Objective       To investigate the antimicrobial resistance and  serotype   of Haemophilus influenzae (Hi) isolates from the children in Chongqing during the year of 2009 to 2013

and provide instruction for prevention and pharmacological application.       Methods       Antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion method

and serotypes were measured by Hi antiserum.       Results       A total of 5 474 Hi isolates were collected

97.4% (5 329 isolates) were from respiratory samples. All the samples were divided into 4 groups according to the children’s ages

that is

younger than 6 months (group 1)

6 months to 3 years (group 2)

3 years to 5 years (group 3) and older than 5 years (group 4). The positive rate in group 2 (21.8%) and group 3 (16.3%) were significantly higher than that in group 1 (10.3%) and group 4 (6.6%). Among all the 5 474 Hi strains

82.2% were identified from children younger than 5 years old. The resistant rate to trimethoprim-sulfamethoxazole

ampicillin

cefotaxime

ampicillin/sulbactam

levofloxacin was 77.0% 42.4%

0.2 %

2.3% and 0.4%

respectively. There were significant changes  among the resistance rates of trimethoprim-sulfamethoxazole

amoxycillin-clavulanic acid

ampicillin

chloramphenicol

  rifampicin

   cefuroxime

and azithromycin during the investigation period (P0.05). However

the difference of resistance rates of the rest antibiotics had no statistically significance (P0.05). A total of 33 isolates (0.6%) were beta-lactamase negative ampicillin-resistant (BLNAR) Hi. Total 2 282 isolates (41.7%) produced beta-lactamase. Nontypeable Haemophilus influenzae (NTHi) accounted for 92.8% among all Hi strains

and Hia

Hib

Hic

Hid

Hie

and Hif accounted for 5.6%

5.6%

5.6%

27.8%

38.9%

and 16.7% respectively among all serotype of Hi.       Conclusion       Children younger than 5 years old are sensitive population for Hi infection. Most of Hi are isolated from respiratory samples

and trimethoprim-sulfamethoxazole is not suitable for Hi infection. More attention should be paid to resistant Hi

and to survey of antimicrobial resistance in Hi infection. NTHi is the major serotype of Hi

and the Hie is the main serotype.