Prevalent Clones of Methicillin Resistant Staphylococcus Aureus Strains in Pakistan by Various Typing Techniques

Staphylococcus aureus (S.aureus) is an important pathogen that causes infections in both hospital and community settings. The resistant to methicillin in S. aureus emerged in 1960s and since then the prevalence of Methicillin resistant S.aureus (MRSA) has been increasing globally. The increasing incidence of MRSA infections demands a quick and reliable characterization of isolates and investigation of the clonal spread of clones in hospitals as well as in the community to generate information that helps health care professionals to implement appropriate measures to control these infections. To investigate the MRSA outbreaks, evaluation of transmission of MRSA strains and their evolution, bacterial typing techniques are important tools. The continuous surveillance and monitoring of the presence of MRSA in community and hospital settings is important to make a clear understanding of the dynamics of the spread of MRSA to assist in controlling its dissemination. In this review the various typing techniques that have been used to type MRSA isolates from Pakistan have been discussed. This review also focuses on the various clones of MRSA that are reported in Pakistani community as well as in hospitalized patients. *Corresponding author: Naila Altaf, Department of microbiology Quaid-i-Azam university, Islamabad Phone: 0332-5481129. E-mail: . [email protected] Review Article R-2 Prevalent Clonal Types of MRSA Circulating in Pakistan Annals of Pathology and Laboratory Medicine, Vol. 02, No. 02, April June 2015 Introduction Staphylococcus aureus (S. aureus) is the cause of infections, both in hospitals and community settings. With the passage of time it is exhibiting more virulence and acquiring resistance to antibiotics like methicillin and vancomycin. New strains of S. aureus with different virulence and antibiotic resistance profiles are emerging. Knowledge about the difference in S. aureus genome and factors that control these differences can better help us to control infections caused by S. aureus. [1] The difference in S. aureus genome can be recognized by using a reliable typing method which can also help us in introducing better treatment strategies. S. aureus infections are difficult to treat due to their acquisition of different antibiotic resistant determinants. In 1942 penicillin resistant S. aureus was recognized in both hospital and community. In 1961 methicillin was introduced, but soon S. aureus strains became resistant to methicillin by producing altered penicillin binding protein. [2] MRSA was once limited to hospitals called as hospital acquired MRSA but in mid 1990s a second type of MRSA known as community acquired MRSA (CA-MRSA) was isolated, that has greatly changed the epidemiology of MRSA.[3][4]According to Center for disease control and prevention (CDC), MRSA infections diagnosed in an outpatient setting or within 48 hours of admission to hospital with no history of infection, any medical devices or indwelling catheters will be categorized as CA-MRSA infection. MRSA infection in persons, who have recent contact with a hospital or health care facilities, has undergone an invasive procedure within a previous year or are immunocompromised, should be taken as hospital acquired MRSA infections. The increasing prevalence of MRSA around the world is becoming a serious problem for clinicians and a threat to public health. Studies have reported that the prevalence of MRSA in USA has increased from 6% in 1998 to 50% in the year 2002.The data from Europe and Asia also show increased prevalence of MRSA infections.[5] The same is the case with CAMRSA. In various countries 50% of outpatient Staphylococcal infections are caused by CAMRSA.[6] The prevalence of MRSA in Pakistan is found to be 42% by Hafiz et al. (2002). Clinicians and epidemiologists can discriminate S. aureus isolates by using various typing techniques. The typing systems are usually used for the investigation of outbreaks of nosocomial infection, can aid in clinical treatment of a patient, allowing for discrimination between recurrent and successive infections and in broader context can contribute to the understanding of the epidemiology of infections.[8] The aim of this review is to report all the clonal types of MRSA circulating in Pakistani community and hospitalized patients reported by using various typing techniques. This review describes the epidemiology of various clones of MRSA in Pakistan in order to have an understanding of various clonal types common in this region. Phage Typing The concept of using bacteriophages for the typing of Staphylococci was first developed in the 1940s.[11] Phage typing was the method of choice for characterizing the MRSA outbreak strains in the past.[12]The strains are classified according to the susceptibility to the set of selected phages. An internationally accepted set of 23 phages is used for the typing of human strains of S. aureus. The discriminatory power of Phage typing is greater than capsular typing and zymotyping. [11] Phage typing has been reported to be valuable in the identification of known epidemic strains among endemic strains and is preferred as a first line approach in epidemiological investigation of MRSA strains.[13] Some of the disadvantages of Phage typing includes that it is time consuming, technically demanding and lack reproducibility. Phage typing has been confined to the larger laboratories because it can be done more efficiently on large batches. In phage typing high proportion of MRSA isolates remains non-typeable.[11]The biologically active phages are maintained and available only at the reference laboratories.[13] Phage Typing of S. aureus Isolates From