Ampicillin-resistant Haemophilus influenzae isolates in Geneva: serotype, antimicrobial susceptibility, and β-lactam resistance mechanisms

Impact of the COVID-19 pandemic on Haemophilus influenzae infections in pediatric patients hospitalized with community acquired pneumonia

The COVID-19 pandemic has altered the infection landscape for many pathogens. This retrospective study aimed to compare Haemophilus influenzae (H. influenzae) infections in pediatric CAP patients hospitalized before (2018-2019) and during (2020-2022) the COVID-19 pandemic. We analyzed the clinical epidemiology and antimicrobial resistance (AMR) patterns of H. influenzae from a tertiary hospital in southwest China. A total of 986 pediatric CAP patients with H. influenzae-associated infections were included. Compared to 2018, the positivity rate increased in 2019 but dropped significantly in 2020. Although it rose in the following 2 years, the rate in 2022 remained significantly lower than in 2019. Patients' age during the pandemic was significantly higher than in 2018 and 2019, while gender composition remained similar across both periods. Notably, there were significant changes in co-infections with several respiratory pathogens during the pandemic. Resistance rates of H. influenzae isolates to antibiotics varied, with the highest resistance observed for ampicillin (85.9%) and the lowest for cefotaxime (0.0%). Resistance profiles to various antibiotics underwent dramatic changes during the COVID-19 pandemic. Resistance to amoxicillin-clavulanate, cefaclor, cefuroxime, trimethoprim-sulfamethoxazole, and the proportion of multi-drug resistant (MDR) isolates significantly decreased. Additionally, MDR isolates, alongside isolates resistant to specific drugs, were notably prevalent in ampicillin-resistant and β-lactamase-positive isolates. The number of pediatric CAP patients, H. influenzae infections, and isolates resistant to certain antibiotics exhibited seasonal patterns, peaking in the winter of 2018 and 2019. During the COVID-19 pandemic, sharp decreases were observed in February 2020, and there was no resurgence in December 2022. These findings indicate that the COVID-19 pandemic has significantly altered the infection spectrum of H. influenzae in pediatric CAP patients, as evidenced by shifts in positivity rate, demographic characteristics, respiratory co-infections, AMR patterns, and seasonal trends.

Characterization of Serotypes and Molecular Drug Resistance Patterns of Haemophilus influenzae in Kunming Children

The present study aimed to determine the capsular serotype distribution and antimicrobial drug resistance patterns of Haemophilus influenzae from children in the Kunming region of China. This information could guide policymakers in clinical treatment. In the present study, H. influenzae isolates were tested for their serotypes, antimicrobial susceptibility pattern, and presence of β-lactamases. One-hundred forty-eight H. influenzae strains isolated from children 0-2 years old were investigated for capsular types by glass slide agglutination and molecular methods, and biotyped by the biochemical reactions. The drug resistance-encoding genes TEM-1, ROB-1, and the ftsI gene mutations PBP3-3, and PBP3-BLN were detected with real-time quantitative polymerase chain reaction (qPCR). The prevalence of β-lactamase-producing strains (60.3%) was significantly higher (p < 0.05) than non-enzyme-producing strains. β-Lactamase-producing strains were multidrug resistant to various antibiotics such as ampicillin, tetracycline, sulfamethoxazole/trimethoprim, chloramphenicol, cefuroxime, and cefaclor. Among β-lactamase-producing strains, the detection rates of the TEM-1, PBP3-BLN, PBP3-s, and ROB-1 were 54.1%, 18.9%, 11.8%, and 6.9%, respectively. The biotyping results show that most H. influenzae strains were of type II and III. Non-typeable H. influenzae (NTHi) accounted for 89.3% of the strains. NTHi strains were the most prevalent in this region; most belonged to biological types II and III. β-Lactamase-positive ampi-cillin-resistant (BLPAR) strains were prevalent among H. influenzae isolates in this region.

Highlights Regarding the Use of Metallic Nanoparticles against Pathogens Considered a Priority by the World Health Organization

The indiscriminate use of antibiotics has facilitated the growing resistance of bacteria, and this has become a serious public health problem worldwide. Several microorganisms are still resistant to multiple antibiotics and are particularly dangerous in the hospital and nursing home environment, and to patients whose care requires devices, such as ventilators and intravenous catheters. A list of twelve pathogenic genera, which especially included bacteria that were not affected by different antibiotics, was released by the World Health Organization (WHO) in 2017, and the research and development of new antibiotics against these genera has been considered a priority. The nanotechnology is a tool that offers an effective platform for altering the physicalchemical properties of different materials, thereby enabling the development of several biomedical applications. Owing to their large surface area and high reactivity, metallic particles on the nanometric scale have remarkable physical, chemical, and biological properties. Nanoparticles with sizes between 1 and 100 nm have several applications, mainly as new antimicrobial agents for the control of microorganisms. In the present review, more than 200 reports of various metallic nanoparticles, especially those containing copper, gold, platinum, silver, titanium, and zinc were analyzed with regard to their anti-bacterial activity. However, of these 200 studies, only 42 reported about trials conducted against the resistant bacteria considered a priority by the WHO. All studies are in the initial stage, and none are in the clinical phase of research.

Epidemiologic study of Haemophilus influenzae causing invasive and non-invasive disease in Paraguay (1999-2017)

INTRODUCTION

Haemophilus influenzae is a cause of mild and severe invasive infections, especially among children under 5 years old. Serotype b (Hib) was very frequent before the introduction of the vaccine, which was introduced in Paraguay in 2004.

METHODS

A total of 523 isolates of H. influenzae obtained from 1999 to 2017 and referred to the National Reference Laboratory in Paraguay were studied by conventional microbiological methods and molecular techniques.

RESULTS

The most frequent serotype was non-typeable (HiNT) (51.8%; 271/523), followed by Hib (43%; 225/523), Hia and Hif (1.5%; 8/523, respectively), Hic (1%; 5/523), Hie (0.8%; 4/523), and Hid (0.4%; 2/523). A total of 48.4% invasive infections were caused by HiNT, and 46.1% by Hib; 88.6% of isolates corresponded to meningitis, 70.8% to sepsis and 50.9% to pneumonia in children under 5 years. A total of 84% (181/217) of isolates corresponded to invasive infections caused by Hib in children under 5 years, with the highest proportion observed between 2001 and 2003. The most prevalent biotypes were biotype I (29%), biotype II (12%), biotype III (24%), and biotype IV (13%). Among the total of isolates, 13% (68/523) of isolates were resistant to ampicillin.

CONCLUSION

After the introduction of the Hib vaccine in Paraguay, the number of invasive Hib cases decreased in children under 5 years old, although we observed an increase of HiNT in children over 5 years. Continuous surveillance is necessary in order to monitor the effectiveness of the vaccine and for the development of preventive interventions.

Lower respiratory tract isolates of non-typeable Haemophilus influenzae in Western Sichuan, China: Antimicrobial susceptibility, mechanisms of β-lactam resistance and decade changes

OBJECTIVES

The aims of this study were to analyse the serotypes of epidemic Haemophilus influenzae and changes in mechanisms of β-lactam resistance over the past decade.

RESULTS

Haemophilus influenzae isolates in Western Sichuan from 2013-2014 were non-typeable H. influenzae (NTHi). β-Lactam MICs for NTHi isolated during 2013-2014 were significantly higher than those from 2003-2004 (P < 0.05). Of 274 NTHi, 141 (51.5%) were β-lactamase-positive (TEM-1 type). There were 35 amino acid (AA) substitutions in ftsI among NTHi isolated from 2013-2014. However, NTHi isolates from 2003-2004 had only nine AA substitutions. Ordered multiple classification logistic regression analysis showed that different AA substitution patterns in ftsI had different effects on β-lactam MICs. The main factors affecting the ampicillin MIC were the mutations R517H (OR = 6.999), L389F (OR = 7.128), N526K (OR = 4.660) and D350N (OR = 0.450). The main factor influencing the amoxicillin/clavulanic acid MIC was an N526K mutation (OR = 9.349). The main factors affecting the cefuroxime MIC were the mutations S357N (OR = 37.453) and N526K (OR = 14.816). Compared with 2003-2004, gBLNAR and gBLPAR isolated from 2013-2014 increased significantly from 13.0% (7/54) and 9.3% (5/54) to 38.2% (84/220) and 45.5% (100/220), respectively (P < 0.001). In the 'others' group of ftsI gene mutations, 13 NTHi had the same ftsI gene mutation pattern and 24 AA substitutions.

CONCLUSION

These results confirm that β-lactam-resistant NTHi isolates increased rapidly. AA substitutions in ftsI were more complex and diversified in 2013-2014.

Genetic characteristics and antibiotic resistance of Haemophilus influenzae isolates from pediatric patients with acute otitis media after introduction of 13-valent pneumococcal conjugate vaccine in Japan

Acute otitis media (AOM) occurs commonly in pediatric populations. We examined resistance genotype, antibiotic susceptibility, quinolone (QL) resistance, and multilocus sequence type (MLST) among Haemophilus influenzae isolates causing AOM following introduction of pneumococcal conjugate vaccines in Japan. The AOM surveillance group included 69 participating otolaryngologists. Causative pathogens isolated from middle ear fluid (MEF) samples collected from 582 children with AOM were identified using both bacterial culture and real-time PCR. H. influenzae isolates among these pathogens were characterized by capsular type, resistance genotype, antibiotic susceptibility, QL resistance, and MLST. In 2016, H. influenzae was identified in 319 samples (54.8%), among which 72.4% (n = 231) tested positive by both culture and PCR; remaining H. influenzae cases were only PCR-positive. This proportion of H. influenzae positivity has increased significantly from 41.2% in 2006 (p < 0.001). Among culture-positive strains, genotypic β-lactamase-nonproducing ampicillin (AMP)-resistant (gBLNAR) strains were frequent (63.2%), with β-lactamase-nonproducing AMP-susceptible (gBLNAS) strains accounting for only 24.2%. Susceptibilities of gBLNAR to oral antimicrobials were best for tosufloxacin, followed by cefditoren and tebipenem; MIC₉₀s were 0.031 μg/mL, 0.5 μg/mL, and 1 μg/mL, respectively. In 7 gBLNAR isolates (3.0%), QL susceptibility was low, owing to amino acid substitutions in GyrA and/or ParC. Sequence types identified numbered 107, including 28 that were new. Prevention of further increases in resistance to antimicrobial agents will require antibiotic selection based on characterization of causative pathogens in clinical practice.

Increasing Prevalence of Group III Penicillin-Binding Protein 3 Mutations Conferring High-Level Resistance to Beta-Lactams Among Nontypeable Haemophilus influenzae Isolates from Children in Korea

This study investigated the roles of β-lactamase and penicillin-binding protein 3 (PBP3) alterations in the development of recent antimicrobial resistance in nontypeable Haemophilus influenzae (NTHi) isolated from Korean children. Nasopharyngeal NTHi isolates from children at a tertiary children's hospital were tested for antimicrobial susceptibility using E-test. β-lactamase production was screened by the paper disc test, and polymerase chain reaction amplification of bla_TEM and bla_ROB-1 was performed. The ftsI gene was amplified to identify PBP3 alteration. Of the 53 NTHi isolates, 69.8% were ampicillin nonsusceptible. The nonsusceptibility rates for cefaclor were 81.1%, cefpodoxime 69.8%, and amoxicillin/clavulanate 32.1%. About 60.3% and 32.1% of the isolates were genetically β-lactamase-nonproducing ampicillin-resistant (gBLNAR) and genetically β-lactamase-producing amoxicillin/clavulanate-resistant (gBLPACR) strains, respectively. Group III amino acid substitutions comprised 65.6% of the gBLNAR strains and 70.6% of the gBLPACR strains. MIC₅₀ for amoxicillin/clavulanate, cefaclor, cefuroxime, cefpodoxime, and cefixime were more than 2-80 times higher in the gBLNAR and gBLPACR strains compared with gBLPAR strains. Group III gBLNAR strains had significantly higher ampicillin, amoxicillin/clavulanate, cefpodoxime, and cefixime minimum inhibitory concentrations than group II strains. Group III gBLNAR and gBLPACR NTHi strains are highly prevalent in Korea, raising the alarm about increasing β-lactam resistance in NTHi.

β-Lactam resistance among Haemophilus influenzae isolates in Poland

OBJECTIVES

Haemophilus influenzae is a human-specific Gram-negative coccobacillus responsible for a significant number of respiratory tract infections and severe invasive infections such as meningitis and sepsis. The purpose of this study was to characterise the mechanisms of β-lactam resistance among Polish H. influenzae isolates and to evaluate the resistance detection methods applied.

METHODS

This study was conducted on 117 Polish H. influenzae isolates collected in 2012. Minimum inhibitory concentrations were assessed by broth microdilution. All strains were evaluated using the disk diffusion method and the algorithm proposed by the Nordic Committee on Antimicrobial Susceptibility Testing (NordicAST). To detect changes in penicillin-binding protein 3 (PBP3), PCR screening was performed, followed by ftsI gene sequencing.

RESULTS

Neither β-lactamase production nor PBP3 alterations were demonstrated in 76 isolates (65.0%). Susceptibility to ampicillin, amoxicillin, amoxicillin/clavulanic acid, cefuroxime (intravenous) and ceftriaxone was observed in 70.9%, 78.6%, 98.3%, 82.9% and 100% of the isolates, respectively. β-Lactamase production characterised 21 isolates (17.9%). Screening PCR identified 20 isolates (17.1%) with PBP3 alterations, and according to subsequent ftsI sequencing all these strains were finally recognised as gBLNAR (genetically β-lactamase-negative, ampicillin-resistant), among which 65.0% were ampicillin-resistant. According to molecular classification of PBP3 alterations, 95.0% of gBLNAR belonged to group II, representing four subgroups IIa-IId.

CONCLUSIONS

Haemophilus influenzae resistance to antibiotics requires continuous attention, effective detection methods and a rational policy of antibiotic usage. The algorithm proposed by NordicAST can be applied in routine laboratory work, whereas sequencing of the ftsI gene may be useful in molecular epidemiology studies.

Rapid identification of ST131 Escherichia coli by a novel multiplex real-time allelic discrimination assay

Escherichia coli sequence type 131 is increasingly described in severe hospital infections. We developed a rapid real-time allelic discrimination assay for the rapid identification of E. coli ST131 isolates. This rapid assay represents an affordable alternative to sequence-based strategies before completing characterization of potentially highly virulent isolates of E. coli.

Ampicillin resistance in Haemophilus influenzae from COPD patients in the UK

BACKGROUND

Haemophilus influenzae is commonly isolated from the airways of COPD patients. Antibiotic treatment may cause the emergence of resistant H. influenzae strains, particularly ampicillin-resistant strains, including β-lactamase-negative ampicillin resistance (BLNAR) strains. Genetic identification using ftsI sequencing is the optimum method for identifying mutations within BLNAR strains. The prevalence of BLNAR in COPD patients during the stable state has not been reported. We investigated the antibiotic resistance patterns of H. influenzae present in the sputum of stable COPD patients, focusing on ampicillin resistance; the prevalence of enzyme and non-enzyme-mediated ampicillin resistance was determined. A subset of patients was followed up longitudinally to study H. influenzae strain switching and antibiotic sensitivity changes.

PATIENTS AND METHODS

Sputum sampling was performed in 61 COPD patients, with 42 samples obtained at baseline; H. influenzae was detected by polymerase chain reaction in 28 samples. In all, 45 patients completed the follow-up for 2 years; 24 H. influenzae isolates were obtained.

RESULTS

Disk diffusion showed the highest antibiotic resistance in the penicillin antibiotic group (eg, 67% for ampicillin) and macrolides (eg, 46% for erythromycin), whereas all isolates were susceptible to quinolones. Of the 16 isolates resistant to ampicillin, 9 (56%) were β-lactamase positive. The β-lactamase-negative isolates were further investigated; none of these fulfilled the phenotypic BLNAR classification criteria of ampicillin minimum inhibitory concentration >1 µg/mL, and only one demonstrated an ftsI mutation. Frequent H. influenzae strain switching was confirmed using multilocus sequence typing and was associated with changes in the antibiotic sensitivity pattern.

CONCLUSION

We observed an overidentification of ampicillin resistance by disk diffusion. The majority of ampicillin resistance was due to enzyme production. H. influenzae strain changes during the stable state may be associated with a change in antibiotic sensitivity; this has implications for empirical antibiotic prescribing.

The most appropriate therapeutic strategy for acute lower respiratory tract infections: a Delphi-based approach

Lower respiratory tract infections (LRTIs) cause high morbidity and mortality worldwide. Empiric therapy often base the choice of antibiotic treatment on antibacterial spectrum of the agent rather than on its pharmacological properties or the pathogen resistance profile. Inappropriate prescribing leads to therapeutic failure and antibiotic resistance, with increasing direct and indirect health costs. A consensus on appropriate prescribing in LRTI therapy was appraised by this Delphi exercise, based on a panel of 70 pulmonologists, coordinated by a Scientific Committee of nine experts in respiratory medical care. Full or very high consensus was reached on several issues, including the role of oral cephalosporins in first-line treatments of LRTIs and the appropriateness of cefditoren, with balanced spectrum and high intrinsic activity, in LRTI treatment. Evidence-based medicine approach and a comprehensive process of disease management, from diagnosis to therapy and follow-up, should guide antibiotic prescribing.

Imipenem heteroresistance in nontypeable Haemophilus influenzae is linked to a combination of altered PBP3, slow drug influx and direct efflux regulation

OBJECTIVE

To investigate the potential roles of PBPs, efflux pumps and slow drug influx for imipenem heteroresistance in nontypeable Haemophilus influenzae (NTHi).

METHODS

Fifty-nine NTHi clinical isolates examined in this study were collected at Geneva University Hospitals between 2009 and 2014. Alterations in PBPs were investigated by gene sequencing. To evaluate the affinities of the PBPs to imipenem, steady-state concentration-response experiments were carried out using imipenem in a competition assay with Bocillin-FL. The effect of the carbonyl cyanide m-chlorophenylhydrazone (CCCP) on imipenem susceptibility was assessed using broth dilution and viable cell counting. Using whole-genome sequencing, we explored the potential roles of outer membrane protein P2 (OmpP2), LytM proteins and the dcw gene cluster in imipenem heteroresistance.

RESULTS

All 46 imipenem-heteroresistant isolates (IMI^hR) harboured amino acid substitutions in the ftsI gene, which encodes PBP3, corresponding to 25 different mutation patterns that varied from the ftsI gene mutation patterns found in imipenem-susceptible isolates. Among all PBPs, the highest affinity to imipenem was documented for PBP3 (IC₅₀, 0.004 μg/mL). Different amino acid substitutions and insertions were noted in OmpP2, suggesting a relationship with imipenem heteroresistance. The IMI^hR isolates were affected by CCCP differently and displayed a higher percentage of killing by imipenem in CCCP-treated cells at concentrations ranging between 0.5 and 8 μg/mL.

CONCLUSIONS

The present study provides robust evidence indicating that in combination with the altered PBP3, the slowed drug influx and its enhanced efflux due to the loss of regulation led to the development of imipenem heteroresistance in NTHi.