Extended-spectrum β-lactamase/AmpC-producing uropathogenic Escherichia coli from HIV patients: Do they have a low virulence score?

Journal of Medical Microbiology. 2013: 63; 345-351.

Kesavaram Padmavathy,1,2 Krishnan Padma1 and Sikhamani Rajasekaran3

1Dept of Microbiology, Dr ALM PGIBMS, University of Madras, Chennai, India.

2Dept of Microbiology, Sree Balaji Dental College and Hospital, Bharath University, Chennai, India.

3Government Hospital of Thoracic Medicine, Chennai, India.


Extended-spectrum β-lactamase (ESBL) production and quinolone resistance are often associated in enterobacteria. Prior exposure to 3G cephalosporins/quinolones accelerates the risk of resistance to both these groups of antibiotics. Hence, information on the antimicrobial resistance pattern of uropathogenic Escherichia coli (UPEC) isolates is important to better formulate the guidelines for the empirical therapy of urinary tract infection in the context of HIV/AIDS. The aim of this study was to determine the incidence of ESBL/AmpC and fluoroquinolone (FQ) resistance among urinary E. coli isolates and to establish the association of extraintestinal virulence and phylogenetic distribution with antibiotic resistance and host immunocompromisation. Accordingly, 118 urinary Escherichia coli isolates from HIV (n = 76) and non-HIV antenatal patients (n = 42) from Chennai, South India, were analysed for the presence of five virulence-associated genes (VAGs): pap, sfa/foc, afa/dra, iutA and kpsMII. Compared with the susceptible HIV isolates, the majority of the ESBL(+)AmpC(+)FQ(R) isolates harboured iutA (66.7%) and pap (40%). The FQ-resistant HIV isolates were significantly enriched for iutA (67.8%) and kpsMII (47.5%) and qualified as UPEC (54.2%), while a majority of the FQ-susceptible isolates from the non-HIV patients were found to harbour pap (48.4%), sfa/foc (41.9%) and kpsMII (48.4%) and were classified as UPEC (40.5%). We conclude that antibiotic-resistant (ESBL(+)AmpC(+)and/or FQ(R)) phylogroup D isolates with limited virulence are competent enough to establish infections in HIV patients, while among non-HIV patients, an array of virulence factors is essential for E. coli to overcome host defences irrespective of antibiotic resistance.

PMID: 23161767



Uropathogenic Escherichia coli (UPEC) are documented to be the major cause of urinary tract infection (UTI) accounting for substantial morbidity among HIV patients. The antimicrobial susceptibility profile of the UPEC has been changing over the years. Resistance to third generation cephalosporins in E. coli is a formidable problem associated with escalating health care costs and increased reliance on newer antibiotics. There have been only a few studies on the incidence of UTI caused by ESBL/AmpC-producing E. coli among HIV patients in India.

HIV patients receive frequent courses of fluoroquinolones and cepahalosorins for the treatment of LRI & AGE. Prior exposure to these antibiotic classes is reported to serve as the driving force for the selection of endogenous multidrug resistant pathogens. We planned to assess the possible risk of previous antibiotic exposure especially cephalosporins/ fluoroquinolones for the development of ESBL/ AmpC resistance among E. coli isolates from HIV patients. We found that the incidence of fluoroquinolone resistance and ESBL/ AmpC producers were more common among the HIV isolates compared to the non-HIV isolates.

UPEC are a distinct pathotype of Escherichia coli that often belong to the phylogroup B2 and are multivirulent. The major virulence factors elaborated by the UPEC include the adhesins (pyelonephritis associated protein, afimbrial adhesin and S fimbriae), iron uptake systems (aerobactin) and protectins (group II capsule). The minimal virulence requisite of any bacterial strain to initiate an infection largely depends on the patient’s immune status. We hypothesized that the E. coli isolates from HIV (immunocompromised) patients would have a reduced virulence profile compared to those from non-HIV (immunocompetent) patients. We assessed the incidence of five virulence-associated genes (VAGs): pap, sfa/foc, afa/dra, iutA and kpsMII that encode the prime virulence factors that determine the UPEC status. We found that the mean virulence scores of UPEC isolated from the non- HIV patients were significantly higher than the isolates from HIV patients.

FQ resistant/ESBL/AmpC producing isolates are reported to be associated with a significant shift towards the non-B2 phylogenetic lineage as well as a reduced virulence profile. We found that the majority of the FQ resistant/ESBL/AmpC producing isolates from HIV patients belonged to phylogroup D. Also, multidrug resistance was exhibited by the non-B2 phylogenetic groups with decreased or no virulence determinants. We postulate that multidrug resistance provides a fitness advantage for these less virulent strains to infect compromised hosts.

This study was supported by a research grant from the Indian Council of Medical Research (ICMR).



Dr. Kesavaram Padmavathy, Ph. D.,

AssistantProfessor, Dept of Microbiology,

Sree Balaji Dental College and Hospital,

Bharath University, Chennai, India.

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