Potential Risk of Cross Infection From Slit–Lamps

Abstract

Abstract: : Purpose:Personnel hands and tonometer heads are known vectors of nosocomial infections in the ophthalmic environment. Implementation of specific infection control policies targeting these areas has reduced the rate of cross–infection. Slit–lamps remain a possible source for the transfer of micro–organisms. This study was designed to assess the extent of microbial colonisation of various slit–lamp components in the emergency room (ER) and outpatient clinic (OPC) during the course of a single clinic session at a major referral centre. Methods:A total of 17 slit–lamps (5 ER, 12 OPC) were evaluated. Swabs were taken from the head rest, chin rest, and transformer switch using sterile, cotton–tipped buds moistened with sterile saline, pre– and post–cleaning with a solution of detergent (chlorhexidine) and water prior to the start of clinic. Swabs were placed immediately in transport medium and later plated onto blood agar. Blood agar plates were incubated at 37^oC for 2 weeks. All swabs were repeated at the end of the clinic. Results:Cleaning before the start of clinic reduced the overall number of microbial isolates (pre=14/51(27.5%), post= 9/51(17.6%), p=0.27). By the end of the clinic session, there was a significant rise in culture–positive swabs (22/51(43.1%), p=0.01), although there was no difference in the frequency of isolates grown between the two clinic areas (ER=7/15(46.6%), OPC=15/36(41.7%), p=0.17). Microbial contamination of the head and chin rests exceeded that of the transformer switches pre– and post–cleaning, but the growth was restricted to scanty skin flora including Staphylococcus Epidermidis. At the end of the clinic, microbial colonisation had increased (head rests 9/17(52.9%), chin rests 12/17(70.5%), transformer switches 3/17(17.6%)) with penicillin–resistant Staphylococcus Aureus being isolated from 3 swabs taken from 2 slit–lamps situated in the OPC (2 head rests, 1 chin rest). Fungal species were not isolated after prolonged incubation of the blood agar plates. Conclusions:Slit–lamp cleaning prior to the start of clinic decreases the microbial load, but colonisation increases during the course of a clinic session most notably on the head rest and chin rest components. The presence of antibiotic resistant organisms suggests potential for nosocomial transfer. We recommend that slit–lamps should be cleaned in between patients as well as the beginning and end of clinic. Cleaning should include the transformer switch.

Keywords: clinical (human) or epidemiologic studies: risk factor assessment • clinical (human) or epidemiologic studies: systems/equipment/techniques