Heydari Samira, Eftekhar Fereshteh
Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, IR Iran.
Jundishapur J Microbiol. 2015 Mar 21;8(3):e15514. doi: 10.5812/jjm.15514. eCollection 2015 Mar.
Pseudomonas aeruginosa is an important nosocomial pathogen characterized by its innate resistance to multiple antimicrobial agents. Plasmid-mediated drug resistance also occurs by the production of extended-spectrum β-lactamases (ESBL), metallo β-lactamases (MBL), and AmpC β-lactamases. Another important factor for establishment of chronic infections by P. aeruginosa is biofilm formation mediated by the psl gene cluster.
The aim of this study was to evaluate biofilm formation and presence of the pslA gene in burn isolates of P. aeruginosa as well as the association of antibiotic resistance, MBL, ESBL and AmpC β-lactamase production with biofilm formation among the isolates.
Sixty-two burn isolates of P. aeruginosa were obtained from Shahid Motahari Hospital in Tehran from August to October 2011. Antibiotic susceptibility was determined by the disc diffusion assay. MBL, AmpC and ESBL production were screened using the double disc synergy test, AmpC disc test and combined disc diffusion assay, respectively. The potential to form biofilm was measured using the microtiter plate assay and pslA gene was detected using specific primers and PCR.
Biofilm formation was observed in 43.5% of the isolates, of which 66.7% produced strong and 33.3% formed weak biofilms. All biofilm-positive and 14.2% of biofilm-negative isolates harbored the pslA gene. MBL, AmpC and ESBL production were significantly higher in the biofilm-positive isolates (70.3%, 62.9% and 33.3%, respectively) compared to the biofilm-negative strains (31.4%, 34.2% and 20%, respectively). Overall, 19 isolates (30.6%) co-produced MBL and AmpC, among which the majority were biofilm-positive (63.1%). Finally, four isolates (6.4%) had all three enzymes, of which 3 (75%) produced biofilm.
Biofilm formation (both strong and weak) strongly correlated with pslA gene carriage. Biofilm formation also correlated with MBL and AmpC β-lactamase production. More importantly, multiple-β-lactamase phenotype was associated with formation of strong biofilms.
铜绿假单胞菌是一种重要的医院病原体，其特点是对多种抗菌药物具有天然耐药性。质粒介导的耐药性也可通过产生超广谱β-内酰胺酶（ESBL）、金属β-内酰胺酶（MBL）和AmpCβ-内酰胺酶而发生。铜绿假单胞菌建立慢性感染的另一个重要因素是由psl基因簇介导的生物膜形成。
本研究旨在评估铜绿假单胞菌烧伤分离株中生物膜的形成及pslA基因的存在情况，以及分离株中抗生素耐药性、MBL、ESBL和AmpCβ-内酰胺酶产生与生物膜形成之间的关联。
2011年8月至10月从德黑兰的沙希德·莫塔哈里医院获得62株铜绿假单胞菌烧伤分离株。采用纸片扩散法测定抗生素敏感性。分别使用双纸片协同试验、AmpC纸片试验和联合纸片扩散试验筛选MBL、AmpC和ESBL的产生情况。使用微量滴定板试验测定生物膜形成潜力，并使用特异性引物和PCR检测pslA基因。
43.5%的分离株观察到生物膜形成，其中66.7%产生强生物膜，33.3%形成弱生物膜。所有生物膜阳性分离株和14.2%的生物膜阴性分离株携带pslA基因。与生物膜阴性菌株（分别为31.4%、34.2%和20%）相比，生物膜阳性分离株中MBL、AmpC和ESBL的产生显著更高（分别为70.3%、62.9%和33.3%）。总体而言，19株分离株（30.6%）同时产生MBL和AmpC，其中大多数为生物膜阳性（63.1%）。最后，4株分离株（6.4%）产生所有三种酶，其中3株（75%）形成生物膜。
生物膜形成（强和弱）与pslA基因携带密切相关。生物膜形成也与MBL和AmpCβ-内酰胺酶的产生相关。更重要的是，多重β-内酰胺酶表型与强生物膜的形成有关。
