en ميکروب شناسي Microbiology Research Article Research Article <div style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Times New Roman;"><b>Background:</b> The emergence of multidrug-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 <i>Staphylococcus aureus</i> (MRSA) bloodstream isolates by agar dilution, disk diffusion, and screen agar.<br> <b>Methods:</b> In this study, 141 consecutive blood isolates resistant to carbapenem and 62 MRSA blood culture isolates were collected over a period of 8 months. The methods used were fosfomycin agar dilution (0.25 &micro;g/ml to 512 &micro;g/ml), Kirby-Bauer disk diffusion (150 &micro;g of fosfomycin + 50 &micro;g of glucose-6-phosphate), and fosfomycin screen agar (32 &micro;g/ml, 48 &micro;g/ml, and 64 &micro;g/ml). All three methods were interpreted using the European Committee on Antimicrobial Susceptibility Testing guidelines. The agreement between the new method and the reference method was calculated.<br> <b>Results:</b> Among the tested isolates, 100% of MRSA, followed by <i>Escherichia coli </i>(<i>E. coli</i>) (86.4%), <i>Klebsiella pneumonia </i>(<i><span lang="EN-IN">K. pneumonia</span></i><span lang="EN-IN">)</span> (65.2%), and <i>E. cloacae</i> (50%) were susceptible to fosfomycin. The MIC50 and MIC90 of fosfomycin were 0.5 &micro;g/ml and 2 &micro;g/ml for MRSA, 16 &micro;g/ml and 32 &micro;g/ml for <i>K. pneumoniae</i>, 4 &micro;g/ml and 16 &micro;g/ml for <i>E. coli</i>, and 8 &micro;g/ml and 32 &micro;g/ml for <i>E. cloacae</i>, respectively.<br> <b>Conclusion</b>: Fosfomycin demonstrated a good <i>in-vitro</i> effect on most of the carbapenem-resistant Enterobacterales and MRSA isolates tested.</span></span></div> <div style="text-align: justify;"><br> <span style="font-size:11pt"><span style="text-justify:inter-ideograph"><span style="line-height:107%"><span style="font-family:Calibri"><b><span style="font-size:14.0000pt"><span style="font-family:'Times New Roman'"><span style="font-weight:bold"></span></span></span></b></span></span></span></span></div> Fosfomycin, Drug Resistance, Microbial, Methicillin-Resistant Staphylococcus aureus, Susceptibility testing, Carbapenem resistant Enterobacterales 5 8 http://mlj.goums.ac.ir/browse.php?a_code=A-10-1432-1&slc_lang=en&sid=1 Apurba Sankar Sastry drapurbasastry@gmail.com 100319475328460031257 100319475328460031257 Yes Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India Shuruthi Kirubakaran shuruthi99k@gmail.com 100319475328460031258 0009-0006-2416-8985 No Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India Sarumathi Dhandapani saimaruthi331993@gmail.com 100319475328460031259 100319475328460031259 No Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India Ketan Priyadarshi ketprirule@gmail.com 100319475328460031260 100319475328460031260 No Medical College and Medical Research Public Institute located in Phulwari Sharif, Patna, Bihar, India