Journal Article

Bacteria with increased mutation frequency and antibiotic resistance are enriched in the commensal flora of patients with high antibiotic usage

Ingegerd Gustafsson, Maria Sjölund, Erik Torell, Marie Johannesson, Lars Engstrand, Otto Cars and Dan I. Andersson

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 52, issue 4, pages 645-650
Published in print October 2003 | ISSN: 0305-7453
Published online October 2003 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dkg427
Bacteria with increased mutation frequency and antibiotic resistance are enriched in the commensal flora of patients with high antibiotic usage

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Background: We examined how prolonged antibiotic treatment affected the resistance and mutation frequency of human microflora isolated from intestine (Escherichia coli, enterococci spp.), pharynx (α-streptococci) and nostril (coagulase-negative staphylococci, CoNS).

Methods: Samples were collected from patients at the Center of Cystic Fibrosis (n = 18) and the haematology ward (n = 18) of the University Hospital, Uppsala, Sweden. The individually used amount of antibiotics for 1 year was recorded as the defined daily dose (DDD). Primary health care patients (n = 30), with no antibiotic treatment for 1 year before sampling, were used as controls. Three isolates of each bacterium from each patient were examined. Antibiotic susceptibilities were determined by disc diffusion. Mutation frequencies to rifampicin resistance were measured on 30 independent cultures of each bacterial species from each individual by plating on rifampicin agar plates. For α-streptococci the mutation frequency to streptomycin resistance was also determined.

Results: Isolates from patients with high antibiotic use showed a pronounced shift towards increased resistance and a small but significant increase in the mutation frequency compared with isolates from the controls. For E. coli, enterococci and CoNS the increase in geometric mean mutation frequency in the patient group was 3-, 1.8- and 1.5-fold, respectively (P values 0.0001, 0.016 and 0.012). For α-streptococci there was a significant difference in geometric mean mutation frequency between patient and control groups for streptomycin resistance (P = 0.024) but not for rifampicin resistance (P = 0.74).

Conclusions: High antibiotic use selected for commensals with highly increased resistance and a slight increase in mutation frequency.

Keywords: Keywords: human microflora, antibiotic treatment, selection, mutators

Journal Article.  3869 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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