1. C H A P T E R © 2014 Pearson Education, Inc. PowerPoint ® Lecture Presentations prepared by Mindy Miller-Kittrell, North Carolina State University Pathogenic Gram-Positive Bacteria 19

2. © 2014 Pearson Education, Inc. Gram-Positive Bacterial Pathogens Stain purple when Gram stained Two major groups based on DNA Low G + C bacteria High G + C bacteria Staphylococcus Normal members of every human's microbiota Can be opportunistic pathogens

3. © 2014 Pearson Education, Inc. Staphylococcus Structure and Physiology Facultative anaerobes Cells occur in grapelike clusters Nonmotile:(not capable of move) Salt-tolerant Tolerate salt on human skin Tolerant of desiccation, radiation, and heat Survive on environmental surfaces

4. © 2014 Pearson Education, Inc. Staphylococcus Structure and Physiology Two species commonly associated with diseases in humans Staphylococcus aureus More virulent strain Variety of conditions depending on site of infection Staphylococcus epidermidis Normal microbiota of human skin Opportunistic infections

5. © 2014 Pearson Education, Inc. Staphylococcus Pathogenicity Infections result when staphylococci breach body's physical barriers Entry of only a few hundred bacteria can result in disease Pathogenicity results from three features 1.Structures that enable it to evade phagocytosis 2.Production of enzymes 3.Production of toxins

6. © 2014 Pearson Education, Inc. Staphylococcus Pathogenicity Structural defenses against phagocytosis Protein A coats the cell surface Inhibits opsonization and the complement cascade Bound coagulase Converts fibrinogen into fibrin molecules Fibrin clots hide the bacteria from phagocytic cells Synthesize polysaccharide slime layers (capsules) Inhibit leukocyte chemotaxis and phagocytosis Facilitate attachment of Staphylococcus to surfaces

7. © 2014 Pearson Education, Inc. Staphylococcus Pathogenicity Enzymes Cell-free coagulase Triggers blood clotting Staphylokinase Dissolves fibrin threads in blood clots Allows S. aureus to free itself from clots Lipases Digest lipids Allow staphylococcus to grow on skin and in oil glands  -lactamase Breaks down penicillin Allows bacteria to survive treatment with  -lactam antimicrobial drugs

8. © 2014 Pearson Education, Inc. Staphylococcus Pathogenicity Toxins Produced by S. aureus and less frequently by S. epidermidis Cytolytic toxins Disrupt the cytoplasmic membrane of a variety of cells Exfoliative toxins Cause skin cells to separate and slough off Toxic-shock syndrome toxin Causes toxic-shock syndrome Enterotoxins Stimulate symptoms associated with food poisoning

9. © 2014 Pearson Education, Inc. Staphylococcus Epidemiology S. epidermidis is ubiquitous on human skin S. aureus primarily found only in moist skin folds Both species grow in the upper respiratory, gastrointestinal, and urogenital tracts of humans Hand washing and aseptic techniques help prevent infections

10. © 2014 Pearson Education, Inc. Staphylococcus Staphylococcal Diseases Noninvasive disease Food poisoning Due to ingestion of enterotoxin-contaminated food Cutaneous diseases Various skin conditions Scalded skin syndrome, impetigo, folliculitis

11. © 2014 Pearson Education, Inc. Figure 19.2 Staphylococcal scalded skin syndrome. Figure 19.3 Impetigo.

12. © 2014 Pearson Education, Inc. Staphylococcus Staphylococcal Diseases Systemic diseases Toxic-shock syndrome (nonstreptococcal) Some Staphylococcus strains produce TSS toxin TSS toxin absorbed into the blood Produces fever, vomiting, rash, low blood pressure

13. © 2014 Pearson Education, Inc. Figure 19.4 Toxic-shock syndrome (TSS).

14. © 2014 Pearson Education, Inc. Staphylococcus Staphylococcal Diseases Systemic diseases Bacteremia Presence of bacteria in the blood Endocarditis Damage to the lining of the heart Pneumonia Inflammation of the lungs Osteomyelitis Inflammation of the bone and bone marrow

15. © 2014 Pearson Education, Inc. Staphylococcus Diagnosis, Treatment, and Prevention Diagnosis Detect Gram-positive bacteria in grapelike arrangements Treatment Methicillin Vancomycin used to treat MRSA infections Prevention Hand antisepsis important to prevent nosocomial infections

16. © 2014 Pearson Education, Inc. Streptococcus Facultative anaerobes Cocci arranged in pairs or chains Often categorized based on Lancefield classification Divided into serotypes based on bacteria's antigens Lancefield groups A and B include the significant human pathogens

17. © 2014 Pearson Education, Inc. Streptococcus Group A Streptococcus: Streptococcus pyogenes Epidemiology Typically infects the pharynx or skin Often causes disease when normal microbiota are depleted Spreads via respiratory droplets

18. © 2014 Pearson Education, Inc. Streptococcus Group A Streptococcus: Streptococcus pyogenes Group A streptococcal diseases Pharyngitis ("strep throat") Inflammation of the pharynx Scarlet fever Can occur following streptococcal pharyngitis infections Chest rash develops that spreads across the body

19. © 2014 Pearson Education, Inc. Pus pockets on tonsils Figure 19.6 Pharyngitis.

20. © 2014 Pearson Education, Inc. Streptococcus Group A Streptococcus: Streptococcus pyogenes Group A streptococcal diseases Streptococcal toxic-shock syndrome Bacteremia that causes severe multisystem infections Can cause organ failure, shock, and death Necrotizing fasciitis Streptococci enter the body and spread along the fascia Secrete enzymes and toxins that destroy tissue

21. © 2014 Pearson Education, Inc. Figure 19.8 Necrotizing fasciitis.

22. © 2014 Pearson Education, Inc. Streptococcus Group A Streptococcus: Streptococcus pyogenes Group A streptococcal diseases Rheumatic fever Complication of untreated streptococcal pharyngitis Inflammation damages the heart valves and muscle Autoimmune response against heart antigens Glomerulonephritis Caused by antibody-bound streptococcal antigens that accumulate in the glomeruli of the kidneys Inflammation causes hypertension and low urine output Adults may suffer irreversible kidney damage

23. © 2014 Pearson Education, Inc. Streptococcus Group A Streptococcus: Streptococcus pyogenes Diagnosis, treatment, and prevention Diagnosis Skin infections diagnosed by the presence of gram-positive bacteria in short chains or pairs Rapid strep test used to diagnose respiratory infections Streptococci in the pharynx are not diagnostic Treatment Penicillin is effective Prevention Antibodies against M protein provide protection

24. © 2014 Pearson Education, Inc. Streptococcus Group B Streptococcus: Streptococcus agalactiae Cocci that form chains Distinguished from group A Streptococcus Group-specific cell wall antigens Smaller zone of beta-hemolysis Resistant to bacitracin

25. © 2014 Pearson Education, Inc. Streptococcus Group B Streptococcus: Streptococcus agalactiae Pathogenicity Often infects newborns without specific antibodies Produces enzymes whose roles are not yet understood Epidemiology Colonizes the gastrointestinal, genital, and urinary tracts Wound infections and childbirth cause most adult infections Newborns often inoculated at birth

26. © 2014 Pearson Education, Inc. Streptococcus Beta-Hemolytic Streptococci Streptococcus equisimilis Causes pharyngitis Streptococcus anginosus Infection produces pus-filled abscesses Penicillin effective against both species

27. © 2014 Pearson Education, Inc. Streptococcus Alpha-Hemolytic Streptococci: The Viridans Group Lack group-specific carbohydrates Many produce a green pigment when grown on blood media Inhabit mouth, pharynx, GI tract, genital tract, and urinary tract Opportunistic pathogens One cause of dental caries and dental plaques If enter the blood can cause meningitis and endocarditis

28. © 2014 Pearson Education, Inc. Figure 19.9 Dental caries.

29. © 2014 Pearson Education, Inc. Streptococcus Streptococcus pneumoniae Cocci that most commonly form pairs Form unpigmented, alpha-hemolytic colonies on blood agar Lacks Lancefield antigens

30. © 2014 Pearson Education, Inc. Capsule Figure 19.10 Streptococcus pneumoniae.

31. © 2014 Pearson Education, Inc. Streptococcus Streptococcus pneumoniae Epidemiology Present in the mouths and pharynges of most humans Causes disease when travel to the lungs Infections occur most often in children and the elderly

32. © 2014 Pearson Education, Inc. Streptococcus Streptococcus pneumoniae Pneumococcal diseases Pneumococcal pneumonia Most common disease caused by S. pneumoniae Sinusitis and otitis media Sometimes occur following viral infections Bacteremia and endocarditis S. pneumoniae can enter the blood through lacerations or tissue damage Pneumococcal meningitis Mortality rate higher than other causes of meningitis

33. © 2014 Pearson Education, Inc. Streptococcus Streptococcus pneumoniae Diagnosis, treatment, and prevention Diagnosis Gram stain of sputum smears Confirmed with Quellung reaction Treatment Penicillin Resistant strains have emerged Prevention Vaccine made from purified capsular material

34. © 2014 Pearson Education, Inc. Enterococcus Previously classified with group D streptococci Reclassified as a separate genus All enterococci live in the intestinal tracts of animals

35. © 2014 Pearson Education, Inc. Enterococcus Structure and Physiology Form short chains and pairs Lack a capsule Two species cause disease in humans E. faecalis E. faecium Pathogenesis, Epidemiology, and Diseases Found in the human colon Rarely pathogenic at this site Can cause disease if introduced into other parts of the body Important cause of nosocomial infections

36. © 2014 Pearson Education, Inc. Enterococcus Diagnosis, Treatment, and Prevention Diagnosis Enterococcus distinguished from S. pneumoniae by its sensitivity to bile Treatment Difficult to treat enterococcal infections Enterococci often resistant to antimicrobials Prevention Prevention is difficult in health care setting Patients often have weakened immune systems Good hygiene and aseptic techniques minimize transmission

37. © 2014 Pearson Education, Inc. Enterococcus Figure 19.11 Enterococcus faecalis in lung tissue.

38. © 2014 Pearson Education, Inc.

39. Bacillus Structure, Physiology, and Pathogenicity Facultative anaerobes Bacilli that occur singly, in pairs, or in chains Form endospores Pathogenic strains produce anthrax toxins Epidemiology Humans contract from infected animals Transmission occurs via one of three routes Inhalation of spores Inoculation of spores through break in the skin Ingestion of spores

40. © 2014 Pearson Education, Inc. Figure 19.12 Bacillus anthracis as it appears in tissue. Bacillus anthracis

41. © 2014 Pearson Education, Inc. Bacillus Disease Bacillus anthracis only causes anthrax Three clinical manifestations Gastrointestinal anthrax Rare in humans Cutaneous anthrax Produces ulcer called an eschar Fatal in 20% of untreated patients Inhalation anthrax Rare in humans Requires inhalation of airborne endospores High mortality rate

42. © 2014 Pearson Education, Inc. Eschar Figure 19.13 Cutaneous anthrax.

43. © 2014 Pearson Education, Inc. Bacillus Diagnosis, Treatment, and Prevention Diagnosis Large, nonmotile, Gram-positive bacilli in lung or skin samples Treatment Many antimicrobials are effective against B. anthracis Prevention Control of disease in animals Effective vaccine available Requires multiple doses and boosters

44. © 2014 Pearson Education, Inc. Clostridium Clostridium perfringens Large, nonmotile, bacillus Clostridium most frequently isolated from clinical specimens

45. © 2014 Pearson Education, Inc. Clostridium Clostridium perfringens Pathogenesis, epidemiology, and disease Produces toxins that can cause irreversible damage to body Grows in the digestive tracts of animals and humans Diseases Food poisoning Abdominal cramps and watery diarrhea Gas gangrene Trauma introduces endospores into body Endospores germinate and cause necrosis

46. © 2014 Pearson Education, Inc. Clostridium Clostridium perfringens Diagnosis, treatment, and prevention Diagnosis Presence of minimum bacterial load in food or feces Appearance of gas gangrene is usually diagnostic Treatment Food poisoning is self-limited Gas gangrene requires removal of dead tissue and administration of antitoxin and penicillin Prevention Refrigeration of foods can reduce cases of food poisoning Proper cleaning of wounds can prevent gas gangrene

47. © 2014 Pearson Education, Inc. Clostridium Clostridium difficile Motile, anaerobic intestinal bacterium Produces two toxins and the enzyme hyaluronidase Pathogenesis, epidemiology, and disease Common member of the intestinal microbiota Opportunistic pathogen in patients taking broad- spectrum antimicrobial drugs

48. © 2014 Pearson Education, Inc. Clostridium Minor infections result in self-limiting explosive diarrhea Serious cases can cause pseudomembranous colitis Sections of the colon wall slough off, causing massive infection by fecal bacteria Diagnosis Isolation of organism from feces Demonstrate the presence of toxins by immunoassay Treatment Discontinue causative antimicrobial drug to resolve minor infections Serious cases treated with antibiotics Prevention Proper hygiene to limit nosocomial infections

49. © 2014 Pearson Education, Inc. Clostridium Clostridium botulinum Anaerobic, endospore-forming, bacillus Common in soil and water Botulism results when the endospores germinate and produce botulism toxins Pathogenesis Botulism toxins C. botulinum strains produce seven distinct toxins Among the deadliest known toxins Bind neurons and prevent muscle contractions

50. © 2014 Pearson Education, Inc. Figure 19.15 How botulism toxin acts at a neuromuscular junction. Neuron Muscle cell Synaptic cleft Cytoplasmic membrane of muscle cell Normal neuromuscular junction Acetylcholine Vesicles with acetylcholine Cytoplasmic membrane of neuron Neuromuscular junction with botulism toxin present Botulism toxin Vesicles with acetylcholine 1 2

51. © 2014 Pearson Education, Inc. Clostridium Clostridium tetani Motile, obligately anaerobic, bacilli with a terminal endospore Ubiquitous in soil, dust, and GI tract of animals and humans Tetanus results when endospores germinate and produce tetanus toxin

52. © 2014 Pearson Education, Inc. Figure 19.16 Cells of Clostridium tetani, with terminal endospores. Endospore

53. © 2014 Pearson Education, Inc. Clostridium Clostridium tetani Pathogenesis Tetanospasmin toxin (tetanus toxin) Released by C. tetani cells when they die Potent neurotoxin Causes continuous muscle contractions

54. © 2014 Pearson Education, Inc. Clostridium Clostridium tetani Disease and epidemiology Initial tightening of the jaw and neck muscles Commonly called lockjaw Spasms and contractions can spread to other muscles Unrelenting contraction of the diaphragm can cause death Most cases occur in less-developed countries Due to inadequate medical care and lack of vaccination Recovery requires growth of new neuronal terminals Mortality rate about 50%

55. © 2014 Pearson Education, Inc. Listeria Listeria monocytogenes Non-endospore-forming bacillus Found in soil, water, mammals, birds, fish, and insects Enters body in contaminated food and drink Grows in macrophages or liver or gallbladder cells Listeria produces no toxins or enzymes Virulence directly related to Listeria's ability to live within cells Can cause meningitis in certain at-risk groups Pregnant women can transmit Listeria to their fetus Cause premature delivery, miscarriage, stillbirth, or meningitis in the newborn

56. © 2014 Pearson Education, Inc. Listeria Diagnosis, Treatment, and Prevention Diagnosis Presence of bacteria in the cerebrospinal fluid of individuals with meningitis Rarely seen in Gram-stained preparations Treatment Ampicillin and an aminoglycoside Prevention Difficult because organism is ubiquitous At-risk individuals should avoid certain foods

57. © 2014 Pearson Education, Inc. Mycoplasmas Smallest free-living microbes Lack cytochromes, enzymes of the Krebs cycle, and cell walls Most have sterols in their cytoplasmic membranes Require various growth factors from a host or supplied in laboratory media Can colonize the mucous membranes of the respiratory and urinary tracts Associated with pneumonia and urinary tract infections Only a few species cause significant human disease

58. © 2014 Pearson Education, Inc. Mycoplasmas Mycoplasma pneumoniae Pathogenesis and epidemiology Attaches to epithelial cells lining the human respiratory tract Removal of mucus impaired, allowing bacteria to colonize Causes primary atypical pneumonia Early symptoms not typical of other types of pneumonia Not usually severe enough to require hospitalization Sometimes called walking pneumonia Spread by nasal secretions among people in close contact Common in children 5 to 15 years old

59. © 2014 Pearson Education, Inc. Figure 19.21 Mycoplasma pneumoniae.

60. © 2014 Pearson Education, Inc. Mycoplasmas Mycoplasma pneumoniae Diagnosis, treatment, and prevention Diagnosis Mycoplasmas are small and difficult to detect Mycoplasmas grow slowly in culture Treatment Macrolides Prevention Patients often infectious without signs or symptoms Prevent with proper hygiene and avoidance of aerosols and contaminated fomites

61. © 2014 Pearson Education, Inc. Corynebacterium Pleomorphic, non-endospore-forming bacteria Ubiquitous on plants and in animals and humans Colonize the skin and respiratory, gastrointestinal, urinary, and genital tracts Divide via snapping division

62. © 2014 Pearson Education, Inc. V-shapes Palisade arrangement Figure 19.22 Gram-stained Corynebacterium diphtheriae.

63. © 2014 Pearson Education, Inc. Corynebacterium Pathogenesis, Epidemiology, and Disease Corynebacterium diphtheriae Causes diphtheria Endemic in poor parts of the world that lack immunization Transmitted from person to person via respiratory droplets or skin contact Diphtheria toxin causes the signs and symptoms of disease Inhibits polypeptide synthesis in eukaryotes Bacteria that do not produce the toxin are not pathogenic Formation of a pseudomembrane can cause suffocation

64. © 2014 Pearson Education, Inc. Corynebacterium Diagnosis, Treatment, and Prevention Diagnosis Initial diagnosis based on presence of a pseudomembrane Elek test used to confirm diagnosis Treatment Administration of antitoxin neutralizes effects of the toxin Penicillin or erythromycin kills the bacterium Surgery may be needed to open a blocked airway Prevention Immunization is the most effective way to prevent diphtheria

65. © 2014 Pearson Education, Inc. Mycobacterium Non-endospore-forming pathogen Cell wall contains a waxy lipid called mycolic acid Results in a number of unique characteristics Slow growth Protection from lysis after phagocytosis Capacity for intracellular growth Resistance to Gram staining, detergents, many antimicrobial drugs, and desiccation

66. © 2014 Pearson Education, Inc. Mycobacterium Tuberculosis Respiratory disease caused by Mycobacterium tuberculosis Cord factor Cell wall component produced by virulent strains of M. tuberculosis Inhibits neutrophil migration and is toxic to mammalian cells

67. © 2014 Pearson Education, Inc. Figure 19.24 Mycobacterium tuberculosis.

68. © 2014 Pearson Education, Inc. Mycobacterium Tuberculosis Pathogenesis and disease Three types of tuberculosis Primary tuberculosis Results from the initial infection with M. tuberculosis Secondary or reactivated tuberculosis Reestablishment of active infection after period of dormancy

69. © 2014 Pearson Education, Inc. Figure 19.25 Development of tuberculosis in the lungs. Respiratory droplets Inhaled respiratory droplets Respiratory bronchiole Alveoli Tubercle Collagen fibers Caseous necrosis Tubercle Alveolus Ruptured tubercle Mycobacterium Bronchiole Blood vessel Beginning of tubercle Bronchiole Macrophage Alveolus Blood vessel Mycobacterium 1 2 3 45 Primary tuberculosis infectionSecondary or reactivated tuberculosis

70. © 2014 Pearson Education, Inc. Mycobacterium Tuberculosis Pathogenesis and disease Three types of tuberculosis Disseminated tuberculosis Results when infection spreads throughout the body Symptoms arise due to complications at the various sites involved Once referred to as "consumption"

71. © 2014 Pearson Education, Inc. Mycobacterium Tuberculosis Epidemiology Cases are declining in the United States Pandemic in other parts of the world Kills almost 2 million people annually Individuals with lowered immunity at greatest risk for infection

72. © 2014 Pearson Education, Inc. Mycobacterium Tuberculosis Diagnosis, treatment, and prevention Diagnosis Tuberculin skin test identifies possible exposure Chest X rays identify individuals with active disease Treatment Common antimicrobials ineffective Combination therapy used for months to treat the disease Prevention Immunization with BCG vaccine where TB is common Efficacy of the vaccine is not clear

73. © 2014 Pearson Education, Inc. Tubercles Figure 19.26 Diagnosis of tuberculosis.

74. © 2014 Pearson Education, Inc. Mycobacterium Leprosy Also referred to as "Hansen's disease" Caused by Mycobacterium leprae Grows best in cooler regions of the human body Bacteria do not grow in cell-free culture Armadillos are the only known host other than humans

75. © 2014 Pearson Education, Inc. Mycobacterium Leprosy Pathogenesis, epidemiology, and disease Two different forms of the disease Tuberculoid leprosy Nonprogressive form of the disease Due to a strong cell-mediated immune response Lepromatus leprosy More virulent form of the disease Due to a weak cell-mediated immune response Cases are becoming relatively rare Transmitted via person-to-person contact or break in the skin

76. © 2014 Pearson Education, Inc. Figure 19.27 Lepromatous leprosy can result in severe deformities.

77. © 2014 Pearson Education, Inc. Mycobacterium Leprosy Diagnosis, treatment, and prevention Diagnosis Based on signs and symptoms of disease Treatment Combination of antimicrobial drugs Lifelong treatment is sometimes needed Prevention Limiting exposure to the pathogen BCG vaccine provides some protection

78. © 2014 Pearson Education, Inc. Mycobacterium Other Mycobacterial Infections Mycobacterium avium-intracellulare Most common mycobacterial infection among AIDS patients in the United States Infections result from ingestion of contaminated food or water Affects almost every organ Results in massive organ failure Treatment is difficult due to the disseminated nature of the infection

79. © 2014 Pearson Education, Inc. Propionibacterium Small, anaerobic rods often found on the skin Propionibacterium acnes Most commonly involved in human infections Causes acne in adolescents and young adults May also be an opportunistic pathogen Many cases require no treatment Antimicrobial drugs help control bacterium

80. © 2014 Pearson Education, Inc. Nocardia and Actinomyces Nocardia asteroides Pathogenesis, epidemiology, and disease Common inhabitant of soils rich in organic matter Produces opportunistic infections in numerous sites Pulmonary infections Develop from inhalation of the bacteria Cutaneous infections Result from introduction of the bacteria into wounds May produce a mycetoma Central nervous system infections Result from spread of bacteria in the blood

81. © 2014 Pearson Education, Inc. Figure 19.29 A Nocardia infection.

82. © 2014 Pearson Education, Inc. Nocardia and Actinomyces Nocardia asteroides Diagnosis, treatment, and prevention Diagnosis Presence of Nocardia in samples is usually diagnostic Treatment Six-week course with sulfonamides Immunocompromised patients have poor prognosis Prevention Avoiding exposure to bacterium in soil

83. © 2014 Pearson Education, Inc. Nocardia and Actinomyces Actinomyces Pathogenesis, epidemiology, and disease Normal microbiota of human mucous membranes Opportunistic infections Occur in the respiratory, gastrointestinal, urinary, and female genital tracts Actinomycosis Bacteria enter through breaks in the mucous membrane Develop abscesses connected by channels in skin or mucous membranes

84. © 2014 Pearson Education, Inc. Figure 19.30 Actinomyces.

85. © 2014 Pearson Education, Inc. Nocardia and Actinomyces Actinomyces Diagnosis, treatment, and prevention Diagnosis Diagnosis difficult Other organisms cause similar symptoms Treatment Surgical removal of infected tissue Administration of penicillin for several months Prevention Good oral hygiene Prophylactic use of antimicrobials if breach of mucous membranes occurs