Characterisation of propionibacterium acnes

Propionibacterium acnes forms part of the normal flora of the skin, oral cavity, large intestine and the external ear. Historically, P. acnes is considered to be of low virulence; however, in recent years it has been found as the aetiological agent in various pathologies including acne vulgaris, endophthalmitis, endocarditis, osteomyelitis, sarcoidosis, prosthetic hip infections and sciatica. It currently remains unclear why this normally harmless commensal can cause infection and contribute to a number of clinically significant conditions. This thesis has sought to investigate the phenotypic, genetic and antigenic properties of P.acnes strains isolated from sciatica patients undergoing microdiscectomy, normal skin, blood cultures, prosthetic hips and acne lesions. Isolates' phenotype was examined by determining their biotype by analytical profile index, antimicrobial susceptibility, virulence factor expression and serotype. A molecular typing method for P.acnes was developed using random amplification of polymorphic DNA (RAPD). Patient serum was used to screen P.acnes strains for antigens expressed in vivo and the chemical composition determined. The serodiagnostic potential and inflammatory properties of identified antigens were assessed. The optimised and reproducible RAPD protocol classified strains into three major clusters and was found to distinguish between the serotypes I and II for a large number of clinical isolates. Molecular typing by RAPD also enabled the identification of a genotype that did not react with the type I or II monoclonal antibodies and these strains may therefore constitute a previously undiscovered subspecies of P.acnes with a genetic background different from the type I and II serotypes. A major cell associated antigen produced by all strains was identified and characterised. A serological assay based on the antigen was used to measure IgG and IgM levels in serum from patients with acne, sciatica and controls. No difference in levels of antibodies was detected. Inflammatory properties of the antigen were measured by exposing murine macrophage-like cells and measuring the release of nitric oxide and tumour necrosis factor-alpha (TNF-α). Only TNF-α was elicited in response to the antigen. The phenotypic, genotypic and antigenic properties of this organism may provide a basis for future studies on P.acnes virulence and provide an insight into its mechanisms of pathogenesis.

Evaluation of disinfecting procedures for aseptic transfer in hospital pharmacy departments

Current practice in National Health Service (NHS) hospitals employs 70% Industrial Methylated Spirit spray for surface disinfection of components required in Grade A pharmaceutical environments. This study seeks to investigate other agents and procedures that may provide more effective sanitisation. Several methods are available to test the efficacy of disinfectants against vegetative organisms. However, no methods currently available test the efficacy of disinfectants against spores on the hard surfaces encountered in the pharmacy aseptic processing environment. Therefore, a method has been developed to test the efficacy of disinfectants against spores, modified from British Standard 13697 and Association of Analytical Chemists standards. The testing procedure was used to evaluate alternative biocides and disinfection methods for transferring components into hospital pharmacy cleanrooms, and to determine which combinations of biocide and application method have the greatest efficacy against spores of Bacillus subtilis subspecies subtilis 168, Bacillus subtilis American Type Culture Collection (ATCC) 6633, and Bacillus pumilis ATCC 27142. Stainless steel carrier test plates were used to represent the hard surfaces in hospital pharmacy cleanrooms. Plates were inoculated with 10(7)-10(8) colony-forming units per milliliter (CFU/mL) and treated with the various biocide formulations, using different disinfection methods. Sporicidal activity was calculated as log reduction in CFU. Of the biocides tested, 6% hydrogen peroxide and a quaternary ammonium compound/chlorine dioxide combination were most effective compared to a Quat/biguanide, amphoteric surfactant, 70% v/v ethanol in deionised water and isopropyl alcohol in water for injection. Of the different application methods tested, spraying followed by wiping was the most effective, followed closely by wiping alone. Spraying alone was least effective.

Investigating the prevalence of Salmonella in dogs within the Midlands region of the United Kingdom

Background - The intimate relationship between dogs and their owners has the potential to increase the risk of human exposure to bacterial pathogens. Over the past 40 years, there have been several reports on transmission of salmonellae from dogs to humans. This study therefore aimed to determine the prevalence of Salmonella in the faeces of dogs from the Midlands region of the United Kingdom to assess exposure risk and potential for zoonotic transmission. Results - A total of 436 apparently healthy dogs without diarrhoea from households (n = 126), rescue centres (n = 96), boarding kennels (n = 43), retired greyhound kennels (n = 39) and a pet nutrition facility (n = 132) were investigated for Salmonella shedding. Faecal samples were processed by an enrichment culture based method. The faeces from one dog (0.23 %; 95 % confidence limit 0.006 %, 1.27 %) was positive for Salmonella. The species was S. enterica subspecies arizonae. Conclusion - This study showed that the prevalence of Salmonella from faeces from apparently healthy dogs from a variety of housing conditions is low; however, Salmonella shedding was still identified.