Streptococcus pneumoniae infection
Streptococcus pneumoniae infection Microchapters
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Synonyms and Keywords: Strep pnumoniae; Strep pneumoniae infection
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive bacterium. It is a diplococcus, alpha-hemolytic member of the Streptococcus genus. During the 19th century pneumonia was heavily associated with this pathogen. S. pneumoniae is known to be the cause of various different infections apart from pneumonia including endocarditis, meningitis, pericarditis, brain abscess, otitis media, osteomyelitis, acute sinusitis, septic arthritis, peritonitis, and cellulitis. In children as well as adults, S. pneumoniae is the most common cause of otitis media as well as bacterial meningitis. Pneumonia caused by S. pneumoniae is usually found at the extremes of the age (in old or very young individuals). Streptococcus viridans also belongs to the family of alpha hemolytic bacteria but can e distinguished from S. pneumoniae by an optochin test. Streptococcus viridans are found to be insensitive to optochin where as S. pneumoniae are found to be optochin sensitive. The most potent virulence factor of S. pneumoniae is its polysaccharide capsule. Up to 91 various types of capsules have been discovered; each of these differ in virulence, drug resistance, prevalence, and distribution.
Streptococcus pneumoniae infections may be classified as follows:
|Streptococcus Pneumoniae Infection|
|Community Acquired Pneumonia||Endocarditis||Sinusitis||Bronchitis||Meningitis|
Depending on the nature of infection, an appropriate sample is collected from the infected area for laboratory identification. Commonly found
- Pneumococci are gram positive, cocci, seen in pairs or chains.
- When cultured on blood agar plates with added optochin antibiotic disk, pneumococci show alpha-hemolytic colonies and a clear zone of inhibition around the disk meaning pneumococci are sensitive to the antibiotic.
- Pneumococci are also bile soluble.
- Similar to other streptococci, pneumococci are catalase negative.
- Quellung test to identify specific capsular polysaccharides may also be done.
- An ASO titre of >200 units is significant.
- S. pneumoniae is, in general, optochin sensitive, although optochin resistance has been observed.
- Atromentin and leucomelone possess antibacterial activity, inhibiting the enzyme enoyl-acyl carrier protein reductase, (essential for the biosynthesis of fatty acids) in S. pneumoniae.
- Streptococcus pneumonia treatment
- 1. Lung (Community-acquired pneumonia)
- 1.1 Penicillin sensitive (minimum inhibitory concentration < 2 mcg/ml)
- Preferred regimen: Penicillin G 5-24 MU IV in equally divided doses q4-6h, Amoxicillin 1 g PO tid (+/- macrolide)
- Alternative regimen: Macrolides (Azithromycin (IV) 500 mg IV qd for at least 2 days followed by 500 mg PO qd 7-10 days or Clarithromycin extended-release tablets 1000 mg PO qd for 7 days) and oral Cephalosporins-Cefpodoxime 200 mg PO bd, (Cefprozil 500 mg PO bd, Cefditoren 400 mg PO bd, Cefdinir 300 mg PO bd), OR parenteral Cephalosporins-Ceftriaxone 2 g IV q24h (or Cefotaxime 1-2 g IV q6-8h), Clindamycin 600-1200 mg IV/IM q6-12h, do not give single IM doses > 600 mg; IV infusion rates should not exceed 30 mg/min , Doxycycline 100 mg PO bd, respiratory flouroquniolones.
- Preferred regimen: Ceftriaxone 2 g IV q24h (or Cefotaxime 1-2 g IV q6-8h), respiratory Flouroquniolones Levofloxacin (Levaquin) 500 mg IV/PO q24h for 7-14 days or 750 mg IV/PO q24h for 5 days (or Moxifloxacin (Avelox) 400 mg PO/IV over 60 minutes q24h for 7-14 days)
- Alternative regimen: Vancomycin 2 g/day IV q6-12h over at least 60 minutes, Linezolid 600 mg IV/PO q12h for 7-21 days , high-dose Amoxicillin (3 g qd with Penicillin minimum concentration of inhibitory <4 mcg/mL).
- Preferred regimen (1): Aqueous crystalline Penicillin-G 6 MU q4-6h IV for 4 weeks
- Preferred regimen (2) (who are unable to tolerate beta lactams therapy): Vancomycin 15 mg/kg IV q12h (target trough concentration, 10-15 mcg/mL); for troughs of 15-20 mcg/mL (MIC, 1 mcg/mL or less), 15-20 mg/kg (actual body weight) IV q8-12h for most patients with normal renal function
- Preferred regimen (3) (If the isolate is resistant (MIC 2 g/mL) to cefotaxime): Cefotaxime 1-2 g q8-12h IV/IM (max dose: 12 g/24 hr) AND Vancomycin 15 mg/kg/day IV q12h AND Rifampin 300 mg IV/PO q8h for 6 weeks, in combination with appropriate antimicrobial therapy
- Alternative regimen (1): Cefazolin 0.5-2 g q8h IV/IM (max dose: 12 g/24 hr)
- Alternative regimen (2): Ceftriaxone 2 g IV q12h
- 3. Sinuses (sinusitis)
- Empiric therapy
- 3.1 For initial empiric treatment of acute bacterial rhinosinusitis in adults
- Preferred regimen: Amoxicillin 500 mg/Clavulanate 125 mg PO tid or Amoxicillin 875 mg/Clavulanate 125 mg PO bid for 5 to 7 days recommended by the Infectious Disease Society of America (IDSA)
- Alternative regimen (1): Doxycycline 100 mg PO q12h
- 3.2 For second-line high-dose therapy for acute bacterial rhinosinusitis in adults
- Preferred regimen: Amoxicillin 2 g/Clavulanate 125 mg PO bid recommended by the Infectious Disease Society of America (IDSA).
- Note: The second line high dose therapy is recommended in adults who have failed initial therapy, in regions of high endemic rates (10% or greater) of invasive Penicillin-nonsusceptible Streptococcus pneumoniae, severe infection.
- 5. CNS (meningitis)
- Empiric therapy
- Preferred regimen: Vancomycin 15 mg/kg/day IV q12h AND a third-generation cephalosporin (Ceftriaxone 2 g IV q12h OR Cefotaxime 2 g IV q4h or 3 g q6h) AND Rifampin 600 mg IV qd in combination with Vancomycin
- Alternative regimen: Meropenem, fluoroquinolones
- General principles
- 1. Pneumovax (23-valent) prevents bacteremia; impact on rates of CAP are modest or nil.
- 2. Prevnar vaccine for children <2 yrs age prevents invasive pneumococcal infection in adults by herd effect. Impact is impressive with rates of invasive pneumococcal infection down 80% in peds and 20-40% in adults.
- 3. Risk for bacteremia in splenectomy, HIV, smokers, black race, multiple myeloma, asthma.
Vaccination in the USA
- A heptavalent pneumococcal conjugate vaccine vaccine (PCV 7) (e.g. Prevnar) is recommended in the USA since 2000 for all children between 2 to 23 months of age. PCV 7 is also recommended for children between 24 to 59 months of age if they are at risk of getting the infection.
- The vaccination is generally given as a 4-doses series at 2, 4, 6 & 12 - 14 months of age.
- The PCV 7 provides a good protection is good against deep pneumococcal infections (especially septicemia and meningitis). Some new vaccines being tested are 9- and 13-valent. No protection is offered if the child is infected by a pneumococcus serotype that is not a component of the current vaccine. The ability of capsular-polysaccharide conjugate vaccines to promote the spread of non-covered serotypes and the limitation has led to research into vaccines that would provide species-wide protection.
- Pneumovax™ which is one trade name for the Pneumococcal polysaccharide vaccine which approximately provides 85% protection for 5 or more years in individuals younger than age 55.
- Individuals at a high risk of infection such as those who are 65 years or older are recommended to get the vaccine.
- Generally it is a single once in a lifetime dose as it is associated with high risk of side effects with repitition. The standard 23-valent vaccines are not effective for children who are less than two years old.
- The American College of Physicians in its current guidelines recommends immunization administration between 2 to 65 years old in the presence of indications, or at age 65. If someone received the immunization before age 60, the guidelines call for a one-time revaccination.
- Periodic revaccination for those who have conditions like asplenia or nephrotic syndrome is indicated.
Vaccination in the UK
- It was announced in February 2006 that the UK government would introduce vaccination with the conjugate vaccine in children aged 2, 4 and 13 months. This is expected to start on September 4, 2006 and is to include changes to the immunisation programme in general.
- In the developing world a plan to accomplish the accelerated new pneumococcal vaccines evaluation and access is done according to the Pneumococcal vaccines Accelerated Development and Introduction Plan (PnemoADIP). Global Alliance for Vaccines and Immunization (GAVI) funds this plan for new pneumococcal vaccines. Almost 30 countries in this list showed interest in participating by 2010. An estimated 5.4 million lives of the children can be saved by PneumoADIP by 2030.
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- Pikis, A; Campos, JM; Rodriguez, WJ; Keith, JM (2001). "Optochin resistance in Streptococcus pneumoniae: mechanism, significance, and clinical implications". Journal of Infectious Diseases. 184 (5): 582–590. doi:10.1086/322803. PMID 11474432.
- Zheng CJ, Sohn MJ, Kim WG. (2006). "Atromentin and leucomelone, the first inhibitors specific to enoyl-ACP reductase (FabK) of Streptococcus pneumoniae". Journal of Antibiotics. 59 (12): 808–12. doi:10.1038/ja.2006.108. PMID 17323650.
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- "Children to be given new vaccine" BBC News, February 08, 2006, retrieved August 25, 2006
- "Pneumococcal vaccine added to the childhood immunisation programme" February 08, 2006
- "Changes to the immunisation programme in the UK" Meningitis Research Foundation, retrieved August 25, 2006
- "PneumoADIP website"