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GRAM POSITIVE BACTERIA

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Scarlet fever. Pyoderma - erysipelas. Necrotising fascitis. Puerperal sepsis ... Acute rheumatic fever. Acute glomerulonephritis. Streptococci. Pathogenicity factors ... – PowerPoint PPT presentation

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Title: GRAM POSITIVE BACTERIA


1
GRAM POSITIVE BACTERIA
  • Classification
  • Systematic
  • morphology and staining behavior
  • structure of murein of cell wall
  • metabolic properties
  • DNA homologies
  • antigenic similarities

2
2094
3
Gram positive cocci
  • Aerobic / Facultatively anaerobic
  • Micrococcaciae
  • Staphylococcus spp.
  • Streptococcus spp., Enterococcus spp.,
    Lactococcus spp.
  • Leuconostoc spp, Pediococcus, spp, Gemella spp.,
    Aerococcus spp..
  • Anaerobic
  • e.g. Peptococcaceae
  • Peptococcus spp.
  • Peptostreptococcus spp.

4
Gram positive bacilli
  • Aerobic
  • Aerobic
  • Bacillaceae e.g. Bacillus anthracis
  • Corynebacteriaceae e.g. Corynebacteria
    diphtheriae
  • Lactobacillaceae e.g Lactobacillus acidophilus
  • Other e.g. Listeria monocytogenes, Erysipelothrix
    spp.
  • Anaerobic / Microaerophilic
  • Bacillaceae e.g. Clostridium perfringens
  • Actinomycetaceae e.g. Actinomyces

5
Staphylococci
  • Gram positive cocci in clusters
  • Aerobic/facultatively anaerobic
  • Catalase positive
  • Coagulase enzyme - clots plasma
  • S. aureus
  • Coagulase negative staphylococci e.g.
  • S. epidermidis
  • S. haemolyticus

6
S. aureus
  • Pathogenicity factors
  • Capsule polysaccharide
  • Protein A, Peptidoglycan, Clumping factor
  • Coagulase
  • Haemolysins, Leukocidin, Staphylokinase,
    Protease, Nuclease
  • B-lactamase
  • Epidermolytic toxins
  • Enterotoxins
  • Exotoxins e.g. TSST1

7
S. aureus
  • Diseases
  • Non-toxin mediated
  • Abscess
  • Furuncles/carbuncles
  • Wound infections
  • Cellulitis
  • Bacteraemia
  • Osteomyelitis/Endocarditis/Pneumonia
  • Toxin-mediated
  • Acute staphylococcal enterocolitis
  • Staphylococcal scalded skin syndrome
  • Toxic shock syndrome

8
Coagulase negative staphylococci
  • Normal skin / mucous membrane flora
  • Non-pathogenic in normal host
  • Pathogenic in immunocompromised host
  • adherence to plastic material
  • central lines
  • artificial heart valves
  • endoprosthesis etc.

9
Streptococci
  • Gram positive cocci in chains
  • Catalase enzyme - negative
  • Classified on basis of haemolysis
  • ?-haemolysis
  • Streptococcus pneumoniae
  • viridans streptococci
  • ?-haemolysis
  • Lancefield group A, B, C, D, E, F, G
  • cell wall C-polysaccharide
  • non-haemolysis

10
Streptococcus pyogenes
  • Group A ? -haemolytic streptococcus
  • Small colonies after 24 hours incubation
  • Identified using slide agglutination / latex
    antigen detection kits

11
Streptococcus pyogenes
  • Diseases
  • By invasion
  • Pharyngitis, tonsillitis, peritonsillar abscess
  • Sinusitis, otitis media
  • Pneumonia
  • Scarlet fever
  • Pyoderma - erysipelas
  • Necrotising fascitis
  • Puerperal sepsis
  • Long term immunological
  • Acute rheumatic fever
  • Acute glomerulonephritis

12
Streptococci
  • Pathogenicity factors
  • Capsule
  • C carbohydrate
  • Lipoteichoic acid
  • peptidoglycan
  • M-proteins (group A), T-proteins, R-proteins
  • Exotoxins and enzymes

13
Streptococcus agalactiae
  • Group B ? -haemolytic streptococcus
  • Diseases
  • Early neonatal infection
  • Late neonatal infection
  • Adult disease
  • wound infection, sepsis, meningitis, urinary
    tract infection

14
Enterococcus spp.
  • Group D ? -haemolytic streptococcus
  • Diseases
  • Urinary tract infection
  • Endocarditis
  • Wound infections (mixed)
  • Peritonitis

15
Streptococcus pneumonia
  • Gram positive diplococci
  • ?-haemolytic
  • Autolysis - depressed central colonies, Optochin
    sensitive, Bile soluble
  • Diseases
  • Lobar pneumonia
  • Meningitis
  • Bacteraemia
  • Sinusitis, otitis media, conjunctivitis

16
Viridans streptococci
  • S. mutans, S. salivarius, S. angiosus, S. sanguis
    etc.
  • Numerous genospecies
  • ?-haemolytic
  • Diseases
  • tooth decay
  • oropharyngeal infection
  • endocarditis
  • septicaemia in immunocompromised

17
Anaerobic GPC
  • Peptococcaceae
  • Peptococcus spp.
  • Peptostreptococcus spp
  • Diseases
  • wound infection
  • abscess formation
  • tooth decay

18
Gram positive bacilli
  • Corynebacteria
  • Gram positive bacillus
  • Obligate pathogens
  • C. diphtheriae
  • Clinical manifestations produced by exotoxin
  • inhibits protein synthesis
  • Local vs systemic effects (cardiac/neurological)
  • Clinical diagnosis
  • Rapid treatment

19
Other coryneforms
  • C. ulcerans, C. pseudotuberculosis etc
  • Local effects
  • Diphtheroids
  • Opportunistic

20
Listeria monocytogenes
  • Non-spore forming Gram positive bacillus
  • Haemolytic, cryophilic
  • Diseases
  • Food borne outbreaks
  • Pregnant women
  • Neonatal infection
  • Elderly / immunocompromised

21
Bacillaceae
  • Gram positive bacillus with endospores
  • Aerobic
  • Catalase positive
  • Bacillus spp.
  • B. anthracis - toxin composed of 3 proteins
  • B. cereus - enterotoxins

22
Clostridium spp.
  • C. tetani - tetanus
  • swarming, obligate anaerobe
  • produce toxins (metalloproteinase)
  • degrades synaptobrevin - prevents transmitter
    release in inhibitory cells of CNS
  • irreversible event
  • Clinical diagnosis - laboratory diagnosis too late

23
Clostridium spp.
  • C. botulinum - botulism
  • produces toxin (metalloproteinase)
  • targets the peripheral neuromuscular junction and
    autonomic synapses
  • classically causes acute cranial neuropathy in
    association with descending weakness

24
Clostridium spp.
  • C. perfringens
  • non-motile, boxcar appearance on gram staining
  • produces a number of exo-toxins
  • Diseases
  • gas gangrene
  • food poisoning
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