Comparison of multidrug-resistant Salmonella enterica serovar Newport isolates from a patient and sewages in Fukui Prefecture

Abstract

From May 2003 to March 2004, nine strains of multidrug-resistant (MDR) Salmonella enterica serovar Newport were isolated from 5 sewages of 3 sewage treatment plants located in 2 different regions of Fukui Prefecture. Antimicrobial susceptibility testing identified 2 different MDR patterns (type I and II). Type I strains were resistant to ampicillin, tetracycline, streptomycin, chloramphenicol, amoxicillin/clavulanic acid, sulfisoxazole, cefotaxime, cephalothin, ceftriaxone, and ceftrazidime and type II strains were additionally resistant to sulfamethoxazole-trimethoprim and spectionomycin. Neither of kanamycin, fosfomycin, nalidixic acid, gentamycin, or ciprofloxacin resistance was observed. Type I and II strains were different in pulsed-field gel electrophoresis patterns and plasmid profiles, while they showed the same profiles with in each type. All the MDR strains in this study were proved to carry the blaCMY-2 gene by PCR and sequence analyses. Numbers of reports on MDR S. Newport with blaCMY-2 have been increasing in foreign countries such as the United States. The MDR patterns of the isolates in this study were similar to those of the United States. These properties of the type I strains were identical with that a strain isolated from a 7-year-old patient in Fukui Prefecture, in September 2003 which we previously reported. However, the patient lived in a region where no epidemiological associations with the sewage treatment plants were found. This suggests that the MDR strains might prevail in Fukui Prefecture. Domestic surveillance for MDR S. Newport would be need.