In vitro Comparative Efficacy of Nitrofurantoin and Fluoroquinolones in Urinary Escherichia coli 

Background: Over the past decade, the prevalence of drug resistance in E. coli has increased dramatically. A more serious concern has been the gradual increase in floroquinolone resistance among UTI isolates. An older, narrow-spectrum drug nitrofurantoin—has led to little resistance among E.coli, can be an effective empirical therapy against urinary pathogens which require further study. Keeping in view the above fact, this study was carried out to determine the frequency of drug resistance in urinary E. coli especially in regard to nitrofurantoin.
Material and Methods;This descriptive study was conducted on a total  of  185 urinary  E. coli. isolates obtained from patients presenting with symptoms of UTI in Railway hospital during 2007–2008. The urine samples were inoculated on blood Agar and MacConkey’s Agar and incubated aerobically. Plates showing significant growth were identified by standard biochemical tests . Antimicrobial sensitivity testing was done by Kirby-Bauer disc diffusion method.
Results: Urinary E. coli showed a highest sensitivity towards amikacin (91.3%), and  nitrofurantoin (84.8%), while 23.2-52.4% of them were resistant to fluoroquinolones, , the most commonly used empirical antibiotics in the clinical settings. Comparative sensitivity of nitrofurantoin with other members of quinolones and aminoglycosides showed that majority of the isolates found resistant towards other members of the above mentioned group of antibiotics were found sensitive to nitrofurantoin.Conclusion: A significantly high proportion of the urinary E. coli isolates have developed resistance to the currently and most commonly prescribed empirical antibiotics like fluoroquinolones. The best in vitro susceptibility profile in this study has been shown by nitrofurantoin, an oral antibiotic, and keeping in view of this in vitro susceptibility pattern, a transition in empirical therapy needs further study.
Key Words: Escherichia coli, Nitrofurantoin, Fluoroquinolones.

Introduction: 

Urinary Tract Infection (UTI) is the third most common cause of hospital visits in our country.¹  A multitude of factors, including the narrow spectrum of bacteria causing community-acquired UTI, severity of the ailment, the threat of complications and the most important is the absence of culture-sensitivity facilities in many places, compels the physicians to start antibiotics empirically.² The most suitable antibiotic for empirical therapy should have a low resistance rate, should achieve a significant urinary concentration , be cost-effective and  free of adverse effects and moreover should be able to satisfy patient compliance.³  Regarding the acceptable resistance rates, the Infectious Diseases Society of America recommends an antibiotic for empirical therapy only if <10-20% of the urinary pathogens are resistant to it.³

Shamim Mumtaz  

Abdul Khan Bari 

Ahsan Ahmad Alvi

Sajid Hussain Shah

Islamic International Medical College-Trust

Riphah University

Rawalpindi

This is because in vivo therapeutic results correlate with in vitro sensitivity patterns.²   UTI caused by E. coli are one of the most common extra- intestinal infections in females and because of their high incidence, are the focus of most epidemiologic studies.4 The source of E. coli for these infections is a person's intestinal tract.⁴  Most of the infections caused by E. coli, are susceptible to many oral antibiotics, although resistance is increasing to some of the commonly used antimicrobials.⁵ Trimethoprim-sulfamethoxazole seemed to be an effective antimicrobial agent in the past decades but resistance has increased towards this effective antimicrobial agent.   Over the past decade, the prevalence of drug resistance in E. coli has further increased dramatically, still complicating management of these infections. A more serious concern has been the gradual increase in fluoroquinolone (e.g., ciprofloxacin) resistance among UTI isolates.⁶ An alternative regimen such as nitrofurantoin, a fluoroquinolone, or an oral third-generation cephalosporin may be a better empiric choice in some areas.⁵  Nitrofurantoin —the older, narrow-spectrum drug has little resistance among E. coli, but it may have lower cure rates (85%), compared with those of other first-line agents (90%–95%), and more side effects, especially acute and chronic pulmonary syndromes.⁵ There is a paucity of data on the efficacy of nitrofurantoin for the treatment of acute UTI. Evidence-based use of this drug is becoming increasingly important as resistance towards trimethoprim-sulfamethoxazole and fluoroquinolone among uropathogens is increasing but they require further study.³ An older, narrow-spectrum drug nitrofurantoin—has led to little resistance among E. coli, can be an effective empirical therapy against urinary pathogens which require further study. The empirical therapy of urinary tract infections (UTI) relies on the predictability of the agents causing UTI and knowledge of their antimicrobial susceptibility pattern. Keeping in view the development of resistance of urinary pathogens against the commonly used antimicrobials and knowledge of the sensitivity of nitrofurantoin, this study was carried out to determine the frequency of drug resistance in urinary E. coli especially in regard to nitrofurantoin , an effective oral antibiotic which can be used to treat urinary tract infections, E.coli isolates sensitive or resistant to the other antibiotics were analyzed for their sensitivity to nitrofurantoin.
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