Module 11: Streptococcus Flashcards by Amanda Belick

What is the clinical significance of Aerococcus viridans?

Opportunistic organism, rarely causes infections

How well did you know this?

Not at all

Perfectly

Does Steptococcus ferment carbohydrates?

Yes and primarily produces lactic acid

How well did you know this?

Not at all

Perfectly

Name some examples of Strep species for each Lancefield group

A - S. pyogenes
B. S. agalactiae
C. S. equisimilis
D. Enterococcus: E. faecalis, E. facium Non-Enterococcus: S. euinus, S. bovis

How well did you know this?

Not at all

Perfectly

What are some streps that do not have a Lancefield grouping?

S. pneumoniae, S. viridans, S. anginosus/milleri

How well did you know this?

Not at all

Perfectly

What do S. anginosus/milleri colonies look like?

Small/pinpoint

Alpha, beta, or gamma

How well did you know this?

Not at all

Perfectly

What is a nutritionally variant Streptococcus?

Group with S. viridans but differ in that a thiol compound (cystine) or vitamin B (pyridoxal) is required for growth

How well did you know this?

Not at all

Perfectly

What does most strep look like in a gram? What species is different and what does it look like?

Mostly gram positive cocci in chains, may be oval

S. pneumoniae is different, usually in pairs, elongated “lancet” shapes

How well did you know this?

Not at all

Perfectly

How do most strep (A, B, C, F, G) colonies look?

Small-large colonies, gray, opaque or translucent, buttery, beta hemolysis (usually)

How well did you know this?

Not at all

Perfectly

What are the growth requirements for most strep?

Mostly facultative, may grow better anaerobically, usually increased CO2 is not necessary
35 degrees
Blood or serum enrichment usually required for good growth

How well did you know this?

Not at all

Perfectly

What causes hemolysis on blood plates?

Streptolysin S and/or Streptolysin O

How well did you know this?

Not at all

Perfectly

What is Streptolysin S?

Produces beta hemolysis

Oxygen stable, acid labile - if agar has fermentable carbohydrates acid is produced and Steptolysin S may be destroyed

How well did you know this?

Not at all

Perfectly

What is Steptolysin O?

Produces beta hemolysis

Oxygen labile, acid labile - exposure to oxygen and acid from carbohydrate fermentation may destroy Streptolysin O

How well did you know this?

Not at all

Perfectly

What are the genus tests for Streptococcus?

Catalase - negative

Nitrate reduction - negative (red after zinc salts)

How well did you know this?

Not at all

Perfectly

What are 2 tests that can give a presumptive ID for GAS?

Bacitracin susceptibility and PYR positive

How well did you know this?

Not at all

Perfectly

What are the 2 tests that can give a definitive ID of GAS?

Latex/co-agglutination tests for specific cell-wall antigen (carbohydrate residue) and GAS-D, DNA probe

How well did you know this?

Not at all

Perfectly

How does the GAS DNA probe work?

Bacteria is lysed off the original swab and the DNA is amplified, usually takes 4 hours

How well did you know this?

Not at all

Perfectly

What are some advantages of GAS DNA probes?

The bacteria do not have to be living, a large number of tests can be done a day, and is it much faster than growing the organism up

How well did you know this?

Not at all

Perfectly

What is the susceptibility of GAS?

Universally susceptible to penicillin
If a patient is allergic erythromycin and tetracycline are considered
Susceptibility not routinely done

How well did you know this?

Not at all

Perfectly

What are the 4 major infections GAS causes?

Upper respiratory (strept throat)
Cutaneous
Invasive infections
Post-streptococcal disease

How well did you know this?

Not at all

Perfectly

What infection does GAS cause in the upper respiratory tract? What are some symptoms and complications?

Acute pharyngitis and strept throat
Symptoms - sudden sore throat, swollen lymph nodes, fever, headache
Complications - ear and sinus infections, meningitis (rare)

How well did you know this?

Not at all

Perfectly

What can acute pharyngitis develop into?

Scarlet fever if the strain of GAS produces a pyrogenic exotoxin
Causes a rash on upper chest which spreads, and strawberry/beefy tongue

How well did you know this?

Not at all

Perfectly

What does GAS cause with cutaneous infections?

Pustular lesions, impetigo, eysipelas (strep infection in dermis, red and thick skin)
Usually disseminate into bacteremia/septicemia (invasive infection)

How well did you know this?

Not at all

Perfectly

What does GAS cause with invasive infections?

Pneumonia, flesh eating disease/necrotizing fascitis

May be called Streptococcal toxic shock, fulminant group A infection, or invasive GAS disease

How well did you know this?

Not at all

Perfectly

What are common symptoms of flesh eating disease?

Cellulitis w/ pain, fever, septic shock, decreased blood pressure, respiratory distress, renal dysfunction, liver dysfunction
30-50% mortality

How well did you know this?

Not at all

Perfectly

What are the 2 post-streptococcal diseases?

Rheumatic fever and acute glomerulonephtitis

What is rheumatic fever?

Caused by GAS with specific M antigens which are similar to myosin in the heart Anti-streptococcal antibodies attach to heart muscle causing inflammation and scarring of the valves May require replacement of valves

What is acute glomerulonephritis?

Antigen-antibody complexes are deposited on the kidney glomerular membranes, activating complement, resulting in membrane damage which allows blood and protein to enter the urine May follow pharyngitis or cutaneous infection

What lab test can determine possible post-streptococcal disease?

Test for antibodies, most frequently Anti-Streptolysin O (ASO) High level = recent infection and possible post-streptococcal disease

How many people may carry GAS in their respiratory tract without infection?

5-15%

What tests can be used for presumptive ID of GBS?

Positive CAMP and positive hippurate hydrolysis

What is the test that can definitively ID GBS?

Latex or co-agglutinaton test to detect specific group B antigens

What bacteria may give a false positive with GBS latex typing? How can it be determined if the organism is GBS or not?

Listeria monocytogenes | Gram stain - GBS are GPC, Listeria are GPB

How does GBS affect neonates?

Can cause serious general infection, neonatal sepsis (rapid or late onset) Most common cause of neonatal sepsis and death

What is rapid onset of GBS sepsis in neonates?

Infection occurs in utero or during birth from a colonized vagina Usually born critically ill with respiratory distress, sepsis, and meningitis High mortality rate

What is late onset of GBS sepsis in neonates?

Occurs weeks after birth (average = 4 weeks) Meningitis is usual Lower mortality

What can GBS cause in adults?

Eye, ear, upper respiratory tract, surgical incision, and other body infections Usually opportunistic and may colonize without infection, commonly in the vagina/rectum (Noraml in feces)

What do GDS colonies look like?

Small-large, gray, buttery, usually non-hemolytic | May grow on MAC without crystal violet (small, deep pink)

What genus test may have a false positive against GDS?

Enterococcus may be catalase pseudopositive

What tests can be used to identify GDS?

Positive BEA (Bile esculin), PYR, 6.5% sodium chloride, and latex/co-agglutination

What type of GDS is PYR positive?

Enterococcus (ex: faecalis, faecium)

What type of GDS is 6.5% sodium chloride positive?

Enterococcus will grow (ex: faecalis, faecium)

What is the pathogenicity of GDS Enterococcus?

Normal fecal and intestinal flora Commonly urinary tract, wound, and miscellaneous infections E. faecium is important nosocomial pathogen due to vancomycin resistance E. faecalis is the most common isolate

What is the pathogenicity of GDS Non-Enterococcus?

S. bovis is the most common isolate | Presence in blood cultures is associated with GI carcinoma/neoplasm

What is the susceptibility of GDS Enterococcus?

``` Sometimes resistant to low dose penicillin and ampicillin (good for UTI, concentrates in urine) Serious infections (endocarditis) treated with aminoglycoside and penicillin combo Aminoglycoside resistance emerging ```

What is the susceptibility of GDS Non-Enterococcus?

S. bovis susceptible to penicillin, combination therapy usually used

What is the susceptibility of GBS?

Susceptible to penicillin (G or amp) Ampicillin and gentamicin combo sometimes used Erythromycin and vancomycin are alternatives for penicillin allergies

What is the significance of GCS and GFS?

Animal pathogens | May cause pharyngitis, pneumonia, septicemia, meningitis, and others

What is the significance of GGS?

Animal pathogens | May cause pharyngitis, otitis media, neonate sepsis, endocarditis, and meningitis

What is VRE?

``` Vancomycin Resistant Enterococcus Important nosocomial pathogen Usually resistant to all antibiotics Mostly affects immunocompromised, may colonize others Normal gut flora Usually E. faecium ```

How is VRE screened for?

Rectal swabs on agar containing vancomycin (agar dilution, 6ug/mL) Growth in 72 hours = VRE if identified as Enterococcus

What organisms could an alpha hemolytic Streptococcus be?

S. pneumoniae or S. viridans

What feature may S. pneumoniae have that other Streptococcus species do not?

A capsule

What does a typical S. pneumoniae colony look like?

Alpha hemolytic, "dimpled"/"life-saver" shaped | May flatten out later due to autolysis from H2O2 accumulation

What tests are used to speciate S. pneumoniae?

Positive/soluble bile solubility, sensitive to optochin (>/= 14mm ZOI), and latex/co-agglutination reactions (pneumoslide)

What is the pathogenicity of S. pneumoniae?

Most common cause of adult lobar pneumoniae usually sudden and with septicemia May also cause otitis media, sinusitis, conjunctivitis, and meningitis (in children spinal fluid is full of neutrophils) Most common cause of death in old people Can be found in the upper respiratory tract without infection

What is the antimicrobial susceptibility for S. pneumoniae?

Drug of choice is penicillin, resistance emerging Susceptibility testing is essential Screening done with oxacillin disc on Mueller Hinton in CO2, >20mm is susceptible

What is the pathogenicity of S. viridans?

Normal upper respiratory tract flora Major cause of subacute bacterial endocarditis, endogenous infection usually from break in oral mucosa after the dentist, predisposed by damaged/scarred heart valves

What is the antimicrobial susceptibility of S. viridans?

Must be performed on all significant isolate | Majority susceptible to penicillin, some resistance

What tests can be used to identify S. viridans?

Negative/insoluble bile solubility, resistant (<14mm) to optochin

Gram positive cocci may be a. Staphylococcus b. Streptococcus c. Both d. Neither

c. both

Organisms that reduce nitrate to nitrite may be a. Staphylococcus b. Streptococcus c. Both d. Neither

a. Staphylococcus

Catalase negative organisms may be a. Staphylococcus b. Streptococcus c. Both d. Neither

b. Streptococcus

Organisms that are facultative anaerobes may be a. Staphylococcus b. Streptococcus c. Both d. Neither

c. both

Organisms where lactic acid is the main end product of fermentation may be a. Staphylococcus b. Streptococcus c. Both d. Neither

b. Streptococcus

S. pneumoniae is a. GAS b. GBS c. GDS d. no group

d. no group

S. agalactiae is a. GAS b. GBS c. GDS d. no group

b. GBS

Enterococcus species is a. GAS b. GBS c. GDS d. no group

c. GDS

S. pyogenes is a. GAS b. GBS c. GDS d. no group

a. GAS

S. bovis is a. GAS b. GBS c. GDS d. no group

c. GDS

Which of the following would indicate an organism is a Streptococcus rather than a Staphylococcus? a. oval cells b. one micrometer in diameter c. clusters d. chain of four

a. oval cells

The following is required fro good growth of S. pyogenes a. oxygen b. carbon dioxide c. enrichment of blood or serum d. none of the above

c. enrichment of blood or serum

Typical colonies of S. pyogenes on blood agar are a. 1mm, opaque, alpha hemolytic b. 2mm, opaque, yellow, beta hemolytic c. 1mm, opaque, white, non-hemolytic d. 1mm, opaque, gray, beta-hemolytic

d. 1mm, opaque, gray, beta hemolytic

Which of the following would explain why a strain of S. pyogenes was beta hemolytic on anaerobic blood agar but non-hemolytic when incubated in air? a. the strain is an obligate aerobe b. the strain has streptolysin O but lacks streptolysin S c. the stain has streptolysin S but lacks streptolysin O d. the strain has neither streptolysin S or O

b. the strain has streptolysin O but lacks streptolysin S

When bacitracin susceptibility testing is being used to identify S. pyogenes a. accuracy is between 98 and 100% b. positive results due to other streptococci will be encountered c. approximately 6% of S. pyogenes will test negative d. results are most accurate when the test is done on the primary plate

b. positive results due to other streptococci will be encountered

Most isolates of S. pyogenes are a. sensitive to penicillin and resistant to erythromycin b. sensitive to penicillin and erythromycin c. resistant to penicillin and sensitive to erythromycin d. resistant to penicillin and erythromycin

b. sensitive to penicillin and erythromycin

Antimicrobial susceptibility testing for S. pyogenes is a. required for all isolates b. required when indicated by treatment failure c. only required for hospital isolates d. never requied

b. required when indicated by treatment failure

Categories of clinical disease caused by S. pyogenes includes all of the following except a. urinary infection b. upper respiratory infection c. cutaneous infection d. invasive infection

a. urinary infection

The most common cause of bacterial pharyngitis is a. S. pneumoniae b. S. pyogenes c. S. agalactiae d. S. aurues

b. S. pyogenes

The etiological agent of scarlet fever is a. S. pyogenes b. S. agalactiae c. S. aureus d. S. bovis

a. S. pyogenes

Most patients with "flesh eating disease" will have the following organism isolated from blood culture a. S. aureus b. E. faecium c. S. agalactiae d. S. pyogenes

d. S. pyogenes

Typical colonies of GBS are a. 1mm, gray, beta hemolytic b. 1-2mm, gray, alpha hemolytic c. 1mm, gray, double zone of hemolysis d. 1mm, gray, gamma hemolytic

a. 1mm, gray, beta hemolytic

A four hour old neonate is seriously ill with septicemia and meningitis. The most likely bacterial cause is a. S. aurues b. S. pyogenes c. E. faecium d. S. agalactiae

d. S. agalactiae

The most likely source infecting bacteria in a four hour old neonate with septicemia and meningitis is a. hospital staff b. vagina of the mother c. hospital environment d. contaminated intravenous fluid

b. vagina of the mother

The following Streptococcus grows on MAC agar without crystal violet a. GAS b. GBS c. GDS d. S. pneumoniae

c. GDS

A Streptococcus that is bile soluble may be a. Group D Enterococcus b. Group D Non-Enterococcus c. both d. neither

d. neither

A Streptococcus that grows in bile salts may be a. Group D Enterococcus b. Group D Non-Enterococcus c. both d. neither

c. both

A Streptococcus that hydrolyzes esculin may be a. Group D Enterococcus b. Group D Non-Enterococcus c. both d. neither

c. both

A Streptococcus that grows in 6.5% sodium chloride may be a. Group D Enterococcus b. Group D Non-Enterococcus c. both d. neither

a. Group D Enterococcus

A Group D Streptococcus that is PYR positive may be a. Group D Enterococcus b. Group D Non-Enterococcus c. both d. neither

a. Group D Enterococcus

Identification of GDS to the species level requires a. series of biochemical tests b. DNA hybridization tests c. serological identification of subgroup antigens d. testing for susceptibility to a battery of antimicrobials

a. series of biochemical tests

Which of the following tends to be the most resistant to antimicrobials? a. S. viridans b. GBS c. Group D Non-Enterococcus d. Group D Enterococcus

d. Group D Enterococcus

Antimicrobials often used in combination to treat enterococcal infections include a. penicillin and tetracycline b. penicillin and aminoglycoside c. penicillin and vancomycin d. erythromycin and tetracycline

b. penicillin and aminoglycoside

The recommended screen test for VRE is a. an agar plate with 6ug/L vancomycin b. a disc diffusion test c. a broth with 6ug/L vancomycin d. an agar plate with an oxacillin disc

a. an agar plate with 6ug/L vancomycin

The organism most likely to be found as normal fecal flora is a. S. agalactiae b. S. viridans c. CNS d. Enterococcus species

d. Enterococcus species

The isolation of the following organism from a blood culture may indicate GI carcinoma a. E. faecalis b. S. agalactiae c. S. bovis d. E. faecium

c. S. bovis

Mucoid, alpha hemolytic colonies that tend to be concave are likely a. S. viridans b. S. pneumoniae c. S. agalactiae d. E. faecalis

b. S. pneumoniae

The carbon dioxide requirements for S. pneumoniae are best described as a. increased CO2 required for all strains b. increased CO2 never required c. increased CO2 required for some strains on primary isolation d. increased CO2 only required if growing on chocolate agar

c. increased CO2 required for some strains on primary isolation

A blood culture broth grew S. pneumoniae on the first subculture but showed no growth on subculture done two days later. The best explanation is a. the first subculture was contaminated b. the bacteria have undergone autolysis c. the blood culture broths have been mixed up d. a hot loop was used for the second subculture

b. the bacteria have undergone autolysis

Bile esculin Streptococcus may be a. S. pneumoniae b. S. viridans c. both d. neither

d. neither

Bile soluble Streptococcus may be a. S. pneumoniae b. S. viridans c. both d. neither

a. S. pneumoniae

Alpha hemolytic Streptococcus may be a. S. pneumoniae b. S. viridans c. both d. neither

c. both

Optochin sensitive Streptococcus may be a. S. pneumoniae b. S. viridans c. both d. neither

a. S. pneumoniae

PYR positive Streptococcus may be a. S. pneumoniae b. S. viridans c. both d. neither

d. neither

The following test may be used for rapid identification of S. pneumoniae a. latex agglutination b. hemagglutination test c. PYR test d. hippurate hydrolysis

a. latex agglutination

The following best describes the susceptibility of S. pneumoniae to penicillin a. all strains are resistant b. all strains are susceptible c. most strains are susceptible but some are resistant d. most strains are resistant but some are susceptible

c. most strains are susceptible but some are resistant

Screening for penicillin resistance in S. pneumoniae requires a. Mueller Hinton agar enriched with blood b. the use of an oxacillin disc c. preparation of inoculum by emulsifying colonies directly in broth d. all of the above

d. all of the above

Which of the following statements does not apply to S. viridans a. includes alpha and gamma hemolytic strains b. a common cause of subacute bacterial endocarditis c. resistant to optochin d. soluble in bile salts

d. soluble in bile salts

Which of the following is most likely to be the cause of adult lobar pneumonia a. S. pyogenes b. S. agalactiae c. S. bovis d. S. pneumoniae

d. S. pneumoniae

S. pneumoniae seen in spinal fluid from patients with meningitis are often seen as a. spherical cocci in pairs b. spherical cocci in chains c. elongated cocci in pairs d. round cocci in clusters

c. elongated cocci in pairs

The most common cause of subacute bacterial endocarditis is a. S. pyogenes b. S. bovis c. S. viridans d. S. pneumoniae

c. S. viridans

There may be more than one correct answer: Tests that may be used for presumptive identification of S. pyogenes include a. bacitracin susceptibility b. CAMP c. PYR d. hippurate hydrolysis

a and c | bacitracin susceptibility and PYR

There may be more than one correct answer: The antigens identified in Streptoocci grouping are a. cell wall antigens b. proteins c. carbohydrates d. capsular antigens

a and c | cell wall antigens and carbohydrates

There may be more than one correct answer: Direct detection of group A antigen from throat swabs a. provides results within 1 hour b. yields few false positives c. may be negative when few bacteria are present d. is suited for home testing

a, b, and c | provides results within 1 hour, yields few false positives, and may be negative when few bacteria are present

There may be more than one correct answer: Post-Streptococcal diseases include a. rheumatic fever b. scarlet fever c. glomerulonephritis d. subacute bacterial endocarditis

a and c | rheumatic fever and glomerulonephritis

There may be more than one correct answer: Presumptive identification tests for GBS include a. CAMP b. PYR c. hippurate hydrolysis d. esculin hydrolysis

a and c | CAMP and hippurate hydrolysis

There may be more than one correct answer: The following clinical specimens give reliable results for direct testing for Group B antigen a. urine b. serum c. spinal fluid d. sputum

a and c | urine and spinal fluid

There may be more than one correct answer: Streptococci with Group D antigens include a. E. faecalis b. S. bovis c. E. faecium d. S. equinus

a, b, c, and d | E. faecalis, S. bovis, E. faecium, and S. equinus

There may be more than one correct answer: Group D antigen identification a. lacks specificity and sensitivity b. involves identification of teichoic acid antigens c. requires specific extraction procedures d. is the most accurate method of identifying GDS

a, b, and c lacks specificity and sensitivity, involves identification of teichoic acid antigens, and requires specific extraction procedures

There may be more than one correct answer: VRE a. are usually E. faecium b. can be screed for using an agar plate with vancomycin c. are important nosocomial pathogens d. are less common now than ten years ago

a, b, and c | are usually E. faecium, can be screened for using an agar plate with vancomycin, and are important nosocomial pathogens

Identify the organism: ``` Alpha hemolytic, translucent, 1mm Gram positive cocci Bile esculin - negative Optochin - resistant Bile solubility - insoluble ```

S. viridans

Identify the organism: ``` Non-hemolyric, translucent, 2mm Gram positive cocci Catalase - negative Bile esculin - positive 6.5% NaCl - positive ```

Group D Streptococcus Enterococcus species

Identify the organism: ``` Beta hemolytic, creamy, opaque Gram positive cocci Catalase - positive Bacitracin - resistant Esculin - positive Slide coagulase - positive ```

S. aureus

Identify the organism: Alpha hemolyric, translucent, 2mm Gram positive cocci Optochin - sensitive Bile solubility - soluble

S. pneumoniae

Identify the organism: ``` Beta hemolytic, opaque, 1mm Gram positive cocci Catalase - negative Bile esculin - negative PYR - positive ```

S. pyogenes

Identify the organism: Alpha hemolytic, translucent, 1mm Gram positive cocci Bile esculin - positive PYR - negative

Group D Streptococcus Non-Enterococcus species

Identify the organism: ``` Beta hemolyric, translucent, 2mm Gram positive cocci Catalase - negative Bacitracin - resistant Group A antigen - negative Bile esculin - negative ``` What is needed to definitively ID this bug?

Streptococcus not group A or D Requires antigen typing, latex/co-agglutination