Characterization of antibiotic resistance in Listeria spp. isolated from slaughterhouse environments, pork and human infections.

Luisa Z Moreno,Renata Paixão,Daniele C Raimundo,Débora D S Gobbi,Andrea M Moreno,Ernesto Hofer,Maria H Matté,Glavur R Matté,Cristhiane M F Reis,Thais P Ferreira

doi:10.3855/jidc.4188

Abstract

Listeria species are susceptible to most antibiotics. However, over the last decade, increasing reports of multidrug-resistant Listeria spp. from various sources have prompted public health concerns. The objective of this study was to characterize the antibiotic susceptibility of Listeria spp. and the genetic mechanisms that confer resistance. Forty-six Listeria spp. isolates were studied, and their minimal inhibitory concentrations of antibiotics were determined by microdilution using Sensititre standard susceptibility MIC plates. The isolates were screened for the presence of gyrA, parC, lde, lsa(A), lnu(A), and mprF by PCR, and the amplified genes were sequenced. All isolates were susceptible to penicillin, ampicillin, tetracycline, erythromycin, and carbapenems. Resistance to clindamycin, daptomycin, and oxacillin was found among L. monocytogenes and L. innocua, and all species possessed at least intermediate resistance to fluoroquinolones. GyrA, parC, and mprF were detected in all isolates; however, mutations were found only in gyrA sequences. A high daptomycin MIC, as reported previously, was observed, suggesting an intrinsic resistance of Listeria spp. to daptomycin. These results are consistent with reports of emerging resistance in Listeria spp. and emphasize the need for further genotypic characterization of antibiotic resistance in this genus.

Highlights

Listeria species are susceptible to most antibiotics
25 were isolated from pork and slaughterhouse environments (15 isolates of L. monocytogenes and of L. innocua), isolates of L. monocytogenes were from human infections, two isolates were L. ivanovii, two isolates were L. seeligeri, two isolates were L. welshimeri, and four were controls (L. monocytogenes ATCC 19115 and ATCC 19111, and L. innocua ATCC 33090 and CLIP 12612) (Table 1)
Resistance to clindamycin and oxacillin was found among L. monocytogenes and L. innocua isolates and included L. monocytogenes isolates of human origin

Summary

Introduction

Over the last decade, increasing reports of multidrug-resistant Listeria spp. from various sources have prompted public health concerns. The objective of this study was to characterize the antibiotic susceptibility of Listeria spp. and the genetic mechanisms that confer resistance. Methodology: Forty-six Listeria spp. isolates were studied, and their minimal inhibitory concentrations of antibiotics were determined by microdilution using Sensititre standard susceptibility MIC plates. Conclusions: These results are consistent with reports of emerging resistance in Listeria spp. and emphasize the need for further genotypic characterization of antibiotic resistance in this genus. Eight species are currently described in the Listeria genus: L. monocytogenes, L. innocua, L. seeligeri, L. welshimeri, L. ivanovii, L. grayi, L. marthii, and L. rocourtiae [2]. L. monocytogenes and L. ivanovii are considered to be pathogenic to animals and humans [1]; instances of human listeriosis due to L. seeligeri and L. innocua infection have been reported [3,4]. The standard treatment remains the application of high doses of a beta-lactam antibiotic (ampicillin or amoxicillin) alone or in combination with gentamicin; sulfamethoxazole is generally used in the case of betalactam intolerance [7]

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Conclusion