Isolation and characterisation of extended spectrum B-lactamases in South African Klebsiella pneumonia isolates.
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Date
2012
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Abstract
The use of antibiotics and antimicrobial drugs has played a large role in the elimination of many
infectious diseases, however the wide spread use of such drugs has given rise to the phenomenon
of antimicrobial resistance and has rendered antibiotics ineffective to a broad range of bacteria.
The aim of the study was to ascertain the differences if any in the phenotypic and genotypic
resistance profiles of K. pneumoniae isolated from a single tertiary hospital in two surveillance
studies undertaken at different times, viz., 2001 and 2007 with special emphasis on ESBLs. A
correlation with antibiotic use was also undertaken.
ESBL positives were identified and phenotypic resistance profiles were generated based on the
resistance profiles of individual isolates by means of their MIC data. The molecular detection of
ESBLs was carried out using representative isolates and sequencing was based on the phenotypic
expression of the most common ESBL genes. The data was summarized using median values and
interquartile ranges. Antibiotic use and susceptibility in 2000 was compared to that in 2007 using
a Wilcoxon signed rank test for paired data since the same drugs were tested in both years.
Of the isolates that were tested, sequencing revealed that TEM – 1 was identified in all isolates
and SHV-1 and SHV-2 were identified in 60 % in the isolates collected in 2000 and 77 % and 11
% respectively in the isolates collected in 2007. SHV – 11 was present in 67% of isolates from
2007 and 55% of those were in combination with SHV – 1. Sequencing also revealed CTXM-15
present in one of the isolates collected in 2007. There was 100% susceptibility to cefoxitin and
only one isolate in 2007 showing an intermediate result to imipenem.
No novel β-lactamases were identified in this study; however the decrease in susceptibility over
time is proof of bacterial evolution. The variety of β-lactamases and diversity of plasmid profiles
in these two small populations provides proof to the claim that dissemination of resistance in
Klebsiella pneumonia is effortless. Statistical analysis showed an increase in resistance from the
year 2000 to 2007 however the correlation between overall antibiotic use and the increase in
resistance did not reach statistical significance. It was observed that resistance increased despite only a slight increase in the use of a few antibiotics to which we attributed co-carriage of resistance genes.
Description
Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Westville, 2012.
Keywords
Beta lactamases., Drug resistance in microorganisms., Enzyme inhibitors., Microbial enzymes., Theses--Medical biochemistry.