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Common Infections in the Ambulatory Setting – Best Antibiotic Choices

ENT/Respiratory Infections
Otitis Media
Consider Ø Rx and f/u prn (if >6 mo)
Common Bugs: S. Pneumo, H. Flu
1st Line: Amox (80/mg/kg/day, three divided doses)
Acute Sinusitis
Common Bugs: S. Pneumo, H. Flu
1st Line: Amox (consider double dose), Levofloxacin if resistant
Pharyngitis
Common Bugs: Group A strep
1st Line: PCN 500 BID x 10D
Erythromycin x 10D if PCN allergy Amox in kids (liquid amox tastes better than liquid PCN)
Pneumonia
Common Bugs: S. Pneumo, Atypicals, H. Flu
1st Line: macrolide, doxycycline
Consider Levofloxacin if refractory,
Pt. is elderly, pt. has co-morbidities

GI Tract Infections
Traveller’s Diarrhea
Common Bugs: E. Coli, Salmonella, Shigella, Campylobacter, Parasite
1st Line (Bacterial): Cipro 500 BID

x 3 days, initiate if Sx’s >24 hours, fever, bloody diarrhea;
Single-dose azithromycin for kids
1st Line (Giardia, Entamoeba): Metronidazole
Pseudomemb. Colitis/C. diff
PO Vanco 125 QID x 10D or
Fidaxomicin 200 BID x 10D
Metronidazole now 2nd line

GU Tract Infections
UTI (Uncomplicated)
Common Bugs: E. Coli, other Gram negs, S. Saphrophyticus
1st Line: Macrobid 100 BID x 5D, Bactrim DS BID x 3D
Cipro 250 BIDx 3D (second line)

STI’s
Chlamydia: 1 gm Azithro po x 1
Gonorrhea: Ceftriaxone 250 IM x 1
& Azithro 1 gram PO x 1
Partner(s) must be treated

Vaginitis
Candida: OTC antifungals or Fluconazole 150mg PO x T
Bacterial Vaginosis: Flagyl (po/pv) Trichomonas: Flagyl (treat partner)

Skin Infections
Acne
Common Bug: P. Acnes
1st Line: Doxy (Beware of photosensitivity rxn)
Cellulitis/Impetigo/Abscess
Diclox/Keflex (QID), 2nd line: Clinda
Drain Abscess, Can use Bactroban for impetigo; MRSA: Bactrim, Doxy


Oral Antibiotics – Guidelines for Coverage of Common Bacteria

Penicillins SE: GI upset, allergic reaction (rash, anaphylaxis), yeast infection, ↓ seizure threshold, C. diff colitis
Penicillin
+++ Group A Strep, oral anaerobes, T. pallidum
++  Strep pneumoniae,
--- S. aureus, Gonorrhea
Amoxicillin
+++ Group A Strep, Listeria, oral anaerobes
++ Strep Pneumo, Enterococcus
+   H. Flu, Moraxella, E. coli
---  S. aureus, Gonorrhea
Dicloxacillin
+++ S. aureus, ++ Strep, + Oral anaerobes
--- Gram Negs, MRSA
Amoxicillin/Clavulanic Acid (Augmentin)
+++ Group A Strep, oral anaerobes, H. flu, E. coli, Pasteurella multocida, S. aureus
++ Strep pneumo, Enterococcus
--- resistant Pneumococcus

Cephalosporins SE: GI upset, allergic reaction (5% cross-allergenicity with PCN), yeast infection C. diff colitis
1st Generation: Cephalexin (Keflex)
+++ Group A Strep, Strep pneumo
++  S. aureus, +  H. flu, Moraxella, E. coli
2nd Generation: Cefuroxime, others
+++ H. flu, E. coli, Moraxella
++ Strep pneumo, other Gram (-), GC

Macrolides SE: GI upset, allergic rxn (rare), yeast infxn, C. diff colitis.↑QT interval when combined w/ azoles (anti-fungals). Drug interxns: can increase levels of other drugs by inhibiting p450.
Erythromycin
+++ "Atypicals" (Mycoplasma, Chlamydia, Legionella), Group A Strep, Pertussis
++ Strep pneumo, C. trachomatis,
P. acnes
+ S. aureus, H. Flu, Moraxella
Azithromycin, Clarithromycin (Biaxin)
+++ "Atypicals," Group A Strep, C. trachomatis, Pertussis
++ Strep pneumo, H. flu, Moraxella, S. aureus

Trimethoprim/Sulfamethoxizole
SE: Allergic reaction (rash, Steven’s Johnson Syndrome), GI upset, yeast infxn, C. diff colitis, E. multiforme, Anemia with G-6PD deficiency
+++ E. coli, PCP
++ Strep pneumo, H. Flu, Moraxella, MRSA
--- Group A Strep, anaerobes

Tetracyclines SE: GI upset, photosensitivity rash, allergic rxn, C. diff colitis, yeast infection, bone/teeth discoloration: avoid < 8 yo, pregnant
Doxycycline
+++ C. trachomatis, Lyme, P.Acnes, MRSA, RMSF, "Atypicals" (Mycoplasma, Chlamydia,
Legionella)
++ Strep pneumo, H. Flu, Moraxella

Metronidazole (Flagyl)
SE : disulfiram-like rxn (severe GI upset w/ EtOH), GI upset, metallic taste, allergic rxn
+++ Abdominal/Vaginal Anaerobes, C. difficile, Bact. vaginosis, Trich, Giardia, Ameobiasis
--- Gram Negs, Gram Positives

Clindamycin SE: GI upset, allergic rash, yeast infection,
C. diff colitis
+++ Oral/Vaginal Anaerobes,
S. aureus, Grp A Strep
++ Bacterial vaginosis, Strep pneumo, Trich
--- Gram Negs

Fluoroquinolones
SE: GI upset, allergic rxn (1%), HA, yeast infection, C. diff colitis. Damages developing cartilage: avoid in pregnacy, kids
Cipro/Oflox/Norflox
+++Gram Negs, Pseudomonas
++ Gonorrhea, Enterococcus
+ Strep
--- Anaerobes, "Atypicals" (Mycoplasma, Chlamydia pneumoniae, Legionella)
 Levofloxicin (Levaquin), Gatifloxacin (Tequin)
+++ Gram Negs, Pseudomonas, "Atypicals" (Mycoplasma, Chlamydia pneumoniae, Legionella), Strep pneumo (including resistant strep)
++ Enterococcus
--- Anaerobes, Staph

 

Author(s): Wayne Altman, M.D.
Created: Thursday October 25, 2012
Modified: Monday May 18, 2020

Copyright Information: Copyright 2012, Tufts University

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