Bacteriological profile and their antimicrobial susceptibility pattern in central venous catheter tip culture

Correspondence: Dr Jyotshna Sapkota, MBBS, M.D Lecturer, Department of Microbiology, Kathmandu Medical College Teaching Hospital, Sinamangal Kathmandu, Nepal. Email: 21jyots@gmail.com Background: Bacterial colonization of central venous catheter carries risk of developing catheter-related blood stream infections. The purpose of this study is to find out the frequency of colonization of by different bacterial pathogens and their antibiotic sensitivity pattern..

selection of appropriate antimicrobial agents for prophylaxis and empirical therapy of CRBSI.

MATERIALS AND METHODS
This study was done in Kathmandu Medical College Teaching Hospital, Kathmandu, Nepal over the period of one year from January 2016 to December 2016.All the central venous catheter tip sent for culture and antibiotic sensitivity in microbiology laboratory of Kathmandu Medical College were included in this study.A total of 53 CVC tips were received in microbiology laboratory over the study period.
Extra luminal Maki's roll plate method was used for processing of catheter tip.Using sterile forceps, the catheter tip was removed from transport tube and laid on Blood agar plate.The tip was rolled back and forth across the entire surface of blood ager plate using sterile forceps and exerting slight downward pressure and incubated aerobically at 37 0 C. 4,5 Agar plates were examined at 24 hours, 48 hours and 72 hours.Significant growth was defined as >=15 colony forming unit.Significant colonies were further processed.Organisms were identified according to colony morphology, gram staining and biochemical tests.Antibiotic sensitivity test were done by Kirby Bauer disk diffusion technique as recommended by Clinical Laboratory Standards Institute (CLSI).Statistical analysis was performed using Microsoft Excel.

RESULTS
A total number of 53 samples were sent to our microbiology laboratory for culture and sensitivity during study period.Out of 53 samples, 21 (39.6%)showed significant growth of organism.Remaining samples either had no organism grown or had insignificant growth.
Out of 53 samples submitted for culture and antibiotic susceptibility, 21 (39.6%)showed the significant growth.In our study 52.3% of pathogens isolated were gram negative bacilli, 33.3% were gram positive cocci.9.6 % were multiple growth and 4.8% were Candida albicans.Acenitobacter baumannii was the most common organism isolated followed by Staph.aureus and Klebsiella pneumoniae.Distribution of isolated bacteria is shown in Table 1.Among these 18 isolates were tested for antibiotic susceptibility pattern.The details of the antimicrobial susceptibility pattern of overall microorganisms are shown in table 2.

DISCUSSION
Central venous catheter is frequently used in ICU settings, however their colonization with different types of organism increases the hospital stay and mortality in these patients.Colonization of CVC with microorganism is one of the main risk factor for occurrence of CRBSI.][8][9][10] our study showed the colonization rate to be 39.6%.6][7][8][9] however our study showed the predominant organism to be gram negative bacilli, which is consistent with some of the studies done recently. 10,11Moreover recent studies have also shown the leading cause of CRBSI to be gram negative bacilli. 12cenitobacter baumannii was the most common organism isolated (29%) which is in contrast with the similar studies done in the past, [6][7][8][9][10][11] where some of the studies showed Staph.aureus, CONS and Pseudomonas aeruginosa as the commonest organism colonizing CVC.This may be due to emergence of Acentiobacter species as common colonizer in hospitalized patients in recent years. 13According to various literature common organism colonizing CVC and associated with infections are CONS, Staph aureus, Candida spp and gram negative bacilli. 14Our study also confirmed these findings.
In this study overall isolates were mostly sensitive to chloramphenicol.However, routinely used antibiotics, like Gentamicin, Amikacin and Ceftriaxone are mostly resistant.
Our study also showed decrease in sensitivity to Imepenem and Piperacillin-Tazobactum, which are commonly used in ICU settings.This shows the changing pattern in antibiotic sensitivity.
Our study showed 100% efficacy Vancomycin and Lenezolid, which are used, only in gram positive organism and Colistin.

CONCLUSION
In conclusion, we report a significant shift in colonizers of central venous catheter towards predominance of Gram negative bacilli, so empirical treatment must to prevent CRBSI must address their increasing prevalence.We suggest that empirical antibiotic selection should be based on knowledge of the local prevalence of bacteria and antibiotic sensitivity pattern rather than on universal or even national guidelines.