The Evolution of Bacterial Resistance

What types of antibiotic resistance have been identified?

MRSA - Methicillin-Resistant Staphylococcus Aureus

These bacteria have become resistant to methicillin, nafcillin, oxacillin, cloxacillin, dicloxacillin, imipenem, and cephalosporins, which are the usual antibiotics used to treat Staphylococcus aureus infections. As a result, more toxic and expensive antibiotics (eg. vancomycin) must be used instead

VRE - Vancomycin-Resistant Enterococcus

Strains that have developed resistance to many commonly used antibiotics, but more specifically vancomycin, which is usually the last line of defence against these infections.
Enterococci are common bacteria that occur naturally in our bowels, but may become harmful if the body is already weakened from illness (eg. prevalent in hospitals)

PR - Penicillin Resistance

Bacteria resistant to the effect of penicillin
Historically, Streptococcus pneumoniae was uniformly susceptible to penicillin (bacteria responsible for meningitis, pneumonia, otitis media, sinusitis, and bacteremia in adults and children)
This constitutes a serious problem among the elderly, infants, and those with chronic underlying medical conditions or immune systems that are already compromised

Bacteria in Action | Bacterial vs. Viral Infections | Good and Not-So-Good Bacteria
The Evolution of Bacterial Resistance | Bacterial Infection Dictionary