Main article: Methicillin-resistant Staphylococcus aureus FROM en.wikipedia.org...
Staphylococcus aureus (colloquially known as "Staph aureus" or a "Staph infection") is one of the major resistant pathogens. Found on the mucous
membranes and the human skin of around a third of the population, it is extremely adaptable to antibiotic pressure. It was one of the earlier bacteria
in which penicillin resistance was found—in 1947, just four years after the drug started being mass-produced. Methicillin was then the antibiotic of
choice, but has since been replaced by oxacillin due to significant kidney toxicity. Methicillin-resistant Staphylococcus aureus (MRSA) was first
detected in Britain in 1961, and is now "quite common" in hospitals. MRSA was responsible for 37% of fatal cases of sepsis in the UK in 1999, up
from 4% in 1991. Half of all S. aureus infections in the US are resistant to penicillin, methicillin, tetracycline and erythromycin.
This left vancomycin as the only effective agent available at the time. However, strains with intermediate (4-8 μg/ml) levels of resistance, termed
glycopeptide-intermediate Staphylococcus aureus (GISA) or vancomycin-intermediate Staphylococcus aureus (VISA), began appearing in the late 1990s. The
first identified case was in Japan in 1996, and strains have since been found in hospitals in England, France and the US. The first documented strain
with complete (>16 μg/ml) resistance to vancomycin, termed vancomycin-resistant Staphylococcus aureus (VRSA) appeared in the United States in
2002. However, in 2011 a variant of vancomycin has been tested that binds to the lactate variation and also binds well to the original target,
thus reinstates potent antimicrobial activity.
A new class of antibiotics, oxazolidinones, became available in the 1990s, and the first commercially available oxazolidinone, linezolid, is
comparable to vancomycin in effectiveness against MRSA. Linezolid-resistance in S. aureus was reported in 2003.
Community-acquired MRSA (CA-MRSA) has now emerged as an epidemic that is responsible for rapidly progressive, fatal diseases, including necrotizing
pneumonia, severe sepsis and necrotizing fasciitis. MRSA is the most frequently identified antimicrobial drug-resistant pathogen in US hospitals.
The epidemiology of infections caused by MRSA is rapidly changing. In the past 10 years[when?], infections caused by this organism have emerged in the
community. The two MRSA clones in the United States most closely associated with community outbreaks, USA400 (MW2 strain, ST1 lineage) and USA300,
often contain Panton-Valentine leukocidin (PVL) genes and, more frequently, have been associated with skin and soft tissue infections. Outbreaks of
CA-MRSA infections have been reported in correctional facilities, among athletic teams, among military recruits, in newborn nurseries, and among men
who have sex with men. CA-MRSA infections now appear endemic in many urban regions and cause most CA-S. aureus infections.
Streptococcus and Enterococcus
Streptococcus pyogenes (Group A Streptococcus: GAS) infections can usually be treated with many different antibiotics. Early treatment may reduce the
risk of death from invasive group A streptococcal disease. However, even the best medical care does not prevent death in every case. For those with
very severe illness, supportive care in an intensive care unit may be needed. For persons with necrotizing fasciitis, surgery often is needed to
remove damaged tissue. Strains of S. pyogenes resistant to macrolide antibiotics have emerged; however, all strains remain uniformly sensitive to
Resistance of Streptococcus pneumoniae to penicillin and other beta-lactams is increasing worldwide. The major mechanism of resistance involves the
introduction of mutations in genes encoding penicillin-binding proteins. Selective pressure is thought to play an important role, and use of
beta-lactam antibiotics has been implicated as a risk factor for infection and colonization. S. pneumoniae is responsible for pneumonia, bacteremia,
otitis media, meningitis, sinusitis, peritonitis and arthritis.
Multidrug-resistant Enterococcus faecalis and Enterococcus faecium are associated with nosocomial infections. Among these strains,
penicillin-resistant Enterococcus was seen in 1983, vancomycin-resistant Enterococcus in 1987, and linezolid-resistant Enterococcus in the late
Pseudomonas aeruginosa is a highly prevalent opportunistic pathogen. One of the most worrisome characteristics of P. aeruginosa is its low antibiotic
susceptibility. END QUOTE
Those who say where is the proof of evolution need look no farther than the end of a microscope.