Comparative Evaluation of Fosfomycin Activity with other Antimicrobial Agents against E.coli Isolates from Urinary Tract Infections

Prevalence of O25b-ST131 clone and fosfomycin resistance in urinary Escherichia coli isolates and their relation to CTX-M determinant

Escherichia coli ST131 clone and H30-R/H30-Rx subclones are the most common multidrug-resistant high-risk clones in UTIs. Antimicrobial susceptibility of fosfomycin was compared to five other agents in consecutively collected 299 urinary isolates using the agar dilution method. Prevalence of the ST131 clone and the occurrence of blaCTX-M were also investigated. Overall resistance to fosfomycin, cefuroxime, and ceftriaxone were 2.7%, 35.4%, and 30.1% respectively. fosA, fosA3, and fosC2 genes were not detected. In isolates resistant to ciprofloxacin (34.7%), the prevalence of ST131 clone was 31.7%, of which 81.8% belonged to H30-R and 66.7% to H30-Rx subclones. None of the isolates of the ST131 clone were resistant to fosfomycin. However, bla_CTX-M occurred in 57.6% of the isolates among this clone, 62.9% in H30-R and 68.2% in H30-Rx subclones. The results of this study suggest that fosfomycin resistance is not prevalent in urinary isolates, however, bla_CTX-Mpositive ST131 clone is quite common.

Susceptibility pattern of oral antimicrobials in uncomplicated UTI: Does fosfomycin still stand effective?

INTRODUCTION

Urinary tract infections (UTIs) are a leading cause of morbidity amongst all age groups and most patients with uncomplicated UTI who visit the OPD are treated with empirical antibiotics without doing any culture analysis. Of all the oral antibiotics used in UTI, fosfomycin is well excreted in the urine and is being used for the treatment of UTIs with a single oral dose.

METHODOLOGY

The current study was planned to determine the resistance amongst uropathogens to various oral antibiotics including fosfomycin isolated over a 4-year period (April 2015 to March 2019).

RESULTS

A total of 22,546 urine samples were received from OPD patients over 4 years and of these, 7,295 isolates were obtained from patients with uncomplicated UTI. About 82% of the isolates were gram-negative bacilli (GNBs). The most common isolate was E. coli 1023 (67.2%) followed by Klebsiella spp 254 (16.7%), and Pseudomonas spp 63 (4.1%). Of all the antibiotics tested, maximum sensitivity in the year 2018 was found to fosfomycin followed by nitrofurantoin for all the isolates tested. There was a statistically significant increase in the resistance pattern for almost all antibiotics tested in gram-negative bacteria (both Enterobacteriaceae and nil fermenters) whereas the increase in the resistance was not statistically significant in gram-positive cocci.

CONCLUSION

It can be easily seen that the level of antibiotic resistance has been increasing even in the community with the rampant injudicious use of antibiotics in humans as well as livestock. As the level of resistance to fosfomycin is still low in the community, it can play a promising role in the treatment of infection in patients with uncomplicated UTI.

Evaluation of in vitro susceptibility of fosfomycin among Enterobacteriaceae isolates from urine cultures: A study from Puducherry

INTRODUCTION:

The increasing drug resistance among Gram-negative uropathogens and a lack of effective oral antibiotics have limited the therapeutic options available for urinary tract infections (UTIs). This shortage of newer antibiotics has paved the way for considering the use of older antibiotics such as fosfomycin. This study aims to evaluate the in vitro susceptibility of Enterobacteriaceae isolates to fosfomycin.

MATERIALS AND METHODS:

In this descriptive study conducted over a period of 6 months, we processed 1500 urine samples. The Enterobacteriaceae isolates were subjected to in vitro susceptibility testing to fosfomycin, in addition to the regularly used urinary antibiotics, by Kirby–Bauer disc-diffusion method.

RESULTS:

Of 1500 urine samples processed, 582 samples yielded the growth of pathogens. Enterobacteriaceae accounted for 392 (67.3%) of the isolates. Among these isolates, lower rates of resistance were observed for imipenem (4.1%) and fosfomycin (13.3%). Relatively higher rates of resistance were observed for nitrofurantoin (35.5%) and amikacin (30.9%). Nalidixic acid, norfloxacin, gentamicin, cefotaxime, and cotrimoxazole showed a high resistance rate of 82.7%, 69.6%, 52.3%, 69.1%, and 71.4%, respectively. All antibiotics, except fosfomycin, were in routine clinical use in our hospital. The low resistance (13.3%) to fosfomycin is indicative of its utility as an excellent urinary antibiotic.

CONCLUSIONS:

Uropathogenic Enterobacteriaceae isolates displayed excellent in vitro susceptibility to fosfomycin. These in vitro findings suggest the unexplored potential of fosfomycin as a superior therapeutic option for treating uncomplicated UTI.