Iaconis J P, Sanders C C
Department of Medical Microbiology, Creighton University School of Medicine, Omaha, Nebraska 68178.
Antimicrob Agents Chemother. 1990 Jan;34(1):44-51. doi: 10.1128/AAC.34.1.44.
beta-Lactamases from Aeromonas hydrophila and A. sobria were purified and characterized. Both species produced beta-lactamases that were inducible by either cefoxitin or imipenem. These species were resistant to ampicillin and cephalothin but not imipenem. Isoelectric focusing of sonic extracts revealed one band at pI 8.0 and a second band at pI 7.0 for A. hydrophila. Likewise, A. sobria produced two bands, one at pI 8.4 and the other at pI 7.0. Two enzymes from each species were separated by flatbed electrofocusing gel and purified to homogeneity. The molecular weight of the pI 7.0 enzyme (A1) from both species was estimated to be 42,500, whereas the pI 8.0 (A2h) and 8.4 (A2s) enzymes of A. hydrophila and A. sobria had molecular weights of 31,500 and 35,000, respectively, on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The relative Vmax values for cephalothin, penicillin, and imipenem for these enzymes indicated that A1 was primarily a cephalosporinase while A2h and A2s were penicillinases highly active against carbapenems. A1 was susceptible to inhibition by cloxacillin, while the A2 enzymes were inhibited by clavulanic acid and EDTA and required zinc for activity. Thus, there appear to be two distinct inducible beta-lactamases in A. hydrophila and A. sobria that play an important role in the beta-lactam resistance of these species.
对嗜水气单胞菌和温和气单胞菌的β-内酰胺酶进行了纯化和特性鉴定。这两个菌种都产生可被头孢西丁或亚胺培南诱导的β-内酰胺酶。这些菌种对氨苄西林和头孢噻吩耐药，但对亚胺培南敏感。对嗜水气单胞菌超声提取物进行等电聚焦，在pI 8.0处显示一条带，在pI 7.0处显示第二条带。同样，温和气单胞菌产生两条带，一条在pI 8.4，另一条在pI 7.0。通过平板电聚焦凝胶分离每个菌种的两种酶，并纯化至均一。在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳上，两个菌种的pI 7.0酶（A1）分子量估计为42,500，而嗜水气单胞菌的pI 8.0（A2h）酶和温和气单胞菌的pI 8.4（A2s）酶分子量分别为31,500和35,000。这些酶对头孢噻吩、青霉素和亚胺培南的相对Vmax值表明，A1主要是一种头孢菌素酶，而A2h和A2s是对碳青霉烯类高度活跃的青霉素酶。A1对氯唑西林敏感，而A2酶被克拉维酸和EDTA抑制，且活性需要锌。因此，嗜水气单胞菌和温和气单胞菌中似乎存在两种不同的可诱导β-内酰胺酶，它们在这些菌种的β-内酰胺耐药性中起重要作用。
