Bacterial Profile and Antimicrobial Susceptibility Patterns in Urine Isolates from Patients with Kidney Stones: A Preliminary Study from Najaf, Iraq

Abstract

Background: Kidney stones are a common urinary tract disorder that may be associated with bacterial colonisation and urinary tract infections. The identification of bacterial pathogens and their antimicrobial susceptibility patterns is important for appropriate management of suspected infections in patients with nephrolithiasis. Objective: This study aimed to investigate the bacterial profile of urine specimens obtained from patients with kidney stones and to determine the antimicrobial susceptibility patterns of the recovered bacterial isolates. Methods: A total of 24 urine specimens were collected from patients with kidney stones who attended Al-Hakim General Hospital, Najaf, Iraq, between October 2024 and February 2025. The specimens were processed by conventional microbiological methods, including culture on MacConkey agar, mannitol salt agar, and eosin methylene blue agar. Bacterial isolates were identified based on cultural characteristics and Gram staining. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion method on Mueller–Hinton agar against rifampin, cefixime, trimethoprim, amoxicillin, and doxycycline. Results: Bacterial growth was detected in 17 of the 24 examined urine specimens (70.8%). A total of 21 bacterial isolates were recovered. Escherichia coli was the most frequently isolated organism (33%), followed by Staphylococcus aureus (29%), Pseudomonas aeruginosa (24%), and Staphylococcus epidermidis (14%). Gram-negative bacteria accounted for 57% of the isolates, whereas Gram-positive bacteria accounted for 43%. Among E. coli isolates, the highest resistance was observed against cefixime (100%), followed by rifampin and amoxicillin (85.7% each), doxycycline (71.4%), and trimethoprim (57.1%). S. aureus showed the highest resistance to amoxicillin (66.7%), followed by cefixime and trimethoprim (50% each). Conclusion: The study demonstrated a relatively high frequency of bacterial growth in urine specimens from patients with kidney stones, with both Gram-negative and Gram-positive organisms recovered. E. coli was the predominant isolate and showed considerable resistance to several tested antimicrobial agents. These findings emphasise the importance of bacterial identification and antimicrobial susceptibility testing when urinary infection is suspected in patients with kidney stones. Larger studies with appropriate control groups and comprehensive clinical data are needed to further clarify the relationship between nephrolithiasis, bacterial infection, and antimicrobial resistance.