Antibiotic resistance and biofilm‐forming ability of α‐toxin‐positive Clostridium septicum isolates worsen patient prognosis

A total of, 78 Clostridium septicum (CLSE) isolates were screened for genes encoding: α‐toxin, flagellin, and resistance to vancomycin ( VANg ). The isolates were also tested for their ability to form biofilm and their antibiotic susceptibility. All isolates were positive for α‐toxin and flagellin genes. However, only 19 isolates (24.3%) showed prevalence for VANg . We observed the strongest capacity to form a biofilm (100%) in isolates from patients with oncologic or septic and febrile diagnoses. This percentage was also very high in patients with colitis and gastrointestinal hemorrhage (72.7%). No less than 43 isolates showed antibiotic resistance, and 21 were multidrug‐resistant (MDR). Interestingly, our studies showed a correlation between antibiotic resistance and biofilm formation. A statistically significant difference was observed between biofilm‐forming MDR isolates and those with low/no biofilm‐forming ability. However, the most impressive observation was the correlation with mortality rate. While the overall mortality rate for CLSE infections was 16.7% (13/78), the mortality rate for patients infected with MDR isolates forming biofilm moderately or strongly reached 38.1% (8/21). This number increased even further when only infections with the biofilm‐forming VANg ‐positive isolates were considered (61.5%; 8/13). Therefore, the ability of a VANg ‐positive CLSE isolate to form a biofilm has been suggested as a biomarker of poor prognosis.