Genotyping and antimicrobial susceptibility of Salmonella enterica serotype Panama isolated in Taiwan

Background and Purpose: Previous studies have indicated that Salmonella enterica serotype Panama causes systemic infections in humans. The present study was undertaken to gain more understanding of the molecular epidemiology and antimicrobial resistance of Salmonella Panama. Methods: Antimicrobial susceptibility testing and molecular typing were performed on 9 clinical isolates by pulsed-field gel electrophoresis (PFGE). The presence of resistance genes, Salmonella genomic island 1 (SGI1), and integrons was examined by polymerase chain reaction. Plasmid profiles of these isolates were also determined. Results: Molecular typing showed 3 predominant PFGE types with 6 subtypes among these isolates. High rates of antimicrobial resistance to trimethoprim-sulfamethoxazole (66.7%), tetracycline (66.7%), chloramphenicol (66.7%), ampicillin (55.6%), streptomycin (55.6%), kanamycin (55.6%), and gentamicin (44.4%) were found. All 9 isolates were susceptible to ceftriaxone, cefixime, imipenem, amikacin, and ciprofloxacin. Isolates with PFGE type P1 and subtype P1-1 contained a class 1 integron and resistance genes sulI and str (p=0.048). Plasmids of 3 to 20 kb were found in all isolates belonging to PFGE type P1, subtypes P1-1 and P1-2, which were associated with multidrug resistance (p=0.012) and the resistant gene bla_TEM (p=0.048). There was no SGI1 found in these 9 isolates. Conclusions: In view of the high rates of drug resistance to the antimicrobial agents tested, extended-spectrum cephalosporins and fluoroquinolones seem to be a better choice for treatment of systemic infection caused by Salmonella Panama. There is a major clone (P1 and its subtypes) among the Salmonella Panama isolates. Multidrug resistance was conferred by integrons or plasmids, rather than SGI1.