hematology and medical oncology - acgme
TRANSCRIPT
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Genus: Streptococcus and Enterococcus
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The Streptococci
• Diverse collection of cocci.
• Gram-positive• Chains or pairs• significant pathogens
• Strong fermenters• Facultative anaerobes• Non-motile• Catalase Negative
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Genus: Streptococcus and Enterococcus
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Classification 1
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Genus: Streptococcus and Enterococcus
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Classification 2• The pyogenic group
• The mitis group
• The anginosus group
• The salivarius group
• The bovis group
• The mutans group
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Genus: Streptococcus and Enterococcus
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Haemolytic activity• β-haemolysis
http://medicine.ucsd.edu/NizetLab/streptococcipage/Hemolysis.jpg
• α-haemolysishttp://www.kcom.edu/faculty/chamberlain/Website/lab/idlab/hemo.jpg
• Another useful site:http://www.aic.cuhk.edu.hk/web8/Strep.htm
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Genus: Streptococcus and Enterococcus
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Lancefield Grouping
• Serological classification– Means of distinguishing PYOGENIC Streps
• Differences in cell wall polysaccharides
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Genus: Streptococcus and Enterococcus
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Streptococcus pyogenes
• Lancefield Group A• Most prevalent• Exclusively human pathogens• Infection Types
– Suppurative – Toxin related– Non-suppurative
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Str. pyogenes. pyogenes -- suppurativesuppurative•• nonnon--invasive invasive
–– pharyngitis skin infection, impetigopharyngitis skin infection, impetigo
•• invasive bacteremia invasive bacteremia –– toxic shocktoxic shock--like syndrome like syndrome –– "flesh eating" bacteria"flesh eating" bacteria
•• pyrogenic toxinpyrogenic toxin
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Genus: Streptococcus and Enterococcus
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SuppurativeSuppurative (continued 1)(continued 1)
• Pyrogenic toxin–– superantigensuperantigen–– T cell T cell mitogenmitogen–– activates immune systemactivates immune system
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SuppurativeSuppurative (continued 2)(continued 2)
•• Scarlet feverScarlet fever–– rash rash –– erythrogenic toxinerythrogenic toxin
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Non-suppurative
• rheumatic fever •• inflammatory diseaseinflammatory disease•• life threateninglife threatening•• chronic sequalaechronic sequalae
•• fever fever •• heart heart •• jointsjoints
•• rheumatic NOT rheumatoid arthritisrheumatic NOT rheumatoid arthritis
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Genus: Streptococcus and Enterococcus
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Non-suppurative 2• Rheumatic fever• (penicillin: terminates pharyngitis & decreases
carditis) • Acute glomerulonephritis (immune complex
disease of kidne)• Rheumatic fever –etiology• M protein ( cross-reacts heart myosin;
autoimmunity)• cell wall antigens (poorly digested in vivo persist
indefinitely)
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Genus: Streptococcus and Enterococcus
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Str. pyogenes: Pathogenesis (1)
• Lancefield Group A• Human pathogen• Suppurative infections
– Respiratory tract– Soft tissue infections
(http://www.4um.com/tutorial/icm/softiss.htm)– Toxin associated infections
• Spectrum of infection resembles that of Staph. aureus BUT virulence characteristics DIFFER
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Location of virulence associated factors Pathogenesis (2)
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Virulence factors:Pathogenesis (3)
• Any attributes that are conducive to the process of infection
• adherence, • evasion of the host immune system and • tissue damage
• Variability • Genetic info transfer via “transduction”
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Transduction
www.panspermia.org/transduction.jpg
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Virulence factors: adhesion
• Principal mechanism– F protein===fibronectin
• Adherence
• Entry of the organism INTO the cell
– Lipoteichoic acid
– M protein
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Virulence factors: M protein• Resistance to phagocytosis• Fibril
• Cytoplasmic membrane• Cell wall
• Polymorphism in gene encoding variability• >80 forms
• Strains may have :– More than 1 type on their surface and– M-like
• Bind to host serum proteins
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Genus: Streptococcus and Enterococcus
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Virulence factors: Capsule
• Hyaluronic acid capsule– Some strains
• Severe infections
• Mucoid colonies on blood agar
• Anti-phagocytic effect– Variable significance
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Streptococcus agalactiae• Lancefield Group B• Primary habitat is the human colon; other
areas include– throat– vagina (10-40 %)
• Bovine mastitis
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Genus: Streptococcus and Enterococcus
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Str. agalactiae: Pathogenesis
• virulence factors – haemolysins,– capsule polysaccharide; (9 different types)– C5a peptidase (only the human pathogenic
strains), – hyaluronidase (not all strains) , – various surface proteins
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Str. agalactiae: Pathogenesis 2• CAMP
– Means of lab recognition of Str. Agalactiae
http://gold.aecom.yu.edu/id/micro/camp.htm
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Genus: Streptococcus and Enterococcus
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Str. agalactiae: Features• Infections in Neonates
– Early onset (at or T<12 h of birth)– Late onset (T> 7 days but T<3 months)
• Newborn babies become infected in three ways:– before birth– during birth– after birth
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Genus: Streptococcus and Enterococcus
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Early onset disease• Risk factors for early onset disease include:• Premature delivery;• Multiple births;• Premature rupture of membranes before the onset of
labour;• Prolonged rupture of membranes lasting more than 18
hours before delivery;• Urinary tract infection in mother caused by Group B Strep;• Lack of antibody in mother against type of Group B Strep
carried in birth canal;• Fever in mother during labour;• History of previous newborn with Group B Strep disease.
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Genus: Streptococcus and Enterococcus
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Late onset disease• Bacteraemia alone or in conjunction with other
conditions– purulent meningitis– pneumonia, – septic arthritis,– osteomyelitis – conjunctivitis– sinusitis– otitis media– endocarditis – peritonitis
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Infection in the adult• Pregnancy / recent post partum
– Ascending spread– Abortion, chorioamnionitis,post partum sepsis, – other infections
e.g. pneumonia in the post partum period
• Non pregnant adults– sepsis, pneumonia, soft tissue infections, and
UTI– complicated by bacteraemia.
• Elderly
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Other Pyogenic Streptococci
• http://www.spjc.edu/hec/vettech/VTDE/ATE2639L/Microchart.htm
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Str. suis(Group R streptococcus)
• septicaemia and meningitis in pigs.
• occasionally infect people• Through contaminated pork or infected pigs, and
• cause septicaemia, meningitis, and respiratory tract
infections.
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Genus: Streptococcus and Enterococcus
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Streptococcus pneumoniae• pneumococcus
– oropharyngeal flora of 5-70% of the population– highest isolation rate in children during the
winter months.• diplococcus
• an important pathogen– polysaccharide capsule
• genetically very flexible
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Genus: Streptococcus and Enterococcus
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Streptococcus pneumoniae: Pathogenesis 1
• Capsulehttp://www.indstate.edu/thcme/micro/s-
pneum2.html• Antiphagocytichttp://www.medschool.lsumc.edu/Micr/COU
RSES/DMIP/opson.htmhttp://medtech.cls.msu.edu/ISL/immunology/
opsonize.htm
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Streptococcus pneumoniae: Pathogenesis 2
• IgA1 protease• Pneumolysin
– Neutrophil chemotaxis– Phagocytosis and the respiratory burst
http://www.cellsalive.com/nbt.htm• Autolysin
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Clinical features: pneumonia• Predisposing conditions
• Person-to-person spread is uncommon.
• Possible causes include:– Aspiration into the lower respiratory tract
– Terminal events
– Immune deficiencies
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The Commensal Streptococci:Viridians Streptococci
• Viridans group dominant resident oral flora– Mitis– Salivarius
• Inhibit colonization of many pathogens– Bacteriocins– H2O2
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Viridans streptococci
• ill defined group of species• α- haemolysis on blood agar,• may have a variety or no Lancefield
antigens. • The most common are Str. sanguis, mitis,
mutans and salivarius. • Most are commensals of the mouth and
upper respiratory tract.
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Bacteriocins• http://www.biochem.ucl.ac.uk/bsm/PLASMID/Ba
cteriocins.htm• Agents • Encoded in the genetic material carried by
plasmids• There purpose is to of kill or inhibit closely related
species or even different strains of the same species
• Specific• Survival in an overpopulated environment
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Genus: Streptococcus and Enterococcus
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Mitis group• Str. mitis, Str. oralis, Str. sanguis and Str. gordonii
• Colonize tooth surfaces & mucosal membranes
• May enter the bloodstream
• In healthy individuals, cleared from circulation within 1 h
• Not so with other predisposing factors present
post-streptococcal rheumatic fever• were the primary cause of infective endocarditis
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Mutans group
• Str. mutans and Str. sobrinus
– Exclusively colonize tooth enamel
– Only after eruption
• Lactic acid producers
• may cause subacute bacterial endocarditis.
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Anginosus Group
• Str. anginosus , Str. intermedius & others• regular commensals
– tooth surfaces– gingival crevices.
• isolated from abscesses and other purulent opportunistic infections
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Bovis Group
• Str. Bovis • Various animal species• Human gut• Occasionally causes
– Bacteraemia– Subacute endocarditis
• Associated with colon carcinoma
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Genus: Streptococcus and Enterococcus
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Enterococcus• natural habitat in the human intestines
– E. faecalis – E. faecium
• Associated diseases– Urinary tract infection ( in hospitals, sporadic outbreaks)– Infective endocarditis– Biliary tract infections– Suppurative abdominal lesions– Peritonitis
• Poor prognosis
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On Line Medical Encyclopedia
e.g. Hypogammaglobulinaemia http://www.amershamhealth.com/medcyclopaedia/Volume%20III%201/HYPOGAMMAGLOBULINAEMIA.asp
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In conclusion
• http://www.geocities.com/SouthBeach/Port/3008/strepto.html