Epidemiology of Haemophilus influenzae in the Republic of Ireland, 2010–2018

Extensively drug-resistant Haemophilus influenzae isolated in Geneva, Switzerland

The emergence of multi-drug resistant (MDR) and even extensively drug-resistant (XDR) strains among H. influenzae was observed in some Asian countries. Herein, we reported the first XDR H. influenzae isolated in Geneva, Switzerland. This strain was isolated in a good-quality sputum sample from a 63 year-old male patient. There was no respiratory infection diagnosed at that time. The strain was non-typeable and pan-β-lactam resistant. According to whole genome sequencing analysis it belongs to sequence type 159 and the ST-107 clonal complex. It was classified into group III + regarding the amino acid substitutions identified in the transpeptidase domain of PBP3.

Clinical and microbiological characteristics of invasive diseases due to Haemophilus influenzae in the Minami Ibaraki Area, Japan

INTRODUCTION

We investigated clinical and microbiological characteristics of invasive Haemophilus influenzae disease (IHD) during recent 20 years in the Minami Ibaraki Area.

METHODS

H. influenzae strains isolated from the blood and the cerebrospinal fluid in 5 hospitals located in this area between 2001 and 2020 (the pre-vaccination period [PreVP]: 2001-2010, the post-vaccination period [PostVP]: 2011-2020) were consecutively collected. Drug susceptibilities, capsular types, β-lactamase production, and sequence types of the strains and clinical information of patients from whom the strains were isolated were investigated.

RESULTS

A total of 99 H. influenzae strains (59 in PreVP and 40 in PostVP) were collected. The ages of the patients were significantly higher in PostVP (median: 1 vs 69.5 years). The most common organ infected primarily was the central nervous system in PreVP (38 cases) and the lung in PostVP (22 cases). Mortality was significantly higher in PostVP (1.7 % vs 15.0 %). Strains serotyped b (Hib) and non-typeable (NTHi) were predominant in PreVP and PostVP (88.1 % and 80.0 %, respectively). Only 2 encapsulated non-Hib strains (1 each of types e and f) were found. The ratio of strains with beta-lactamase non-producing ampicillin resistance (BLNAR) was significantly higher in PostVP (10.2 % vs 42.5 %). All Hib strains belonged to the ST6-complex; while most of NTHi strains were genetically diverse.

CONCLUSION

The picture of IHD in this area has changed from meningoencephalitis among children due to Hib to pneumonia among adults due to NTHi, with the increases in BLNAR strains and mortality.

Trends in serotype distribution and antimicrobial susceptibility pattern of invasive Haemophilus influenzae isolates from Brazil, 2009-2021

INTRODUCTION

Invasive Haemophilus influenzae (Hi) disease poses a significant global health challenge. With the relaxation of COVID-19 pandemic measures and declining H. influenzae serotype b (Hib) vaccination coverage, there is concern about a potential increase in Hi cases worldwide.

METHODOLOGY

This study analyzed 1437 invasive Hi isolates in Brazil over 13 years, determining capsular serotypes, antimicrobial susceptibility, and genetic relatedness through multilocus sequence typing.

RESULTS

The primary source of isolation for these invasive H. influenzae isolates was blood (54.4%), followed by cerebrospinal fluid (37.1%) and lung specimens (8.5%), respectively. Consequently, bacteremia (47%) was the most common clinical presentation, followed by meningitis (39.6%) and pneumonia (13.4%). Non-encapsulated Hi (NTHi) predominated among the isolates (51.4%), along with serotype a (22%) and serotype b (21.5%) among the encapsulated isolates. The majority of the encapsulated isolates were isolated from children under 14 years of age (76.7%), while NTHi isolates were identified in patients older than 15 years, particularly those ≥ 60 years old (40%). Ampicillin resistance was observed in 17.1% of cases, displaying β-lactamase production as the principal resistance mechanism. MLST revealed a diverse NTHi population, whereas the encapsulated isolates presented a clonal structure.

CONCLUSION

This study describes the prevalence of NTHi isolates circulating in Brazil after two decades of the Hib vaccine immunization program. Continuous universal surveillance is crucial for implementing prompt public health measures to prevent and control invasive Hi disease and monitor changes in antibiotic resistance profiles.

Antibiotic resistance and molecular characterization of non-invasive clinical Haemophilus influenzae isolates in Germany 2019 and 2020

Background

Haemophilus influenzae (Hi) is known as a cause of invasive and non-invasive diseases. Especially ear, nose and throat (ENT) infections are common reasons for antibiotic prescriptions in outpatient settings in Germany. Therefore, antibiotic resistance surveillance is important to provide the basis of recommendations for the empirical usage of antibiotic agents.

Objectives

To provide data on susceptibility rates of oral antibiotics for non-invasive clinical Hi isolates in Germany and to investigate molecular resistance patterns of β-lactams, ciprofloxacin, doxycycline and trimethoprim/sulfamethoxazole.

Methods

Isolates were collected from a sentinel network of diagnostic laboratories in a prospective multicentre prevalence study. Antibiotic susceptibility testing was done with a commercial broth microdilution kit. MICs were interpreted according to EUCAST guidelines. Resistance gene sequencing and WGS were performed to analyze molecular antibiotic resistance patterns and genetic relationships between the isolates.

Results

In total, 215 Hi isolates were collected from 23 laboratories across Germany. The highest resistance rates were found for amoxicillin (n = 30; 14%), cefuroxime (n = 40; 18.6%) and trimethoprim/sulfamethoxazole (co-trimoxazole) (n = 34; 15.8%). Resistance to amoxicillin was mainly due to blaTEM-1 (n = 29; 96.7%). PBP3 alterations were found in 39 of 40 cefuroxime-resistant isolates (97.5%). Two of the cefuroxime-resistant isolates harboured PBP3 mutation patterns that have not yet been associated with cefuroxime resistance; in one of them, a known lpoA mutation was found. One isolate showed no mutations in PBP3 or lpoA. All co-trimoxazole-resistant isolates (15.8%) showed known mutations in folA and its promoter region. Additionally, point mutations in folP were identified in a subset of these isolates. The most frequent sequence types (STs) were ST57 (n = 10) and ST103 (n = 10). Genetic cluster analysis identified six clusters, but no epidemiological link could be confirmed.

Conclusion

Resistance to oral antibiotics in non-invasive clinical Hi isolates in Germany was generally low. Amoxicillin is estimated to cover 86% of infections involving non-invasive Hi and, therefore, is still effective for the first-line empirical treatment for ENT infections in Germany. Further surveillance of antimicrobial susceptibility in non-invasive Hi isolates is important to ensure the data basis for guidelines of antibiotic usage.

Monitoring of Haemophilus influenzae isolated from carriage, lower respiratory tract infections and blood over a six-month period in Belgium

INTRODUCTION

H. influenzae carriage may evolve into respiratory or systemic infections. However, no surveillancesystem is in place in Belgium to monitor carriage strains.

MATERIAL AND METHODS

This study provides a detailed description of H. influenzae strains isolated from both carriage and lower respiratory infections, collected during a six-month national surveillance. Subsequently, a comparison is conducted with invasive isolates collected during the same period at the National Reference Centre (NRC).

RESULTS AND DISCUSSION

From November 2021 to April 2022, 39 clinical laboratories collected 142 and 210 strains of H. influenzae from carriage and infection, respectively, and 56 strains of blood were submitted to the NRC. In each group, the biotype II comprised more than 40%, followed by biotypes III and I. The majority of strains were non-typeable H. influenzae, with a notable increase in the number of encapsulated strains in the invasive group (14.3% vs. 1-2%). A beta-lactamase was identified in 18.5% and 12.5% of surveillance and invasive strains, respectively. Resistance to the amoxicillin-clavulanic acid combination accounted for 7% in the surveillance strains and 10.7% in invasive strains. The overall resistance to third-generation cephalosporins at 1.2% is consistent with rates observed in other European countries. Of particular significance is the identification of mutations in the ftsI gene in both carriage and infected strains, which are associated with high-level beta-lactam resistance.

CONCLUSION

NRC must engage in regular and systematic monitoring of beta-lactam susceptibility of H. influenzae to guarantee safe empiric therapy in severe cases and identify potential transitions from low-level to high-level resistance in the future.

Microevolution and Its Impact on Hypervirulence, Antimicrobial Resistance, and Vaccine Escape in Neisseria meningitidis

Neisseria meningitidis is commensal of the human pharynx and occasionally invades the host, causing the life-threatening illness invasive meningococcal disease. The meningococcus is a highly diverse and adaptable organism thanks to natural competence, a propensity for recombination, and a highly repetitive genome. These mechanisms together result in a high level of antigenic variation to invade diverse human hosts and evade their innate and adaptive immune responses. This review explores the ways in which this diversity contributes to the evolutionary history and population structure of the meningococcus, with a particular focus on microevolution. It examines studies on meningococcal microevolution in the context of within-host evolution and persistent carriage; microevolution in the context of meningococcal outbreaks and epidemics; and the potential of microevolution to contribute to antimicrobial resistance and vaccine escape. A persistent theme is the idea that the process of microevolution contributes to the development of new hyperinvasive meningococcal variants. As such, microevolution in this species has significant potential to drive future public health threats in the form of hypervirulent, antibiotic-resistant, vaccine-escape variants. The implications of this on current vaccination strategies are explored.

National Danish surveillance of invasive clinical Haemophilus influenzae isolates and their resistance profile

INTRODUCTION

This study aimed to investigate the epidemiology, serotype distribution, phenotypical antibiogram, and molecular resistance gene characteristics of invasive Haemophilus influenzae infections in Denmark from 2014 to 2022. Additionally, the potential impact of outdoor temperature and COVID-19 restrictions on the epidemiology of H. influenzae was assessed.

MATERIALS AND METHODS

Invasive H. influenzae isolates were received from patients with positive culture results from cerebrospinal fluid, blood, or other sterile sites. Sample data were obtained from the Danish laboratory surveillance system/MiBa database, and whole-genome sequencing (WGS) was performed on the isolates. The incidence rates and distribution of H. influenzae cases were analyzed, and antibiotic susceptibility were assessed.

RESULTS

A total of 1,007 invasive H. influenzae cases were identified, with serotyping conducted for 752 (74.7%) isolates. The median incidence per year of H. influenzae was 2.0 cases per 100,000, with the highest incidence in 2014 and the lowest in 2020. The majority of H. influenzae isolates were non-typeable H. influenzae (NTHi), while the most prominent serotypes were serotype f followed by serotype b. Bacteremia cases accounted for the majority (88.6%) of occurrences, although meningitis cases showed an increasing trend during the time period. The age group 85+ exhibited the highest incidence. The implementation of COVID-19 preventive interventions in 2020 resulted in a significant reduction in H. influenzae incidence, which returned to pre-COVID levels in 2021. A negative correlation was observed between monthly H. influenzae cases and outdoor temperature. An overall level of genetic beta-lactamase resistance of 26.3% was observed divided into 10.6% beta-lactamase-positive ampicillin-resistant (gBLPAR), 13.6% beta-lactamase-negative ampicillin-resistant (gBLNAR) and 2.1% beta-lactamase-positive amoxicillin clavulanate-resistant (gBLPACR). Other non-beta-lactam resistance traits were detected in 7.6% of isolates (primarily aminoglycoside-modifying enzymes).

CONCLUSION

The overall incidence of H. influenzae in Denmark returned to stable levels after the COVID-19 epidemic, with NTHi strains dominating. The COVID-19 preventive interventions led to a major reduction in incidence. A significant negative correlation between the incidence of H. influenzae and temperature was observed. The study revealed an overall genetic beta-lactam resistance rate of 26.3%, and the concordance between genotypic and phenotypic beta-lactam resistance was high (98.2%).

Trends in invasive Haemophilus influenzae serotype a disease in England from 2008-09 to 2021-22: a prospective national surveillance study

BACKGROUND

Invasive Haemophilus influenzae serotype a (Hia) disease is rare, with most cases reported among Indigenous populations in North America. In England, national surveillance was enhanced following an increase in laboratory-confirmed invasive Hia disease since the 2016-17 epidemiological year. This study aimed to describe the epidemiological trends, clinical characteristics of cases, and assess potential genomic drivers.

METHODS

Hospital laboratories in England routinely submit invasive H influenzae isolates to the UK Health Security Agency for confirmation and serotyping. In this prospective national surveillance study we contacted the general practitioners and clinicians of all patients with laboratory-confirmed invasive Hia from the 2008-09 to the 2021-22 epidemiological year to complete a clinical questionnaire on demographics, underlying conditions, clinical presentation, complications, outcomes, and travel history of the patient. All Hia invasive isolates from residents in England were included in the study; non-invasive isolates were excluded. Multilocus sequence typing (MLST), whole genome single-nucleotide polymorphism, and k-mer-based analysis of bacterial isolates were performed following Illumina whole-genome sequencing (WGS). Outcomes included epidemiological trends, clinical characteristics of confirmed Hia cases, and genomic analyses.

FINDINGS

From the 2008-09 to the 2021-22 epidemiological years, there were 52 cases of invasive infection with H influenzae serotype a in England (25 [48%] in female patients and 27 [52%] in male patients). There were zero to two annual Hia cases (accounting for <0·5% of serotyped H influenzae isolates) until 2015-16, after which cases increased across England to 19 cases in 2021-22 (incidence 0·03 cases per 100 000), when Hia accounted for 19 (4%) of 484 serotyped H influenzae isolates, 19 (19%) of 100 capsulated cases, and 37% (19 of 52) of all H influenzae cases between 2008-09 and 2021-22. Most of the recent increase in cases occurred among individuals aged 65 years and older (17 [33%] of 52), who typically presented with bacteraemic pneumonia (13 [76%] of 17), and infants younger than 1 year, who had the highest incidence and were more likely to present with meningitis (five [50%] of ten). Overall case fatality rate was 7·7% (95% CI 2·1-19·7; four of 52 patients). WGS found that closely related MLST sequence types ST1511 (20 [39%] of 51), ST23 (13 [25%] of 51), and ST56 (seven [14%] of 51) accounted for most cases, with no evidence of serotype b strains switching capsule to Hia. Duplication of the capsule operon, associated with more severe disease, was present in 32 (80%) of 40 of these sequence types. Analysis of the core and accessory genome content grouped most isolates into a single strain.

INTERPRETATION

The persistent increase in invasive Hia cases across England and across all age groups suggests widespread transmission, consistent with reports from other European countries, and will require close monitoring.

FUNDING

UK Health Security Agency.

Haemophilus influenzae carriage and antibiotic resistance profile in Belgian infants over a three-year period (2016-2018)

Background

Non-typeable Haemophilus influenzae has become increasingly important as a causative agent of invasive diseases following vaccination against H. influenzae type b. The emergence of antibiotic resistance underscores the necessity to investigate typeable non-b carriage and non-typeable H. influenzae (NTHi) in children.

Methods

Nasopharyngeal swab samples were taken over a three-year period (2016-2018) from 336 children (6-30 months of age) attending daycare centers (DCCs) in Belgium, and from 218 children with acute otitis media (AOM). Biotype, serotype, and antibiotic resistance of H. influenzae strains were determined phenotypically. Mutations in the ftsI gene were explored in 129 strains that were resistant or had reduced susceptibility to beta-lactam antibiotics. Results were compared with data obtained during overlapping time periods from 94 children experiencing invasive disease.

Results

Overall, NTHi was most frequently present in both carriage (DCC, AOM) and invasive group. This was followed by serotype "f" (2.2%) and "e" (1.4%) in carriage, and "b" (16.0%), "f" (11.7%), and "a" (4.3%) in invasive strains. Biotype II was most prevalent in all studied groups, followed by biotype III in carriage and I in invasive strains. Strains from both groups showed highest resistance to ampicillin (26.7% in carriage vs. 18.1% in invasive group). A higher frequency of ftsI mutations were found in the AOM group than the DCC group (21.6 vs. 14.9% - p = 0.056). Even more so, the proportion of biotype III strains that carried a ftsI mutation was higher in AOM compared to DCC (50.0 vs. 26.3% - p < 0.01) and invasive group.

Conclusion

In both groups, NTHi was most frequently circulating, while specific encapsulated serotypes for carriage and invasive group were found. Biotypes I, II and III were more frequently present in the carriage and invasive group. The carriage group had a higher resistance-frequency to the analyzed antibiotics than the invasive group. Interestingly, a higher degree of ftsI mutations was found in children with AOM compared to DCC and invasive group. This data helps understanding the H. influenzae carriage in Belgian children, as such information is scarce.

Available evidence and potential for vaccines for reduction in antibiotic prescriptions

Bacterial antibiotic resistance is a public health issue. It means that drugs become ineffective, infections persist and have a huge impact on the health of patients and their spreading increases. To address a complex threat such as bacterial antibiotic resistance different and integrated approaches are needed including discovery of new antibiotics, improvement of diagnostics tools and improvement of antibiotic stewardship. Absolutely relevant are prevention of infections as well as decrease in the use of antibiotics. Vaccines are an important tool in the fight against bacterial antibiotic resistance and can help prevent it in several ways. Indeed, vaccines are highly effective in preventing diseases that might otherwise require the use of antibiotics to treat symptoms and associated complications. Preventing infections through vaccination helps reduce the need for and widespread and inappropriate use of antibiotics, including for secondary bacterial infections.

Molecular epidemiology and antimicrobial resistance of Haemophilus influenzae in Guiyang, Guizhou, China

Background

The widespread use of antimicrobials and Haemophilus influenzae type b (Hib) vaccine worldwide has altered the epidemiological patterns of invasive H. influenzae. Nonetheless, little is currently known on the epidemiological characteristics of H. influenzae in Guiyang, Guizhou, China.

Objective

To determine the serotype distribution, antimicrobial resistance and Multilocus Sequence Typing (MLST) of H. influenzae in hospitalized patients in Guiyang City.

Methods

A total of 196 clinical isolates from hospitalized patients were collected. Serotypes were determined according to the specific capsule gene, bexA, amplified by PCR. According to the guidelines of Clinical and Laboratory Standards Institute (CLSI) 2020 drug susceptibility tested, and the results determined. The chromogenic cephalosporin nitrocefin method was used to detect β-lactamase production, β-lactamase negative, ampicillin-resistant (BLNAR) strains were detected by PCR amplification and sequencing of the penicillin-binding protein 3 (PBP3) locus of ftsI. Multilocus Sequence Typing was performed for molecular typing.

Results

All isolates studied were non-typeable H. influenzae (NTHi). Most patients originated from the pediatrics department (78.6%, 154/196), and suffered from lung with respiratory tract infection (pneumonia and bronchitis, 68.4%, 134/196). The resistance rates of ampicillin, cefaclor and azithromycin were 71.4% (140/196), 36.7% (72/196) and 34.2% (67/196), respectively. 40.3% (79/196) of strains were β-lactamase positive ampicillin-resistant (BLPAR). All BLPAR carried the TEM-1 gene. 9.2% (18/196) were β-lactamase negative ampicillin-resistant strains (BLNAR). The PBP3 mutation was detected in the ampicillin-resistant strains (n = 113), of which 18 belonged to group IIa. A total of 49 sequence types (ST) and 23 clonal complexes (CC) were detected, among which CC107 (ST107, n = 27; ST1002, n = 5; ST1218, n = 5) was the most frequent clonal complexes. BLPAR isolates mostly belonged to ST107 (20/79), while BLNAR was predominantly distributed in ST12 (5/18).

Conclusion

H. influenzae infections are predominately caused by genetically diverse NTHi among hospitalized patients in Guiyang. The prevalence of β-lactamase production and PBP3 mutation may contribute to the high local ampicillin resistance rate.

Haemophilus influenzae type f in the post-Haemophilus influenzae type b vaccination era: a systematic review

Since the introduction of Haemophilus influenzae (Hi) serotype b (Hib) vaccination, reports of increasing incidence rates of non-Hib serotypes have emerged. A systematic review was performed to investigate whether the Hi serotype f (Hif) incidence rate has increased globally and to describe its associated disease burden. In the post-Hib vaccine era, evidence shows that the incidence rate of Hif infection is increasing worldwide. In total 94 studies including 2 701 patients reported Hif infections. The estimated pooled incidence rate of Hif infection was 0.15/100 000 population per year (range: 0.05–0.40/100 000), with a median case fatality ratio of 14.3 %. Invasive infections most frequently presented as pneumonia (45 %), septicaemia (34 %) and meningitis (20 %). Of 191 Hif isolates, 87 % were ampicillin-susceptible. Multi-locus sequence typing revealed that Hif were relatively clonal, with the majority belonging to clonal complex 124. Hif causes invasive infections of significant variance in both severity and presentation. Globally, the Hif population shows little genetic variability and currently appears to possess low resistance to antimicrobials.

Impact of a Single-Tube PCR Assay for the Detection of Haemophilus influenzae Serotypes a, c, d, e and f on the Epidemiological Surveillance in Greece

Background: The decrease in the rate of meningitis due to Haemophilus influenzae type b after vaccine introduction and a possible change in epidemiology of H. influenzae disease highlights the need for continuous serotype surveillance. Methods: A single-tube multiplex PCR assay for serotyping of H. influenzae was developed and deployed. Results: During 2003−2020, 108 meningitis cases due to H. influenzae were notified; 86 (80%) were confirmed and serotyped by molecular methods. The overall specificity and sensitivity of the assay were estimated (100% PPV and NPV respectively). The overall mean annual reported incidence for H. influenzae was 0.02, while for Hib and non-b meningitis equaled 0.02 and 0.03 per 100 000, respectively. Analysis by age group revealed that H. influenzae peaks in toddlers and children 0−4 years and in adults >45 years old. Among the serotyped cases, 39.8% were identified as Hib, 46.3% as NTHi, and 0.9% and 2.8% as serotypes a (Hia) and f (Hif)) respectively. Conclusions: Low incidence due to Hib was observed while non-typeable H. influenzae (NTHi) and serotypes Hia and Hif seem to emerge. The application of the current assay discloses the ongoing change of invasive H. influenzae disease trends during the Hib post-vaccine era.

Nontypeable Haemophilus influenzae P5 Binds Human C4b-Binding Protein, Promoting Serum Resistance

Exposure of P5 at the surface of NTHi positively correlates with C4BP binding.

C4BP bound to the bacterial surface retains its complement inhibitory capacity.

C4BP binding to P5 is important for NTHi serum resistance.

Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative human pathogen that causes infections mainly in the upper and lower respiratory tract. The bacterium is associated with bronchitis and exacerbations in patients suffering from chronic obstructive pulmonary disease and frequently causes acute otitis media in preschool children. We have previously demonstrated that the binding of C4b binding protein (C4BP) is important for NTHi complement evasion. In this study, we identified outer membrane protein 5 (P5) of NTHi as a novel ligand of C4BP. Importantly, we observed significantly lower C4BP binding and decreased serum resistance in P5-deficient NTHi mutants. Surface expression of recombinant P5 on Escherichia coli conferred C4BP binding and consequently increased serum resistance. Moreover, P5 expression was positively correlated with C4BP binding in a series of clinical isolates. We revealed higher levels of P5 surface expression and consequently more C4BP binding in isolates from the lower respiratory tract of chronic obstructive pulmonary disease patients and tonsil specimens compared with isolates from the upper respiratory tract and the bloodstream (invasive strains). Our results highlight P5 as an important protein for protecting NTHi against complement-mediated killing.

Cefotaxime resistance in invasive Haemophilus influenzae isolates in Germany 2016-19: prevalence, epidemiology and relevance of PBP3 substitutions

BACKGROUND

Haemophilus influenzae can cause invasive infections, in which cefotaxime is among the first-line antibiotics for treatment. The prevalence of cefotaxime-resistant H. influenzae in Europe is reported to be on a low level. Nevertheless, systematic studies with a large set of invasive isolates are scarce.

OBJECTIVES

To provide prevalence data for cefotaxime resistance in invasive H. influenzae isolates in Germany 2016-19 and investigate the epidemiological relevance of PBP3 mutations known to elevate the cefotaxime MIC.

METHODS

Cefotaxime susceptibility of invasive H. influenzae isolates, collected in the national laboratory surveillance programme, was examined by gradient agar diffusion (GAD) testing. Cefotaxime resistance was determined according to EUCAST guidelines (resistance breakpoint MIC >0.125 mg/L). Therefore, the MIC for all resistant isolates was verified by broth microdilution method (BMD). WGS was performed to investigate the genetic relationship of cefotaxime-resistant isolates and to analyse alterations in the PBP3. An analysis of the geographic distribution of the resistant isolates was performed.

RESULTS

From 2016 to 2019, the German National Reference Laboratory for Meningococci and H. influenzae received 2432 invasive H. influenzae isolates from blood and CSF. According to GAD results, 27 strains were resistant to cefotaxime. BMD confirmed the resistance in 22 of these isolates, which equals a prevalence of cefotaxime resistance of 0.90% in invasive H. influenzae in Germany. Among cefotaxime-resistant isolates cgMLST revealed three clusters. PBP3 analysis showed previously described mutations in our strains. In comparison with cefotaxime-susceptible strains, the alterations L389F and Y557H were significantly associated with cefotaxime resistance, but were not present in all resistant strains. Geographic analysis showed that the disease cases with cefotaxime-resistant H. influenzae were evenly spread throughout the population in Germany.

CONCLUSIONS

Cefotaxime is still well suited for the treatment of invasive H. influenzae infections. Rarely occurring cefotaxime resistance is caused by sporadic mutations. The role of PBP3 mutations needs further investigation.

Dissemination of quinolone low-susceptible Haemophilus influenzae ST422 in Tokyo, Japan

INTRODUCTION

Haemophilus influenzae with a reduced susceptibility to quinolones (quinolone low-susceptible H. influenzae) has recently emerged in Japan. In addition, the regional outbreak of the quinolone low-susceptible H. influenzae ST422 clone has been reported. In this study, we isolated this clone from an acute care hospital located in a geographically different area from the previous outbreak and characterised the nature of this clone.

METHODS

Eighty-nine H. influenzae isolated between 2017 and 2019 were tested. The antimicrobial susceptibility was determined by the broth dilution method. The genetic background was analysed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. Growth ability and β-lactamase acquisition were evaluated by growth curve analysis and conjugative transfer experiments, respectively.

RESULTS

Quinolone low-susceptible isolates accounted for 4.2% (1/24) in 2018 and 13.9% (5/36) in 2019. Most of the quinolone low-susceptible strains (83.3%) were classified as ST422 and had amino acid substitutions in quinolone resistance-determining regions in both GyrA and ParC. The patients' backgrounds were highly diverse. In addition, these isolates showed the same PFGE pattern as outbreak strains. The growth of ST422 clone was relatively faster than other clones. Furthermore, ST422 clone was able to acquire β-lactamase from a β-lactamase positive strain by horizontal transfer, becoming highly resistant to β-lactams.

CONCLUSION

Our study indicated that the quinolone low-susceptible H. influenzae ST422 clone has been spreading in the community undetected. In addition, this clone has the potential to grow faster and become more resistant through exogenous gene transfer. Therefore, ST422 clone should be monitored attention throughout Japan.

Identification of mcr-1 and a novel chloramphenicol resistance gene catT on an integrative and conjugative element in an Actinobacillus strain of swine origin

The aim of this study was to characterize a mcr-1-carrying integrative and conjugative element (ICE) in a novel Pasteurellaceae-like bacteria of swine origin. The mcr-1-positive GY-402 strain, recovered from a pig fecal sample, was subjected to whole genome sequencing with the combination of Illumina Hiseq and MinION platforms. Genome-based taxonomy revealed that strain GY-402 exhibited highest ANI value (84.89 %) to Actinobacillus succinogenes, which suggested that it represented a novel Actinobacillus species. Sequence analysis revealed that mcr-1 was clustered with eight other resistance genes in the MDR region of a novel ICE element, named ICEAsp1. Inverse PCR and mating assays showed that ICEAsp1 is active and transferrable. In addition, six circular forms mediated by four ISApl1 elements were detected with different inverse PCR sets, indicating that flexible composite transposons could be formed by pairwise combinations of multiple IS copies. Cloning experiment and phylogenetic analysis revealed that the novel Cat protein, designated CatT, belongs to type-A family and confers resistance to chloramphenicol. In conclusion, this is, to the best of our knowledge, the first report of mcr-1 gene on ICE structure and also in Pasteurellaceae bacteria. The diverse composite transposons mediated by multicopy IS elements may facilitate the dissemination of different resistance genes.