The freshwater aquiculture industry has developed rapidly in China. As a result, China has become the largest producer of freshwater cultured fish in the world. However, production is threatened by Aeromonas hy-drophila, a widely distributed freshwater bacterial pathogen that is thought to cause disease in a range of aquatic animals. For example, A. Hydrophila is thought to cause bacterial septicemia in fish and red abdominal shell diseases in soft-shelled turtles. Outbreaks of A. Hydrophila have resulted in significant economic losses to the aqua-culture industry. In addition, A. Hydrophila is a zoonotic pathogen, sometimes causing gastroenteritis and septicemia in humans. Our objective was to document the epidemiological characteristics of pathogenic A. Hydrophila to provide insight into potential measures to prevent and control infections. We genotyped pathogenic Aeromonas hydrophila strains collected from a variety of sources, determined their drug susceptibility, and evaluated the relationship between genotype and antimicrobial resistance patterns. We used enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR to genotype SO strains of Aeromonas hydrophila collected from freshwater culture sites in Shanghai, Zhejiang, Jiangsu, Jiangxi, Hubei, and Guangdong. ERIC-PCR is a more rapid, efficient, and accurate molecular typing method than the traditional serotyping methods. In addition, we evaluated the susceptibility of each isolate to 12 antibacterial drugs and determined the relationship between the genotype and the antimicrobial resistance pattern. We identified 12 special genotypes (Ⅰ-Ⅻ) from the 50 isolates. Among these, genotype Ⅶ was the dominant genotype, consisting of 14 strains, whereas genotype Ⅲ and X contained only one strain. All strains were resistant to ampicillin and 98% of the strains were resistant to cefalexin. However, >94% of the strains were susceptible to aminoglycosides and quinolones. We identified 9 patterns of drug-resistance: AMP, CX/AMP, CX/AMP/POL, CX/AMP/SMZ, CX/AMP/NM, CX/AMP/SMZ/POL, CX/AMP/SMZ/POL/GM, CX/AMP/ SMZ/LOM/ENR, and CX/AMP/SMZ/LOM/ENR/OF/LEV. The twelve strain genotypes shared a common pattern of drug resistance (CX/AMP/POL). Similarly, the majority of genotypes within strain II and XI shared a common pattern of drug resistance (CX/AMP/SMZ). The drug-resistant pattern of most genotypes within strains IV, VI, and VIII was CX/AMP and for strain X the pattern was CX/AMP/NM. Thus, our results suggest that there is likely a correlation between the genotype and drug-resistance among A. Hydrophila strains.%以质控菌株ATCC7966为对照,采用ERIC-PCR方法对49株分别采集于中国浙江、江苏、江西、广东、湖北、上海等主要淡水养殖区的致病性嗜水气单胞菌(Aeromonas hydrophila)进行了基因分型,并分析了嗜水气单胞菌对12种抗生素的耐药模式,探讨了嗜水气单胞菌的基因型与区域性分布及其耐药性的关联性.实验结果表明,50株受试嗜水气单胞菌菌株可分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、V、Ⅵ、Ⅶ、Ⅷ、Ⅸ、X、Ⅺ、Ⅻ这12个基因型,其中Ⅷ型菌株最多,Ⅲ型和X型菌株最少.此外,50株受试菌株对氨苄青霉素(AMP)的耐药率高达100％,对头孢氨苄(CX)的耐药率高达98％,94％以上的菌株对氨基糖苷类及喹诺酮类抗生素未产生耐药性.受试菌株对12种抗生素呈现出AMP、CX/AMP、CX/AMP/POL(多黏菌素)、CX/AMP/SMZ(复方新诺明)、CX/AMP/NM(新霉素)、CX/AMP/SMZ/POL、CX/AMP/SMZ/POL/GM(庆大霉素)、CX/AMP/SMZ/LOM(洛美沙星)/ENR(恩诺沙星)、CX/AMP/SMZ/LOM/ENR/OF(氧氟沙星)/LEV(左氟沙星)这9种不同的耐药模式,其中Ⅻ型菌株的耐药谱均为CX/AMP/POL型,Ⅱ型和Ⅺ型菌株的耐药谱多为CX/AMP/SMZ型,Ⅳ型、Ⅵ型和Ⅷ型菌株的耐药谱多为CX/AMP型,X型菌株的耐药谱为CX/AMP/NM型.据此推测,嗜水气单胞菌基因型与耐药性可能存在一定的相关性.
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