Susceptibilities of Haemophilus influenzae, Streptococcus pneumoniae, including serotype 19A, and Moraxella catarrhalis paediatric isolates from 2005 to 2007 to commonly used antibiotics


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Abstract

ObjectivesThe aim of this study was to evaluate susceptibility to common paediatric antibiotics for Streptococcus pneumoniae, non-typeable Haemophilus influenzae and Moraxella catarrhalis isolated from 2005 through 2007.MethodsMicrodilution MIC assays were performed using CLSI-approved methods. S. pneumoniae 19A strains were identified by quellung reaction.ResultsAmong 143 non-typeable H. influenzae, 42% produced β-lactamase. By 2007 breakpoints (PK/PD:CLSI), percentage susceptibility for non-typeable H. influenzae was: ceftriaxone=cefixime=high-dose amoxicillin/clavulanate (all 100%:100%) > standard-dose amoxicillin/clavulanate (91.6%:100%) > cefuroxime axetil (88.1%:99.3%) > cefdinir (83.9%:100%) > trimethoprim/sulfamethoxazole (73.4%:73.4%) >high-dose amoxicillin (58%:58%) > standard-dose amoxicillin (55.2%:58%) > cefprozil (28.7%:83.2%) > cefaclor (3.5%:83.2%) > azithromycin (0%:87.4%). Of 208 S. pneumoniae (42 serotype 19A), 86 were penicillin-susceptible, 60 were penicillin-intermediate and 62 were penicillin-resistant by 2007 CLSI breakpoints. Percentage susceptibility for all S. pneumoniae/19A by PD breakpoints was: ceftriaxone (95.2%/86.1%) > high-dose amoxicillin (89.4%/58.3%) > clindamycin (85%/58.3%) > standard-dose amoxicillin (73.5%/33.3%) > cefuroxime axetil (69.2%/36.1%), cefprozil (67.3%/33.3%) > cefdinir (59.1%/33.3%) > cefixime (57.7%/33.3%) > azithromycin (56.7%/33.3%) > trimethoprim/sulfamethoxazole (50.5%/25%) > penicillin (41.3%/19.4%) > cefaclor (28.8%/8.3%). Percentage M. catarrhalis (n = 62) susceptibility by PK/PD breakpoints was: high-dose amoxicillin/clavulanate = cefixime (100%) > azithromycin (98.4%) > ceftriaxone (96.8%) > standard-dose amoxicillin/clavulanate (88.7%) > cefdinir (80.6%) > cefprozil = cefuroxime axetil (37.1%) > high-dose amoxicillin (11.2%) > cefaclor (6.5%) > standard-dose amoxicillin (4.8%).ConclusionsDespite high rates of β-lactamase production among non-typeable H. influenzae and M. catarrhalis, multiple oral treatment options exist for non-typeable H. influenzae and M. catarrhalis. Multidrug-resistant serotype 19A S. pneumoniae (∼20%) limits treatment options for ambulatory S. pneumoniae respiratory disease.

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