Transcript Streptococcus pneumoniae pneumococus Pneumonia Meningitis

Streptococcus pneumoniae
pneumococus
Pneumonia
Meningitis
bacteraemia
Description
Gram-positive diplococci (in pairs)
Encapsulated ovoid or lanceolate coccus
Non-motile
Fastidious (enriched media)
– Blood or chocolate agar
– 5-10 % CO2
Alpha haemolysis + draughtsman appearance
Some strains are mucoid
Soluble in bile
Optochin sensitive
Pathogenesis
Virulence factors
– Capsular polysaccharide
The major factor
84 serotypes
Both antigenic and type specific
Antiphagocytic
Serotype 3 , 7 are most virulent
90% of cases of bacteraemic pneumococcal
pneumonia and meningitis are caused by 23
serotypes
Quellung reaction , india ink
– Pneumolysin
Membrane damaging toxin
Carrier rate
– Oropharyngeal flora of 5 – 70% of the
population
– Significance in respiratory infection
Predisposing factors
– Aspiration of upper airway secretions ( endogenous )
– No person-person spread
– Disturbed consciousness , general anaesthesia ,
convulsions , CVA , epilepsy , head trauma
– Prior LRT. VIRAL infection
– Preexisting respiratory diseases , smoking
Chronic bronchitis , bronchogenic malignancy
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Chronic heart disease
Chronic renal disease ( nephrotic syndrome )
Chronic liver disease ( cirrhosis)
Diabetes mellitus
Old age , (extreme of age )
Malnutrition , alcoholism
Specific deficiencies in host defence
– Hypogamaglobulinaemia
– Asplenia , hypospenism ( tuftsin )
– Homozygous sickle cell disease
– Coeliac disease
– Multiple myeloma , leukaemia , lymphomas
– Neutropenia
– HIV
Relative or absolute deficiency of opsonic
antibody or inadequate manufacture of type
specific antibody
Diseases
Respiratory tract infections
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Lobar pneumonia ( commonest cause of CAP )
Empyema
Otitis media (6 months – 3 yrs )
Mastoiditis
Sinusitis
Acute exacerbation of chronic bronchitis
Meningitis
Conjunctivitis
Peritonitis ( primary )
Bacteraemia ( 15 % of pneumonia )
septicaemia
Clinical feature
Lobar pneumonia
– Sudden onset
– Fever
– rigor
– Cough , rusty sputum
– Pleural pain
– Signs of lobar consolidation
– Polymorphonuclear leucocytosis
– Empyema , pericarditis
Meningitis
– The most virulent pathogen of meningitis
– Mortality ( 20% )
– Primary
– Complicate infections at other site ( lung )
– Bacteraemia usually coexists
– Bimodal incidence ( < 3 yr - > 45 yr )
Mortality
Age (> 65 yr )
Preexisting disease
Bacteraemia
Serotype 3 , 7
Laboratory diagnosis
Specimen
– Sputum
– CSF
– Swabs
– Pus
– Blood culture
– Aspirate
Microscopy
– Gram stained smear
Gram-positive diplococci + pus cells
culture
Blood agar , chocolate agar + 10 % CO2
identification
Alph-haemolytic colonies
Optochin sensitive
Bile soluble
Sensitivity testing
– Penicillin
– susceptible
Sensitive
– Nonsusceptible
Intermediate
Resistant
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Ampicillin , amoxicillin
Erythromycin
Ceftriaxone , cefuroxime
Clindamycin
Fluroquinolones
tetracyclines
Vancomycin
Treatment
Meningitis
– Parenteral ceftriaxone + vancomycin
pneumonia
– Outpatients
Erythromycin
Amoxacillin – clavulanic acid
Cefuroxime or ceftriaxone (IV) + oral b- lactam
– Inpatients
Parenteral cefuroxime or ceftriaxone
Prevention
23 polysaccharide vaccine
– Not effective in children < 2 yrs
– >65 yrs
– Functional or anatomical asplenia
– SCD
7-valent – protein- conjugated vaccine
– Children < 3 yrs