**Section 2**

**Epidemiology Molecular of Methicillin-Resistant** *Staphylococcus aureus* **(MRSA) Isolated from Humans and Animals** 

50 Epidemiology Insights

Zaba, R. & Danczak-Pazdrowska, A. (2001). Analysis of mycoses in children – patients of

(June), pp. 106-109, ISSN 1232-986X

City Hospital in Poznan in the years 1996-2000. *Mikologia Lekarska*, Vol. 8, No. 2

**4** 

*Brazil* 

**CA-MRSA: Epidemiology of a Pathogen of a Great Concern** 

*Biosciency Institute, Botucatu-SP* 

Mariana Fávero Bonesso, Adilson de Oliveira and Maria de Lourdes Ribeiro de Souza da Cunha

*UNESP- Univ. Estadual Paulista, Department of Microbiology and Immunology* 

The emergence of community-acquired methicillin resistant *Staphylococcus aureus* (CA-MRSA) strains in individuals without traditional risk factors, has caused a drastic change in MRSA epidemiology since community acquired infections are etiologically caused by MSSA (methicillin sensitive *S. aureus*). Initially the most affected social groups were soldiers, men who have sex with men, prisoners, illicit injection drug users, and athletes; people with compromised skin and mucosa, poor hygiene habits and postpartum mastitis; Native Americans of the United States, and children due to their close contact with

This change in epidemiology lead to molecular studies aimed at determining pathogenicity, virulence, resistance to different antimicrobial classes and the behavior of these strains against selective pressure of the human immunological system. Associating risk factors with

Humans are the main source of *Staphylococcus* spp., which can be found in the skin, throat, intestine and nose without causing damage to the host. In hospitals, the asymptomatic host can disseminate *S. aureus* to immunocompromised patients. Since they are ubiquitous, these bacteria can cause several types of infections such as: necrotizing pneumonia, skin and soft tissue infections, bacteremia, as well as food poisoning through enterotoxin production.

Individuals affected by CA-MRSA strains can develop from mild to metastatic and lethal infections, which are directly related to the synthesis of certain toxins, antimicrobial resistance and individual health conditions. One of the most discussed virulence factors is PVL (Panton-Valentine Leukocidine). Since its first association with skin and soft tissue infections, PVL is now believed to contribute to the elevated virulence potential attributed to

Methicillin resistance is conferred by *mecA* gene inserted in a mobile genomic island, the Staphylococcal cassette chromosomal (SCC*mec*). Some different SCC*mec* regions are responsible for mobility and regulation, and others for resistance to several antimicrobial classes. According to the presence, lack or genomic variations in these regions, the cassettes

**1. Introduction**

CA-MRSA.

contaminated nasal secretions.

the molecular studies gave rise to Molecular Epidemiology.
