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Resistance pattern of middle ear fluid isolates in acute otitis media recently treated with antibiotics
E Leibovitz1, S Raiz, L Piglansky
1Pediatric Infectious Disease Unit, Soroka University Medical Center and the Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Background:
Little information is available about the effect of antibiotic treatment on the prevalence and MIC of the subsequently isolated pathogens in cases of acute otitis media (AOM) failing a course of antibiotic therapy. This information is important, particularly regarding the effectiveness of the oral antibiotics used in children failing initial therapy.
Patients And Methods:
One hundred eighty-one children with culture-positive AOM were prospectively studied between October, 1995, and July, 1996. Sixty-three (35%) patients received various antibiotics for variable periods during the 14 days preceding enrollment.
Results:
A total of 94 Streptococcus pneumoniae (Pnc) and 113 Haemophilus influenzae (Hi) were isolated. Thirty-eight Pnc and 35 Hi were isolated in the 63 patients with recently treated AOM. Pnc as a single isolate was more prevalent in patients recently treated with antibiotics (27 of 63, 43%) than among those not recently treated (32 of 118, 27%, P = 0.047). The MIC50 values of penicillin, cefaclor and cefuroxime axetil for Pnc were significantly higher in the pneumococci isolated from patients recently treated than among those isolated from patients not recently treated with antibiotics (0.38, 3 and 0.75 microg/ml vs. 0.094, 0.38 and 0.12 microg/ml, respectively). Seventy-nine percent of Pnc isolates in the recently treated group had MIC for penicillin of >0.1 microg/ml vs. only 47% in those not recently treated (P < 0.05). The respective figures for MIC >0.5 microg/ml of cefaclor were 79% vs. 41% for the recently treated and not recently treated groups (P < 0.001); cefuroxime MIC >0.5 microg/ml was found in 61 and 25%, respectively (P = 0.001).
Conclusions:
Pneumococcus is more prevalent in AOM after a recent antibiotic treatment, and the MIC of the commonly used beta-lactam drugs for Pnc is considerably higher in this setting. In view of our data, the use of oral cephalosporins like cefaclor or cefuroxime as second line drugs in the treatment of unresponsive AOM, particularly in regions where resistant PNC is prevalent, should be reconsidered.
Insights
Recent antibiotic use increases Streptococcus pneumoniae prevalence in acute otitis media (AOM). This leads to higher minimum inhibitory concentrations (MIC) for common antibiotics, questioning the effectiveness of second-line treatments.
Area of Science:
- Pediatric Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Limited data exists on antibiotic impact on pathogen prevalence and MIC in treatment-failure acute otitis media (AOM).
- Understanding this is crucial for selecting effective oral antibiotics for children with persistent AOM.
Purpose of the Study:
- To investigate the effect of recent antibiotic treatment on pathogen prevalence and antibiotic susceptibility in AOM.
- To inform antibiotic selection for refractory AOM cases.
Main Methods:
- Prospective study of 181 children with culture-positive AOM.
- Analysis of pathogen isolation and minimum inhibitory concentration (MIC) in children with and without recent antibiotic exposure (within 14 days).
Main Results:
- Streptococcus pneumoniae (Pnc) was more prevalent in recently treated AOM patients (43%) compared to untreated (27%).
- Higher MIC50 values for penicillin, cefaclor, and cefuroxime axetil were observed for Pnc isolated from recently treated patients.
- A significant increase in Pnc isolates with high MICs for penicillin and cephalosporins was found in the recently treated group.
Conclusions:
- Recent antibiotic treatment is associated with increased Pnc prevalence and reduced susceptibility to beta-lactam antibiotics in AOM.
- The efficacy of oral cephalosporins (cefaclor, cefuroxime) as second-line AOM therapy may be compromised in settings with prevalent resistant Pnc.