Prevalence of bacterial isolates and change in their antibiotic susceptibility patterns in urinary tract infections- A five year retrospective study

Urinary Tract Infection (UTI) continues to be one of the commonly occurring infections in medical practice despite the widespread availability of antibiotics. Presence of risk factors like elderly age, diabetes, immune-suppression, and other comorbidity pose a challenge in its treatment. Over the years, the etiology and antibiotic resistance of the uropathogens has been inconsistent. Therefore, it is important to determine the causative agents of UTI and their resistance patterns locally, in each region, so that appropriate empiric therapy can be started before the culture and antibiotic sensitivity results are available. This study aims to highlight the prevalence of uropathogens and determine the antibiotic sensitivity pattern over the period of five years.The urine samples from patients with suspected urinary tract infections (UTI) received in the laboratory at Nanavati Max Super speciality hospital were processed by standard protocol from January 2018 to December 2022. Antibiotic susceptibility test for the bacterial isolates was carried out by the VITEK2 automated system and interpreted as per CLSI guidelines. The data collected over the study period of five years was interpreted by using the WHO Net Antibiotic Susceptibility Surveillance Software in February 2023. From a total of 8068 urine samples received over five years, uropathogens were isolated in 4209 (52.16%) samples. E.coli was the most common isolate causing UTI, with prevalence of 380(46.7%) in 2018 and 480(50.6%) in 2022 of total samples. Amongst gram positive organisms, a rise in Enterococcus species was seen from 41(5%) in 2018 to 87(9%) in 2022, with significantly fewer Staphylococcus species isolated, from 32(4%) in 2018 to 7(0.7%) in 2022. The Enterobacteriaceae showed high sensitivity to Amikacin, Tigecycline and Meropenem all throughout the study. However, rise in resistance to Nitrofurantoin and Fosfomycin, antibiotics commonly used for UTIs, was observed. Also the prevalence of Extended Spectrum of Beta lactamase (ESBL) producers decreased from 213(36%) to 127(17%) with a rise in Carbapenemase producing Enterobacteriaceae from 48(8%) to 298(40%) over the five years study period.Amongst Lactose Nonfermenting gram negative bacilli only 32 % were sensitive to Carbapenems and 37% sensitive to Aminoglycosides.By 2022, Enterococcus species showed an increase in sensitivity to Nitrofurantoin (27%), High level Aminoglycosides (37%), Fluoroquinolones (25%) and Ampicillin (37%).The change in antibiotic sensitivity patterns over time and rise in resistance to antibiotics commonly used in empirical treatment of UTIs warrants the need for regular surveillance, so the physicians can be updated regarding the most prevalent organism and its susceptibility and the empirical treatment for UTIs can be modified accordingly. This can help curb indiscriminate use of antibiotics and development of antibiotic resistance.