Coliforms in the Oral Cavity - Retrospective Analysis of Laboratory Data

Objectives: 'Coliforms' or enterobacteriaceae are a group of facultative Gram-negative bacilli including Escherichia coli and Klebsiella species. Recent concerns have been raised over increasing levels of antimicrobial resistance in this group of microbes, although their role in oral colonisation and infection is unclear. The aim of this study was to investigate epidemiological features of specimens containing coliforms submitted to a regional Oral Microbiology Laboratory over a 2 year period (2006-2007). Methods: A review of laboratory data was performed on specimens where coliforms were isolated. Data collated included patient demographics, referral source, clinical details, specimen type, species identification and antibiotic sensitivities. Results: Coliforms were isolated from 152 out of 2813 specimens submitted to the laboratory during the study period. The most commonly identified isolates were Enterobacter cloacae (14%), K. pneumoniae (13%), E. coli (12%) and K. oxytoca (11%). The most common reason for specimen submission was a suspected diagnosis of Candidal infection and 105 isolates were co-cultured with Candida species. The specimen type from which coliforms were most frequently isolated was from an oral rinse (36%) or a tongue swab (20%). The majority (68%) of patients were in the 60-89 year age group and were most frequently treated in the oral medicine/oral surgery departments (32%), followed by community health centres (30%), hospices (9%) and general dental practice (7%). A high proportion (68%) of isolates were resistant to commonly used first line antimicrobial agents. Conclusions: Coliforms are relatively uncommon isolates from oral disease and their role is unclear. Their presence in the oral cavity may shed light on the transmission of these organisms within community settings and may be indicative of more wide spread environmental contamination by these microbes.