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September 1995

Therapeutic Implications in the Treatment of Aural Pseudomonas Infections Based on In Vitro Susceptibility Patterns

Author Affiliations

From the Department of Otolaryngology, Division of Pediatric Otolaryngology (Drs Dohar and Kenna), and the Department of Pathology (Dr Wadowsky), University of Pittsburgh (Pa) School of Medicine, and the Departments of Pediatric Otolaryngology (Drs Dohar and Kenna) and Pathology (Dr Wadowsky), Children's Hospital of Pittsburgh.

Arch Otolaryngol Head Neck Surg. 1995;121(9):1022-1025. doi:10.1001/archotol.1995.01890090060012

Objective:  To examine the in vitro susceptibility patterns of aural isolates of Pseudomonas aeruginosa and to identify changes over a 4-year period.

Design:  Retrospective case series.

Setting:  The outpatient department at Children's Hospital of Pittsburgh (Pa), a tertiary referral center.

Patients:  Ambulatory children younger than 18 years from whose ears P aeruginosa was isolated.

Outcome Measures:  The in vitro susceptibility of aural isolates of P aeruginosa to ampicillin, cefotaxime, chloramphenicol, sulfisoxazole, ticarcillin, mezlocillin, gentamicin, tobramycin, cefazolin, tetracycline, piperacillin, nitrofurantoin, cephalexin hydrochloride, ceftriaxone, cefuroxime axetil, and sulfamethoxazole-trimethoprim.

Results and Conclusions:  No changes were found in the trends of the susceptibility patterns over the 4-year study period, with the exception of the semisynthetic penicillins, ticarcillin and mezlocillin. These two agents were found to be relatively ineffective against the strains of P aeruginosa isolated in 1989 (59% and 18% susceptibility, respectively). This finding is in contrast to their effectiveness over the remainder of the study period (96% and 90% susceptibility, respectively), which was excellent. These observations likely reflect a change in the breakpoints for the minimal inhibitory concentrations between these periods. The intravenous agent with the best susceptibility profile was piperacillin (96%). Of the aminoglycosides tested, 94% of the isolates were sensitive to tobramycin, as opposed to only 79% for gentamicin. This finding may have significance when one is empirically selecting ototopical therapy, since both tobramycin and gentamicin are available as topical preparations. Of the oral agents, the combination of sulfamethoxazole-trimethoprim was most effective (46%).(Arch Otolaryngol Head Neck Surg. 1995;121:1022-1025)

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