Prevalence of USA300 Methicillin-resistant Staphylococcus aureus at the Hershey Medical Center and the Development of a Novel Multiplex-PCR Method to Detect USA300 MRSA

Open Access
Bjanes, Elisabet Laura
Area of Honors:
Immunology and Infectious Disease
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Stephen John Knabel, Thesis Supervisor
  • Pamela Hankey, Honors Advisor
  • Antibiotic resistance
  • molecular evolution of MRSA
  • epidemiology of infectious disease
  • USA300 MRSA
  • novel multiplex-PCR
The emergence and rapid spread of methicillin-resistant S. aureus (MRSA) epidemic clone USA300 has doubled the incidence of MRSA and S. aureus disease burden since the early 2000’s. Although USA300 originated as a community-associated MRSA clone (CA-MRSA), it has been increasingly isolated from hospital-associated settings. Since hospital-associated and community-associated clones of MRSA have different resistance and infection profiles, antibiotics that work on HA-MRSA clones are often ineffective on CA-MRSA clones and vice versa. Analysis of clinical MRSA isolates from the Penn State Milton S. Hershey Medical Center (HMC) showed a dramatic increase in USA300 prevalence compared to previous analysis of MRSA isolates from the nasal passages of patients upon admission to HMC. A reliable method that differentiates between USA300 and other HA-MRSA clones may allow screening, tracking and control of USA300 in time to affect patient outcomes and potentially halt the spread between patients and staff. Use of multiplex-PCR methods as diagnostic aids would also significantly reduce the time spent administering ineffective antibiotics and potentially increase the possibility of positive outcomes. A novel multiplex-PCR method was developed to target five genes unique to MRSA and USA300, mecA (methicillin resistance), nuc (S. aureus nuclease), lukPV (Panton-Valentine leukocidin), ACME (arginine catabolic mobile element), and SCCmecIVa (staphylococcal chromosomal cassette IVa). The electrophoretic pattern produced by the multiplex-PCR method can also differentiate several of the major epidemic clones of MRSA including USA100, USA400, and USA700. Known epidemic clone MRSA isolates previously analyzed using multi-virulence-locus sequence typing (MVLST) were used to validate this novel multiplex-PCR method.