1. Slightly Curved Bacilli

2. Vibrio
Members of this genus share many characteristics with enteric bacteria such as Escherichia and Salmonella
Found in water environments worldwide (among the most common bacteria in surface waters).
Vibrio cholerae is the most common species to infect humans
Vibrio cholerae serogroup O1 (Ogawa & Inaba serotypes)
It has 2 biotypes: classical and ElTor
Causes cholera
Humans become infected with V. cholerae by ingesting contaminated food and water
Found most often in communities with poor sewage and water treatment
There are 100 O serogroups. Many vibrios share a single heat labile flagellar H Ag

7. Vibrio They are curved aerobic rods motile by a polar flagellum
A large inoculum (108) is required to cause disease because the bacteria are susceptible to the acidic stomach environment
Cholera toxin (enterotoxin) is the most important virulence factor of V. cholerae
Lemon drops during epidemics

8. GM1

9. Cholera Pathology
Some infections are asymptomatic or cause mild diarrhea
Incubation period is 1-4 days
Can cause severe disease resulting in abrupt watery diarrhea and vomiting (20-30L/day)
“Rice-water stool” is characteristic
Results in severe fluid and electrolyte loss, dehydration, shock, acidosis, anuria
Can progress to coma and death
Mortality rate in untreated cases is 60%

10. Diagnosis, Treatment, and Prevention
Usually based on the characteristic diarrhea
Selective medium : TCBS (thiosulphate, citrate, bile salt, sucrose agar) pH
Vibrio cholerae is a sucrose fermenter
Vibrio parahemolyticus is a non-sucrose fermenter

12. Treatment Treatment Prevention Fluid and electrolyte replacement
Antimicrobial drugs are not as important because they are lost in the watery stool
Tetracyclines reduce stool output and shorten the period of excretion of vibrios
Resistance via plasmids is developing
An attack is followed by immunity of unknown duration
Prevention
Adequate sewage and water treatment can limit the spread of V. cholerae

13. Epidemiology
Epidemics caused by classical biotype through the early 1960s
El Tor biotype prevailed in the late 1960s
It is endemic in Southeast Asia
Ships have carried it to ports all around the world in ballast water
It is spread by person to person contact, water, food, and flies
There are seldom carriers

17. Other Diseases of Vibrio
Vibrio parahaemolyticus
It is halophilic and does not ferment sucrose
Results from ingestion of shellfish or raw fish
Incubation period is hours
Causes cholera-like gastroenteritis
Vibrio vulnificus
Causes septicemia following consumption of contaminated shellfish
Infections can result from washing wounds with contaminated seawater (skin lesions)

18. Campylobacter Gram negative rods with comma, S or “gull wings” shapes
Motile with a single polar flagellum, non-sporing.
One of the most common causes of gastroenteritis in the developed world
Many animals serve as reservoirs for the bacteria where they cause sepsis, abortion or enteritis
Humans become infected by consuming contaminated food, milk, or water
Infections produce bloody and frequent diarrhea that is self-limiting
Spread of the bacteria can be reduced by proper food handling and preparation

19. Campylobacter jejuni A common human pathogen causing enteritis
Poultry is the most common source of infection
The source of infection may be food, drink, contact with infected animals or humans and their excreta
Organisms multiply in the small intestine, invade the epithelium and produce inflammation causing appearance of RBCs and WBCs in stools resembling shigellosis.

22. Culture
Selective medium is Skirrow’s medium (VPT). Colonies are colourless or grey (tear drop) or watery or round
Incubation atmosphere: microaerophilic with reduced O2 (5%) and added CO2 (10%)
Incubation temperature 42-43ºC
Oxidase and catalase positive

23. Treatment Self limited
Erythromycin: shortens the duration of fecal shedding of bacteria

24. Other Campylobacters Other species include Campylobacter fetus
(cattle & sheep), Campylobacter coli (pigs)
and Campylobacter lari (animals and birds).
Campylobacter fetus can cause systemic
infections in immunocompromised patients.

25. Helicobacter pylori
Was originally placed with campylobacters but it has sheathed flagella and is urease positive
Slightly helical, Gram-negative highly motile bacterium that colonizes the stomach of its hosts
It is present on the gastric mucosa of 20% of persons under 20 years and increases up to 80% in adults in developing countries
The natural history of infection is not well known but it is likely that person to person transmission and common source infections occur
Once acquired, infection persists for years or for life.

29. Virulence factors
H.pylori produces numerous virulence factors that enable it to colonize the stomach
It is a strong producer of urease
Flagella that enable the pathogen to burrow through the mucous lining the stomach
Adhesins facilitate binding to gastric cells
H. pylori also produces a protease that modifies the gastric mucous and further reduces the ability of acid to diffuse through the mucous.
Toxins and lipopolysaccharide
A toxin that inhibits acid production by stomach cells

30. Pathogenesis Associated with antral gastritis
Important in Peptic ulcer (duodenal)
Warren-MarshalL & Koch’s postulates
Optimum pH 6-7, killed at low pH
Gastric mucous is relatively impermeable to acid and has a strong buffering capacity.
On the lumen side of the mucous, pH is low 1-2
While on the epithelial side the pH is about 7.4
H. pylori is found deep in the mucous layer near the epithelial surface

31. Pathogenesis (cont.)
H. pylori also produces a potent urease which yields ammonia and further buffers the acid.
H. pylori is quite motile even in mucous and is able to find its way to the epithelial surface
H. pylori invades the epithelial cell surface to a limited degree
Toxins and lipopolysaccharide may damage the cells also
IgM, IgG & IgA are produced and persist in chronic infections

32. Phagocytosed bacteria survive in leukocytes by catalase and superoxide dismutase

33. Diagnosis, Treatment, and Prevention
Mainly histologically (biopsy)
Presence of H. pylori can be demonstrated by a positive urease test
Biochemical tests provide a definitive identification
Treatment
Antimicrobial drugs are used in combination with drugs that inhibit acid production (triple therapy)
Prevention
Prevention is difficult because the exact mode of transmission is unknown

34.                            A gastric MALT-lymphoma