Diagnosing Extended-Spectrum Beta-Lactamase (ESBL) Infections

Collection of Appropriate Specimens

The Infectious Diseases Society of America recommends collecting representative specimens from the site of infection (at least 1 mL of fluid or tissue, preferably more) and transporting to the laboratory in an appropriate transport system 1, 2
For intra-abdominal infections, the World Journal of Emergency Surgery suggests collecting peritoneal fluid or pus in airless sterile syringes or sterile test tubes, as peritoneal swabs and fluid from drain tubes are not recommended 3
The Clinical Infectious Diseases guidelines recommend inoculating 1-10 mL of fluid directly into an aerobic blood culture bottle for optimal recovery of aerobic bacteria 1, 2
The Clinical Infectious Diseases guidelines also suggest sending at least 0.5 mL of fluid to the laboratory for Gram stain and fungal cultures if indicated 1
For anaerobic cultures, the Clinical Infectious Diseases guidelines recommend transporting at least 0.5 mL of fluid or 0.5 g of tissue in an anaerobic transport tube, or inoculating 1-10 mL of fluid directly into an anaerobic blood culture bottle 1

The Journal of Microbiology, Immunology and Infection states that MIC determination is a common laboratory method for ESBL detection 4
The Journal of Microbiology, Immunology and Infection and the Clinical and Laboratory Standards Institute guidelines suggest that routine ESBL testing is no longer necessary before reporting results when using the new interpretive criteria for cephalosporins, but ESBL testing remains useful for epidemiological and infection control purposes 4, 7

The World Journal of Emergency Surgery recommends considering ESBL infection in patients with specific risk factors, including recent exposure to antibiotics (particularly beta-lactams or fluoroquinolones) within 90 days, known colonization with ESBL-producing Enterobacteriaceae, and healthcare-associated infections 3, 5

The International Journal of Antimicrobial Agents suggests that rapid molecular identification of microorganisms and their resistance mechanisms from blood cultures can significantly reduce time to appropriate therapy, and molecular tests should be adopted in patients colonized or potentially infected with ESBL-producing Enterobacteriaceae 6

The International Journal of Antimicrobial Agents states that identification of ESBL-producing organisms is critical for appropriate antibiotic selection, as these infections are associated with higher mortality, complications, and prolonged hospitalization if not properly treated 6