Hemolysin production, salt tolerance, antibacterial resistance, and prevalence of extended spectrum ?-lactamases in Proteus bacilli isolated from clinical and environmental sources

Introduction and objective: Proteus bacilli are opportunistic members of Enterobacteriaceaeand Proteus mirabilis is among the most common causes of community or hospital acquired urinary tract infections (UTI) in many countries. In the present study hemolysin production, salt tolerance and resistance to antibacterial agents in environmental and UTIs samples were compared.

Materials and methods: Bacteria were isolated from UTIs (n=80), chicken skin (n=34) and soil (n=10). Resistance to 10 antimicrobial agents was determined by agar dilution method. In addition, β-lactamase and extended spectrum beta-lactamases (ESBLs) were also determined by nitrocefin disks and double disk diffusion methods respectively. 

Results: Totally, 62.9% of the isolates showed resistance to 8.5% sodium chloride, and the difference in salt tolerance was significant in respect to species and origin of the samples. However, no significant difference in hemolysin production was detected in respect to species and origin of the samples. Resistance to trimethoprim-sulfamethoxazole (Sxt), amoxicillin (Amx) and chloramphenicol (C) were high (48.4% 41.9%, and 32.26% respectively), while sensitivity to β-lactams except amoxicillin was high (≥93.3%). β-lactamase production was found for 33% of the isolates and the MIC₉₀of Amx resistance isolates was high, but reduced several folds in presence of clavulanic acids, however ESBL phenotype was not observed for any of the isolates.

Conclusion: Hemolysin production was not significantly different in samples isolated from different sources, however isolates from soil were significantly more tolerance to salt (P=0.001). Resistance to some antibacterial agents was significantly higher in the isolates from UTIs and chicken skins in comparison with the soil samples. This is important in the case of Amx and Sxt, which are the important antibacterial agents for the treatment of uncomplicated UTIs.