Streptococcus pneumoniae pneumococus PneumoniaMeningitisbacteraemia

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 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 –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 MeningitisConjunctivitis 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 ( 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 IntermediateResistant –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