Resistance Pattern of Nitrofurantoin of Uropathogens in Different Age Groups at Dr. Lal Path Labs, National Reference Laboratory, Rohini, Delhi

Aims and Objectives: This study was undertaken to highlight the resistance pattern of Nitrofurantoin among 5162 UTIs causing isolates at Microbiology Department of Dr. Lal Path Labs between April to June 2019.

Materials and Methods: This retrospective study was performed in Department of Microbiology at Dr. Lal Path Labs, Delhi during period April to June 2019. Standard loopful midstream urine samples collected in a sterile container were inoculated on UTI Chromagar and incubated overnight at 37ºC and demonstrating significance colony count of ≥105 CFU/ml. Common Enterobacteriaceae group of isolates and Gram positive isolates identified by MALDI TOF-MS (Bruker, Daltonics) were included in this study. To determine Nitrofurantoin resistance by VITEK-AST (Biomerieux) system on 280/P628 antibiotic susceptibility testing cards respectively as per as CLSI M100-S-29. Proteus spp, Pseudomonas spp., Acinetobacter spp, of complicated UTI isolates were excluded from this study.

Results: Of the 29485 urine samples tested during April to June 2019, 5162 (17.5%) were culture positive. Out of the 5162 positive isolates 2856 (55.3%) were isolated from female patients and 2306 (44.7%) from male patients. The most common bacterial isolates were members of Enterobacteriaceae 4728 (91.5%) and Gram positive were 434 (8.5%). The most predominant age group infected with uropathogens were elderly adults ≥ 50 years of age constituted 58.1% of the UTIs culture positive cases. Klebsiella pneumoniae demonstrated highest resistance of 92.3% whereas Staphylococcus aureus demonstrated the least resistance of 8.3%.

Discussion and Conclusion: The alarming substantial resistance to Nitrofurantoin in decreasing order has been noticed in Enterobacteriaceae i.e., Klebsiella pneumonia (92.3%), Enterobacter spp.(58.2%), Citrobacter spp (42.6%) and Gram positive Enterococcus spp. (45.6%) which is across all age groups. Most susceptible to Nitrofurantoin were Escherichia coli (69.9%) in Gram negative and Staphylococcus aureus (91.7%) in Gram positive. This finding emphasis the need of robust restriction of Nitrofurantoin antibiotic policy and usage to uncomplicated UTIs caused by Escherichia coli and Staphylococcus aureus.