Non-susceptibility trends among Haemophilus influenzae and Moraxella catarrhalis from community-acquired respiratory tract infections in the UK and Ireland, 1999-2007.
OBJECTIVE
To determine the antimicrobial susceptibility of Haemophilus influenzae and Moraxella catarrhalis causing community-acquired respiratory tract infections in the UK and Ireland from 1999/2000 to 2006/07.


METHODS
Sentinel laboratories across the UK and Ireland contributed up to a fixed quota of isolates of defined organisms per annum. A central laboratory confirmed the isolates' identities, measured MICs by the BSAC agar dilution method and undertook further testing by standard methods. The variability of the MIC method was assessed by repeated annual testing of control isolates. BSAC and EUCAST breakpoints were used. Statistical analysis adjusted for inter-centre variation by random effects logistic regression.


RESULTS
A total of 7371 H. influenzae and 2529 M. catarrhalis isolates were investigated. Over 90% of the H. influenzae isolates were susceptible to most of the antimicrobials tested, the exceptions being ampicillin (84.6% susceptible), trimethoprim (84.0%), cefuroxime (82.9%), amoxicillin (77.2%) and cefaclor (11.7%). For M. catarrhalis, resistance was solely due to beta-lactamase (prevalence over 91%) reducing susceptibility to penicillins only. There was little evidence of decreased antimicrobial susceptibility between 1999 and 2007 in either pathogen, except for a reduction in susceptibility to trimethoprim in H. influenzae (90.3% to 82.6%, P < 0.00001). On the other hand, tetracycline susceptibility in H. influenzae increased over this period in the UK and Ireland (96.5 to 98.8%, P = 0.00008).


CONCLUSIONS
Despite increased resistance in respiratory pathogens from other parts of the world, the susceptibility of H. influenzae and M. catarrhalis to all agents, except tetracycline and trimethoprim in the case of H. influenzae, has remained constant during this longitudinal study.
Morrissey
Ian
I
Quotient Bioresearch Limited, Microbiology, 7-9 William Road, London NW1 3ER, UK. ian.morrissey@quotientbioresearch.com
Maher
Kirsty
K
Williams
Laura
L
Shackcloth
Jemma
J
Felmingham
David
D
Reynolds
Rosy
R
D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D005260:Female; D006192:Haemophilus Infections / Q000382:microbiology*; D006193:Haemophilus influenzae / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007494:Ireland; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D001936:Moraxella catarrhalis / Q000187:drug effects* / Q000302:isolation & purification; D045828:Moraxellaceae Infections / Q000382:microbiology*; D012141:Respiratory Tract Infections / Q000382:microbiology*; D018571:Sentinel Surveillance; D006113:United Kingdom
D000900:Anti-Bacterial Agents