Staphylococcus aureus CA-MRSA
A Microbial Biorealm page on the genus Staphylococcus aureus CA-MRSA
Classification
Bacteria; Firmicutes; Cocci, Bacillales; Staphylococcaceae; Staphylococcus; Aureus
Description and significance
Methicillin-resistant Staphylococcus aureus (MRSA) is a super bug that has developed resistance to our strongest antibiotics including penicillin and amoxicillin. It emerged in the 1970’s and now accounts for 50-70% of S. aureus infections, which are the most prevalent of hospital pathogens. The MRSA mortality rate is estimated to be as high as 23 percent of patients, around 2.5 times higher than the methicillin susceptible strain of S. aureus. While MRSA is found most commonly in patients undergoing invasive surgery or in those with weakened immune systems, the type of infection classified as community-acquired MRSA (CA-MRSA) requires no contact with healthcare facilities. Since the spread of MRSA only requires skin to skin contact, it can occur among teams where athletes share equipment and even in childcare facilities where children are in close contact for long periods of time. Numbers indicate that around 50 percent of skin infections entering emergency rooms are caused by MRSA (5).
Vancomycin was originally used to combat the infection, but with new strains emerging an increased resistance has grown. Researchers are attempting to develop new ways to cope with this organism, hopefully with the aid of genome sequencing, so that this untreatable pathogen can be eradicated.
Genome structure
Two MRSA strains, methicillin-resistant N315 and vancomycin-resistant Mu 50, were sequenced in 1982 and 1997 respectively. The strain N315 has 2,839,469 bp, holds a plasmid of 25kb in size, and has a G-C content of 32.8% (7). The complex genes present in S. aureus were acquired through lateral gene transfer. The notorious antibiotic resistance of the MRSA pathogen is carried by plasmids or mobile genetic elements. The mobile genetic elements include a unique resistance island. Three new classes of pathogenicity islands were recognized along with the identification of 70 candidates for new virulence factors (1).
S. aureus is able to infect humans of many backgrounds and cause severe immune reactions due to its super antigens encoded by repeated duplication of genes. Research into these newly recognized genes will hopefully help the process of developing a way to fight back (4).
Cell structure, metabolism & life cycle
Provide a physical and biochemical description of the organism. What kind of organism is it, what does it look like, how is it built, what are its metabolic properties, how can it be identified, what is it's life cycle, &c. In other words, describe the organism from its perspective.
Ecology (including pathogenesis)
Describe its habitat, symbiosis, and contributions to environment. If it is a pathogen, how does this organism cause disease? Human, animal, plant hosts? Describe virulence factors and patient symptoms.
Interesting feature
Describe in detail one particularly interesting aspect of your organism or it's affect on humans or the environment.
