WOUND CONTAMINATION DURING PRIMARY THR DETECTED BY POLYMERASE CHAIN REACTION

Abstract

Introduction: Although there is evidence that laminar flow operating theatres (LFOTs) can reduce the incidence of wound infection over standard operating theatres (STOTs) when no routine peri-operative antibiotics were used, the evidence for the use with concurrent parenteral antibiotics is less compelling. A number of prior studies have compared the bacterial load observed in LFOTs and STOTs by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the polymerase chain reaction (PCR), a molecular biology test for the presence of bacterial DNA. The purpose of this study was to compare the wound contamination rate during THRs performed in STOT with that in LFOTs using PCR.

Method: Patients undergoing primary THR for osteoarthritis without a history of joint infection were recruited for the study. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

Results: In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture (80 specimens and 40 THRs in total).

Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs. Of these 12, three were taken at the start of surgery and nine at the end of the surgery, equivalent to a 45% wound contamination rate (9 of 20). Only two specimens (5%), both taken at the end of surgery, were positive on enriched culture.

In LFOTs, bacterial DNA was identified by PCR on eight of 40 specimens (20%). Of these eight, two were taken at the start of surgery and six at the end of surgery, equivalent to a 30% wound contamination rate (6 of 20). None of the specimens were positive on enriched culture.

Discussions: We concluded that wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data are important in that they confirm that continued vigilance to technique continue to be important as significant wound contamination can occur despite the use of ultra clean air operating theatres.