Respiratory infections caused by Haemophilus influenzae β-lactamase positive carrying blaTEM gene

Abstract Introduction One of the main etiological agents of respiratory infections is H. Influenzae. The group of antibiotics most used to the treatment of H. influenzae infections is β-lactams. The most common β-lactam resistance is to ampicillin, characterized by the production of TEM (95%) and ROB (5%) β-lactamases, designated enzymatic resistance. Objectives Characterize the susceptibility profile of H. influenzae to β-lactam antibiotics, to evaluate the enzymatic resistance by the β-lactamase production and to correlate the phenotypic profile with the presence of the blaTEM. Methodology Total of 152 isolates of H. influenzae from respiratory infections were evaluated: 88 from expectorations, 56 from bronchial aspirates and 8 from bronchoalveolar lavage, collected in Clinical Pathology Service of Centro Hospitalar e Universitário de Coimbra. The results of the antimicrobial susceptibility profile and the β-lactamase screening were also provided. In order to investigate the blaTEM, DNA was extracted from the isolates and the detection was performed using the PCR technique. Results The prevalence of the blaTEM in the isolates was 31.6%, of these 33.3% showed resistance to ampicillin and 57.9% were positive in β-lactamase activity screening and blaTEM carriers. There was a statistically significance between the presence of the gene with ampicillin resistance and β-lactamase activity screening. Conclusion β-lactamase TEM production was the main mechanism of enzymatic resistance which demonstrates the high spread of the blaTEM among isolates of H. influenzae. The results found suggest that the negative strains for this β-lactamase but that presented β-lactamases with activity and resistance to β-lactams should have other β-lactamases as ROB or others. However strains with β-lactamase negative should have other mechanisms promoting the resistance as PBP3. This study provides important data on the antibiotic therapy, to minimize the expression of resistance mechanisms and problems associated with treatment.