You are here: Home Research Themes Antimicrobial Resistance

Antimicrobial Resistance

Article Reference A chalcone with potent inhibiting activity against biofilm formation of nontypeable Haemophilus influenzae.
Nontypeable Haemophilus influenzae (NTHi) is an important human respiratory pathogen and this bacterium frequently causes biofilm infections. Resistance to conventional antimicrobials of bacteria within the biofilm poses a major difficulty in current medical treatment on a global scale. Novel agents that are effective against NTHi biofilm are therefore required and in an urgent need. In this study, a series of natural and synthetic chalcones with various chemical substituents were evaluated in vitro for their antibiofilm activities against strong biofilm-forming strains of NTHi. Of the test chalcones, 3-hydroxychalcone (chalcone 8) exhibited the most potent inhibitory activity, with mean minimum biofilm inhibitory concentration (MBIC50 ) value of 16 μg/mL (71.35 μM), or approximately 6-fold more active than azithromycin (MBIC50 419.68 μM), the reference drug. The inhibitory activity of chalcone 8 which was a chemically modified chalcone, appeared to be superior to those of natural chalcones tested. Significantly, chalcone 8 effectively inhibited biofilm formation of all studied NTHi strains. This indicated that antibiofilm activities of such compound occurred across multiple strong-biofilm forming NTHi isolates of different clinical origins. As examined by antimicrobial and growth curve assays, chalcone 8 at concentration that decreased biofilm formation did not affect growth of NTHi, suggesting a non-antimicrobial biofilm inhibitory effect of chalcone 8. In terms of structure-activity relationship, the potential substituent on the chalcone backbone required for antibiofilm activity was discussed. These results indicated the powerful antibiofilm action of 3-hydroxychalcone (chalcone 8) and suggested the potential application of chalcone 8 as a new therapeutic agent for control of NTHi biofilm-associated infections.
Article Reference Molecular epidemiology of nontypeable Haemophilus influenzae causing community-acquired pneumonia in adults.
Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen which causes a variety of respiratory infections. The objectives of the study were to determine its antimicrobial susceptibility, to characterize the β-lactam resistance, and to establish a genetic characterization of NTHi isolates. Ninety-five NTHi isolates were analyzed by pulsed field gel electrophoresis (PFGE) and multi locus sequence typing (MLST). Antimicrobial susceptibility was determined by microdilution, and the ftsI gene (encoding penicillin-binding protein 3, PBP3) was PCR amplified and sequenced. Thirty (31.6%) isolates were non-susceptible to ampicillin (MIC ≥ 2 mg/L), with 10 of them producing β-lactamase type TEM-1 as a resistance mechanism. After ftsI sequencing, 39 (41.1%) isolates showed amino acid substitutions in PBP3, with Asn526 → Lys being the most common (69.2%). Eighty-four patients were successfully treated with amoxicillin/clavulanic acid, ceftriaxone and levofloxacin. Eight patients died due either to aspiration or complication of their comorbidities. In conclusion, NTHi causing CAP in adults shows high genetic diversity and is associated with a high rate of reduced susceptibility to ampicillin due to alterations in PBP3. The analysis of treatment and outcomes demonstrated that NTHi strains with mutations in the ftsI gene could be successfully treated with ceftriaxone or fluoroquinolones.
Article Reference Relative contributions of lipooligosaccharide inner and outer core modifications to nontypeable Haemophilus influenzae pathogenesis.
Nontypeable Haemophilus influenzae (NTHi) is a frequent commensal of the human nasopharynx that causes opportunistic infection in immunocompromised individuals. Existing evidence associates lipooligosaccharide (LOS) with disease, but the specific and relative contributions of NTHi LOS modifications to virulence properties of the bacterium have not been comprehensively addressed. Using NTHi strain 375, an isolate for which the detailed LOS structure has been determined, we compared systematically a set of isogenic mutant strains expressing sequentially truncated LOS. The relative contributions of 2-keto-3-deoxyoctulosonic acid, the triheptose inner core, oligosaccharide extensions on heptoses I and III, phosphorylcholine, digalactose, and sialic acid to NTHi resistance to antimicrobial peptides (AMP), self-aggregation, biofilm formation, cultured human respiratory epithelial infection, and murine pulmonary infection were assessed. We show that opsX, lgtF, lpsA, lic1, and lic2A contribute to bacterial resistance to AMP; lic1 is related to NTHi self-aggregation; lgtF, lic1, and siaB are involved in biofilm growth; opsX and lgtF participate in epithelial infection; and opsX, lgtF, and lpsA contribute to lung infection. Depending on the phenotype, the involvement of these LOS modifications occurs at different extents, independently or having an additive effect in combination. We discuss the relative contribution of LOS epitopes to NTHi virulence and frame a range of pathogenic traits in the context of infection.
Article Reference A prospective, observational, epidemiological evaluation of the aetiology and antimicrobial susceptibility of acute otitis media in Saudi children younger than 5years of age.
Information regarding acute otitis media (AOM) aetiology is important for developing effective vaccines. Here, bacterial aetiology and antimicrobial susceptibility of AOM were determined in young Saudi children.
Article Reference Oropharyngeal colonization by nontypeable Haemophilus influenzae among healthy children attending day care centers.
Haemophilus influenzae colonizes the upper respiratory tract and can spread causing otitis and sinusitis. This work aimed to study the oropharyngeal carriage rate in healthy <5-year-old children attending day care centers in Oviedo, Spain in two consecutive years (January to March 2004-2005). The carriage rate was 42% (400/960) and highly variable among centers (range, 12% to 83%). Isolates were mainly identified as nontypeable H. influenzae (NTHi, 99%). Epidemiologically, 127 different genotypes were identified by PFGE with a minimum of two genotypes per center. One hundred fourteen children (12%) were included in both studies and none of them harbored the same strain over a period of time. The isolates only showed resistance to cotrimoxazol and ampicillin, presenting a shift in the level of ampicillin reduced susceptibility, showing a predominance of PBP3 mutations in 2004 and a predominance of β-lactamase production in 2005. This study proved the great genetic variability of NTHi isolates that present similar genotypic patterns in both years with no long-term carriage of the same strain.
Article Reference Characterization of lactate utilization and its implication on the physiology of Haemophilus influenzae.
Haemophilus influenzae is a Gram-negative bacillus and a frequent commensal of the human nasopharynx. Earlier work demonstrated that in H. influenzae type b, l-lactate metabolism is associated with serum resistance and in vivo survival of the organism. To further gain insight into lactate utilization of the non-typeable (NTHi) isolate 2019 and laboratory prototype strain Rd KW20, deletion mutants of the l-lactate dehydrogenase (lctD) and permease (lctP) were generated and characterized. It is shown, that the apparent KM of l-lactate uptake is 20.1μM as determined for strain Rd KW20. Comparison of the COPD isolate NTHi 2019-R with the corresponding lctP knockout strain for survival in human serum revealed no lactate dependent serum resistance. In contrast, we observed a 4-fold attenuation of the mutant strain in a murine model of nasopharyngeal colonization. Characterization of lctP transcriptional control shows that the lactate utilization system in H. influenzae is not an inductor inducible system. Rather negative feedback regulation was observed in the presence of l-lactate and this is dependent on the ArcAB regulatory system. Additionally, for 2019 it was found that lactate may have signaling function leading to increased cell growth in late log phase under conditions where no l-lactate is metabolized. This effect seems to be ArcA independent and was not observed in strain Rd KW20. We conclude that l-lactate is an important carbon-source and may act as host specific signal substrate which fine tunes the globally acting ArcAB regulon and may additionally affect a yet unknown signaling system and thus may contribute to enhanced in vivo survival.
Article Reference Resistance to complement-mediated killing and IgM binding to non-typeable Haemophilus influenzae is not altered when ascending from the nasopharynx to the middle ears in children with otitis media.
We have previously found that non-typeable Haemophilus influenzae (NTHi) collected from the middle ear of children with otitis media (OM) exhibit increased levels of complement resistance compared to NTHi collected from the nasopharynx. However, it is unknown whether bacteria develop complement resistance in the middle ear, or whether resistance is present when residing in the nasopharynx. The objective of this study was to investigate whether the levels of complement resistance of isolates collected from the middle ear were similar to those of isolates from the nasopharynx with an identical MLST type. We included 62 children with recurrent acute OM, chronic OM with effusion or acute tympanostomy tube otorrhea. NTHi was simultaneously isolated from the nasopharynx and middle ear fluid. MLST, resistance to complement-mediated killing, IgG binding, IgM binding and phosphorylcholine expression was determined. In 41 children, NTHi isolated from the middle ear and nasopharynx showed to have an identical MLST type. Isolates collected from the middle ear showed a highly similar level of complement resistance and IgM binding with isolates collected from the nasopharynx, whereas this was not the case for IgG binding and phosphorylcholine incorporation into lipooligosaccharide. Resistance to complement-mediated killing and IgM binding of NTHi isolates with an identical MLST type collected from the middle ear and nasopharynx of children with OM was highly similar.
Article Reference Epidemiology and evolution of antibiotic resistance of Haemophilus influenzae in children 5 years of age or less in France, 2001-2008: a retrospective database analysis.
Trends in the evolution of antimicrobial resistance and mechanisms of resistance of Haemophilus influenzae to β-lactam antibiotics in France were assessed through a retrospective database review. The antimicrobial resistance of 2,206 H. influenzae strains from children aged ≤5 years was studied between 2001 and 2008. Strains were isolated from blood or cerebrospinal fluid (n = 170), bronchial secretions (n = 188), middle ear fluid, and nasopharynx or conjunctiva (n = 1,848). A proportion of 95.1 % (n = 2,097) were non-typeable H. influenzae (NTHi). β-lactamase production was identified in 27.5 % of NTHi isolates (all TEM-1), while β-lactamase-negative ampicillin resistance and β-lactamase-negative amoxicillin-clavulanate resistance among NTHi was 16.9 and 6.4 %, respectively. Over time, a statistically significant decrease in β-lactamase-producing strain prevalence (p < 0.0001) and a statistically significant increase in β-lactamase-negative ampicillin-resistant (BLNAR) strains (p < 0.0001) were observed in NTHi isolates from 2001 to 2008. The largest changes coincided with a campaign to reduce antibiotic use in France. An increasing diversity of amino acid substitution patterns was observed, with the emergence of group III/'III-like' patterns linked to high-level resistance. In France, amino acid substitution patterns are increasingly diverse, and strains with high-level antibiotic resistance are emerging. This study highlights the complexity of resistance dynamics within a given country. These results have implications on antibiotic guidelines and illustrate the importance of continued surveillance.
Article Reference Acute otitis media otopathogens during 2008 to 2010 in Rochester, New York.
The otopathogen distribution colonizing the nasopharynx (NP) and causing acute otitis media (AOM) is in flux following the introduction of pneumococcal conjugate vaccine 7 (PCV7) and will continue to change.
Article Reference Shielding of a lipooligosaccharide IgM epitope allows evasion of neutrophil-mediated killing of an invasive strain of nontypeable Haemophilus influenzae.
Nontypeable Haemophilus influenzae is a frequent cause of noninvasive mucosal inflammatory diseases but may also cause invasive diseases, such as sepsis and meningitis, especially in children and the elderly. Infection by nontypeable Haemophilus influenzae is characterized by recruitment of neutrophilic granulocytes. Despite the presence of a large number of neutrophils, infections with nontypeable Haemophilus influenzae are often not cleared effectively by the antimicrobial activity of these immune cells. Herein, we examined how nontypeable Haemophilus influenzae evades neutrophil-mediated killing. Transposon sequencing (Tn-seq) was used on an isolate resistant to neutrophil-mediated killing to identify genes required for its survival in the presence of human neutrophils and serum, which provided a source of complement and antibodies. Results show that nontypeable Haemophilus influenzae prevents complement-dependent neutrophil-mediated killing by expression of surface galactose-containing oligosaccharide structures. These outer-core structures block recognition of an inner-core lipooligosaccharide epitope containing glucose attached to heptose HepIII-β1,2-Glc by replacement with galactose attached to HepIII or through shielding HepIII-β1,2-Glc by phase-variable attachment of oligosaccharide chain extensions. When the HepIII-β1,2-Glc-containing epitope is expressed and exposed, nontypeable Haemophilus influenzae is opsonized by naturally acquired IgM generally present in human serum and subsequently phagocytosed and killed by human neutrophils. Clinical nontypeable Haemophilus influenzae isolates containing galactose attached to HepIII that are not recognized by this IgM are more often found to cause invasive infections. Importance: Neutrophils are white blood cells that specialize in killing pathogens and are recruited to sites of inflammation. However, despite the presence of large numbers of neutrophils in the middle ear cavity and lungs of patients with otitis media or chronic obstructive pulmonary disease, respectively, the bacterium nontypeable Haemophilus influenzae is often not effectively cleared from these locations by these immune cells. In order to understand how nontypeable Haemophilus influenzae is able to cause inflammatory diseases in the presence of neutrophils, we determined the mechanism that underlies resistance to neutrophil-mediated killing. We have shown that nontypeable Haemophilus influenzae prevents binding of antibodies of the IgM subtype through changes in their surface lipooligosaccharide structure, thereby preventing complement activation and clearance by human neutrophils.
Article Reference Comparison study of single and concurrent administrations of carbapenem, new quinolone, and macrolide against in vitro nontypeable Haemophilus influenzae mature biofilms.
Nontypeable Haemophilus influenzae (NTHi) is an opportunistic pathogen and a common cause of otitis media in children, chronic bronchitis, and pneumonia in patients with chronic obstructive pulmonary disease. Many studies have reported that NTHi is capable of producing biofilms, which may be one of the important factors involved in chronic diseases and accelerating antimicrobial resistance. Unfortunately, there is still no consensus about the elimination of biofilms. In this study, concurrent administrations of levofloxacin (LVFX)-imipenem (IPM) and clarithromycin (CAM)-IPM, as well as the single administration of IPM, LVFX, and CAM, were performed to treat the mature biofilms produced by NTHi, respectively. Biofilm inhibition was quantified using microtiter biofilm assay (MBA), and relative biomass was calculated as the ratio compared to that of untreated control biofilms. The relative biomasses of biofilms treated with IPM, LVFX-IPM, and CAM-IPM against a β-lactamase-negative ampicillin-resistant strain was 1.10, 0.08, and 0.13 at 1× minimum inhibitory concentration (MIC), 0.90, 0.05, and 0.07 at 10× MIC, and 0.80, 0.06, and 0.07 at 100× MIC, respectively. Biofilms were also visually observed by scanning electron microscopy, and a focused ion-beam system showed that high concentrations of combined administration strongly inhibited the biofilms, which was consistent with the results of MBA. Our data demonstrated the antibiofilm effect of concurrent administration against mature NTHi biofilms, which indicated a rationale for the potential use of concurrent administrations in diseases involving chronic NTHi biofilms.
Article Reference Correlation of nasopharyngeal cultures prior to and at onset of acute otitis media with middle ear fluid cultures.
We sought to determine if nasopharyngeal (NP) cultures taken at times of healthy visits or at onset of acute otitis media (AOM) could predict the otopathogen mix and antibiotic-susceptibility of middle ear isolates as determined by middle ear fluid (MEF) cultures obtained by tympanocentesis.
Article Reference Outer membrane protein P5 is required for resistance of nontypeable Haemophilus influenzae to both the classical and alternative complement pathways.
The complement system is an important first line of defense against the human pathogen Haemophilus influenzae. To survive and propagate in vivo, H. influenzae has evolved mechanisms for subverting this host defense, most of which have been shown to involve outer surface structures, including lipooligosaccharide glycans and outer surface proteins. Bacterial defense against complement acts at multiple steps in the pathway by mechanisms that are not fully understood. Here we identify outer membrane protein P5 as an essential factor in serum resistance of both H. influenzae strain Rd and nontypeable H. influenzae (NTHi) clinical isolate NT127. P5 was essential for resistance of Rd and NT127 to complement in pooled human serum. Further investigation determined that P5 expression decreased cell surface binding of IgM, a potent activator of the classical pathway of complement, to both Rd and NT127. Additionally, P5 expression was required for NT127 to bind factor H (fH), an important inhibitor of alternative pathway (AP) activation. Collectively, the results obtained in this work highlight the ability of H. influenzae to utilize a single protein to perform multiple protective functions for evading host immunity.
Article Reference Safety and reactogenicity of primary vaccination with the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine in Vietnamese infants: a randomised, controlled trial.
Pneumococcal infections are major causes of child mortality and morbidity worldwide and antibiotic resistance of Streptococcus pneumoniae is a major concern, especially in Asian countries. The present study was designed to evaluate the reactogenicity and safety of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) when co-administered with the licensed diphtheria, tetanus, acellular pertussis, hepatitis B virus, inactivated poliovirus and H. influenzae type b vaccine (DTPa-HBV-IPV/Hib) in a 3-dose primary vaccination course in Vietnamese infants.
Article Reference Characterization of nontypable Haemophilus influenzae isolates recovered from adult patients with underlying chronic lung disease reveals genotypic and phenotypic traits associated with persistent infection.
Nontypable Haemophilus influenzae (NTHi) has emerged as an important opportunistic pathogen causing infection in adults suffering obstructive lung diseases. Existing evidence associates chronic infection by NTHi to the progression of the chronic respiratory disease, but specific features of NTHi associated with persistence have not been comprehensively addressed. To provide clues about adaptive strategies adopted by NTHi during persistent infection, we compared sequential persistent isolates with newly acquired isolates in sputa from six patients with chronic obstructive lung disease. Pulse field gel electrophoresis (PFGE) identified three patients with consecutive persistent strains and three with new strains. Phenotypic characterisation included infection of respiratory epithelial cells, bacterial self-aggregation, biofilm formation and resistance to antimicrobial peptides (AMP). Persistent isolates differed from new strains in showing low epithelial adhesion and inability to form biofilms when grown under continuous-flow culture conditions in microfermenters. Self-aggregation clustered the strains by patient, not by persistence. Increasing resistance to AMPs was observed for each series of persistent isolates; this was not associated with lipooligosaccharide decoration with phosphorylcholine or with lipid A acylation. Variation was further analyzed for the series of three persistent isolates recovered from patient 1. These isolates displayed comparable growth rate, natural transformation frequency and murine pulmonary infection. Genome sequencing of these three isolates revealed sequential acquisition of single-nucleotide variants in the AMP permease sapC, the heme acquisition systems hgpB, hgpC, hup and hxuC, the 3-deoxy-D-manno-octulosonic acid kinase kdkA, the long-chain fatty acid transporter ompP1, and the phosphoribosylamine glycine ligase purD. Collectively, we frame a range of pathogenic traits and a repertoire of genetic variants in the context of persistent infection by NTHi.
Article Reference Predicted Configurations of Oligosaccharide Extensions in the Lipooligosaccharide of Non-Typeable Haemophilus influenzae.
Lipooligosaccharide configurations were predicted in non-typeable Haemophilus influenzae isolates based on the presence of seven oligosaccharide-extension initiating genes (or alleles). Predicted configurations with 2-3 oligosaccharide extensions were more prevalent among middle ear than throat strains. In addition, strains with these configurations averaged higher levels of serum resistance than strains with other configurations.
Article Reference Non-typeable Haemophilus influenzae, an under-recognised pathogen.
Non-typeable Haemophilus influenzae (NTHi) is a major cause of mucosal infections such as otitis media, sinusitis, conjunctivitis, and exacerbations of chronic obstructive pulmonary disease. In some regions, a strong causal relation links this pathogen with infections of the lower respiratory tract. In the past 20 years, a steady but constant increase has occurred in invasive NTHi worldwide, with perinatal infants, young children, and elderly people most at risk. Individuals with underlying comorbidities are most susceptible and infection is associated with high mortality. β-lactamase production is the predominant mechanism of resistance. However, the emergence and spread of β-lactamase-negative ampicillin-resistant strains in many regions of the world is of substantial concern, potentially necessitating changes to antibiotic treatment guidelines for community-acquired infections of the upper and lower respiratory tract and potentially increasing morbidity associated with invasive NTHi infections. Standardised surveillance protocols and typing methodologies to monitor this emerging pathogen should be implemented. International scientific organisations need to raise the profile of NTHi and to document the pathobiology of this microbe.
Article Reference Beta- lactam antibiotics stimulate biofilm formation in non-typeable haemophilus influenzae by up-regulating carbohydrate metabolism.
Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended.
Article Reference The Haemophilus Sap Transporter Mediates Bacterial-Epithelial Cell Homeostasis.
Nontypeable Haemophilus influenzae (NTHI) is a commensal inhabitant of the human nasopharynx, and causative agent of otitis media and other diseases of the upper and lower human airway. During colonization within the host, NTHI must acquire essential nutrients and evade immune attack. We previously demonstrated that the NTHI Sap transporter, an inner membrane protein complex, mediates resistance to antimicrobial peptides and is required for heme homeostasis. We hypothesized that Sap transporter functions are critical for NTHI interaction with the host epithelium and establishment of colonization. Thus, we co-cultured the parent or the sapA mutant on polarized epithelial cells grown at an air-liquid interface, as a physiological model of NTHI colonization, to determine the contribution of the Sap transporter on bacterial-host cell interactions. Although SapA-deficient NTHI were less adherent to epithelial cells, we observed a significant increase in invasive bacteria compared to the parent strain. Upon internalization, the sapA mutant appeared free in the cytoplasm whereas the parent strain was primarily found in endosomes, indicating differential subcellular trafficking. Additionally, we observed reduced inflammatory cytokine production by the epithelium to the sapA mutant strain compared to the parental strain. Furthermore, chinchilla middle ears challenged with the sapA mutant demonstrated a decrease in disease severity compared to ears challenged with the parental strain. Collectively, our data suggest that NTHI sense host environmental cues via Sap transporter function to mediate interaction with host epithelial cells. Epithelial cell invasion and modulation of host inflammatory cytokine responses may promote NTHI colonization and access to essential nutrients.
Article Reference Relative contribution of lipooligosaccharide inner and outer core modifications to nontypable Haemophilus influenzae pathogenesis.
Nontypable Haemophilus influenzae (NTHi) is a frequent commensal of the human nasopharynx that causes opportunistic infection in immunocompromised individuals. Existing evidence associates lipooligosaccharide (LOS) with disease, but the specific and relative contribution of NTHi LOS modifications to virulence properties of the bacterium has not been comprehensively addressed. Using NTHi strain 375, an isolate where the detailed LOS structure has been determined, we compared systematically a set of isogenic mutant strains expressing sequentially truncated LOS. The relative contribution of 2-keto-3-deoxyoctulosonic acid, the tri-heptose inner core, oligosaccharide extensions on heptoses I and III, phosphorylcholine, di-galactose and sialic acid to NTHi resistance to antimicrobial peptides (AMP), self-aggregation, biofilm formation, cultured human respiratory epithelial infection, and murine pulmonary infection was assessed. We show that opsX, lgtF, lpsA, lic1 and lic2A contribute to bacterial resistance to AMP; lic1 is related to NTHi self-aggregation; lgtF, lic1 and siaB are involved in biofilm growth; opsX and lgtF participate in epithelial infection; opsX, lgtF and lpsA contribute to lung infection. Depending on the phenotype, the involvement of these LOS modifications occurs at a different extent, independently or having an additive effect in combination. Collectively, we propose the relative contribution of LOS epitopes to NTHi virulence and frame a range of pathogenic traits in the context of infection.