Molecular characterization and prevalence of Bacillus species isolated from Saudi hospitals

OBJECTIVE: This study highlighted the dissemination of Bacillus species (including drug-resistant species) in public hospital environments and calls for the design of optimal strategies to curb their spread. This a critical consideration for all health care systems such as caring for the increasing number of immune-compromised patient. METHODS: A total of 528 swab samples were collected from the environments of different Saudi hospitals. Swab samples were collected by swabbing approximately 5 cm(2) of different surfaces at each site using pre-moisturized cotton swabs with 1 mL of neutralizing buffer. The swabs were transported in cool boxes with ice packs within 2 h of collection. Isolation and identification were performed according to conventional bacteriological, semi-automated and molecular characterization methods. Antibiogram typing was carried against different groups of antimicrobial agents. RESULTS: The most prevalent of the isolated Bacillus species were Bacillus cereus (46.6%) followed by Bacillus subtilis (38.1%); the least prevalent was Bacillus pumilus (1.1%). Most Bacillus isolates (25.6%) were isolated from the Department of Internal Medicine followed by the Emergency Department (18.8%), while the operating rooms had the lowest prevalence (4.5%). Antimicrobial susceptibility testing revealed high levels of resistance in Bacillus isolates to β-lactams and tetracycline. Overall, 21.6% of isolates showed multi-drug resistance to three or more antibiotics (21.6%). Antibiogram typing of the 176 isolates revealed 45 antibiotypes; the most common was antibiotype 31, which included 32 isolates (18.2%); this particular antibiotype was resistant to both penicillin and cefoxitin. CONCLUSIONS: Analyses identified the high dissemination of Bacillus species in several hospital environments with high resistance to β-lactams and tetracycline antibiotics. Molecular analysis also revealed the existence of genetic diversity among the Bacillus isolates investigated. Thus, monitoring the hospital environment is an important tool in the prevention of hospital-associated infection by Bacillus species.