Efficacy of Amikacin and Imipenem Against Multi-Drug Resistant Gram-Negative Bacteria Isolated from Wound Infections, Egypt

 Gram-negative pathogens are considered the common cause of wound infections associated with increased mortality and morbidity rates. Antibiotics combination has been used to overcome this problem. In this study, we identify Gram-negative pathogens found in wound infections and assess the in-vitro efficacy of a combination of amikacin and imipenem against the resistant isolated pathogens.

 One hundered fifty gram-negative bacteria were collected from two hundered patients suffering from different wound infections. Patients attended Minia University Hospitals,Egypt at period from January 2019- January 2020 and they were  followed up periodically as a routine work in the hospitals. Swabs streaked on various media as Nutrient agar, MacConkey agar, Eosin methylene blue agar and cetrimide agar. The antimicrobial susceptibility of the identified pathogens was tested using the Kirby-Bauer method. Conventional PCR was used to detect the prevalence of bla-IMP and AAC (6’)-Ib genes. The effect of the tested combination was assessed by checkerboard technique and time-killing assay.

Escherichia coli 38.6% was the most common isolated pathogen, followed by Proteus spp 30%, P. aeruginosa 21.4%, Klebsiella spp. 5.7%, and Acinetobacter baumannii 4.3%. The isolates were completely resistant to Ampicillin/sulbactam, Amoxicillin/clavulanic, Cephalothin, Cefadroxil, Ciprofloxacin, Ceftazidime and Ofloxacin. Bla-IMP was detected in all Klebsiella spp., E. coli (85.2%), A. baumannii (66.7%), Proteus spp. (38.1%) and P. aeruginosa (33.35%). aac(6’)-Ib was detected among E. coli, P. aeruginosa and Proteus spp. The Checkerboard test showed a significant decrease in bacterial count in the presence of combination indicating a synergistic effect with FICIs ≤0.5. Time-kill assay showed a significant decrease in the bacterial count after 12h.

 The studied combinations of antibiotics showed synergistic effects against the tested Gram-negative bacteria which can help in the control and treatment of serious wound infections.