Basnet Ajaya, Chand Arun Bahadur, Bajracharya Sohani, Shrestha Mahendra Raj, Shrestha Shila, Tamang Basanta, Dulal Maina, Pokhrel Nayanum, Shrestha Lok Bahadur
Department of Medical Microbiology, Shi-Gan International College of Science and Technology, Tribhuvan University, Kathmandu, Nepal.
Department of Microbiology, Nepal Armed Police Force Hospital, Kathmandu, Nepal.
Am J Trop Med Hyg. 2024 Nov 19;112(2):346-354. doi: 10.4269/ajtmh.24-0276. Print 2025 Feb 5.
The likelihood of antimicrobial failure in COVID-19 patients with bacterial superinfection arises from both phenotypic (biofilms) and genotypic mechanisms. This cross-sectional study aimed to determine the inhibitory concentrations of quinolones-nalidixic acid, norfloxacin, ciprofloxacin, ofloxacin, and levofloxacin-in biofilm formers (minimum biofilm inhibitory concentration [MBIC]) and nonformers (minimum inhibitory concentration [MIC]) and correlate inhibitory concentrations with plasmid-mediated quinolone resistance (PMQR) genes in quinolone-resistant bacteria isolated from COVID-19 inpatients. Quinolone-resistant bacteria (n = 193), verified through disc diffusion, were tested for quinolone inhibitory concentrations using broth microdilution and biofilm formation using microtiter plate methods. The polymerase chain reaction was used to detect PMQR genes. Study variables were analyzed using SPSS v.17.0, with a significance level set at P <0.05. MIC-to-MBIC median fold increases for ciprofloxacin, ofloxacin, and levofloxacin were 128 (2-8,192), 64 (4-1,024), and 32 (4-512) in gram-positive cocci (GPC, n = 43), respectively, whereas they were 32 (4-8,192), 32 (4-2,048), and 16 (2-1,024) in fermentative gram-negative bacilli (F-GNB, n = 126) and 16 (4-4,096), 64 (2-64), and 16 (8-512) in nonfermentative gram-negative bacilli (NF-GNB, n = 24). In biofilm-forming F-GNB and NF-GNB, qnrB (10/32 versus 3/10), aac(6')-Ib-cr (10/32 versus 4/10), and qnrS (9/32 versus 0/10) genes were detected. A 32-fold median increase in the MIC-to-MBIC of ciprofloxacin was significantly (P <0.05) associated with qnrA in F-GNB and qnrS in NF-GNB. Biofilms formed by F-GNB and NF-GNB were significantly associated with the aac(6')-Ib-cr and qnrS genes, respectively. Nearly one-third of the superinfecting bacteria in COVID-19 patients formed biofilms and had at least one PMQR gene, thus increasing the need for quinolones at higher inhibitory concentrations.
新冠病毒感染合并细菌重叠感染患者出现抗菌治疗失败的可能性源于表型（生物膜）和基因型机制。本横断面研究旨在测定喹诺酮类药物（萘啶酸、诺氟沙星、环丙沙星、氧氟沙星和左氧氟沙星）对生物膜形成菌（最低生物膜抑制浓度[MBIC]）和非生物膜形成菌（最低抑菌浓度[MIC]）的抑制浓度，并将抑制浓度与从新冠住院患者中分离出的喹诺酮耐药菌中的质粒介导喹诺酮耐药（PMQR）基因相关联。通过纸片扩散法验证的喹诺酮耐药菌（n = 193），采用肉汤微量稀释法检测喹诺酮抑制浓度，采用微量滴定板法检测生物膜形成情况。聚合酶链反应用于检测PMQR基因。使用SPSS v.17.0分析研究变量，显著性水平设定为P <0.05。在革兰氏阳性球菌（GPC，n = 43）中，环丙沙星、氧氟沙星和左氧氟沙星的MIC至MBIC中位数增加倍数分别为128（2 - 8,192）、64（4 - 1,024）和32（4 - 512），而在发酵型革兰氏阴性杆菌（F - GNB，n = 126）中分别为32（4 - 8,192）、32（4 - 2,048）和16（2 - 1,024），在非发酵型革兰氏阴性杆菌（NF - GNB，n = 24）中分别为16（4 - 4,096）、64（2 - 64）和16（8 - 512）。在形成生物膜的F - GNB和NF - GNB中，检测到qnrB（10/32对3/10）、aac(6') - Ib - cr（10/32对4/10）和qnrS（9/32对0/10）基因。环丙沙星的MIC至MBIC中位数增加32倍与F - GNB中的qnrA和NF - GNB中的qnrS显著相关（P <0.05）。F - GNB和NF - GNB形成的生物膜分别与aac(6') - Ib - cr和qnrS基因显著相关。新冠患者中近三分之一的重叠感染细菌形成生物膜且至少有一个PMQR基因，因此需要更高抑制浓度的喹诺酮类药物。
