Genetic diversity of Staphylococcus aureus strains from a tertiary care hospital in Rawalpindi, Pakistan

Authors: SYED, MUHAMMAD - University Of Haripur; JAMIL, BUSHRA - Bj Micro Lab; RAMADAN, HAZEM - Mansoura University; RUKAN, MARIA - University Of Haripur; ALI, SHEHZAD - Abdul Wali Khan University; ABASSI, SHAHID - Bj Micro Lab; Woodley, Tiffanie; Jackson, Charlene

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2021
Publication Date: 11/5/2021
Citation: Syed, M.A., Jamil, B., Ramadan, H., Rukan, M., Ali, S., Abassi, S.A., Woodley, T.A., Jackson, C.R. 2021. Genetic diversity of Staphylococcus aureus strains from a tertiary care hospital in Rawalpindi, Pakistan. Microorganisms. https://doi.org/10.3390/microorganisms9112301.
DOI: https://doi.org/10.3390/microorganisms9112301

Interpretive Summary: Staphylococcus aureus has been implicated in a number of diseases in humans ranging from minor skin infections and food poisoning to more serious infections such as pneumonia. Treatment of S. aureus infections has become more complicated due to the emergence of resistant bacteria such as Methicillin-Resistant Staphylococcus aureus (MRSA). As a result, antibiotic resistant S. aureus has been listed by the Centers for Disease Control and Prevention as a serious threat to public health. To gather data on global circulation of resistant S. aureus, clinical S. aureus isolates from Pakistan were tested for resistance to antibiotics and analyzed using molecular methods. Most of the S. aureus isolated were MRSA and also multidrug resistant to drugs commonly used to treat S. aureus infections. MRSA were genetically diverse using molecular typing tests. Regional and global circulating clones implicated in clinical infections were found including the Bengal Bay clone and clones from the U.S., China, and Argentina. Results from this study are important for molecular epidemiologists to monitor evolution and circulation of resistant bacterial clones and for development of effective infection control measures.

Technical Abstract: Staphylococcus aureus is an important healthcare-associated bacterium that causes a multitude of infections in humans such as superficial skin and soft tissue infections, necrotizing pneumonia, foodborne illnesses and postsurgical infections. Treatment of S. aureus infections has become more complicated due to the emergence of Methicillin-Resistant Staphylococcus aureus (MRSA), some of which are multidrug resistant. The present study aimed to characterize S. aureus isolates from a tertiary care hospital in the Rawalpindi district of Pakistan. Staphylococci were isolated from 300 clinical samples collected from January 2018 to January 2019 and S. aureus isolates were tested for antimicrobial susceptibility and analyzed using Pulsed-Field Gel Electrophoresis (PFGE), Multi-Locus Sequence Typing (MLST), staphylococcal cassette chromosome mec (SCCmec) and spa typing. Approximately 25.3% (76/300) of the clinical samples were positive for S. aureus; of those, 88.2% (67/76) were mecA+ (MRSA). In addition to the '-lactam antibiotics, high levels of resistance were also found to the fluoroquinolones [ciprofloxacin, gatifloxacin, and levofloxacin (73.7% each)]. Of the 23 different spa types identified, the majority of isolates belonged to spa type t632 and t657 (9/66; 13.6% each spa type). ST772-t657 (Bengal Bay clone) was the most commonly identified clone in this study although other clones circulating around different regions of the world were also found indicating the diversity in MRSA isolates from this area of Pakistan. This study emphasizes the need to monitor MRSA in the clinical setting for improved infection control and treatment options.