Department of Microbiology and Immunology, Faculty of Biology, University of Bucharest, Bucharest, Romania.
Research Institute of the University of Bucharest (ICUB), Bucharest, Romania.
BMC Vet Res. 2021 Jan 26;17(1):52. doi: 10.1186/s12917-021-02770-8.
The present study aims the characterization of antibiotic resistance phenotypes and encoding genes in bacterial strains isolated from some Romanian aquatic fishery lowland salted lakes.
MATERIAL/METHODS: This study was conducted on 44 bacterial strains, mainly belonging to species used as microbiological indicators of fecal pollution isolated from four natural fishery lakes. All strains were tested for their antibiotic susceptibility by disk diffusion method. Simplex and multiplex PCR were performed to identify the β-lactams antibiotic resistance genes (bla, bla, bla, bla, bla, bla), sulfonamides (Sul1, Sul2), tetracyclines (TetA, TetB, TetC, TetD, TetM), aminoglycosides (aac3Ia), vancomycin (VanA, VanB, VanC), macrolides (ermA, ermB, ermC) as well as the plasmid-mediated quinolone resistance (PMQR) markers (QnrA, QnrB, QnrS), and class 1 integrons (Int1, drfA1-aadA1).
The Enterococcus spp. isolates exhibited phenotypic resistance to vancomycin (35 %) and macrolides (erythromycin) (75 %); from the vancomycin - resistant strains, 5 % harboured VanA (E. faecalis), while the erythromycin resistant isolates were positive for the ermA gene (E. faecalis - 10 %, E. faecium - 5 %). The Gram- negative rods (GNR) exhibited a high level of resistance to β-lactams: cefuroxime (63 %), cefazolin (42 %), ceftriaxone (8 %), ceftazidime and aztreonam (4 % each). The genetic determinants for beta-lactam resistance were represented by bla (33 %), bla and bla (8.33 %) genes. The resistance to non-β-lactam antibiotics was ascertained to the following genes: quinolones (QnrS - 4.16 %); sulfonamides (Sul1-75 %, Sul2-4.16 %); aminoglycosides (aac3Ia - 4.16 %); tetracyclines (tetA - 25 %, tetC - 15 %). The integrase gene was found in more than 50 % of the studied strains (58.33 %).
The cultivable aquatic microbiota from fishery lakes is dominated by enterococci and Enterobacterales strains. The GNR strains exhibited high levels of β-lactam resistance mediated by extended spectrum beta-lactamases and metallo-β-lactamases. The Enterococcus sp. isolates were highly resistant to macrolides and vancomycin. The high level and diversity of resistance markers, correlated with a high frequency of integrons is suggesting that this environment could act as an important reservoir of antibiotic resistance genes with a great probability to be horizontally transmitted to other associated species from the aquatic sediments microbiota, raising the potential zoonotic risk for fish consumers.
本研究旨在对从罗马尼亚一些淡水渔业低盐湖泊中分离的细菌菌株的抗生素耐药表型和编码基因进行表征。
材料/方法：本研究共检测了 44 株细菌，主要为微生物指示菌，从四个天然渔业湖中分离得到。所有菌株均采用纸片扩散法检测其抗生素敏感性。采用单重和多重 PCR 检测β-内酰胺类抗生素耐药基因（blaTEM，blaCTX-M，blaOXA，blaSHV，blaPER，blaVEB）、磺胺类（Sul1，Sul2）、四环素类（TetA，TetB，TetC，TetD，TetM）、氨基糖苷类（aac3Ia）、万古霉素（VanA，VanB，VanC）、大环内酯类（ermA，ermB，ermC）以及质粒介导的喹诺酮耐药（PMQR）标记物（QnrA，QnrB，QnrS）和 1 类整合子（Int1，drfA1-aadA1）。
肠球菌属分离株对万古霉素（35%）和大环内酯类（红霉素）（75%）表现出表型耐药；耐万古霉素的菌株中，5%携带 VanA（粪肠球菌），而红霉素耐药株 ermA 基因阳性（粪肠球菌-10%，屎肠球菌-5%）。革兰氏阴性杆菌（GNR）对β-内酰胺类药物高度耐药：头孢呋辛（63%）、头孢唑林（42%）、头孢曲松（8%）、头孢他啶和头孢噻肟（各 4%）。β-内酰胺类耐药的遗传决定因素由 blaTEM（33%）、blaCTX-M 和 blaOXA（8.33%）基因表示。非β-内酰胺类抗生素耐药的确定与以下基因有关：喹诺酮类（QnrS-4.16%）；磺胺类（Sul1-75%，Sul2-4.16%）；氨基糖苷类（aac3Ia-4.16%）；四环素类（tetA-25%，tetC-15%）。研究菌株中超过 50%（58.33%）携带整合酶基因。
渔业湖泊中的可培养水生菌群主要由肠球菌和肠杆菌科菌株组成。GNR 菌株对扩展谱β-内酰胺酶和金属β-内酰胺酶介导的β-内酰胺类抗生素表现出高水平耐药。肠球菌属分离株对大环内酯类和万古霉素高度耐药。高耐药标志物水平和多样性，与高频率的整合子相关，表明该环境可能是抗生素耐药基因的重要储存库，极有可能通过水平基因转移到水生沉积物微生物群中的其他相关物种，从而增加鱼类消费者的潜在人畜共患病风险。
