Study of metallo beta lactamase production and biofilm formation of pseudomonas aeruginosa in clinical isolates

Background: Pseudomonas aeruginosa is one of the most common pathogens causing nosocomial infections. Metallo-β lactamases (MBL) have recently emerged as one of the most troublesome resistance mechanisms owing to their capacity to hydrolyze all β-lactams including carbapenems.. Objectives: To know the antibiotic susceptibility pattern in Pseudomonas aeruginosa isolates. Also, to detect MBL production and biofilm forming ability of Pseudomonas aeruginosa from various clinical isolates from our hospital. Materials and methods: The present study was conducted in the department of Microbiology, Yenepoya medical college, Mangalore, Karnataka for a period of three months (December 2017 to February 2018). Pseudomonas aeruginosa was identified from the clinical samples by standard microbiological techniques. The isolates were further subjected for antibiotic susceptibility testing by Kirby-Bauer disc diffusion method on Mueller Hinton agar. Phenotypic detection of Metallobetalactamse (MBL) was carried out by Combined Disk Diffusion Technique (IPM CDST) using imipenem (10μg) and imipenem (10μg) +EDTA (750μg) discs. Biofilm formation was detected using Tissue Culture Plate method. Results: In our study, total of 155 isolates of P.aeruginosa were collected. Most of the isolates were collected from pus samples(52.2%), followed by sputum & ET tip (20%). Maximum resistance was observed for ceftazidime (38.7%) and ciprofloxacin(34.8%) whereas polymyxin B(7.7%) and piperacillin-tazobactum(20.6%) showed lowest resistance. 19(12.2%) isolates exhibited ≥ 7 mm zone size enhancement indicating a positive MBL test.MBL production was seen highest among isolates from pus ( 42.1%),followed by urine(31.5%). MBL isolates were most sensitive to Polymyxin B (57.8%), followed by piperacillin –tazobactum 8(42.1%). 114(73.5%) isolates were strongly biofilm positive, 20(12.9%) were moderate and 21 (13.5%) were weak isolates. Out of 19 MBL producers, 14(73.6%) were strong biofilm forming isolates and 5 (26.3%) were moderate biofilm forming isolates. Conclusion: Though the prevalence of MBL in our study is lower when compared to other recent studies, an association between biofilm production and MBL production was observed. Routine detection of MBLs will ensure optimal patient care and timely introduction of appropriate infection control practices. The detection of biofilm production among P. aeruginosa may help in introducing newer techniques based on interference with biofilm formation.