9 Vibrio Species and Campylobacter (20)

Question 1

Case
A 54-year-old man in Louisiana presents with a 2-day history of fever, chills, and diarrhea; he now has painful, hemorrhagic, bullous lesions on his lower extremities. His blood pressure is 60/40 mmHg. He consumed uncooked oysters 3 days earlier; 6 months ago he was diagnosed with liver cirrhosis. Clinical samples from the bullous lesions, blood, and stool are sent for microbiological investigations; the patient is placed on tetracycline. Stool and the samples from the skin lesions are inoculated on various media including thiosulfate-citrate-bile salts-sucrose (TCBS) agar. After 24 hours of incubation at 37°C, green colonies appear on the TCBS agar. Further study of the colonies show actively motile, Gram-negative curved rods that are oxidase-positive and ferment lactose; they grow in the presence of 6% sodium chloride. The isolate fails to grow in the absence of sodium chloride and is susceptible to compound O/129. Samples from the skin lesions and blood cultures also grow organisms with the same characteristics.

What bacteria is most likely responsible for the patient’s symptoms?

1 Vibrio fluvialis
2 Aeromonas hydrophila
3 Plesiomonas shigelloides
4 Vibrio parahemolyticus
5 Vibrio vulnificus

Answer 1

Vibrio vulnificus

The clinical presentation of the patient following the consumption of uncooked oysters is typical of an invasive infection by the halophilic marine bacterium Vibrio vulnificus. The patient having liver cirrhosis increases the risk of infection by this Vibrio. The morphology, motility, colony characteristics on TCBS medium, a positive oxidase reaction, lactose fermentation, and the ability to grow in the presence of 6% sodium chloride are characteristics of Vibrio vulnificus, which can often produce fatal human infections. The organism is a natural inhabitant of the warm coastal waters of the Gulf coast, mostly related to seafood consumption (especially raw oysters). Following hurricane Katrina, which struck the Gulf coast in 2005, the number of infections with V. vulnificus reportedly increased in the city of New Orleans; this was attributed to the exposure of open wounds to the seawater that caused extensive flooding of the city. Risk factors for severe invasive disease include underlying immunocompromising conditions, or diseases which lead to elevated serum iron levels (e.g., liver cirrhosis, hemochromatosis, and thalassemia).
Infection can lead to primary septicemia and shock, accompanied by hemorrhagic, bullous, necrotic cutaneous lesions that often involve the extremities. Such infections are associated with >50% mortality. Gastrointestinal symptoms (e.g., nausea, vomiting, and diarrhea) are seen in some patients. The elevated serum and tissue levels of iron in patients with liver disease may provide a nutrient substrate for Vibrio to proliferate. Various factors contribute to the virulence of V. vulnificus (e.g., its lipopolysaccharide, capsular lipopolysaccharide, type IV pili, cytolysins, metalloprotease, and siderophore). The occurrence of cutaneous lesions in the extremities is explained by the laboratory observation that the bacterium is able to produce metalloprotease more efficiently at lower temperatures (25°+C). In humans, this optimum condition is available in the interstitial tissues of the limbs where the temperature is less than the internal body temperature. Metalloprotease has many biological functions; it causes degradation of a variety of host proteins and enhances vascular permeability through inflammatory mediators.
Combination therapy with doxycycline or tetracycline and one of the third-generation cephalosporins is generally used for treatment. Recently, single therapy using newer fluoroquinolones has also been found to be equally effective. Children in whom doxycycline and fluoroquinolones are contraindicated are treated with trimethoprim/sulphamethoxazole and an aminoglycoside. When there is a clinical suspicion of a V. vulnificus infection, prompt specific antibiotic therapy and immediate radical debridement of necrotic tissue are essential and life-saving.
Vibrio fluvialis is a halophilic marine bacterium that causes watery diarrhea. The infection has been reported in various parts of the world, including the United States. The most common source of infection is uncooked shellfish. Though very rarely, this bacterium has been associated with wound infection and sepsis. V. fluvialis ferments sucrose and produces yellow colonies on a TCBS medium, one of the differentiating features from V. vulnificus.
Aeromonas hydrophila is Gram-negative and motile; it produces large zones of hemolysis on blood agar. It is oxidase-positive and produces yellow colonies on TCBS agar; it is a sucrose fermenter. It does not grow in the presence of 6% sodium chloride and is resistant to the compound O/129. It is commonly found in fresh water. This bacterium has been isolated from fresh water fish, clams, oysters, many animals, and humans. Though human infections are rare, it is a potential pathogen. Aeromonas hydrophila is reported to cause skin and soft tissue infections, infection of burns, respiratory infections, and gastroenteritis. Predisposing factors are immunosuppression, chronic diseases, or trauma in an aquatic environment.
Plesiomonas shigelloides is a motile, Gram-negative bacillus common in tropical and subtropical areas. This bacterium has been isolated from fresh water fish, clams and oysters, many animals, and humans. It is oxidase-positive and produces green-colored colonies on TCBS agar; it does not ferment sucrose. P. shigelloides is able to grow in the absence of sodium chloride and does not ferment lactose. It is DNase-positive and shares antigens with Shigella sonnei. It is rarely associated with food-borne outbreaks and there are very few reports of isolation of P. shigelloides from blood and other septic lesions.
Vibrio parahemolyticus is a halophilic marine bacterium that causes acute gastroenteritis following the ingestion of raw fish or shellfish. Contaminated food and exposure of wounds to seawater can also lead to infection by this bacterium. Occasionally, the infection can lead to septicemia. Infection by V. parahemolyticus is highly prevalent in southeast Asian countries. Clones of pandemic strains have been identified; these are found to be the predominant isolates from various southeast Asian countries. In the United States, this organism is the leading cause of bacterial diarrhea associated with seafood consumption. Foodborne outbreaks and sporadic infections have been reported. One of the largest known outbreaks in the United States was caused by the serotype O6:K18 following the consumption of raw seafood from Alaska. Virulent strains of V. parahemolyticus are found to possess the tdh (thermostable direct hemolysin) gene, which codes for the production of a thermostable hemolysin. In the laboratory, the bacterium can be differentiated from V. vulnificus by various phenotypic reactions. Molecular methods are available for confirming the identification of various Vibrios.

Question 2

A 24-year-old Indian man presents to his physician with 4-day history of progressive weakness in the legs. The patient states that he is now also having weakness in his arms. History is significant for gastroenteritis 1 week ago. A spinal tap is performed and a CSF analysis is pending. Which of the following is true regarding the organism that is associated with this disease?

1 Gram positive anaerobic rod
2 Gram positive aerobic rod
3 Gram negative rod
4 Gram negative diplococci
5 Gram positive cocci

Answer 2

Gram negative rod

The correct answer choice is Gram negative rod. This patient presents with ascending paralysis and a notable history of gastroenteritis. This patient most likely has Guillain Barre Syndrome (GBS). Campylobacter jejuni is the most commonly associated organism with the preceding gastroenteritis that is associated with GBS. C. jejuni is a Gram negative curved rod.
Clostridium tetani is an example of a Gram positive anaerobic rod.
Corynebacterium diptheria is an example of a Gram positive aerobic rod.
Neisseria are Gram negative diplococci.
Staphylococcus are Gram positive cocci.

Question 3

Which one of the following organisms causes diarrhea that is associated with eating raw or uncooked seafood?

1 Vibrio cholerae
2 Vibrio parahaemolyticus
3 Moraxella nonliquefaciens
4 Escherichia coli
5 Helicobacter pylori

Answer 3

Vibrio parahaemolyticus

Vibrio parahaemolyticus is a major cause of diarrhea in Japan and is transmitted by eating contaminated seafood. Vibrio cholerae causes cholera. Cholera is transmitted by the fecal-oral route. Moraxella nonliquefaciens causes blepharitis or infection of the eyelid. Escherichia coli causes urinary tract infection, sepsis, neonatal meningitis and traveler’s diarrhea. Helicobacter pylori causes peptic ulcers.

Question 4

The major difference between Campylobacter jejuni and Campylobacter intestinalis is that

1 C. jejuni grows best at 42° C while C. intestinalis grows best at 37° C.
2 C. jejuni is microaerophilic while C.intestinalis is anaerobic
3 C. jejuni is gram-negative while C. intestinalis is gram-positive
4 C. jejuni is spread by oral-fecal route while C. intestinalis is spread by airborne droplets
5 C. jejuni causes bacteremia while C. intestinalis causes enterocolitis

Answer 4

C. jejuni grows best at 42° C while C. intestinalis grows best at 37° C.

C. jejuni grows best at 42° C while C. intestinalis grows best at 37° C. C. jejuni and C. intestinalis are both microaerophilic, gram-negative and are spread by oral-fecal route. C. jejuni cause enterocolitis while C. intestinalis cause bacteremia.

Question 5

Which of the following is a halophilic organism?

1 Escherichia coli
2 Shigella sonnie
3 Gardnerella vaginalis
4 Salmonella typhi
5 Vibrio vulnificus

Answer 5

Vibrio vulnificus

Halophiles grow in the presence of medium containing high concentration of sodium chloride. Vibrio vulnificus and Vibrio parahaemolyticus are halophiles from seawater. Vibrio vulnificus can cause skin lesion in individuals who handle shell fish or other marine animals.
Ingestion of seafood can result in gastroenteritis from Vibrio parahaemolyticus.

Question 6

A 21-year old male student was brought to hospital in Baltimore city along with his 20 year old fiancee with history of abdominal cramps, headache, vomiting and explosive watery diarrhea. The sickness started 28 hours after the couple attended a crab feast. The condition of the couple improved after replacement of fluid and electrolyte. The stool culture yielded oxidase positive colonies on blood agar and green colonies on TCBS medium. The gram staining of isolates from TCBS revealed gram negative curved rods. Which of the following is the etiological agent?

1 Vibrio parahaemolyticus
2 Escherichia coli
3 Shigella boydii
4 Salmonella typhimurium
5 Staphylococcus aureus

Answer 6

Vibrio parahaemolyticus

Vibrio parahaemolyticus is associated with gastroenteritis caused by consumption of seafood. It is gram negative comma shaped curved rod. It gives oxidase positive colonies on blood agar. It does not ferment sucrose therefore appears green on TCBS agar (thiosulfate citrate bile salt agar). However, sucrose fermenting Vibrio cholerae appears yellow on the TCBS agar.
Escherichia coli, Shigella boydii, and Salmonella typhimurium are oxidase negative gram negative rods.
Staphylococcus aureus is gram positive cocci.

Question 7

Which of the following organism is associated with primary septicemia and wound infection and is referred to as the lactose-positive Vibrio ?

1 Vibrio alginolyticus
2 Vibrio cholerae
3 Vibrio parahaemolyticus
4 Vibrio vulnificus

Answer 7

Vibrio vulnificus

Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio alginolyticus are non lactose fermenters. However, Vibrio vulnificus is a halophile that ferments lactose and is associated with very serious type of infections. It is implicated in septicemia after consumption of shellfish and has high mortality rate (40 to 60%). Exposure to contaminated sea water can lead to wound infection which is characterized by swelling, erythema, and pain. These can develop into vesicles or bullae and tissue necrosis along with fever and chills. The patients with hepatic disease, hematopoietic disease, or chronic renal failure are at higher risk of severe infections.

Question 8

Which of the following Vibrio species requires 3% NaCl for growth and can tolerate up to 10% NaCl?

1 Vibrio alginolyticus
2 Vibrio cholerae
3 Vibrio parahaemolyticus
4 Vibrio vulnificus

Answer 8

Vibrio alginolyticus

Vibrio alginolyticus is a strict halophile and is least pathogenic for humans. It is associated with eye, ear, burn, and wound infection following exposure to seawater. It requires at 3% NaCl for the growth and can survive salt concentration up to 10% NaCl. It is sucrose fermenter and yields yellow colonies on TCBS agar.

Question 9

The action of choleragen toxin produced by Vibrio cholerae is similar to the toxin produced by

1 Corynebacterium diphtheriae
2 Enterotoxigenic Escherichia coli
3 Shigella dysenteriae type 1
4 Pseudomonas aeruginosa

Answer 9

Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli produces heat labile toxin that resembles choleragen, toxin produced by Vibrio cholerae. Both toxins cause accumulation of cAMP in the intestinal mucosa and initiate the hypersecretion of electrolytes and fluids into the lumen, that leads to watery diarrhea.
Exotoxin A of Pseudomonas aeruginosa resembles the toxin produced by Corynebacterium diphtheriae.
Shigella dysenteriae type 1 resembles the verotoxin I produced by Escherichia coli O157:H.

Question 10

Which of the following is the most common cause of bacterial gastroenteritis worldwide?

1 Vibrio cholerae
2 Vibrio parahaemolyticus
3 Campylobacter jejuni
4 Salmonella paratyphi
5 Shigella sonnie

Answer 10

Campylobacter jejuni

Campylobacter jejuni is the most common etiological agent of bacterial gastroenteritis. Children younger than 1 year and adults between 20 and 29 are mostly affected with the disease. The infection is transmitted by different modes:
Direct exposure to animals
Handling infected pets
Consumption of contaminated water, dairy products and improperly cooked poultry
Sexual contact

Question 11

Campylobacter are

1 Fermentative
2 S-shaped gram positive rods
3 Oxidase positive and motile
4 Facultative aerobes

Answer 11

Oxidase positive and motile

The characteristic features of Campylobacter are as follows:
Curved gram negative rod
Characteristic s-shaped with “seagull-wing” appearance
Motile with single polar flagellum and exhibits darting motility
Oxidase positive
Microaerophilic and capnophilic
Non-fermentative

Question 12

Which of the following is commonly associated with gastric and duodenal ulcers?

1 Campylobacter rectus
2 Escherichia coli
3 Helicobacter pylori
4 Pasteurella multocida
5 Vibrio cholerae

Answer 12

Helicobacter pylori

Helicobacter pylori is a major pathogen associated with gastric and duodenal ulcers. It is also commonly implicated in the type B gastritis. This organism colonizes the stomach for an extended period and causes a low grade inflammatory process, leading to superficial gastritis.
Campylobacter rectus causes periodontal disease, and is implicated in root canal infections and Crohn’s disease.

Question 13

Campylobacter fetus ssp fetus:

1 Is microaerophilic
2 Is urease positive
3 Grows at 42° C
4 Is catalase negative

Answer 13

Is microaerophilic

Growth of Campylobacter fetus ssp fetus is suppressed at 42° C. Additional characteristics of this microbe are as follows:
Microaerophilic curved gram negative rod
Non fermentative
Urease negative
Catalase positive
Resistant to Nalidixic acid
Sensitive to cephalothin
Associated with bacteremia in immunocompromised patients

Question 14

Urea breath test” is recommended for monitoring the therapy for

1 Vibrio cholerae
2 Campylobacter jejuni
3 Helicobacter pylori
4 Salmonella paratyphi

Answer 14

Helicobacter pylori

Helicobacter pylori produces urease and “urea breath test” detects the urease activity of the organism. 14C-labeled urea drink is given to the patient. 14CO2 is released when urea is degraded in the presence of urease produced by Helicobacter pylori. This 14CO2 can be detected in the exhaled breath by a scintillation counter.
Christensen’s urea medium can be inoculated with tissue sample and incubated at 37° C for 2 hours to test for presence of urease. In presence of Helicobacter pylori the color changes rapidly to indicate presence of urease.

Question 15

A stool specimen collected from a patient with gastroenteritis was cultured on skirrow medium. A gram negative curved rod was isolated from the colonies grown on the culture incubated at 42° C under microaerophilic conditions. See the attached chart. Given the additional biochemical reactions, identify the most probable etiological agent isolated.

1 Campylobacter jejuni ssp jejuni

2 Campylobacter curvus

3 Campylobacter fetus ssp fetus

4 Helicobacter fennelliae

5 Helicobacter pylori

Answer 15

Campylobacter jejuni ssp jejuni

All the organisms given in the choice are oxidase positive gram negative curved rods. Campylobacter jejuni ssp jejuni is the only organism among the given list which hydrolyzes hippurate.
Following are the distinguishing characteristics of the other organism:
Campylobacter curvus is negative for catalse
Growth of Campylobacter fetus ssp fetus is inhibited at 42° C
Helicobacter fennelliae does not grow at 42° C and can not reduce nitrate to nitrite
Helicobacter pylori is positive for urease

Question 16

The characteristics of Campylobacter jejuni ssp doylei include

1 Positive for nitrate reduction grows at 25° C as well as 42° C
2 Produces urease
3 Positive for nitrate reduction
4 Sensitive to nalidixic acid

Answer 16

Sensitive to nalidixic acid

Campylobacter jejuni ssp doylei does not grow at 25° C or 42° C. The characteristics of Campylobacter jejuni ssp doylei are summarized in the table below.

Biochemical Tests Results
Nitrate Reduction -
Urease -
H2S Production -
Susceptibility to Nalidixic Acid S
Susceptibility to Cephalothin S

Question 17

Which of the following gram-negative rods are found in sea water and are the common cause of toxigenic water-loss diarrhea? These bacteria are highly motile with a single polar flagella.

1 Vibrio cholerae
2 Proteus mirabilis
3 Shigella flexneri
4 Escherichia coli

Answer 17

Vibrio cholerae

Vibrio cholerae is the causative organism of cholera, a very serious epidemic diarrhea. The bacteria produces an enterotoxin, called the “cholera toxin.” This product induces large-scale transport of sodium, potassium, chloride, and bicarbonate along with water from the intestinal epithelium. Epidemics result directly from contaminated water supplies and are a serious problem in poorly developed areas.
Proteus mirabilis, Shigella flexneri, and Escherichia coli are all members of the Enterobacteriaceae group but do not cause epidemic diarrhea.

Question 18

Which of the following gram-negative rods are found in seawater and are therefore referred to as halophilic? The bacteria are commonly associated with acute gastrointestinal illness following the ingestion of raw fish or incompletely cooked shellfish. The disease has an incubation period of 24-48 hours and is self-limiting

1 Vibrio parahaemolyticus
2 Clostridium botulinum
3 Escherichia coli
4 Proteus mirabilis

Answer 18

Vibrio parahaemolyticus

Vibrio parahaemolyticus is a gram-negative rod found in seawater along the coast of every inhabited continent. It is commonly present on seafood, and infection may result if shellfish or fish are not completely cooked or are eaten raw. This process has a 24-48 hour incubation time and results in abdominal cramps, vomiting, and watery diarrhea. The infection is self-limiting and is not influenced by antibiotics. Clostridium botulinum, Escherichia coli, and Proteus mirabilis are not generally associated with sea water and are not halophilic.

Question 19

6 hours after eating raw fish and other seafood at a Japanese restaurant, a couple developed nausea and vomiting, watery diarrhea, abdominal cramps, and fever. What organism is likely involved in the patients’ condition?

1 Salmonella enteritidis
2 Bacillus cereus
3 Clostridium perfringens
4 Staphylococcus aureus
5 Vibrio parahaemolyticus

Answer 19

Vibrio parahaemolyticus

Vibrio parahaemolyticus are a marine organism transmitted by contaminated seafood, especially when raw fish is eaten. The clinical picture varies from mild to quite severe watery diarrhea, nausea and vomiting, abdominal cramps, and fever. The illness is self-limited, lasting about 3 days.
Bacillus cereus cause two syndromes: one involves a short incubation period with nausea and vomiting and is similar to staphylococcal food poisoning; the other involves a long incubation period (18 hours) with watery non-bloody diarrhea and resembles clostridial gastroenteritis.
Clostridium perfringens cause food poisoning with an 8- to 16-hour incubation period. It is characterized by watery diarrhea with cramps and little vomiting. It resolves in 24 hours.
Staphylococcus aureus cause food poisoning characterized by vomiting being more prominent than diarrhea. The disease is due to ingestion of enterotoxin, which is performed in foods and hence has a short incubation period (1-8 hours).
Salmonella enteritidis cause enterocolitis after an incubation period of 6-48 hours. The disease begins with nausea and vomiting and then progresses to abdominal pain and diarrhea, which can vary from mild to severe and present with or without blood. Usually, the disease lasts a few days and is self-limited.
Bacterial diarrheal diseases transmitted by foods:
Bacterium Typical food Disease
Gram-positive cocci
Staphylococcus aureus Custard-filled pastries; potato/egg/tuna salad Food poisoning, especially vomiting
Gram-positive rods
Bacillus cereus Reheated rice Diarrhea
Clostridium perfringens Cooked meat, stew, gravy Diarrhea
Gram-negative rods
Escherichia coli Various foods and water Diarrhea
Escherichia coli (O157:H7 strain) Undercooked meat Hemorrhagic colitis
Salmonella enteritidis Poultry, meats, and eggs Diarrhea
Shigella species Various foods and water Diarrhea (dysentery)
Vibrio cholerae Various foods, e.g. seafood, and water Diarrhea
Vibrio parahaemolyticus Seafood Diarrhea
Campylobacter jejuni Various foods Diarrhea
Yersinia enterocolitica Various foods Diarrhea

Question 20

Case
A 45-year-old Asian American presents with symptoms of gastritis. The physician orders a noninvasive breath test in order to help elucidate the possible cause of these symptoms.

This test relies on a bacteria’s production of which enzyme?

1 Peptidase
2 Tryptase
3 Oxidase
4 Urease
5 Catalase

Answer 20

Urease

Helicobacter pylori is the most common cause of gastritis. Production of large amounts of urease is an important characteristic of this organism, and the enzyme contributes to its virulence. Urease production is also the cornerstone of the “urea breath test” used by clinicians to noninvasively diagnose H. pylori infection. In this test, the patient ingests radiolabeled urea. In the presence of urease, the urea is broken down into radiolabeled carbon, which can be detected in the breath.
Peptidase is an enzyme that helps break down protein into amino acids.
Tryptase is an enzyme present in mast cells.
Oxidase is an enzyme possessed by some bacteria that catalyzes the oxidation of cytochrome c.
Catalase is an enzyme that causes the metabolism of hydrogen peroxide to oxygen and water. It is used to help identify bacteria. For example, staphylococci are catalase-positive while streptococci are catalase-negative.