Browsing by Author "Van Biljon, Bernardus Daniel"

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    Population structure and biofilm formation of Pseudomonas aeruginosa isolated from patients with severe burn wounds at Tygerberg Hospital
    (Stellenbosch : Stellenbosch University, 2017-12) Van Biljon, Bernardus Daniel; Newton-Foot, Mae; Whitelaw, Andrew; Faculty of Medicine and Health Sciences. Dept. of Pathology. Division Medical Microbiology.
    ENGLISH ABSTRACT : Pseudomonas aeruginosa is a common opportunistic pathogen which is responsible for more than 11% of nosocomial infections including urinary tract infections (UTI’s), bacteraemia, pneumonia and soft tissue infections. Little is known about P. aeruginosa associated infections in burn wound patients in South Africa, and in particular at Tygerberg hospital. Burn wound patients are highly vulnerable to infections due to natural defence destruction. P. aeruginosa has the ability to form a biofilm and cause persistent biofilm associated infections. The biofilm acts as a protective layer defending organisms against the environment, host immune system and antibiotic treatment. P. aeruginosa infections have a mortality rate of 40-50% in burn wound patients. This study aimed to determine the population structure of P. aeruginosa isolated from the burns unit and burns ICU in comparison to isolates from other wards at Tygerberg hospital, to investigate their ability to form biofilms and to determine the impact of various antibiotics on biofilm formation. P. aeruginosa isolates from blood cultures, swabs and tissue specimens from adult and paediatric patients at Tygerberg hospital were collected from February 2015 to March 2016. Forty isolates from the burns unit and 40 isolates from outside the burns unit were used for the study. Multiple locus variable number tandem repeat analysis (MLVA) was used for strain typing. Biofilm formation was assessed by crystal violet staining. The strength of biofilm formation of the isolates was determined after a 12h incubation period and the effects of varying concentrations of four different classes of antibiotic on biofilm formation was determined over a 24 hour period. Forty two different MLVA types were described, of which ten were assigned to two or more isolates. Thirty two MLVA patterns were unique to a single isolate. MLVA type 1 was the most abundant MLVA type; 60% of the isolates from the burns unit and burns ICU were type 1. The predominance of a single MLVA type within the burns unit implies nosocomial transmission within the burns unit. Greater diversity was observed outside the burns unit. P. aeruginosa appeared to form multiple biofilm formation patterns. Three distinct patterns of biofilm formation could be described after 10 hours incubation. These patterns did not correlate with MLVA type. The effect of exposure to four antibiotics (cefepime, ciprofloxacin, imipenem, and gentamicin) on biofilm formation over time was shown to differ between organisms with early and late onset biofilm formation patterns, but is not predicted by MLVA type. The mechanisms of action of the antibiotics also did not seem to predict the response since two antibiotics with the same mechanism of action (cefepime and imipenem) had different biofilm formation patterns. Increased knowledge of the P. aeruginosa population structure and biofilm forming ability in this patient group, and enhanced understanding of the effect of antibiotic treatment on biofilm formation may enable improvements in transmission prevention, the selection and use of antibiotics for treatment and, ultimately, improve patient outcome.