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33 Cards in this Set
- Front
- Back
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Commensal Neisseria
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Nasopharyngeal carriage is common
Primary diagonostic issue is distinguishing these from pathogens |
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Neisseria: Physiology and Structure
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Gram-negative diplococci
Nutritionally fastidious Best growth in microaerophilic (high CO2) conditions Many outer membrane proteins Antigenic variation Structure is typical of a gram-negative bacterium “Rough” endotoxin lacking O antigen polymer Endotoxin is primary initiator of inflammation |
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Neisseria gonorrhoeae: Pathogenesis and immunity
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Portal of entry
-Contact with mucous exudates from infected people -Sexual activity -Conjunctivitis in very young children What role does immunity play? -Antigenic heterogeneity: little cross protection, reinfection is common -Lipooligosaccharide (LOS) endotoxin is primary immunogen -Carbohydrate, poor memory -Protein based vaccines under study Virulence factors -Adherence factors -Inflammatory mediators |
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Neisseria gonorrhoeae: Epidemiology
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One of the most common sexually transmitted diseases
-Second only to chlamydia in number of reported cases/year -310,000 new infections reported in 2004 US: decline from 1975 (468/100,000) to 1997 (122.5/100,000) -Essentially unchanged thereafter (131/100,000) -Incidence is directly proportional to sexual activity -Rates of acquisition: ~50% per exposure for women ~20% per exposure for men -Antibiotic resistant strains are common |
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Gonococcus: Clinical Presentation
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Males: urethral discharge with pus, painful urination, occasionally presents as epididymitis
Females: Can have discharge, esp. bleeding after sex, often asymptomatic, long term damage includes infertility, PID, scarring of Fallopian tubes and ectopic pregnancy Neonates: opthalimic infections Other presentations: pharyngitis, anorectal infection, vaginitis in prepubescent girls |
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Neisseria gonorrhoeae: Laboratory Diagnosis
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Appropriate specimen is crucial
-urethral exudate or cervical smear Can be confused with Neisseria normal flora Definitive diagnosis: -bacterial culture on selective media - modified Thayer Martin -immunofluorescent tests -nucleic acid based tests |
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Gonococcus: Treatment, prevention, and control
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Antibiotic therapy:
-resistance to penicillin and other b-lactams is widespread -fluoroquinolone resistance common in some groups -Azithromycin is currently most commonly used treatment Prevention: -decrease sexual contacts -preventative opthalmic treatment Control: -public health management and reporting |
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Neisseria meningitidis: Pathogenesis and Immunity
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Pathogenesis:
-asymptomatic carriage (nasopharynx) in 1-20% of pop. -can cross blood brain barrier -capsule is primary virulence factor: antiphagocytic, prevents complement -protein adhesins/invasins -IgA protease Immunity -capsular antibodies are major protective determinant -elderly and young don't make anti-carb antibody -t-cell independent (no memory) |
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Meningococcus: Epidemiology
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Major cause of bacterial meningitis and septicemia
At risk groups: stress and communal housing Recurrent infections might be immunocompromised Most common in Asia and sub Saharan Africa |
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Meningococcus: Clinical Diseases
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Pneumonia often precedes systemic spread
Meningitis: Severe headache, fever Sepsis: petechia or purpura on trunk and/or legs |
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Meningococcus: Laboratory Diagnosis
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Sample is crucial
Isolation of Gram neg diplococci from CSF or blood is definitive Isolation from sputum is not (could be commensal Neisseria) |
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Meningococcus: Prevention and Treatment
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Polyvalent vaccine:
-capsular polysaccharide -t cell independent response -poor memory Prophylactic treatment -penicillin or cephalosporins Treatment accompanied with corticosteroid therapy |
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Haeomophilus influenzae: Physiology and Structure
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Gram negative bacillus
-short rods to long filamentous Nutritionally fastidious -requires hemin and NAD -chocolate agar -satellite growth on blood agar |
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Haemophilus influenzae: Chronic infections
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otitis, chronic bronchitis, sinusitis
-host clearance defects -sample sputum -normal flora may have significance (etiologic agents are normal flora) |
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Haemophilus influenzae: Acute infections
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Meningitis, epiglottitis
-encapsulated bacteria -normal flora do not have significance but can obscure diagnosis |
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Haemophilus influenzae: Systemic infections pathogenisis
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Encapsulated strains
Respiratory portal of entry -colonizes nasopharynx, bacteriocins kill off other bacteria -sometimes present as URT infection prior to systemic -crosses blood brain barrier or enters bloodstream |
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Haemophilus influenzae: Systemic infections immunity
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Polysaccharide capsule
-major virulence determinant -protects from complement and phagocytosis -elderly and very young don't make anti-capsular antibody |
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Encapsulated Haemophilus influenzae: Epidemiology
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Serotype b is major pathogen
Hib conjugate vaccine -capsular polysaccharide linked to protein carrier -improves t cell help -greater memory and affinity maturation of antibodies Hib eliminated carraige and dissease caused by serotype b |
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Haemophilus influenzae: Systemic infections clinical diseases
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Meningitis, acute epiglottitis, sepsis
Affect children <5 Unvaccinated at risk |
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Encapsulated Haemophilus influenzae: Laboratory Diagnosis
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Source of sample crucial
-sputum not as meaningful (commensal strains) -Blood or CSF: significant Serotyping |
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Encapsulated Haemophilus influenzae: Prevention and treatment
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Hib conjugate vaccine
Broad spectrum antibiotics: Cephalosporins |
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Opportunistic Haemophilus influenzae infections: Pathogenesis and immunity
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Caused by nontypeable (unencapsulated) strains
-localized to airways -NOT systemic Innate immunity contains during normal carriage |
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Opportunistic Haemophilus influenzae infections: Epidemiology and Clinical Disease
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Benign carriage is virtually universal
Otitis media: >90% children within first 3 yrs -middle ear Chronic bronchitis -associated with COPD Secondary pneumonia -bacterial infection following viral infection |
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Nontypeable Haemophilus influenzae infections: Laboratory diagnosis
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Isolation of organism from sputum
-not always diagnostic (sometimes patients are carriers) Middle ear fluid |
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Nontypeable Haemophilus influenzae infections: Treatment, prevention, control
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Antibiotics
-b lactam resistance increasing -tympanocentesis No vaccine Children: breast feed Avoid factors that compromise clearance |
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Haemophilus ducreyi: Physiology and structure
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Gram negative rod
Fastidious and slow growing Colonies cause pitting in agar plates STD Causes chancroid -large pus filled lesion |
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Haemophilus ducreyi: Pathogenesis and immunity
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Entry via skin
-mucous exudates from infected people -sexual activity -self transmission to other site Virulence -cytotoxin -painful necrotic lesions -swelling and pain in lymph nodes -can be asymptomatic in women No evidence for natural immunity |
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Haemophilus ducreyi: Epidemiology
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Rare in US
More common in underdeveloped countries Cofactor in HIV transmission |
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Haemophilus ducreyi: clinical diseases
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Chancroid
-soft necrotic lesion -must be differentiated from syphillus and herpes -swelling and pain in regional lymph nodes -can be asymptomatic in women |
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Haemophilus ducreyi: Laboratory diagnosis
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Based on gram stain of pus from lesion
Bicycle chain appearance Req special growth medium No standard nucleic acid based test |
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Chancroid: Prevention, treatment, and control
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Humans only reservoir
Sexual transmission Antibiotics -azithromycin, ceftriaxone, ciprofloxacin, erythromycin Large lymph nodes need draining by needle or local surgery Public health reporting |
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Haemophilus aegyptius
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Subspecies of NTHi
Causes conjunctivitis -some cause brazilian purpuric fever |
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HACEK bacteria
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Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, Kingella
Normal oral flora -peridontal infection -bite infections -endocarditis |
