Phenotypic and Molecular Identification of Bacteria Involved in Decubitus Ulcers

Bacterial secondary infection of pressure ulcers (bedsores), so called as decubitus ulcers, leads to ulcer development and it interferes with the healing process. Thus, such infections can be lethal due to the sepsis if no constructive medicinal measures regarded. Drug resistance of bacteria in pressure ulcers leads to healing inhibition. Molecular identification of bacteria involved in such infections seem necessary as culture and phenotypic approaches may result in misidentification. . The purpose of this study was to isolate and identify aerobic bacteria detected in bedsores in three Hospitals: Rasool-e-Akram, Imam Hossein and Tajrish Shohada Hospitals, Tehran, Iran.
To this end, decubitus ulcer samples of 49 patients were obtained using sterile swabs. After direct microscopic examination, the swabs were used to streak BHI agar plates supplemented with %5 defibrinated sheep blood for enrichment of probable aerobic cultures. Bacterial isolates diagnosed by biochemical tests. Antibiotic susceptibility of the isolates determined based on CLSI guideline. For molecular identification, PCR amplification of the 16S rRNA gene performed using Eubacterial universal primers. Then, the PCR products were sequenced and the nucleotide sequences of the PCR products were analyzed by BLASTN similarity search program available at NCBI.
Among the isolates, Pseudomonas aeruginosa (36%) had the highest frequency, followed by Staphylococcus aureus (32%) and Escherichia coli (30%). The frequencies of Klebsiella pneumonia and Proteus spp. were 10% and 8%, respectively. Most of the isolated bacteria showed a widespread antibiotic resistance. Molecular identification of the bacterial isolates resulted in 6 isolates of Escherichia coli, two isolates of each of Proteus mirabilis and Shigella spp., 4 isolates of Enterobacter cloacae, and 1 isolate of each of Cronobacter sakazakii and Morganella morganii.
Results showed that Pseudomonas aeruginosa and Staphylococcus aureus as the most frequent bacterial species detected in pressure ulcers; however, bacterial prevalence may be different in different hospital wards.