FINAL micro quiz

An organism was inoculated to a TSI tube and gave the following reactions: Acid slant/acid butt No H2S Produced gas The organism most likely is: 1. Klebsiella pneumoniae 2.Shigella dysenteriae 3. Salmonella typhimurium 4. Salmonella typhi

1. Klebsiella pneumoniae

The beta-hemolysis produced by group A Streptococcus seen on the surface of a sheep blood agar plate is primarily the result of streptolysin: 1. M 2. O 3. H 4. S

4. S

A TSI tube inoculated with an organism gave the following reactions: Alkaline slant/Acid butt No H2S No gas produced The organism is most likely: 1.Yersinia enterocolitica 2.Salmonella typhi 3.Salmonella enteritidis 4.Shigella dysenteriae

4.Shigella dysenteriae

Nonmetallic surfaces contaminated with blood should be disinfected with:

5% bleach (sodium hypochlorite)

A 12-year-old girl goes to the doctor complaining of a sore throat, fever, headache, and general malaise. The doctor does a quick strep test that is positive for group A beta-hemolytic Streptococcus. No antibiotic testing is needed because Streptococcus is:

Universally susceptible to penicillin

What organism mostly commonly causes gas gangrene?

C. perfringens

What organism is the most common cause of bacterial gastroenteritis worldwide?

Campylobacter jejuni

What test differentiates staphylococci from streptococci?

Catalase

What medium will sustain the growth of most Haemophilus spp.?

Chocolate agar

All of the following are non-spore-forming, anaerobic, gram-positive bacilli EXCEPT:

Clostridium

An elderly patient in a nursing home is recovering from bacterial pneumonia. The patient has been on a lengthy regiment of antibiotics to kill the organism causing the disease. A few days later, the patient is diagnosed with pseudomembranous colitis. What organism is the most likely cause?

Clostridium difficile

The tests used to detect clumping factor will differentiate Staphylococcus aureus from other staphylococcal species. What are these tests?

Coagulase and latex agglutination

Which organism is the most common cause of urinary tract infections (UTIs) in humans?

Escherichia coli

The stock cultures needed for quality control testing of oxidase production are:

Escherichia coli/Pseudomonas aeruginosa

Which of the following organisms does not require susceptibility testing when isolated from a clinically significant source?

Group A streptococci

Which species of Haemophilus requires both X and V factors?

H. influenzae

What biochemical test will differentiate nonfermenters from Enterobacteriaceae (except Plesiomonas)?

Oxidase

Characteristics of Moraxella include:

Oxidase-positive and nonmotile, Biochemically inert and aerobic, & Susceptible to penicillin and opportunistic pathogens

A microbiologist is reading the plates from a sputum culture. On the sheep blood agar (SBA), she sees flat spreading colonies with a metallic sheen. On cetrimide agar, she sees a fluorescent green color in the media with clear colonies. On MacConkey, she sees medium clear colonies that have a fruity or grape-like odor. What is the most likely organism?

P. aeruginosa

A technician is reading plates from a cerebrospinal fluid (CSF) culture. She notices that there is growth on chocolate agar (CHOC), but no growth on sheep blood agar (SBA) or MacConkey (MAC) agar. The Gram stain showed a gram-negative bacillus. What organism should be suspected?

Haemophilus influenzae

Which of the following is an important virulence factor of Bacteroides fragilis?

Polysaccharide capsule

Isolation of Neisseria gonorrhoeae:

Requires incubation under increased CO2

This staphylococcus produces wide zones of beta hemolysis on 5% sheep blood agar.

S. aureus

A laboratory professional is testing a new antimicrobial soap. The tech washes her forearm, then does a culture of the skin. Which organisms should she expect to find growing in the culture?

S. epidermidis and Propionibacterium

All of the following staphylococci are coagulase positive EXCEPT:

S. saprophyticus

An organism was inoculated into a TSI tube and gave the following reactions: Alkaline slant/acid butt, H2S, gas produced This organism most likely is: 1.Klebsiella pneumoniae 2.Shigella dysenteriae 3.Salmonella typhimurium 4. Escherichia coli

Salmonella typhimurium

What type of bacteria are those in the genus Clostridium?

Spore-forming anaerobic bacilli

Of the following bacteria, the most frequent cause of prosthetic heart valve infections occuring within two to three months after surgery is:

Staphylococcus epidermidis

The novobiocin susceptibility test is used for the identification of:

Staphylococcus saprophyticus

What is one of the most common diseases caused by streptococci?

Strep throat

An important cause of acute exudative pharyngitis is:

Streptococcus pyogenes

GRAM-POSITIVE COCCI, NONMOTILE, NONSPOREFORMING CATALASE: NEGATIVE, OXIDASE: NEGATIVE, FACULTATIVELY ANAEROBIC. Colonies are surroundend by a wide zone of beta-hemolysis. Most strains are susceptible to erythromycin (macrolides) and clindamycin (lincosamides) - fig. B. Positive PYR test is useful for preliminary identification of isolated strains (together with negative catalase test). Identification is confirmed by latex aglutination. Infections include pharyngitis ("strep throat")and localized skin infection ("impetigo"). Erysipelas and cellulitis.

Streptococcus pyogenes

Which of the following is the most appropriate method for collecting a urine specimen from a patient with an indwelling catheter?

aspirate urine aseptically from the catheter tubing

Streptococci are unable to synthesize the enzyme:

catalase

Which of the following is the most appropriate specimen source and primary media battery?

endocervical - chocolate, Thayer- Martin

The organism most commonly associated with neonatal purulent meningitis is:

group B streptococci

Which of the following combinations of organisms would be appropriate as controls to test the functions listed?

indole - Escherichia coli and Proteus mirabilis

Which of the following groups of specimens would be acceptable for anaerobic cultures?

pleural fluid, brain abscess

A characteristic helpful in separating Pseudomonas aeruginosa from other members of the Pseudomonas family is:

production of pyocyanin pigment

Upon review of a sputum Gram stain, the technician notes that the nuclei of all of the neutrophils present in the smear are staining dark blue. The best explanation for this finding is the:

slide was inadequately decolorized with acetone/alcohol

Which of the following factors would make an organism appear to be more resistant on a disk difusion susceptibility test?

too many organisms in the inoculum

Staphylococcus saprophyticus, a recognized pathogen, is a cause of:

urinary tract infections

Obligate anaerobic, gram-negative bacilli, recovered from an abdominal wound, were found to be resistant to penicillin. Growth of this organism was not inhibited by bile. What is the most likely identification of this isolate?

Bacteroides fragilis group

The K antigen of the family Enterobacteriaceae is:

Heat labile

A culture from a CSF specimen grows gray, mucoid, stringy colonies on sheep blood. The isolate grows readily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results: ONPG: positive Indole: negative Glucose: positive Oxidase: negative Citrate: positive VP: positive

Klebsiella pneumoniae

Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines. Catalese (+) Oxidase ( - ). Is urea positive (blue color of the slope), metabolise glucose with production of gas and is lactose positive (but on Endo agar its colonies often remain quite pale). lysine "+", ornithine "-", arginine. "-" . The most common infection caused outside the hospital is pneumonia.

Klebsiella pneumoniae

All Neisseria spp. are generally all of the following EXCEPT:

Motile

What are the names of the two diseases caused by Legionella species?

Legionnaire's disease and Pontiac fever

GRAM-NEGATIVE DIPLOCOCCI, NONMOTILE, NONSPOREFORMING, CATALASE: POSITIVE, OXIDASE: POSITIVE AEROBES. require complex growth media and are highly susceptible to toxic substnces (e.g., fatty acids). Gonococci are not able to grow on common blood agar. Often use media resembling chocolate agar in appearance(e.g., modified Thayer-Martin agar(MTM) or Martin-Lewis agar(ML)) Plates are always incubated in a CO2-enriched, humid atmosphere (some gonococci require CO2 for growth, the growth of all species is enhanced by CO2). Infection of the genitals can result in a purulent (or pus-like) discharge from the genitals which may be foul smelling, inflammation, redness, swelling, dysuria and a burning sensation during urination.

Neisseria gonorrhoeae

The smallest concentration of antimicrobial agent which prevents growth in subculture or results in a 99.9 % decrease if the initial inoculum, is the definition of:

minimum bacteriocidal concentration