MRSA ST398

MRSA ST398

Methicillin-resistant *Staphylococcus aureus* (MRSA) ST398 is a strain of the bacterium *Staphylococcus aureus* that is resistant to methicillin and other beta-lactam antibiotics. This particular strain, known as sequence type 398 (ST398), is notable for its association with livestock, particularly pigs, and has been referred to as "livestock-associated MRSA" (LA-MRSA).

History and Emergence

MRSA ST398 was first identified in the early 2000s in the Netherlands and has since been detected in various countries around the world. It emerged as a significant public health concern due to its ability to colonize and infect humans who are in close contact with livestock, especially pigs. The strain was initially discovered in pig farmers and their families, highlighting the zoonotic potential of MRSA ST398.

Genetic Characteristics

MRSA ST398 belongs to the clonal complex 398 (CC398) and is characterized by the absence of the *SCCmec* type IV element, which is commonly found in community-associated MRSA strains. Instead, it often carries the *SCCmec* type V or other types. The strain is also known for its lack of the Panton-Valentine leukocidin (PVL) toxin, which is associated with virulence in other MRSA strains.

Epidemiology

MRSA ST398 is primarily associated with livestock, particularly pigs, but it has also been found in other animals such as cattle, poultry, and horses. Human infections are typically linked to direct contact with these animals or their environments. The strain has been reported in Europe, North America, and Asia, with varying prevalence rates depending on the region and the density of livestock farming.

Transmission

Transmission of MRSA ST398 occurs through direct contact with colonized or infected animals, as well as through contaminated environments. Human-to-human transmission is less common but can occur, particularly in healthcare settings or among individuals with close contact with colonized persons.

Clinical Manifestations

In humans, MRSA ST398 can cause a range of infections, from mild skin and soft tissue infections to more severe conditions such as pneumonia and bloodstream infections. However, it is often less virulent than other MRSA strains, partly due to the absence of certain virulence factors like PVL.

Diagnosis

Diagnosis of MRSA ST398 involves microbiological culture and susceptibility testing to confirm methicillin resistance. Molecular typing methods, such as multilocus sequence typing (MLST), are used to identify the specific sequence type 398.

Treatment

Treatment of MRSA ST398 infections involves the use of antibiotics to which the strain is susceptible. Common options include vancomycin, linezolid, and daptomycin. The choice of antibiotic depends on the severity of the infection and the susceptibility profile of the isolate.

Prevention and Control

Preventive measures focus on reducing the risk of transmission from animals to humans. This includes implementing good hygiene practices in livestock farming, using personal protective equipment, and conducting regular screening of animals and workers. In healthcare settings, standard infection control measures are essential to prevent the spread of MRSA ST398.

Also see

• Methicillin-resistant Staphylococcus aureus
• Livestock-associated MRSA
• Antibiotic resistance
• Zoonotic diseases