Microbiological characterization of neuropathic diabetic foot infection: a retrospective study at a Portuguese tertiary hospital

Abstract Diabetic foot infection imposes a significant burden and is the major cause of nontraumatic limb amputation. Adequate patient management with effective antibiotic therapy is crucial. This retrospective cohort study aimed to characterize the microbiology and resistance patterns of moderate to severe neuropathic diabetic foot infection in patients hospitalized at a tertiary referral hospital between January 2020 and June 2023. Deep tissue specimens from ulcers were collected for culture. Sixty inpatients were included (62% male, mean age 59.1 ± 11.5 years). Osteomyelitis was present in 90% of the patients. Among 102 microorganisms (average of 1.91 ± 1.25 pathogens per patient), 60.8% were gram-positive bacteria, 31.4% were gram-negative, 3.92% were anaerobic bacteria, and 3.92% were fungi. Staphylococcus aureus (19%) and Enterococcus faecium (17%) were the most common. Pseudomonas aeruginosa (8%) and bacteria of the Enterobacterales family (24%) accounted for all the isolated gram-negative bacteria. Sixteen percent of Staphylococcus aureus and 67% of coagulase-negative Staphylococci were resistant to methicillin. Resistance to ampicillin was found in 11% of Enterococci. All Pseudomonas aeruginosa isolates were sensitive to piperacillin-tazobactam, ceftazidime, or cefepime. Among the Enterobacterales, resistance rates were 35% for piperacillin-tazobactam, 38% for ceftazidime, 21% for cefepime, and 13% for carbapenems. Although the prevalence of methicillin-resistant staphylococci was lower than that in other studies, carbapenem resistance among gram-negative bacteria warrants attention. This study highlights the importance of understanding local epidemiology for effective diabetic foot infection management and resistance mitigation.