ABSTRACT
Objective To establish a bioiflm (BF) models of Haemophilus inlfuenza in vitro, and to observe the changes of antibiotic susceptibility after the BF fromation. Methods Thirty strains Haemophilus inlfuenzae isolated from adenoids of children with adenoidal hypertrophy and cultured in a 96-well plate. The BF was identiifed by crystal violet staining and scanning electron microscopy (SEM). The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and the minimum bioiflm bacteria bioiflm clear concentration (MBEC) of ampicillin (AMP), ceftriaxone (CRO), levolfoxacin (LVFX) and azithromycin (AZM) were individually detected. Result All of 30 strains of Haemophilus inlfuenzae formed various BF. After BF is formed, the increase of MBEC for different antibiotics was inconsistent with the increase of MIC and MBC. The difference was statistically signiifcant (MBEC/MBC, H=91.54;MBEC/MIC, H=87.91;all P<0.001). The MBEC of AMP was the highest, up to 100 times than the MBC and MIC. The MBEC of CRO was dozens of times than the MBC and MIC. The MBEC of LVFX and AZM were most close to those of MBC and MIC. Conclusion After the formation of BF, resistance to antibiotics of Haemophilus inlfuenzae is enhaced. LVFX and AZM showed more favorable effect on Haemophilus infuenzae BF.
ABSTRACT
Objectives To investigate the changes and features of drug resistance in Haemophilus inlfuenzae (Hi) isolated from children with infection diseases in Suzhou. Methods One thousand two hundred and twenty-two Hi strains isolated from clinical specimens were collected from January 2011 to June 2012. Antimicrobial susceptibility was tested by Kirby-Bauer me-thod, andβ-lactamase was analyzed by chromogenic nitroceifn method. Then strains were divided into four groups according to their speciifc resistance patterns:①β-lactamase positive strains (except for cefuroxime-resistant strains),②β-lactamase negative ampicillin-resistant (BLNAR) strains,③cefuroxime-resistant strains, and④other resistant strains. Results The resistance of iso-lated Hi from children in Suzhou area to ampicillin, co-trimoxazole, cefaclor, tetracycline, chloramphenicol, azithromycin, cefu-roxime, ampicillin/sulbactam was 32.7%, 76.7%, 27.4%, 14.3%, 10.2%, 8.4%, 6.9%and 4.3%, respectively, and the detection rate in four groups was 29.0%, 2.6%, 6.9%, 41.2%, respectively. Multi-resistant strains were mainly distributed in Group①and Group②, accounting for 67.5%and 81.3%of each group. Azithromycin, tetracycline and chloramphenicol showed high antimicrobial activity against BLNAR and cefuroxime-resistant Hi strains. The positive rate of resistance toβ-lactamase was 30.8%. The rates of resistance to cefuroxime, cefaclor, ampicillin/sulbactam and cotrimoxazole inβ-lactamase-positive ampicillin-resistant strains are signiifcantly different from those inβ-lactamase-negative ampicillin-resistant strains. Conclusions The resistance feature of Hi isolated from children in Suzhou shows signiifcant changes, including new appearance of cefuroxime-resistant strain, a rapid increase in resistance to azithromycin, and a large proportion of multidrug-resistant strains. The rapid increase in BLNAR and the emergence of cefuroxime-resistant strains have become the new resistance pattern of Hi in this area.