Ratna A K, Menon I, Kapur I, Kulkarni R
Department of Microbiology, K.B.N. Institute of Medical Sciences, Karnataka, India.
Indian J Med Res. 2003 Jul;118:29-32.
BACKGROUND & OBJECTIVES: AmpC beta-lactamases confer resistance to a wide variety of beta-lactam drugs except for cefepime, cefpirome and carbapenems. They are known to be responsible for nosocomial outbreaks, therapeutic failures and multidrug resistance. Although reported with increasing frequency the true rate of occurrence of these beta-lactamases in Enterobacteriaceae is not known. Hence the present study was undertaken to determine the occurrence of AmpC enzymes among clinical isolates.
A total of 520 consecutive, non-repeat clinical isolates were included in the present study. Twenty eight strains resistant to cefoxitin were tested for AmpC beta-lactamases by the modified 3-dimensional extract method. Isolates harbouring AmpC beta-lactamases were tested for inducible beta-lactamases by disc diffusion.
Sixteen (3.3%) isolates were positive for AmpC beta-lactamases. Based on the species 9 (3.3%) Escherichia coli, 4 (2.2%) Klebsiella pneumoniae, 2 (5%) Citrobacter freundii and 1 (5.5%) isolate of Enterobacter aerogenes harboured AmpC enzymes. Nine (56.3%) of AmpC harbouring strains, were urinary isolates. All the isolates were sensitive to imipenem and variably sensitive to aminoglycosides and co-trimoxazole.
INTERPRETATION & CONCLUSION: Our findings document the presence of AmpC enzymes in this region. Hence AmpC beta-lactamase detection should be undertaken in clinical isolates showing resistance to broad-spectrum cephalosporins.
AmpCβ-内酰胺酶可使细菌对除头孢吡肟、头孢匹罗和碳青霉烯类以外的多种β-内酰胺类药物产生耐药性。已知其与医院感染暴发、治疗失败及多重耐药有关。尽管此类β-内酰胺酶的报道日益增多，但肠杆菌科细菌中这些β-内酰胺酶的实际发生率尚不清楚。因此开展本研究以确定临床分离株中AmpC酶的发生率。
本研究共纳入520株连续的、非重复的临床分离株。对28株对头孢西丁耐药的菌株采用改良三维提取法检测AmpCβ-内酰胺酶。对携带AmpCβ-内酰胺酶的分离株采用纸片扩散法检测诱导型β-内酰胺酶。
16株（3.3%）分离株AmpCβ-内酰胺酶检测呈阳性。基于菌种，9株（3.3%）大肠埃希菌、4株（2.2%）肺炎克雷伯菌、2株（5%）弗劳地枸橼酸菌和1株（5.5%）产气肠杆菌携带AmpC酶。携带AmpC酶的菌株中有9株（56.3%）为尿液分离株。所有分离株对亚胺培南敏感，对氨基糖苷类和复方新诺明的敏感性各异。
我们的研究结果证明了该地区存在AmpC酶。因此，对于对广谱头孢菌素耐药的临床分离株应进行AmpCβ-内酰胺酶检测。
