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The Gram-Positive Bacteria

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... toxic shock syndrome * S. aureus Skin Lesions Boil or Furuncle Carbuncle * S. aureus Osteomyelitis * S. aureus Staphylococcal scalded skin syndrome ... – PowerPoint PPT presentation

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Title: The Gram-Positive Bacteria


1
(No Transcript)
2
The Gram-Positive Bacteria
Chapter 19
3
The Gram-Positive Bacilli of Medical Importance
4
A reminder Some Gram-positive soil bacteria
are capable of producing endospores.
Bacillus anthracis With central endospores
Clostridium perfringens With subterminal
endospores
Clostridium tetani With terminal endospores
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
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
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
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.
  • The attacks came in two waves of letters with
    Trenton, New Jersey postmarks
  • the first, with postmarks of Sepmtember 18, were
    sent to ABC, NBC, CBS, the New York Post, and the
    National Equiror at American Media Inc.
  • the second, with postmarks of October 9, were
    sent to Senators Daschle and Leahy.

9
Cutaneous anthrax showing the eschar
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
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
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

13
C. perfringens infection
14
C. perfringens wound infection
15
Clostridium perfringens
  • treatment of gangrene
  • debridement of diseased tissue
  • large doses of cephalosporin or penicillin
  • hyperbaric oxygen

Hyperbaric treatment chamber Exposure to
increased oxygen levels inhibits anaerobes and
speeds healing
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

17
C. difficile infection. Lining of the colon
as seen via a sigmoidoscope
Mild
Severe pseudomembranous colitis
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

19
Tetanospasmin (a potent neurotoxin). Toxin
inhibits release of neurotransmitter from neurons
controlling inhibition of skeletal muscle
contraction
20
Patient with Tetanus
Figure 19.17
21
Neonatal tetanus
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 (although GI tract is not
    colonized)

23
Botulism
24
Clostridium botulinum
  • Botox
  • In 2007, almost 4.6 million procedures were
    performed with FDA-approved BOTOX Cosmetic.
  • BOTOX Cosmetic works by temporarily reducing the
    contractions of the muscles that cause the
    persistent frown lines that have develop over
    time.
  • The benefits may last up to 4 months
  • Over 11 million people have used botox

25
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 trimethoprim-sulfamethoxazole
  • Prevention pasteurization cooking

26
Listeria monocytogenes
  • Pathogen isolated from
  • 12 of ground beef
  • 25-30 of chicken/turkey carcasses
  • 6 of luncheon meats
  • also in dairy products

27
Erysipelothrix rhusiopathiae
  • gram-positive rod widely distributed in animals
    the environment
  • primary reservoir tonsils of healthy pigs
  • enters through skin abrasion, multiplies to
    produce erysipeloid, dark red lesions
  • penicillin or erythromycin
  • vaccine for pigs

28
Erysipeloid lesion on hand of animal handler
29
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

30
United States
31
pseudomembrane
32
DiptheriaWhat can happen if you dont vaccinate!
  • 1990s epidemic in former Soviet Union countries.
    In 1993 and 1994, more than 50,000 cases were
    reported during a serious outbreak of diphtheria
    in countries of the former Soviet Union.
    (Contrast US had only 15 total cases between
    1994-2009)
  • 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.

33
Propionibacterium acnes
  • gram-positive rods
  • aerotolerant or anaerobic
  • nontoxigenic
  • common resident of sebaceous glands
  • Causes 85 of acne cases

34
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

35
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
  • Estimated that 1/3 of worlds population is
    infected
  • only 5-10 infected people develop clinical
    disease. (stillabout 2 million people die every
    year)

36
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

37
Granulomatous infection by M. tuberculosis
Tubercule formation
38
Primary Tuberculosis
Figure 19.22a
39
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 (disseminated) TB
  • during secondary TB, bacilli disseminate to
    regional lymph nodes, kidneys, long bones,
    genital tract, brain, meninges Bad News

40
Secondary Tuberculosis
Figure 19.22b
41
Diagnosis
  1. tuberculin testing (Mantoux test)
  2. X rays
  3. direct identification of acid-fast bacilli in
    specimen
  4. cultural isolation and biochemical testing

42
Tuberculin skin test. Tests for exposure. Tests
for hypersensitivity(type IV)
Vaccination causes a positive test resultso test
is only useful in countries that do employ
widespread vaccination
43
Treatment of TB
  • Current US treatment combination of 4
    antibiotics for 2 months.
  • Multi-drug resistant TB treatment much more
    expensive and can go on for 2 years.
  • 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
Directly Observed Therapy (DOT)to assure that
medication is actually taken
45
Mycobacterium leprae
  • Hansens 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
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

47
Leprosy
48
Leprosy
49
Feather test for leprosy. Tickling to determine
sensitivity to touch
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

51
Periodontal infection. Infection works its way to
the surface of the face to rupture and drain
Actinomycosis
52
Nocardiosis
Pulmonary infection that has disseminated to the
skin
53
Lactobacillus
  • Ferment carbohydrates to lactic acid. The
    acidity inhibits many competing bacteria and
    creates an ecological niche where they have the
    advantage.
  • Major inhabitant of the vaginal tract. Not a
    pathogen.
  • Used in production of many foods
  • L. delbrueckii used in yogurt production
  • L. acidophilus used in acidophilus milk production

54
Gram Positive Cocci
Oral streptococci on agar plate
55
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

56
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

57
S. aureus
SEM showing grape-like clusters
58
Enzymes of S. aureus
  • coagulase coagulates plasma and blood produced
    by 97 of human isolates diagnostic
  • hyaluronidase
  • staphylokinase
  • DNase
  • lipases
  • penicillinase

59
S. aureus
Coagulase Test
Catalase Test
60
Toxins of S. aureus
  • hemolysins lyse RBCs a, b, g
  • leukocidin
  • enterotoxins
  • exfoliative toxin
  • toxic shock syndrome toxin

61
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

62
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

63
S. aureus
Skin Lesions
Boil or Furuncle
Carbuncle
64
S. aureus
Osteomyelitis
65
S. aureus
Staphylococcal scalded skin syndrome (SSSS)
Exfoliative toxin
Epidermal shedding/separation
66
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67
Staphylococcus aureus
  • Food Poisoning
  • Food contaminated by handling with bare hands.
    Bacteria grow and produce toxin.
  • Refrigerate food to prevent growth. Heating
    doesnt 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

68
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 1980-198415,000 affected/yr
    with 15 mortality.

69
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70
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.

71
MRSA has become a subject for some intensive
public education efforts
72
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73
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

74
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

75
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

76
Streptococcus
77
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

78
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79
Human streptococcal pathogens
  • S. pyogenes
  • S. agalactiae
  • viridans streptococci
  • S. pneumoniae
  • Enterococcus faecalis

80
b-hemolytic S. pyogenes
  • Group A
  • Most serious streptococcal pathogen
  • Strict parasiteInhabits throat, nasopharynx,
    occasionally skin
  • Produces multiple virulence factors

81
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

82
Pharyngitis and Tonsilitis Strep Throat
Note white pus patches on tonsils
83
Toxic sequelae to Strep throat
http//www.cnn.com/video//video/health/2008/10/22
/tessman.strep.throat.kare
84
Impetigo lesions
Streptococcal skin infections
Erysipelas
85
FLESH-EATING BacteriaNecrotizing fasciitis
Streptococcus pyogenes
86
Rheumatic fever is a possible sequelae to S.
pyogenes infection. Antibodies against the
bacteria may cross-react with host tissue leading
to damage of heart valves
87
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 often screened treated
  • wound and skin infections endocarditis in
    debilitated people

88
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

89
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 butdental or surgical
    procedures facilitate entrance

90
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 may receive prophylactic antibiotics
    before surgery or dental procedures

91
Subacute bacterial endocarditis. Colonization of
heart valve surfaces lead to layers of fibrin and
bacteria called vegetations
92
Viridans group
SEM of Plaque
  • S. mutans produces slime layers that adhere to
    teeth, basis for plaque
  • involved in dental caries

93
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

94
Gram stain of sputum from pneumonia patient
showing diplococci
95
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

96
S. pneumoniae
97
Middle ear infections (otitis media)
98
S. pneumoniae
Buldging eardrum (otitis media)
Normal eardrum
99
Healthy eardrum
Ruptured/torn eardrum
Tubes
Tubes are usually left in for 8 to 18 months and
most often fall out on their own
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