Question 1

Campylobacter jejuni subsp.jejuni grows best at what conditions?

Accepted Answer

C.jejuni subsp.jejuni grows best at 42°C in microaerobic conditions.The atmosphere can be generated in several ways,including commercially produced,gas-generating envelopes to be used with plastic bags or jars.

Question 2

Curved,microaerophilic,gram-negative rods,with most species having strong urease activity and the majority of which colonize mammalian stomachs or intestines,describe which group of bacteria?

Accepted Answer

In 1983,spiral-shaped organisms resembling campylobacteria were isolated from the human stomach;these organisms were named Campylobacter pylori.On the basis of many studies,the genus Helicobacter was established in 1989,and C.pylori were renamed Helicobacter pylori.At least 32 species are now included in this genus,the majority of which colonize mammalian stomachs or intestines.The genus Helicobacter consists mostly of curved,microaerophilic,gram-negative rods,with most species having strong urease activity.

Question 3

The majority of human infections with Campylobacter species are caused by:

Accepted Answer

Within the genus Campylobacter,C.jejuni and C.coli are most often associated with infections in humans and are usually transmitted via contaminated food,milk,or water.Outbreaks have been associated with contaminated drinking water and improperly pasteurized milk,among other sources.

Question 4

Which organisms should be used to perform quality control on hippurate reagent?

Accepted Answer

Of the organisms listed,only C.jejuni subsp.jejuni and C.coli are positive and negative for hippurate,respectively.C.coli and C.concisus and C.curvus and C.hyointestinalis are hippurate-negative,and C.jejuni subsp.jejuni and C.jejuni subsp.doylei are both hippurate-positive.

Question 5

Virulence determinants of H.pylori include:

Accepted Answer

H.pylori is an effective and significant bacterial pathogen.Motility allows H.pylori to escape the acidity of the stomach and burrow through and colonize the gastric mucosa in close association with the epithelium.Urease enzyme likely plays a significant role in the survival and growth of H.pylori in the stomach by creating an alkaline microenvironment.Other possible virulence determinants include bacterial adhesins for the colonization of mucosal surfaces,mediators of inflammation,and a vacuolating cytotoxin that causes damage to the host cells.

Question 6

Antimicrobial therapy for H.pylori infection consists of:

Accepted Answer

Therapy for H.pylori infection is problematic.H.pylori readily becomes resistant if metronidazole,clarithromycin,azithromycin,rifampin,or ciprofloxacin is administered as a single agent.Current regimens usually use triple-drug therapy that including a proton pump inhibitor,clarithromycin,and either amoxicillin or metronidazole.An alternative and more simple regimen for patients with metronidazole-resistant strains is omeprazole or lansoprazole (proton pump inhibitors that cause rapid symptom relief while working synergistically with the antibiotics)and amoxicillin or clarithromycin.Relapses occur often.Helicobacter spp.associated with enteritis and proctitis may respond to quinolones,but ideal therapy has not been established.

Question 7

A gram-negative,spiral-shaped organism is isolated from a stool sample that was hippurate-positive,catalase-positive,susceptible to nalidixic acid,and resistant to cephalothin.The organism can be identified as:

Accepted Answer

C.jejuni subsp.jejuni and C.jejuni subsp.doylei are both hippurate- and catalase-positive;however,only C.jejuni subsp.jejuni is susceptible to nalidixic acid and resistant to cephalothin.

Question 8

Ensuring that all foods derived from animal sources are thoroughly cooked,all milk is pasteurized,and all drinking water is chlorinated are ways to avoid becoming infected with:

Accepted Answer

No vaccines are available for Campylobacter spp.Because many infections caused by Campylobacter spp.are acquired by ingesting contaminated foodstuffs or water,all foods derived from animal sources,particularly poultry,should be thoroughly cooked.All milk should be pasteurized and drinking water chlorinated.Care must be taken during food preparation to prevent cross-contamination from raw poultry to other food items.

Question 9

Campylobacter spp.can sometimes be detected by direct Gram-stain examination of fecal sample,which would reveal many:

Accepted Answer

Because of their characteristic microscopic morphologic features,that is,their small,curved or seagull-winged,faintly staining,gram-negative rods,Campylobacter spp.can sometimes be detected by direct Gram-stain examination of a stool sample.

Question 10

Which of the following genes may attribute to the virulence of H.pylori by encoding for outer membrane proteins that mediate adherence to a specific blood group antigen on the surface of gastric epithelial cells?

Accepted Answer

babA encodes outer membrane proteins and mediates adherence to blood group antigens on the surface of gastric epithelial cells.The presence of iceA is associated with peptic ulcer disease in some populations;cagA encodes a type IV secretion system for transferring cagA proteins into host cells;and vacA creates vacuoles in epithelial cells,decreases apoptosis,and loosens cell junctions.

Quiz 32: Campylobacter, Arcobacter, and Helicobacter