Comparação da virulência e potencial terapêutico da fagoterapia em cepas ambientais e clínicas de Staphylococcus saprophyticus

Abstract

Staphylococcus saprophyticus is a gram-positive, catalase-positive and coagulase-negative bacterium that is part of the normal microbiota of the human skin and genitourinary tract. Under certain conditions, it can become an opportunistic pathogen, causing urinary tract infections (UTIs), particularly in young sexually active women. Despite its widespread environmental distribution, few studies have investigated the presence of virulence-associated genes or the pathogenic potential of this organism in environmental isolates. Guanabara Bay, located in Rio de Janeiro, is a highly polluted water body used for recreational activities and fishing, increasing the risk of exposure to environmental pathogens. Thus, investigating the virulence mechanisms of environmental isolates of S. saprophyticus is essential for identifying potential health threats, especially in areas of intense human-environment interaction. This study aimed to compare the virulence of S. saprophyticus strains isolated from Guanabara Bay and hospital patients in Rio de Janeiro, Brazil. A total of 40 strains (20 from Guanabara Bay and 20 from clinical patients) were analyzed, evaluating the presence of virulence genes (aas, ssp, ureC, dsdA, uafA, sssF, and sdrI) by PCR method, biofilm formation capacity, the impact of subinhibitory concentrations (sub-MIC) of ciprofloxacin, pathogenicity in an in vivo model using Tenebrio molitor larvae, and the therapeutic potential of bacteriophages. The results demonstrated a widespread distribution of virulence genes in strains from both sources, except for the sdrI gene, which was not detected in any of the isolates. Also, biofilm formation capacity was observed in 95% of the strains, with greater adherence among clinical isolates. Exposure to sub-MIC ciprofloxacin induced an increase in biofilm formation in 50% of the strains, with strain-dependent effects. Virulence tests in T. molitor revealed that aquatic and clinical strains exhibited similar pathogenic profiles, and survival curve analysis showed no significant differences between the groups. Regarding phage therapy, three tested bacteriophages exhibited lytic activity against 57% of the evaluated strains, while one, phage CSF, reduced biofilm formation in 92.5% of the isolates, including strains not susceptible to lysis. The findings of the current study indicate that environmental S. saprophyticus strains possess pathogenic potential comparable to that of clinical strains, representing a public health risk in the recreational waters of Guanabara Bay. These results emphasize the importance of environmental monitoring and control strategies. Additionally, the research highlights the potential of phage therapy as a promising approach for treating bacterial infections.