Acute and chronic alcohol ingestion exert direct and indirect effects on host defenses against infection (Table 90.1). Recent studies suggest that the immunotoxic effects of ethanol are due to direct cytotoxicity and to a shift in the balance of cytokines produced from the proinflammatory to more immunoinhibitory products. However, the adverse effects of ethanol itself may be indistinguishable from those due to concomitant cirrhosis, malnutrition, poor hygiene, adverse living conditions, and abuse of tobacco and other drugs. This discussion includes infections associated with increased frequency or severity in patients who abuse alcohol (Table 90.2). The suggested antibiotic dosages are for adult patients with normal renal function. Therapeutic decisions always should be made with the knowledge that alcoholic liver disease can interfere with the metabolism and excretion of certain antiinfective agents and that some antimicrobials can cause or exacerbate hepatic dysfunction.

PNEUMONIA

Bacterial pneumonia usually follows aspiration of oropharyngeal flora into the lungs. Severe intoxication is associated with altered consciousness and a diminished cough reflex. Elevated ethanol levels can interfere with cilial function on the surface of respiratory epithelial cells. Most alcoholics also smoke cigarettes, which further impairs mucociliary defenses against infection of the respiratory tract. The most frequent bacterial causes of pneumonia in ethanol abusers include Streptococcus pneumoniae, anaerobes, aerobic gram-negative bacilli, and Haemophilus influenzae. Standard diagnostic approaches are used to evaluate alcoholic patients who exhibit signs or symptoms of pneumonia.