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Updated: May 2, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 10, 2011
Secreted virulence factor comparison between methicillin-resistant and methicillin-sensitive Staphylococcus aureus,
Patrick M Schlievert1, Kristi L Strandberg, Ying-Chi Lin
1Department of Microbiology, University of Minnesota Medical School, 420 Delaware Street SE, Minneapolis, MN 55455, USA. schli001@umn.edu
Abstract:
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains have emerged as serious health threats in the last 15 years. They are associated with large numbers of atopic dermatitis skin and soft tissue infections, but when they originate from skin and mucous membranes, have the capacity to produce sepsis and highly fatal pulmonary infections characterized as necrotizing pneumonia, purpura fulminans, and postviral toxic shock syndrome. This review is a discussion of the emergence of 3 major CA-MRSA organisms, designated CA-MRSA USA400, followed by USA300, and most recently USA200. CA-MRSA USA300 and USA400 isolates and their methicillin-sensitive counterparts (community-associated methicillin-sensitive S aureus) typically produce highly inflammatory cytolysins alpha-toxin, gamma-toxin, delta-toxin (as representative of the phenol soluble modulin family of cytolysins), and Panton Valentine leukocidin. USA300 isolates produce the superantigens enterotoxin-like Q and a highly pyrogenic deletion variant of toxic shock syndrome toxin 1 (TSST-1), whereas USA400 isolates produce the superantigens staphylococcal enterotoxin B or staphylococcal enterotoxin C. USA200 CA-MRSA isolates produce small amounts of cytolysins but produce high levels of TSST-1. In contrast, their methicillin-sensitive S aureus counterparts produce various cytolysins, apparently in part dependent on the niche occupied in the host and levels of TSST-1 expressed. Significant differences seen in production of secreted virulence factors by CA-MRSA versus hospital-associated methicillin-resistant S aureus and community-associated methicillin-sensitive S aureus strains appear to be a result of the need to specialize as the result of energy drains from both virulence factor production and methicillin resistance.
Insights
Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains cause severe skin, soft tissue, and fatal pulmonary infections. This review details the emergence and virulence factors of key CA-MRSA strains like USA300 and USA400.
Area of Science:
- Microbiology
- Infectious Diseases
- Public Health
Background:
- Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a significant global health concern over the past 15 years.
- CA-MRSA strains are frequently implicated in skin and soft tissue infections, particularly atopic dermatitis, and can lead to severe systemic illnesses such as sepsis and fatal necrotizing pneumonia.
- The review focuses on three prominent CA-MRSA lineages: USA400, USA300, and USA200.
Purpose of the Study:
- To review the emergence and characteristics of major CA-MRSA strains.
- To compare the virulence factor production, including cytolysins and superantigens, among different CA-MRSA strains and their methicillin-sensitive counterparts.
- To explore the potential reasons for the specialized virulence factor profiles observed in CA-MRSA.
Main Methods:
- Literature review and synthesis of existing research on CA-MRSA.
- Comparative analysis of secreted virulence factors (cytolysins and superantigens) produced by different Staphylococcus aureus strains (CA-MRSA, hospital-associated MRSA, community-associated MSSA).
- Discussion of the genetic and metabolic factors influencing virulence factor expression.
Main Results:
- CA-MRSA USA300 and USA400 strains, along with their methicillin-sensitive counterparts, characteristically produce alpha-toxin, gamma-toxin, delta-toxin, and Panton Valentine leukocidin.
- USA300 isolates are noted for producing enterotoxin-like Q and a variant of toxic shock syndrome toxin 1 (TSST-1), while USA400 isolates produce staphylococcal enterotoxin B or C.
- USA200 CA-MRSA strains produce lower levels of cytolysins but high levels of TSST-1, contrasting with their methicillin-sensitive counterparts.
- Methicillin-sensitive Staphylococcus aureus strains exhibit variable cytolysin production influenced by host niche and TSST-1 expression.
Conclusions:
- Significant variations in secreted virulence factors exist between CA-MRSA, hospital-associated MRSA, and community-associated methicillin-sensitive S aureus strains.
- These differences likely reflect specialized adaptations driven by the energetic costs of virulence factor production and methicillin resistance.
- Understanding these specialized virulence profiles is crucial for developing targeted therapeutic and preventative strategies against CA-MRSA infections.
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