Gene Reports 24 (2021) 101179 2452-0144/© 2021 Elsevier Inc. All rights reserved. Plausible challenges of methicillin and clindamycin resistance detection in Staphylococcus aureus Nasim Asadi Faezi a, b , Alka Hasani a, b, c, * , Elghar Soltani b, c , Vahideh Valizadeh d , Akbar Hasani e , Aytak Khabbaz c , Mohammad Ahangarzadeh Rezaee b , Mojtaba Varschochi a a Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran b Department of Bacteriology and Virology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran c Clinical Research Development Unit, Sina Educational, Research and Treatment Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, I.R., Iran d Department of Nano-Biotechnology, New Technologies Research Group, Pasteur Institute of Iran, Tehran, Iran e Department of Clinical Biochemistry and Laboratory Sciences, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, I.R.. Iran A R T I C L E INFO Keywords: Methicillin resistance Inducible clindamycin resistance Constitutive clindamycin resistance D-test Multiplex PCR ABSTRACT Accurate detection and therapeutic challenges are still on the debate for methicillin-resistant Staphylococcus aureus (MRSA). Working on clindamycin, researchers serendipitously spotted the D test and the era of macrolide- lincosamide (ML) resistance commenced. We aimed to i) assess usage of other antibiotics other than cefoxitin for the detection of MRSA, ii) evaluate various surrogate therapeutic options, and iii) determine phenotypic and genotypic aspects of inducible and constitutive clindamycin resistance in S. aureus. Disk diffusion agar assay and molecular method were used to assess MRSA detection. Effcacy of linezolid, vancomycin, mupirocin, teico- planin, fusidic acid, and rifampin was analyzed by E-test. Various phenotypes of macrolide-lincosamide- streptogramin B (MLS B ) resistance were detected by performing D-test followed by PCR assay for ermA, ermB and ermC genes coding for macrolide resistance. The cefoxitin disc yielded the best sensitivity value (100%) over oxacillin, imipenem, and meropenem. All isolates were completely sensitive to linezolid and teicoplanin. Among MRSA isolates, 6.2%, 1.5%, and 17.1% strains had intermediate and complete resistance to vancomycin, fusidic acid, and rifampin respectively. Fifty-six isolates were clindamycin susceptible and diverse resistance outlooks were the major outcome of our study with 20.6% isolates demonstrated two distinct induction phenotypes (D and D+) and 45% isolates showed non-induction (HD,R) phenotypes. ermA gene alone and in combination with ermC was found to be more prevalent among inducible as well as constitutive clindamycin- resistant isolates. 1. Introduction Staphylococcus aureus is legendary notorious for community-acquired infections however, the emergence of drug-resistant ‘hospital strains’ particularly, methicillin-resistant S. aureus (MRSA) led to the appear- ance of fatal outbreaks and perplexed the situation leaving little thera- peutic options (Hiramatsu et al., 1997). S. aureus clinical infections are treated with glycopeptides however, the emergence of sporadic com- plete or intermediate resistance to this class of antibiotic has lead to considerable challenge (Phillips et al., 2016). Though Quinopristin/ dalfopristin (Synercid) and linezolid have been proposed as surrogate markers (Hu et al., 2013) however, many physicians still prefer to use old antibiotics like macrolide, lincosamides, and streptogramins, the degree of resistance of which is ought to be assessed. Resistance towards these antibiotics is the result of target site modifcation mechanisms, which is also called macrolide-lincosamide-streptogramin B (MLS B ) resistance. The most common mechanism for such resistance is target site modifcation mediated by erm genes: ermA, ermB, and ermC, and the effux mediated phenomenon conducted by msr gene (Khan et al., 1999). This erm mediated resistance can be expressed either constitutively Abbreviations: MRSA, methicillin-resistant Staphylococcus aureus; MSSA, methicillin-susceptible Staphylococcus aureus; ML, macrolide-lincosamide; MLS B , mac- rolide-lincosamide-streptogramin B; PBP, penicillin-binding protein; iMLSB, Inducible MLSB; cMLSB, Constitutive MLSB; QC, Quality control; CLSI, Clinical and Laboratory Standards Institute; MIC, Minimum Inhibitory Concentration; MDR, Multi-drug Resistance. * Corresponding author at: Infectious and Tropical Diseases Research Center, Clinical Research Development Unit, Sina Educational, Research and Treatment Center; and Department of Bacteriology and Virology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, I.R., Iran. E-mail address: hasanialka@tbzmed.ac.ir (A. Hasani). Contents lists available at ScienceDirect Gene Reports journal homepage: www.elsevier.com/locate/genrep https://doi.org/10.1016/j.genrep.2021.101179 Received 16 March 2021; Received in revised form 11 April 2021; Accepted 27 April 2021