Bacteria PDF - Immunology

Bacteria Wednesday, July 17, 2024 8:05 PM Gram positive - peptidoglycan; stains purple - Cocci, bacilli Gram negative - outer membrane; stains pink - Cocci, bacilli Staphylococcus Staphylococcus aureus Gram positive spherical cocci, facultative anaerobe Golden staph - appears gold on agar...

Bacteria Wednesday, July 17, 2024 8:05 PM Gram positive - peptidoglycan; stains purple - Cocci, bacilli Gram negative - outer membrane; stains pink - Cocci, bacilli Staphylococcus Staphylococcus aureus Gram positive spherical cocci, facultative anaerobe Golden staph - appears gold on agar plate due to antioxidant capacity Optimum growth temp of 37C; tolerates high salt and extremes of pH Virulence factors - Enzymes: ○ coagulase (diagnostic factor - only species of staph that produce coagulase) ○ Hyaluronidase, staphylokinase, DNase, lipases, penicillinase - Toxins: hemolysins, leukocidin, enterotoxin, exfoliative toxin, toxic shock syndrome toxin Epidemiology and pathogenesis - Readily isolated from fomites - Carriage on skin, anterior nares, nasopharynx, intestine Clinical disease - Localized cutaneous infections - invade skin via wounds, follicles, or glands ○ Folliculitis - superficial inflammation of hair follicle ○ Furuncle (boil) - inflammation of hair follicle or sebaceous gland ○ Carbuncle - larger and deeper lesion ○ Impetigo - bubble like swellings the that break and peel away - Systemic infections ○ Osteomyelitis - infection establishes in metaphysis; abscess forms ○ Bacteremia - primary origin is bacteria from another infected site or medical devices; endocarditis possible - Toxigenic disease ○ Food intoxication - ingestion of heat stable enterotoxins ○ Staphylococcal scalded skin syndrome - toxin induces reddening, blisters, desquamation of the epidermis ○ Toxic shock syndrome - toxemia leading to shock and organ failure Treatment - >95% produce penicillinase and are resistant to penicillin and ampicillin - MSRA - methicillin resistant S. aureus - some strains are resistant to all major drug groups except vancomycin - Abscesses require surgical drainage - Systemic infections require lengthy antimicrobial therapy Other staphylococci Coagulase negative - nosocomial, opportunistic infections - S epidermidis - lives on skin, mucous membranes, bacteremia, UTI - S hominis - lives around apocrine sweat glands - S capitis - lives in scalp, face, external eat; all may cause wound infections via broken skin - S saprophyticus - infrequently lives on skin, intestine, vagina; UTI Streptococcus Characteristics - Gram positive ovoid cocci, facultative anaerobes - Sensitive to drying, heat, disinfectants Classified based on hemolysis, Lancefield group (only associated with beta hemolytic groups) - B hemolysis - full clearing of blood cells, carbohydrate antigen present in cell wall - a hemolysis - partial hemolysis Immunology 第 1 頁  - a hemolysis - partial hemolysis - y hemolysis - non hemolysis Streptococcus pyogenes Group A streptococci, beta hemolytic Inhibit throat, nasopharynx, skin Cause of many important infections Cell wall constituents - Fimbriae - attachment to host cell - M protein - inhibits regulator of complement - Capsule - polysaccharide layer protecting against phagocytosis - C5a protease Exotoxins - streptolysins and erythrogenic toxins Enzymes - streptokinase, hyaluronidase, DNase Transmission - contact, droplets, food, fomites Portal of entry - skin, pharynx Systemic infections and progressive sequelae can occur if untreated Skin infections - Impetigo (pyoderma) - superficial skin infection (contagious crust associated with crowding, poor hygiene, breaks in the skin) - Erysipelas - associated with breaks in skin and spreads to dermis; raised rash and inflammation Necrotizing fascitis (flesh eating disease) - Typically caused by S. pyogenes; associated with breaks in the skin, invasion and multiplication in the fasscia - Damage to conenctive tissue and muscle - Diabetes and immunocompromised most at risk - Low risk: healthy individual and proper wound care Throat infection - Pharyngitis (strep throat) - involve uvula Systemic infections - Scarlet fever - strain of S pyogenes carrying a prophage that encodes a erythrogenic toxin - Sepsis, pneumonia, streptococcal toxic shock syndrome Long term complications - Rheumatic fever - follows overt of subclinical pharyngitis in children; carditis with extensive valve damage possible, arthritis, chorea, fever (develops 2-4 weeks after throat infection) - Acute glomerulonephritis Streptococcus pneumoniae Alpha hemolytic; normal flora of upper resp tract Classic cause of pneumonia, ear infections, systemic infections (meningitis, bacteremia) Virulence factors - capsules Gains access to middle ear via Eustachian tube Treatment and prevention - S pyogenes - penicillin - S pneumonia - penicillin; vaccines available for high risk individuals Enterococcus Similar to streptococci, normal flora of the large intestine (cause of opportunistic infections - UTI and bacteremia) Important species - enterococcus fecalis and enterococcus fecium Resistant to many antibiotics - treated with vancomycin but emergence of vancomycin resistant enterococcus (VRE) Neisseria Gram negative cocci, aerobe/facultative anaerobe Normal flora of mucus membranes Neisseria gonorrhea Virulence factors - Fimbriae - aids attachment to mucosal epithelium - IgA protease - breaks down immunoglobulin present on mucosal surfaces Strictly a human pathogen; top 5 STD Doesn't survive more than 1-2 hours on fomites Clinical disease Immunology 第 2 頁 Clinical disease - Male - urethritis - Female - cervicitis Neisseria meningitidis Virulence factors - Fimbriae, capsule, IgA proteases, endotoxin Normal flora of nasopharynx; spread via saliva and resp secretions Invasion particularly following influenza - viral infection damages epithelial cells Children and teenagers at greater risk Clinical disease - Meningitis - bacteria enters bloodstream -> crosses BBB -> permeates the meninges and grows in the CSF ○ Rapid onset: neurological symptoms, endotoxin causes hemorrhage and shock, can be fatal Treatment and prevention - Treated with IV penicillin, cephalosporin - Prophylactic treatment of family members, medical personnel, or children in close contact with the patient - Primary vaccine contains specific purified capsular antigens Clostridium Gram positive anaerobic spore forming rods Clostridium perfringens Cause soft tissue, would infections, food poisoning Spores found in soil, human skin, intestine Predisposing factors - puncture wounds, surgical incisions, diabetic ulcers Virulence factors - Alpha toxin - RBC rupture, edema, tissue destruction - Collagenase - Hyaluronidase - DNase Gas gangrene - requires damaged/dead tissue and anaerobic conditions that stimulate spore germination, vegetative growth, release of exotoxins - Fermentation of muscle carbohydrates results in gas formation and further tissue destruction Treatment - Immediate cleansing of dirty wounds - Debridement of diseased tissue - Treat with cephalosporin or penicillin (no vaccines available) - Hyperbaric oxygen therapy - increase O2 pressure on tissue because perfringens are strict anaerobes Clostridium tetani Cause of tetanus; resident of soil, GIT of animals Tetanospasmin - neurotoxin causes paralysis by binding to motor nerve endings; blocks release of neurotransmitter; uncontrollable muscle contraction Death due to paralysis of resp muscles Treatment - Antitoxin therapy with human tetanus Ig; inactivates circulating toxin (not bound) - Treat with penicillin or tetracycline and muscle relaxants - Vaccine available; booster needed every 10 years Clostridium botulinum Cause of botulism - intoxication associated with inadequate food preservation - Botulin toxin blocks release of Ach necessary for muscle contraction Commonly inhabits soil and water - spores present on food when gathered and processed Treatment and prevention - Determine presence of toxin in food - Administer antitoxin, cardiac, and resp support - Infectious botulism treated with penicillin Bacillus Bacillus anthracis Immunology 第 3 頁 Bacillus anthracis Gram positive aerobic spore forming robs Virulence factors - capsule and exotoxins Cause of anthrax - Cutaneous - spores enter through skin, black sore, least dangerous - Pulmonary - inhalation of spores - Gastrointestinal - ingested spores Treatment - penicillin, tetracycline, ciprofloxacin Vaccines - Live spores and toxoid to protect livestock - Purified toxoid - high risk occupations and military personnel Listeria monocytogenes Gram positive non spore forming rods (coccobacilli to long filaments) Possess flagella (1-4) but lack capsules Virulence - can induce phagocytosis and replicated in the cytoplasm Epidemiology and pathology - Can contaminate foods and grow during refrigeration - Listeriosis - most cases associated with dairy products, poultry, meat - Immunocompromised patients, fetus, neonates - affects brain and meninges Treatment - Ampicillin and Bactrim (trimethoprim/ sulfamethoxazole) - Prevention - pasteurization and cooking Corynebacterium diphtheriae Gram positive non spore forming rods (irregular shaped) Most cases occur in non-immunized children Acquired via resp droplets from carriers or infected individuals Pathology - Local infection - upper resp tract inflammation - sore throat, nausea, vomiting, swollen lymph nodes; pseudo membrane formation can cause asphyxiation - Diptherotoxin production and toxemia - target organs (heart and nerves) Treatment - Penicillin or erythromycin - Prevention - toxoid vaccine series and boosters Aerobic gram negative bacilli Non spore forming Pseudomonas aeruginosa (opportunistic) Intestinal resident; resistant to soap, disinfectants, drugs Frequent contaminant of ventilators, IV solutions, anesthesia, equipment Common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis - Complications - pneumonia, UTI, abscesses, otitis - Systemic infection - bacteremia, endocarditis Virulence - cell surface polysaccharides, toxins, biofilm formation Resistant to many antibiotics Bordetella pertussis (human pathogen) - coccobacillus Cause of pertussis whooping cough Transmission - direct contact, aerosol droplets of fomite Virulence factors - adhesions, toxins to invade ciliated epithelial cells (stop cilia beating) Vaccine - acellular vaccine (toxoid and other antigens) Legionella pneumophila (human pathogen) Colonize aquatic environments Inhalation via aerosols - invades and multiplies in macrophages Cause of legionellosis (pneumonia) - fever, cough, diarrhea, abdominal pain Treatment - azithromycin Enteric pathogens (Enterobacteriaceae) Non spore forming, gram negative rods (facultative anaerobes) Most frequent cause of diarrhea through enterotoxins Virulence - complex surface antigens (flagella, capsule, somatic E.coli (lactose fermenter) - opportunistic Immunology 第 4 頁 E.coli (lactose fermenter) - opportunistic Enterotoxigenic - severe diarrhea Enteroinvasive - bloody diarrhea (invades cells causing inflammatory disease - colitis) Enteropathogenic - wasting form of infantile diarrhea Enterohemorrhagic - hemorrhagic syndrome and kidney disease Uropathic - UTI Klebsiella pneumoniae (lactose fermenter) - opportunistic Produces a large capsule, normal flora of resp tract Opportunistic infections - nosocomial pneumonia, meningitis, bacteremia, wound infections, UTI Salmonella (non-lactose fermenter) - true pathogen Salmonellosis - uncooked foods Nausea, vomiting, diarrhea S.enteritis (gastroenteritis), S.typhi (typhoid fever) - treat with chloramphenicol or bactrim Hemophilus Small gram negative rods (pleomorphic) Fastidious growth requirements (will not grow on blood agar) Hemophilus influenza (opportunistic pathogen) - meningitis, otitis media, sinusitis, pneumonia Subunit vaccine (Hib) - low incidence since introduction Gram negative bacilli (irregular shaped) Vibrio - comma shaped rods; single polar flagellum Introduced into humans via contaminated food and water - gastroenteritis, open wounds (cellular, sepsis) Vibrio cholerae - causative agent of cholera - Produces AB exotoxin -> secretion of Cl- into lumen of small intestine -> profuse watery diarrhea -> rapid dehydration and electrolyte loss - Treatment - oral rehydration Campylobacter Spiral shaped or curved rods; single polar flagellum Introduced via contaminated food and water - main cause of bacterial gastroenteritis Produces exotoxin that stimulates secretory diarrhea, headache, fever, abdominal pain Treatment - rehydration and electrolytes Helicobacter Spiral shaped rods, several polar flagella Mycobacteria Bacteria with mycolic acid in cell wall - undetectable via gram stain so use acid fast stain Mycobacterium tuberculosis Transmitted by inhalation of aerosols Inhalation of infected droplets: 1. Innate defense system of lung clear bacilli - no infection 2. Latent TB - infection failed to clear bacilli -> bacilli proliferate inside alveolar macrophages -> macrophages produce chemokines and cytokines which attract other phagocytic cells -> formation of a nodular granuloma -> uncontrolled bacterial replication (can reach local lymph nodes) -> effective cell mediated immune response and control the infection -> infection but is contained by immune response thus asymptomatic 3. Primary TB - innate system failed to clear bacilli (infection and symptomatic) 4. Secondary (reactivation) TB - had an infection and was dormant, but now developed symptoms (typically btw 1-2 years of infection) Unchecked bacterial proliferation leads to hematogenous spread and disseminated TB - Pulmonary TB - fever, constitutional symptoms (weight loss, fatigue, night sweats), pleuritic or retrosternal pain, cough, hemoptysis, pleural effusions - CNS TB - rupture of cortical or meningeal tubercle into subarachnoid space causes TB meningitis; can form tuberculoma and subsequent mass effects - Miliary TB - typically chronic or subacute; organ dysfunction (infected lung) - Acute miliary TB - can be fulminant (septic shock, acute resp distress syndrome) Screening - Tuberculin skin test - inject small amount of purified protein from dead TB - Interferon gamma release assay blood test - measures immune response to TB - CXR, sputum smear and acid fast stain with follow up culture + PCR Immunology 第 5 頁  - CXR, sputum smear and acid fast stain with follow up culture + PCR - If culture TB, want to test for resistance (MDR TB) Mycobacterium ulcerans Causes buruli flesh eating ulcers - most common mycobacterial disease after TB Typically beings as painless, non-tender nodule or papule -> slowly forms ulcer Spread by mosquito Diagnose - collect a swab from unroofed lesion for staining, PCR, culture Mycoplasma Bacteria without a cell wall - will not show on gram stain Highly pleomorphic - pseudo coccoidal Mycoplasma pneumoniae - atypical pneumonia One of the most common bacterial causes of URTI, acute bronchitis, CAP Transmitted via resp droplets Spirochetes Spiral shaped gram negative bacteria; flagella gives corkscrew motility Borrelia burgdorferi - lyme disease Transmitted by Ixodes tick - erythema migrans (tick bite) Stage 1 (early localized) - develop erythema migrans Stage 2 (early disseminated) - carditis, CNS complications (ex. meninges), MSK complications (migratory arthralgias) Stage 3 (late persistent) - MSK/ CNS complications, cutaneous disease Immunology 第 6 頁