β-lactamase-producing Gram-negative bacteria in an intensive care unit in southern Brazil

ABSTRACT The present study evaluated the antimicrobial susceptibility profile, β-lactamase production, and genetic diversity of Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter spp. using phenotypic identification, antimicrobial susceptibility testing, and β-lactamase phenotypic detection. Isolates were obtained from patients in an intensive care unit in a hospital in southern Brazil. Bacterial genomic DNA was extracted, followed by the genotypic detection of carbapenemases and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). Fifty-six isolates (26 Klebsiella pneumoniae, five Escherichia coli, three Enterobacter aerogenes, nine P. aeruginosa, and 13 Acinetobacter spp.) were evaluated. The phenotypic extended spectrum β-lactamase (ESBL) test was positive in 53.8% of the K. pneumoniae isolates, 100.0% of the E. coli isolates, and 100.0% of the E. aerogenes isolates. Phenotypic and genotypic testing of K. pneumoniae carbapenemase (KPC) was positive in 50.0% of the K. pneumoniae isolates. Phenotypic and genotypic testing showed that none of the P. aeruginosa or Acinetobacter spp. isolates were positive for metallo- β-lactamase (MBL). The bla OXA gene was detected only in Acinetobacter spp. The lowest genetic diversity, determined by ERIC-PCR, was observed among the KPC-producing K. pneumoniae isolates and OXA-producing Acinetobacter spp. isolates, indicating the inadequate dissemination control of multidrug-resistant bacteria in this hospital environment.摘要 本研究通过表型鉴定、抗菌药物敏感性试验以及β-内酰胺酶表型检测方法，对肠杆菌科、铜绿假单胞菌（Pseudomonas aeruginosa）以及不动杆菌属（Acinetobacter spp.）的抗菌药物敏感性谱、β-内酰胺酶产生情况与遗传多样性进行了评估。菌株分离自巴西南部某医院重症监护病房的患者样本。研究提取细菌基因组DNA后，对碳青霉烯酶进行基因型检测，并采用肠杆菌科基因间重复一致序列-聚合酶链反应（enterobacterial repetitive intergenic consensus-polymerase chain reaction, ERIC-PCR）进行分析。本研究共评估了56株菌株：其中肺炎克雷伯菌（Klebsiella pneumoniae）26株、大肠埃希菌（Escherichia coli）5株、产气肠杆菌（Enterobacter aerogenes）3株、铜绿假单胞菌9株以及不动杆菌属13株。表型超广谱β-内酰胺酶（extended spectrum β-lactamase, ESBL）检测结果显示，53.8%的肺炎克雷伯菌菌株、100.0%的大肠埃希菌菌株以及100.0%的产气肠杆菌菌株呈阳性。肺炎克雷伯菌碳青霉烯酶（Klebsiella pneumoniae carbapenemase, KPC）的表型与基因型联合检测结果显示，50.0%的肺炎克雷伯菌菌株呈阳性。表型与基因型联合检测结果表明，所有铜绿假单胞菌与不动杆菌属菌株的金属β-内酰胺酶（metallo-β-lactamase, MBL）检测均呈阴性。bla OXA基因仅在不动杆菌属菌株中被检出。通过ERIC-PCR分析可知，产KPC的肺炎克雷伯菌菌株与产OXA的不动杆菌属菌株的遗传多样性最低，提示该医院环境中多重耐药菌的传播控制措施存在不足。