Sharma Swati, Singh Kamal, Chaurasiya Ashish, Banerjee Tuhina, Singh Royana, Yadav Ghanshyam, Kumar Ashok
Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, 221005, India.
Multidisciplinary Research Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India.
BMC Microbiol. 2025 Jan 11;25(1):13. doi: 10.1186/s12866-024-03727-1.
Carbapenem resistant Acinetobacter baumannii has evolved as the most troublesome microorganism with multiple virulence factors. Biofilm formation, porins, micronutrient capturing mechanism and quorum sensing, provide protection against desiccation, host-pathogen killing and enhance its persistence. The conservation of these factors between colonizing and pathogenic carbapenem resistant A. baumannii has been barely investigated. We studied biofilm formation, desiccation survival, motility and hemolysis in pathogenic carbapenem resistant A. baumannii and colonizer carbapenem resistant A. baumannii from the hospital environment. The virulent genes pgaA, csuE, bap, ompA, abaI, pilA and bauA were detected by simplex-PCR and Quantitative Real-Time PCR was done for expressional studies. In-vivo survival percentage was studied by Galleria mellonella (wax moth) killing assay. Phenotypic characterization revealed that the biofilm formation and desiccation survival proportion was significantly higher in colonizer carbapenem resistant A. baumannii (p < 0.05). Twitching motility was found comparable (mean 0.5 to 1.5 cm). Surface associated motility varied widely. None showed hemolysis. The csuE, bap, ompA, abaI, pilA and bauA genes were detected in almost all the pathogenic and colonizer carbapenem resistant A. baumannii isolates while none harboured pgaA gene. The expression of bap, ompA and bauA gene was found significantly higher in pathogenic carbapenem resistant A. baumannii while expression of csuE and abaI gene was comparable in both. Overexpression of pilA gene was seen in those with higher surface associated motility. Pathogenic carbapenem resistant A. baumannii showed significantly higher pathogenicity in-vivo, as 100% of larvae died on 4th day post-infection. In conclusion high level expression of outer membrane proteins (ompA) and siderophores is significantly associated with the pathogenicity in carbapenem resistant A. baumannii isolated from infections, which can be a differentiating point from the colonizers. CLINICAL TRIAL: Not Applicable.
耐碳青霉烯鲍曼不动杆菌已演变成具有多种毒力因子的最棘手微生物。生物膜形成、孔蛋白、微量营养素捕获机制和群体感应可提供抗干燥、宿主病原体杀灭的保护作用，并增强其持久性。在定植性和致病性耐碳青霉烯鲍曼不动杆菌之间，这些因子的保守性几乎未得到研究。我们研究了来自医院环境的致病性耐碳青霉烯鲍曼不动杆菌和定植性耐碳青霉烯鲍曼不动杆菌的生物膜形成、干燥存活、运动性和溶血情况。通过单重PCR检测毒力基因pgaA、csuE、bap、ompA、abaI、pilA和bauA，并进行定量实时PCR以进行表达研究。通过大蜡螟（蜡蛾）杀伤试验研究体内存活百分比。表型特征显示，定植性耐碳青霉烯鲍曼不动杆菌的生物膜形成和干燥存活比例显著更高（p < 0.05）。发现颤动运动性相当（平均0.5至1.5厘米）。表面相关运动性差异很大。均未显示溶血。几乎所有致病性和定植性耐碳青霉烯鲍曼不动杆菌分离株中均检测到csuE、bap、ompA、abaI、pilA和bauA基因，而无一携带pgaA基因。发现bap、ompA和bauA基因在致病性耐碳青霉烯鲍曼不动杆菌中的表达显著更高，而csuE和abaI基因在两者中的表达相当。在具有较高表面相关运动性的菌株中观察到pilA基因的过表达。致病性耐碳青霉烯鲍曼不动杆菌在体内显示出显著更高的致病性，因为100%的幼虫在感染后第4天死亡。总之，外膜蛋白（ompA）和铁载体的高水平表达与从感染中分离出的耐碳青霉烯鲍曼不动杆菌的致病性显著相关，这可能是与定植菌的一个区别点。临床试验：不适用。
