Pneumococcal Infections

Medical Pharmacology Chapter 35 Antibacterial Drugs

Pneumococci (Streptococci pneumoniae): gram-positive cocci that grow in chains.
Streptococci pneumoniae colonize the nasopharynx

Infections caused by S. pneumoniae from most to least common in adults
Acute sinusitis S. pneumoniae is the most common organism cultured from middle ear fluid or from paranasal sinus from patients with otitis media or sinusitis respectively. Almost equally common is nontypable Hemophilus influenzae. Pneumonia Pneumococcal pneumonia is most common in the very young and elderly. Symptoms include: Cough and sputum production fever plain film detection of an infiltrate Most adults with pneumococcal pneumonia have an underlying disease the make them more vulnerable to infection. Predisposing factors include: prior viral respiratory illness alcoholism malnutrition chronic pulmonary disease diabetes mellitus hepatic cirrhosis renal insufficiency congestive heart failure infection with human immunodeficiency virus (HIV) Acute purulent tracheobronchitis Otitis media S. pneumoniae is the most common organism cultured from middle ear fluid or from paranasal sinus from patients with otitis media or sinusitis respectively. Almost equally common is nontypable Hemophilus influenzae. Empyema Meningitis S. pneumoniae is the most common cause of bacterial meningitis in adults {except during meningococcal infection} S. pneumoniae is also the most common cause of bacterial meningitis in infants and toddlers (but not new borns) due to the effectiveness of vaccination against H. influenzae. Meningitis usually results from extension of sinus or middle ear infection, but may occur from bacteremia and subsequent infection of the choroid plexus. Primary bacteremia Osteomyelitis Septic arthritis Peritonitis Pericarditis Endometritis Cellulitis Brain abscess

**Treatment Principles**
ß-Lactam antibiotics are the primary drugs used in treating pneumococcal infections. With the development of resistance, higher drug concentrations or different agents have been used. By 1995 about 20% of streptococcal strains showed intermediate levels ; between 2% to 5% of strains showing a high degree of resistance. Some intermediate level of resistant strains also showed resistance to erythromycin, newer macrolides, tetracyclines, trimethoprim-sulfamethoxazole (Bactrim) and clindamycin (Cleocin). Some highly penicillin-resistant strains are also resistant to second-generation and some third-generation cephalosporins. Most strains remain sensitive to cefotaxime (Claforan), ceftriaxone (Rocephin), and imipenem. The vast majority of pneumococcal strains remain sensitive to vancomycin (Vancocin), although acquisistion of resistance to this agent is of concern in view of the emergence of vancomycin-resistant enterococci and other gram-positive microbes.

**Specific Antibiotic Treatment:**
Pneumonia: For penicillin-sensitive or intermediate resistant strains: penicillin is used. Clindamycin is also efficacious in treating these strains. For highly resistant strains, i.v. cefotaxime, ceftriaxone or imipenem is usually effective (90%). For strains resistant to these agents, vancomycin must be used. If the infection is thought to be life-threatening and without susceptibility information, initial treatment with cefotaxime or ceftriaxone would be appropriate. For hospitalized patients with suspected pneumococcal pneumonia, a life-threatening condition, this approach might be considered. Patients with severe drug allergy to penicillins may be treated with an advanced macrolide, clindamycin, or vancomycin pending susceptibility testing results.

**Meningitis:**
Meningitis: the most life-threatening of pneumococcal infections. Initial Treatment: cefotaxime plus vancomycin. Cefotaxime is highly efficacious against most strains and penetrates the blood-brain barrier; vancomycin is very effective, but may not reliably enter the CNS. If the strain is sensitive to penicillin, then treatment can be continued with penicillin. Rifampin inhibits the activity of ß-lactam agents and should not be used in this situation

Musher, D.M., Pneumococcal Infections, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 874-875.

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