Comparative herbal and conventional antimicrobial susceptibility patterns of methicillin-resistant (MR) and methicillin-susceptible (MS) staphylococci of clinical and environmental origin
Authors:   Division of Epidemiology, ICAR-Indian Veterinary Research Institute, Izatnagar-243 122, India., Singh Bhoj R , Agri Himani , Yadav Akanksha , Jayakumar Varsha , Pawde Bho Abhijit M ,   Centre for Wildlife, ICAR-Indian Veterinary Research Institute, Izatnagar-243 122, India.
Published: September 2024

Staphylococci are the leading cause of bacteraemia (septicemia), infective endocarditis (infection in the heart), osteoarticular infections (joints’ infection), skin and soft tissue infections, pleuropulmonary (lung and respiratory tract infections), nosocomial (hospital borne) infections in human and animals. Specifically, vancomycin, methicillin and multi-drug resistant (MDR) staphylococci lead to millions of deaths every year. However, little is understood about methicillin resistance and MDR in staphylococci strains of coagulase-negative or non-S. aureus staphylococci. The present study targeted the void concerning the relation of methicillin resistance with multiple antimicrobial resistances among different species of staphylococci.In the study staphylococci from clinical (607) and non-clinical (267) sources isolated at ICAR-Indian Veterinary Research Institute, Izatnagar, India, were tested for their methicillin resistance using an alternative test (cefoxitin resistance) and susceptibility of the strains to 39 antimicrobials was conducted as per standard CLSI protocol. The data was analyzed to determine the significance of species of the host of origin and species of staphylococci strains and resistance patterns in Microsoft Excel.Staphylococci strains included in the study belonged to 26 species;S. epidermidis was the most commonly identified species from clinical samples followed by S. aureus, S. intermedius,and S. haemolyticus. From non-clinical samples, too S. epidermidis was the most commonly identified Staphylococcus followed by S. haemolyticus, S. aureus and S. intermedius strains. In the study, S. saprophyticus and S. warneri strains were isolated only from non-clinical and clinical samples, respectively. Occurrence of cefoxitin resistance (or methicillin resistance), and multi-drug resistance (MDR) were slightly higher in clinical staphylococci (62.44%, 55.52%) than in non-clinical staphylococci (62.17%, 51.31%) but more concerning was multiple-herbal drug-resistance (MHDR) detected in 60.30% of non-clinical and 42.17% of the clinical strains. The most effective antibiotic against staphylococci was minocycline followed by imipenem, tigecycline, chloramphenicol, meropenem, piperacillin + tazobactam, nitrofurantoin, gentamicin, doxycycline, clindamycin, amoxicillin + clavulanic acid, linezolid, piperacillin, tetracycline and azithromycin, other 11 recommended antibiotics for staphylococcal infections failed to inhibit >65% of staphylococci. Of the 11 herbal antimicrobials tested, five herbal antimicrobials inhibiting ≥80% of staphylococci-causing infections were carvacrol, thyme oil, ajowan oil, cinnamaldehyde, and cinnamon oil revealing their potential as topical antimicrobials to treat skin infections by staphylococci. The present study revealed that methicillin resistance was rampant among both clinical and non-clinical staphylococci and not limited to S. aureus only but detected among all Staphylococcus species strains except S. capraestrains. However, the occurrence of MR varied among strains of different species. Vancomycin and linezolid, the recommended drugs for treating infections with MRSA had no significant difference in their efficacy concerning MR; however, MDR was significantly more common in MR than MS staphylococci. The study suggested the need to review the panel of antibiotics recommended for the treatment of staphylococcal infections in humans and animals.