Characterisation of the first CTX-M-10-producing isolate of Salmonella enterica serotype Virchow

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 bla_CTX-M-15-positive isolates and in 50.0% (11/22) of bla_CMY-2-positive isolates. All conjugative plasmids carrying bla_CTX-M-15 and bla_CMY-2 genes belonged to ST2-IncHI2 and ST12/CC12-IncI1, respectively. Genetic features of transferred bla genes were involved with ISEcp1 in both bla_CTX-M-15 and bla_CMY-2; ISEcp1 plays a critical role in the efficient capture, expression, and mobilization of bla genes. In addition to bla_CTX-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 bla_CTX-M-15 and bla_CMY-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.

Biocompatible Fe3O4 increases the efficacy of amoxicillin delivery against Gram-positive and Gram-negative bacteria

This paper reports the synthesis and characterization of amoxicillin- functionalized magnetite nanostructures (Fe₃O₄@AMO), revealing and discussing several biomedical applications of these nanomaterials. Our results proved that 10 nm Fe₃O₄@AMO nanoparticles does not alter the normal cell cycle progression of cultured diploid cells, and an in vivo murine model confirms that the nanostructures disperse through the host body and tend to localize in particular sites and organs. The nanoparticles were found clustered especially in the lungs, kidneys and spleen, next to the blood vessels at this level, while being totally absent in the brain and liver, suggesting that they are circulated through the blood flow and have low toxicity. Fe₃O₄@AMO has the ability to be easily circulated through the body and optimizations may be done so these nanostructures cluster to a specific target region. Functionalized magnetite nanostructures proved a great antimicrobial effect, being active against both the Gram positive pathogen S. aureus and the Gram negative pathogen E. coli. The fabricated nanostructures significantly reduced the minimum inhibitory concentration (MIC) of the active drug. This result has a great practical relevance, since the functionalized nanostructures may be used for decreasing the therapeutic doses which usually manifest great severe side effects, when administrated in high doses. Fe₃O₄@AMO represents also a suitable approach for the development of new alternative strategies for improving the activity of therapeutic agents by targeted delivery and controlled release.

Epidemiology and genetics of CTX-M extended-spectrum β-lactamases in Gram-negative bacteria

CTX-M enzymes, the plasmid-mediated cefotaximases, constitute a rapidly growing family of extended-spectrum β-lactamases (ESBLs) with significant clinical impact. CTX-Ms are found in at least 26 bacterial species, particularly in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. At least 109 members in CTX-M family are identified and can be divided into seven clusters based on their phylogeny. CTX-M-15 and CTX-M-14 are the most dominant variants. Chromosome-encoded intrinsic cefotaximases in Kluyvera spp. are proposed to be the progenitors of CTX-Ms, while ISEcp1, ISCR1 and plasmid are closely associated with their mobilization and dissemination.

Emergence of extended-spectrum beta-lactamases and AmpC-type beta-lactamases in human Salmonella isolated in Spain from 2001 to 2005

OBJECTIVES

To study the resistance to third-generation cephalosporins in Salmonella strains isolated from humans in a 5 year period in Spain, and to identify the responsible genes and their dissemination.

METHODS

Twenty-seven isolates were analysed by PCR and sequencing to identify the genes responsible for the beta-lactamase resistance phenotypes. The transferability of the phenotypes was tested by conjugation to Escherichia coli K12J53, plasmid detection with S1-PFGE, hybridization and PCRs of the transconjugants. The genetic relationship was determined by PFGE.

RESULTS

We found bla(CTX-M-9) and bla(CTX-M-10) in Salmonella Virchow PT19. bla(CTX-M-14) was detected in Salmonella (IV) 44:z(4),z(23):-, Salmonella Enteritidis PT6a, Salmonella Typhimurium DT193 and Salmonella Typhimurium DT104B. bla(CTX-M-1) was found in Salmonella Litchfield. bla(CTX-M-15) and bla(CTX-M-32) were found in Salmonella Enteritidis PT1. bla(SHV-12) was found in Salmonella Blockley, Salmonella Hadar PT2, Salmonella Enteritidis PT21, Salmonella Enteritidis PT1 and Salmonella Bredeney. bla(SHV-2) was found in Salmonella Livingstone. bla(CMY-2) was detected in Salmonella Bredeney, Salmonella Newport, Salmonella Enteritidis PT5b and Salmonella Heidelberg. bla(DHA-1) was detected for the first time in Spain in Salmonella Newport. One strain of Salmonella Senftenberg harboured two extended-spectrum beta-lactamases, bla(SHV-12) and bla(CTX-M-9). We have found a large variety of beta-lactamase families as well as several members of major relevance, such as CTX-M-15, CTX-M-32, CMY-2 and DHA-1. XbaI-PFGE, conjugation assays and S1-PFGE hybridization showed that all these beta-lactamases were mediated by plasmids.

CONCLUSIONS

This study demonstrates the emergence of a public health risk related to resistance to beta-lactams in Salmonella. The resistance trends need to be monitored carefully.

Prevalence, antimicrobial resistance, and extended-spectrum beta-lactamases characterization of Salmonella isolates in Apulia, southern Italy (2001-2005)

The prevalence, antimicrobial susceptibility, and production of extended-spectrum beta-lactamases (ESBLs) of Salmonella collected from several hospitals in Apulia (southern Italy) were evaluated. The most common Salmonella isolates were Salmonella enterica serovar Typhimurium (44.6%), S. enterica serovar Enteritidis (33.4 %), S. enterica serovar Infantis (3.2 %), S. enterica serovar Typhi (1.5%), and S. enterica serovar Bovismorbificans (1.5%). The other serovars accounted for less than 1% each. Our data show a high resistance to ampicillin, tetracycline, and chloramphenicol. The isolates were pansensitive (53.5%), resistant to one antimicrobial agent (10.5%), resistant to two antimicrobial agents (22.1%), resistant to three antimicrobial agents (10.8%), and to four antimicrobial agents (2.7%). Resistance to more than four antibiotics was observed in 0.5% of strains. The presence of ESBL was found in only one strain of S. enterica serovar Bovismorbificans. The CTX-M-1 type-producing strain was identified by isoelectric focusing and molecular analysis. Results were consistent with the presence of a pI 8.6 ESBL active on cefotaxime, ceftazidime, cefepime, and aztreonam. Mating experiments showed that the CTX-M-1 determinant was transferable. To the best of our knowledge, this is the first report of CTX-M-1 type ESBL in Salmonella serovar Bovismorbificans.