Staphylococcus Coccus - Lecture Outline PDF

STAPHYLO COCCUS Dr. NAWAID HUSSAIN KHAN, Ph.D. ASSISTANT PROFESSOR(MICROBIOLOGY & MOLECULAR MEDICINE) ALA-TOO INTERNATIONAL UNIVERSITY Lecture outline:  Introduction, History, Classification  Morphology & Biochemical Characteristics.  Pathogenicity & Virulence factors...

STAPHYLO COCCUS Dr. NAWAID HUSSAIN KHAN, Ph.D. ASSISTANT PROFESSOR(MICROBIOLOGY & MOLECULAR MEDICINE) ALA-TOO INTERNATIONAL UNIVERSITY Lecture outline:  Introduction, History, Classification  Morphology & Biochemical Characteristics.  Pathogenicity & Virulence factors  Clinical manifestation  Laboratory Diagnosis and Treatments  Drug Resistances in S. aureus  Coagulase negative Staphylococcus Introduction:  Staphylococci - Greek “staphyle” (bunch of grapes)  and “Kokkos” = berry, meaning bacteria occurring in grapelike clusters or berry.  >40 species are known  Occur as commensal on skin and mucous membrane  Natural habitat: Nostril and skin (Present on the skin and mucus membrane)  Major human pathogen, Some act as opportunistic pathogens  causing pyogenic infections.  Can surviving many non-physiologic conditions History:  Robert Koch (1878)- first to see staphylococci in pus specimen  Louis Pasteur (1880)- first to cultivate in liquid medium  Sir Alexander Ongston (1881)- named the bacteria as “Staphylococcus” Morphology & Biochemical Characteristics:  Gram-positive cocci, 0.5-1.5 μm in diameter  Occur characteristically in group, also singly and in pairs Form irregular grapelike clusters (divide in 3 planes), Non- motile, Non- spore forming, Catalase positive, Oxidase negative, Few strains are capsulated  Mostly aerobic or facultative anaerobic (2 species = S. anaerobius and S. saccharolyticus are anaerobic and catalase negative)  Grow in media containing 10% NaCl at temp= 18 to 40°C  Coagulase positive = S. aureus, S. intermedius, are important pathogen to human.  Coagulase negative staphylococci are low virulence, some occasionally cause disease in humans and animals. Classification: S. citrus : lemon yellow colonies. Based on pathogenicity: Pathogenic: i.e. S. aureus Opportunistic pathogens: S. epidermidis, S. saprophyticus Non-pathogenic: S. albus, S. citrus, S. hominis etc. Based on pigment production: Based on coagulase production: S. aureus : golden-yellow Coagulase positive: S. aureus pigmented Coagulase negative: S. Colonies. epidermidis, S. saprophyticus. S. albus : white colonies. Pathogenicity: Infections:  Cocci enter via damaged skin/ mucosa/tissue –Colonies locally – Evade host mechanism –Tissue damage Source of infection: A) Exogenous: patients or carriers B) Endogenous: From colonized site Mode of transmission: A) Contact: direct or indirect B) Inhalation of infected air-borne droplets Virulence factors:  CELL ASSOCIATED FACTORS:  Two types: Capsule CELL ASSOCIATED FACTORS Peptidoglycan EXTRACELLULAR FACTORS Teichoic acid  Also classified as: Protein A A. Cell associated polymers B. Cell surface proteins C. Enzymes D. Toxins Capsular polysaccharide:  Some strains produce exopolysaccharide (helps in adherence to host cell & prosthetic devices).  protects bacteria by inhibiting chemotaxis and phagocytosis  facilitates adherence of bacteria to catheters and synthetic materials  Clinical isolates of SA – classified into 11 types based on capsular polysaccharide immunotyping.  70-80% of significant clinical isolate belong to capsular serotype 5 or 8. Peptidoglycan & Teichoic Acid:  Cell wall contain peptidoglycan consisting of layers of glycan chains with alternating subunits of N – acetylmuramic acid and N-acetylglucosamine (NAG & NAM) & teichoic acid.  Functions: Specific adherence of bacteria to mucosal surfaces., Provides rigidity & resilience to the cell wall, Adhesins, fibronectin-binding proteins, collagen-binding proteins & clumping factors are covalently incorporated into peptidoglycan, and have endotoxin-like activity. Cell Associated factor-Protein-A:  MW: 42 kDa  Found on cell surface & in growth medium.  Ability to bind the Fc region of all human IgG (except IgG3 ).  Interfere with opsonization & ingestion of the organism by PMN cells, activating complement & eliciting immediate & delayed-type hypersensitivity reactions.  It is immunogenic; abs are found in patients with serious S.aureus infections.  The presence of protein A provides the basis for the Co- agglutination reaction (used for streptococcal grouping) and detection of bacterial Ags in body fluids. Extracellular factors-Enzyme:  Catalase: All staphylococci produce catalase, which catalyzes the conversion of toxic hydrogen peroxide to water and oxygen.  Hydrogen peroxide can accumulate during bacterial metabolism or after phagocytosis.  Coagulase: S. aureus strains possess two forms of coagulase: bound and free.  Coagulase of staphylococcal can directly convert fibrinogen to insoluble fibrin and form a clump. Hyaluronidase:  Hyaluronidase hydrolyses hyaluronic acid, the acidic mucopolysaccharides present in the acellular matrix of connective tissue. This enzyme facilitates the spread of S. aureus in tissues. More than 90% of S. aureus strains produce this enzyme.  Lipases: Seen in chronic furunculosis patients. Spread organisms in cutaneous & subcutaneous tissues.  Other: DNase, Thermonuclease, Staphylokinase (fibrinolysin), Phosphatase TOXINS: ALPHA HEMOLYSIN: CYTOLYTIC TOXINS: – inactivated at 70°C but membrane-active substances, reactivated at 100°C consisting of four hemolysins – Lyse rabbit erythrocyte but & a leucocidin less active against sheep and 1. Alpha hemolysin human red cells. 2. Beta hemolysin – Toxic to macrophages, 3. Gamma hemolysin lysosomes, muscle tissue, renal cortex & circulatory 4. Delta hemolysin system 5. Leucocidin BETA HEMOLYSIN- LEUCOCIDIN It is a sphingomyelinase, hemolytic for (PANTON- sheep cells but not for human & rabbit VALENTINE cells. TOXIN/PVL) Exhibit hot-cold phenomenon(hemolysis – Composed of S & F being initiated at 37°C but becoming components. evident only after chilling) GAMMA HEMOLYSIN- – Damages PMN cells & macrophages. Composed of 2 separate proteins ( necessary for hemolytic activity) – Grouped as DELTA HEMOLYSIN – synergo- hymenotropic toxins. Detergent-like effect on cell membrane of erythrocyte, leucocyte, macrophage & platelet. ENTEROTOXINS: Source of infection: food Staphylococcal Food handler(carrier). poisoning: contaminated food. - Recovery: 24-48 hours. – Nine antigenic types are - Toxin acts directly on the currently known (A, B, C1, C2, Autonomic nervous system C3, D, E, H, I). (ANS). – Toxin A – most cases. - Enterotoxin : superantigen – Resistance- Gut enzymes, - Toxin is antigenic- Boiling for 30 minutes neutralized by specific – Common food items: antitoxin. carbohydrate, protein food, - Toxin detection: ELISA, meat & fish, milk & milk latex agglutination product cooked & left at room temperature. TOXIC SHOCK SYNDROME  Proteolytic, dissolves TOXIN (TSST) mucopolysaccharide Superantigen - TOXIC SHOCK matrix of epidermis. SYNDROME  Epidermal splitting Most TSST producing strain belongs to Bacteriophage group-I blistering disease. (TSST TYPE-I)  Staphylococcal EXFOLIATIVE (EPIDERMOLYTIC) Scalded Skin TOXIN Syndrome (SSSS), 2 types- ET-A and ET-B Severe form: Ritter’s – ET-A – heat stable disease (new-born) & (chromosomal) toxic epidermal – ET-B – heat-labile (plasmid- necrolysis (older mediated) patients) Produced by some strains of Staph. aureus (phage group II) Clinical manifestation: Diseases produced by staphylococcus aureus: 2 - groups INFECTIONS INTOXICATION Skin and soft tissue infection – Folliculitis – Furuncle (boil) – Carbuncle – Impetigo – abscess – Wound infection  Central nervous system Musculoskeletal infection  Abscess Osteomyelitis  Meningitis Periostitis  Intracranial thrombophlebitis Endovascular Respiratory  Bacteremia  Tonsilitis  Septicemia  Pharyngitis  Pyemia  Sinusitis  Endocarditis Urinary tract infection  Otitis The diseases are caused by bacterial  Bronchopneumonia toxins. 1. Food poisoning  Lung abscess 2. Toxic shock syndrome (TSS)  Empyema 3. Staphylococcal scalded skin syndrome (SSSS)  Sty: Folliculitis: A sty is folliculitis affecting It is inflammation of the hair one or more hair follicles follicles. on the edge of the upper or A small red bump or pimple lower eyelid develops at infection sites of hair follicles. Furuncle/boils: Carbuncle: Furuncle is a deep-seated Carbuncle is an infection, originating from aggregation of infected folliculitis,( if infection extends furuncles. from follicle to neighbor Carbuncles may form large tissue) Causes redness, Abscesses, It is a large swelling, and severe pain and areas of redness, swelling, is commonly found on the and pain, punctuated by neck, armpit, and groin several sites of drainage regions. pus. Impetigo: a very superficial skin infection usually produces blisters or sores on the face, neck, hands, and diaper area. It is characterized by watery bristles, which become pustules and then a honey-colored crust. Musculoskeletal infection: Osteomyelitis: Septic arthritis – knee, inflammation of bone shoulder, hip, phalanges Bacteria can get to the Osteomyelitis – children: long bone bones, adults: vertebrae – Via bloodstream Pyomyositis – skeletal muscle – Following an injury infection Clinical features: pain, Bursitis swelling, deformity, defective healing, in some cases pus flow, Diagnosis: X-ray, MRI, bone aspirates Periostitis: inflammation of periosteum Clinical features: fever, localized pain, leucocytosis Diagnosis: needle aspiration of subperiosteal fluid Endocarditis: It is an inflammation of the inner layer of the heart, the endocardium Endocarditis occurs- when bacteria enter the bloodstream, travel to the heart, and lodge on abnormal heart valves or damaged heart tissue Food poisoning: (Enterotoxin) Enterotoxin is responsible for manifestations of staphylococcal food poisoning. Nine types of enterotoxin are currently known, named A, B, C1-3, D, E, H & I. It usually occurs when the preformed toxin is ingested with contaminated food. The toxin acts directly on the autonomic nervous system to cause the illness, rather than gut mucosa. The common food items responsible are – milk and milk products, meat, fish, and ice cream. Source of infection- food handler who is a carrier. Incubation period- 2 to 6 hours. Clinical symptoms- nausea, vomiting, and diarrhea. The illness is usually self-limited, with recovery in a day. Staphylococcal Toxic shock syndrome (STSS):  STSS is associated with infection of mucosal or sequestered sites by TSST( formerly known as enterotoxin type F) producing S. aureus.  It is a fatal multisystem disease presenting with fever, hypotension, myalgia, vomiting, diarrhea, mucosal hyperemia, and an erythematous rash which desquamates subsequently. Staphylococcal scalded skin syndrome (SSSS):  Caused by Exfoliative toxin produced by S. aureus.  It is a skin disease in which the outer layer of the epidermis gets separated from the underlying tissues.  IN NEWBORN- RITTER’S DISEASE, PEMPHIGUS NEONATORUM  IN OLDER PATIENTS EPIDERMAL NECROLYSIS , BULBOUS IMPETIGO Laboratory Diagnosis: Specimens: – Pus: from wound or abscess or burns – Nasal Swab: from suspected carrier – Food: to diagnose staphylococcal intoxication – Blood: to diagnose endocarditis and bacteremia – Sputum: to diagnose lower respiratory tract infection Direct smear microscopy: Culture Media:  gram stain = positive,  Nutrients agar, Blood Spherical, Grape-like clusters. agar.  Non-motile, Non-sporing, Non-  Selective media: capsulated {Few strains Mannitol salt agar, possess microscopically visible Salt milk agar, capsules (young cultures)}. Ludlam’s medium  CULTURE CHARACTERISTICS: Aerobes and facultative anaerobes, Temperature = 10°C to 42°C (37°C), pH = 7.4 - 7.6 On Nutrient agar: On Blood agar- golden yellow colonies, surrounded by a clear golden yellow and opaque zone of hemolysis (beta- colonies with a smooth hemolysis) glistening surface, 2-4 mm in On MacConkey agar – Smaller diameter, circular, convex, colonies than those on Nutrient smooth, shiny & easily agar and are pink colored due to lactose fermentation. emulsifiable (max. pigment production at 22 °C & only in On Mannitol salt agar – S.aureus ferments mannitol and appears aerobic cultures). as yellow colonies – MSA is a useful selective medium for recovering S.aureus from fecal specimens, when investigating food poisoning Biochemical properties:  Catalase positive  Oxidase negative  Ferment glucose, lactose, maltose, sucrose, and mannitol, with the production of acid but no gas  Mannitol fermentation carries diagnostic significance  Indole test= negative  MR test= positive  VP test= positive  Urease test= positive  Hydrolyse gelatin  Reduces nitrate to nitrite  Phospahatase= positive  DNA-ase test= positive  Coagulase test= positive Treatment:  Methicillin-resistant Staphylococcus aureus (MRSA)  Antibiotic susceptibility strains have become common testing should be done now.  Vancomycin is used in the before treatment. treatment of infections with MRSA  Drug resistance is strains. common.  Vancomycin resistance is very rare – so far MRSA was considered  Benzyl penicillin is the to be Hospital-acquired But, most effective antibiotic if Community-acquired cases now (CAMRSA) the strain is sensitive.  Methicillin-resistant S. epidermidis  Cloxacillin or Methicillin is - MRSE used against beta-  VRSA= vancomycin-resistant lactamase-producing Staphylococcus aureus strains.  VISA= vancomycin-intermediate Staphylococcus aureus Drug Resistances in S.  PRODUCTION OF BETA aureus: LACTAMASE:  S. Aures shows resistance (PENICILLINASE)- to beta-lactam antibiotics Inactivates penicillin in various ways.  Staphylococci produces  In which two are common 4 types of penicillinases(A-D)  Production of Beta-  Hospital strains: type A lactamase penicillinase  Alteration in penicillin  Penicillinase: Production binding protein PBP2a. usually controlled by plasmids, which are transmitted by transduction or conjugation ALTERATION IN PENICILLIN BINDING PROTEIN(PBP2A) & CHANGES IN BACTERIAL SURFACE RECEPTORS:  Reduces binding of beta-lactam antibiotics to cells.  Normally chromosomal in nature  Also extends to cover beta lactamase-resistant penicillins such as methicillin and cloxacillins (MRSA).  MRSA is mediated by the mecA gene  VRSA is mediated by the vamA gene Coagulase negative Staphylococcus: Staphylococcus epidermidis –Commensal on skin –Can cause cystitis –Stitch abscess, artificial heart valves, shunts, intravascular catheters& prosthetic appliances Staphylococcus hemolytic Staphylococcus saprophyticus –UTI in young women  The End Questions???