Antibiotic resistance of Haemophilus influenzae isolated in invasive and non-invasive forms of children's infections in Ural region

Abstract number: P2055

Boronina L., Lavrinenko E.

Objectives: Antibiotic resistance of Haemophilus influenzae strains is a big problem in many countries. The purpose of the current study is to determine the distribution frequency of different phenotypes antibiotic resistance of H. influenzae (HI) strains isolated from children with different localisation infections from 1991 to 2006 in Ural Region.

Methods: 268 non-typing HI strains obtained from clinical materials of children with the upper and lower respiratory tract inflammatory diseases, otitis media, sinusitis and 8 HI serotype "b" strains isolated from liquor and blood by osteomyelitis, meningitis and sepsis were studied for their antibiotic susceptibility. Antibiotic susceptibility was tested on Haemophilus Test Medium with the disk diffusion method (the results were checked with criteria NCCLS-CLSI) and test-systems ATB NH and ATB Haemo (ATB Expression, bioMerieux, France). Beta-lactamase was detected with chromogenic cephalosporin (cefinase-bioMerieux, France).

Results: 187 strains from 268 non-typing strains were tested to ampicillin. Only 148 (79.14%) strains from the tested 187 ones were susceptible, 15 (8.06%) were intermediate, 24 (12.8%) were resistant. Beta-lactamase was detected at 5.1% strains. It was the first time in 2003, when b-lactamase-negative ampicillin-resistant (BLNAR) 5 strains and b-lactamase-negative ampicillin-intermediate (BLNAI) 2 strains were revealed, that made 2.5% and 1% accordingly among the strains isolated from 2000 to 2005. 99 strains were tested to amoxycillin-clavulanate only 5 (5.05%) from them were resistant. 219 strains were tested to cephalosporin of the second generation only 7 (3.21%) from them were resistant. All strains were susceptible to cephalosporin of the third and fourth generation. 165 strains were tested to fluoroquinolone only 2 (1.21%) from them were resistant.

HI serotype "b" strains which had no b-lactamase were susceptible to ampicillin, amoxycillin-clavulanate, cefuroxime, cefaclor, ofloxacin, rifampicin and chloramphenicol.

Conclusion: HI serotype "b" susceptibility did not change. But resistance of non-typing HI strains changed for the investigated period: ampicillin resistance went up to 13%, resistance to amoxycillin-clavulanate and cephalosporin of the second generation appeared 5% and 3% accordingly, b-lactamase was revealed at 5.1% strains. 2.5%b-lactamase-negative ampicillin-resistant strains were revealed.