Abstract
Background. Moraxella catarrhalis is an important bacterial pathogen. Although national data have shown an increase in the levels of antimicrobial resistance in clinical settings in Lebanon, there is a lack of data regarding this human pathogen. This study aimed to determine for the first time the antimicrobial susceptibility profiles of M. catarrhalis isolates in Lebanon.
 Methods. A total of 34 M. catarrhalis strains were isolated from clinical specimens during the period from November 2010 to March 2019. Bacterial identification was carried out using matrix assisted laser desorption ionization–time of flight mass spectrometry. Antibiotic susceptibility of all isolates was performed according the recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST).
 Results. A total of 34 non-duplicated M. catarrhalis strains were isolated from nose (n=19), ear (n=7), sputum (n=5), blood (n=1), eye (n=1), and throat (n=1) of patients referred to Nini Hospital in Tripoli, North governorate of Lebanon. Regarding antibiotic susceptibility rates, the percent susceptibility is 100% to the majority of antibiotics, except ampicillin (7.4%), trimethoprim-sulfamethoxazole (85.3%), nalidixic acid (85.3%), and ciprofloxacin (97.1%).
 Conclusion. To our knowledge, this study is the first investigation regarding the antimicrobial susceptibility patterns of M. catarrhalis isolates in Lebanon. In addition to the high level of resistance to ampicillin, our findings showed the emergence of resistance to trimethoprim-sulfamethoxazole, nalidixic acid and ciprofloxacin. Even if this study provides useful information to develop effective empirical treatment, we recommend the implementation of reliable diagnostic tools to guide appropriate treatment.
Highlights
Moraxella catarrhalis is an aerobic Gram-negative diplococcus, formerly known as Branhamella catarrhalis, that resides exclusively in humans, and commensally colonizes the mucosal surface of the upper respiratory tract, and occasionally the conjunctiva and genital tract [1]
A total of 34 non-duplicated M. catarrhalis strains were isolated from patients referred to Nini Hospital in Tripoli, Lebanon
In addition to the high level of resistance to ampicillin, our findings showed the emergence of resistance to trimethoprimsulfamethoxazole, nalidixic acid and ciprofloxacin
Summary
Moraxella catarrhalis is an aerobic Gram-negative diplococcus, formerly known as Branhamella catarrhalis, that resides exclusively in humans, and commensally colonizes the mucosal surface of the upper respiratory tract, and occasionally the conjunctiva and genital tract [1]. The highest prevalence of colonization was detected among infants and children, which decreased in healthy adults [2] The role of this bacterium as a disease-causing organism has long been questioned. Two major resistance mechanisms have been described in M. catarrhalis: the inactivation of antimicrobials by enzymes such as β-lactamases and the decrease in permeability of bacterial cell wall (reducing in the number of porins and/or enhancement of the active efflux system) [1]. We decided to assess for the first time the antimicrobial resistance patterns in M. catarrhalis strains isolated in North Lebanon. This study aimed to determine for the first time the antimicrobial susceptibility profiles of M. catarrhalis isolates in Lebanon
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