Correlation between increased consumption of fluoroquinolones in outpatients and resistance of Escherichia coli from urinary tract infections

Milan Cizmana,*, Andreja Orazemb, Veronika Krizan-Hergouthc and Jana Kolmanc

a Department of Infectious Diseases, Japljeva 2, 1525 Ljubljana; b Institute of Public Health of Slovenia, Trubarjeva 2, 1000 Ljubljana; c Institute of Microbiology and Immunology, Medical Faculty Ljubljana, Zaloska 4, 1000 Ljubljana, Slovenia

Sir,

Increased use of fluoroquinolones may lead to increased fluoroquinolone resistance in Escherichia coli in the community.1 The correlation between fluoroquinolone consumption and resistance in urinary isolates of E. coli in Slovenia has been recently evaluated.

In Slovenia, the outpatient consumption of fluoroquinolones increased from 0.59 defined daily doses (DDD)/1000 inhabitants/year in 1992 to 1.50 DDD/1000 inhabitants/ year in 1999, or from 0.27 to 7.64% of all outpatient antibiotic prescriptions. In children <15 years of age, the number of fluoroquinolone prescriptions increased from 0.7 to 1.5 prescriptions/1000 inhabitants/year, and from 22.5 to 64.6 in adults. In 1999, ciprofloxacin represented 51.7% of all fluoroquinolone prescriptions, followed by norfloxacin (45.7%), pefloxacin (2.4%) and ofloxacin (0.1%). The consumption of fluoroquinolones in Slovenia in 1999 was higher than in Sweden (1.03 DDD) and Denmark (0.23 DDD) in 1998, but lower than in Spain in 1997 (2.22 DDD).2

Two analyses of resistance of E. coli to fluoroquinolones were performed in 1999. In the first, the susceptibility to ciprofloxacin of E. coli isolates from children and adults treated for community-acquired urinary tract infections as inand outpatients at the Department of Infectious Diseases in Ljubljana was assessed. Susceptibility testing was performed by an agar diffusion method according to the NCCLS.3 Repeat isolates from the same patients were excluded. The resistance of E. coli to ciprofloxacin was significantly (P = 0.02, {chi}2 test) higher in patients >15 years of age (16/174, 9.2%) than in children (1/93, 1.1%). In 1993, all E. coli isolated in children (n = 55) were susceptible to ciprofloxacin. In contrast, the resistance of E. coli to ciprofloxacin in adult patients increased from 3.6% (6/168) in 1996 to 9.2% in 1999.

By comparison, the consumption of trimethoprim/sulphamethoxazole (TMP/SMX) in children decreased by 37% between 1992 and 1999. The resistance of urinary E. coli isolates in children has not changed significantly (25% in 1993 to 21.6% in 1999). In adults, the consumption of TMP/SMX decreased by 9% from 1996 to 1999. The resistance of E. coli did not change significantly (12.1% in 1996 to 14.4% in 1999).

Microbiology laboratories covering c. 70% of the Slovenian population participated in the second analysis.4 In 1999, 10.4% (795/7672) of all urinary E. coli isolates were resistant to ciprofloxacin. Resistance rates were 13.4% (703/ 5243) in adults and 1.8% (43/2429) in children (P < 0.01, {chi}2 test). The highest resistance rate was observed in adult outpatients (20.4%, 465/2280), followed by adult inpatients (8.0%, 237/2963), paediatric outpatients (2.0%, 31/1529) and paediatric inpatients (1.3%, 12/900). In one laboratory, the resistance of E. coli in adult outpatients and nursing home residents was compared. A significantly higher resistance rate of urinary E. coli isolates was observed in nursing home residents (74.6%, 85/114) than in adult outpatients (30%, 112/373) (P < 0.01, {chi}2 test).

Our data indicate that increasing resistance of E. coli to fluoroquinolones is associated with an increase in consumption of these antibiotics in the community. The highest resistance rates were found in nursing home residents where risk factors such as frequent use of quinolones, complicated infections and use of urinary catheters are commonly present.5 To prevent a further increase of resistance to quinolones, The Institute of Health Insurance of Slovenia, which covers all healthcare costs, issued a recommendation that fluoroquinolones should be used if urinary tract isolates are susceptible only to these antibiotics or as a second-choice drug for patients in whom treatment with the antibiotic of first choice has failed.

Notes

J Antimicrob Chemother 2001; 47: 502

* Corresponding author. Tel: +386-1-2310-558; Fax: +386-1-2302-781; E-mail: milan.cizman{at}mf.uni-lj.si Back

References

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2 . Ruiz-Bremon, A., Ruiz-Tovar, M., Perez-Gorricho, B., Diaz de Torres, P. & Lopez-Rodriguez, R. (2000). Non-hospital consumption of antibiotics in Spain: 1987–1997. Journal of Antimicrobial Chemotherapy 45, 395–400.[Abstract/Free Full Text]

3 . National Committee for Clinical Laboratory Standards. (1999). Performance Standards for Antimicrobial Susceptibility Testing: Ninth Informational Supplement M100-59. NCCLS, Villanova, PA.

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