López A C, de Ortúzar R V M, Alippi A M
Unidad de Bacteriología, Centro de Investigaciones de Fitopatología, Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, La Plata, Argentina.
Rev Argent Microbiol. 2008 Oct-Dec;40(4):231-7.
The aim of this study was to investigate the presence of tetracycline and oxytetracycline resistance determinants in Bacillus cereus strains isolated from honey samples. Of a total of 77 isolates analyzed, 30 (39%) exhibited resistance to tetracyclines according to the results of a disk diffusion method. Resistant strains (n=30) were screened by PCR for the presence of the resistant determinants tetK, tetL, tetM, tetO, tetW, otrA and otrB and their MIC values for tetracycline, oxytetracycline and minocycline were assessed. According to the PCR results, 23 isolates (77%) presented at least one tetracycline or oxytetracycline resistance determinant. The tetK genotype was present in 10 isolates while the tetL, tetM, and otrA genotypes were present in 3, 2, and 5 isolates, respectively. In addition, 2 isolates of the tetK plus tetM genotype, 1 of the tetK plus tetL genotype, and 1 of the tetK plus otrA genotype were found. All isolates were tetW, tetO and otrB negatives. On the other hand, 7 isolates (23%) showed a tetracycline-resistant and/or minocycline-resistant phenotype (MIC) but did not carry any of the tet or otr determinants investigated in this study. This research has shown that B. cereus isolates from honey samples contain a variety of tetracycline and oxytetracycline resistance genes, including the tetK and tetL determinants which encode for efflux proteins, and tetM and otrA, which encode for ribosomal protection proteins. These findings indicate that strains isolated from honeys could represent a reservoir for tetracycline resistance genes. To our knowledge, this is the first report of tetracycline-resistant and oxytetracycline-resistant B. cereus strains carrying the tetK determinant, and also the first report of oxytetracycline-resistant and tetracycline-resistant Bacillus species carrying the otrA determinant.
本研究的目的是调查从蜂蜜样品中分离出的蜡样芽孢杆菌菌株中四环素和土霉素抗性决定因素的存在情况。根据纸片扩散法的结果，在总共分析的77株分离株中，有30株（39%）对四环素类药物表现出抗性。通过PCR对耐药菌株（n = 30）进行筛选，以检测耐药决定因素tetK、tetL、tetM、tetO、tetW、otrA和otrB的存在情况，并评估它们对四环素、土霉素和米诺环素的MIC值。根据PCR结果，23株分离株（77%）至少呈现一种四环素或土霉素抗性决定因素。tetK基因型存在于10株分离株中，而tetL、tetM和otrA基因型分别存在于3株、2株和5株分离株中。此外，还发现了2株tetK加tetM基因型、1株tetK加tetL基因型和1株tetK加otrA基因型的分离株。所有分离株的tetW、tetO和otrB均为阴性。另一方面，7株分离株（23%）表现出对四环素耐药和/或对米诺环素耐药的表型（MIC），但未携带本研究中检测的任何tet或otr决定因素。本研究表明，从蜂蜜样品中分离出的蜡样芽孢杆菌菌株含有多种四环素和土霉素抗性基因，包括编码外排蛋白的tetK和tetL决定因素，以及编码核糖体保护蛋白的tetM和otrA。这些发现表明，从蜂蜜中分离出的菌株可能是四环素抗性基因的储存库。据我们所知，这是携带tetK决定因素的耐四环素和耐土霉素蜡样芽孢杆菌菌株的首次报道，也是携带otrA决定因素的耐土霉素和耐四环素芽孢杆菌属的首次报道。
