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Phylogenetic groups, antibiotic susceptibility, biofilm formation and PFGE in Escherichia coli from community-acquired cystitis

Abstract number: 1733_86

Ejrnaes K., Reisner A., Lundgren B., Ferry S., Holm S., Monsen T., Lundholm R., Frimodt-Moller N.

Objectives: To study Escherichia coli (EC) isolates from community-acquired cystitis with respect to phylogenetic groups, antibiotic susceptibility, biofilm formation and PFGE.

Methods: A subgroup of 243 out of 1162 women with community-acquired cystitis from a placebo-controlled comparative study of three different dosing regimes of mecillinam was studied. We stratified patients into two groups: 1) The mecillinam group (MG), all treated with mecillinam and all with EC at inclusion: a group of all those having EC at follow-up, plus a randomly selected group having negative culture at follow-up (N = 160); and 2) the placebo group (PG), all treated with placebo and all with EC at inclusion: a randomly selected group having EC at follow-up and a randomly selected group having negative culture at follow-up (N = 83). The primary infecting ECs were studied. Susceptibility to mecillinam was tested by agar dilution; MICs of ampicillin, cefpodoxime, chloramphenicol, ciprofloxacin, gentamicin, streptomycin, sulfamethoxazole, trimethoprim and tetracycline were tested with Sensititre. Phylogenetic grouping was determined by a triplex PCR assay. Biofilm formation was measured in 3 media (static growth, 48 hours, crystal violet staining). PFGE was done with XbaI to the primary infecting EC and EC from follow-up.

Results: Only 20% of the strains were resistant to one or more antimicrobials. Susceptibility was significantly associated with phylogenetic group B2 for ampicillin (P = 0.048), chloramphenicol (P = 0.002), streptomycin (P = 0.001), sulfamethizole (P = 0.006), trimethoprim (P = 0.013) and tetracycline (P = 0.003). Resistance to 3 or more antimicrobials was significantly associated with phylogenetic group A (P = 0.033) and D (P = 0.014). Resistance to less than 3 antimicrobials was significantly associated with B2 (P < 0.0001). EC causing relapse/persistence had a higher biofilm formation than those causing reinfection/cure in 2 of 3 media (P = 0.002 and P = 0.011) in the PG, but there was no significant difference in the MG.

Conclusion: Although representing a low-antibiotic-consumption area (Sweden) with low resistance rates, still, antimicrobial susceptibility was significantly associated with phylogenetic group B2 and resistance to 3 or more antimicrobials with A and D. EC causing relapse/persistence had a higher biofilm formation capacity than those causing reinfection/cure in the PG.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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