Shigella Species and Antibiotic Treatment
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Questions and Answers

What is the treatment for E coli meningitis and respiratory tract infection?

  • Third-generation cephalosporins (eg ceftriaxone) (correct)
  • First-generation cephalosporins
  • Fourth-generation cephalosporins
  • Second-generation cephalosporins

    • How many species of Shigella are there?

  • Three
  • Six
  • Five
  • Four (correct)

    • What is the result of TSI K/A with Shigella?

  • K/A is not applicable to Shigella
  • Gas produced
  • Inconclusive result
  • No gas produced (correct)

    • Which Shigella species does not ferment mannitol?

    <p>S.dysenteriae</p> Signup and view all the answers

    What is the mechanism of action of Shiga toxin?

    <p>Cleaving a glycosidic bond in the 28S rRNA constituents</p> Signup and view all the answers

    What happens to the vacuoles after Shigella is phagocytosed?

    <p>They are destroyed</p> Signup and view all the answers

    How do Shigella spread laterally through epithelial cells?

    <p>By polymerization of actin filaments</p> Signup and view all the answers

    What is the mode of transmission of Shigella?

    <p>Fecal-oral</p> Signup and view all the answers

    What is the main symptom of Salmonella infection in the initial stage?

    <p>Low-grade fever and constipation</p> Signup and view all the answers

    Where do Salmonella bacteria multiply after entering the body?

    <p>Liver and spleen</p> Signup and view all the answers

    What is the main purpose of the Widal test?

    <p>To detect antibodies against Salmonella typhi</p> Signup and view all the answers

    What is the primary treatment for enteric fevers caused by Salmonella?

    <p>Use antimicrobial therapy with chloramphenicol</p> Signup and view all the answers

    What is the typical outcome for 10% of individuals infected with Salmonella?

    <p>They become short-term carriers</p> Signup and view all the answers

    What is the characteristic skin lesion seen in Salmonella infection?

    <p>Erythematous, muculopapular lesions (rose spots)</p> Signup and view all the answers

    When are blood cultures typically positive for Salmonella?

    <p>During the first week and after the second week</p> Signup and view all the answers

    What is the primary goal of treatment for Salmonella gastroenteritis?

    <p>To replace lost fluids and electrolytes</p> Signup and view all the answers

    What are adhesins also known as?

    <p>Colonization factors</p> Signup and view all the answers

    How many types of adhesins are there at least?

    <p>21</p> Signup and view all the answers

    What is the function of enterochelin?

    <p>Captures iron</p> Signup and view all the answers

    What is the leading cause of urinary tract infections?

    <p>E.coli</p> Signup and view all the answers

    What is the common cause of traveler's diarrhea?

    <p>ETEC</p> Signup and view all the answers

    What is the function of outer membrane proteins?

    <p>Helps in attachment to host cells</p> Signup and view all the answers

    What is the leading cause of neonatal meningitis?

    <p>E.coli with K1 capsular antigen</p> Signup and view all the answers

    What is the result of bacteria living on the edges of the biofilms?

    <p>Break off leading to a round of infection</p> Signup and view all the answers

    What is the characteristic of somatic O antigens in Enterobacteriaceae?

    <p>They are heat-stable polysaccharide part of the LPS.</p> Signup and view all the answers

    What is the effect of boiling on the K antigen in Enterobacteriaceae?

    <p>It destroys the K antigen and unmask O antigens.</p> Signup and view all the answers

    What is the normal habitat of Escherichia coli?

    <p>Gastrointestinal tract</p> Signup and view all the answers

    What is the association of K1 antigen in Escherichia coli?

    <p>It is associated with virulence, particularly meningitis in neonates.</p> Signup and view all the answers

    What is the characteristic of flagellar H antigens in Enterobacteriaceae?

    <p>They are heat-labile.</p> Signup and view all the answers

    What is the result of variation from smooth to rough colonial forms in Enterobacteriaceae?

    <p>It is accompanied by progressive loss of smooth O Antigen.</p> Signup and view all the answers

    What is the characteristic of the Vi antigen in Salmonella Typhi?

    <p>It is a heat-labile K antigen.</p> Signup and view all the answers

    What is the characteristic of Escherichia coli in TSI?

    <p>It is A/A + gas.</p> Signup and view all the answers

    What is a characteristic of Citrobacter?

    <p>Motility +</p> Signup and view all the answers

    Which of the following is a virulence factor of Klebsiella?

    <p>Adhesions</p> Signup and view all the answers

    What is the clinical significance of Edwardsiella tarda?

    <p>Causes GI disease in tropical and subtropical countries</p> Signup and view all the answers

    What is a characteristic of Enterobacter?

    <p>TSI, LIA, and urea give variable results</p> Signup and view all the answers

    What is a characteristic of Serratia?

    <p>Motility +</p> Signup and view all the answers

    Which of the following is a characteristic of Klebsiella?

    <p>MR-</p> Signup and view all the answers

    What is the clinical significance of Klebsiella?

    <p>Causes pneumonia, mostly in immunocompromised hosts</p> Signup and view all the answers

    What is a characteristic of Proteus, Providencia, and Morganella?

    <p>All are motile, with Proteus swarming</p> Signup and view all the answers

    Study Notes

    E. coli and Shigella

    • E. coli meningitis and respiratory tract infections require third-generation cephalosporins (e.g., ceftriaxone).
    • Shigella species:
      • Contain four species (A, B, C, and D) that differ antigenically and biochemically.
      • Biochemistry: TSI K/A with no gas, urea negative, motility negative, and all ferment mannitol except S. dysenteriae.
      • Antigenic structure: differentiated into groups (A, B, C, and D) based on O antigen serotyping; K antigens may interfere with serotyping.
      • Virulence factors: Shiga toxin, outer membrane and secreted proteins, and attachment and penetration mechanisms.
      • Clinical significance: causes shigellosis or bacillary dysentery, transmitted via the fecal-oral route.

    Enterobacteriaceae

    • Phenotypic properties: growth on MacConkey's agar and Blood agar.
    • Antigenic structure:
      • Heat-stable somatic O (lipopolysaccharide) antigens (>150).
      • Heat-labile K (capsular) antigens (>100).
      • Flagellar H antigens (>50).
      • Vi antigens in Salmonella serotype Typhi.
    • Somatic O antigens: heat-stable polysaccharide part of LPS; variation from smooth to rough colonial forms accompanied by progressive loss of smooth O antigen.
    • Flagellar H antigens: heat-labile.
    • Envelope or capsule K antigens: overlay the surface O antigen and may block agglutination by O-specific antisera; destroyed by boiling for 15 minutes.

    E. coli

    • Normal inhabitant of the GI tract.
    • Some strains cause gastroenteritis, urinary tract infections, and neonatal meningitis and septicemia.
    • Biochemistry: most are motile, may be hemolytic on BA, TSI is A/A + gas, urea -, indole +, citrate -, and motility +.
    • Antigenic structure: has O, H, and K antigens; K1 has a strong association with virulence, particularly meningitis in neonates.
    • Adhesins (colonization factors): include pili or fimbriae and non-fimbrial factors involved in attachment; at least 21 different types.
    • Virulence factors: capsule, iron capturing ability (enterochelin), and outer membrane proteins.

    E. coli: Urinary Tract Infections (UTI)

    • Clinical significance: leading cause of UTIs, which can lead to acute cystitis and pyelonephritis.
    • The formation of E. coli biofilms inside bladder epithelial cells may contribute to recurrent UTIs.

    E. coli Infections

    • Neonatal meningitis: leading cause of neonatal meningitis and septicemia with a high mortality rate; usually caused by strains with the K1 capsular antigen.
    • Gastroenteritis: several distinct types of E. coli are involved in different types of gastroenteritis, including enterotoxigenic, enteroinvasive, enteropathogenic, enteroaggregative, and Shiga toxin-producing E. coli.

    Salmonella

    • Clinical significance: causes enteric fevers (typhoid and paratyphoid) and gastroenteritis.
    • In enteric fevers, Salmonella disseminates before multiplying, causing a low-grade fever and constipation; later, the bacteria re-enter the bloodstream, disseminating throughout the body.
    • Diagnosis: blood cultures, stool cultures, and urine cultures; Widal test for antibodies against Salmonella typhi.
    • Antimicrobial therapy: chloramphenicol usually; resistant strains have emerged, making antimicrobial susceptibility testing essential.

    Citrobacter

    • TSI: K/A or A/A, both + gas and H2S.
    • Urea: usually +.
    • Motility: +.
    • Clinical significance: opportunistic pathogen causing urinary tract or respiratory tract infections, and occasionally wound infections, osteomyelitis, endocarditis, and meningitis.

    Edwardsiella tarda

    • TSI: K/A + gas and H2S.
    • Urea: -.
    • Citrate: -.
    • Indole: +.
    • Clinical significance: causes GI disease in tropical and subtropical countries.

    Klebsiella

    • Respiratory and GI tract, but potential pathogen in other areas.
    • TSI: A/A + gas.
    • Urea: +.
    • Citrate: +.
    • MR: -, VP: +.
    • Motility: -.
    • Has both O and K antigens.
    • Virulence factors: capsule, adhesions, and iron capturing ability.
    • Clinical significance: causes pneumonia, mostly in immunocompromised hosts; permanent lung damage is a frequent occurrence.

    Enterobacter

    • GI tract.
    • TSI, LIA, and urea give variable results depending on the species.
    • Citrate: +.
    • Clinical significance: nosocomial infections, bacteremia in burn patients.

    Serratia

    • A free-living saprophyte.
    • TSI: A/A or K/A, +/- gas (does not ferment lactose).
    • LIA: usually K/K.
    • Citrate: +.
    • Motility: +.
    • Urea: +/-.
    • Has been found in RT and UT infections, and is resistant to many antimicrobics.

    Proteus, Providencia, and Morganella

    • GI tract infections.
    • All motile, with Proteus swarming.
    • PA: +.
    • Lysine deamination.
    • Urea: + for most, strongly + for Proteus.
    • TSI: variable.
    • Indole: -.

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    Description

    This quiz covers the different species of Shigella, their biochemistry, and the antibiotic treatment of E coli meningitis and respiratory tract infections.

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