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Gram Positive Bacteria
Have a cell wall that contains a thick out layer of peptidoglycan laced with lipoteichoic acid and teichoic acid. Feature staphylococcus, streptococcus, enterococcus, bacillus, and clostridium. Mostly cause disease from secreted toxins
Low G and C Bacteria
Low amount of Guanine-Cytosine nucleotide base pairs versus Adenine-Thymine nucleotide base pairs
High G and C Bacteria
High amount of Guanine-Cytosine nucleotide base pairs versus Adenine-Thymine nucleotide base pairs
Staphylococcus
Many are normal members of residential microbiota. Under certain conditions can become opportunistic pathogens, resulting in minor to life threatening conditions. They are facultative Anaerobes, nonmotile (lack flagella), and are spheres in grape like arrangement
Facultative Anaerobe
Prefer to grow in an environment with oxygen for aerobic respiration but can grow and survive in environments without oxygen (staphylococcus)
Salt
Staphylococcus are able to survive on the epidermis that has this deposited on it from sweat glands because it is tolerant of it
Catalase
Staphylococcus contains this enzyme and will bubble and release O2 when exposed to hydrogen peroxide
Desiccation, Radiation, and Heat
Staphylococcus can tolerate harsh environment conditions like this which allows them to survive for a long time on environmental surfaces outside the human body
Staphylococcus aureus
More virulent strain causing a wide variety of disease conditions and symptoms depending on site of infection. Will ferment mannitol causing the pH to become acidic. This causes the pH indicator phenol red to turn yellow and changes the media color on an MSA plate
Staphylococcus epidermidis
Normal microbiota of the human skin but can cause opportunistic infections in very rare cases. Will not ferment mannitol on an MSA plate and leaves the media a pink color
Mannitol Salt Agar
Can be used to identify S. aureus and S. epidermidis. They grow because they can tolerate salt
Pathogenicity of Staphylococcus
Infection results when they breach the body’s skin or mucus membrane to reach the blood. Only takes a few hundred to cause disease, results from extracellular enzymes, antiphagocytic structures, and toxins
Cell-Free Coagulase
Causes blood clotting, reacts with prothrombin, causing the inactive fibrinogen to convert to the active fibrin. Fibrin causes red blood cells to clot
Staphylokinase
Dissolves fibrin causing blood clots to breakdown or dissolve, allows S. aureus to free itself from clots and spread through blood vessels
Hyaluronidase
Skin cells in the epidermis are tightly backed and glue together by hyaluronic acid. Allows the bacteria pass between cells in the epidermis by breaking down hyaluronic acid
Lipases
Breaks down lipids/oil for energy on the skin, allowing staphylococci to grow on the surface of the skin and in cutaneous oil glands
B Lactamase
Gives antibiotic resistance as this enzyme breaks open and destroys the beta lactam ring found in all beta lactam antibiotics such as penicillin
Protein A
Aureus. staphylococcus coats their cells with this. B cells release antibodies that bind to the surface of the bacteria where phagocytes can grip. This makes it easier for phagocytes to adhere to and engulf the bacteria. This binds to antibodies, blocking the location where phagocytes grab on to the antibodies during phagocytosis
Slime Layer
Inhibits leukocyte chemotaxis and phagocytosis, also has a capsule
Cytolytic Toxins
This binds and weakens/destroys the plasma membrane
Leukocidin Toxin
Specifically binds to and destroy all leukocytes
Exfoliative Toxins
These breakdown desmosomes, causing skin cells to separate and slough off
Enterotoxins
Stimulates intestinal contraction, nausea, and intense vomiting (food poison symptoms). These enzymes are very heat stable, meaning they do not breakdown at high temperatures
Epidemiology
The study of the incidence, distribution, and control of disease
Staphylococcus epidermidis
Found everywhere on human skin. Grow in the upper respiratory, gastrointestinal, and urogenital tracts of humans. Transmitted by direct contact or fomites, can be prevented by aseptic techniques and handwashing.
Staphylococcus aureus
Usually only found in moist skin folds. Grow in the upper respiratory, gastrointestinal, and urogenital tracts of humans. Transmitted by direct contact or fomites, can be prevented by aseptic techniques and handwashing.
Noninvasive Disease
Food poisoning due to the ingestion of enterotoxins left in contaminated food NOT bacteria growth. Food left at room temperature for several hours allows bacteria to grow long enough to produce enterotoxins. These toxins are stable at high temperatures, you can kill the bacteria when reheating food but not the enterotoxins
Scalded Skin Syndrome
Blistering and peeling of skin due to exfoliative toxins. These spread through the blood stream and bind to target proteins on the epidermis, layers of the epidermis peel off in sheets
Impetigo
Formation of red sores that eject fluid and leave an amber colored scab. These red sores are filled with bacteria, pus, and leukocytes
Toxic Shock Syndrome
Some Staphylococcus strains produce this toxin inside wounds. The toxin is absorbed and spread through the blood producing fever, vomiting, rash, and low blood pressure. This can be fatal if blood pressure drops so low that vital organs do not get enough oxygen to function
Bacteremia
Presence and spreading of the bacteria in the blood
Endocarditis
The bacteria attack and damage to the lining of the heart. This causes the amount of blood pumped by the heart to drop rapidly
Pneumonia
Inflammation of the lungs, empyema occurs when pus fills the lungs
Osteomyelitis
Inflammation of bone and blood marrow
Treatment of Staphylococcus
Due to beta lactamase, these bacteria are resistant to penicillin. Semisynthetic penicillin-methicillin is commonly used, some strains are resistant to this called methicillin-resistant Staphylococcus aureus (MRSA).
Vancomycin is used for infections that does not respond to penicillin-methicillin