Vibrio, Camplyobacter, & Helicobacter Flashcards
Describe the characteristics of Vibrio Cholera.
Gram -
Curved rod
Facultive anaerobe
Has a single, polar flagellum
Chemoorganotrophic
Optimal growth is 20-30 degrees
What does chemoorganotrophic mean?
These are organisms that organisms which oxidize the chemical bonds in organic compounds as their energy source
How are different subsets of cholera divided?
Biotype (Biovar) - Different strains of the same bacterial species distinguished by a group of phenotypic or genetic traits.
Serogroup - Bacteria of the same species with different antigenic determinants on the cell surface.
V. cholera has more than 150 different serogroups but only two cause epidemic disease.
How many chromosomes does V. cholera have?
Two circular chromosomes
Chromosome 1 is for larger cell functions / housekeeping
Chromosome 2 is smaller and carries integron island genes a/ antibiotic resistance genes
How is Cholera spread?
Fecal-oral route
What is the pathogenesis of V. cholera?
Cholera disease begins with the ingestion of contaminated water or food.
Those bacteria that survive the acidic conditions in the stomach are able to colonize the small intestine.
What is responsible for the severe diarrhea that is characteristic of Cholera disease?
Cholera toxin (CT)
What are the characteristics of Cholera Toxin?
Cholera toxin is a proteinaceous enterotoxin that is secreted by V. cholera.
Describe the make up of Cholera Toxin?
Cholera toxin is made up of five (5) B subunits and Two (2) A subunits
How does Cholera Toxin work?
The five B subunits bind to GM1 gangliosides on the intestinal cell membrane.
The two A subunits ribosylate the ADP on the GTP=binding protein.
This ribosylation activates membrane-associated adenylate cyclase which converts ATP to cAMP.
Elevated levels cAMP induces the secretion of NaCL and HCO3 while inhibiting the absorption of these compounds.
This change in ion concentration in the lumen of the intestine leads to the secretion of large amounts of H2O and electrolytes.
This ten leads to the watery diarrhea that is characteristic of Cholera.
This ultimately leads to death by dehydration if these imbalances are not corrected.
What antigens are present in V. cholera?
O and H antigens but ONLY O antigens are useful in distinguishing pathogenic V. cholera species.
What are the two biotypes (subdivisions) of the species of V. cholera?
There are two biotypes: Classic and El Tor
What are outbreaks of Cholera due to?
Undercooked, contaminated seafood and contaminated water.
How can V. cholera be identified?
V. cholera grows on standard media such as blood agar and MacConkey agars.
Thiosulfate-citrate-bile salt & sucrose media can also help with the isolation of V. cholera
Is V. cholera oxidase positive or negative?
V. cholera is oxidase positive.
How is Cholera treated?
Fluid and electrolyte replacement
Antibiotics are of limited value because they are flushed out with the diarrhea
How is Cholera diagnosed?
Cholera is usually diagnosed based on the characteristics of the diarrhea.
What are the characteristics of Campylobacter and Helicobacter?
These are Gram - and have a helical / spiral morphology. They also tend to be pleomorphic (Become coccoid when exposed to O2 or prolonged culture time)
The shape of the bacteria help to facilitate penetration and colonization of mucosal environments
They are Microaerophilic and do not ferment or oxidize carbohydrates.
Describe the history and characteristics of Campylobacter.
First isolated as Vibrio fetus in 1909 from spontaneously aborted livestock
Was not officially recognized as Campylobacter enteritis until 1970. Isolated from feces.
This is the most common form of acute, infectious diarrhea in developed nations. Has a higher incidence than Salmonella and Shigella combined.
Describe the morphology and physiology of Campylobacter.
Small and thin (0.2 - 0.5 um X 0.5 - 5.0 um)
Helical (Spiral or curved)
Have a typical ‘gull-winged’ appearance with a typical Gram - cell wall
They have a tendency to form coccoid & elongated shapes when in prolonged cell culture or exposed to O2
Have a distinctive, darting motility due to long, sheathed polar flagellum
Microaerophillic & capnophillic (5% O2, 10% CO2, & 85% N2)
Thermophilic (42 - 43 o C)- This happens to be the body temp. of the natural avian reservoir
What are the three most important Campylobacter species that are associated with human diseases?
C. jejuni - The reservoir are poultry, pigs, cattle, dogs, cats, birds, minks, rabbits, insects and it causes gastroenteritis, septicemia, meningitis, spontaneous abortion, and Guillain-Barre syndrome.
C. coli - Reservoir is pigs, poultry, cattle, sheep and birds. Causes all of the diseases that C. jejuni causes except for Guillain-Barre.
C. fetus - The reservoir is cattle and sheep. Causes all of the same diseases as C. jejuni except for Guillain-Barre.
What is Guillain-Barre Syndrome (GBS)?
This is a low-incidence, self-limited autoimmune disease that is associated with Campylobacter jejuni infection.
How does GBS start?
Specific bacterial O-antigens cross react with surface components of peripheral nerves. (Antigenic mimicry)
The immune system responds to this cross-reaction.
This causes an acute inflammatory demylenating neuropathy in 85% of the cases due to cross reaction with Schwann cells or myelin.
Discuss the epidemiology of Campylobacteriosis.
Zoonotic infection
Birds are the reservoirs
Causes spontaneous abortions in cattle, sheep, and swine but usually asymptomatic in animals.
Humans acquire this via teh ingestion of contaminated food, esp. chicken, milk, or water. Fecal-oral transmission occurs as well.
Infectious dose is reduced by foods that neutralize gastric acids (Milk).
Contaminated polutry accounts for more than 1/2 of cases in developed countries.
Peak incidence occurs in children below 1 year of age and young adults 15-24 years of age.
In developing nations, this disease is hyperendemic with symptomatic disease occuring in young children and persistent, asymptomatic carriage in adults.
What are the virulence factors associated with Campylobacter?
Endotoxin
Flagellum - Motility
Adhesins - Mediate attachment to mucosa
Invasins
S-layer protein in C. fetus
GBS is associated with C. jejuni serogroup O19
Extracellular virulence factors include enterotoxins and cytopathic toxins
Discuss the pathogenesis and immune response to Camplyobacter.
Infectious dose and host immunity determine whether gastroenteric disease develops.
Some people infected with as few as 500 organisms while others need 106 colony forming units.
Pathogenesis is not fully understood
No good animal model exists
Damage to mucosal surfaces of the jejunum, ileum, and colon
Inflammatory process is consistent with invasion of the organisms into the intestinal tissue
Strains that are non-motile & adhesin-lacking strains are avirulent
How are Camplyobacter species identified in a laboratory?
Examination of feces
& rectal swabs
Blood draws for C. fetus
Take care to avoid oxygen exposure
Selective isolation by filtration of stool specimen (0.45 um filter)
Enrichment broth & selective medias
Hippurate hydrolysis
Susceptibility testing (Nalidixic acid and Cephalothin)
How Camplyobacter species treated?
Gastroenteritis from Camplyobacter species is usually self-limiting
Replinish fluids and electrolytes
Antibiotics can shorten the excretion period
Controls should be directed at domesticated animals to interrupt transmission to humans
To treat Guillain-Barre Syndrome, provide supportive care but intensive care is needed for up to 33% of cases
Describe the history and taxonomy of Helicobacter.
First observed in 1983 in the stomachs of patients with type B gastritis (pylorus)
The important human pathogens are:
H pylori (Humans and no animal reservoir)
H cinaedi (Male homosexuals and rodents) - Colonize intestinal tract
H fenneliae (Male homosexuals and rodents) - Colonize intestinal tract
What makes H. pylori and important human pathogen?
H. pylori is associated with chronic gastritis.
The stomachs of many animal species are also colonized.
Urease+ (Gastric strains only)
Mucinase+
Catalase+
Highly motile
What is the morphology and physiology of Helicobacter?
Gram -
Helical 9Spiral or curved)
Cells become rod-like or coccoid on prolonged culture
Produce urease, mucinase, and catalase
H. pylori is lophotrichous with 4 to 6 sheathed flagella on one end.
Single polar flagella on H. fennellae and H. cinaedi.
What is the epidemiology of Helicobacter infection?
See family clusters
Orally transmitted person-to-person (?)
~ 20% below age 40 are infected
~50% above age 60 are infected
H. pylori is uncommon in young children
In U.S., 30% of total population is infected and about 1% per year develop duodenal ulcer
Low socioeconomic status is a risk factor for infection
Hyperendemic in developing nations; most adults are infected but have no disease due to protective immunity
Where does Helicobacter colonize?
Mucosal lining of stomach and duodenum in humans and animals
Most gastric adenocarcinomas and lymphomas are concurrent with or preceded by an infection with H. pylori
What are the virulence factors for Helicobacter?
Multiple polar, sheathed flagella
Adhesins - Hemagglutinins
Mucinase - Degrades gastric mucus and causes localized tissue damage
Urase - Converts urea to bicarbonate and ammonia; this neutralizes the local acidic environment and causes localized tissue damage
Acid-inhibitory proteins
How are Helicobacter infections treated?
Proton pump inhibitors
One or more antibiotics - Clarithromycin, amoxicillin, metronidazole
Bismuth compound
It should be noted that inadequate treatment results in the recurrence of symptoms
