Department of Microbiology, Sikkim Manipal University, Gangtok, Sikkim, India.
Medicine, Sikkim Manipal Institute of Medical Sciences, Sikkim Manipal University, Gangtok, Sikkim, India.
Indian J Med Res. 2023 Oct 1;158(4):439-446. doi: 10.4103/ijmr.ijmr_3470_21. Epub 2023 Sep 25.
Acinetobacter baumannii has emerged as a nosocomial pathogen with a tendency of high antibiotic resistance and biofilm production. This study aimed to determine the occurrence of A. baumannii from different clinical specimens of suspected bacterial infections and furthermore to see the association of biofilm production with multidrug resistance and expression of virulence factor genes in A. baumannii.
A. baumannii was confirmed in clinical specimens by the detection of the blaOXA-51-like gene. Biofilm production was tested by microtitre plate assay and virulence genes were detected by real-time PCR.
A. baumannii was isolated from a total of 307 clinical specimens. The isolate which showed the highest number of A. baumannii was an endotracheal tube specimen (44.95%), then sputum (19.54%), followed by pus (17.26%), urine (7.49%) and blood (5.86%), and <2 per cent from body fluids, catheter-tips and urogenital specimens. A resistance rate of 70-81.43 per cent against all antibiotics tested, except colistin and tigecycline, was noted, and 242 (78.82%) isolates were multidrug-resistant (MDR). Biofilm was detected in 205 (66.78%) with a distribution of 54.1 per cent weak, 10.42 per cent medium and 2.28 per cent strong biofilms. 71.07 per cent of MDR isolates produce biofilm (P<0.05). Amongst virulence factor genes, 281 (91.53%) outer membrane protein A (OmpA) and 98 (31.92%) biofilm-associated protein (Bap) were detected. Amongst 100 carbapenem-resistant A. baumannii, the blaOXA-23-like gene was predominant (96%), the blaOXA-58-like gene (6%) and none harboured the blaOXA-24-like gene. The metallo-β-lactamase genes blaIMP-1 (4%) and blaVIM-1(8%) were detected, and 76 per cent showed the insertion sequence ISAba1.
The majority of isolates studied were from lower respiratory tract specimens. The high MDR rate and its positive association with biofilm formation indicate the nosocomial distribution of A. baumannii. The biofilm formation and the presence of Bap were not interrelated, indicating that biofilm formation was not regulated by a single factor. The MDR rate and the presence of OmpA and Bap showed a positive association (P<0.05). The isolates co-harbouring different carbapenem resistance genes were the predominant biofilm producers, which will seriously limit the therapeutic options suggesting the need for strict antimicrobial stewardship and molecular surveillance in hospitals.
鲍曼不动杆菌已成为一种医院获得性病原体，具有高度抗生素耐药性和生物膜形成的倾向。本研究旨在确定不同疑似细菌感染临床标本中鲍曼不动杆菌的发生情况，并进一步观察生物膜形成与多药耐药性以及鲍曼不动杆菌毒力因子基因表达的相关性。
通过检测 blaOXA-51 样基因来确认临床标本中的鲍曼不动杆菌。通过微量滴定板测定法检测生物膜的形成，通过实时 PCR 检测毒力基因。
从总共 307 份临床标本中分离出鲍曼不动杆菌。检出鲍曼不动杆菌数量最多的标本是气管内管标本（44.95%），其次是痰（19.54%），然后是脓液（17.26%）、尿液（7.49%）和血液（5.86%），<2%来自体液、导管尖端和泌尿生殖道标本。除多粘菌素和替加环素外，所有检测的抗生素均出现 70-81.43%的耐药率，242（78.82%）株为多药耐药（MDR）。205 株（66.78%）检测到生物膜，分布为 54.1%弱、10.42%中、2.28%强。71.07%的 MDR 分离株产生生物膜（P<0.05）。在毒力因子基因中，检测到 281 株（91.53%）外膜蛋白 A（OmpA）和 98 株（31.92%）生物膜相关蛋白（Bap）。在 100 株碳青霉烯耐药鲍曼不动杆菌中，blaOXA-23 样基因占主导地位（96%），blaOXA-58 样基因（6%），无 blaOXA-24 样基因。检测到金属β-内酰胺酶基因 blaIMP-1（4%）和 blaVIM-1（8%），76%的菌株携带插入序列 ISAba1。
研究中的大多数分离株来自下呼吸道标本。高 MDR 率及其与生物膜形成的正相关性表明鲍曼不动杆菌在医院的传播。生物膜形成与 Bap 的存在无相关性，表明生物膜形成不受单一因素调节。MDR 率和 OmpA 和 Bap 的存在呈正相关（P<0.05）。同时携带不同碳青霉烯类耐药基因的分离株是主要的生物膜生产者，这将严重限制治疗选择，表明需要在医院进行严格的抗菌药物管理和分子监测。
