Browsing by Author "Paterson, Lauren Ann"
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- ItemThe epidemiology of Gram negative bacteraemia at Tygerberg Hospital(Stellenbosch : Stellenbosch University, 2018-03) Paterson, Lauren Ann; Whitelaw, Andrew; Newton-Foot, Mae; Stellenbosch University. Faculty of Faculty of Medicine and Health Sciences. Dept. of Pathology. Medical Microbiology.Background Escherichia coli and Klebsiella pneumoniae are common causes of Bloodstream Infections (BSI). β-lactam antibiotics, such as cephalosporins and carbapenems, are commonly used to treat these infections. Increasing resistance has been noted, usually due to plasmid mediated β-lactamases such as Extended-Spectrum β-lactamases (ESBLs) and carbapenemases. This study describes the antibiotic resistance profiles, outcomes and epidemiology of Gram negative BSIs in a tertiary hospital in Cape Town, South Africa. Methods Patients with E. coli (n=70) and K. pneumoniae (n=70) bacteraemia identified at Tygerberg Hospital between April 2015 and March 2016 were included. Identification and Antibiotic Susceptibility Testing (AST) were performed as part of routine testing. Patient data was obtained through record review. ESBL and carbapenemase genes were characterised by Polymerase Chain Reaction (PCR) and DNA sequencing. Isolates were typed using rep-PCR and Pulsed Field Gel Electrophoresis (PFGE). Chi-square and Mann-Whitney tests were used to estimate significance of correlation. Results and discussion 45% of patients were male, and 30.7% were paediatric. 66.4% of BSI were hospital-acquired. K. pneumoniae accounted for 61.3% of hospital-acquired isolates; 72.3% of community-acquired isolates were E. coli. 55.7% of K. pneumoniae and 15.7% of E. coli were cephalosporin resistant (presumed ESBL); one K. pneumoniae isolate was carbapenem resistant. Increased antibiotic resistance and ESBL production was seen in hospital-acquired isolates. ESBL genes were harboured in 35.7% of isolates; 50.7% contained β-lactamase genes and 13.6% no β-lactamase genes. Most TEM genes (98%) were β-lactamases; 47.4% of SHV genes were β-lactamases, 7% were ESBLs and 45.6% were SHV genes whose spectrum is uncertain. Isolates containing SHV genes with uncertain spectrum were phenotypically susceptible to cephalosporins, suggesting these enzymes do not have extended-spectrum activity. Multiple β-lactamase genes were present in 60% of K. pneumoniae isolates, and only 5.7% of E. coli isolates. CTX-M genes were the most common ESBL genes, with most (91.3%) of these belonging to group 1. CTX-M genes were found in combination more often than not (84.8%). No carbapenemase genes were detected. Molecular and phenotypic resistance agreed in 95.3% of isolates. The 30-day mortality rate was 30%, with no association between mortality and hospital-acquired infection, or with ESBL production (phenotypic or molecular). Molecular and phenotypic resistance was associated with hospital-acquired isolates (P=0.001, P<0.001). Both strain typing techniques showed substantial diversity among isolates, with minimal clustering; which suggests multiple clones in the hospital, precluding any possibility of assessing associations. Conclusion Increased resistance was observed in hospital-acquired isolates, and the association between hospital-acquired isolates and ESBL presence was significant, which is not unexpected. Isolates were genetically diverse and showed minimal clustering, suggesting that resistance may be due to horizontal transmission. Continuous efforts towards surveillance of the epidemiology and resistance patterns of circulating strains are required to monitor and guide antimicrobial stewardship, infection prevention and control (IPC) practises and empiric therapy.