* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Gram Positive Bacteria
Survey
Document related concepts
Traveler's diarrhea wikipedia , lookup
Sociality and disease transmission wikipedia , lookup
Transmission (medicine) wikipedia , lookup
Triclocarban wikipedia , lookup
Anaerobic infection wikipedia , lookup
Neglected tropical diseases wikipedia , lookup
Gastroenteritis wikipedia , lookup
Onchocerciasis wikipedia , lookup
Globalization and disease wikipedia , lookup
Urinary tract infection wikipedia , lookup
Infection control wikipedia , lookup
African trypanosomiasis wikipedia , lookup
Germ theory of disease wikipedia , lookup
Neonatal infection wikipedia , lookup
Staphylococcus aureus wikipedia , lookup
Transcript
. Staphylococci are gram positive cocci, Occur in grape like clusters, In Greek; staphyle - Bunch of grapes Kokkus - Berry CLASSIFICATION: A) Based on coagulase production: 1. Coagulase positive: Eg- S. aureus 2. Coagulase negative: Eg- S. epidermidis S. saprophyticus B) Based on pathogenicity: 1. Common pathogen: Eg- S. aureus 2. Opportunistic pathogens: Eg- S. epidermidis S. saprophyticus 3. Non pathogen: Eg- S. homonis STAPHYLOCOCCUS AUREUS MORPHOLOGY: These are spherical cocci. Approximately 1μm in diameter. Arranged characteristically in grape like clusters. They are non motile and non sporing. A few strains possess capsules. CULTURE: Media used :i) Non selective media: Nutrient agar, Blood agar, MacConkey’s agar. ii) Selective media: Salt-milk agar, Ludlam’s medium Cultural Characteristics: i) On nutrient agar- The colonies are large, circular, convex, smooth, shiny, opaque and easily emulsifiable. Most strains produce golden yellow pigments. ii) On MacConkey’s agar- The colonies are small & pink in colour. iii) On blood agar- Most strains produce βhaemolytic colonies. Biochemical reactions: 1) Catalase test- Positive. 2) Coagulase testi) Slide coagulase test- Positive. ii) Tube coagulase test- Positive. SLIDE COAGULASE TEST TUBE COAGULASE TEST PATHOGENICITY: Source of infection: A) Exogenous: patients or carriers B) Endogenous: From colonized site Mode of transmission: A) Contact: direct or indirect( through fomites) B) Inhalation of air borne droplets Disease: Diseases produced by Staphylococcus aureus is studied under 2 groups: A) Infections B) Intoxications A) INFECTIONS: Mechanism of pathogenesis: Cocci gain access to damaged skin, mucosal or tissue site Colonize by adhering to cells or extracellular matrix Evade the host defense mechanisms and multiply Cause tissue damage Common Staphylococcal infections are: 1) Skin and soft tissue: Folliculitis, furuncle (boil), carbuncle, styes, abscess, wound infections, impetigo, paronychia and less often cellulitis. Folliculitis Folliculitis Furuncle (boil) Carbuncle Styes Abscess Impetigo Wound infection Paronychia Cellulitis 2) Musculoskeletal: Osteomyelitis, arthritis, bursitis, pyomyositis. osteomyelitis 3) Respiratory: Tonsillitis, pharyngitis, sinusitis, otitis, bronchopneumonia, lung abscess, empyema, rarely pneumonia. 4) Central nervous system: Abscess, meningitis, intracranial thrombophlebitis. 5) Endovascular: Bacteremia, septicemia, pyemia, endocarditis. Endocarditis 6) Urinary: Urinary tract infection. B) INTOXICATIOINS: The disease is caused by the bacterial exotoxins, which are produced either in the infected host or preformed in vitro. There are 3 types1. 2. 3. Food poisoning Toxic shock syndrome Staphylococcal scalded skin syndrome 1) Food poisoning: Enterotoxin is responsible for manifestations of staphylococcal food poisoning. Eight types of enterotoxin are currently known, named A, B, C1-3, D, E, and H. It usually occurs when 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 diarrhoea. The illness is usually self limited, with recovery in a day or so. 2) 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 fatal multisystem disease presenting with fever, hypotension, myalgia, vomiting, diarrhoea, mucosal hyperemia and erythematous rash which desquamates subsequently. 2 types of STSS known: i) Menstrual associated STSS: Here colonization of S.aureus occurs in the vagina of menstruating woman who uses highly absorbent vaginal tampons. ii) Non menstrual associated STSS: Here colonization of S.aureus occurs in other sites like surgical wound. 3) Staphylococcal scalded skin syndrome (SSSS): Exfoliative toxin produced by S.aureus is responsible for this. It is a skin disease in which outer layer of epidermis gets separated from the underlying tissues. Types of SSSS: Severe form In new born Milder form - Ritter’s disease - Pemphigus neonatorum In older patients - Toxic epidermal - Bullous necrolysis impetigo Ritter’s disease Pemphigus neonatorum Toxic epidermal necrolysis Bullous impetigo LAB DIAGNOSIS: Specimens collected: Depends on the type of infection. Suppurative lesion- Pus, Respiratory infection- Sputum, Bacteremia & septicemia- Blood, Food poisoning- Feces, vomit & the remains of suspected food, For the detection of carriers- Nasal swab. Methods of examination: I) Direct microscopy: Direct microscopy with Gram stained smear is useful in case of pus, where cocci in clusters are seen. This is of no value for specimen like sputum where mixed flora are normally present. II) Culture: a) Media used: b) Cultural Characteristics: c) Gram staining: Smears are examined from the culture plate and reveals Gram positive cocci(1μm in diameter) arranged in grape like clusters. d) Biochemical reactions: III) Antibiotic sensitivity tests done as a guide to treatment. IV) Bacteriophage typing is done for epidemiological purposes. V) Serological tests are not useful. TREATMENT: Drug resistance is common. Benzyl penicillin is the most effective antibiotic, if the strain is sensitive. Cloxacillin or Methicillin is used against beta-lactamase producing strains. Methicillin Resistant Staphylococcus aureus (MRSA) strains have become common. Vancomycin is used in treatment of infections with MRSA strains. EPIDEMIOLOGY: Staphylococci are primary parasites of human beings and animals. Hospital infections caused by staphylococci deserve special attention because of their frequency & they are caused by strains resistant to various antibiotics. Staphylococci are the common cause of postoperative wound infection and other hospital cross infections. PREVENTION: Isolation & treatment of MRSA patients. Detection of carriers among hospital staff, their isolation & treatment. Avoid indiscriminate usage of antibiotics. Coagulase Negative Staphylococci( CoNS ): Two species of coagulase negative Staphylococci can cause human infections- 1. Staphylococcus epidermidis 2. Staphylococcus saprophyticus S. Epidermidis: It is a common cause of stitch abscesses. It has predilection for growth on implanted foreign bodies such as artificial valves, shunts, intravascular catheters and prosthetic appliances leading to bacteraemia. In persons with structural abnormalities of urinary tract, it can cause cystitis. Endocarditis may be caused, particularly in drug addicts. Streptococcal Diseases Streptococcus pyogenes Streptococcus pyogenes Pyogenes means pus producing One of the most important pathogens Gram positive cocci in chains Lancefield Serological Group A Beta Hemolytic on blood agar Gram Stain of S. pyogenes Hemolysis on Blood Agar Plates Alpha hemolysis-organism excretes hemolysins which partially break down rbc (incomplete hemolysis) thus a greenish zone appears around colony. S. pneumoniae Beta hemolysis-organisms excretes potent hemoysins which completely lyse rbc (complete hemolysis) thus a clear zone appears around colony. S. pyogenes S.pyogenes S. pneumonia Beta hemolysis Alpha hemolysis Diseases caused by S. pyogenes Strep throat Impetigo Erysipelas Cellulitis Invasive Strep A infections Necrotizing fasciitis Myositis Toxic shock-like syndrome Erysipelas Acute infection and imflammation of the dermal layer of skin. Painful red patches which enlarge and thicken Treatment -penicillin or erythromycin Erysipelas Strep Throat Most common of all Strep diseases Spread by saliva or nasal secretions Incubation period 2-4 days Sore throat, slight fever (101) Important to treat immediately to avoid post strep diseases Diagnosis and treatment of Strep Throat Tell tale symptoms are slight fever associated with sore throat and visual of pus in back of throat Quick diagnostic tests (Molecular) available but must be confirmed by throat swab and growth on blood agar (beta hemolysis) Diagnosis and treatment of Strep Throat If the strain of S. pyogenes is lysogenic for a particular phage which expresses an erythrogenic toxin the result is Scarlet fever Rash appears and characteristic is the strawberry colored tongue Strawberry Tongue Treatment of Strep Penicillin G or Erythromycin are drugs of choice Although the disease is self-limiting it is important to treat immediately to avoid post strep complications Poststreptococcal diseases Rheumatic Fever-autoimmune disease involving heart valves,joints, nervous system. Follows a strep throat Acute glomerulonehritis or Bright’s Diseaseinflamatory disease of renal glomeruli and structures involved in blood filter of kidney. Due to deposition of Ag/Ab complexes Rheumatic Fever Most common cause of permanent heart valve damage in children Exact cause not yet known but there appears to be some antibody cross reactivity between the cell wall of S. pyogenes and heart muscle Rheumatic Fever Diagnosis is based on symptoms and is difficult Occurs most frequently between ages of 6 and 15 US it is about 0.05% of pop having strep infections 100x more frequent in tropical countries Rheumatic Fever Treatment is via salicylates (aspirin derivatives) and corticosteroids to decrease inflammation and fever. Glomerular Nephritis Diagnosis based on history of Strep throat and clinical findings. Symptoms include fever, malaise,edema, hypertension and blood or protein in urine Occurs in 0.5% of those having strep throat. Glomerular Nephritis Treatment and Recovery Penicillin or erythromycin to eradicate and residual strep infection 80-90% of cases recover with bed rest lasting for months Kidney damage in the remainder is often permanent resulting in chronic glomerular nephritis Streptococcus Pneumonia Caused by infection with Streptococcus pneumoniae (Pneumococci) Gram positive, alpha hemolytic, not of lancefield serotype A Often part of normal flora of respiratory track and becomes infective once hosts resistance is lowered. Classified as an endogenous infection. Strep Pneumonia Strep Pneumonia S. pneumoniae Alpha hemolysis Strep pneumonia Predisposing factors: upper respiratory viral infection, diabetes, alcoholism 60-80% of all pneumonias Strep Pneumonia Cause of strep pneumonia Primary virulence factor is the capsular polysaccharide which protects the organism against phagocytosis Pathogenesis is due to rapid growth of bacteria in alveolar spaces Symptoms of Strep Pneumonia Onset abrupt Chest pains Chills Labored breathing Diagnosis of Strep pneumonia Chest Xray Culture and staining Biochemical tests of isolated organism Treatment of Strep Pneumonia Typically treated with Penicillin G cefotaxime, oflaxacin or for those allergic to penicillins can be treated with erythromycin or tetracycline Pneumococcal vaccine (Pneumovax 23 or Pnuimmune 23) is available for the elderly THANK YOU