Isolation of Multidrug-Resistant Stenotrophomonas maltophilia from Cultured Yellowtail ( Seriola quinqueradiata ) from a Marine Fish Farm

Abstract

Six strains of multidrug-resistant Stenotrophomonas maltophilia were isolated from cultured yellowtail. The strains were divided into two clusters based on the 16S rRNA genes, and all of them contained L1 metallo-␤-lactamase and L2 ␤-lactamase genes. Differences in the intercluster divergence between the lactamase genes suggest that horizontal transfer of the genes occurred.Stenotrophomonas maltophilia is a multidrug-resistant bacterium that has been isolated from numerous terrestrial environments (3,7,12,18) and recently has emerged as a nosocomial pathogen in clinical environments (8,13,19,30). Although the phylogenetic relationship between environmental and clinical strains has been examined, no clear distinction has been established yet.We isolated six strains of S. maltophilia, which were identified with API 20NE (BioMerieux, La Balm, France), from yellowtail (Seriola quinqueradiata) cultured in a fish farm located at the southern tip of Japan (14). All six strains grew on Muller-Hinton agar (Becton Dickinson Microbiology Systems, Cockeysville, MD) supplemented with either ampicillin (32 g ml Ϫ1 ) or panipenem (32 g ml Ϫ1 ). The strains were also resistant to cefotaxime and ceftazidime, as determined by susceptibility tests with Sensi-Disks (Showa, Tokyo, Japan). Although the strains grew in a seawater-based medium, the growth rates in this medium were 0.6-fold lower than those with no NaCl. Hence, we concluded that the strains are not indigenous to marine environments. The resistance to ampicillin seemed to be a factor that could induce the presence of S. maltophilia in the fish farm, since medication with ampicillin was used in the previous year according to the fish farmer. Samuelsen et al. have reported persistence of drug-resistant bacteria even in the absence direct selection (28). NaCl may have been a factor in the survival. Resistance to panipenem, cefotaxime, and ceftazidime probably did not play a role in the distribution of the strains, since none of these antibiotics can be used in aquaculture. Rather, the resistance to these drugs suggests that the strains were derived from clinical environments.16S rRNA gene sequences of the six strains were determined for the phylogenetic analysis by a method described previously (14). The phylogenetic analysis divided the strains into two distinct clusters, cluster A (strains BL-9, BL-10, BL-15, and BL-16) and cluster B (strains BL-12 and BL-13), and both of the clusters were included in group I described by Hauben et al., which is comprised mainly of clinical and environmental strains (15).PCR amplification with forward primer 5Ј-CACACCTGGC AGATCGGCAC-3Ј and reverse primer 5Ј-GCCGCATCCGC GTAGGC-3Ј at an annealing temperature of 65°C was used to amplify L1 metallo-␤-lactamase (L1), which can degrade carbapenems (23,24,33). L2 serine ␤-lactamase (L2), which cannot degrade carbapenems (23, 32), was PCR amplified with forward primer 5Ј-CGATTCCTGCAGTTCAGT-3Ј and reverse primer 5Ј-CGGTTACCTCATCCGATC-3Ј at an annealing temperature of 55°C. No differences were foun...

Stenotrophomonas maltophilia: an Emerging Global Opportunistic Pathogen

“…It has been isolated from aqueous-associated sources both inside and outside the hospital/clinical setting ( Table 2). S. maltophilia has been recovered from soils and plant roots, animals (29,30,31,117,138,140,141,160,163,233,265), invertebrates (286), water treatment and distribution systems (142), wastewater plants (158), sinkholes (75), lakes (279), rivers (239), biofilms on fracture surfaces in aquifers (159), washed salads (273), hemodialysis water and dialysate samples (15), faucets, tap water, bottled water (81,316,345,363,367), contaminated chlorhexidine-cetrimide topical antiseptic (369), hand-washing soap (176), contact lens solutions (116), ice machines (272), and sink drains (39). A significant feature of S. maltophilia is its ability to adhere to plastics and form bacterial films (biofilms).…”

“…MDR S. maltophilia strains have been isolated from domestic and wild animals (117,138,140,141,163) (Table 2 Mouth swabs of 16 out of 22 species of captive snakes revealed the presence of S. maltophilia (140). PFGE profiling revealed the heterogeneity of S. maltophilia isolates, as 8 snake species had more than one strain of S. maltophilia.…”

“…All 6 S. maltophilia isolates recovered from yellowtail fish from a marine fish farm exhibited resistance to ampicillin, panipenem, cefotaxime, and ceftazidime (117). In veterinary medicine, S. maltophilia is not commonly considered to be a significant pathogen.…”

“…PCR amplification has been used to detect the presence of L1 metallo-␤-lactamase (L1) and L2 serine ␤-lactamase (L2) in six strains of S. maltophilia isolated from yellowtail (Seriola quinqueradiata) in a fish farm (117). 16S rRNA gene sequencing revealed two clusters, clusters A and B, of the strains.…”

A Stenotrophomonas maltophilia Multilocus Sequence Typing Scheme for Inferring Population Structure

“…It has, for instance, been isolated from the rhizosphere of various plants and animals (14,27,37). Due to its tolerance against cadmium and its ability to degrade xenobiotic compounds, it has been proposed for remediation of contaminated ground (9,39).…”