Molecular epidemiological study of extended spectrum betalactamase (ESBL) producing bacteria from teaching and district general hospitals within Hampshire

Student thesis: Doctoral Thesis


This study provided epidemiological and molecular information regarding multi-resistant ESBL-producing bacteria over two years, assessed the effects of antimicrobial agents onintestinal microbiota resistance and identified potential environmental sources of ESBLcontamination.

The most prevalent bacterial species to express ESBL resistance was Escherichia coli [85% in2010 and 84% in 2012]. Other species included members of Enterobacter, Klebsiella, Citrobacter and Proteus. An increase in resistance to nine antibiotics [amoxicillin 1%, coamoxiclav14%, meropenem1%, cefotaxime 9%, ertapenem 2%, ceftazidime 7%, tigecycline5%, cefuroxime 8% and gentamicin 6%] was observed, indicating that multi-resistant infections had increased over the sampling period.

Multiplex PCR revealed that the CTX-M determinant was most prevalent [38% in 2010 and27% in 2012], followed by TEM then SHV. Double resistance determinants were identified in 68% of the total isolates. A statistical relationship was determined between joint expression of TEM and SHV and patient age [p=0.0174], suggesting that resistance initially presents within the elderly population. ERIC-PCR analysis was used to identify clonal relationships between the isolates. Ten potential clonal groups were identified; however phylogenetic analysis revealed that antibiotic selection and conjugation was taking place simultaneously, with a turnover of isolates observed between the two year cohorts.

Results obtained from the simulated colon model suggested that the receipt of antibiotics may contribute to the overall resistance of the gut microbiota. Increases in co-amoxiclav, amoxicillin and trimethoprim resistance was observed after dosing, while gentamicin remained stable.

One hundred and thirteen non clinical samples [animal faeces and food products] were analysed to determine ESBL presence. ESBL producing isolates were recovered from 32% of the animal faecal and 60% of food product isolates, AmpC was also present in 15% of the faecal and 12% of the food product isolates. Sequence analysis of the SHV and CTX determinants revealed relationships between determinants associated with both animal and human infections.
Date of AwardMay 2016
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorVitaly Zinkevich (Supervisor), James Brown (Supervisor) & Julian Mitchell (Supervisor)

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