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Fosfomycin: an oral treatment option for multi drug resistant uropathogens.

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Introduction Urinary tract infections (UTIs) are commonplace in both the community and hospital environment where it is accepted clinical practice to treat empirically. Consequently, this has led to an alarming increase in antimicrobial resistance in frequently prescribed oral treatment options. In light of the global shortage of newly discovered antibiotics, there is a need to relook at older antimicrobial agents, such as fosfomycin, to fill the gap in therapeutic guidelines. Purpose of the Study It was the purpose of this study to ascertain the extent of antimicrobial resistance in commonly isolated urinary pathogens to frequently prescribed antibiotics. This was done with the intention of bringing to light the severity of the situation. We also looked at fosfomycin as a possible alternative to the currently recommended treatment options most especially in multi drug resistant (MDR) infections. Method A retrospective analysis of antimicrobial susceptibility data of positive urine specimens collected during 2018 – 2020 was performed. Additionally, fosfomycin susceptibility testing was performed in 178 stored MDR uropathogenic isolates using the gold standard agar dilution method. We also compared agar dilution (reference method) to disk diffusion and E test as they are less labour intensive. All data and isolates were obtained from RK Khan Laboratory located in KwaZulu Natal, South Africa. The Clinical and Laboratory Standards Institute guidelines was utilised as the guiding document. Results While conducting the laboratory information system (LIS) based review, it was determined that within the study time frame, 3044 common urinary pathogens were isolated, with Escherichia coli being the most frequent cause of UTI (1603: 53%), followed by Klebsiella spp (437: 14%). Both organisms showed high rates of resistance to amoxicillin clavulanic acid (AMC) (29.8% and 42.3%) and ciprofloxacin (37.7% and 30.4%) which are popular treatment options. Our study on fosfomycin susceptibility in MDR uropathogenic isolates revealed that of the 178 isolates, E. coli was the most prevalent isolate (97: 55%), followed by Klebsiella spp (55: 30.9%). E. coli had a susceptibility rate of 93.8% to fosfomycin, while Klebsiella spp had susceptibility rate of 78%. Categorical agreement was achieved between agar dilution and disk diffusion at 91%, although there was a high rate of false susceptibility at 42.9%. Categorical agreement between agar dilution and E tests at only 89% did not meet CLSI guideline. Conclusion While E. coli remains the most commonly isolated uropathogen, resistance rates for both E. coli and Klebsiella spp to frequently prescribed oral treatment options are alarmingly high, leaving clinicians very little in the way of viable treatment options. There is a need to keep abreast of current antimicrobial resistance trends as well as look at alternative treatment options. To that end, the use of fosfomycin as an alternative oral treatment option in a UTI is a viable solution, most especially when the infection is caused by a MDR E. coli. Lastly, though laborious, agar dilution remains the most reliable method in establishing antimicrobial susceptibility in fosfomycin.


Masters Degree. University of KwaZulu-Natal, Durban.