Staphylococcus Aureus and Methicillin-Resistant Staphylococcus Aureus Nucleic Acid

Staphylococcus aureus is one of the important pathogenic bacteria of nosocomial infection. Staphylococcus aureus (SA) belongs to the staphylococcus and is a representative of Gram-positive bacteria, which can produce a variety of toxins and invasive enzymes. The bacteria have the characteristics of wide distribution, strong pathogenicity and high resistance rate. Thermostable nuclease gene (nuc) is a highly conserved gene of staphylococcus aureus. In recent years, due to the extensive use of hormones and immune preparations and the abuse of broad-spectrum antibiotics, nosocomial infections caused by Methicillin-resistant Staphylococcus aureus (MRSA) in Staphylococcus have been on the rise. The national average detection rate of MRSA was 30.2% in 2019 in China. MRSA is divided into healthcare-associated MRSA (HA-MRSA), community-associated MRSA (CA-MRSA), and livestock-associated MRSA (LA-MRSA). CA-MRSA, HA-MRSA, LA-MRSA have great differences in microbiology, bacterial resistance (eg, HA-MRSA shows more multidrug resistance than CA-MRSA) and clinical characteristics (eg infection site). According to these characteristics, CA-MRSA and HA-MRSA can be distinguished. However, the differences between CA-MRSA and HA-MRSA are narrowing due to the constant movement of people between hospitals and communities. MRSA is multi-drug resistant, not only resistant to β-lactam antibiotics, but also to aminoglycosides, macrolides, tetracyclines and quinolones to varying degrees. There are large regional differences in drug resistance rates and different trends.

Methicillin resistance mecA gene plays a decisive role in staphylococcal resistance. The gene is carried on a unique mobile genetic element (SCCmec), which encodes penicillin-binding protein 2a (PBP2a) and it has low affinity to β-lactam antibiotics, so that antimicrobial drugs can not hinder the synthesis of cell wall peptidoglycan layer, resulting in drug resistance.