Antimicrobial Therapy in Otolaryngology
Marina Boruk
Richard M. Rosenfeld
One-fourth of all Americans who seek medical care do so because of an infectious disease. At least 150 million courses of antibiotics costing more than $16 billion are prescribed in the United States each year. Physicians who deal with the upper respiratory tract treat the largest number of patients with these infections. Therefore, these physicians must be current in their understanding of the uses and costs of antimicrobial agents.
In deciding when and what medication to prescribe, the factors listed below must be kept in mind.
Clinical diagnosis (Table 49-1)
Most likely infecting organism
Natural course of the infectious process
Co-morbid conditions, such as immunologic status, renal failure, or liver failure
Patient’s reliability and compliance with medication taking
Potential morbidity of the medication
Reactivity with other medications the patient is taking
Cost of the medication
Potential complications of not treating or undertreating the infection
Immunologic status is an important factor in the choice of antimicrobial agent. Because a patient with an immunodeficiency disorder is more likely to incur opportunistic and rare infectious diseases, a more potent, broader-spectrum antibiotic and antifungal agent should be prescribed. Prophylactic antibiotics are commonly given to prevent common opportunistic infections, such as trimethoprim-sulfamethoxazole to prevent Pneumocystis carinii pneumonia among patients with acquired immunodeficiency syndrome (AIDS).
Renal and liver functions are important factors in deciding on the type of antimicrobial agent to give (renal clearance versus hepatic clearance) and the dosage of the medication. For example, a patient with renal failure who depends on hemodialysis needs to have an adjusted dose depending on whether the drug can be dialyzed and needs to be more carefully observed for toxic drug levels in the bloodstream. Patients with liver failure often are not able to metabolize some medications to the activated form.
THE ANTIBIOTIC PARADOX
An unfortunate paradox of antibiotics is how misuse destroys their curative powers. Despite new and ongoing discoveries of better and stronger antibiotics, multidrug bacterial resistance is a mounting global health problem. As noted by Stuart Levy, author of The Antibiotic Paradox, “prudent use of antibiotic requires an understanding of and foresight into the environmental
consequences of antibiotic use. Susceptible bacteria are important allies in controlling the invasion and propagation of resistant bacteria. The aim of current and future use of antibiotics should be the revival and maintenance of the normal susceptible microbial flora.”
consequences of antibiotic use. Susceptible bacteria are important allies in controlling the invasion and propagation of resistant bacteria. The aim of current and future use of antibiotics should be the revival and maintenance of the normal susceptible microbial flora.”
Prudent and judicious use of currently available antibiotics is essential to preserve their efficacy. Clinicians are cautioned to consider the factors listed below when prescribing antibiotics for infections of the head, neck, or upper respiratory tract.
Antibiotics are appropriate only for bacterial infections. Viral infections that commonly involve the head and neck but do not benefit from antibiotics include croup, bronchitis, influenzae, common cold, nonstreptococcal tonsillopharyngitis, and most cervical adenitis. Note that rhinorrhea accompanying a viral upper respiratory tract infection may be clear, cloudy, green, yellow, or event purulent, and that color alone does not imply bacterial origin.
Not all presumed bacterial infections require antibiotics. For example, many episodes of nonsevere rhinosinusitis and acute otitis media resolve spontaneously, especially in adults and older children. Antibiotics may be safely withheld in selected circumstances (see below), allowing the patient to “fight the infection” on their own. Conversely, withholding antibiotics is inappropriate for infections that are severe (e.g., malignant external otitis) or complicated (e.g., sinusitis with orbital cellulitis).
Give the right drug for the right bug. Common causes of acute ear, nose, and throat infections include Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, and group A beta-hemolytic streptococcus; chronic infections often include Pseudomonas aeruginosa, Staphylococcus aureus, and anaerobic organisms. Certain commonly used antibiotics (e.g., azithromycin, clarithromycin, cefprozil, and trimethoprim-sulfamethoxazole) are relatively ineffective for several bacteria, and have effects worse than placebo because they induce further resistance.
Educate patients regarding proper antibiotic use. When antibiotics are prescribed, patients are advised to use as directed and finish all medication; short or incomplete treatment will foster resistant bacteria. Self-medication is strongly ill advised. Educational pamphlets are available from the Centers for Disease Control and Prevention and many national medical societies.
All antibiotics have community effects. At the individual (patient) level, antibiotic use unfavorably alters the normal balance between commensal bacteria and pathogens in the skin, gut, and respiratory tract (especially the nasopharynx). These changes correlate directly with bacterial resistance patterns in surveillance studies at the population level.
EMPIRIC THERAPY FOR HEAD AND NECK INFECTIONS
Antimicrobial therapy ideally should be based on culture results from specific infections. In some instances, however, culture studies may be impractical or the clinical condition too threatening for treatment to await culture results. Empiric therapy
is then based on the probability that a certain organism caused the clinical condition.
is then based on the probability that a certain organism caused the clinical condition.
Acute Otitis Media and Sinusitis
Otitis media and acute sinusitis, whether complicated or uncomplicated, have a common bacteriologic source. Most cases—50% to 70%—are comprised of S. pneumoniae and H. influenzae (nontypable). M. catarrhalis, a low-virulence pathogen, is also prevalent; over 80% of these cases resolve without treatment. Viruses are also prevalent and often mimic bacterial infection. Persistent symptoms after initial antibiotic treatment may represent (1) a sustained inflammatory response despite killing of bacteria; (2) reinfection with a different organism; or (3) continued growth of the initial organism despite drug sensitivity. β-lactamase resistance by H. influenzae runs about 35% nationwide, and by M. catarrhalis more than 90%. About 15% to 30% of pneumococcus is penicillin resistant. Anaerobic organisms in acute sinusitis suggest dental disease as the source.
Many patients aged 2 years or older with uncomplicated acute otitis media or sinusitis, especially with nonsevere symptoms, are suitable for initial observation, reserving antibiotic therapy for those who fail to improve within 48 to 72 hours (appropriate follow-up is essential). With this approach, about 70% of patients will resolve without antibiotics. For those who fail to resolve, or present initially with severe or complicated infections, drugs of choice include amoxicillin, amoxicillin-clavulanic acid, or erythromycin plus sulfonamide for penicillin-allergic patients. Alternatives include second- and third-generation cephalosporins (e.g., ceftibuten, cefpodoxime, or cefuroxime axetil). Fluoroquinolones are highly effective second-line agents for adult sinusitis. Ceftriaxone is effective for refractory or complicated acute otitis media or sinusitis.
Otitis Media with Effusion
Otitis media with effusion usually follows an acute infection and is the subacute or incompletely resolved stage of acute otitis media even after adequate treatment. Ninety percent of effusions resolve spontaneously within 3 months of acute otitis media. Chronic otitis media with effusion that lasts longer than 3 months has a cure rate of only about 15% with watchful waiting. Regardless of the duration of otitis media with effusion, the effect of antibiotic therapy is marginal and short-lived. Antibiotic-treated and placebo-treated children have comparable outcomes several weeks after completing therapy. Myringotomy, fluid aspiration, and insertion of tympanostomy tubes reduces the resolution time and eliminates the need for oral antibiotics in highly selected children with chronic effusions despite prolonged observation and monitoring.
Chronic Suppurative Otitis Media
Chronic suppurative otitis media with tympanic membrane perforation, with or without cholesteatoma, results from mixed infections with both aerobic pathogens (P. aeruginosa, S. aureus and S. epidermidis, Proteus, Klebsiella, and Eschericia coli organisms) and anaerobic pathogens (Bacteroides fragilis, Peptococcus organisms, and Veillonella organisms) that produce foul-smelling
purulent discharge. Initial treatment includes ofloxacin otic drops; alternatives include neomycin-polymyxin, or gentamicin ophthalmic drops. Oral therapy alone is not very effective; however, adjunctive systemic therapy with oral ciprofloxacin, with or without clindamycin, or ticarcillin/clavulanate IV is sometimes required.
purulent discharge. Initial treatment includes ofloxacin otic drops; alternatives include neomycin-polymyxin, or gentamicin ophthalmic drops. Oral therapy alone is not very effective; however, adjunctive systemic therapy with oral ciprofloxacin, with or without clindamycin, or ticarcillin/clavulanate IV is sometimes required.
Acute Otitis Externa
Acute otitis externa usually is caused by P. aeruginosa. S. aureus is also prevalent. Although P. mirabilis, streptococci, and other gram-negative bacilli are also recovered from cultures, they respond to the same treatment. Oral therapy may be required in diabetic patients to prevent necrotizing otitis. Otomycosis is generally caused by Aspergillus niger or Candida albicans (monilia). Treatment involves topical therapy with an acidifying or antimicrobial drop (e.g., ofloxacin) with or without an antiinflammatory agent after cleansing of the ear canal (Table 49-2).
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