Using antibiotic concentrations in middle ear fluid to predict potential clinical efficacy.
BACKGROUND
The effectiveness of an antibiotic in eradicating an infection within an anatomic compartment is related to both its availability (penetration) and the susceptibility of the causative pathogen. Antimicrobial penetration can be assessed by measuring concentrations in serum or tissue. However, to assess antibiotic effectiveness in the treatment of otitis media, both antibiotic concentrations and pathogen profiles in middle ear fluid (MEF) should be considered. Tympanocentesis is required to access fluid in the middle ear compartment. This paper considers data on (MEF) antibiotic concentrations obtained with this procedure.


METHODS
Data on MEF antibiotic concentrations were considered in relation to the antibiotic susceptibility profiles of the more common otitis media pathogens.


RESULTS
Amoxicillin reaches MEF concentrations that exceed MICs for penicillin-susceptible and penicillin relatively resistant Streptococcus pneumoniae, but not for beta-lactamase-producing Haemophilus influenzae. Several beta-lactamase-stable drugs, e.g. cefixime and amoxicillin/clavulanate, however, achieve MEF concentrations that easily exceed their respective MIC90s for both beta-lactamase-producing and nonproducing H. influenzae but at ordinary doses may not exceed MIC90s for penicillin relatively resistant S. pneumoniae.


CONCLUSIONS
Ongoing observation of organisms and their antibiotic resistance patterns in patients failing initial therapy of acute otitis media indicate that stability to beta-lactamase remains an essential quality for effective second line therapies. However, when possible tympanocentesis with culture is the ideal method of targeting specific therapy for patients failing multiple consecutive antibiotic regimens.
Harrison
C J
CJ
Department of Pediatrics, Creighton University, Omaha, NE 68178, USA.
D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D002648:Child; D004352:Drug Resistance, Microbial; D005122:Exudates and Transudates / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010034:Otitis Media with Effusion / Q000188:drug therapy* / Q000378:metabolism* / Q000382:microbiology
D000900:Anti-Bacterial Agents