Streptococcus Pneumoniae
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More Specific Terms
Introduction
- Commonly carried in the oropharyngeal area.
Epidemiology
- peak incidence in the winter & spring
- carrier rates as high as 70% or higher [4]
- penicillin-resistant pneumococci associated with beta- lactam antibiotic use [4]
- infection most common in infants & elderly
- risk factors:
Pathology
-
-
- may initially be normal
- later may show classic lobar pneumonia
- leukocytosis of 10,000-30,000/ mm3 is common
- sputum may be rust colored or blood-streaked
- pleurisy/ pleural effusion is common
- cavitation is rare
- bacteremia & sepsis, especially in the elderly
- mortality 20-30%
- fever in 70%
- respiratory distress in 50%
- altered mental status in 50%
- volume depletion in 50%
- meningitis - mortality 20%
- Streptococcus pneumoniae may increase susceptibility to viral pneumonia [5]
-
Genetics
- M-phenotype produces an efflux pump resulting in resistance to:
-
- 11% in 1995, 20% in 1999
- sensitivity to clindamycin persists
- coresistance to other antibiotics is common
- penicillin (81%), cefotaxime (60%), Bactrim (88%)
- most M- phenotypes sensitive to fluoroquinolones
Laboratory
- Gram positive cocci in pairs & chains.
- disk diffusion test with oxacillin predicts susceptibility to penicillin:
- some isolates resistant on disk diffusion will be sensitive by standard broth MIC testing
- grows in 18-24 hours on ordinary blood agar incubated at 37 degrees in 5-10% CO2
- colonies are alpha hemolytic & heterogenous in appearance
- may be identified by sensitivity to optochin
Management
- ( antimicrobial therapy)
- uncomplicated pneumonia treated as outpatient:
- procaine PCN G 600,000 units IM, followed by PCN V 250-500 mg PO every 6 hours for 7-10 days
- amoxicillin 500 mg PO TID
- penicillin allergy
- seriously ill patients:
- PCN G 1-2 million units IV every 4 hours
- erythromycin 500 mg PO or IV every 6 hours if PCN allergy
- levofloxacin
- vancomycin 1 g IV every 12 hours if PCN allergy or PCN or multi-drug resistant organism (all strains sensitive to vancomycin)
- 2 drugs may be better that one for sepsis [6]
- resistance to penicillin
- arises via alterations in penicillin-binding protein(s)
- 50% of intermediate resistant strains are also resistant to ceftazidime & ceftizoxime
- most intermediate resistant strains are susceptible to ceftriaxone & cefotaxime
- most strains susceptible to respiratory fluoroquinolones
- vancomycin or linezolid [2]
More General Terms
Additional Terms
- pneumococcal congugate vaccine (Prevnar, Prevnar 13, PCV7)
- pneumococcal vaccine
- pneumonia (PNA)
- recurrent invasive pneumococcal disease
References
- Manual of Medical Therapeutics, 28th edition, Ewald & McKenzie (eds) Little, Brown & Co, 1995, pg 301
- Medical Knowledge Self Assessment Program (MKSAP) 11, 15, American College of Physicians, Philadelphia 1998, 2009
- Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 796
- Journal Watch 22(4):29, 2002 Nasrin et al, BMJ 324:28, 2002
- Journal Watch 24(17):138, 2004 Madhi SA, Klugman KP, The Vaccine Trialist Group. A role for Streptococcus pneumoniae in virus-associated pneumonia. Nat Med. 2004 Aug;10(8):811-3. Epub 2004 Jul 11. PMID: [1]
- Journal Watch 24(18):147, 2004 Baddour LM, Yu VL, Klugman KP, Feldman C, Ortqvist A, Rello J, Morris AJ, Luna CM, Snydman DR, Ko WC, Chedid MB, Hui DS, Andremont A, Chiou CC; International Pneumococcal Study Group. Combination antibiotic therapy lowers mortality among severely ill patients with pneumococcal bacteremia. Am J Respir Crit Care Med. 2004 Aug 15;170(4):440-4. Epub 2004 Jun 07. PMID: [2]
- Pneumococcal Pneumonia [3]
