International Journal of Microbiology and Immunology Research Vol. 3(6), pp. 084-089, October 2015 ISSN 2327-7769 ©2015 Academe Research Journals

Full Length Research Paper

Haemophilus influenzae strains in children: Increasing resistance to Beta-lactam antibiotics

Sabrine MZILEM*, Sonia KSIAA, Hanen SMAOUI and Amel KECHRID

Microbiological Laboratory, Faculty of Medicine, Children’s Hospital of Tunis, Tunisia.

*Corresponding author. E-mail: mzilem.sabrine@gmail.com. Tel: 00216 22 305 800.

ABBREVIATIONS: AMC: amoxicillin-clavulanate; AMP: ampicillin; β-lactam: Beta-lactam; BLNAR: β-lactamase negative ampicillin resistant strains; BLPACR: β-lactamase positive amoxicillin-clavulanate resistant strains; BLPAR: β-lactamase positive ampicillin resistant strains; CTX: cefotaxime; GM: gentamicin; H.i: Haemophilus influenzae; K: kanamycin; MIC: minimum inhibitory concentration; NAL: nalidixic acid; NTHi: non-typable Haemophilus influenzae; PBP3: penicillin binding protein 3; PCR: polymerase chain reaction; RA: rifampin.

Accepted 29 October, 2015

Abstract

The aim of this study was to determine the bacteriological characteristics of Haemophilus influenzae (Hi) strains isolated from children, namely serotyping, biotyping and their antibiotic susceptibilities specifying the mechanisms and the β-lactams resistance genes. This study made use of 138 Hi strains isolated from 2009 to 2010 at the Microbiological Laboratory of the Children’s Hospital in Tunisia. Antimicrobial susceptibility for all Hi isolates was determined as recommended by the CA-SFM (Comité de l'antibiogramme de la Société Française de Microbiologie). Beta-lactam resistance genes (bla_TEM,, bla_ROB and ftsI) were detected by PCR (Polymerase Chain Reaction) as well as their capsular genes (bexA). Ampicillin resistance was 44.92% (62/138) of Hi isolates. PCR showed that all of the strains were identified as non-capsulated. These isolates were subdivided into 3 groups according to the ampicillin resistance molecular mechanisms as follows: the group of β-lactamase positive ampicillin resistant isolates (BLPAR) (22.4%), the group of the β-lactamase negative ampicillin resistant strains (BLNAR) (18.1%) and finally the group of the β-lactamase positive amoxicillin-clavulanate resistant strains (BLPACR) (4.3%). All isolates showed high amoxicillin, cefuroxime and imipenem MICs (Minimum Inhibitory Concentration). Among these, the less active one was imipenem.  However, cefotaxime, cefixime and cefpodoxime were the most active agents tested against our strains. Finally, we confirmed the dissemination of BLNAR and BLPACR Hi strains with incremental increases in beta-lactam resistance. These strains were previously rare in Tunisia.

Key words: Beta-lactams resistance, Haemophilus influenzae, polymerase chain reaction (PCR).