The Gram-Positive Bacteria

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The Gram-Positive Bacteria

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1. The Gram-Positive Bacteria

2. The Gram-Positive Bacilli of Medical Importance

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5. 5 Bacillus gram-positive, endospore-forming, motile rods mostly saprobic aerobic & catalase positive versatile in degrading complex macromolecules source of antibiotics primary habitat is soil 2 species of medical importance Bacillus anthracis Bacillus cereus

6. 6 Bacillus anthracis large, block shaped rods central spores that develop under all conditions except in the living body virulence factors – capsule & exotoxins 3 types of anthrax Cutaneous – spores enter through skin, black sore- eschar; least dangerous Pulmonary –inhalation of spores Gastrointestinal – ingested spores treated with penicillin or tetracycline vaccine – toxoid 6X over 1.5 years; annual boosters dead livestock burned/chemically decontaminated before burial to prevent soil contamination

7. 7 Bacillus anthracis Biological warfare threat. Letter attacks of 2001 Resulted in only 22 cases of anthrax and five deaths Great disruption and concern More than 32,000 people who may have come into contact with the letters were given prophylactic antibiotics.

8. 8 Anthrax- Domestic Bioterrorism Starting one week after the 9/11/2001 attack letters containing weaponized anhtrax were sent to media offices and to Democratic Senators Tom Daschle and Patrick Leahy -- the two individuals expected to resist passage of the USA PATRIOT ACT.

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10. 10 Bacillus cereus common airborne & dustborne grows in foods, spores survive cooking & reheating ingestion of toxin-containing food causes nausea, vomiting, abdominal cramps & diarrhea; 24 hour duration no treatment spores abundant in the environment

11. 11 Clostridium gram-positive, spore-forming rods anaerobic & catalase negative over 120 species oval or spherical spores produced only under anaerobic conditions synthesize organic acids & alcohols (useful for some biotechnology application) & exotoxins cause wound & tissue infections & food intoxications

12. 12 Clostridium perfringens causes gas gangrene in damaged or dead tissues 2nd most common cause of food poisoning, worldwide virulence factors toxins – alpha toxin – causes RBC rupture, edema & tissue destruction collagenase hyaluronidase DNase

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15. 15 Clostridium perfringens treatment of gangrene – debridement of diseased tissue large doses of cephalosporin or penicillin hyperbaric oxygen

16. 16 Clostridium difficile normal resident of colon, in low numbers causes antibiotic-associated colitis treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow produces entertoxins that damage intestine major cause of diarrhea in hospitals

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18. 18 Clostridium tetani common resident of soil & GI tracts of animals causes tetanus or lockjaw, a neuromuscular disease spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, & crushed body parts tetanospasmin – neurotoxin causes paralysis vaccine booster needed every 10 years

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20. Patient with Tetanus

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22. 22 Clostridium botulinum Causes 3 diseases food poisoning – (an intoxication) spores are in soil, may contaminate vegetables; improper canning does not kill spores & they germinate in the can producing botulinum toxin toxin causes paralysis by preventing release of acetylcholine infant botulism – caused by ingested spores that germinate in the body & release toxin wound botulism – spores enter wound & cause food poisoning symptoms

23. 23 Listeria monocytogenes non-spore-forming gram-positive primary reservoir is soil & water can contaminate foods & grow during refrigeration Most cases are from contaminated dairy products, poultry and meat Disease is often mild/subclinical …may have fever, diarrhea Listerosis in immunocompromised patients, fetuses & neonates affects brain & meninges 20% death rate ampicillin & trimethoprimsulfamethoxazole Prevention – pasteurization & cooking

24. 24 Listeria monocytogenes Pathogen isolated from: 12 % of ground beef 25-30% of chicken/turkey carcasses 6% of luncheon meats also in dairy products

25. 25 Erysipelothrix rhusiopathiae gram-positive rod widely distributed in animals & the environment primary reservoir – tonsils of healthy pigs enters through skin abrasion, multiples to produce erysipeloid, dark red lesions penicillin or erythromycin vaccine for pigs

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27. 27 Corynbacterium diptheriae gram-positive irregular bacilli (pleiomorphic) produce catalase possess mycolic acids & a unique type of peptidoglycan 2 stages of disease local infection –upper respiratory tract diptherotoxin production & toxemia pseudomembrane formation can cause asphyxiation

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31. 31 Diptheria 1990s epidemic in former Soviet Union countries. Reduced vaccination programs resulted in greatly reduced “herd immunity” Multitude of susceptible persons allowed spread in the community. Most cases are in children aged 1-10 in crowded settings.

32. 32 Propionibacterium acnes gram-positive rods aerotolerant or anaerobic nontoxigenic common resident of sebaceous glands causes acne

33. 33 Mycobacteria gram-positive irregular bacilli acid-fast staining strict aerobes produce catalase possess mycolic acids & a unique type of peptidoglycan do not form capsules, flagella or spores grow slowly Mycobacterium tuberculosis Mycobacterium leprae

34. 34 Mycobacterium tuberculosis produces no exotoxins or enzymes that contribute to infectiousness contain complex waxes & other substances that prevent destruction by lysosomes of macrophages transmitted by airborne respiratory droplets only 5% infected people develop clinical disease

35. 35 Primary TB infectious dose 10 cells phagocytosed by alveolar macrophages & multiply intracellularly after 3-4 weeks immune system attacks, forming tubercles, granulomas consisting of a central core containing bacilli surrounded by WBCs

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37. Primary Tuberculosis

38. 38 Secondary TB reactivation of bacilli tubercles expand & drain into the bronchial tubes & upper respiratory tract gradually patient experiences more severe symptoms violent coughing, greenish or bloody sputum, fever, anorexia, weight loss, fatigue untreated 60% mortality rate Extrapulmonary TB during secondary TB, bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain, meninges = Bad News

39. Secondary Tuberculosis

40. 40 Diagnosis tuberculin testing (Mantoux test) X rays direct identification of acid-fast bacilli in specimen cultural isolation and biochemical testing

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43. 43 Treatment of TB 6-24 months of at least 2 drugs from a list of 11 one pill regimen called Rifater (isoniazid, rifampin, pyrazinamide) vaccine based on attenuated bacilli Calmet-Guerin (BCG) strain of M. bovis used in other countries (not U.S.) Success rate of vaccination ~80% in children and 20-50% in adults.

44. 44 Directly Observed Therapy (DOT) …to assure that medication is actually taken

45. 45 Mycobacterium leprae Hansen’s bacillus strict parasite – has not been grown on artificial media or tissue culture slowest growing of all species multiplies within host cells in large packets called globi causes leprosy, a chronic disease that begins in the skin & mucous membranes & progresses into nerves

46. 46 leprosy endemic regions throughout the world spread through direct inoculation from leprotics 2 forms tuberculoid – superficial infection without skin disfigurement which damages nerves and causes loss of pain perception lepromatous – a deeply nodular infection that causes severe disfigurement of the face & extremities treatment by long-term combined therapy

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50. 50 Actinomycetes Genera Actinomyces & Nocardia are nonmotile filamentous bacteria related to mycobacteria may cause chronic infection of skin and soft tissues Actinomyces sp – responsible for diseases of the oral cavity & intestines Nocardia brasiliensis causes pulmonary disease similar to TB

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53. Gram Positive Cocci

54. 54 General characteristics of the Staphylococci Spherical cells arranged in irregular clusters Gram positive Common inhabitant of the skin & mucous membranes Lack spores and flagella May have capsules numerous species

55. 55 Staphylococcus aureus grows in large, round, opaque colonies optimum temperature of 37oC facultative anaerobe withstands high salt, extremes in pH, & high temperatures produces many virulence factors

56. 56 S. aureus

57. 57 Enzymes of S. aureus coagulase – coagulates plasma and blood; produced by 97% of human isolates; diagnostic hyaluronidase staphylokinase DNase lipases penicillinase

58. 58 Toxins of S. aureus hemolysins – lyse RBCs; a, b, g leukocidin enterotoxins exfoliative toxin toxic shock syndrome toxin

59. 59 S. aureus Present in most environments frequented by humans Readily isolated from fomites Carriage rate for healthy adults is 20-60% Carriage is mostly in anterior nares, skin, nasopharynx, intestine

60. 60 S. aureus diseases Ranges from localized to systemic localized -abscess, folliculitis, furuncle, carbuncle, impetigo systemic – osteomyelitis, bacteremia toxigenic disease – food intoxication, scalded skin syndrome, toxic shock syndrome

61. 61 S. aureus

62. 62 S. aureus

63. 63 S. aureus

64. Staphylococcus aureus Food Poisoning Food contaminated by handling with bare hands. Bacteria grow and produce toxin. Refrigerate food to prevent growth. Heating doesn’t always destroy toxin. Symptoms usually start within 1-6 hours after eating contaminated food (usually gone in a day) Symptoms include: diarrhea, vomiting, nausea, cramps

65. Staphylococcus aureus Toxic Shock Syndrome (TSS) First linked to use of ultra-absorbent tampons that bound Mg ions and created a favorable environment for increased colonization and growth of vaginal S. aureus and increased TSS toxin production. Toxin enters bloodstream and causes fever, vomiting organ damage and potential fatality. Height of problem 1980-1984…15,000 affected/yr with 15% mortality.

66. SuperBug ? MRSA: Methicillin Resistant Staphylococcus aureus A strain of staph that is highly resistant to broad-spectrum antibiotics. Once found almost exclusively in hospital settings the bacteria is now showing up in the wider community People can be colonized by the bacteria (skin and nose primarily) and be healthy but act as carriers to spread the microbe. It is thought that perhaps 25-30% of people may harbor S.aureus.

69. MRSA-2 A CDC survey completed recently suggests that in 2005 there were ~ 94,000 cases of MRSA in the US and that perhaps 19,000 people died. (A higher rate than AIDS in the US) 85% of the cases were in hospitals, nursing homes etc. But many are concerned about the large number of infections acquired in normal community environments. Spread may be by hands (direct contact) or from contaminated surfaces. Infections range from an inconsequential skin lesion to a fatal septicemia or pneumonia

70. 70 S. aureus

71. 71 Other Staphylococci S. epidermidis – lives on skin & mucous membranes; endocarditis, bacteremia, UTI S. hominis – lives around apocrine sweat glands S. capitis – live on scalp, face, external ear All 3 may cause wound infections S. saprophyticus – infrequently lives on skin, intestine, vagina; UTI

72. 72 Streptococci Gram-positive spherical/ovoid cocci arranged in long chains Non-spore-forming, nonmotile Can form capsules & slime layers Facultative anaerobes Do not form catalase Most parasitic forms are fastidious & require enriched media Small, nonpigmented colonies numerous species

73. 73 Streptococcus

74. 74 Streptococci Lancefield classification system based on cell wall Ag – 14 groups (A,B,C,….) Another classification system is based on hemolysis reactions b-hemolysis – A,B,C,G & some D strains a –hemolysis – S. pneumoniae & others collectively called viridans

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76. 76 Human streptococcal pathogens S. pyogenes S. agalactiae viridans streptococci S. pneumoniae Enterococcus faecalis

77. 77 b-hemolytic S. pyogenes Group A Most serious streptococcal pathogen Strict parasite…Inhabits throat, nasopharynx, occasionally skin Produces C-carbohydrates, M-protein (fimbrae), streptokinase, hyaluronidase, DNase, hemolysins (streptolysin O (SLO), streptolysin S (SLS)), pyogenic (erythrogenic) toxin

78. 78 S. pyogenes Humans only reservoir Transmission – contact, droplets, food, fomites Skin infections –pyoderma, impetigo, erysipelas Systemic infections – strep throat, pharyngitis, scarlet fever Sequelae -rheumatic fever, glomerulonephritis

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80. 80 Toxic sequelae to Strep throat

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82. 82 FLESH-EATING Bacteria Necrotizing fasciitis

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84. 84 Group B: S. agalactiae Regularly resides in human vagina, pharynx & large intestine can be transferred to infant during delivery & cause severe infection Most prevalent cause of neonatal pneumonia, sepsis, & meningitis 15,000 infections & 5,000 deaths in US Pregnant women should be screened & treated wound and skin infections & endocarditis in debilitated people

85. 85 Enterococcus faecalis, & E. faecium Normal colonists of human large intestine Cause opportunistic urinary, wound, and skin infections, particularly in debilitated persons Enterococcus …Genus related to streptococci and so studied together

86. 86 Viridans group a-hemolytic Large complex group Most numerous & widespread residents of the oral cavity & also found in nasopharynx, genital tract, skin Not very invasive but…dental or surgical procedures facilitate entrance

87. 87 Viridans group Bacteremia, meningitis, abdominal infection, tooth abscesses Most serious infection – subacute endocarditis – blood-borne bacteria settle & grow on heart lining or valves Persons with preexisting heart disease are at high risk & receive prophylactic antibiotics before surgery or dental procedures

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89. 89 Viridans group S. mutans produces slime layers that adhere to teeth, basis for plaque involved in dental caries

90. 90 S. pneumoniae Causes 60-70% of all bacterial pneumonias arranged in pairs and short chains All pathogenic strains form large capsules – major virulence factor Causes pneumonia & otitis media Vaccine available for high risk people

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92. 92 S. pneumoniae 5-50% of all people carry it as normal flora in pharynx Very delicate, does not survive long outside of its habitat Pneumonia occurs when cells are aspirated into the lungs of susceptible individuals Pneumococci multiply & induce an overwhelming inflammatory response Treated with penicillin

93. 93 S. pneumoniae

94. 94 S. pneumoniae

95. 95 S. pneumoniae

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