Moraxella catarrhalis AcrAB-OprM Efflux Pump Contributes to Antimicrobial Resistance and Is Enhanced during Cold Shock Response

Abstract

bMoraxella catarrhalis is a common pathogen of the human respiratory tract. Multidrug efflux pumps play a major role in antibiotic resistance and virulence in many Gram-negative organisms. In the present study, the role of the AcrAB-OprM efflux pump in antibiotic resistance was investigated by constructing mutants that lack the acrA, acrB, and oprM genes in M. catarrhalis strain O35E. We observed a moderate (1.5-fold) decrease in the MICs of amoxicillin and cefotaxime and a marked (4.7-fold) decrease in the MICs of clarithromycin for acrA, acrB, and oprM mutants in comparison with the wild-type O35E strain. Exposure of the M. catarrhalis strains O35E and 300 to amoxicillin triggered an increased transcription of all AcrAB-OprM pump genes, and exposure of strains O35E, 300, and 415 to clarithromycin enhanced the expression of acrA and oprM mRNA. Inactivation of the AcrAB-OprM efflux pump genes demonstrated a decreased ability to invade epithelial cells compared to the parental strain, suggesting that acrA, acrB, and oprM are required for efficient invasion of human pharyngeal epithelial cells. Cold shock increases the expression of AcrAB-OprM efflux pump genes in all three M. catarrhalis strains tested. Increased expression of AcrAB-OprM pump genes after cold shock leads to a lower accumulation of Hoechst 33342 (H33342), a substrate of AcrABOprM efflux pumps, indicating that cold shock results in increased efflux activity. In conclusion, the AcrAB-OprM efflux pump appears to play a role in the antibiotic resistance and virulence of M. catarrhalis and is involved in the cold shock response. Moraxella catarrhalis colonizes the mucosal surface of the human nasopharynx and is a major cause of acute otitis media in children and of exacerbations of chronic obstructive pulmonary disease in adults (1-4). The proportion of cases of acute otitis media caused by M. catarrhalis varies between 5% and 20%, with recent studies showing a relative increase in M. catarrhalis-caused otitis media since the introduction of routine infant immunization with the pneumococcal conjugate vaccine (2, 4-6). Furthermore, clinical studies revealed that the prevalence of pharyngeal colonization and respiratory tract infections caused by M. catarrhalis displays seasonal variation and increases in winter (7-10). The human nasopharyngeal flora is recurrently exposed to rapid downshifts of environmental temperature. Breathing cold air (e.g., Ϫ1°C at 10 to 20 liters/min) reduces the nasopharyngeal temperature from 34°C at room temperature to about 26°C within several minutes and for extended periods (11). Such rapid variation of temperature induces adaptive events in the residential upper respiratory tract flora that may contribute to the transition from asymptomatic colonization to infection. Our previous in vitro studies demonstrated that a 26°C cold shock upregulates the expression of important virulence traits, such as adherence to epithelial cells, iron acquisition, complement resistance, and immune evasion (12)(13)(14).Adaptive resistance also...

Transcriptomic Analysis of Laribacter hongkongensis Reveals Adaptive Response Coupled with Temperature

“…For instance, increased efflux activity of Pseudomonas fluorescens ( P . fluorescens ) [71] and Moraxella catarrhalis [72] were measured at cooler temperature, suggesting the generosity of temperature-induced efflux pumps expression and activity. In L .…”

Contributions of TolC Orthologs to Francisella tularensis Schu S4 Multidrug Resistance, Modulation of Host Cell Responses, and Virulence

“…Bacterial pathogens have evolved various mechanisms to counteract the harmful effects of antimicrobial compounds, including the use of multidrug efflux systems (28,29). Multidrug efflux systems reliant on TolC orthologs are conserved across bacteria and contribute to bacterial virulence (29,(51)(52)(53)(54). Previous work identified roles for all three TolC orthologs in resistance of the F. tularensis LVS to a variety of antibiotics and other toxic chemicals (30,38).…”

Compartmentalized Encapsulation of Two Antibiotics in Porous Nanoparticles: an Efficient Strategy to Treat Intracellular Infections

“…Amoxicillin (AMOX) and potassium clavulanate (CL) are typical examples of drugs used in tandem to treat a variety of bacterial infections, mainly rhinosinusitis, ear infections, pharyngolaryngitis, tonsillitis, bronchitis, and urinary tract infections . However, these polar drugs are poorly permeable across the cell membranes and they lack efficacy in intracellular infections …”

“…[7,8] However, these polar drugs are poorly permeable across the cell membranes and they lack efficacy in intracellular infections. [9][10][11] There are still scarce examples of NPs engineered for the coincorporation of antibiotics. [12][13][14][15][16] Nevertheless, the preparation methods of these drug carriers generally are complex and require the use of organic solvents and surfactants.…”