syndrome toxin
e. All of the above

12. If you Gram-stained the bacteria that live in the human intestine, you would expect to find mostly
a. gram-positive cocci
b. gram-negative rods
c. gram-positive, endospore-forming rods
d. gram-negative nitrogen fixing bacteria
e. all of the above

13. Pathogenic bacteria can be...
a. Motile
b. Rods
c. Cocci
d. Anaerobic
e. all of the above

14. Rheumatic fever is
a. an active Streptococcal infection in the heart
b. an autoimmune response that can appear after "strep throat"
c. a flesh-eating disease that begins as impetigo
d. a disease caused by streptococcal toxins spreading through the body
e. pharyngitis in the tonsils and mucus membranes associated with high fever

15. A furuncle can be
a. something that attaches to the nasopharynx membranes.
b. an infection that has no symptoms
c. small cocci shaped bacteria that attacks the heart valves
d. when an infected hair follicle progresses into a large, red, pustule.

16. Name two of the most common drug-resistant Streptococcus?

17. Who in the 1930's developed the classification system used to identify Streptococcus?


Pick the correct bacteria that goes with each characteristic. Answer may be one or more. Choose from:
Staphylococcus aureus Streptococcus pyogenes Streptococcus pneumoniae Streptococcus agalactiae
Viradans Streptococci Neisseria gonorrhea Neisseria meningiditis

- Gram-positive?
- Sensitive to heat, pH, antibiotics?
- Does not survive more than 1-2 hours on fomites (i.e. relatively fragile)?
- Causes erysipelas?
- Produces slime layers on teeth?
- Causes impetigo?
- Vaccine available?
- Readily isolated from fomites?
- Carried mainly in the anterior nares?
- Inhabits the throat, nasopharynx, and occasionally skin?
- Infectious dose is 100-1,000 (i.e. very easy to get infected)?
- Most numerous and widespread resident of the oral cavity?
- Can be transferred to an infant during delivery?
- Usually enters during dental or surgical procedures?
- Inhabits the vagina, pharynx, and large intestine?
- Causes sequelae such as rheumatic fever?
- Is a Group B strep?
- Inhabits the oral cavity and also found in nasopharynx, genitals, and skin?
- Inhabits the intestine?
- Causes pharyngitis (a.k.a. strep throat)?
- Produces hyaluronidase as a virulence factor to break up the cement between cells?
- Produces DNase as a virulence factor to break apart DNA?
- Has pili as a virulence factor?
- Causes bacteremia?
- 20-60% of adults are carriers?
- Causes necrotizing fasciitis?
- Produces IgA protease as a virulence factor?
- Causes 60-70% of all bacterial pneumonias?
- Produces streptokinase as a virulence factor to break down blood clots?
- Causes pneumonia?
- Produces lipases as a virulence factor to break down fats?
- Causes tooth abscesses?
- Grows as a fastidious culture which requires 5-10% CO2 and will die in O2?
- Causes skin abscesses?
- 3-30% of population carries it in the nasopharynx?
- Causes otitis media?
- Has to be breathed in?
- Causes pyoderma?
- Treated with penicillin?
- Causes toxic shock syndrome?
- Inhabits the throat, nasopharynx, and occasionally skin?
- Increasingly resistant to penicillin, treated with cephalosporin and tetracycline?
- Has 12 strains, of which A, B, and C cause most cases?
- 5-50% of people carry is as normal flora in the pharynx?
- Withstands high salt, extremes in pH, and high temperatures?
- Causes meningitis?
- Causes gonorrhea?
- Can cause sterility in males & females and tubal pregnancies in females?
- Is alpha-hemolytic?
- Can cause anal and pharyngeal infections?
- Produces coagulase as a virulence factor?
- Causes abdominal infections?
- Inhabits the anterior nares, skin, nasopharynx, and intestine?
- Their bacteria get into the cranial cavity, then spreads?
- Produces C-carbohydrates and M-protein as virulence factors?
- Causes folliculitis?
- Inhabits the nasopharynx?
- Causes furuncles and carbuncles?
- Facultative anaerobe?
- Causes food intoxication?
- Resistant to penicillin?
- Causes scalded skin syndrome?
- Inhabits the skin?
- Arranged in pairs or short chains in a diplococcus arrangement?
- Causes strep throat?
- Causes scarlet fever?
- Most serious infection is subacute endocarditis?
- Causes sequealae such as glomerulonephritis?
- Causes endocarditis in debilitated people?
- Is the most prevalent cause of neonatal pneumonia?
- Is beta-hemolytic?
- Is group A strep?
- Produces exfoliative toxins?
- Produces pyogenic toxins?
- Produces hemolysins as a virulence factor?
- Produces penicillinase as a virulence factor?
- Fimbraie is its chief virulence factor?



Comprehension Questions
1. How many people in the U.S. carry Staphylococcus aureus? MRSA?
2. Which forms a capsule, Staph or Strep?
3. Staph or Strep: facultative anaerobes?
4. Staph or Strep: sensitive to drying and heat?
5. Staph or Strep: forms catalase?
6. What allows Strep to survive in the presence of oxygen?
7. What do S. aereus colonies look like?
8. What do Strep colonies look like?
9. What is a diagnostic test for S. aureus, and how does the test work?
10. Which strains of Strep create a zone of beta-hemolysis on sheep blood agar?
11. What is the most serious Streptococcal pathogen of humans?
12. What are the major extracellular enzymes of S. pyogenes?
13. What skin infections does S. pyogenes cause?
14. What are the two most important long-term complications of Strep Group A infections (i.e. sequelae)?
15. What kind of streptococcal infection can lead to severe carditis, where extensive damage to the heart valves and muscle can occur?
16. What kind of streptococcal infection can lead to urine samples being extremely abnormal?
17. What are the symptoms of acute glomerulonephritis (AGN)?
18. What strep species can be transferred to an infant during delivery?
19. What group B strep species is commonly associated with cattle, and is also a resident in the human vagina, pharynx, and large intestine?
20. What is by far the most common beta-hemolytic isolate in human lesions?
21. Which groups of Streptococci are most frequently found in humans?
22. Which groups of Streptococci are most often associated with infections in other mammals and only infrequently found in humans?

Comprehension Answers
1. 95 million people in the U.S. carry S. aureus; 2.6% of those also carry MRSA (about 2.5 million)
2. Staph MAY have capsules; Strep can form capsules and slime layers.
3. Both
4. Strep is sensitive to drying and heat. Staph can withstand extremes in pH and high temperatures.
5. Staph forms catalase, which is an enzyme that breaks down hydrogen peroxide. Strep has a peroxidase system for inactivating hydrogen peroxide, which allows their survival in the presence of oxygen.
6. Its peroxidase system, which inactivates hydrogen peroxide.
7. S. aureus grows in large, round, opaque colonies.
8. Strep forms small, nonpigmented, glistening colonies.
9. S. aureus is the only Staph species to produce coagulase, thus a coagulase tesst is diagnostic for S. aureus. Coagulase is an enzyme that reacts with factors in plasma to initiate clot formation. In the coagulase test, a tube of plasma is inoculated with the bacterium. If it remains liquid, the test is negative. If the plasma develops a lump or becomes clotted, the test is positive.
10. A, B, C, G, and some D strains.
11. Streptococcus pyogenes
12. 1) Streptokinase, which breaks down blood clots, 2) Hyaluronidase, which breaks down the cement between cells, 3) Streptodornase (DNase), which liquefies purulent discharges by hydrolyzing DNA.
13. 1) Pyoderma (aka streptococcal impetigo): marked by burning, itching papules that break and form a highly contagious crust; 2) Eysipelas: an acute but invasive skin infection where the pathogen usually enters through a wound or incision on the face and spreads to the dermis. Produces slightly elevated, red, hot, and vesicular skin. Can remain superficial or produce long-term systemic complications.
14. Rheumatic fever and acute glomerulonephritis (AGN).
15. Rheumatic fever. One of its major clinical features is carditis, where the heart tissues become inflamed and can cause damage to the heart valves and muscle.
16. Acute glomerulonephritis (AGN).
17. The first symptoms are nephritis (appearing as swelling in the hands and feet and also low urine output), increased blood pressure, and occasionally heart failure.
18. The group B streptococci (GBS), represented by the species S. agalactiae.
19. S. agalactiae
20. Group A streptococci
21. Groups A and B are found in humans.
22. Groups C and G are most often associated with infections in other mammals and only infrequently found in humans.