Introduction: Health care-associated infections caused by metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa are a significant growing concern in patients with burns worldwide. The aims of this study were to determine the antibiotic susceptibility of and detect the presence of MBLs among P. aeruginosa isolates and assess their clonal relationship using enterobacterial repetitive intergenic consensus (ERIC)-PCR. Methods: Non-duplicated clinical isolates (160) of P. aeruginosa were collected from patients with burns at the Motahari Hospital in Tehran, Iran. All isolates were identified using standard laboratory methods and further characterized for antimicrobial susceptibility. Any carbapenem-resistant isolates were then examined for MBL production by the E-test and MBL-encoding genes were detected by PCR. The clonal relatedness of MBLproducing isolates was assessed by ERIC-PCR. Results: For multidrug-resistant isolates, the highest rates of susceptibility were observed for colistin 160 (100%), polymyxin B 160 (100%), and ceftazidime 32 (20%). In total, 69 (43.7%) isolates were identified as MBL producers. Twenty-eight (17.5%) isolates were positive for the bla VIM-1 gene followed by the bla IMP-1 (15.6%) and bla SPM-1 (5.6%) genes. ERIC-PCR revealed three separate genotypes, where type A (76.8%) was the most prevalent, followed by B (20.3%), and then C (2.9%). Conclusions: Our present study found that the bla IMP-1 and bla VIM-1 genes were present at a significant frequency and also detected the bla SPM-1 gene in P. aeruginosa isolates for the first time, highlighting the need for establishing suitable infection control measures to successfully treat patients and prevent further spread of these resistant organisms among patients with burns.

Background: Listeriosis can be fatal for vulnerable groups of society. The disease has been widespread in recent years due to the large consumption of dairy and meat products. There is little information about the susceptibility of antibiotics and the pattern of Listeria monostigenesis gene resistance in Iranian society. Accordingly, the present study was conducted to investigate the antibiotic susceptibility and genetic resistance pattern of Listeria monosteogenesis strains isolated from different clinical and environmental sources. Materials and methods: In this study, 55 isolates were tested for antibiotic susceptibility by disk diffusion in agar and genetic pattern by polymerase chain reaction (PCR). Results: 91% and 83% of the strains were resistant to streptomycin and Trimethoprim/sulfamethoxazole respectively. The result of PCR of antibiotic resistance genes showed that the prevalence of ermA, ermB, strA, tetA, tetS and ermC genes in isolates of Listeria monocytogenes was 50.90% (28/55), 21.81% (12/55), 89.9% (49/55), 0% (0/55), 21.81% (12/55) and 0% (0/55), respectively. Conclusion: Due to the presence of 1/2a and 1/2c serotypes in isolated isolates and the presence of marker virulence genes in these strains, these isolates have potential for biological risks and listeriosis disease. Existence of this genetic pattern and resistance pattern can be partly due to the use of antibiotics during the production of dairy products. Regarding results of this study, the manner and rate of using animal antibiotics can be managed.