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

Epidemiology of invasive Haemophilus influenzae infections in Belgium: 2018-2022

INTRODUCTION

Haemophilus influenzae plays a major role in invasive bacterial infections. Resistant strains are emerging, prompting the WHO to include H. influenzae on its list of priority pathogens for research and development of new antibiotics.

PURPOSE

We aimed to describe the serotypes, demographics and susceptibility profiles of invasive strains collected in Belgium.

METHODS

Data on invasive strains referred to the Belgian National Reference Center for H. influenzae from 2018 to 2022 were analyzed retrospectively.

RESULTS

A total of 608 invasive strains were included. The number of notifications per year ranged from 85 to 165, with a marked decrease between 2020 and 2021. The highest incidence rate was observed in Brussels (1.56 per 100,000 inhabitants over the five year 2018-2022). Sex and age distribution were in line with global trends, as was the predominance of the non-typeable H. influenzae (NTHI). Beta-lactam resistance varies between molecules: 18.9% for ampicillin, 5.6% for amoxicillin-clavulanate. Mutations in the ftsI gene associated with decreased susceptibility to beta-lactams increased from 11.5 to 17.7% over the period studied.

DISCUSSION

The COVID-19 pandemic significantly influenced the epidemiology of invasive H. influenzae infections in Belgium. Demographic analysis identified a significant male predominance among infants, with a male-to-female ratio of 2.57 in patients under one year of age, a high figure not previously reported in the literature. The continued predominance of NTHI underscores the efficacy of Hib vaccination, although the emergence of Hib in patients younger than five years in 2022 suggests an alarming serotype dynamic. The detection of meropenem resistance also highlights the growing threat of antimicrobial resistance, while the increase in ftsI gene mutations raises concerns about the efficacy of first-line treatment.

CONCLUSIONS

This study provides a comprehensive overview of the epidemiology of invasive H. influenzae infections in Belgium, focusing on demographic changes, serotype predominance and antimicrobial resistance trends. Vigilant surveillance and research are essential to address emerging challenges and guide future interventions, including potential vaccine development.

Haemophilus influenzae Invasive Infections in Children in Vaccine Era: Phenotypic and Genotypic Characterization Tunis, Tunisia

The changing epidemiological profile of invasive Haemophilus influenzae infections (IIHi) is noted in the post-vaccination era. The aim of this study was to characterize phenotypically and genotypically invasive Haemophilus influenzae (Hi) isolates detected in Tunisian pediatric patients. A retrospective study was conducted in the microbiology laboratory of the Children's Hospital of Tunis over ten years (2013-2023). All IIHi cases were included. Molecular identification and serotyping were conducted through qPCR. Molecular typing and analysis of resistance genes were extracted from whole genome sequencing data. Fifty-three IIHi cases were collected. Children under five years old were the most affected (81%). Non-typable isolates (NTHi) were predominant (79%) followed by serotype b (17%) and serotype a (4%). Genetic diversity was observed, essentially among NTHi isolates. Resistance of Hi isolates to ampicillin, amoxicillin-clavulanic acid and cefotaxime (CTX) were 42%, 20% and 4%, respectively. Thirteen isolates (29%) produced a beta-lactamase and 14 carried the blaTEM-1 gene (kappa = 0.95). For non-enzymatic resistance, group 3 (n = 12) showed resistance to ampicillin. Groupe 4 (n = 9, NTHi) showed discordances with resistance to CTX. The emergence of resistance to CTX is concerning. Continuous surveillance through molecular tools in conjunction with phenotypic and clinical data is necessary to ensure better management of these infections.

Revisiting mutational resistance to ampicillin and cefotaxime in Haemophilus influenzae

BACKGROUND

Haemophilus influenzae is an opportunistic bacterial pathogen that can cause severe respiratory tract and invasive infections. The emergence of β-lactamase-negative ampicillin-resistant (BLNAR) strains and unclear correlations between genotypic (i.e., gBLNAR) and phenotypic resistance are challenging empirical treatments and patient management. Thus, we sought to revisit molecular resistance mechanisms and to identify new resistance determinants of H. influenzae.

METHODS

We performed a systematic meta-analysis of H. influenzae isolates (n = 291) to quantify the association of phenotypic ampicillin and cefotaxime resistance with previously defined resistance groups, i.e., specific substitution patterns of the penicillin binding protein PBP3, encoded by ftsI. Using phylogenomics and a genome-wide association study (GWAS), we investigated evolutionary trajectories and novel resistance determinants in a public global cohort (n = 555) and a new clinical cohort from three European centers (n = 298), respectively.

RESULTS

Our meta-analysis confirmed that PBP3 group II- and group III-related isolates were significantly associated with phenotypic resistance to ampicillin (p < 0.001), while only group III-related isolates were associated with resistance to cefotaxime (p = 0.02). The vast majority of H. influenzae isolates not classified into a PBP3 resistance group were ampicillin and cefotaxime susceptible. However, particularly group II isolates had low specificities (< 16%) to rule in ampicillin resistance due to clinical breakpoints classifying many of them as phenotypically susceptible. We found indications for positive selection of multiple PBP3 substitutions, which evolved independently and often step-wise in different phylogenetic clades. Beyond ftsI, other possible candidate genes (e.g., oppA, ridA, and ompP2) were moderately associated with ampicillin resistance in the GWAS. The PBP3 substitutions M377I, A502V, N526K, V547I, and N569S were most strongly related to ampicillin resistance and occurred in combination in the most prevalent resistant haplotype H1 in our clinical cohort.

CONCLUSIONS

Gradient agar diffusion strips and broth microdilution assays do not consistently classify isolates from PBP3 groups as phenotypically resistant. Consequently, when the minimum inhibitory concentration is close to the clinical breakpoints, and genotypic data is available, PBP3 resistance groups should be prioritized over susceptible phenotypic results for ampicillin. The implications on treatment outcome and bacterial fitness of other extended PBP3 substitution patterns and novel candidate genes need to be determined.

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.

Prevalence of piperacillin/tazobactam resistance in invasive Haemophilus influenzae in Germany

Background

Haemophilus influenzae (Hi) is a Gram-negative bacterium that may cause sepsis or meningitis, treatment of which mainly includes β-lactam antibiotics. Since 2019 EUCAST breakpoints for piperacillin/tazobactam have been available. Little is known about the prevalence and mechanisms of piperacillin/tazobactam resistance in Hi.

Objectives

To provide reliable prevalence data for piperacillin/tazobactam resistance in Hi in Germany, to evaluate different antibiotic susceptibility testing methods and to examine possible resistance mechanisms.

Methods

According to EUCAST breakpoints, the MIC for piperacillin/tazobactam resistance is >0.25 mg/L. All invasive Hi in Germany from 2019 were examined by gradient agar diffusion (GAD) for piperacillin/tazobactam susceptibility. Piperacillin/tazobactam broth microdilution (BMD), piperacillin GAD on tazobactam-containing agar [piperacillin GAD on Mueller-Hinton agar with horse blood (MH-F)/tazobactam) and piperacillin/tazobactam agar dilution (AD) were used for confirmation. Phenotypic testing was complemented by ftsI sequencing.

Results

Piperacillin/tazobactam GAD resulted in 2.9% (21/726) resistant Hi. BMD did not confirm piperacillin/tazobactam resistance. Two strains were found resistant by AD, of which one was also resistant using piperacillin GAD on MH-F/tazobactam. Overall, we found two strains with a piperacillin/tazobactam MIC >0.25 mg/L in at least two different tests (0.3%). Both were β-lactamase-producing amoxicillin/clavulanate-resistant with PBP3 mutations characterized as group III-like+. Relevant PBP3 mutations occurred in six strains without phenotypic piperacillin/tazobactam resistance. These mutations suggest a reduced efficacy of β-lactam antibiotics in these isolates.

Conclusions

Piperacillin/tazobactam resistance prevalence in invasive Hi is low in Germany. Reduced susceptibility was correlated with PBP3 mutations, in particular with group III mutations.

Haemophilus influenzae blood-stream infection and third-generation cephalosporin susceptibility testing: a comparative case study using EUCAST and CLSI guidelines

Introduction

In this comparative case study, we discuss clinically relevant discrepancies of antimicrobial susceptibility testing (AST) interpretation for ceftriaxone against a non-typable, beta-lactamase negative, ampicillin-resistant (BLNAR) Haemophilus influenzae isolated from a blood culture.

Case report

A 74-year-old man presented with a 3 day illness characterized by shortness of breath and dry cough, and was noted to be febrile and hypoxic on admission. A blood culture bottle flagged positive with Gram-negative coccobacilli, later identified as Haemophilus influenzae with the patient commenced on ceftriaxone. The isolate was beta-lactamase negative and antibiotic susceptibility testing (AST) using disc diffusion revealed the isolate resistant to ceftriaxone and ampicillin by EUCAST methodology, with the patient subsequently changed to amoxicillin/clavulanate. Further AST using the CLSI methodology in parallel demonstrated discrepant results between the two susceptibility methods. The patient recovered without complications.

Conclusion

This discrepancy could lead to inconsistent reporting of susceptibilities between laboratories, and consequently antibiotic prescribing, especially for invasive isolates. As more laboratories adopt EUCAST methodologies for AST interpretation in Australia and globally, it is important for clinicians to consider the clinical implications of these methodological discrepancies.

Clinical epidemiology and case fatality due to antimicrobial resistance in Germany: a systematic review and meta-analysis, 1 January 2010 to 31 December 2021

BackgroundAntimicrobial resistance (AMR) is of public health concern worldwide.AimWe aimed to summarise the German AMR situation for clinicians and microbiologists.MethodsWe conducted a systematic review and meta-analysis of 60 published studies and data from the German Antibiotic-Resistance-Surveillance (ARS). Primary outcomes were AMR proportions in bacterial isolates from infected patients in Germany (2016-2021) and the case fatality rates (2010-2021). Random and fixed (common) effect models were used to calculate pooled proportions and pooled case fatality odds ratios, respectively.ResultsThe pooled proportion of meticillin resistance in Staphylococcus aureus infections (MRSA) was 7.9% with a declining trend between 2014 and 2020 (odds ratio (OR) = 0.89; 95% CI: 0.886-0.891; p < 0.0001), while vancomycin resistance in Enterococcus faecium (VRE) bloodstream infections increased (OR = 1.18; (95% CI: 1.16-1.21); p < 0.0001) with a pooled proportion of 34.9%. Case fatality rates for MRSA and VRE were higher than for their susceptible strains (OR = 2.29; 95% CI: 1.91-2.75 and 1.69; 95% CI: 1.22-2.33, respectively). Carbapenem resistance in Gram-negative pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, Enterobacter spp. and Escherichia coli) was low to moderate (< 9%), but resistance against third-generation cephalosporins and fluoroquinolones was moderate to high (5-25%). Pseudomonas aeruginosa exhibited high resistance against carbapenems (17.0%; 95% CI: 11.9-22.8), third-generation cephalosporins (10.1%; 95% CI: 6.6-14.2) and fluoroquinolones (24.9%; 95% CI: 19.3-30.9). Statistical heterogeneity was high (I2 > 70%) across studies reporting resistance proportions.ConclusionContinuous efforts in AMR surveillance and infection prevention and control as well as antibiotic stewardship are needed to limit the spread of AMR in Germany.

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.

Molecular epidemiology and antibiotic resistance profiles of invasive Haemophilus influenzae from Norway 2017-2021

Invasive Haemophilus influenzae (Hi) disease has decreased in countries that included Hi type b (Hib) vaccination in their childhood immunization programs in the 1990s. Non-typeable (NT) and non-b strains are now the leading causes of invasive Hi disease in Europe, with most cases reported in young children and the elderly. Concerningly, no vaccines toward such strains are available and beta-lactam resistance is increasing. We describe the epidemiology of invasive Hi disease reported to the Norwegian Surveillance System for Communicable Diseases (MSIS) (2017-2021, n = 407). Whole-genome sequencing (WGS) was performed on 245 isolates. We investigated the molecular epidemiology (core genome phylogeny) and the presence of antibiotic resistance markers (including chromosomal mutations associated with beta-lactam or quinolone resistance). For isolates characterized with both WGS and phenotypic antibiotic susceptibility testing (AST) (n = 113) we assessed correlation between resistance markers and susceptibility categorization by calculation of sensitivity, specificity, and predictive values. Incidence rates of invasive Hi disease in Norway ranged from 0.7 to 2.3 per 100,000 inhabitants/year (mean 1.5 per 100,000) and declined during the COVID-19 pandemic. The bacterial population consisted of two major phylogenetic groups with subclustering by serotype and multi-locus sequence type (ST). NTHi accounted for 71.8% (176). The distribution of STs was in line with previous European reports. We identified 13 clusters, including four encapsulated and three previously described international NTHi clones with bla TEM-1 (ST103) or altered PBP3 (rPBP3) (ST14/IIA and ST367/IIA). Resistance markers were detected in 25.3% (62/245) of the isolates, with bla TEM-1 (31, 50.0%) and rPBP3 (28, 45.2%) being the most frequent. All isolates categorized as resistant to aminopenicillins, tetracycline or chloramphenicol possessed relevant resistance markers, and the absence of relevant substitutions in PBP3 and GyrA/ParC predicted susceptibility to cefotaxime, ceftriaxone, meropenem and quinolones. Among the 132 WGS-only isolates, one isolate had PBP3 substitutions associated with resistance to third-generation cephalosporins, and one isolate had GyrA/ParC alterations associated with quinolone resistance. The detection of international virulent and resistant NTHi clones underlines the need for a global molecular surveillance system. WGS is a useful supplement to AST and should be performed on all invasive isolates.