Chapter 128. Pneumococcal Infections (Part 3)

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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) 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 source—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 Streptococcus Pneumoniae 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 a result of viral infection, allergies, or exposure to pollutants (including cigarette smoke). In both disease states, S. pneumoniae is the most common or second most
common isolate (after nontypable Haemophilus influenzae) from cultures of the infected site. Pneumonia The distinctive symptoms and signs of pneumonia, whether due to the pneumococcus or to other bacteria, are (1) cough and sputum production, which reflect bacterial proliferation and the resulting inflammatory response in the alveoli; (2) fever; and (3) radiographic detection of an infiltrate. Predisposing Conditions Pneumococcal pneumonia is most common at the extremes of age. Despite the undisputed role of S. pneumoniae as a major pathogenic bacterium for humans, the great majority of adults with pneumococcal pneumonia have underlying diseases that predispose them to infection. Otherwise-healthy military recruits involved in outbreaks of infection may be an exception to this rule; however, many of these individuals have been under extreme physical and/or psychological stress and/or have had an antecedent viral-type illness that may have reduced their normal host resistance. Infections with respiratory viruses, especially influenza virus, predispose to pneumococcal pneumonia. Other common predisposing conditions are alcoholism, malnutrition, chronic pulmonary disease of any kind (including asthma), cigarette smoking, HIV infection, diabetes mellitus, cirrhosis of the liver, anemia, prior hospitalization for any reason, renal insufficiency, and
coronary artery disease (with or without recognized congestive heart failure). In elderly subjects, the predisposition is generally multifactorial. Presenting Symptoms Patients often present with a clear exacerbation of a preexisting respiratory condition. They may have felt unwell for several days, with coryza or a nonproductive cough and low-grade fever, but they feel distinctly worse at the time 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 small proportion of cases, the onset of disease follows a hyperacute pattern in which the patient suddenly has a single episode of shaking chills followed by sustained fever and a cough productive of blood-tinged sputum. In the elderly, the onset of disease may be especially insidious and may not suggest pneumonia at all. Such persons may have minimal cough, no sputum production, and no fever, instead appearing tired or confused. Nausea and vomiting or diarrhea occurs in up to 20% of cases of pneumococcal pneumonia. Symptoms of a new cardiac arrhythmia, myocardial ischemia, or an actual infarction occur in 10% of patients at a veterans' hospital who are admitted for pneumonia, and these manifestations may even predominate. The pneumonia may precipitate cardiogenic or noncardiogenic pulmonary edema. Pleuritic chest pain may result from extension of the inflammatory process to the visceral pleura; persistence of this pain, especially after the first day or two of
treatment, raises concern about empyema (see "Complications," below). Clearly, the range of symptoms is sufficiently broad that no characteristic presentation distinguishes pneumococcal pneumonia from other types of bacterial pneumonia or from some types of nonbacterial pneumonia.