RESUMO
The aim of the present study was to investigate the phenotypic and genotypic antimicrobial resistance and the transferability of resistance markers in 87 lactic acid bacterial strains recovered from fermented milk products obtained from different areas of China. The isolates were identified as 21 Lactobacillus bulgaricus, 8 Lactobacillus casei, 6 Lactobacillus rhamnosus, 3 Lactobacillus paracasei, 2 Lactobacillus acidophilus, and 47 Streptococcus thermophilus strains. High levels of intrinsic resistance were revealed among the tested species. The following resistance genes were detected in strains isolated from fermented milk products: tet(M) in two L. bulgaricus and two S. thermophilus isolates, strA and strB in nine and seven S. thermophilus isolates, respectively; sul1 in six L. bulgaricus and seven S. thermophilus isolates, sul2 in one S. thermophilus isolate, aac(6')-aph(2â³) in two L. bulgaricus isolates, and aph(3â³)-II and aph(3â³)-III in one S. thermophilus and two L. bulgaricus isolates, respectively. Transfer of the monitored antibiotic resistance genes was not observed in the filter mating assays of this study. To our knowledge, the strA, strB, sul1, sul2, and aph(3â³)-II genes in S. thermophilus, and the sul1 and aac(6')-aph(2â³) genes in L. bulgaricus were identified for the first time. These results indicate the potential risks posed by lactic acid bacteria (LAB) in fermented milk products in expanding the antibiotic resistance gene reservoir and transferring antibiotic resistance genes among bacteria. Further investigations are required to identify the potential sources of contamination and the dissemination routes of antibiotic resistance genes among LAB in fermented milk products.
Assuntos
Antibacterianos/farmacologia , Produtos Fermentados do Leite/microbiologia , Farmacorresistência Bacteriana/genética , Lactobacillus/efeitos dos fármacos , Streptococcus thermophilus/efeitos dos fármacos , China , Genes Bacterianos/genética , Lactobacillus/genética , Lactobacillus/isolamento & purificação , Testes de Sensibilidade Microbiana , Reação em Cadeia da Polimerase , Streptococcus thermophilus/genética , Streptococcus thermophilus/isolamento & purificaçãoRESUMO
The expression of efflux pump gene lde in ciprofloxacin resistant (Cip(R) ) and susceptible strains of Listeria monocytogenes collected from retail food samples was investigated. For two Cip(R) strains, the MICs of ciprofloxacin decreased four- to eightfold in the presence of reserpine; however, no significant alterations were observed with naturally sensitive isolates. Overexpression of the lde gene induced by ciprofloxacin was observed in two resistant isolates. The present findings indicate that expression of lde and the MICs of ciprofloxacin are well correlated with the presence and absence of reserpine, suggesting that Lde might be involved in ciprofloxacin resistance of L. monocytogenes.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Antibacterianos/farmacologia , Ciprofloxacina/farmacologia , Farmacorresistência Bacteriana , Microbiologia de Alimentos , Expressão Gênica , Listeria monocytogenes/efeitos dos fármacos , Listeria monocytogenes/genética , Transportadores de Cassetes de Ligação de ATP/biossíntese , Perfilação da Expressão Gênica , Humanos , Listeria monocytogenes/isolamento & purificação , Testes de Sensibilidade MicrobianaRESUMO
A total of 81 Salmonella isolates from retail meats and seafood in Hebei province, China, were assayed for the presence of and horizontal transfer of class 1 integrons. By the PCR screening for the integrons, class 1 integron was detected from strains in serotypes of Derby, Indiana, London and Choleraesuis, which were isolated from pork, chicken or seafood; however, two isolates contained the empty integron that lacked the resistance cassette, a potential hotspot for development of the multidrug resistance. In contrast, two other isolates had the antibiotic resistance gene cassettes within the class 1 integron, which were dfrA1-aadA1 and aadB-cmlA, respectively. The conjugation experiments demonstrated the plasmid-mediated transfer of the class 1 integrons. Furthermore, each of the integrons was transmitted to Streptococcus mutans via natural gene transformation. These findings suggest the possible transfer of class 1 integrons from foodborne pathogens to human residential bacteria via horizontal gene transfer.
