Tenericutes (no wall)
Fibrobacteres–Chlorobi/Bacteroidetes (FCB group)
Planctomycetes–Verrucomicrobia/Chlamydiae (PVC group)
We're in the post-antibiotic era
Antibiotic resistance is a form of drug resistance whereby some (or, less commonly, all) sub-populations of a microorganism, usually a bacterial species, are able to survive after exposure to one or more antibiotics; pathogens resistant to multiple antibiotics are considered multidrug resistant (MDR) or, more colloquially, superbugs. Microbes, rather than people, develop resistance to antibiotics.
Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium responsible for several difficult-to-treat infections in humans. It is also called oxacillin-resistant Staphylococcus aureus (ORSA). MRSA is any strain of Staphylococcus aureus that has developed, through the process of natural selection, resistance to beta-lactam antibiotics, which include the penicillins (methicillin, dicloxacillin, nafcillin, oxacillin, etc.) and the cephalosporins. Strains unable to resist these antibiotics are classified as methicillin-sensitive Staphylococcus aureus, or MSSA. The evolution of such resistance does not cause the organism to be more intrinsically virulent than strains of Staphylococcus aureus that have no antibiotic resistance, but resistance does make MRSA infection more difficult to treat with standard types of antibiotics and thus more dangerous.
MRSA is especially troublesome in hospitals, prisons and nursing homes, where patients with open wounds, invasive devices, and weakened immune systems are at greater risk of infection than the general public.
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain (safranin or fuchsine) and appearing red or pink. Gram-positive organisms are able to retain the crystal violet stain because of their thick peptidoglycan layer, which is superficial to the cell membrane. This is in contrast to Gram-negative bacteria, which may have a thick or thin peptidoglycan layer that is located between two cell membranes.
Plasma membrane, PG layer and cell wall are three distinct structures. For example, plant cells have rigid cell walls in addition to an outer plasma membrane, and animal cells have only plasma membranes. Thus, cell walls are responsible for structural support and rigidity that plant cells need to survive—as they are not motile organisms, and their survival depends on strong, rigid structures. Animal cells and gram-positive cells (to a certain degree) are amorphous and can change shape, since the outer plasma membrane consists of a dynamic lipid bilayer without the constraints of an additional outer cell wall (which would hinder survival in animal cells).
The anterior nares are the external (or "proper") portion of the nostrils (nose). The anterior nares opens into the nasal cavity and allow the inhalation and exhalation of air. Each is an oval opening that measures about 1.5 cm anteroposteriorly and about 1 cm in diameter.
The anterior nares are commonly infected by Staphylococcus aureus (also known as "golden staph") which may contribute to dermatitic skin lesions in patients with atopic dermatitis. The anterior nares can act as a colonizing point from which the infection can spread to other areas (and they should probably be checked in the case of a recurring staph infection). This can be particularly troublesome if the strain is an antibiotic resistant (commonly MRSA or ORSA) strain. MRSA (first discovered in the UK in 1961) has become particularly widespread in hospitals and is commonly considered a superbug. For more information on symptoms and treatment see MRSA.
Staphylococcus aureus is a bacterium that is a member of the Firmicutes, and is frequently found in the human respiratory tract and on the skin. Although S. aureus is not always pathogenic, it is a common cause of skin infections (e.g. boils), respiratory disease (e.g. sinusitis), and food poisoning. Disease-associated strains often promote infections by producing potent protein toxins, and expressing cell-surface proteins that bind and inactivate antibodies. The emergence of antibiotic-resistant forms of pathogenic S. aureus (e.g. MRSA) is a worldwide problem in clinical medicine.
Staphylococcus was first identified in 1880 in Aberdeen, United Kingdom, by the surgeon Sir Alexander Ogston in pus from a surgical abscess in a knee joint. This name was later appended to Staphylococcus aureus by Rosenbach who was credited by the official system of nomenclature at the time. It is estimated that 20% of the human population are long-term carriers of S. aureus which can be found as part of the normal skin flora and in anterior nares of the nasal passages. S. aureus is the most common species of staphylococcus to cause infectionsStaph and is a successful pathogen due to a combination of nasal carriage and bacterial immuno-evasive strategies. S. aureus can cause a range of illnesses, from minor skin infections, such as pimples, impetigo, boils (furuncles), cellulitis folliculitis, carbuncles, scalded skin syndrome, and abscesses, to life-threatening diseases such as pneumonia, meningitis, osteomyelitis, endocarditis, toxic shock syndrome (TSS), bacteremia, and sepsis. Its incidence ranges from skin, soft tissue, respiratory, bone, joint, endovascular to wound infections. It is still one of the five most common causes of nosocomial infections and is often the cause of postsurgical wound infections. Each year, some 500,000 patients in American hospitals contract a staphylococcal infection.