Staphylococcus Balsam Miri

General Characteristics of the Staphylococci Gram-positive cocci Arranged in irregular grape-like clusters but may also be seen as pairs/tetrads or short chain Lack spores and flagella May have capsules Common inhabitant of the skin and mucous membranes About 40 Staphylococcus spp.are known

Morphology Staphylococci are spherical cells arranged in grape like clusters. Single cocci, pairs, tetrads and chains are also seen. Young cocci stain Gram (+), but on aging many cells become Gram (-). Staphylococci are nonmotile and do not form spores. Some are encapsulated.

Cultural charecteristics Staphylococci grow on most bacteriologic media under aerobic or microaerophilic conditions. They grow at 37Cْ but form pigment best at room temperature (20 – 25 Cْ ). Colonies on nutrient agar are round, smooth, raised and glistening. staph.aureus usually forms deep golden yellow colonies. Staph.epidermidis colonies usually gray to white color. On blood agar the staph.aureus cause -haemolysis. Staph. aureus can grow in high concentration of NaCl (7.5-10 %).

Biochemical reaction Staphylococci ferment many carbohydrate (glucose, lactose , sucrose, mannitol) produce acid without gas. Staphylococci produce catalase which differentiates them from the streptococci. The mannitol fermentation is very important due to its association with pathogenicity and coagulase and phosphatase production.

Resistance Staphylococci are resistant to drying heat (but die in 60 Cْ for 60 min.) and resistant to 10 % Nacl and phenol and mercuric chloride. But they sensitive to basic dyes like gention violet or crystal violet which adds to selective media to differentiate the Staphylococci from streptococci.

Antigenic structure substance important in cell wall structure. Peptidoglycan, a polysaccharide polymer, it is important in the production of IL-1 (interlukin-1) and stimulate the production of antibody. Teichoic acid, which are polymer of glycerol or ribitol phosphate. Antiteichoic antibodies detected in patients with active endocarditis due to Staph. aureus. Protein A is a cell wall component of many Staph. aureus that binds to the Fc portion of IgG molecules. Some Staph. aureus strains have capsule, which inhibit phagocytosis.

Enzymes 1-Coagulase (bound and free) which clots plasma and coats the bacterial cell which probably prevent phagocytosis 2-Hyalouronidase also known as spreading factors that breakdown hyaluronic acid and help in spreading of Staphylococcus aureus. 3-Catalase which convert the hydrogen peroxide to water and oxygen. 4- DNAse (deoxyribonuclease) which breakdown the DNA.

Toxins Toxic Shock Syndrome Toxin (TSST-1), is superantigen which causes TSS associated with tampone use. This is characterized by fever, erythematous rash, hypotension, shock, multiple organ failure, and skin desequemation. Enterotoxin that is the causative agent of S. aureus gastroenteritis . The enterotoxin are stable to heating at 100 ° C for 30 minutes and are resistant to hydrolysis by gastric and jejunal enzymes .This gastroenteritis is characterized by vomiting and diarrhea one to six hours after ingestion of the toxin. Symptoms include nausea, vomiting, diarrhea, and major abdominal pain.

Toxin 3-Exfoliative toxins ,EF toxins are implicated in the disease staphylococcal scalded skin syndrome (SSSS), which occurs most commonly in infants and young children. It also may occur as epidemics in hospital. The protease activity of the exfoliative toxins causes peeling of the skin observed with SSSS. 4-Other toxins Staphylococcal toxins that act on cell membrane include alpha toxin, beta toxin, delta toxin

Diseases Staphylococcal scalded skin syndrome (SSSS) Toxic shock syndrome (TSS). Mastitis in cattle, the infection may be chronic or acute, the later is include sudden fever, loss of appetite, enlargement of infected udder. The milk contain blood or pus, toxemia and death may occurs after 3-4 days. Staphylococcosis in poultry: the staphylococci cause many infection in birds, it cause yolk sac infection in embryo and acute septicemia in adult chickens. Also it cause chronic arthritis and bumble foot.

Diagnosis 1-Speciemens: swab of pus, blood, or spinal fluid. 2- Smears: smear of pus or sputum. It is not possible to distinguish saprophyticus from pathogenic organisms. 3- Culture: Staph. aureus but not others ferment mannitol. Specimens contaminated with mixed flora can be cultured on media containing 7.5-10% Nacl. 4-Catalase test: Staph. aureus is catalase (+). 5-Coagulase test (All coagulase + staphylococci are pathogenic for human and animals)

S. aureus morphology

Morphology Staph vs. Strep Gram-positive cocci in clusters

Streptococcus Staphylococcus

Mannitol Salts Agar (MSA) Staphylococcus aureus

Blood agar plate, S. aureus

Staphylococcal Disease Range from localized to systemic Localized cutaneous infections – invade skin through wounds, follicles, or glands Folliculitis – superficial inflammation of hair follicle; usually resolved with no complications but can progress Furuncle – boil; inflammation of hair follicle or sebaceous gland progresses into abscess or pustule Carbuncle – larger and deeper lesion created by aggregation and interconnection of a cluster of furuncles Impetigo – bubble-like swellings that can break and peel away; most common in newborns

Clinical Manifestations/Disease SKIN folliculitis boils (furuncles) carbuncles impetigo (bullous & pustular) scalded skin syndrome Neonates and children under 4 years

Clinical Manifestations/Disease Primary staphylococcal pneumonia Food poisoning / neusea ,vomiting, diarhea. Toxic shock syndrome – toxemia leading to shock and organ failure Symptoms are fever, diarhea, hypotention

Staphylococcal Disease Staphylococcal scalded skin syndrome – toxin induces bright red flush, blisters, then desquamation of the epidermis

Localised infections Impetigo Very common cause of infection by staphylooccal spp. Often results in pus formation Can result in skin, soft tissue infection or deep abscesses Impetigo

Boil (Furuncle)

Carbuncle

Stye

Surgical wound infections: many causes including S. aureus

Staphylococcal mucositis

Local staphlococcal infections inside oral cavity

Laboratory Diagnosis: Cultural Characteristics Colony morphology Smooth, white to yellow, creamy S. aureus may produce hemolysis on blood agar S. aureus

Laboratory Diagnosis: Cultural Characteristics Coagulase-negative staphylococci Smooth, creamy, white Small-to medium- sized, usually non-hemolytic S. saprophyticus Smooth, creamy, may produce a yellow pigment

Identification Tests: Catalase Principle: tests for enzyme catalase 2 H2O2 2 H2O + O2 Drop H2O2 onto smear Bubbling = POS (Most bacteria, O2 generated) No bubbling = NEG (Streptococci and other lactic acid bacteria, no O2 generated)

Differential Characteristics Catalase 2H2O2  O2 + 2H2O Streptococci vs. Staphylococci

Catalase POS Staphylococcus Catalase NEG

Differential Characteristics S. aureus Coagulase Fibrinogen  Fibrin

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. resistance does make MRSA infection more difficult to treat with standard types of antibiotics and thus more dangerous