Epidemiology of antibiotic resistance in Haemophilus influenzae

Emergence of a multidrug-resistant Haemophilus influenzae strain causing chronic pneumonia in a patient with common variable immunodeficiency

We report the emergence of a multidrug-resistant Haemophilus influenzae strain in a patient with common variable immunodeficiency suffering from recurrent bronchopneumonia caused by H. influenzae. After the patient had received several antibiotic therapies, a strain was isolated showing resistance to ampicillin, ampicillin/sulbactam, cefazolin, cefuroxime, ciprofloxacin, and clarithromycin. Polymerase chain reaction analyses and sequencing revealed the presence of the beta-lactamase gene bla(TEM-1), two mutations (A502T and R517H) in the ftsI gene encoding the transpeptidase region of the penicillin-binding protein 3, and one mutation in the ribosomal protein gene L4 (G65D) conferring resistance to beta-lactams and macrolides, respectively. Additionally, the plasmid-encoded aac(6')-Ib-cr gene mediating slightly reduced susceptibility to quinolones and two mutations in the DNA gyrase gene gyrA and one mutation in the topoisomerase IV gene parC were identified leading to a high-level fluoroquinolone-resistant phenotype. In conclusion, the treatment of H. influenzae infections accompanied by high bacterial loads such as bronchopneumonia can be complicated by the selection of multidrug-resistant strains. Moreover, the emergence of aac(6')-Ib-cr in H. influenzae causing low fluoroquinolone resistance levels might have contributed to the selection of DNA gyrase and topoisomerase IV mutants.

Mechanisms, molecular and sero-epidemiology of antimicrobial resistance in bacterial respiratory pathogens isolated from Japanese children

Background

The clinical management of community-acquired respiratory tract infections (RTIs) is complicated by the increasing worldwide prevalence of antibacterial resistance, in particular, β-lactam and macrolide resistance, among the most common causative bacterial pathogens. This study aimed to determine the mechanisms and molecular- and sero-epidemiology of antibacterial resistance among the key paediatric respiratory pathogens in Japan.

Methods

Isolates were collected at 18 centres in Japan during 2002 and 2003 from children with RTIs as part of the PROTEKT surveillance programme. A proportion of Haemophilus influenzae isolates was subjected to sequencing analysis of the ftsI gene; phylogenetic relatedness was assessed using multilocus sequence typing. Streptococcus pneumoniae isolates were screened for macrolide-resistance genotype by polymerase chain reaction and serotyped using the capsular swelling method. Susceptibility of isolates to selected antibacterials was performed using CLSI methodology.

Results and Discussion

Of the 557 H. influenzae isolates collected, 30 (5.4%) were β-lactamase-positive [BL+], 115 (20.6%) were BL-nonproducing ampicillin-resistant (BLNAR; MIC ≥ 4 mg/L) and 79 (14.2%) were BL-nonproducing ampicillin-intermediate (BLNAI; MIC 2 mg/L). Dabernat Group III penicillin binding protein 3 (PBP3) amino acid substitutions in the ftsI gene were closely correlated with BLNAR status but phylogenetic analysis indicated marked clonal diversity. PBP mutations were also found among BL+ and BL-nonproducing ampicillin-sensitive isolates. Of the antibacterials tested, azithromycin and telithromycin were the most active against H. influenzae (100% and 99.3% susceptibility, respectively). A large proportion (75.2%) of the 468 S. pneumoniae isolates exhibited macrolide resistance (erythromycin MIC ≥ 1 mg/L); erm(B) was the most common macrolide resistance genotype (58.8%), followed by mef(A) (37.2%). The most common pneumococcal serotypes were 6B (19.7%), 19F (13.7%), 23F (13.5%) and 6A (12.8%). Telithromycin and amoxicillin-clavulanate were the most active antibacterials against S. pneumoniae (99.8% and 99.6% susceptibility, respectively).

Conclusion

Approximately one-third of H. influenzae isolates from paediatric patients in Japan are BLNAI/BLNAR, mainly as a result of clonally diverse PBP3 mutations. Together with the continued high prevalence of pneumococcal macrolide resistance, these results may have implications for the clinical management of paediatric RTIs in Japan.

Resistance patterns of selected respiratory tract pathogens in Poland

This study presents the results of a survey of the in-vitro susceptibility to antimicrobial agents of major pathogens responsible for community-acquired respiratory tract infections in Poland during 2002-2004. The collection of 1184 bacterial isolates comprised 398 Streptococcus pneumoniae, 344 Haemophilus influenzae, 302 Streptococcus pyogenes and 140 Moraxella catarrhalis. Among the pneumococcal isolates, 16.8% were penicillin-non-susceptible (PNSP), of which 80.6% were identified as multidrug-resistant. Overall, 9.0% of H. influenzae isolates were beta-lactamase-positive, although this percentage increased noticeably in the third year of the study. Based on PCR results, 12.8% of H. influenzae isolates were identified as low-level beta-lactamase-negative, ampicillin-resistant (BLNAR), and one isolate as low-level beta-lactamase-positive, amoxycillin-clavulanic acid-resistant (BLPACR). Pulsed-field gel electrophoresis (PFGE) classified 45 H. influenzae isolates with altered penicillin-binding proteins into 15 PFGE types, including two predominant types (with four and six sub-types) containing 15 and ten isolates, respectively. Resistance to tetracycline, erythromycin and clindamycin was found in 20.9%, 8.9% and 4.6% of S. pyogenes isolates, respectively. The production of beta-lactamase characterised 91.4% of M. catarrhalis isolates. In summary, the overall occurrence of PNSP in Poland remains stable, although there was a noticeable increase in the proportion of fully-resistant isolates. A rising trend in the prevalence of beta-lactamase producers and low-level BLNAR isolates was observed among Polish isolates of H. influenzae.

Characteristics of Haemophilus influenzae type b responsible for meningitis in Poland from 1997 to 2004

Two hundred forty-five H. influenzae isolates responsible for meningitis in Poland from 1997 to 2004 were studied. Among these, 233 (95.1%) belonged to serotype b (Hib), 2 belonged to serotype f, and 10 were noncapsulated. The relatedness of all isolates was evaluated by pulsed-field gel electrophoresis (PFGE), and selected representatives were evaluated by multilocus sequence typing. Resistance to ampicillin was identified in 34 (14.6%) of the Hib isolates and was associated with the production of beta-lactamase only. Except for four isolates nonsusceptible to chloramphenicol, all isolates were susceptible to cefotaxime, ciprofloxacin, and rifampin. The PFGE analysis divided the Hib isolates into five PFGE types; however, all of them were possibly related. The most common PFGE type, with 25 subtypes, was characteristic for 97.4% of the isolates. The most prevalent PFGE subtype found in our study was also the most common among the Hib isolates responsible for invasive disease in Italy and the Czech Republic and was found among isolates causing lower respiratory tract infections in Poland. The most prevalent sequence types (STs) in the studied group were ST6 and ST92. Four new STs were found: ST188, ST189, ST190, and ST268. Results of this study support the evidence that the genetic structure of encapsulated H. influenzae is clonal. The continuing high number of meningitis cases due to Hib in Poland underlines the need for mass vaccination against Hib in Poland.

Prevalence and serotype distribution of encapsulated Haemophilus influenzae isolates from patients with lower respiratory tract infections in Poland

Among 1,272 H. influenzae isolates obtained from patients with lower respiratory tract infections, 5.6% were found to be encapsulated. The most common were serotypes b (40.3%) and e (38.9%) followed by serotypes f (16.7%) and d (4.1%). All encapsulated isolates within a particular serotype showed high genetic homogeneity and did not produce beta-lactamases.

Prevention and management of antibacterial resistance for primary care patients with respiratory tract infections

This review examines the problem of increasing antibacterial resistance among the pathogens commonly associated with community-acquired respiratory tract infections, particularly Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The increases in morbidity, mortality, and treatment cost associated with increased resistance to available antibiotics are challenging prescribers to find more effective therapeutic strategies. A MEDLINE search of the literature from 1966 to the present was performed to seek data relevant to the issue of resistance, especially the negative effects on patient outcomes and costs of therapy. Several observations and conclusions emerged. Data are lacking on local resistance patterns, broad-spectrum agents are overprescribed when narrower-spectrum choices would be more appropriate, a need exists for educational programs to encourage restricting drug use and changing prescribing habits, and there is a need for new antibiotic choices. The best antibiotic options are agents with a tailored spectrum of activity that are targeted at particular respiratory tract pathogens and have low potential to select for resistant organisms.

Antimicrobial resistance among invasive Haemophilus influenzae strains: results of a Brazilian study carried out from 1996 through 2000

A total of 1712 strains of Haemophilus influenzae isolated from patients with invasive diseases were obtained from ten Brazilian states from 1996 to 2000. beta-Lactamase production was assessed and the minimum inhibitory concentrations (MIC) of ampicillin, chloramphenicol, ceftriaxone and rifampin were determined using a method for broth microdilution of Haemophilus test medium. The prevalence of strains producing beta-lactamase ranged from 6.6 to 57.7%, with an overall prevalence of 18.4%. High frequency of beta-lactamase-mediated ampicillin resistance was observed in Distrito Federal (25%), São Paulo (21.7%) and Paraná (18.5%). Of the 1712 strains analyzed, none was beta-lactamase negative, ampicillin resistant. A total of 16.8% of the strains were resistant to chloramphenicol, and 13.8% of these also presented resistance to ampicillin, and only 3.0% were resistant to chloramphenicol alone. All strains were susceptible to ceftriaxone and rifampin and the MIC90 were 0.015 micro g/ml and 0.25 micro g/ml, respectively. Ceftriaxone is the drug of choice for empirical treatment of bacterial meningitis in pediatric patients who have not been screened for drug susceptibility. The emergence of drug resistance is a serious challenge for the management of invasive H. influenzae disease, which emphasizes the fundamental role of laboratory-based surveillance for antimicrobial resistance.

Prevalence of antimicrobial resistance in Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Streptococcus pyogenes: results of a multicentre study in Turkey

The in vitro activities of several antimicrobial agents against clinical isolates of Streptococcus pneumoniae (283), Haemophilus influenzae (272), Moraxella catarrhalis (179) and Streptococcus pyogenes (256) were determined in a multicentre study with the participation of five hospitals from four cities in Turkey. Penicillin resistance in S. pneumoniae was evaluated using the E-test and the remaining agents by disk diffusion. For S. pneumoniae overall 25.8% of the isolates were intermediately and 3.9% were highly resistant to penicillin and resistance to chloramphenicol, azithromycin and trimethoprim/sulphamethoxazole (TMP/SMX) was 3.8, 2.1 and 55.4%, respectively. Seven percent of H. influenzae produced beta-lactamase and all were susceptible to cefotaxime and azithromycin; the highest rate of resistance, 23.5%, was for TMP/SMX. Eighty-one percent of M. catarrhalis isolates produced beta-lactamase, 18.4% were resistant to TMP/SMX and all were susceptible to sulbactam/ampicillin combination. Resistance to chloramphenicol and azithromycin of S. pyogenes was 2.2 and 1.9%, respectively.

Susceptibility and genetic relatedness of invasive Haemophilus influenzae type b in Italy

Haemophilus influenzae type b (Hib) still causes a large portion of meningitis in children less than 5 year old in Italy because vaccination against this agent has not been fully implemented in the country. We have studied 78 Hib strains and 4 nontypable H. influenzae (NTHi) isolated from the cerebrospinal fluid of subjects with meningitis for susceptibility to ampicillin, chloramphenicol, and ceftriaxone. The macrorestriction profiles of chromosomal DNA obtained by pulsed-field gel electrophoresis (PFGE) following digestion with SmaI and ApaI were also determined. All strains except one were equally susceptible to the antibiotics tested. One Hib strain, the only beta-lactamase producer, showed an intermediate susceptibility to ampicillin (MIC = 2 microg/ml), while maintaining full susceptibility to chloramphenicol and ceftriaxone. The analysis of the PFGE patterns showed that most of the Hib isolates, including the beta-lactamase-positive Hib strain, belonged to the same clone or to closely related subclones. For three PCR-confirmed NTHi isolates, we obtained completely different PFGE profiles. In conclusion, resistance to ampicillin still appears to be a rare finding in Hib strains causing meningitis in Italy; moreover, PFGE showed that the population structure of invasive Hib is essentially clonal.

Emergence of drug resistance. Impact on bacterial meningitis

Antimicrobial resistance has emerged among the three major bacterial pathogens causing meningitis. Chloramphenicol resistance in the meningococcus recently has been described, and although intermediate penicillin resistance is common in some countries, the clinical importance of penicillin resistance in the meningococcus has yet to be established. Beta-lactamase-producing Haemophilus influenzae are relatively common, and chloramphenicol resistance is emerging. Third-generation cephalosporins are required to treat meningitis caused by these resistant strains. Pneumococcus resistance to penicillin and to chloramphenicol is widespread, and resistance to third-generation cephalosporins is found in many parts of the world. Correct management of these strains includes the addition of vancomycin or rifampin to therapy with third-generation cephalosporins.

A population-based study of antibiotic prescriptions for Danish children

BACKGROUND

The aim of the study was to examine the use of systemic and topical antibiotics in relation to age and sex in Danish children.

METHODS

We used the Pharmacoepidemiological Prescription Database to identify the individual prescriptions of antibiotics provided for all 0-to 15-year-old children in North Jutland County, Denmark, during 1997. The population was approximately 95000 children.

RESULTS

We identified 44640 prescriptions for systemic antibiotics. The annual prescription rate was highest in the 1- to 2-year-olds, with 945 prescriptions/1000 children/year. One-half of these children received at least 1 prescription, and 12% received 3 or more prescriptions. Among the 11- to 15-year-old children 17% received one or more prescriptions. Overall 88% of the prescriptions were penicillins and 10% were macrolides. In children younger than 3 years 57% of prescriptions were for broad spectrum penicillins, but in children older than 6 years penicillin V was the most frequently used antibiotic. We identified 12 661 prescriptions for topical antibiotics used in eye infections. The prescription rate peaked in the 1- to 2-year-old children, one-third of whom received at least 1 prescription.

CONCLUSIONS

Almost two-thirds of the 0- to 2-year-old children in the population were treated with either systemic or topical antibiotics during 1 year. Physicians prescribe mostly penicillins, but the proportion of broad spectrum penicillins for young children was so high, however, that enforcement of national guidelines should be reconsidered.

The potential for dissemination of Mycobacterium tuberculosis through the anesthesia breathing circuit

BACKGROUND

Respiratory pathogens that pass through the anesthesia breathing system potentially can infect other patients. This study was designed to determine if bacteria can pass through contemporary anesthesia breathing systems and if the environment within the machine is hostile to these organisms.

METHODS

Staphylococcus aureus, Pseudomonas aeruginosa, and Mycobacterium tuberculosis were nebulized into the expiratory limb of an anesthesia breathing circuit and collected from the inspiratory and expiratory limbs in an impinger system that provided a quantitative determination of the number of organisms entering the circuit and the number that would reach the patient in the inspiratory gas. Bacteria were collected before, during, and after nebulization. A second experiment determined if a saturated solution of soda lime was bactericidal.

RESULTS

When the gas flow through the circuit was interrupted for < 1 h following the nebulization period, large numbers of microorganisms (1 x 10(3) to 1 x 10(5), around 100% of the nebulized organisms) were collected from the inspiratory gas. Soda lime itself was not bactericidal for any of the organisms tested, but solutions of this material with a pH of 12 were bactericidal.

CONCLUSION

Cross contamination between patients may occur unless the gas flow through the anesthesia breathing system is interrupted for > 1 h.

Antimicrobial activities of cefditoren against respiratory pathogens isolated from children in Japan

There is an increasing spread and incidence of penicillin-resistant bacteria that are becoming less susceptible to commonly prescribed oral antimicrobials, including extended-spectrum cephalosporins. Against this background, we undertook this study to determine the prevalence of penicillin resistance in Streptococcus pneumoniae and the in-vitro activity of oral antimitrobials. Between April 1996 and December 1997, in 245 children with respiratory tract infections (bronchitis in 61, pharyngitis in 115, and tonsillitis in 69), 119 strains of Haemophilus influenzae, 89 strains of Streptococcus pyogenes, 61 strains of Streptococcus pneumoniae, 36 strains of Staphylococcus aureus, and 34 strains of Moraxella catarrhalis were isolated from the pharynx. The antimicrobial susceptibility of these isolates was assessed by a broth microdilution method. The isolation incidence of penicillin-intermediately resistant S. pneumoniae (PISP) and penicillin-highly resistant S. pneumoniae (PRSP) was 59.0% and 13.1%, respectively. Most strains of PISP and PRSP were highly resistant to cefaclor, cefpodoxime, cefteram, cefdinir, clarithromycin, ampicillin, and minocycline, but susceptibile to ofloxacin and cefditoren (CDTR). The in-vitro activity of CDTR was superior to that of other cephalosporins, such as cefaclor, cefdinir, and cefpodoxime, when tested against both the beta-lactamase-positive and -negative H. influenzae isolated. CDTR was also active against all the other strains, including methicillin-sensitive S. aureus, S. pyogenes, and M. catarrhalis. This study suggested that CDTR was a useful oral antibiotic for pediatric respiratory tract infections.

Host range of the ermF rRNA methylase gene in bacteria of human and animal origin

We screened 183 different clinical anaerobic and aerobic bacteria isolated from humans and other animals for the presence of the ermF gene using a polymerase chain reaction (PCR) assay. The ermF gene was detected in 107 (58%) clinical isolates, including 42 (61%) of 69 gram-positive bacteria and 65 (57%) of 114 gram-negative bacteria. Twenty-five ATCC isolates were also tested; 20 (80%) carried the ermF gene. The gene products from the ermF PCR from four isolates were sequenced and showed 95-99% nucleotide homology with the ermF gene and 98-99% amino acid homology with the gene product. Eleven (58%) of the 19 gram-negative donors tested were able to transfer the ermF gene. All nine (100%) of the gram-positive donors tested transferred the ermF gene, using either Enterococcus faecalis or Haemophilus influenzae as the recipients.

Highlights of the French Antimicrobial Resistance Surveillance Project. French Study Group

Thirty-three French laboratories took part in a study to determine the frequency of antibiotic resistance to S. pneumoniae, H. influenzae and M. catarrhalis in different regions of the country. A total of 1317 bacterial isolates were studied. The level of resistance to penicillin among isolates of S. pneumoniae was high particularly in children with otitis media or upper respiratory tract infections. In H. influenzae isolates the level of beta-lactamase production was over 30% in all groups of patients and specimen types and in M. catarrhalis the level of beta-lactamase production was in excess of 90%. Multidrug resistance was found often among the macrolides, tetracyclines, and trimethoprim/sulfamethoxazole, and these antimicrobials should not be regarded as therapeutic alternatives to the beta-lactams.

Results of the Alexander Project: a continuing, multicenter study of the antimicrobial susceptibility of community-acquired lower respiratory tract bacterial pathogens

In 1992, an ongoing, international multicenter study was established to investigate the antimicrobial susceptibility of community-acquired lower respiratory tract bacterial pathogens: the Alexander Project. Isolates cultured from patients living in geographically separated areas, ten in the European Union (EU) and five in the United States (US), were collected and tested using standard methods in a central laboratory. A total of 4,155 isolates of Haemophilus influenzae was collected during the period 1992-1994. beta-lactamase production was the principal mechanism of resistance observed with overall rates in the US (1992 = 26.3%; 1993 = 28.2%; and 1994 = 30.1%) generally twice those seen in the EU (1992 = 12.3%; 1993 = 14.4%; and 1994 = 15.5%). Chloramphenicol resistance was generally low except in Spanish centers where rates ranging from 4.0 to 15.9% were observed during the study period. One thousand one hundred ninety-three isolates of Moraxella catarrhalis were tested. beta-lactamase production was the only mechanism of resistance of any importance detected, with the vast majority of isolates producing the enzyme. Two thousand eight hundred twenty-nine isolates of Streptococcus pneumoniae were tested. French and Spanish centers provided isolates with the highest rates of either low-level (intermediate) or high-level penicillin resistance, which in 1994 ranged from 10.2 to 31.4% and 30.4 to 40.1% for each resistance category, respectively. With the exception of the fluoroquinolones, rates of resistance to other antimicrobials including the macrolides, doxycycline, chloramphenicol, and trimethoprim/sulfamethoxazole were high, generally, in centers with a high prevalence of penicillin resistance. However, in some centers (Toulouse, France and Genoa, Italy) this association was not complete for the macrolides.