| Objectives To investigate the infection characteristics and antibiotics resistance of Haemophilus influenzae (Hi) isolated from children with acute respiratory tract infection (ARI) in Chongqing during 2006-2009, we measured out drug resistence of Hi and analyzed the correlation betweenβ-lactam antibiotics resistence and the variable promoters of blaTM-1 gene.Methods The durg resistence of clinical isolates Hi from January 2006 to December 2009 were collected and analyzed. Among them, 99 Hi strains which exhibit blaTM-1 PCR-positive were picked out for further analysis of the diversity in blaTM-1 and relativeβ-lactamases antibiotics resistence.Results 1967 Hi were identified from 13842 children with ARI,and the positive rate of Hi was 14.2% . Among all the 1967 Hi, 95.5% were identified from children no more than 5 years old. Beside Hi, 40.3%patients suffered multi-dacteria infenction. The rate of beta-lactamase producing was 35.8% and mainly distributed in groups younger than 5 years old. Less than 10% of the isolates were resistant to amoxicillin/clavulanic acid, cefotaxime, ceftriaxone, cefuroxime, azithromycin, rifadin and ciprofloxacin. Whereas, the resistant rates in SXT, ampicillin, tetracycline and chloramphenicol are 69.0%-77.4%, 31.8%-40.0%, 31.8%-36.0%, 18.7%-22.7% respectively during 2006-2009. Up to 30.0% of Hi were multidrug-resistant, and 74.1% of them can be divided into eight common resistant phenotypes. Among of them, SXT (31.1%-34.5%) is the largest percentage, Amp-SXT-CHL-TET (12.6%-19.3%) is followed and ampicillin resistant Hi most case combined withβ-lactamase positive phenotypes. Theβ-lactamases of 97 Hi isolates were all blaTEM-1, no blaROB-1. Two other stains were blaTEM-1 gene PCR-positive, but nitrocefin-negative. The length of blaTEM-1 in most isolates (74.7%) was not as the expected classical 1075bp. The main diversity of blaTEM-1 among these was not in the coding regions, but in the promoter regions. Therefore, blaTEM-1 promoter regions were categorized into 6 types designated as Pdel, Pa/Pb, P4, Prpt.b, 2Prpt, P3.b according to SSCP-sequence analysis. Our data first provide evidence that the promoter P4 appears in blaTEM-1 in Hi isolates. Among promoter P4 positive Hi strains, 6 (6/7) contain A182C mutation. Of all the 99 isolates, promoter Pdel (53.5%), the 135bp deletion, promoter Prpt.b (18.2%), the repeat 54bp insertion with G175A mutation and promoter Pa/Pb (17.2%) with G175A mutation are the three major promoter types. Significantly, strains with higher MICs (MICs≥128μg/ml) for ampicillin belong to the following promoter types: Pdel.a (47.2%), Prpt.b (28.0%), and Pa/Pb (13.2%). In addition, strains with higher MICs (MICs≥128μg/ml) for cefprozil were mainly harboring the promoter Pdel.a.Conclusion1. Children no more than 5years old is Hi infection sensitive population, especially in lower immunity.2. Ampicillin resistance caused byβ-lactamase decode by blaTEM-1 is the dominant mechanism resistance in Chongqing.3. blaTEM-1 gene in Hi can be categorized into 6 types according to promoter polymorphism, and Pdel.a, Prpt.b, and Pa/Pb are 3 major promoters.4. Pdel.a in promoter region of blaTEM-1 may confer Hi more capability to produceβ-lactamase thereby more against ampicillin and cefprozil.
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