Shiga toxin-producing Escherichia coli isolated from pasteurized dairy products from Bahia, Brazil.

The presence of pathogenic Shiga toxin-producing Escherichia coli (STEC) in dairy products represents a public health concern because of its ability to produce the toxins Stx1 and Stx2, which cause intestinal diseases. Monitoring the stages of milk production and checking dairy products for contamination are crucial steps to ensure dairy safety. This study aimed to report the occurrence of thermotolerant coliforms, E. coli, and STEC strains in pasteurized dairy products and to evaluate the antibiotic resistance profiles, serotypes, and characterizations of the STEC isolates by pulsed-field gel electrophoresis. We obtained a total of 138 pasteurized dairy products from 15 processing plants in Bahia, Brazil, to examine coliforms, E. coli, and STEC strains. We found that 43% of samples (59/138) contained thermotolerant coliforms, and 30% (42/138) did not comply with Brazilian regulations. Overall, 6% (9/138) were positive for E. coli and 4% (5/138) were positive for STEC. We recovered 9 STEC isolates from pasteurized cream (2/9), Minas Padrão cheese (2/9), Minas Frescal cheese (4/9), and ricotta (1/9). All isolates were stx2-positive, and 2 were eae-positive. All isolates were negative for the "big 6" STEC serogroups, belonging instead to serotypes ONT:HNT, ONT:H12, O148:H-, OR:H40, OR:HNT, and O148:HNT. Pulsed-field gel electrophoresis revealed 100% genetic similarity among 3 isolates from 2 different samples produced in the same production facility, which may suggest cross-contamination. As well, we found isolates that were 98% similar but in samples produced in different production facilities, suggesting a mutual source of contamination or a circulating strain. Two STEC strains exhibited resistance to streptomycin. Although the isolates presented a low resistance profile and no strain belonged to the "big 6" pathogenic group, the circulation of stx2-positive STEC strains in ready-to-eat products highlights the importance of epidemiological surveillance inside the Brazilian dairy chain.

Caracterização molecular de Listeria monocytogenes oriundas de cortes cárneos bovinos e de abatedouros frigoríficos de bovinos localizados no Distrito Federal, Brasil / Molecular characterization of Listeria monocytogenes from beef samples and cattle slaughterhouses located in the Federal District, Brazil

Este trabalho teve como objetivo realizar a detecção de cepas de Listeria monocytogenes de cortes cárneos bovinos bem como no ambiente de abatedouros frigoríficos localizados no Distrito Federal, promover a sorotipificação pela reação em cadeia da polimerase (PCR), realizar antibiograma e submeter às cepas à eletroforese de campo pulsado (Pulsed-field gel electrophoresis - PFGE). Foram analisados um total de 125 cortes cárneos bovinos, 45 amostras de swabs de carcaças e 43 amostras de swabs em que foram detectados 13 cepas de Listeria monocytogenes, sendo 11 em cortes cárneos bovinos e 2 swabs de ambiente em um abatedouro frigorifico. Não foram isoladas cepas de swabs de carcaça. Dentre as 13 cepas de Listeria monocytogenes foram encontradas seis cepas do sorotipo 4b, cinco do sorotipo 1/2c e duas cepas do sorotipo 1/2a. Dentre as 11 cepas de L. monocytogenes encontradas em cortes cárneos bovino, uma (9,1%) cepa apresentou resistência a eritromicina, outra (9,1%) cepa a gentamicina e outra a ciprofloxacina (9,1%) e todas as cepas (100%) apresentaram resistência ao Ác. Nalidíxico. Das duas (2) cepas oriundas de ralos de abatedouro frigorífico, todas (100%) apresentaram resistência ao Ác. Nalidíxico e a sulfonamidas. A análise por eletroforese de campo pulsante (PFGE) demonstrou 13 diferentes pulsotipos, em que foram agrupados em 3 diferentes grupos clonais, que coincidentemente se correlacionavam com os 3 diferentes sorotipos encontrados sugerindo uma ampla disseminação desses perfis no Distrito Federal.(AU)

The aim of the study was the analysis of Listeria monocytogenes strains in beef samples as well as slaughterhouse environment, located in the Federal District, promote serotyping by polymerase chain reaction (PCR), perform antibiotic susceptibility and submit the strains to Pulsed-field gel electrophoresis (PFGE). A total of 125 beef samples were analyzed, 45 samples of carcasses swabs and 43 swab samples. It detected 13 strains of Listeria monocytogenes, 11 in beef samples. and 2 in slaughterhouse environment. No carcass swabs strains were isolated. Among the 13 strains of L. monocytogenes six strains of serotype 4b were found, five serotype 1/2c and two strains of serotype 1/2a. Among the 11 strains of L. monocytogenes found in beef, one (9.1%) strain showed resistance to erythromycin, one (9.1%) strain to gentamicin, one to ciprofloxacin (9.1%) and all strains (100%) were resistant to nalidixic acid. The two strains coming from the slaughterhouse drains, all (100%) were resistant to nalidixic acid and Sulfonamides. The analysis by pulsed field gel electrophoresis (PFGE) showed 13 different pulsotypes; they were grouped into three different clonal groups, coincidentally correlated with the three different serotypes found, what suggests a widespread dissemination of these profiles in the Federal District, Brazil.(AU)