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Abstract Background and Objective: Increasing prevalence of methicillin resistant Staphylococcus aureus strains (MRSA) with their multidrug resistance potential causes difficulties in the treatment of infections due to these bacteria. Hence, the detection and determination of the frequency of MRSA strains via phenotypical and molecular methods is necessary in different parts of the county. Material and Methods: In this cross- sectional study, 150 Staphylococcus aureus strains were collected from different clinical samples in the hospitals located in Shiraz and Jahrom, Iran. To detect methicillin resistant Staphylococcus aureus strains, we used phenotypical methods such as disc diffusion and minimum inhibitory concentration by E-Test, and PCR molecular method for mass gene. Results: The frequency of methicillin resistant Staphylococcus aureus was 63 strains (42%) using disc diffusion and E-Test. while in PCR method, in addition to 63 strains, nine other isolates, which were sensitive to oxacillin by disc diffusion and E-Test, possessed also mecA gene. By and large, 72 isolates (48%) had methicillin resistance gene. Conclusion: Given the results of phenotypical and molecular methods, the frequency of methicillin resistant Staphylococcus aureus was relatively high in this area. Thus, the MRSA strains can be detectable as soon as possible by accurate and sensitive methods such as PCR to determinate the effective antibiotics. Keywords: Methicillin Resistant Staphylococcus Aureus, MRSA, MecA Gene, PCR

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Background: Pyogenic infection is a significant cause of morbidity. Infection with multidrug-resistant strains poses a major difficulty in the treatment. The study was conducted to know the bacteriological profile of pyogenic infections and their antibiotic susceptibility.
Methods: A cross-sectional study was conducted in a tertiary care hospital from October 2021 to March 2022. Isolates from pus specimens were subjected to an antibiotic sensitivity test using the Kirby-Bauer method as per CLSI 2021.
Results: Out of 752 samples, etiology could be revealed in 510 (68.4%) specimens. Enterobacterales dominated the profile, with K pneumoniae isolated in the maximum number of specimens. Staphylococcus aureus was the culprit in 14% of the cases. Non-fermenters were isolated in 17% of the cases. Methicillin resistance in S aureus was 67%. Gram-positive cocci showed high sensitivity to linezolid. For both Piptaz and carbapenem, Enterobacterales and non-fermenters showed around 50% and 60% susceptibility, respectively.
Conclusion: Continuous surveillance of the aetiologic agents of pyogenic infections and their antibiotic sensitivity pattern needs to be done to design and implement the antibiotic policy for the infection in our set-up.

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ABSTRACT
Background: The emergence of multi-drug resistant organisms has limited the choice of therapeutic options to treat infections. The lack of development of new antimicrobials paved the way for considering the reassessment of older antibiotics like fosfomycin. In this context, we assessed the in-vitro effect of fosfomycin against carbapenem- resistant Enterobacterales and methicillin-resistant Staphylococcus aureus on bloodstream isolates by agar dilution, disk diffusion and screen agar.
Material & Methods: All the 141 consecutive blood isolates which were resistant to carbapenem and 62 MRSA blood culture isolates were collected over a period of 8 months. The methods such as fosfomycin agar dilution (0.25 µg/ml to 512 µg/ml) , Kirby-Bauer disk diffusion (150μg of fosfomycin + 50μg of glucose -6-phosphate) and fosfomycin screen agar (32 µg/ml, 48µg/ml & 64µg/ml) were performed. All the three methods are interpreted using EUCAST guidelines. The agreement between the new method and the reference method was calculated.
Results: Among the tested isolates, 100 % of MRSA followed by E. coli (86.4%), K.pneumoniae (65.2%) and E.cloacae (50%) were susceptible to fosfomycin. The MIC50 and MIC90 of fosfomycin was 0.5µg/ml and 2µg/ml for MRSA, 16µg/ml and 32µg/ml for K.pneumoniae, 4µg/ml and 16µg/ml for E.coli, 8µg/ml and 32µg/ml for E.cloacae respectively.
Conclusion: In this study, we observed that fosfomycin has a good in-vitro effect on most of the carbapenem resistant Enterobacterales and MRSA isolates tested.
Key words: Fosfomycin; susceptibility testing; antibiotic resistance; MRSA; carbapenem resistant Enterobacterales; MIC
Short running title: In vitro fosfomycin susceptibility