1. Microbiology Department KUMS
Vibrio, Aeromonas, Plesiomonas
Microbiology Department KUMS
Dr. Mohajeri

2. Vibrio cholerae

3. Vibrio, Aeromonas, Plesiomonas, Campylobacter, and Helicobacter species are G-ve rods
The vibrios are found in marine and surface waters.
Aeromonas is found predominantly in fresh water and occasionally in cold-blooded animals.
Plesiomonas exists in both cold-blooded and warm-blooded animals.

4. Vibrio cholerae produces an enterotoxin that causes cholera, a profuse watery diarrhea that can rapidly lead to dehydration and death.
Less commonly, Aeromonas and, rarely, Plesiomonas have been associated with diarrheal disease in humans.

5. The Vibrios
are among the most common bacteria in surface waters worldwide.
are curved aerobic rods and are motile, possessing a polar flagellum.
V. cholerae serogroups O1 and O139 cause cholera in humans.
other vibrios may cause sepsis or enteritis.

7. Vibrio cholerae
- transmission in water and the development of sanitary water systems
Morphology & Identification
V. cholerae is a comma-shaped
is actively motile by a polar flagellum

8. Culture
V. cholerae grows well on thiosulfate-citrate-bile-sucrose (TCBS) agar, on which it produces yellow colonies.

9. Vibrios are oxidase-positive, which differentiates them from enteric G-ve bacteria.
Vibrios grow at a very high pH (8.5–9.5) and are rapidly killed by acid.
direct cultures of stool on selective media such as TCBS, and enrichment cultures in alkaline peptone water (APW) are appropriate.

10. Growth Characteristics
V. cholerae regularly ferments sucrose and mannose but not arabinose.
A positive oxidase test is a key step in the preliminary identification.
Vibrio species are susceptible to the compound O/129 (2,4-diamino-6,7-diisopropylpteridine phosphate), which differentiates them from Aeromonas species, which are resistant to O/129.
Most vibrio species are halotolerant, and NaCl often stimulates their growth.

11. Another difference between vibrios and aeromonas is that vibrios grow on media containing 6% NaCl, whereas aeromonas does not.

12. Antigenic Structure & Biologic Classification
have a single heat-labile flagellar H antigen
Antibodies to the H antigen are probably not involved in the protection of susceptible hosts.
V. cholerae has O lipopolysaccharides that confer serologic specificity.
There are at least 139 O antigen groups.
V. cholerae strains of O group 1 and O group 139 cause classic cholera.

13. occasionally, non-O1/non-O139 V. cholerae causes cholera-like disease.
Antibodies to the O antigens tend to protect laboratory animals against infections with V. cholerae.
The V. cholerae serogroup O1 antigen has determinants that make possible further typing; the main serotypes are Ogawa and Inaba.
Two biotypes of epidemic V. cholerae have been defined, classic and El Tor.

14. The El Tor biotype:
- produces a hemolysin
- VP +
- resistant to polymyxin B
V. cholerae O139 (Bengal) is very similar to V. cholerae O1 El Tor biotype.
V. cholerae O139 does not produce the O1 LPS.
V. cholerae O139 makes a polysaccharide capsule like other non-O1 V. cholerae strains, while V. cholerae O1 does not make a capsule.

15. V. cholerae Enterotoxin
produce a heat-labile enterotoxin with a molecular weight of about 84 kD, consisting of subunits A (MW 28 kD) and B.
Ganglioside GM1 serves as the mucosal receptor for subunit B, which promotes entry of subunit A into the cell → Activation of subunit A1
→ increase intracellular cAMP
→ hypersecretion of water and electrolytes
There is increased sodium-dependent chloride secretion, and absorption of sodium and chloride is inhibited.

16. Diarrhea occurs—as much as 20–30 L/d—with resulting dehydration, shock, acidosis, and death.
The genes for V. cholerae enterotoxin are on the bacterial chromosome.
Cholera enterotoxin is antigenically related to LT of Escherichia coli and can stimulate the production of neutralizing antibodies.

18. Action of Cholera Toxin

19. Pathogenesis & Pathology
V. cholerae is pathogenic only for humans.
A person with normal gastric acidity may have to ingest ≥ 1010 to become infected when the vehicle is water, because the organisms are susceptible to acid.
When the vehicle is food, as few as 102–104 organisms are necessary because of the buffering capacity of food.

20. Cholera is not an invasive infection.
The organisms do not reach the bloodstream but remain within the intestinal tract.
Virulent V. cholerae organisms attach to the microvilli of the brush border of epithelial cells → multiply and liberate toxin, mucinases and endotoxin

21. Clinical Findings
About 60% of infections with classic V. cholerae are asymptomatic
about 75% of infections with the El Tor biotype
incubation period is 1–4 days
Stools, which resemble "rice water"
The mortality rate without treatment is between 25-50%.
The El Tor biotype tends to cause milder disease than the classic biotype.

22. Diagnostic Laboratory Tests
Specimens for culture consist of mucus flecks from stools.
Dark-field or phase contrast microscopy may show the rapidly motile vibrios.
Growth is rapid in peptone agar, on blood agar with a pH near 9.0, or on TCBS agar.
For enrichment, a few drops of stool can be incubated for 6–8 hours in taurocholate-peptone broth (pH 8.0–9.0); organisms from this culture can be stained or subcultured.

23. slide agglutination tests using anti-O group 1 antisera
biochemical reaction patterns

24. Immunity
Gastric acid provides some protection against cholera vibrios.
In experimental animals, specific IgA (s IgA) antibodies occur in the lumen of the intestine.
Similar antibodies in serum develop after infection but last only a few months.
The presence of antitoxin antibodies has not been associated with protection.

25. Treatment
water and electrolyte replacement
Many antimicrobial agents are effective against V. cholerae - Oral tetracycline
In some endemic areas, tetracycline resistance of V. cholerae has emerged, carried by transmissible plasmids.

26. Epidemiology, Prevention, & Control
Six pandemics, caused most likely by V. cholerae O1 of the classic biotype.
The seventh pandemic began in 1961 in the Celebes Islands, Indonesia, with spread to Asia, the Middle East, and Africa. This pandemic has been caused by V. cholerae biotype El Tor.
The serotype O139 strain to be the eighth pandemic that began in the Indian subcontinent in 1992, with spread to Asia.

27. In many instances, only 1–5% of exposed susceptible persons develop disease.
The carrier state seldom exceeds 3–4 weeks, and true chronic carriers are rare.
Vibrios survive in water for up to 3 weeks.
Patients should be isolated, their excreta disinfected, and contacts followed up.

28. Vibrio parahaemolyticus & Other Vibrios
V. parahaemolyticus is a halophilic bacterium that causes acute gastroenteritis following ingestion of contaminated seafood such as raw fish or shellfish.
incubation period: 12–24 hours
watery to bloody diarrhea occur
it does grow well on blood agar and TCBS (green colonies).

29. V. vulnificus can cause severe wound infections, bacteremia, and probably gastroenteritis.
Bacteremia with no focus of infection occurs in persons who have eaten infected oysters and who have alcoholism or liver disease.
Wounds may become infected in normal or immunocompromised persons who are in contact with water where the bacterium is present.
Infection often proceeds rapidly, with development of severe disease.
About 50% of the patients with bacteremia die.

30. the rapid progression of the infection
Diagnosis is by culturing the organism on standard laboratory media; TCBS is the preferred medium for stool cultures, where most strains produce blue-green (sucrose-negative) colonies.
Several other vibrios also cause disease in humans:
- V. mimicus causes diarrhea after ingestion of uncooked seafood, particularly raw oysters.
- V. hollisae and V. fluvialis also cause diarrhea.

31. - V. alginolyticus causes eye, ear, or wound
- V. alginolyticus causes eye, ear, or wound infection after exposure to seawater.
- V. damsela also causes wound infections

32. Aeromonas
The genus has been placed in the new family Aeromonadaceae from the family Vibrionaceae.
Three groups are of primary clinical importance in human infections:
1) A. hydrophila complex
2) A. caviae complex
3) A. veronii biovar sobria.
are motile, produce large zones of hemolysis on blood agar.
are distinguished from the enteric G-ve rods by finding a positive oxidase reaction.

33. Aeromonas species are differentiated from vibrios by showing resistance to compound O/129 and lack of growth on media containing 6% NaCl.
Aeromonads produce hemolysins.
Some strains produce an enterotoxin, Cytotoxins.
Koch's postulates have not been satisfied, largely because there is no suitable animal model that reproduces human aeromonas-associated diarrhea.
Aeromonas strains are susceptible to tetracyclines, aminoglycosides, and cephalosporins.

34. Plesiomonas
P. shigelloides is a G-ve rod with polar flagella.
is most common in tropical and subtropical areas
isolated from freshwater fish and many animals
Most isolates from humans have been from stool cultures of patients with diarrhea
Some plesiomonas strains share antigens with Shigella sonnei, and cross-reactions with shigella antisera occur.

35. Plesiomonas is oxidase-positive and shigellae are not.
Plesiomonas is positive for DNase.

37. التور : در اپیدمی التور در زائرین عربستان
ویرولانس فاکتورها:
1- اندوتوکسین
2- اگزوتوکسین (انتروتوکسین)
3- همولایزین
4- موسیناز (پوسته پوسته شدن دیواره روده)
5- تاژه
6- پیلی
7- نورآمینیداز

38. انتروتوکسین دارای دو قطعه است:
A (A1, A2) ← فعال نمودن آدنیلات سیکلاز ← cAMP↑
B (5 قطعه) ← اتصال به گانگلیوزید GM1
ویبریو کلرا دارای Ag- OH است.
دو نوع ویبریو کلرا مولد وبا:
سروگروپ O1 (با آنتی سرم O1 آگلوتینه می شود)← اپیدمیک
NAG (Non Agglutination Group) (با .... نمی شود) ← اندمیک

39. سروگروپ O1 بر اساس آنتی ژن O دارای انواع سروتیپ (بیوتیپ) های زیر است :
- اینابا (Inaba) ← حاوی آنتی ژن AC>> در هندوستان و برمه
- اوگاوا (Ogawa) ← حاوی آنتی ژن AB>> در هندوستان و برمه
- هایکوجیما (Hikojima) ← حاوی آنتی ژن ABC >> در چین
هر بیوتیپ ممکن است فنوتیپ التور یا کلاسیک داشته باشد.
ویبریو کلرا برخلاف سالمونلا و شیگلا، در دیواره روده فرو نمی رود و زخم ایجاد نمی کند.
اسید معده باکتری را می کشد. افراد هیپوکلرهیدریا مستعدند و با 100 تا 1000 باکتری آلوده می شوند.

40. علایم بیماری وبا:
دهیدراتاسیون
اسیدوز متابولیک
کاهش ادرار (anuria)
کاهش فشار خون
شوک
اسهال آب برنجی (rice water) ← از دست دادن روزانه تا 20 لیتر آب
در موارد درمان نشده تا 60-50% احتمال مرگ وجود دارد.
درمان از روی علائم صورت می گیرد و یک فوریت پزشکی است. (الکترولیت و تتراسایکلین)

41. روی محیط TCBS کلنی زرد ← ویبریو کلرا
انسان ناقل وبا، حدود هزار باکتری در هر سی سی مدفوع دفع می کند.
بیمار وبایی، حدود صد هزار باکتری در هر سی سی مدفوع دفع می کند.
این باکتری در صفرا باقی می ماند (مثل سالمونلا)
در سال 1992، سروگروپ Bengal= O139 در بنگلادش یافت شد که جانشین التور شده است. این سروگروپ خطرناک و دارای کپسول پلی ساکاریدی است. نوعی Non-O1 محسوب می شود.

43. ویبریو پاراهمولیتیکوس
- مسمومیت غذایی در نتیجه خوردن محصولات دریایی و صدف، سپتی سمی و مننژیت
ویبریو ولنیفیکوس
- زخم و عفونت های سیستمیک
- برخلاف ویبریو کلرا تهاجمی است