Chapter 128. Pneumococcal Infections (Part 3)

Specific Infections Caused by S. Pneumoniae S. pneumoniae causes infections of the middle ear, sinuses, trachea, bronchi, and lungs (Table 128-2) by direct spread from the nasopharyngeal site of colonization. Infections of the central nervous system (CNS), heart valves, bones, joints, and peritoneal cavity usually arise by hematogenous spread. Peritoneal infection may also result from ascent via the fallopian tubes. The CNS may also be infected by drainage from nasopharyngeal lymphatics or veins or by contiguous spread of organisms (e.g., through a tear in the dura). Primary pneumococcal bacteremia—i.e., the presence of pneumococci in the blood with no apparent...
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Chapter 128. Pneumococcal Infections (Part 3) Chapter 128. Pneumococcal Infections (Part 3) Specific Infections Caused by S. Pneumoniae S. pneumoniae causes infections of the middle ear, sinuses, trachea,bronchi, and lungs (Table 128-2) by direct spread from the nasopharyngeal site ofcolonization. Infections of the central nervous system (CNS), heart valves, bones,joints, and peritoneal cavity usually arise by hematogenous spread. Peritonealinfection may also result from ascent via the fallopian tubes. The CNS may also beinfected by drainage from nasopharyngeal lymphatics or veins or by contiguousspread of organisms (e.g., through a tear in the dura). Primary pneumococcalbacteremia—i.e., the presence of pneumococci in the blood with no apparentsource—occurs commonly in children the pleural space; the route usually cannot be determined in any individual case.Infections listed after meningitis in Table 128-2 are uncommon or rare. Table 128-2 Most Common Infections Caused by StreptococcusPneumoniae in Adults Site Infections Respiratory tract Otitis media Acute sinusitis Tracheobronchitis Pneumonia Empyema Central nervous system Meningitis Brain abscess Cardiac Endocarditis Pericarditis Soft tissue/skeletal Septic arthritis Osteomyelitis Cellulitis Other Peritonitis Endometritis Primary bacteremia Otitis Media and Sinusitis Otitis media and acute rhinosinusitis are similar in terms of pathogenesis.Bacteria are trapped in a normally sterile site when drainage is impaired, often as aresult of viral infection, allergies, or exposure to pollutants (including cigarettesmoke). In both disease states, S. pneumoniae is the most common or second mostcommon isolate (after nontypable Haemophilus influenzae) from cultures of theinfected site. Pneumonia The distinctive symptoms and signs of pneumonia, whether due to thepneumococcus or to other bacteria, are (1) cough and sputum production, whichreflect bacterial proliferation and the resulting inflammatory response in thealveoli; (2) fever; and (3) radiographic detection of an infiltrate. Predisposing Conditions Pneumococcal pneumonia is most common at the extremes of age. Despitethe undisputed role of S. pneumoniae as a major pathogenic bacterium for humans,the great majority of adults with pneumococcal pneumonia have underlyingdiseases that predispose them to infection. Otherwise-healthy military recruitsinvolved in outbreaks of infection may be an exception to this rule; however,many of these individuals have been under extreme physical and/or psychologicalstress and/or have had an antecedent viral-type illness that may have reduced theirnormal host resistance. Infections with respiratory viruses, especially influenzavirus, predispose to pneumococcal pneumonia. Other common predisposingconditions are alcoholism, malnutrition, chronic pulmonary disease of any kind(including asthma), cigarette smoking, HIV infection, diabetes mellitus, cirrhosisof the liver, anemia, prior hospitalization for any reason, renal insufficiency, andcoronary artery disease (with or without recognized congestive heart failure). Inelderly subjects, the predisposition is generally multifactorial. Presenting Symptoms Patients often present with a clear exacerbation of a preexisting respiratorycondition. They may have felt unwell for several days, with coryza or anonproductive cough and low-grade fever, but they feel distinctly worse at thetime of onset of pneumonia. Coughing, often productive of purulent sputum,becomes prominent. The temperature may rise to 38.9°–39.4°C (102°–103°F),although a substantial proportion of patients are afebrile at admission. In a smallproportion of cases, the onset of disease follows a hyperacute pattern in which thepatient suddenly has a single episode of shaking chills followed by sustained feverand a cough productive of blood-tinged sputum. In the elderly, the onset of diseasemay be especially insidious and may not suggest pn ...