Microbiology 8

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  1. What is the most common cause  of infectious diarrhoes in US?
    Campylobacter is more common than Salmonella plus Shigella.
  2. What are the important features of C. jejuni?
    • - Gram negative rods
    • - Comma shaped, Motile with single polar flagella (darting or tumbling motility) 
    • - Non sporing 
    • - Culture of C. jejuni is best under microaerophilic condition with O2 tension lowered to 5% and carbon dioxide raised to 10%. Incubation of primary plates should be at 42oC. [AI 05]
  3. What is the major complication of campylobacter?
    • GBS
    • - Antibody made against Campylobacter cross react with the neural tissue.
  4. Which of the following is true regarding Vibrio [UP 96]
    A) Produce medusa head colony 
    B) It is oxidase positive 
    C) It ferments glucose only 
    D) It has peritrichous flagella
    B) It is oxidase positive

    Vibrio cholera produces acid without gas from glucose, sucrose, maltose and mannitol.
    It gives positive oxidase and cholera red reaction. They liquify gelatin, produce H2S but do not hydrolyze urea.
    Vibrio cholerae possess a single polar flagellum and exhibit highly active motility.
    (this multiple choice question has been scrambled)
  5. How can we classify Vibrio cholera?
    • Vibrio cholera can be classified as 
    • a) O1 V. cholera (agglutinate on O1 antiserum) 
    • - Classical 
    • - El Tor 

    • b) Non O1 V. cholera (do not agglutinate in O1 antiserum)
    • - O139 V. cholera - cause epidemic/pandemic
    • - Non O1/Non O139 V. cholera - is not known to cause epidemic/pandemic
  6. What are types of O1 V. cholera?
    Classic and El Tor.

    • Vibrio El Tor resembles Classic vibrio cholera in biochemical reactions, morphology and antigenic structure.  [AI 92]
    • El Tor vibrios were first found in Indonesia. [BHU 02]
  7. How do you differentiate El Tor vibrio from Classical vibrio? [AI 97]
    Cholera is mostly caused by El Tor biotype which are distinguished from the classical  vibrios by the following tests - 

    • a) El Tor vibrios agglutinate chicken and sheep RBC
    • b) El Tor vibrios are resistant to classic phage IV 
    • c) Eltor vibrios are more resistant than the classic vibios including polymyxin B-50 unit disc, and 
    • d) The VP reaction and hemolytic test do not give consistent results.
    • e) Higher incidence of mild and asymptomatic infection [SGPGI 03] - characteristic picture of rice water stools and other signs of classical cholera may not be seen. 
    • f) Secondary attack rate is less
    • g) Higher occurrence of chronic carriers. 
    • h) Longer survival in extraintestinal environment

    [in comparision to classical cholera, El tor are Hemolysis, Chick embryo agglutination and VP reaction +ve, and Polymyxin B and group IV (4) phage sensitivity are -ve - @ Elton was HCV +ve, but p4 -ve]
  8. What are important features of V. cholera O139? [AI 07]
    • V. cholera O139 biotype was first isolated from a cholera outbreak in Chennai as a novel strain of V. cholera.
    • Clinical manifestations and epidemiological features of the disease caused by V. cholera 0139 are indistinguishable from those of the O1 cholera
    • It does not produce O1 lipopolysaccharide
    • V. cholera O139 is very similar to V. cholera O1 El Tor biotype but there are some differences. 
    • It is capsulated. El Tor strains are non capsulated.
  9. Classify Vibrios based upon salt tolerance.
    • Non halophilic vibrios 
    • - V. cholerae [AI 05] 
    • - V. mimicus 

    • Halophilic vibrios (these vibrios donot grow in salt media without added salt) 
    • - V. parahaemolyticus 
    • - V. vunlificus 
    • - V. mimicus
  10. What are the culture media for Vibrio cholera?
    • Selective media 
    • Thiosulphate citrate bile salt sucrose (TCBS) media
    • - Alkaline bile salt agar 

    • Transport media
    • - Venkataraman Ramakrishnan (VR) medium [AIIMS 91]
    • - Cary Blair medium 
    • - Alkaline peptone water [AI 99]
  11. What are important biochemical reactions with Vibrio cholera?
    • - Catalase positive, Oxidase positive 
    • - Gives cholera red reaction - this is contributed by two properties, Indole positive and reduction of nitrate
    • - Elaborate certain enzymes, like neuramidinase
  12. Which of the following is false regarding Vibrio cholera [AI 94]
    A) Gram negative organism 
    B) Transported in acidic medium
    C) Aerobic organism 
    D) Ferments glucose 
    B) Transported in acidic medium

    Vibrios are gram-negative curved rods which are actively motile. Mobility is of darting type. [TN 97]  Human beings are the only known reservoir of cholera infection. They are strongly aerobic organisms which ferment carbohydrates producing acid. They ferment glucose, mannitol, maltose, mannose and sucrose but not inositol.
    (this multiple choice question has been scrambled)
  13. Oscillatory movement is found in [IOM 10]
    A) Salmonella typhi 
    B) V. cholera 
    C) Treponema pallidum
    D) Trichomonas vaginalis 
    B) V. cholera 

    (this multiple choice question has been scrambled)
  14. Diseases caused by non-cholera vibrios.
    • A. V. parahemolyticus
    • - Gastroenteritis
    • - Wound infection
    • B. Non O-1/O139 V. cholera
    • - Gastroenteritis
    • - Wound infection
    • - Otitis media
    • C. V. vulnificus
    • - Sepsis
    • - Secondary cellulitis
    • - Wound infection
    • D. V. alginolyticus
    • - Wound infection
    • - Cellulitis
    • - Otitis media
    • - Sepsis
  15. Name important diseases caused by Vibrio vulnificus?
    • It causes 2 types of illness:
    • - Wound infection following contact of open wounds in seawater. [AIIMS 01]  
    • - Illness in compromised hosts particularly those with liver disease.
  16. Which of the following "vibrios" is most commonly associated with ear infection: [AI 12]
    A. V. alginolyticus
    B. V. fluvialis
    C. V. parahemolyticus
    D. V. Vulnifcus
    A. V. alginolyticus

    V. alginolyticus is an opportunistic pathogen (halophilic vibrio) that is primarily associated with wound and ear infections, and occasionally eye infections.
    (this multiple choice question has been scrambled)
  17. Endotoxin of which gram negative bacteria have no part in pathogenesis of disease: [AI 12]
    A. Vibrio cholera
    B. Klebsiella
    C. Pseudomonas aerugonesa
    D. E. coli
    A. Vibrio cholera

    Cholera is primarily caused by production of a powerful exotoxin called cholera enterotoxin.
    Cholera endotoxin (Lipopolysaccharide O antigen) has no role in pathogenesis of cholera, but is responsible for immunity induced by killed vaccine.
    (this multiple choice question has been scrambled)
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Microbiology 8
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