北部湾养殖牡蛎体内异养细菌数量及其耐药性研究

The number and antibiotic resistance of heterotrophic bacteria in Crassostrea hongkongensis in aquaculture areas of Beibu Gulf

为了探究北部湾养殖区域香港牡蛎(Crassostrea hongkongensis)体内的异养细菌和弧菌数量及其耐药概况变化,对不同养殖场牡蛎体内的异养细菌进行分离培养,并统计其数量,通过药敏纸片扩散等方法研究了细菌的耐药状况。结果显示:牡蛎在高死亡率养殖环境中体内的异养细菌[(8.6±0.4)×10^(6)CFU·g^(-1)]和弧菌[(9.5±0.4)×10^(5)CFU·g^(-1)]数量较高,在中死亡率环境中体内的异养细菌[(6.9±0.2)×10^(6)CFU·g^(-1)]和弧菌[(4.5±0.6)×10^(5)CFU·g^(-1)]数量次之,在低死亡率养殖环境中体内的异养细菌[(3.3±0.1)×10^(6)CFU·g^(-1)]和弧菌[(2.5±0.6)×10^(5)CFU·g^(-1)]数量最低。耐药细菌主要为革兰氏阴性菌,对β-内酰胺类(青霉素)、糖肽类(万古霉素)的耐药率较高,对四环素类(四环素、多西环素)的耐药率次之,对氨基糖苷类(链霉素、庆大霉素、妥布霉素、新霉素)、大环内酯类(红霉素)、喹诺酮类(诺氟沙星、环丙沙星、氧氟沙星、恩诺沙星)的耐药率较低。在高死亡率环境中牡蛎体内的多重耐药菌占79.7%,其耐药谱型(48种)较广;在中度死亡率环境中牡蛎体内的多重耐药菌占66.2%,其耐药谱型为30种;在低死亡率环境中牡蛎体内的多重耐药菌占58.4%,其耐药谱型为17种。本文探究了牡蛎死亡率与其体内异养细菌数量和细菌耐药性的关系,结果显示牡蛎在高死亡率环境中体内的耐药细菌数量多、耐药谱型较广,低死亡率环境中牡蛎体内的耐药细菌数量较少,异养细菌数量与牡蛎死亡率呈正相关关系,两者相关系数为0.996。

This study investigated the quantity and antibiotic resistance of heterotrophic bacteria in Crassostrea hongkongensis,which were collected from aquaculture zones with different mortality rates.Heterotrophic bacteria were cultivated and numbered,and their antibiotic resistance was explored by the Kirby-Bauer method.The results indicate that the highest number of heterotrophic bacteria[(8.6±0.4)×10^(6)CFU·g^(-1)]and Vibrio[(9.5±0.4)×105 CFU·g-1]occurred in the high-mortality farming zones.The medium number of heterotrophic bacteria[(6.9±0.2)×10^(6)CFU·g^(-1)]and Vibrio[(4.5±0.6)×10^(5)CFU·g^(-1)]occurred in the moderate-mortality farming zones.Heterotrophic bacteria[(3.3±0.1)×10^(6)CFU·g^(-1)]and Vibrio[(2.5±0.6)×10^(5)CFU·g^(-1)]had reached the least abundant in low-mortality farming areas.The antibiotic resistance happened mainly to gram-negative bacteria,especially with the highest resistance rate toβ-lactams(penicillin)and glycopeptides(vancomycin),and the second to tetracyclines(tetracycline,doxycycline).The lower resistance rates of antibiotics happened to aminoglycosides(streptomycin,gentamicin,tobramycin,neomycin),macrolides(erythromycin)and quinolones(norfloxacin,ciprofloxacin,ofloxacin,enrofloxacin).Multi-antibiotics-resistant bacteria accounted for 79.7%in high-mortality oysters,with a broad spectrum of antibiotic resistance(48 antibiotics).Multi-antibiotics-resistant bacteria accounted for 66.2%in medium-mortality oysters,with resistance to 30 antibiotics.Heterotrophic bacteria with multi-antibiotics resistance in oysters from the low-mortality area accounted for 58.4%,with resistance to 17 kinds of antibiotic-resistant spectrum.The antibiotic resistance and number of heterotrophic bacteria may be related to the death of oysters.The resistant bacteria of high-mortality oysters were large in number and broad in antibiotic resistance spectrum.Quantity of the antibiotic-resistant bacteria in oysters from the low-mortality area were lower.The results reveal that the number of heterotrophic bacteria is positively correlated with the mortality rate of oysters.