Bacteriological Profile of Diabetic Foot Ulcer With Special Reference to Biofilm Formation

Introduction Diabetes mellitus is a metabolic disorder characterized by abnormally high sugar levels in the blood for prolonged periods of time. The world's largest number of diabetics resides in India, making it the world's diabetic capital, with a diabetic foot ulcer (DFU) incidence of around 8-17%. Due to the polymicrobial and multidrug resistant (MDR) nature of DFUs, antimicrobial susceptibility testing is of high importance to help treat patients effectively and prevent the development of MDR bacteria. The ability to form biofilms is a significant additive to virulence of an organism that causes an able strain to be resistant to more antibiotics as compared to a free-living strain, thereby further delaying the healing of DFUs. Materials and methods This study included 74 samples collected from patients with DFUs, out of which 69 (93.24%) yielded growth on culture. Gram staining was done for the direct microscopy, isolation, and determination of organism, and the detection of biofilm formers using Congo Red Agar plates. Data were tabulated and statistically analyzed. Results Out of 74 samples collected, 69 (93.24%) yielded growth on culturing, with 5 (6.76%) cultures coming back negative. On Gram staining, 42 (56.8%) samples showed Gram-positive cocci and 53 (71.6%) showed Gram-negative bacilli. On isolating organisms from the samples, 16 (21.7%) samples had Pseudomonas aeruginosa, followed by Klebsiella pneumoniae at 13 (17.6%) and Proteus mirabilis and Escherichia coli at 11 each (14.9%), indicating a Gram-negative bacteria predominance. Of the Gram-positive bacteria isolated, Staphylococcus aureus stands at two (2.7%) and Streptococcus pyogenes at one (1.4%). The prevailing monomicrobiality could be attributed to antibiotic administration prior to sample collection. On antibiotic sensitivity of organisms tested against each antibiotic, more than 75% of tested samples were resistant to ampicillin, cefuroxime, and erythromycin, and around 70% and more of tested samples were sensitive to ertapenem, meropenem, amikacin, gentamicin, benzylpenicillin, vancomycin, and clindamycin. Out of the 69 positive cultures, 29 (42.03%) yielded biofilm formers. Pseudomonas aeruginosa was the predominant biofilm former with 10 (34.48%) of 29 of total biofilm-forming isolates, followed by E. coli and K. pneumoniae with five each (17.24%) and Proteus mirabilis with three samples (10.34%). Regarding strains forming biofilms according to bacterium species, S. aureus was predominant, with 100% (two out of two samples) of isolates forming biofilms. Staphylococcus aureus was followed by Pseudomonas aeruginosa with 62.5% (10 out of 16 samples), Acinetobacter baumannii (two out of four samples) and Enterobacter cloacae (one out of two samples) with 50% each, E. coli with 45.45% (5 out of 11 samples), and K. pneumoniae with 38.46% (5 out of 13 samples) of isolates forming biofilms. It should be noted that only two S. aureus, four A. baumannii, and two Enterobacter cloacae samples were isolated in comparison to a larger number of Gram-negative bacteria. This study has found that 100% of multidrug-resistant organisms (MDROs) are biofilm formers. Conclusion The ability to form biofilms adds immensely to the virulence and antibiotic resistance. Detection of biofilm formers is non-invasive and convenient to measure and would help provide insight into antibiotics to be administered to the patient, thereby reducing development of MDROs and reducing healing time.