Gram Positive Cocci-Staphylococcus

Staphylococcus pathogenecity

1. GRAM POSITIVE COCCI (Staphylococcus) SAMIRA FATTAH HAMID Ph.D. Medical Bacteriology College of Health Sciences Hawler Medical University

2. GRAM POSITIVE COCCI Genus Staphylococcus Genus Streptococcus

3. GENUS: STAPHYLOCOCCUS Characteristics: Gram positive spherical cells, usually arranged in grape-like clusters. Facultatively anaerobic non spore-forming non-motile, Form single cocci , pairs, tetrads and clusters.

4. GENUS: STAPHYLOCOCCUS Characteristics: They are salt tolerant, capable of growing in media saturated with Nacl —about 28% salt—which explains how they tolerate the salt deposited on human skin by sweat glands. synthesizes catalase enzyme which differentiate them from the streptococci. Tolerant to radiation, and heat (up to 60°C for 30 minutes),allowing them to survive on environmental surfaces in addition to skin.

5. Characteristics: Active metabolically, ferment carbohydrates producing lactic acids. Produce pigments that vary from white to deep yellow. Some are members of the normal microbiota of the skin and mucous membranes of humans; others cause suppuration, abscess formation and even fatal septicemia. The pathogenic staphylococci often hemolyze blood, coagulate plasma, and produce a variety of extracellular enzymes and toxins. GENUS: STAPHYLOCOCCUS

6. The genus Staphylococcus has at least 40 species. The most frequently encountered species of clinical importance are: Staphylococcus aureus Staphylococcus epidermidis Staphylococcus saprophyticus

7. Less common staphylococcus species: Staphylococcus haemolyticus Staphylococcus xylosus Staphylococcus lentus Staphylococcus lugdenensis Staphylococcus hominis Staphylococcus warneri

8. Staphylococcus aureus S. aureus is a relatively common human commensal, nasal carriage occurs in 30–50% of healthy adults, faecal carriage in about 20% and skin carriage in 5–10%. Antigenic structure Peptidoglycan: a polysaccharide polymer containing linked subunits, provides the rigid exoskeleton of the cell wall. destroyed by strong acid or exposure to lysozyme. It is important in the pathogenesis of infection: It trigger production of interleukin-1 and antibodies by monocytes. It can be a chemoattractant for polymorphonuclear leukocytes, have endotoxin-like activity, and activate complement.

9. Antigenic structure 2. Teichoic acid: polymers of polyribitol –phosphate, are cross- linked to the peptidoglycan and can be antigenic, can trigger activation of complement. Staphylococcus aureus

10. Staphylococcus aureus Antigenic structure Protein A: Protein A binds to the Fc portion of immunoglobulins (IgG). It is assumed that “false” binding of immunoglobulins by protein A prevents “correct” binding of opsonizing antibodies, thus hindering phagocytosis.

11. Antigenic structure Capsule: polysaccharide inhibit phagocytosis by polymorphonuclear leukocytes. At least 11 serotypes have been identified, with types 5 and 8 responsible for the majority of infections. Staphylococcus aureus

12. Enzymes Catalase Produced by staphylococci converts H 2 O 2 into H 2 O and O 2 . Coagulase and clumping factor Coagulase deposit fibrin on the surface of organism and alter ingestion by phagocytic cells. Clumping factor : A surface compound that is responsible for adherence of the organism to fibrinogen and fibrin. Staphylokinase (Fibrinolysin)-digest fibrin clots Staphylococcus aureus

13. Staphylococcus aureus Enzymes Hyaluronidase -Spreading factor- hydrolyze hyaluronic acid Proteinases -hydrolyze protein Lipases -hydrolyze lipid DNase - Deoxyribonucleotidase β-lactamase -Provides resistance of staphylococcus to β-lactam antibiotic like penicillin.

14. Staphylococcus aureus Toxins Hemolysins S. aureus possesses four hemolysins , capable of lysing white and red blood cells. Panton–Valentine Leukocidin It can kill white blood cells of humans. This toxin is an important virulence factor in CA-MRSA infections.

15. Staphylococcus aureus Toxins Exfoliative Toxins Epidermolytic toxins dissolve the mucopolysaccharide matrix of the epidermis. composed of two distinct proteins of the same molecular weight. Exfoliative toxin A: heat stable (resists boiling for 20 minutes). Exfoliative toxin B: heat labile. Toxic Shock Syndrome Toxin Desquamative toxin produced by S. aureus it binds to major histocompatibility class (MHC) class II molecules, yielding T-cell stimulation and causes fever, shock, multiple-organ failure and skin rash.

16. Staphylococcus aureus Toxins Enterotoxin There are multiple enterotoxins (A–E, G–J, K–R and U, V), produced when S. aureus grown in carbohydrate and protein foods. heat stable and resistant to the action of gut enzymes. Important causes of food poisoning , Ingestion of 25 μg of enterotoxin B results in vomiting and diarrhea. The emetic effect of enterotoxin is probably the result of central nervous system stimulation (vomiting center) after the toxin acts on neural receptors in the gut.

17. Pathogenesis and clinical features Staphylococcus causes a variety of medical problems, depending on the site of infection , the immune state of its host, and the toxins and enzymes of a particular species or strain secretes . Cutaneous diseases Folliculitis : Infection of one hair follicle in which the base of the follicle becomes red, swollen, and pus filled. Furuncle or boil is a large, painful raised nodular extension of folliculitis into surrounding tissue. Carbuncle : When several furuncles unite, they form a carbuncle (infection of multiple hair follicle and surrounding skin), which extends deeper into the tissues.

18. Pathogenesis and clinical features Cutaneous diseases impetigo : Small, flattened, red patches on the face and limbs, particularly of children whose immune systems are not fully developed Cellulitis : Infection of skin and subcutaneous tissue.

19. Pathogenesis and clinical features Cutaneous diseases Staphylococcal scalded skin syndrome : is a reddening of the skin that typically begins near the mouth, spreads over the entire body, and is followed by large blisters that contain clear fluid lacking bacteria or white blood cells. These are lacking because the syndrome is caused by exfoliative toxin released by bacteria growing on the skin rather than in the body. Within two days, the affected outer layer of skin (epidermis) peels off in sheets, as if it had been dipped into boiling water.

20. Pathogenesis and clinical features Systemic diseases Toxic shock syndrome : (Non-Streptococcal) When strains of Staphylococcus that produce TSS toxin grow in a wound or in scraped vagina, the toxin can be absorbed into the blood and cause toxic shock syndrome, characterized by fever, vomiting, red rash, extremely low blood pressure, and loss of sheets of skin. TSS is fatal to 5% of patients when their blood pressure falls so low that the brain, heart, and other vital organs have an inadequate supply of oxygen—a condition known as shock.

21. Pathogenesis and clinical features Systemic diseases Bacteremia S. aureus is a common cause of bacteremia , the presence of bacteria in the blood. After staphylococci enter the blood from a site of infection, they travel to other organs of the body, which may become infected. Furuncles, vaginal infections, infected surgical wounds, and contaminated medical devices such as intravascular catheters have all been implicated in cases of bacteremia.

22. Pathogenesis and clinical features Systemic diseases Endocarditis S. aureus may attack the lining of the heart (including its valves), producing a condition called endocarditis. Typically, patients with endocarditis have nonspecific, flulike symptoms, but their condition quickly deteriorates as the amount of blood pumped from the heart drops quickly. About 50% of patients with endocarditis do not survive.

23. Pathogenesis and clinical features Systemic diseases Pneumonia and Empyema Staphylococcus in the blood can invade the lungs, causing pneumonia - an inflammation of the lungs in which the alveoli (air sacs) and bronchioles (smallest airways) become filled with fluid. In 10% of patients with staphylococcal pneumonia, infection spreads to the space between a lung and the chest wall where pus builds up—a condition known as empyema .

24. Pathogenesis and clinical features Systemic disease Osteomyelitis When Staphylococcus invades a bone, either through a traumatic wound or via the blood during bacteremia, it causes osteomyelitis - inflammation of the bone marrow and the surrounding bone. Osteomyelitis is characterized by pain in the infected bone accompanied by high fever. In children, the disease typically occurs in the growing regions of long bones, which are areas with well-developed blood supplies. In adults, osteomyelitis is more commonly seen in vertebrae.

25. Pathogenesis and clinical features Systemic disease Food poisoning Symptoms come on quickly, usually within hours of eating a contaminated food. Symptoms usually disappear quickly, too, often lasting just half a day. A staph infection in food usually doesn't cause a fever. Signs and symptoms include: Nausea and vomiting Diarrhea Dehydration Low blood pressure

26. Staphylococcus epidermidis S. epidermidis is part of the normal human flora, typically the skin flora, and less commonly the mucosal flora. Although it is not usually pathogenic, patients with compromised immune systems are at risk of developing infection. S. epidermidis is a particular concern for people with catheters or other surgical implants because it is known to form biofilms that grow on these devices. Being part of the normal skin flora, S. epidermidis is a frequent contaminant of specimens sent to the diagnostic laboratory.

27. Staphylococcus epidermidis Diseases S. epidermidis causes biofilms to grow on plastic devices placed within the body like intravenous catheters and medical prostheses. Infection can also occur in dialysis patients by contaminated device. It also causes endocarditis, most often in patients with defective heart valves.

28. Staphylococcus epidermidis Diseases Occasional cause of infection associated with implanted appliances and devices.

29. Staphylococcus epidermidis R ole of Staphylococcus epidermidis in acne vulgaris Staphylococcus epidermidis in the normal skin is nonpathogenic. But in abnormal lesions, it becomes pathogenic, likely in acne vulgaris. Staphylococcus epidermidis enters the sebaceous gland (where Propionibacterium acnes the main bacterium that causes acne vulgaris colonizes) and damages the hair follicles by producing lipolytic enzymes that change the sebum triglyceride to free fatty acids leading to inflammatory effect.

30. Staphylococcus saprophyticus S. saprophyticus is part of the normal human flora that colonizes the: Perineum Rectum Urethra Cervix Gastrointestinal tract.

31. Staphylococcus saprophyticus It is a common cause of uncomplicated urinary tract infections (UTIs), particularly in young sexually active females. Less commonly, it is responsible for complications including: acute pyelonephritis Cystitis Urethritis prostatitis

32. Staphylococcus saprophyticus An acute uncomplicated UTI is characterized by dysuria and frequency in an immunocompetent, non-pregnant adult female and is the most common bacterial infection in women. A complicated infection typically involves a patient that is immunocompromised, elderly, male, pregnant, diabetic, and/or with urologic abnormalities such as indwelling catheters or kidney disease.

33. Treatment Penicillin sensitive staphylococci………penicillin, ampicillin Penicillin resistant staphylococci………cloxacillin, Nafcillin Methicillin resistant staphylococci……… Vancomycin