Antimicrobial Susceptibility of Listeria monocytogenes Food Isolates from Different Cities in Colombia

One hundred eight Listeria monocytogenes food isolates from four cities in Colombia and previously confirmed by multiplex polymerase chain reaction were characterized for antimicrobial susceptibility. Isolates were evaluated against 17 antimicrobials contained in the MICroSTREP plus (R) 3 panel (MicroScan system). Susceptibility found for ampicillin, amoxicillin/clavulanic acid, and chloramphenicol was 100%, whereas it was 98% for other antimicrobials such as trimethoprim/sulfamethoxazole, 97% for azithromycin, 92% for vancomycin, 90% for erythromycin, 86% for tetracycline, 84% for penicillin, 70% for ciprofloxacin, 57% for rifampin, 56% for meropenem, and 32% for clindamycin. Natural resistance to cephalosporins was confirmed in all cases, and 16% of isolates were nonsusceptible to penicillin. Using Staphylococcus spp. or Enterococcus spp. breakpoints, 48% of isolates displayed multidrug resistances, and the major resistance phenotypes were against rifampin, clindamycin, ciprofloxacin, azithromycin, and erythromycin. Colombian food isolates displayed high resistance to clindamycin, meropenem, rifampin, and ciprofloxacin (30%-65%), and the primary drugs of choice against listeriosis remain effective for most of isolates (84%).