Anaerobic Bacteria practice quiz

The optimal collection of a wound specimen for culture of anaerobic organisms is a

syringe filled with pus, obtained before administration of antibiotics

Cycloserine-cefoxitin-fructose agar (CCFA) is used for the recovery of:

Clostridium difficile

Obligate anaerobes, facultative anaerobes, and microaerophiles are terms referring to bacteria that require:

Which of the following most affects the oxidation-reduction potential (Eh or redox potential) of media for anaerobic bacteria?

pH

Which of the following is the medium of choice for the selective recovery of gram-negative anaerobes?

Kanamycin-vancomycin (KV) agar

Anaerobic bacteria are routinely isolated from all of the following types of infections except:

Urinary tract infections

Methods other than packaged microsystems used to identify anaerobes include:

Gas-liquid chromatography (GLC)

Which broth is used for the cultivation of anaerobic bacteria in order to detect volatile fatty acids as an aid to identification?

Prereduced peptone-yeast extract-glucose (PYG)

Egg yolk agar is used to detect which enzyme produced by Clostridium species?

Lecithinase

Which of the following organisms will display lipase activity on egg yolk agar?

All of these options

C. botulinum

C. sporogenes

C. noyvi A

A gram-positive spore-forming bacillus growing on sheep-blood agar anaerobically produces a double zone of β-hemolysis and is positive for lecithinase. What is the presumptive identification?

Clostridium perfringens

Which spore type and location is found on Clostridium tetani?

Round, terminal spores

Gram-positive bacilli recovered from two blood cultures from a 60-year-old diabetic patient gave the following results:

Spores seen = Neg Hemolysis = + (double zone)

Motility = Neg Lecithinase = +

Volatile acids by GLC (PYG) = acetic acid (A) and butyric

acid (B)

What is the most likely identification?

Clostridium perfringens

Which mechanism is responsible for botulism in infants caused by Clostridium botulinum?

Ingestion of preformed toxin in food

The classic form of foodborne botulism is characterized by the ingestion of:

Preformed toxin in food

Which test is performed in order to confirm an infection with Clostridium botulinum?

Toxin neutralization

Which Clostridium spp. causes pseudomembranous colitis or antibiotic-associated colitis?

C. difficile

Identification of Clostridium tetani is based upon:

Clinical findings

Obligate anaerobic gram-negative bacilli that do not form spores grow well in 20% bile and are resistant to penicillin 2-unit disks are most likely:

Bacteroides fragilis gp.

Which Bacteroides spp. is noted for "pitting" of the agar and is sensitive to penicillin 2-unit disks?

B. ureolyticus

Which gram-negative bacilli produce black pigment and brick red fluorescence when exposed to an ultraviolet light source?

Porphyromonas spp. and Prevotella spp.

The following characteristics of an obligate anaerobic gram-negative bacilli best describe which of the listed genera?

Gram stain: long, slender rods with pointed ends

Colonial appearance: dry bread crumbs or "fried-egg" appearance

Penicillin 2-unit disk test: Susceptible

Fusobacterium spp

All of the following genera are anaerobic cocci that stain gram positive except:

Veillonella spp

The gram-positive non-spore-forming anaerobic rods most frequently recovered from blood cultures as a contaminant are:

Propionibacterium acnes

Which Clostridium species is most often recovered from a wound infection with gas gangrene?

C. perfringens

Gram stain of a smear taken from the periodontal pockets of a 30-year-old man with poor dental hygiene showed sulfur granules containing gram-positive rods (short diphtheroids and some unbranched filaments). Colonies on blood agar resembled "molar teeth" in formation. The most likely organism is:

Actinomyces israelii

Antimicrobial susceptibility testing of anaerobes is done by which of the following methods?

Microtube broth dilution

An aspirate of a deep wound plated on blood agar plates and incubated aerobically and anaerobically. At 24 hrs there was growth on both plates. This indicates that the organism is an

faculty anaerobe

The characteristic that is most commonly associated with the presence of strict anaerobic bacteria and can be taken as presumptive evidence of their presence in a clinical specimen is the

presence of a foul, putrid odor from tissue specimens and culture

Gram stain of a thigh wound showed many Gram-positive spore-forming bacilli. The

specimen was placed on brain heart infusion blood agar and incubated aerobically at

35°C for 3 days. At the end of that time, the plates showed no growth. The most likely

explanation is that some of the specimen should have been incubated:

anaerobically

An aspirate of a deep wound was plated on blood agar plates aerobically and anaerobically.

At 48 hours there was growth on the anaerobic plate only. The next step in the evaluation

of this culture Is to:

Gram stain and begin organism identification

Correct answer

In general, anaerobic infections differ from aerobic infections in which one of the following?

they are usually polymicrobic

Which of the following pairs of organisms usually grow on kanamycin, vancomycin, laked

blood agar?

Bacteroides and Prevotella

Acceptable specimen sources for culture of anaerobic bacteria includes:

abscess

Propionibacterium aces is most often associated with:

blood culture contamination

The etiologic agent of botulism is:

an exotoxin producer

Organisms associated with human bites?

Viridans strep, Eikenella, Fusobacterium, Porphyromonas-Prevotella, Peptostreptococcus

Disease caused by ingestion of a preformed neurotoxin that causes symptoms of neuromuscular paralysis

Botulism

A strict anaerobe that produces terminal spores is:

Clostridium tetani

An anaerobic, box-car shaped, beta hemolvtic Gram-positive bacillus isolated from a foot

wound is most likely

Clostridium perfringens

The laboratory is considering adoption of a rapid and sensitive "stand alone" method

ONLY

that detects Clostridium difficile toxins A and B. Which one of the following testing

methodologies will provide this?

NAAT

The reverse CAMP test, lecithinase production, double zone hemolysis, and Gram stain

morphology are all useful criteria in the identification of:

Clostridium perfringens

Which one of the following anaerobes is inhibited by sodium polyanethol sulfonate (SPS)

Peptostreptococcus anaerobius

Clostridium difficile can be detected by:

glutamate dehydrogenase

Anaerobic Gram-positive bacilli with subterminal spores were isolated from a peritoneal

abscess. The colony has a swarming appearance. The most likely identification of this

organism is:

Clostridium septicum

If a stool sample is sent to the laboratory to rule out Clostridium difficile, what medium

should the microbiologist use and what is the appearance of this organism on this

medium?

CCFA: yellow, ground glass colonies

A Gram stain of a peritoneal fluid showed large Gram-positive bacilli. There was 3+ growth

on anaerobic media only, with colonies producing a double zone of hemolysis. To assist

with the classic identification of the organism, the microbiologist could:

set up egg yolk agar plate

A patient has a suspected diagnosis of subacute bacterial endocarditis. His blood cultures grow non spore-forming pleomorphic Gram-positive bacilli only in the anaerobic bottle.

What test(s) will give a presumptive identification of this microorganism?

catalase and spot indole

The Gram stain of drainage from a pulmonary sinus tract shows many WBCs and 3+ branching Gram-positive bacilli. Colonies grow only on anaerobic media after 3 days

incubation. They are yellow-tan and have a molar tooth appearance. The most likely

genus is:

Actinomyces

Which organism is the most common anaerobic bacteria isolated from infectious processes of soft tissue and anaerobic bacteremia?

Bacteroides fragilis

An organism from a peritoneal abscess is isolated on kanamycin-vancomycin laked blood agar and grows black colonies on BBE agar. It is nonpigmented, catalase positive, and

indole negative. The genus of this organism is:

Bacteroides

Which of the following sets of organisms may exhibit a brick red fluorescence?

Prevotella melaninogenica and Porphyromonas asaccharolytica

A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobic culture of a lung abscess after 72 hours, was found to fluoresce brick-red under ultraviolet light. A Gram

stain of the organism revealed a coccobacillus that had the following characteristics:

growth in bile: inhibited

vancomycin: resistant

kanamycin: resistant

colistin: susceptible

catalase: negative

esculin hydrolysis: negative

indole: negative

The identification of this isolate is:

Prevotella melaninogenica

A thin, Gram-negative bacillus with tapered ends isolated from an empyema specimen grew only on anaerobic sheep blood agar. It was found to be indole positive, lipase

negative, and was inhibited by 20% bile. The most probable identification of this isolate

would be:

Fusobacterium nucleatum

The presence of 20% bile in agar will allow growth of:

Bacteroides fragilis

A control strain of Clostridium should be used in an anaerobe jar to assure that:

an anaerobic environment is achieved

Which one of the following organisms could be used as the positive quality control test for

lecithinase on egg yolk agar?

Clostridium pertringens

The potentially lethal intoxication type of food poisoning often associated with improperly canned food is caused by

Clostridium botulinum

Which of the following is not considered a zoonotic disease?

Botulism

An anaerobically incubated blood agar plate shows colonies surrounded by an inner zone of complete red cell lysis and an outer zone of incomplete cell lysis (double zone of hemolysis). The most likely presumptive identification of this isolate would be

Clostridium perfringens

A cervical mucosal abscess specimen was sent to the laboratory for bacteriologic examination. The culture of this sample grew and anaerobic gram-negative bacilli that was inhibited by bile, produced a black pigment, and was negative for indole production and positive for glucose, sucrose, and lactose fermentation. This isolate would most likely be

Prevotella melaninogencia

Which one of the following is not true of Clostridium tetani?

It produces rapid tissue necrosis.

The characteristic colony morphology of Actinomyces israelii on solid agar resembles

A molar tooth

What is the predominant indigenous flora of the colon?

Anaerobic, gram-negative, non-spore-forming bacteria

Obligately 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 fragilisgroup

Which of the following is described as obligately anaerobic gram-positive cocci?

Peptostreptococcus

Growth on kanamycin-vancomycin laked blood agar incubated anaerobically is primarily used for

Bacteroides fragilis

The diagnosis of pseudomembranous colitis (Clostridium difficile associated disease) is often made by

Assays to detect toxin in stool

The anaerobic, gram-negative, curved, motile bacilli associated with bacterial vaginosis belong to the genus

Mobiluncus

An infant was seen in the emergency department with symptoms of neuromuscular weakness and constipation. The diagnosis of infant botulism was confirmed by the demonstration of toxin in the child's stool. The child most likely contracted this disease by

Ingestion of spore that germinated in the intestine

The majority of the gram-positive, non-spore-forming, anaerobic bacilli isolated from clinical material will be

Propionibacterium acnes

Which of the following clostridia has a terminal spore that causes the cell to swell?

C.tetani

The gram-negative, non-spore-forming, anaerobic bacillus frequently implicated in serious clinical infections such as brain and lung abscesses is

Fusobacterium nucleatum

Which one of the following is a non-spore-forming, gram-positive, anerobic bacillus?

Propionibacterium

Which of the following statements is not characteristic of Clostridium botulinum?

Oval spores are located terminally.

Identify the Fusobacterium sp. considered to tge the most frequent isolate recovered from clinical infections.

F.nucleatum

Septicemia caused by which of the following is generally associated with an underlying maliganancy?

Clostridium septicum

Which of the following is the most potent bacterial exotoxin known?

Botulinum toxin

Which Clostridium sp. is most commonly recovered from cases of gas gangrene?

C.perfringens

Which of the following organisms in not gram-positive?

Suttonella wadsworthensis

Which of the following statements is not true of clostridia?

C.tetanispores will form in the presence of oxygen; therefore, anaerobiosis in a wound is not required to cause tetanus.

Gram-positive bacilli with central spores are seen in the direct Gram stain of a tissue biopsy. After 24 hours of incubation, no growth is seen on the sheep blood agar plate incubated aerobically and the chocolate agar plate incubated in increased CO2. Which of the following is the likely cause of this infection?

Clostridium

Small alpha-hemolytic colonies are seen on a sheep blood agar plate after 48 hours of incubation on a vaginal culture. This describes which of the following?

Lactobacillus

Which of the following statements is true regarding Clostridium perfringens?

: Alpha-toxin is produced by all strains.

Which is a correct statement regarding Clostridium tetani?

It produces terminal spores

Which anaerobic, gram-negative rod can be presumptively identified by its Gram strain morphology, and inhibition by bile and 1-ug kanamycin disk?

Fusobacterium nucleatum

Which of the following tests is most appropriate for the presumptive identification of Prevotella melaninogencia?

Fluorescence test

Which of the following tests is most appropriate for the presumptive identification of Clostridium difficile?

Cytotoxin assay

Which of the following tests is most appropriate for the presumptive identification of Clostridium perfringens?

Reverse CAMP test

Which of the following tests is most appropriate for the presumptive identification of Peptostreptococcus anaerobius?

SPS disk

A curved appearance on Gram stain is characteristic of which of the following?

Fusobacterium nucleatum

Purulent material from a cerebral abscess was submitted to the laboratory for smear and culture. On direct Gram stain, gram-positive cocci in chains and gram-negative bacilli with pointed ends were seen. Plates incubated aerobically exhibited no growth at 24 hours. On the basis of the organisms seen on the smear, what is the most likely presumptive identification of the etiologic anaerobic agents?

Fusobacteriumsp. andPeptostreptococcussp.

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

Polysaccharide capsule

Which of the following is not true of Bacteroides fragilis?

Among the most antimicrobial-sensitive anaerobic bacteria

Aspiration of vomitus can lead to pneumonia. Which of the following would not be likely causative agent in aspiration pneumonia?

Mobiluncussp.

To ensure that anaerobic conditions have been achieved in anaerobic jars or chambers, an oxygen-sensitive indicator is employed, such as

Methylene blue

Egg yolk agar showing a precipitate in the medium surrounding the colony is positive for

Lecithinase production

After 72 hours of anaerobic incubation, small olive-green to black colonies are seen. A Gram stain reveals gram-positive cocci. What is the most likely identification of the organism?

Peptoccus niger

Which of the following is an important cause of food poisoning?

Clostridium perfringens

Which bacterium is part of the normal vaginal flora that helps resist the onset of bacterial vaginosis?

Lactobacillussp.