10 Questions
What type of specimens are used for diagnosing Enterobacteriaceae?
Urine, blood, pus, spinal fluid, sputum
What is indicated by the presence of large capsules in smears?
Klebsiella species
On what type of media are specimens plated for culture?
Blood agar and differential media
What do multiplex NAATs detect in specimens?
Common pathogens and resistance markers
What makes antibiotic susceptibility testing essential in treatment?
High variability in susceptibility
What is a common preventive measure for traveler's diarrhea?
Daily ingestion of bismuth subsalicylate suspension
What is the major habitat of E. coli in the body?
Intestinal tract
How are enteric bacteria commonly transmitted within hospitals?
By medical personnel and instruments
What specific antibiotics are suggested for brief treatment of traveler's diarrhea?
Ciprofloxacin or trimethoprim-sulfamethoxazole
What are the primary control measures in hospitals for multidrug-resistant enteric bacteria?
Surveillance and contact precautions
Study Notes
Enteric Gram-Negative Rods Enterobacteriaceae
Diagnostic Laboratory Tests
- Specimens include urine, blood, pus, spinal fluid, sputum, or other material depending on the disease location.
- Morphologically, Enterobacteriaceae resemble each other, with large capsules suggesting Klebsiella species.
- Specimens are plated on both blood agar and differential media for rapid preliminary identification.
- Nucleic Acid Amplification Tests (NAATs) detect Enterobacteriaceae in specimens such as positive blood cultures, cerebrospinal fluid, respiratory specimens, and stool, and may also detect resistance markers.
Immunity
- Specific antibodies develop in systemic infections, but it is unclear if significant immunity to the organisms follows.
Treatment
- No single specific therapy is available for Enterobacteriaceae.
- Sulfonamides, ampicillin, cephalosporins, fluoroquinolones, and aminoglycosides have marked antibacterial effects, but susceptibility varies and laboratory tests are essential.
- Multiple drug resistance is common and controlled by transmissible plasmids.
- Treatment of gram-negative bacteremia and impending septic shock requires rapid institution of antimicrobial therapy and restoration of fluid and electrolyte balance.
Epidemiology, Prevention, and Control
- Enteric bacteria establish themselves in the normal intestinal tract within a few days after birth and form a main portion of the normal aerobic microbial flora.
- Control measures are not feasible for normal endogenous microbiota.
- Enteropathogenic E.coli serotypes should be controlled like salmonellae.
- Enterics are a major problem in hospital infection, particularly in debilitated patients.
- Control depends on handwashing, rigorous asepsis, sterilization of equipment, disinfection, and strict precautions in keeping the urinary tract sterile.
The Shigellae
- The natural habitat of shigellae is limited to the intestinal tracts of humans and other primates.
This quiz covers the diagnostic laboratory tests for Enterobacteriaceae, including specimen collection, smears, and culture. It is essential for microbiology and laboratory medicine students.
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