Background: Carbapenem antibiotics consider the primary treatment choice for serious Pseudomonas aeruginosa infection. Hence, the evolution of carbapenem resistance mediated by acquiring genes encoding class b enzymes is of global concern. The purpose of this article research is to explore the prevalence, drug resistance profiles, and metallo-βlactamases (MβLs) production in extensively drug-resistant carbapenem-resistant P. aeruginosa (XDR-CRPA). Methods: P. aeruginosa isolates were collected and identified according to conventional methods. Antibiotic resistance patterns were determined by single disk diffusion. Minimum inhibitory concentrations (MICs) of (imipenem, meropenem, ceftazidime, piperacillin/tazobactam, levofloxacin, and gentamicin) were determined for CRPA. A subset of the isolates collection consisting of the XDR-CRPA with the highest MICs to imipenem and meropenem were selected for the phenotypic screening of carbapenemases and MβLs production capability using the modified carbapenem inactivation (mCIM) and imipenem-EDTA combined disk (MβL-CD) methods, respectively. Then, molecular analysis, including identification by the specific primer of 16S rRNA and detection of MβL genes using polymerase chain reaction (PCR) was performed to the XDR selected isolates. Results: Among 100 P. aeruginosa isolated throughout this period, 59% exhibited reduced susceptibility rates to carbapenems. A total of 20.3% and 57% of CRPA isolates were MDR and XDR, respectively. MIC values of the CRPA revealed that these isolates exhibited high MIC 50 and MIC 90 to the six selected antibiotics. The findings of the (mCIM) assay displayed identical concordance results with the MβL-CD. Molecular investigation technique assured that 10 (90.9%) and 2 (18.1%) of the 11 XDR selected isolates are positive for bla NDM-1 and bla VIM-1 genes, respectively. Polymyxin B and colistin followed by aztreonam were the most effective antibiotics used for curing infections caused by XDR Pseudomonas aeruginosa. Conclusion: The prevalence of high XDR-CRPA in our study is a critical problem. Our present study found that the bla NDM-1 was present at a significant frequency among the selected XDR isolates, highlighting the need for establishing strict antimicrobial policies to avoid the prompt spread of these isolates.

Infection is an important cause of mortality in patients with burns. Rapid emergence of hospital pathogens and antibiotic-resistant organisms necessitate periodic evaluation of bacterial colonization patterns and antibiogram sensitivity in burn wards. Sixty isolates from wounds of burns were collected from two hospitals in Cairo, Egypt along the period of 12 months in 2013. Antibiotic sensitivity of these isolates was assessed by single disk diffusion method. Multi drug resistance percentage and the most prevalent resistance phenotype among bacterial isolates were recorded. In addition, 19 essential oils were tested against the MDR isolates. The most potent oils were analyzed by GC-MS to determine their main chemical constituents. According to microbiological and biochemical identification method, Pseudomonas aeruginosa was the most dominant organism 23 (38%), followed by Staphylococcus aureus 16 (27%), Klebsiella spp. 11 (18%), Acinetobacter spp. 4 (7%). Three isolates of Escherichia coli (5%) and three isolates of Proteus spp. (5%). Piperacillin-tazobactam, imipenem and linezolid antibiotics were the most effective antibiotics against Pseudomonas aeruginosa, Enterobacteriaceae and S. aureus isolates respectively. Cinnamon and thyme essential oils were the most potent oils against the multi drug resistant burn wound isolate. Cinnamaldehyde (60.7%) and ρ-cymene (50%) were the major chemical constituents in cinnamon and thyme essential oils, respectively. It is clear that antibiotic resistance levels are high among the examined bacterial isolates of burn wounds. This study could be useful for physician to better choice of empiric therapy. Cinnamon and thyme may be used as a promising an alternative medicine for the treatment of burn wound infections.

The evaluation of the combined effects between the antibiotics against P. aeruginosa is among the efforts to counteract its antimicrobial resistance. This study aimed to evaluate the possible combined effect of colistin or polymyxin-B with carbapenem antibiotic group against clinical isolates of multi-drug resistant P. aeruginosa. Strains were isolated from biological samples of hospitalized and nonhospitalized patients with any type of infection related to this pathogen. Only carbapenem-resistant strains were included in the study. After determining the minimum inhibitory concentration (MIC) of antibiotics against the strains by broth microdilution test, the checkerboard method was used for evaluation of any possible effect of both colistin or polymyxin-B with imipenem or meropenem. Fifty-nine strains of reduced susceptibility to carbapenems were recovered. It was noted that (45.7%) of strains had an imipenem MIC=1024 µg/ml and (28.8%) had a meropenem MIC=512 µg/ml. The checkerboard technique demonstrated that the ten representative strains showed reductions in their minimal inhibitory concentration (MIC) for at least one of the antibiotics in the combinations evaluated. These results from the in vitro evaluation suggest that combinations of colistin and polymyxin-B may significantly reduce the MICs of the carbapenem antibiotics tested.

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