1. Explain potential downsides to antibiotic therapy.

2. Cite and follow the recommended treatment algorithm when bacterial meningitis is strongly suspected.

3. Describe antibiotic options for treating outpatient and serious methicillin-resistant Staphylococcus aureus infections and current recommended timing of antibiotics for community-acquired pneumonia.

4. Evaluate patients with travel-related illness.

5. Diagnose and manage diarrheal illness, dermatologic problems, and malaria acquired abroad.

Antibiotic Use and Misuse
Lisa Winston, MD, Assistant Clinical Professor, Division of Infectious Diseases, University of California, San Francisco, School of Medicine; Interim Vice Chief, Medical Service, and Hospital Epidemiologist, San Francisco General Hospital

General points: obtain blood for cultures before giving patients antibiotics (do not assume blood already drawn); threshold for obtaining cultures in emergency department (ED) and urgent care settings has dropped in recent years, due to increased antibiotic resistance (which has made it harder to predict appropriate antibiotic and course of treatment); with some conditions (eg, stable patient with suspected late prosthetic joint infection), not necessary to give antibiotics immediately; in such cases, obtaining cultures in operating room (OR) can be critical for making diagnosis, and antibiotic can interfere with diagnostic testing; avoid antibiotics for viral infections (eg, upper respiratory infections [URIs], influenza-like illnesses, most bronchitis, most pharyngitis); impact of antibiotics minimal for some bacterial infections (eg, sinusitis, pediatric otitis media)

Downside to antibiotics: unnecessary antibiotics not therapeutically neutral; adverse reactions; drug interactions; Candida overgrowth; resistance (patient-specific and more generally in population); Clostridium difficile (just one dose of antibiotic can predispose to C difficile overgrowth, and risk lasts for several weeks); expensive

Bacterial meningitis: antibiotics and corticosteroids—data show adding dexamethasone to treatment provides morbidity and mortality benefit in adults with Streptococcus pneumoniae meningitis; to get benefit, corticosteroid must be given before (or with first dose of) antibiotic; common organisms—S pneumoniae most common organism in all age groups; Listeria monocytogenes tends to be seen in elderly and in immunocompromised patients; Neisseria meningitidis second most common organism in adults (also seen in adolescents and children); bacterial meningitis fairly rare (incidence of S pneumoniae meningitis 1.1 cases/100,000 per year)

Treatment algorithm (strong suspicion of bacterial meningitis): indications for head computed tomography (CT) in adults include immunocompromise, history of central nervous system (CNS) disease (including mass lesion, stroke, or focal infection), new-onset seizure, papilledema, and altered consciousness; if head CT indicated—obtain blood cultures en route to scanner; after CT, initiate therapy with dexamethasone and empiric antibiotic; if head CT negative, do lumbar puncture (LP) to determine whether cerebrospinal fluid (CSF) findings consistent with bacterial meningitis (if not, stop therapy); if head CT not indicated—obtain blood cultures and LP in timely manner, give dexamethasone and empiric antibiotic, and look at CSF findings; key to treatment—if bacterial meningitis strongly suspected, think about condition up front and give antibiotics early; recommended antibiotics—ceftriaxone plus vancomycin; ampicillin added in adults >60 yr of age or patients who are immunocompromised

Treatment algorithm (bacterial meningitis considered but not strongly suspected): eg, patient with chronic disease, drug abuse; if considering doing LP to rule out bacterial meningitis, follow through; in stable patients, can often wait for initial LP results; in sicker patients (or if testing delayed), give ceftriaxone alone after obtaining blood cultures; without reasonable suspicion that patient has pneumococcal meningitis, speaker does not advocate giving dexamethasone initially; not wrong to give more aggressive antibiotics while waiting for LP results, but unnecessary in most cases

Methicillin-resistant Staphylococcus aureus (MRSA): clinicians should think of MRSA whenever dealing with disease caused by S aureus, or with serious infections, eg, necrotizing soft tissue infections, community-acquired pneumonia (CAP) in seriously ill patients (obtain sputum Gram stain and culture); cautions against overdiagnosing MRSA— eg, traditional cellulitis caused by S aureus in only 50% of cases; other 50% caused by β-hemolytic streptococci; trimethoprim-sulfamethoxazole (TMP-SMZ) and doxycycline, drugs commonly used to treat outpatient MRSA infections, not very effective against streptococci; combination therapy with amoxicillin plus doxycycline or TMP-SMZ recommended; clindamycin alone covers staphylococci and streptococci, although resistance growing in staphylococci; treatment of choice for uncomplicated abscesses usually drainage alone

Antibiotic options for outpatient MRSA infection: TMP-SMZ (most reliable); doxycycline (limited data on efficacy against S aureus but probably works well; some areas with higher resistance); clindamycin (reasonable choice when trying to cover Staphylococcus and Streptococcus; some areas with higher resistance; resistance inducible; may be particularly associated with risk for C difficile overgrowth); rifampin (reliable but cannot be used alone; generally not prescribed in ED and not used alone, due to rapid development of resistance; used more commonly for recurrent infections); not recommended—fluoroquinolones (>50% of MRSA infections resistant); li-nezolid (high cost); dosages—for TMP- SMZ, two double-strength tablets q12h

Therapy for serious MRSA infections: if worried about possible MRSA infection in seriously ill patient, start vancomycin in ED; if patient not doing well after admission, switch to another antibiotic (eg, linezolid, daptomycin)

Timing of antibiotics for CAP: before 2004, Medicare guidelines recommended that patients be given antibiotics within 8 hr of hospital arrival; in 2004, Centers for Medicare and Medicaid Services (CMS) and Joint Commission for the Accreditation of Healthcare Organizations adopted 4-hr rule; after significant input from various sources, standard changed to 6 hr; rule applies to—adults with principal discharge diagnosis of pneumonia; exemptions; potential disadvantages of 4-hr rule— less accurate diagnosis; overuse of antibiotics; prioritization of CAP patients over others; decreased ability to focus on other quality-improvement measures

Infectious Disease Society of America/American Thoracic Society (IDSA/ATS) guidelines for empiric treatment of CAP: outpatient—previously healthy and no antibiotics (macrolide or doxycycline) within 3 mo; comorbid conditions or antibiotics within 3 mo (select different class of drug; options include respiratory fluoroquinolone, or β-lactam plus macrolide or doxycycline); inpatient not in intensive care unit (ICU)—respiratory fluoroquinolone, or β- lactam plus macrolide or doxycycline; inpatient, ICU— β-lactam plus azithromycin or respiratory fluoroquinolone (for patients with penicillin allergy, substitute aztreonam for β-lactam); for suspected Pseudomonas aeruginosa infection— antipneumococcal antipseudomonal β-lactam plus ciprofloxacin or levofloxacin, or β-lactam plus aminoglycoside and either azithromycin or respiratory fluoroquinolone (seldom done, but in guidelines); in patient who presents severely ill with CAP—consider community-acquired MRSA and add vancomycin to initial treatment regimen until microbiologic information obtained

Health care-associated pneumonia (HCAP): hospital-acquired pneumonia (HAP); ventilator-associated pneumonia (VAP); IDSA/ATS treatment guidelines for these as well; organisms most likely to cause early HCAP include S pneumoniae, Haemophilus influenzae, S aureus, and antibiotic-sensitive gram-negative bacilli; treat these patients with relatively narrow-spectrum therapy

Travel Medicine: The Globalization of Emergency Medicine
Michael Van Rooyen, MD, MPH, Associate Professor, Department of Emergency Medicine, Harvard Medical School, and Chief, Division of International Health, Brigham and Women’s Hospital, Boston, MA

Risk associated with global travel: high-risk groups include those visiting family and/or friends; travelers who stay with local families; remote, expedition, or adventure travelers; those who indulge in high-risk behaviors; travelers with predisposing conditions and morbidities

Clinical evaluation of returning tropical traveler: includes detailed history, assessment of risk, physical examination, and laboratory testing; historical background—includes patient’s travel itinerary (countries and regions visited); geographic distribution of disease; duration of exposure; climate; risky activities; progression of symptoms; travel itinerary—depending on country patient has visited, clinician must consider different diseases (eg, type of malaria seen in Africa different from type seen in Central and South America); duration of travel—risk of acquiring certain diseases directly related to amount of time spent in country

Relative risk per traveler: high risk—traveler’s diarrhea; URI; noninfectious illness, eg, cardiac problems, complications of medication; moderate risk—sexually transmitted diseases (STDs); certain types of malaria; dengue; low risk and very low risk—illnesses much less common

High-risk behaviors: ingestion of local foods; participation in local customs (eg, blood drinking); prolonged exposure to contaminated food or water; sleeping in strange places; “stupid behavior” (eg, handling infected or poisonous animals); “really stupid behavior” (eg, prostitution, needle sharing)

Diarrheal illness: case—27-yr-old Secret Service agent returns after accompanying President of United States to India; presents after 3 mo of diarrhea; blood and mucus in stool; no fever; some cramping; mild abdominal tenderness; in case like this, main diagnostic issue whether diarrhea caused by common offender (rotavirus; Salmonella; Shigella; enterotoxigenic or enteroinvasive Escherichia coli) or by severe endemic infection (giardiasis; amebiasis; typhoid; cholera); obtain basic laboratory tests; often necessary to treat empirically before diagnosis; returning tropical traveler with diarrhea (with or without fever) also requires malaria smear; in this case, fecal smear positive for white blood cells and Giardia cysts; patient prescribed metronidazole (eg, Flagyl) and sent home; improved slightly but did not fully recover; returned for reevaluation and referred to gastrointestinal (GI) specialist; eventually diagnosed as also having amebiasis; prescribed luminal agent (diloxanide) and responded well to treatment; take-home points—if patient has diarrhea, establish whether blood, pus, or mucus in stool, and if diarrhea chronic; recognize that many diarrheal illnesses acquired abroad polymicrobial; set up system for reevaluation

Prevention: food—transmits most traveler’s diarrhea; basic preventive recommendations include avoiding salads (if one cannot confirm food well cooked or boiled, or cannot peel it, it should be avoided); water—fastidious treatment of water for drinking and brushing teeth; use of bottled water and other bottled beverages (traveler should break seal); black coffee or tea fine; no ice; avoid swimming in freshwater lakes, due to possible sewage contamination; methods of water purification—boiling (up to 1 min sufficient); iodine (effective except against protozoans and Giardia); filtration (must be done with approved filtration device)

Prophylaxis: routine prophylaxis with ciprofloxacin not recommended; recommended that travelers carry medication (eg, ciprofloxacin, loperamide [eg, Imodium]) in case diarrhea develops

Symptomatic treatment: self-treatment usually recommended; sudden onset with cramps and discomfort indicative of bacterial infection; slow-onset diarrhea for >3 to 4 wk indicates parasitic infection; fluoroquinolones used for treatment of presumed bacterial diarrhea; can add metronidazole if diarrhea persists for >2 wk; bismuth subsalicylate (eg, Pepto- Bismol) good treatment but requires large dosage and tastes unpleasant; loperamide very effective (however, Centers for Disease Control and Prevention [CDC] recommends not taking drug if blood and/or mucus in stool)

Dermatologic problems: case—38-yr-old woman presents with intensely pruritic rash on hands and groin; rash developed while patient traveling in Amazon; when dealing with dermatologic condition acquired during travel, determine whether problem primary, result of topical exposure (eg, insect bite) or general response (eg, to medication), or cutaneous manifestation of systemic disease; in this case, patient admitted to sleeping in hut used by miners; diagnosed with severe case of scabies and treated with hydroxyzine (eg, Atarax) and lindane; second case—24-yr-old woman returned from military tour in Middle East; presented with itchy track-like lesion on right buttock; admitted to spending days off lying on beaches, but denies any other exposure; source of lesion determined to be cutaneous larva migrans (from hookworm in dog feces on beach); diagnosis clinical; treat with antihelminthic agent; both examples demonstrate importance of patient history in making diagnosis

Case example (malaria): 45-yr-old man returns from climbing Mt. Kilimanjaro; took chloroquine prophylaxis but comes in with undulating fever of 104ºF, neck stiffness, and photophobia; potential diagnoses include malaria, dengue, and meningitis; working diagnosis malaria; thick and thin blood smears required to confirm (meanwhile, patient should be treated presumptively for malaria and meningitis); in this case, thick and thin smears revealed high rate of parasitemia; patient treated in hospital with antibiotics and intravenous (IV) quinine; condition worsened (patient unresponsive and catatonic); patient with high rate of parasitemia who is given antimalarial medication can develop very high fever and progressive mental status changes that can lead to state of akinetic mutism, in which patient can become significantly hypoglycemic, hyponatremic, and have sequestration of red blood cells; patients eventually recover if treated and supported appropriately; take-home points—think of malaria in returning traveler who has high fever; treat other life threats; during treatment, monitor eg, blood glucose

Malaria: 1500 cases/yr in returning travelers in United States; Plasmodium falciparum causes 90% of malaria in sub-Saharan Africa; Plasmodium vivax and Plasmodium ovale cause 90% of malaria in South America and Caribbean; characterized by flu-like symptoms, diarrhea, and malaise; can be associated with altered mental status (cerebral malaria), and renal failure (blackwater fever); prophylaxis—for chloroquine-sensitive malaria, travelers should take chloroquine or hydroxychloroquine (CDC recommends also carrying dose of atovaquone plus proguanil [Malarone]); travelers to areas with chloroquine-resistant malaria should take mefloquine, doxycycline, or atovaquone plus proguanil; prevention—behavior modification important (do not go out at dusk; wear long-sleeved clothing at night; use insect repellant [N,N-diethyl-m- toluamide {DEET}extremely effective]; concentration of 50% adequate permethrin extremely safe in humans; combination effective in preventing mosquito bites and malaria)