Isolation, identification, and sensitivity profile of Bacillus spp. in co-infection with respiratory viruses

This study investigates the occurrence and antimicrobial susceptibility of <i>Bacillus spp</i>. in pediatric patients with viral respiratory infections admitted to intensive care units. Secondary bacterial infections are known to exacerbate the severity of viral respiratory diseases and represent a major cause of morbidity and mortality during pandemics, including COVID-19. A total of 659 respiratory samples from children with respiratory symptoms hospitalized in five hospitals were analyzed. Bacterial co-infections were identified by inoculation in BHI medium and confirmed by MALDI-TOF. Antimicrobial susceptibility testing was performed using the Kirby-Bauer method, following EUCAST guidelines. Among 166 cases of bacterial co-infection, 20 (12.05%) were attributed to <i>Bacillus spp</i>., with a predominance in patients infected with respiratory syncytial virus (55%). The isolates showed high susceptibility to vancomycin (85%), imipenem (80%), erythromycin (70%), and ciprofloxacin (65%). These findings reveal that <i>Bacillus spp</i>., often considered an environmental contaminant, may play a clinically relevant role in pediatric viral co-infections, particularly in severe respiratory cases. This study contributes novel data to a poorly explored area of pediatric infectious disease research, emphasizing the need for routine susceptibility testing to optimize antimicrobial therapy. The results provide a foundation for future molecular studies on <i>Bacillus spp</i>. virulence and resistance mechanisms, supporting evidence-based management and infection control practices in critical care settings.