Application of α-glucosidase activity and drug susceptibility tests to epidemiological studies on the fish pathogen Nocardia seriolae

Abstract

This study determined the minimum inhibitory concentrations (MICs) for oxytetracycline hydrochloride (OTC) and erythromycin (Em), along with the a-glucosidase (a-glu) activities in 110 Nocardia seriolae strains isolated in Miyazaki and Kagoshima prefectures in 2008-2009. The strains were examined for the presence of the tet(K), tet(L), tet(M), tet(O), tet(S), erm(A), erm(B), mph(A), mef(A), and msr(D) genes. All the a-glu-positive strains (n = 15) were OTC resistant and Em sensitive, with MICs of 32-64 and \0.125 lg/ml, respectively. All the aglu-negative strains (n = 95) were OTC sensitive, with MICs of 2-4 lg/ml, and most of them (93 of 95) were Em resistant, with MICs of [128 lg/ml. The MICs for Em in the remaining 2 a-glu-negative strains were \0.125 lg/ml. The 15 OTC-resistant strains possessed the tet(K) and/or tet(L) gene(s), and all of the 93 Em-resistant strains possessed both the mef(A) and msr(D) genes. The relationship between a-glu activity and drug sensitivity of the N. seriolae strains may explain the difference in prevalence of each phenotype. Nevertheless, the relationship should be further explored using N. seriolae isolates collected from more prefectures and farms.

Genomic characterization of Nocardia seriolae strains isolated from diseased fish

“…In the genomes of Nocardia strains, resistance genes against several kinds of antibiotics were detected with more than 30% similarity to previously known antibiotic resistance genes (Figure ). According to Yasuike et al., the N. seriolae strains can be divided into two groups according to their α‐glucosidase activity and susceptibility to erythromycin or oxytetracycline (Ismail, Takeshita, Umeda, Itami, & Yoshida, ; Yasuike et al., ). All N. seriolae strains analyzed in this study contained the gene encoding α‐glucosidase, but did not have resistance genes against erythromycin or oxytetracycline.…”

“…Resistance against several kinds of antibiotics is a major feature of the genus Nocardia (Hashemi‐Shahraki et al., ; Ismail et al., ). Pathogens possessing diverse antibiotic resistance genes can cause severe problems, such as the transfer of antibiotic resistance genes to other bacteria and an increase in multi‐drug resistant pathogens.…”

In vitro activity of some essential oils alone and in combination against the fish pathogen Nocardia seriolae

“…0.5 McFarland standard as previously reported (Ismail et al 2011a), and were diluted 100-fold with sterile 0.85% NaCl (10 5 to 10 6 CFU/ml). Cinnamon (Cinnamomum zeylanicum), thyme (Thymus vulgaris), lemongrass (Cymbopogon flexuosus) and tea tree (Melaleuca alternifolia) EOs were obtained from Naturas Psychos (http:// www.naturas-psychos.com) as 100% pure oils.…”

“…The previously proposed environmental selective pressure for the routinely used oxytetracycline (OTC) and erythromycin (Em) antibiotics in the Asian aquaculture resulted in a marked prevalence of the h-glucosidase (glu)-positive N. seriolae that were OTC resistant and Em sensitive in Asian countries, while the h-glu-negative N. seriolae that were OTC sensitive and Em resistant prevailed in Japan (Ismail et al 2011a(Ismail et al , 2011b. For these reasons, the search for antimicrobial safer compounds that have no harmful effects on fish, consumers and the environment is greatly encouraged.…”

Draft Genome Sequence of Erythromycin- and Oxytetracycline-Sensitive Nocardia seriolae Strain U-1 (NBRC 110359)

“…seriolae causes nocardiosis mainly in cultured yellowtail ( Seriola quinqueradiata ) and amberjack ( Seriola dumerili ) (4), which can be controlled by using sulfamonomethoxine and sulfisozole sodium (http://www.maff.go.jp/j/syouan/suisan/suisan_yobo/). On the other hand, the emergence of resistant strains to macrolide antibiotics (i.e., erythromycin, spiramycin, and kitasamycin) and oxytetracycline has previously been reported (5–7). We isolated seven N .…”