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 â€‹= â€‹8) or colonized CVC (n â€‹= â€‹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 â€‹= â€‹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 â€‹= â€‹0.030). S. haemolyticus showed higher resistance to cloxacillin compared to other CoNS (p â€‹= â€‹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.

Distribution of mecA and qacA/B genes among coagulase negative staphylococci isolated from central venous catheters of intensive care unit patients.

PURPOSE: This study was designed to detect the prevalence of antibiotic and antiseptic resistance genes, mecA and qacA/B in coagulase negative Staphylococcus (CoNS) species isolated from intensive care unit patients with catheter related blood stream infections (CRBSI) or colonized central venous catheters (CVC). METHODS: Consecutive CoNS isolates from ICU patients with CRBSI or colonized central venous catheters were speciated and antibiotic susceptibilities were determined. The mecA and qacA/B genes were detected by polymerase chain reaction. RESULTS: Eighty-two CoNS isolates from ICU patients with CRBSI (n â€‹= â€‹8) or colonized CVC (n â€‹= â€‹74) were included. The mecA gene was detected in 62 CoNS isolates (76%). The commonest species isolated was S. haemolyticus (n â€‹= â€‹34; 41%) and 30 of these possessed mecA which was significantly higher compared to other CoNS species (p â€‹= â€‹0.036). The qacA/B gene was detected in 13 (16%) isolates. Eleven (13%) CoNS had both genes. A significant association was seen with the presence of mecA and resistance to cloxacillin (p â€‹< â€‹0.001) and erythromycin (p â€‹= â€‹0.046). Presence of qacA/B (p â€‹= â€‹0.007) or both mecA and qacA/B (p â€‹= â€‹0.014) was associated with a higher resistance to clindamycin. CONCLUSION: A considerably high prevalence of mecA and qacA/B genes as well as co-existence of both genes is noted among the CoNS isolated from ICU patients. This indicates the need of taking prompt actions in hospital acquired infection prevention including continuous surveillance.