Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, 44613, Nepal.
Upendra Devkota Memorial National Institute of Neurological and Allied Sciences, Bansbari, Kathmandu, 44600, Nepal.
BMC Microbiol. 2023 May 25;23(1):153. doi: 10.1186/s12866-023-02906-w.
INTRODUCTION: Pseudomonas aeruginosa is an opportunistic pathogen, which causes healthcare-associated infections in immunosuppressed patients. They exhibit resistance to multiple classes of antibiotics via various mechanisms such as the over-expression of efflux pumps, decreased production of the outer membrane protein (D2 porin), over-expression of the chromosomally encoded AmpC cephalosporinase, modification of drugs, and mutation(s) at the target site of the drug. The bacteria also develop antibiotic resistance through the acquisition of resistance genes carried on mobile genetic elements. Limited data on phenotypic as well as genotypic characterization of MDR P. aeruginosa in Nepal infers the needs for this study. This study was carried out to determine the prevalence rate of metallo-β-lactamase (MBL-producer) as well as colistin resistant multidrug resistant (MDR) P. aeruginosa in Nepal and also to detect MBL, colistin resistance, and efflux pump encoding genes i.e. bla, mcr-1 and MexB respectively in MDR P. aeruginosa isolated from clinical samples. METHODS/METHODOLOGY: A total of 36 clinical isolates of P. aeruginosa were collected. All bacterial isolates were phenotypically screened for antibiotic susceptibility using Kirby Bauer Disc Diffusion method. All the multidrug resistant P. aeruginosa were phenotypically screened for MBL producer by Imipenem-EDTA combined disc diffusion test (CDDT). Similarly, MIC value for colistin was also determined by broth microdilution method. Genes encoding carbapenemase (bla), colistin resistant (mcr-1) and efflux pump activity (MexB) were assayed by PCR. RESULTS: Among 36 P. aeruginosa, 50% were found to be MDR among which 66.7% were found to be MBL producer and 11.2% were found to be colistin resistant. Among MDR P. aeruginosa, 16.7%, 11.2% and 94.4% were found to be harbouring bla, mcr-1 and MexB genes respectively. CONCLUSION: In our study, carbapenemase production (encoded by bla), colistin resistant enzyme production (encoded by mcr-1), and expression of efflux pump (encoded by MexB) are found to be one of the major causes of antibiotic resistance in P. aeruginosa. Therefore, periodic phenotypic as well as genotypic study in Nepal on P. aeruginosa would provide the scenario of resistance pattern or mechanisms in P. aeruginosa. Furthermore, new policies or rules can be implemented in order to control the P. aeruginosa infections.
简介：铜绿假单胞菌是一种机会致病菌，会导致免疫功能低下的患者发生医院获得性感染。该细菌通过多种机制对多种类别的抗生素表现出耐药性，这些机制包括外排泵的过度表达、外膜蛋白（D2 孔道蛋白）产量降低、染色体编码的 AmpC 头孢菌素酶过度表达、药物修饰以及药物靶位的突变等。此外，细菌还可以通过获得携带在可移动遗传元件上的耐药基因来产生抗生素耐药性。由于尼泊尔对铜绿假单胞菌的多药耐药（MDR）表型和基因型特征的了解有限，因此需要开展这项研究。本研究旨在确定尼泊尔产金属β-内酰胺酶（MBL-产生菌）和多粘菌素耐药 MDR 铜绿假单胞菌的流行率，并检测从临床样本中分离出的 MDR 铜绿假单胞菌中的 MBL、多粘菌素耐药和外排泵编码基因，即 bla、mcr-1 和 MexB。
方法/方法论：共收集 36 株铜绿假单胞菌临床分离株。使用 Kirby Bauer 纸片扩散法对所有细菌分离株进行表型药敏试验筛选。使用亚胺培南-EDTA 联合纸片扩散试验（CDDT）对所有 MDR 铜绿假单胞菌进行表型筛选，以确定 MBL 产生菌。同样，通过肉汤微量稀释法确定多粘菌素的 MIC 值。通过 PCR 检测碳青霉烯酶（bla）、多粘菌素耐药（mcr-1）和外排泵活性（MexB）的编码基因。
结果：在 36 株铜绿假单胞菌中，有 50%为 MDR 菌，其中 66.7%为 MBL 产生菌，11.2%为多粘菌素耐药菌。在 MDR 铜绿假单胞菌中，分别有 16.7%、11.2%和 94.4%携带 bla、mcr-1 和 MexB 基因。
结论：在本研究中，碳青霉烯酶的产生（由 bla 编码）、多粘菌素耐药酶的产生（由 mcr-1 编码）和外排泵的表达（由 MexB 编码）是铜绿假单胞菌产生抗生素耐药性的主要原因之一。因此，在尼泊尔定期进行铜绿假单胞菌的表型和基因型研究，可以提供铜绿假单胞菌耐药模式或机制的情况。此外，还可以实施新的政策或规则来控制铜绿假单胞菌感染。
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