Salmonella enterica is one of the most common bacterial causes of foodborne illness, and nontyphoidal Salmonella is estimated to cause ∼1.2 million illnesses in the United States each year. Plasmids are mobile genetic elements that play a critical role in the dissemination of antimicrobial resistance determinants. AmpC-type CMY β-lactamases (bla(CMY)) confer resistance to extended-spectrum cephalosporins and β-lactam/β-lactamase inhibitor combinations and are commonly plasmid-encoded. A variety of plasmids have been shown to encode CMY β-lactamases and certain plasmids may be associated with particular Salmonella serotypes or environmental sources. In this study, we characterized bla(CMY) β-lactamase-encoding plasmids among Salmonella isolates. Isolates of Salmonella from specimens collected from humans in 2007 were submitted to the Centers for Disease Control and Prevention National Antimicrobial Resistance Monitoring System laboratory for susceptibility testing. Three percent (65/2161) of Salmonella isolates displayed resistance to ceftriaxone (minimum inhibitory concentration [MIC] ≥4 mg/L) and amoxicillin/clavulanic acid (MIC ≥32 mg/L), a combination associated with the presence of a bla(CMY) mechanism of resistance. Sixty-four (98.5%) isolates were polymerase chain reaction-positive for bla(CMY) genes. Transformation and conjugation studies showed that 95% (61/64) of the bla(CMY) genes were plasmid-encoded. Most of the bla(CMY)-positive isolates were serotype Typhimurium, Newport, Heidelberg, and Agona. Forty-three plasmids were replicon type IncA/C, 15 IncI1, 2 contained multiple replicon loci, and 1 was untypeable. IncI1 plasmids conferred only the bla(CMY)-associated resistance phenotype, whereas IncA/C plasmids conferred additional multi-drug resistance (MDR) phenotypes to drugs such as chloramphenicol, sulfisoxazole, and tetracycline. Most of the IncI1 plasmids (12/15) were sequence type 12 by plasmid multi-locus sequence typing. CMY β-lactamase-encoding plasmids among human isolates of Salmonella in the United States tended to be large MDR IncA/C plasmids or single resistance determinant IncI1 plasmids. In general, IncI1 plasmids were identified among serotypes commonly associated with poultry, whereas IncA/C plasmids were more likely to be identified among cattle/beef-associated serotypes.
"11 ; Lindsey et al . , 2011 ; Randall et al . , 2011 ; Folster et al . , 2012 ; Del Castillo et al . , 2013 ; Guo et al . , 2014 ) . Disturbingly , recent studies identified multiple extended - spectrum β - lactamases ( ESBLs ) - encoding ACPs conferring resistance to a wide range of β - lactam antimicrobials ( Fernandez - Alarcon et al . , 2011 ; Folster et al . , 2011 , 2012 ; Walsh et al . , 2011 ; Harmer and Hall , 2015 ) . Carbapenems were the last effective β - lactams for the treatment of infectious bacteria carrying ESBLs . Unfortunately , several recently isolated ACPs propagate the infamous New Delhi metallo - β - lactamase bla NDM−1 gene and its variants , which code for zinc metallo - β - l"
[Show abstract][Hide abstract] ABSTRACT: Nowadays, healthcare systems are challenged by a major worldwide drug resistance crisis caused by the massive and rapid dissemination of antibiotic resistance genes and associated emergence of multidrug resistant pathogenic bacteria, in both clinical and environmental settings. Conjugation is the main driving force of gene transfer among microorganisms. This mechanism of horizontal gene transfer mediates the translocation of large DNA fragments between two bacterial cells in direct contact. Integrative and conjugative elements (ICEs) of the SXT/R391 family (SRIs) and IncA/C conjugative plasmids (ACPs) are responsible for the dissemination of a broad spectrum of antibiotic resistance genes among diverse species of Enterobacteriaceae and Vibrionaceae. The biology, diversity, prevalence and distribution of these two families of conjugative elements have been the subject of extensive studies for the past 15 years. Recently, the transcriptional regulators that govern their dissemination through the expression of ICE-or plasmid-encoded transfer genes have been described. Unrelated repressors control the activation of conjugation by preventing the expression of two related master activator complexes in both types of elements, i.e., SetCD in SXT/R391 ICEs and AcaCD in IncA/C plasmids. Finally, in addition to activating ICE-or plasmid-borne genes, these master activators have been shown to specifically activate phylogenetically unrelated mobilizable genomic islands (MGIs) that also disseminate antibiotic resistance genes and other adaptive traits among a plethora of pathogens such as Vibrio cholerae and Salmonella enterica.
Frontiers in Microbiology 09/2015; 6(837). DOI:10.3389/fmicb.2015.00837 · 3.99 Impact Factor
"Recently, Salmonella has developed resistance to cephalosporin through the transmission of PABL , of which CMY-2 is the most common. CMY-2 was first reported in the USA and is the most widely distributed PABL, with cases also reported in France, Germany, Greece and the United Kingdom; indeed, it was recently isolated from a cow in Japan and from pigs in China [1,3,12-14]. In most cases, the CMY-2 gene is present in large plasmids, of which several genetic types have been reported. "
[Show abstract][Hide abstract] ABSTRACT: Abstracts
Salmonella resistant to third-generation cephalosporin has been isolated from an increasing number of animals worldwide. The purpose of this study was to examine ESBL (extended-spectrum β-lactamases)-producing and PABL (plasmid-mediated AmpC β-lactamases)-producing Salmonella isolates from pigs in South Korea.
Salmonella Typhimurium KVCC-BA1300259 was resistant to ampicillin, amoxicillin/clavulanic acid, cephalothin, chloramphenicol, florfenicol, cefoxithin, gentamicin, nalidixic acid, trimethoprim/sulfamethoxazole, tetracycline, and ceftiofur. The results of a double-disk synergy test and PCR confirmed that the isolate produced CMY-2 (PABL). Analysis of plasmid incompatibility (Inc) groups revealed the presence of IncA/C and IncFIB, indicating antimicrobial resistance. This study is the first to identify S. Typhimurium isolates harboring CMY-2 in pigs in South Korea.
The presence of CMY-2 in pigs poses a significant threat of possible horizontal spread between animals and humans.
BMC Research Notes 06/2014; 7(1):329. DOI:10.1186/1756-0500-7-329
"The bla CMY-2 -encoding gene has the widest distribution of all the ampC-like genes, and its occurrence and transmission between various enteric bacterial species are well documented (Deshpande et al., 2006). Studies of bacterial isolates cultured from foodproducing animals highlighted the fact that ampC-like genes move horizontally between different hosts and are commonly associated with IncI1 and IncA/C plasmid replicon types (Mulvey et al., 2009; Folster et al., 2011; Martin et al., 2012). Transposable elements are also known to mediate the acquisition and transmission of these genetic determinants. "
[Show abstract][Hide abstract] ABSTRACT: A blaCMY-2 -containing conjugative IncF plasmid denoted as pEQ011, previously identified in a multidrug-resistant Escherichia coli isolate of equine origin, was characterized. The plasmid consisted of 85 507 bp, with 118 predicted open reading frames. This is the first known report demonstrating the association of a blaCMY-2 gene with an IncF incompatibility-type plasmid backbone. A novel genetic arrangement was identified wherein the blaCMY-2 resistance gene was proximally flanked by IS1294 along with a partial blc gene located distally and within a yacABC operon.
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