Analysis of Distribution and Drug Susceptibility Test Results of Pathogenic Bacteria in Diabetic Foot Ulcers.

Introduction: This study aimed to determine the pathogen distribution and drug susceptibility of diabetic foot wound secretions in a tertiary hospital in a coastal area of southeastern China to guide clinical antibiotic selection.

Methods: A retrospective analysis was conducted on 212 patients with diabetic foot hospitalized at Xiamen Third Hospital from 2018 to 2023, and foot wound secretions were collected for microbial culture and drug susceptibility testing.

Results: Among 212 cases of patients with diabetic foot wound secretions, 163 cases (76.9%) were cultured with pathogenic bacteria, and a total of 207 strains of pathogenic bacteria were cultured, including 75 strains (36.23%) of Gram-positive (G+) bacteria, 118 strains of Gram-negative (G-) bacteria (57.00%), 14 strains of fungi (6.76%), 120 cases of single microorganism infection (73.62%), 43 cases of mixed infection (26.38%), and 15 strains of multidrug-resistant bacteria (7.25%). The top three pathogenic bacteria were Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. G+ bacteria were dominated by S. aureus. Drug susceptibility results showed that G+ bacteria were highly susceptible to vancomycin, linezolid, tigecycline, quinupristin/dalfopristin, rifampicin, and furotoxin, and somewhat resistant to penicillin, erythromycin, clindamycin, and cefoxitin. Among G- bacterial infections, Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Proteus were the major species. Drug susceptibility testing indicated that carbapenems such as imipenem and ertapenem were the most effective antibacterial drugs against G- strains, followed by amikacin, piperacillin, and tazabactams to which these bacteria were also relatively sensitive, while resistance to penicillins and first-generation cephalosporins increased significantly. We isolated one strain of pathogenic bacteria from a Wagner grade 1 ulcer, which was G+ bacteria. In Wagner grade 2 ulcers, the distribution of pathogenic bacteria was mainly G+ bacteria. In Wagner grade 3 and 4 ulcers, the distribution of pathogenic bacteria was mainly G- bacteria, and the increased rate of mixed infection was mainly due to mixed infection of G+ and G-. Two strains of pathogenic bacteria were isolated at Wagner grade 5, which were mixed infections of G+ and G-.

Conclusions: Pathogenic bacteria in diabetic foot wounds are predominantly G- bacteria, followed by G+ bacteria. As the Wagner ulcer grade increases, the distribution of pathogenic bacteria changes from G+ bacteria to G- bacteria, and the mixed infection rate increases. G+ bacteria are highly susceptible to vancomycin, linezolid, tigecycline, quinupristin/dalfopristin, rifampicin, and furotoxin, and somewhat resistant to penicillin, erythromycin, clindamycin, and cefoxitin. G- bacteria are more sensitive to the antimicrobial drugs ertapenem, imipenem, amikacin, piperacillin tazobactam, and have high resistance to penicillin and first-generation cephalosporins.