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

INTRODUCTION: 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. 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. 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. RESULTS: 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. 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.

Isolation and molecular characterization of Arcobacter butzleri and Arcobacter cryaerophilus from the pork production chain in Brazil / Isolamento e caracterização molecular de Arcobacter butzleri e Arcobacter cryaerophilus de linhas de abate suíno e do comércio de carne no Brasil

Arcobacter is an emerging zoonotic pathogen, and the major transmission routes to humans are the handling or consumption of contaminated raw/undercooked food products of animal origin, water and seafood. The isolation and identification of Arcobacter species are not routine in clinical laboratories; therefore, its true incidence in human infections may be underestimated. The present study aimed to isolate and characterize Arcobacter from carcasses and fecal samples collected at swine slaughterhouses and from meat markets in São Paulo State, Brazil. The isolates were identified using multiplex-PCR to differentiate the species and analyzed by single-enzyme amplified fragment length polymorphism (SE-AFLP). Arcobacter spp. were isolated from 73.0% of swine carcasses, 4% of fecal samples and 10% of pork samples. A. butzleri was the most prevalent species identified, followed by A. cryaerophilus. Interestingly, the carcasses presented higher frequency of A. butzleri isolation, whereas only A. cryaerophilus was isolated from fecal samples. SE-AFLP enabled the characterization of A. butzleri and A. cryaerophilus into 51 and 63 profiles, respectively. The great genetic heterogeneity observed for both species corroborates previous reports. This study confirms the necessity for a standard isolation protocol and the improvement of molecular tools to further elucidate Arcobacter epidemiology.(AU)

Arcobacter é um patógeno zoonótico emergente e as principais formas de transmissão para humanos são a manipulação e o consumo de água ou alimentos contaminados crus ou mal cozidos. O isolamento e a identificação das espécies de Arcobacter não fazem parte da rotina dos laboratórios clínicos; dessa forma, a real incidência da infecção em humanos é subestimada. O presente estudo teve o objetivo de isolar e caracterizar Arcobacter de carcaças e amostras de fezes coletadas em dois abatedouros de suínos e de carne suína de dois açougues no Estado de São Paulo, Brasil. As estirpes foram identificadas utilizando multiplex-PCR para diferenciar as espécies e foram analisadas por polimorfismo no comprimento de fragmentos amplificados (SE-AFLP). Arcobacter spp. foi isolado de 73% das carcaças, 4% das amostras de fezes e de 10% das amostras de carne suína avaliadas. A. butzleri foi a espécie mais prevalente, seguida por A. cryaerophilus. As carcaças apresentaram a maior taxa de isolamento de A. butzleri enquanto que apenas A. cryaerophilus foi isolado das amostras de fezes. SE-AFLP possibilitou a caracterização de A. butzleri e A. cryaerophilus em 51 e 63 perfis de bandas, respectivamente. A grande heterogeneidade genética observada para ambas as espécies corrobora estudos previous. Estes resultados confirmam a necessidade de protocolos de isolamento padronizados e o aperfeiçoamento das ferramentas moleculares para aprofundar os conhecimetos sobre epidemiologia das infecções pelo gênero Arcobacter.(AU)