We investigated the numbers of planktonic and biofilm cells and the expression levels of genes encoding efflux pumps and biofilm-related proteins in 10 clinical isolates of multi-drug resistant Acinetobacter baumannii (MDRA) as well as in its standard strain ATCC 19606 in the presence of colistin (CST), polymyxin B (PMB), minomycin (MIN), and tigecycline (TGC) at their respective sub-MICs. The number of planktonic and biofilm cells of ATCC 19606 decreased in the presence of all aforementioned antibiotics in a dose-dependent manner. Cell number also decreased in two representative MDRA strains, R2 and R3, in the presence of MIN and TGC in a dose-dependent manner. In contrast, the number of biofilm cells in these two strains increased in the presence of CST, while they increased significantly in the presence of PMB in R2 only. Pearson correlation analysis revealed that the number of biofilm cells was positively and significantly correlated with the mRNA levels of genes encoding efflux pumps (adeB and adeG) and autoinducer synthase (abaI) in strain R2 and adeB, adeG, adeJ, poly-acetyl-glucosamine-porin (pgaA), and abaI in strain R3 in the presence of CST. It was positively and significantly correlated with the mRNA levels of genes encoding adeB in strain R2 and an outer membrane protein A (ompA) and biofilm-associated protein (bap) in strain R3 in the presence of PMB. These results provide valuable insights into the biofilm formation potency of clinical isolates of MDRA that depends on efflux pumps and biofilm-related genes and its regulation by antibiotics.

我们调查了多药耐药鲍曼不动杆菌的10种临床分离株中浮游生物和生物膜细胞的数量以及编码外排泵和生物膜相关蛋白的基因的表达水平（MDRA）以及其标准菌株ATCC 19606中存在大肠菌素（CST），多粘菌素B（PMB），米霉素（MIN）和替加环素（TGC）的情况下，它们各自的子MIC都存在。在所有上述抗生素的存在下，ATCC 19606的浮游和生物膜细胞数量以剂量依赖性方式减少。在MIN和TGC存在下，两种代表性的MDRA菌株R2和R3中的细胞数也呈剂量依赖性。相反，这两个菌株中的生物膜细胞数量在CST存在下增加，而仅在R2中在PMB存在下它们显着增加。皮尔森（Pearson）相关分析显示，生物膜细胞的数量与外排泵编码基因（adeB和adeG）的mRNA水平正相关，且显着相关。）和R2菌株中的自诱导合成酶（abaI），以及在CST存在的情况下R3菌株中的adeB，adeG，adeJ，聚乙酰氨基葡萄糖-孔蛋白（pgaA）和abaI。在存在PMB的情况下，它与R2菌株中编码adeB的基因的mRNA水平以及R3菌株中的外膜蛋白A（ompA）和生物膜相关蛋白（bap）呈正相关。这些结果为依赖于外排泵和生物膜相关基因的MDRA临床分离株的生物膜形成潜能提供了有价值的见解，并通过抗生素对其进行调节。