Streptococcus pneumoniae pneumococus

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

• 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
• 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

• 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
• 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

• 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

• 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

• Sensitivity testing
• Penicillin
• susceptible
• Sensitive
• Nonsusceptible
• Intermediate
• Resistant
• 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