What is the Difference Between HA-MRSA and CA-MRSA

The main difference between HA-MRSA and CA-MRSA is that HA-MRSA is the type of MRSA infection that occurs during a stay in or immediately after the discharge from a hospital whereas CA-MRSA is the type of MRSA infection that is community-acquired, spreading in families or other groups with no any prior of healthcare exposure. Furthermore, HA-MRSA predominantly causes skin and soft tissue infections while CA-MRSA causes deep-scaled or systemic infections. In addition, HA-MRSA is often resistant to non-β-lactam antimicrobial agents including aminoglycosides, macrolides, lincosamides, and fluoroquinolones while CA-MRSA is susceptible to non-β-lactam antimicrobials.  

HA-MRSA and CA-MRSA are two strains of MRSA (methicillin-resistant Staphylococcus aureus). Generally, these strains differ only by a small number of genes, which permit them to survive in different environments. 

Key Areas Covered 

1. What is HA-MRSA
     – Definition, Characteristics of Infection
2. What is CA-MRSA
     – Definition, Characteristics of Infection
3. What are the Similarities Between HA-MRSA and CA-MRSA
     – Outline of Common Features
4. What is the Difference Between HA-MRSA and CA-MRSA
     – Comparison of Key Differences

Key Terms 

β-Lactam Antimicrobial Drugs, CA-MRSA, HA-MRSA, Infections, Methicillin, MRSA

Difference Between HA-MRSA and CA-MRSA - Comparison Summary

What is HA-MRSA 

HA-MRSA (healthcare-associated MRSA) is a type of methicillin-resistant strains of Staphylococcus aureus (MRSA), significantly causing nosocomial infections. Generally, it largely affects older adults as well as immunosuppressed people. In other words, those who have undergone surgical procedures are at higher risk for the HA-MRSA infection. Furthermore, HA-MRSA causes respiratory, urinary, and systemic infections.

Main Difference - HA-MRSA vs CA-MRSA

Figure 1: MRSA Skin Infection

Moreover, HA-MRSA contains large (34-67 kb) SCCmec types: type I, II, or III. Significantly, it is resistant to methicillin as well as other β-lactam antimicrobial drugs. Meanwhile, HA-MRSA is multi-drug resistant. Basically, this is due to the presence of SCCmec type II or II, which permits the inclusion of other non-beta-lactam resistance genes. 

What is CA-MRSA 

CA-MRSA (community-acquired MRSA) is another type of MRSA. However, it evolved as an endemic form of MRSA. The main feature of CA-MRSA is that it infects healthy individuals in the community without established risk factors of MRSA. Besides, it infects the skin and soft tissues, including abscesses, cellulitis, folliculitis, and impetigo and a serious form of pneumonia.

Difference Between HA-MRSA and CA-MRSA

Figure 2: MRSA Selective Media Plate

Moreover, CA-MRSA contains smaller SCCmec variants, predominantly SCCmec type IV (24 kb). However, as larger SCCmec types, SCCmec type IV does not permit the inclusion of other non-beta lactam resistance genes. Therefore, CA-MRSA is susceptible to non-beta lactam antibiotics such as trimethoprim/sulfamethoxazole (SXT) and clindamycin. On the other hand, SCCmec type IV is always associated with PVL (Panton-Valentine leukocidin) genes, which codes for the production of a cytotoxin, causing tissue necrosis and leukocyte destruction. Therefore, PVL genes play a key role in the determination of the clinical spectrum of the CA-MRSA infection. 

Similarities Between HA-MRSA and CA-MRSA 

  • HA-MRSA and CA-MRSA are two strains of MRSA, first identified in the 1960s. 
  • Traditionally, MRSA was considered a major nosocomial pathogen in healthcare facilities, but in the past decade, it has been observed emerging in the community as well.   
  • Moreover, MRSA occurs without identified risk factors, and it is resistant to methicillin as well as other β-lactam antimicrobial drugs.  
  • Both strains of MRSA cause mild to severe infections worldwide. 
  • They infect both healthy adults and immunosuppressed individuals. 
  • They show increased morbidity and mortality in patients due to the cumbersome treatment required. 
  • Both strains can be distinguished by drug resistance patterns and molecular characteristics. 

Difference Between HA-MRSA and CA-MRSA 


HA-MRSA refers to the healthcare-associated MRSA, while CA-MRSA refers to the community-associated MRSA. 


HA-MRSA spreads within healthcare settings while CA-MRSA spreads within families and other groups of people out of the healthcare settings. 

Type of Patients 

Moreover, HA-MRSA infects individuals that are elderly, debilitated, and/or critically or clinically ill while CA-MRSA infects young and healthy people such as students, professional athletes, or military service personal. 

Infection Site 

HA-MRSA causes bacteraemia with no obvious infection focus, infecting surgical wounds, open ulcers, catheter urine, IV lines, etc. while CA-MRSA infects skin, soft tissue, producing abscesses or cellulitis.  

Type of Pneumonia 

While HA-MRSA causes ventilator-associated pneumonia, CA-MRSA causes necrotizing community-acquired pneumonia. 

Type of Diseases 

HA-MRSA predominantly causes skin and soft tissue infections while CA-MRSA causes deep-scaled or systemic infections, including septic shock or bone and joint infections. 


While HA-MRSA has a limited community spread, CA-MRSA spreads in the community easily.  


Moreover, HA-MRSA contains type SCCmec type I, II, or III, while CA-MRSA contains type IV or V SCCmec. 

PVL Genes 

PVL genes are absent in HA-MRSA while PVL genes are present in CA-MRSA, including lukS and lukF. 

Antibiotic Susceptibility 

HA-MRSA is multiresistant to antibiotics, while CA-MRSA is susceptible to more antibiotics. 


The five clones of HA-MRSA include USA100, -200, -500, -600, and -800, while the two clones of CA-MRSA include USA300 and USA400. 

Prominent Clone 

The predominant clone of HA-MRSA is USA100, while the predominant clone of CA-MRSA is USA300. 


HA-MRSA is one of the strains of MRSA associated with healthcare settings. Therefore, it infects patients in hospitals and mainly causes skin and soft tissue infections. Moreover, HA-MRSA is resistant to many antibiotics. On the other hand, CA-MRSA is another strain of MRSA. However, it is not associated with healthcare settings. Meanwhile, it spreads in communities out of healthcare settings. They also cause deeply-scaled or systemic infections. Furthermore, CA-MRSA is susceptible to antibiotics. Therefore, the main difference between HA-MRSA and CA-MRSA is the type of infection. 


1. Hsiao, Ching-Hsi, et al. “A Comparison of Clinical Features between Community-Associated and Healthcare-Associated Methicillin-ResistantStaphylococcus AureusKeratitis.” Journal of Ophthalmology, vol. 2015, 2015, pp. 1–7., doi:10.1155/2015/923941.
2. “Healthcare (Hospital)-Associated MRSA (HA-MRSA) versus Community-Associated MRSA (CA-MRSA).” Laboratory Continuing Education, LabCE, Available Here.

Image Courtesy:

1. “Mrsa2” By Jen – Self-photographed (CC BY-SA 3.0) via Commons Wikimedia      
2. “MRSA on a selective choromogenic media plate” By Xishan01 – Own work (CC BY-SA 3.0) via Commons Wikimedia  

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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