Biofilm formation and antibiotic resistance among Coagulase Negative Staphylococcus species isolated from central venous catheters of intensive care unit patients.

PURPOSE: This study was conducted to determine the biofilm formation of coagulase negative Staphylococcus species (CoNS) isolated from patients with catheter related blood stream infection (CRBSI) and colonized central venous catheters (CVC) and their antibiotic susceptibility patterns and in situ biofilm formation of CVC tips.

METHODS: Eighty-two CoNS isolated from intensive care unit (ICU) patients with CRBSI (n ​= ​8) or colonized CVC (n ​= ​74) were included. Species identification and antibiotic susceptibility test were done. All isolates were screened for biofilm formation using crystal violet and 3-(4,5-dimethylthiazole-2-yl)-2-5-diphenyl-2H-tetrazolium bromide (MTT) assays and categorized as strong or moderate biofilm formers. CVC tips were subjected to crystal violet stain and scanning electron microscopy (SEM) to detect in-situ biofilm formation.

RESULTS: Staphylococcus haemolyticus (n ​= ​34; 41%) was the commonest to cause both CRBSI and CVC colonization. All 82 CoNS produced biofilms. Among them 77 (93.90%) were strong biofilm formers including all from CRBSI patients and 05 (6.10%) were moderate biofilm formers as detected by both methods. SEM showed bacteria adhered to surfaces of CVC tips with microbial-aggregates embedded in extracellular matrix. Mean crystal violet absorbance of CVC from CRBSI patients (0.6628) was significantly higher than colonized CVC (mean value 0.5592) (p ​= ​0.030). S. haemolyticus showed higher resistance to cloxacillin compared to other CoNS (p ​= ​0.039).

CONCLUSION: Majority of CoNS isolated were strong biofilm formers. In-situ biofilm formation on CVC tips were significantly evident in CRBSI patients compared to CVC colonized patients. S. haemolyticus is the commonest to cause both CRBSI and CVC colonization and shows significantly higher cloxacillin resistance rate.