Genetic relatedness of antibiotic resistance determinants in multiply resistant Hemophilus influenzae

Extensively drug-resistant Haemophilus influenzae - emergence, epidemiology, risk factors, and regimen

Background

Concern about Haemophilus influenzae infection has been increasing over recent decades. Given the emergence of H. influenzae with severe drug resistance, we assessed the prevalence of as well as risk factors and potential therapies for extensively drug-resistant (XDR) H. influenzae infection in Taiwan.

Results

In total, 2091 H. influenzae isolates with disk diffusion-based antibiotic susceptibility testing from 2007 to 2018 were enrolled. H. influenzae strains resistant to ampicillin, chloramphenicol, levofloxacin, and trimethoprim-sulfamethoxazole tended to be isolated from patient wards (≧41%), whereas those resistant to amoxicillin-clavulanate, cefotaxime, and cefuroxime were more likely to be isolated from intensive care units (approximately 50%). XDR H. influenzae was first identified in 2007, and its incidence did not significantly change thereafter. Overall prevalence of single, multiple, and extensively drug-resistant H. influenzae over 2007–2018 was 21.5% (n = 450), 26.6% (n = 557), and 2.5% (n = 52), respectively. A stepwise logistic regression analysis revealed that blood culture (odds ratio: 4.069, 95% confidence intervals: 1.339–12.365, P = 0.013) was an independent risk factor for XDR H. influenzae infection. No nosocomial transmission of XDR H. influenzae observed. Antibiotic susceptibility testing results demonstrated that cefotaxime was effective against 78.8% (n = 41) of the XDR strains.

Conclusions

The presence of XDR H. influenzae strains was identified in Taiwan, and cefotaxime was efficacious against most of these strains.

Meningitis due to ampicillin-and chloramphenicol-resistant Haemophilus influenzae type b in Canada. Case report and review

The first report of a case of ampicillin- and chloramphenicol-resistant Haemophilus influenzae type b invasive infection in Canada is described in a four-month-old male with meningitis. He was treated with cefotaxime 200 mg/kg/day divided every 6 h and dexamethasone 0.6 mg/kg/day divided every 6 h, eventually recovering after a complicated course. Follow-up at 21 months showed mild to moderate global developmental delay. While chloramphenicol resistance is rare in North America, a case of meningitis initially unresponsive to ampicillin and chloramphenicol must be considered suspect for resistance. Third generation cephalosporins should be used for resistant cases.

Antimicrobial resistance in Haemophilus influenzae

Haemophilus influenzae is a major community-acquired pathogen causing significant morbidity and mortality worldwide. Meningitis and bacteremia due to type b strains occur in areas where the protein-conjugated type b vaccine is not in use, whereas nontypeable strains are major causes of otitis media, sinusitis, acute exacerbations of chronic bronchitis, and pneumonia. Antibiotic resistance in this organism is more diverse and widespread than is commonly appreciated. Intrinsic efflux resistance mechanisms limit the activity of the macrolides, azalides, and ketolides. beta-Lactamase production is highly prevalent worldwide and is associated with resistance to ampicillin and amoxicillin. Strains with alterations in penicillin binding proteins, particularly PBP3 (beta-lactamase negative ampicillin resistant and beta-lactamase positive amoxicillin-clavulanate resistant), are increasing in prevalence, particularly in Japan, with increasing resistance to ampicillin, amoxicillin, amoxicillin-clavulanate, and many cephalosporins, limiting the efficacy of expanded-spectrum cephalosporins against meningitis and of many oral cephalosporins against other diseases. Most strains remain susceptible to the carbapenems, which are not affected by penicillin binding protein changes, and the quinolones. The activity of many oral agents is limited by pharmacokinetics achieved with administration by this route, and the susceptibility of isolates based on pharmacokinetic and pharmacodynamic parameters is reviewed.

Ampicillin-resistant non-beta-lactamase-producing Haemophilus influenzae in Spain: recent emergence of clonal isolates with increased resistance to cefotaxime and cefixime

The sequence of the ftsI gene encoding the transpeptidase domain of penicillin-binding protein 3 (PBP 3) was determined for 354 nonconsecutive Haemophilus influenzae isolates from Spain; 17.8% of them were ampicillin susceptible, 56% were beta-lactamase nonproducing ampicillin resistant (BLNAR), 15.8% were beta-lactamase producers and ampicillin resistant, and 10.4% displayed both resistance mechanisms. The ftsI gene sequences had 28 different mutation patterns and amino acid substitutions at 23 positions. Some 93.2% of the BLNAR strains had amino acid substitutions at the Lys-Thr-Gly (KTG) motif, the two most common being Asn526 to Lys (83.9%) and Arg517 to His (9.3%). Amino acid substitutions at positions 377, 385, and 389, which conferred cefotaxime and cefixime MICs 10 to 60 times higher than those of susceptible strains, were found for the first time in Europe. In 72 isolates for which the repressor acrR gene of the AcrAB efflux pump was sequenced, numerous amino acid substitutions were found. Eight isolates with ampicillin MICs of 0.25 to 2 microg/ml showed changes that predicted the early termination of the acrR reading frame. Pulsed-field gel electrophoresis analysis demonstrated that most BLNAR strains were genetically diverse, although clonal dissemination was detected in a group of isolates presenting with increased resistance to cefotaxime and cefixime. Background antibiotic use at the community level revealed a marked trend toward increased amoxicillin-clavulanic acid consumption. BLNAR H. influenzae strains have arisen by vertical and horizontal spread and have evolved to adapt rapidly to the increased selective pressures posed by the use of oral penicillins and cephalosporins.

High ampicillin resistance in different biotypes and serotypes of Haemophilus influenzae colonizing the nasopharynx of healthy school-going Indian children

Haemophilus influenzaeis one of the main causes of otitis media, sinusitis, meningitis, pneumonia and septicaemia in children, and the development of ampicillin resistance inH. influenzaeis a cause of serious concern. The aim of the present study was to determine the prevalence of ampicillin resistance inH. influenzaecolonizing the nasopharynx of school-going healthy North Indian children, and to compare the distribution of different biotypes and serotype b in this population. A total of 2400 school-going healthy children from 45 rural and 45 urban schools were enrolled. Nasopharyngeal swabs were collected from the children and cultured.H. influenzaewas isolated from 1001 (41·7 %) of the 2400 nasopharyngeal swabs collected. All theseH. influenzaeisolates were biotyped and serotyped, and their antibiotic susceptibility tested. All eight biotypes were present in this population. The most prevalent biotypes were I (19·6 %), II (16·8 %) and III (25·0 %). Of the 1001 isolates, 316 (31·6 %) wereH. influenzaetype b and 685 (68·4 %) were non-type bH. influenzae, and 22·9 % were resistant to ampicillin, 41·9 % to chloramphenicol, 27·5 % to erythromycin and 67·3 % to co-trimoxazole. Of the 316H. influenzaetype b isolates, 44·0 % were ampicillin resistant, while only 13·1 % non-type bH. influenzaeisolates were ampicillin resistant. Of the 229 ampicillin-resistantH. influenzaeisolates, 196 (85·6 %) were positive forβ-lactamase; 93·4 % (214/229) were biotypes I, II and III, of which 49 % were biotype I, 27·9 % were type II and 16·6 % were type III. Most of the strains belonging to biotypes III–VIII were ampicillin sensitive. Ampicillin resistance is significantly more common in biotype I and serotype b than in other biotypes and serotypes.

Analysis of invasive Haemophilus influenzae infections after extensive vaccination against H. influenzae type b

Little clinical and microbiological information is available about invasive Haemophilus influenzae infection after widespread vaccination against H. influenzae type b (Hib). We conducted an active community surveillance study on invasive H. influenzae during a 2-year period in a community of more than 5 million people after vaccination against Hib in children was introduced. The median incidence was 16.3 cases/100000 persons per year in children less than 1-year-old and 4.41 cases/100000 persons in children less than <5 years old. The highest incidence in adults was observed in patients greater than 70 years old. Clinical diagnoses included bacteremia, pneumonia, and meningitis. Of the H. influenzae-infected patients, 74.3% had underlying predisposing conditions, including impaired immunity and respiratory diseases. A total of 73.6% of the isolates were nontypeable and 16.5, 6.6, and 3.3% were types b, f, and e, respectively. Infections due to capsulated strains b, e, and f were evenly distributed between children and adults. Ampicillin and cotrimoxazole resistance occurred at frequencies of 24.2 and 48.4%, respectively. Antibiotic resistance was more prevalent in capsulated than in noncapsulated H. influenzae. Invasive isolates were highly resistant to antibiotics that were used infrequently in the community. Nontypeable H. influenzae were genetically much more heterogeneous than capsulated strains. Capsule-deficient mutants (b(-)) were not detected. Plasmid carriage was linked to antibiotic resistance and capsulated strains. Over the study period, the incidence of invasive H. influenzae infections, either encapsulated or not, did not increase. In the post-Hib vaccination era, most invasive infections were due to noncapsulated strains and occurred in the extreme ages of life in patients with predisposing conditions.

Levofloxacin Treatment Failure inHaemophilus influenzaePneumonia

We describe the first case of failure of oral levofloxacin treatment of community-acquired pneumonia caused by Haemophilus influenzae. The strain showed cross-resistance to fluoroquinolones and carried four mutations in quinolone resistance-determining regions of DNA gyrase and topoisomerase IV genes.

Infections due to Haemophilus influenzae serotype E: microbiological, clinical, and epidemiological features

Surveillance after introduction of Haemophilus influenzae serotype b vaccination in Spain identified 26 H. influenzae serotype e (HiE) isolates. Of these, 16 (61.5%) were recovered from patients aged >16 years and 10 (38.5%) from children <16 years of age. HiE caused respiratory infections in 14 patients (9 with pneumonia), conjunctivitis in 4, vaginitis in 2, abscess in 2, and cellulitis, peritoneal infection, sepsis and meningitis in 1 patient each. HiE was strongly clonal and highly resistant to ampicillin and cotrimoxazole, and the incidence of HiE infection did not increase over time.

Antibiotic medication and bacterial resistance to antibiotics: a survey of children in a Vietnamese community

OBJECTIVE

To investigate antibiotic use and antibiotic susceptibility of respiratory tract pathogens in children aged 1-5 years in Bavi, Vietnam.

METHOD

Nasopharynx and throat specimens were collected from 200 children from randomly selected households in a demographically defined population. Respiratory isolates were tested for antibiotic susceptibility according to the standard disk diffusion method. A questionnaire survey of carers elicited information on type of antibiotic used, duration of treatment, where the antibiotics had been purchased, type of treatment information retained by carers and episodes of illness preceding the study.

RESULTS

82% of the children had at least one symptom of acute respiratory tract infection (ARI) in the 4 weeks prior to the study, and of these 91% were treated with antibiotics. The most commonly used antibiotics were ampicillin (74%), penicillin (12%), amoxicillin (11%), erythromycin (5%), tetracycline (4%) and streptomycin (2%). Ampicillin was used for 3.3 days on average (SD:1.8) and penicillin for 2.6 days (SD:0.7). When deciding which antibiotic to use, 67% of the carers consulted the pharmacy seller, 11% decided themselves and 22% followed the doctor's prescription. The carrier rate of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis was 50%, 39% and 17%, respectively. Isolates from 145 children were susceptibility tested, and 74% were found to carry resistant pathogens. Of the tested isolates, 90% of S. pneumoniae, 68% of H. influenzae and 74% of M. catarrhalis were resistant to at least one antibiotic. The mean number of antibiotics (susceptible strains excluded) to which resistance was found was 2.0 (SD:1.2), 2.5 (SD:1.8) and 2.1 (SD:0.9), respectively. S. pneumoniae and H. influenzae showed high resistance to tetracycline (88% and 32%, respectively), trimethoprim/sulphonamide (32% and 44%), and chloramphenicol (25% and 24%). 23% of S. pneumoniae were erythromycin-resistant and 18% of H. influenzae isolates were resistant to ampicillin. There was a significant difference in ampicillin and penicillin resistance between the group of children previously treated with beta lactam antibiotics and the group of children who did not receive antibiotics.

CONCLUSION

As reported by the carers, children in Bavi are treated with antibiotics frequently. Most antibiotics were obtained without consulting a doctor. High levels of antibiotic resistance and high prevalence of multidrug-resistant strains were found among respiratory pathogens. The existence of a large reservoir of resistance genes among children in low-income countries represents a threat to the success of antibiotic therapy throughout the world. Multi-faceted programmes to improve rational use of antibiotics in Vietnam are urgently needed.

Antibiotic resistance in Haemophilus influenzae: mechanisms, clinical importance and consequences for therapy

Invasive and non-invasive infections caused by Haemophilus influenzae are frequently diagnosed in children below the age of 5 years. The treatment of choice for these infections was ampicillin. However, since the early 1970s the increasing prevalence of resistance to ampicillin and other antibiotics has necessitated major changes in antibiotic therapy. This article summarizes some of the important clinical features of diseases caused by H. influenzae. The epidemiology, the problems with in vitro susceptibility testing and the mechanisms of resistance to major antibiotics are reviewed. The consequences of antibiotic resistance for the treatment of diseases caused by H. influenzae are discussed.

Antibiotic availability and use: consequences to man and his environment

Antibiotics are the cornerstone of therapy for infectious diseases affecting people living worldwide. The ability of these agents to cure infections, with little if any harm to the host, has helped to propagate their designation as "miracle drugs". This idea has continued throughout the past four decades and into the present one. To a large extent, this concept has led to the inappropriate use of these agents. The consequence of this misuse affects not only the individuals taking antibiotics, but indirectly others who may subsequently need antibiotics, but find that the infecting pathogen is resistant. This phenomenon results from the strong selective environmental effect of these drugs for resistant bacteria. Resistant pathogens have emerged and spread worldwide. In response to this global health problem, the Alliance for the Prudent Use of Antibiotics was established. This international network of concerned prescribers and users aims to improve antibiotic use and eliminate inappropriate use worldwide. Prudent use of antibiotics will not only curtail health care costs and the potential side effects to the individual taking these drugs, but also diminish the wide ecologic effects leading to selection of antibiotic resistant forms of common disease-causing agents.