H1: Physicians' Press - A Division of Jones and Bartlett Publishers: Authoritative, Expert, and User-Friendly References for the Medical Community

 

SELF-ASSESSMENT QUESTIONS: OTITIS, MASTOIDITIS, PAROTITIS

1. The most common pathogen isolated from the external auditory canal in patients with external otitis ("swimmer’s ear) is:

a. Pseudomonas aeruginosa
b. Strepococcus pneumoniae
c. Hemophilus influenzae
d. Moxarella catarrhalis

Make your selection before scrolling beyond this point

Answer: P. aeruginosa is a ubiquitous, aerobic gram-negative bacillus frequently found in moist environments (e.g., irrigant solutions, whirlpool baths, hospital sinks). In addition to causing serious infection in hospitalized patients (e.g., hospital-acquired bacteremia, nosocomial pneumonia, etc.), P. aeruginosa may cause infections associated with water exposure, including external otitis (swimmer’s ear), interdigital infection, and hot-tub folliculitis. External otitis presents as acute external ear canal drainage without perforation of tympanic membrane or bone involvement after fresh-water exposure (e.g., swimming pool). External otitis is not an invasive infection and does not require systemic antibiotics. Local therapy with otic solutions (ofloxacin 0.3%, tobramycin, polymyxin B); apply ear drops q6h x 1 week) is highly effective, but the infection may also resolve spontaneously after removal of exposure and drying. If external otitis is associated with a perforated tympanic membrane, ENT consultation and systemic antibiotics are recommended. S. pneumoniae, H. influenzae and M. catarrhalis cause otitis media, not external otitis. (Answer: a)

2. Which of the following statements about "malignant" external otitis are true:

a. Pseudomonas is the usual pathogen, and elderly diabetics are at greatest risk
b. Common manifestations include ear pain, external ear canal discharge, fever, and elevated erythrocyte sedimentation rate
c. Common complications include facial nerve paralysis, meningitis, and brain abscess
d. Aggressive antibiotic therapy without surgical debridement is adequate for cure

Make your selection before scrolling beyond this point

Answer: Malignant otitis media is a potentially life-threatening infection that occurs when P. aeruginosa penetrates the epithelium of the external ear canal to involve underlying soft tissue, cartilage, and bone. Common manifestations include marked ear pain with purulent ear drainage; facial paralysis and trismus may also occur, but meningitis and brain abscess are uncommon. The erythrocyte sedimentation rate is almost always markedly elevated, and can be used to follow the response to therapy. The diagnosis is confirmed by demonstrating P. aeruginosa in soft tissue culture from the ear canal with bone/cartilage involvement on x-ray/MRI. Malignant external otitis usually affects diabetics, and is rare in non-diabetics. Therapy consists of surgical debridement plus antibiotics. Antibiotic therapy is started IV, and one preferred regimen consists of (cefepime or piperacillin) plus either (levofloxacin or gentamicin) x 4-6 weeks. (Answer: a)

3. Which of the following statements about otitis media in adults are true:

a. Usual pathogens are the same in acute and chronic otitis media, including Streptococcus pneumoniae, Hemophilus influenzae, and Moxarella catarrhalis
b. Preferred oral antibiotics for acute otitis media include amoxicillin, a quinolone, cefprozil, clarithromycin XL, or azithromycin
c. Acute and chronic otitis media should be treated with antibiotics for a duration of 2 weeks
d. Acute otitis media tends to recur in children, and depends on the patency and angularity of the eustachian tube

Make your selection before scrolling beyond this point

Answer: Usual pathogens are the same in acute and chronic otitis media, and include S. pneumoniae, H. influenzae, and M. catarrhalis. (H. influenza is more common in chronic otitis media.) Acute otitis media presents clinically with acute unilateral ear pain, fever and a reddened tympanic membrane, which may or may not be perforated. Chronic otitis media presents with earache with minimally reddened tympanic membrane and a history of acute otitis media. The diagnosis of otitis media is clinical, with a reddened tympanic membrane that is full, opaque, and manifests little movement to pneumatic otoscopy. All antibiotics listed above are useful for acute otitis media; preferred antibiotics for chronic otitis media consist of a respiratory quinolone or cefprozil. Patients should be treated empirically for all potential pathogens, since culture of middle ear fluid is usually not possible. Antibiotic therapy should be given for 2 weeks for acute otitis media and 4-6 weeks for chronic otitis media; shorter courses of antibiotic therapy may fail. Treatment with macrolides, TMP-SMX, or oral cephalosporins (except cefprozil) predisposes to resistant S. pneumoniae. Acute otitis media tends to recur in children; patency/angularity of eustachian tube determines risk. (Answer: a, b, d)

4. All of the following statements about mastoiditis are true except:

a. Usual pathogens include Streptococcus pneumoniae, Hemophilus influenzae, and Stapylococcus aureus
b. Acute mastoiditis presents as pain/tendernes over the mastoid without fever
c. Antibiotic therapy is required for 2 weeks for acute mastoiditis and 4-6 weeks for chronic mastoiditis
d. Chronic mastoiditis usually requires surgical debridement for cure

Make your selection before scrolling beyond this point

Answer: Acute mastoiditis may occur secondary to acute/chronic otitis and presents with pain/tenderness over the mastoid with fever. Usual mastoiditis pathogens include S. pneumoniae, H. influenzae, and S. aureus; oral anaerobes and P. aeruginosa are also common pathogens in chronic mastoiditis. Diagnosis is made by CT/MRI showing mastoid involvement; CT/MRI can also demonstrate extension into CNS presenting as acute bacterial meningitis. The prognosis for acute mastoiditis is good if treated early with antibitotics; surgical debridement is usually unnecessary. In contrast, chronic mastoiditis should be considered analagous to chronic osteomyelitis, requiring debridement (in addition to antibiotics) for cure. Useful antibiotics include cefotaxime (acute mastoiditis), cefepime, meropenem, or a quinolone (levofloxacin or gatifloxacin or moxifloxacin for acute mastoiditis; levofloxacin 750 mg or ciprofloxacin for chronic mastoiditis). Antibiotic therapy should be continued for 2 weeks for acute mastoiditis and 4-6 weeks for chronic mastoiditis. (Answer: b)

5. All of the following statements about bacterial (suppurative) parotitis are true except:

a. Usual pathogens include S. aureus, Enterobacteriaceae, or oral anaerobes
b. Risk factors include dehydration, diabetes mellitus, and anticholinergic drugs
c. Can be differentiated from viral parotitis by purulent discharge from Stensen’s duct
d. Infection often resolves with hydration, anti-inflammatory drugs and local heat/ice over salivary gland; without antibiotics

Make your selection before scrolling beyond this point

Answer: Acute bacterial (suppurative) parotitis is usually caused by S. aureus, Enterobacteriaceae, or oral anaerobes. Risk factors include dehydration, diabetes mellitus, anticholinergic drugs, advanced age, intubation, post-operative state, and stones in the parotid duct. Clinical presentation includes unilateral parotid pain and swelling with discharge from Stensen’s duct; fever and dysphagia may also be present. Amylase levels are elevated, and CT/MRI demonstrates parotid duct/gland involvement. Suppurative parotitis can be differentiated from viral parotitis (mumps, coxsackievirus, influenza virus, parainfluenza virus, LCM virus, CMV virus) by purulent discharge from Stensen’s duct, which should be examined by Gram stain and cultured. In addition to intravenous/oral antibiotics and hydration, stones obstructing the parotid duct should be removed. Preferred intravenous therapy consists of 2 weeks of either meropenem 1 gm (IV) q8h or imipenem 1 gm (IV) q6h or ceftizoxime 2 gm (IV) q8h; clindamycin 600 mg q8h or an anti-staphylococcal quinolone q24h may be used. Once stable clinically, the patient can be switched to clindamycin 300 mg (PO) q8h (for S. aureus) or an anti-staphylococcal quinolone (PO) q24h (for Enterobacteriaceae or if the organism is not known) to complete a 2 week course of therapy. (Answer: d)

 

OTITIS EXTERNA/MEDIA PITFALLS

PITFALL: TREATMENT OF MALIGNANT EXTERNAL OTITIS WITH AMINOGLYCOSIDES

Aminoglycosides are sometimes chosen as treatment for malignant otitis externa, due to their anti-Pseudomonas activity and excellent bone penetration. Anti-Pseudomonas agents like meropenem, cefepime, or piperacillin are preferred to aminoglycosides. Although aminoglycosides penetrate bone well, their activity is decreased in the presence of local hypoxia, acidosis and cellular debris, as found in malignant external otitis, which is a form of chronic osteomyelitis.

PITFALL: USE OF DIFFERENT ANTIBIOTICS TO TREAT EACH CHRONIC OTITIS MEDIA RELAPSE

Physicians often feel that the most common cause of relapse after treatment of chronic otitis media is antibiotic resistance, and therefore use different antibiotics for each relapse. Resistance may occur over time to Streptococcus pneumoniae when macrolides or trimethoprim-sulfamethoxazole is used, but individual treatment failure due to resistance is very uncommon. Treatment failure in chronic otitis media is usually due to underdosing and inadequate treatment duration (assuming the antibiotic selected has the appropriate spectrum and the ability to penetrate middle ear fluid in the absence of inflammation). Treatment with antibiotics for a full 4-6 weeks is recommended.

PITFALL: FAILURE TO CONSIDER DIFFERENCES IN ANTIBIOTIC PENETRATION INTO MIDDLE EAR FLUID WHEN SELECTING TREATMENT FOR CHRONIC OTITIS MEDIA

Many clinicians choose antibiotics for chronic otitis media based on considerations other than tissue penetration (e.g., spectrum, resistance potential, side effects, cost), based on the impression that all antibiotics penetrate middle ear fluid in chronic otitis media fairly well. While these other considerations are important, tissue penetration is critical to cure. Oral antibiotics with inflammation-independent tissue penetration are preferred (all other factors being equal), including amoxicillin (not ampicillin), trimethoprim-sulfamethoxazole, cefadroxil or cefprozil (not other cephalosporins), quinolones (children > 2 years), and doxycycline (children > 8 years). Other antibiotics with good tissue penetration (e.g., clindamycin) have inadequate spectrum for chronic otitis media.

  

ARCHIVES

The  other archives can be reached by returning to the Antibiotic Self-Assessment page and clicking on the individual links there.

 

 

Link: Jones and Bartlett Publishers© 2009 Jones and Bartlett Publishers