Diversity and characterization of oxytetracycline-resistant bacteria associated with non-native species, white-leg shrimp (Litopenaeus vannamei), and native species, black tiger shrimp (Penaeus monodon), intensively cultured in Thailand

Abstract

Aims: This study aimed at surveying prevalence of oxytetracycline (OTC)‐resistant bacteria in the white‐leg shrimp Litopenaeus vannamei, and the black tiger shrimp Penaeus monodon, intensively cultured in Thailand. We investigated the phylogenetic diversity of the bacterial isolates, as well as the minimum inhibitory concentration (MIC) of OTC, the occurrence of major OTC‐resistant genes and multiple‐antibiotic resistance in the isolates. Methods and Results: Shrimps were collected from culture ponds, and the homogenates of whole bodies were plated on tryptic soy agar supplemented with or without OTC. Percentages of OTC‐resistant bacteria were 0·3–52·1% in white‐leg samples and 0·008–22·3% in black tiger samples. Analyses of 16S rDNA sequences indicated that most OTC‐resistant isolates were closely related to Aeromonas spp. and Lactococcus garvieae. MICs of OTC were 4–128 μg ml−1 in the OTC‐resistant aeromonads and 128–256 μg ml−1 in OTC‐resistant L. garvieae. OTC resistance was found to be conferred by the genes tet(A), tet(C), tet(D), tet(E), tet(M) and tet(S), detected either singly or in pairs. No resistance to ceftazidime, imipenem or chloramphenicol was observed in any isolate. Conclusions: Both species of shrimp are associated with OTC‐resistant bacteria, occasionally at high densities exceeding 106 cfu g−1. The associated bacteria, predominantly Lactococcus and Aeromonas genera, are potential pathogens and are reservoirs of a variety of OTC‐resistant genes. Significance and Impact of the Study: Cultured shrimps can be vehicle to carry OTC‐resistant bacteria to domestic and foreign consumers via the food chain. Very low populations of OTC‐resistant bacteria observed in the several ponds suggest that levels of the resistant bacteria are artificially high and should be reduced in farmed shrimps.

Prevalence and Antimicrobial Susceptibility of Vibrio parahaemolyticus Isolated from Short Mackerels (Rastrelliger brachysoma) in Malaysia

“…Nevertheless, the majority of the isolates were susceptible to most antibiotics tested in this study. Susceptibility profiles of V. parahaemolyticus isolates to antibiotic classes such as tetracycline, phenicols, quinolone, and cephalosporin were comparable with many other studies reported in several countries and sample sources (Lesmana et al, 2001; Han et al, 2007; Yano et al, 2011; Ottaviani et al, 2013). In this study, 37.31% of isolates with MAR value more than 0.2 indicating samples originated from a high risk source of contamination where several antibiotics are used (Krumperman, 1983).…”

Bacterial Flora and Antimicrobial Resistance in Raw Frozen Cultured Seafood Imported to Denmark

“…Previous studies on antimicrobial resistance in seafood have almost entirely determined resistance for other, mainly zoonotic, bacterial pathogens, including Vibrio (1,3,11,16,24,32,38), Aeromonas (1,3,25,28,42), Salmonella (16,32), and the fecal indicator E. coli (1,16,21,34). Little is known about the normal bacterial flora in cultured shrimp and fish at the point of harvest or in the final processed products.…”

Antibiotic resistance of Vibrio parahaemolyticus and Vibrio vulnificus in various countries: A review

“…Similarly, in Thailand, Yano et al (2014) reported high resistance to ampicillin (72%) of V. parahaemolyticus strains isolated from inland ponds' shrimp, and 20% of V. vulnificus isolates showed resistance to nalidixic acid. Both Vibrio spp.…”