Molecular characteristics of extended-spectrum β-lactamase/AmpC-producing Salmonella enterica serovar Virchow isolated from food-producing animals during 2010-2017 in South Korea.

Global dissemination of non-typhoidal Salmonella producing extended-spectrum β-lactamase (ESBL) is a public-health concern. Recently, the prevalence of Salmonella spp. resistant to third-generation cephalosporins has been increasing in food-producing animals in Korea. In this study, we investigated resistance mechanisms and molecular characteristics of S. Virchow isolates resistant to extended-spectrum cephalosporins (ESCs). We obtained 265 S. Virchow isolates from fecal and carcasses samples of cattle (n = 2), pigs (n = 7), and chickens (n = 256) during 2010-2017, and observed high ESC-resistance (63.8%, 169/265); most of the resistant isolates (96.4%) were obtained from chickens. ESC-resistant S. Virchow isolates (n = 169) showed significantly higher resistance rates to other antimicrobials (especially aminoglycosides and tetracycline, p-value <0.0001), as well as prevalence of multidrug resistance, than did ESC-susceptible S. Virchow isolates (n = 96). All ESC-resistant S. Virchow produced CTX-M-15-type ESBL (n = 147) and/or CMY-2-type AmpC β-lactamase (n = 23). ESC-resistant S. Virchow represented seven pulsotypes, predominantly composed of type II (58.6%) and III (26.0%), detected in 69 farms in 10 provinces, and 33 farms in 7 provinces, respectively. Genes encoding ESC-resistance were horizontally transferred by conjugation to recipient E. coli J53; this was demonstrated in 28.8% (42/146) of blaCTX-M-15-positive isolates and in 50.0% (11/22) of blaCMY-2-positive isolates. All conjugative plasmids carrying blaCTX-M-15 and blaCMY-2 genes belonged to ST2-IncHI2 and ST12/CC12-IncI1, respectively. Genetic features of transferred bla genes were involved with ISEcp1 in both blaCTX-M-15 and blaCMY-2; ISEcp1 plays a critical role in the efficient capture, expression, and mobilization of bla genes. In addition to blaCTX-M-15 genes, resistance markers to aminoglycosides and/or tetracycline were co-transferred to recipient E. coli J53. Our results show a high prevalence of ESBL-producing S. Virchow in chickens and chicken carcasses. Specific blaCTX-M-15 and blaCMY-2-carrying S. Virchow clones and plasmids were predominant in food-producing animals nationwide. Restriction of antimicrobial use and proper biosecurity practices at the farm level should be urgently implemented in the poultry industry.

Na SH ，Moon DC ，Kang HY ，Song HJ ，Kim SJ ，Choi JH ，Yoon JW ，Yoon SS ，Lim SK ... -  《-》

Antibiotic Resistance Profiles and Molecular Characteristics of bla(CMY-2)-Carrying Salmonella enterica Serovar Albany Isolated from Chickens During 2013-2020 in South Korea.

Ali MS ，Song HJ ，Moon BY ，Kim SJ ，Kang HY ，Moon DC ，Lee YH ，Kwon DH ，Yoon SS ，Lim SK ... -  《-》

Antibiotic Resistance Profiles and Molecular Characteristics of bla(CTX-M-15)-Carrying Salmonella enterica Serovar Enteritidis Isolates from Healthy and Diseased Chickens in Korea.

Mechesso AF ，Na SH ，Moon DC ，Kim SJ ，Choi JH ，Song HJ ，Yoon SS ，Lim SK ... -  《-》

Characterisation of plasmids implicated in the mobilisation of extended-spectrum and AmpC β-lactamase genes in clinical Salmonella enterica isolates and temporal stability of the resistance genotype.

Plasmids implicated in the mobilisation of β-lactamase genes in extended-spectrum β-lactamase (ESBL)- and AmpC-producing Salmonella enterica isolates recovered from three Spanish hospitals were characterised. The temporal stability of these plasmids and of the resistance phenotype without antimicrobial pressure was also assessed in the laboratory setting. The resistance determinants and their genetic environments were characterised by PCR sequencing, and their genomic location was analysed by S1 nuclease pulsed-field gel electrophoresis (PFGE) and I-CeuI PFGE, followed by Southern blot hybridisation. The 11 S. enterica studied strains carried blaCTX-M-9 (serovar Virchow, 2 isolates), blaCTX-M-10 (Virchow, 2), blaCTX-M-14 (Enteritidis, 1), blaCTX-M-15 (Gnesta and S. enterica group C, 2), blaSHV-2 (Livingstone, 1), blaSHV-12 (Enteritidis, 1) and blaCMY-2 (Bredeney, 2). The ISEcp1-blaCTX-M-14-IS903 and ISEcp1-blaCTX-M-15-orf477 genetic structures were detected. IncI1 and IncA/C plasmids carried blaCTX-M-14, blaCTX-M-15, blaSHV-2, blaSHV-12 and blaCMY-2 genes. blaCTX-M-9 included in an In60 complex integron and blaCTX-M-10 linked to a phage-related element were found in non-typeable plasmids. Conjugation and temporal stability experiments were performed in vitro through daily passages (100 days) in the absence of antimicrobial pressure. In the stability experiments, 5 of the 11 tested isolates lost the ESBL or AmpC plasmidic genes and this was associated with concomitant loss of the whole or partial plasmid. In conclusion, successful plasmids belonging to different Inc groups mobilise ESBL- and AmpC-encoding genes in S. enterica. Loss of ESBL/AmpC genes in the absence of antimicrobial pressure might explain the low prevalence of these β-lactamases among Salmonella isolates.

de Toro M ，García P ，Rodríguez I ，Rojo-Bezares B ，Helmuth R ，Sáenz Y ，Rodicio MR ，Guerra B ，Torres C ... -  《-》

Prevalence and characterization of extended-spectrum beta-lactamases-producing Salmonella enterica isolates in Saragossa, Spain (2001-2008).

Pardos de la Gándara M ，Seral C ，Castillo García J ，Rubio Calvo C ，Weill FX ... -  《-》