Antimicrobial susceptibility of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella (Branhamella) catarrhalis isolated in the UK from sputa

Moraxella catarrhalis: A Cause of Concern with Emerging Resistance and Presence of BRO Beta-Lactamase Gene-Report from a Tertiary Care Hospital in South India

Background

Found as a commensal in the upper respiratory tract, Gram-negative diplococcus Moraxella catarrhalis did not hold much importance as an infectious agent for long. The emergence of the first antibiotic-resistant strain of M. catarrhalis was noted in 1977 in Sweden. This has gradually spread worldwide over the years to more than 95% of the strains showing resistance to penicillin now. Penicillin resistance is mediated by the production of beta-lactamases encoded by bro-1 and bro-2 genes that code for beta-lactamases BRO-1 and BRO-2, respectively. The purpose of this study was to explore the trends of antibiotic resistance, the presence of bro genes, and clinical correlation of these findings with the rise in M. catarrhalis was noted in 1977 in Sweden. This has gradually spread worldwide over the years to more than 95% of the strains showing resistance to penicillin now. Penicillin resistance is mediated by the production of beta-lactamases encoded by bro-1 and bro-2 genes that code for beta-lactamases BRO-1 and BRO-2, respectively. The purpose of this study was to explore the trends of antibiotic resistance, the presence of bro genes, and clinical correlation of these findings with the rise in

Methods

Strains of M. catarrhalis was noted in 1977 in Sweden. This has gradually spread worldwide over the years to more than 95% of the strains showing resistance to penicillin now. Penicillin resistance is mediated by the production of beta-lactamases encoded by bro-1 and bro-2 genes that code for beta-lactamases BRO-1 and BRO-2, respectively. The purpose of this study was to explore the trends of antibiotic resistance, the presence of bro genes, and clinical correlation of these findings with the rise in

Results

Fourteen strains of M. catarrhalis was noted in 1977 in Sweden. This has gradually spread worldwide over the years to more than 95% of the strains showing resistance to penicillin now. Penicillin resistance is mediated by the production of beta-lactamases encoded by bro-1 and bro-2 genes that code for beta-lactamases BRO-1 and BRO-2, respectively. The purpose of this study was to explore the trends of antibiotic resistance, the presence of bro genes, and clinical correlation of these findings with the rise in

Conclusion

The increase in antibiotic resistance and beta-lactamase production in M. catarrhalis is a cause of concern. The emerging resistance pattern emphasises the need for an appropriate antibiotic stewardship program in clinical practice. Importance should be given to the monitoring of the trends of antibiotic susceptibility and their usage to prevent the emergence of outbreaks with resistant strains and treatment failures.M. catarrhalis was noted in 1977 in Sweden. This has gradually spread worldwide over the years to more than 95% of the strains showing resistance to penicillin now. Penicillin resistance is mediated by the production of beta-lactamases encoded by bro-1 and bro-2 genes that code for beta-lactamases BRO-1 and BRO-2, respectively. The purpose of this study was to explore the trends of antibiotic resistance, the presence of bro genes, and clinical correlation of these findings with the rise in

A prediction model for COPD readmissions: catching up, catching our breath, and improving a national problem

Frequent COPD exacerbations have a large impact on morbidity, mortality and health-care expenditures. By 2020, the World Health Organization expects COPD and COPD exacerbations to be the third leading cause of death world-wide. Furthermore, In 2005 it was estimated that COPD exacerbations cost the U.S. health-care system 38 billion dollars. Studies attempting to determine factors related to COPD readmissions are still very limited. Moreover, few have used a organized machine-learning, sensitivity analysis approach, such as a Random Forest (RF) statistical model, to analyze this problem. This study utilized the RF machine learning algorithm to determine factors that predict risk for multiple COPD exacerbations in a single year. This was a retrospective study with a data set of 106 patients. These patients were divided randomly into training (80%) and validating (20%) data-sets, 100 times, using approximately sixty variables intially, which in prior studies had been found to be associated with patient readmission for COPD exacerbation. In an interactive manner, an RF model was created using the training set and validated on the testing dataset. Mean area-under-curve (AUC) statistics, sensitivity, specificity, and negative/positive predictive values (NPV, PPV) were calculated for the 100 runs. THE FOLLOWING VARIABLES WERE FOUND TO BE IMPORTANT PREDICTORS OF PATIENTS HAVING AT LEAST TWO COPD EXACERBATIONS WITHIN ONE YEAR: employment, body mass index, number of previous surgeries, administration of azithromycin/ceftriaxone/moxifloxacin, and admission albumin level. The mean AUC was 0.72, sensitivity of 0.75, specificity of 0.56, PPV of 0.7 and NPV of 0.63. Histograms were used to confirm consistent accuracy. The RF design has consistently demonstrated encouraging results. We expect to validate our results on new patient groups and improve accuracy by increasing our training dataset. We hope that identifying patients at risk for frequent readmissions will improve patient outcome and save valuable hospital resources.

Clinical characteristics of pneumonia caused by beta-lactamase negative ampicillin resistant Haemophilus influenzae (BLNAR)

We wished to assess the clinical differences between beta-lactamase-negative, ampicillin-sensitive and beta-lactamase-negative, ampicillin-resistant Haemophilus influenzae pneumonia. The medical records of 118 patients with H. influenzae pneumonia admitted between March 1998 and March 2003 to Nagasaki University Hospital and affiliated institutions were reviewed. In line with CLSI (Clinical and Laboratory Standards Institute) criteria, we classified H. influenzae according to sensitivity to ampicillin as follows: S (sensitive), minimum inhibitory concentration (MIC) =1; I (intermediate sensitivity), MIC =2; R (resistant), MIC =4. We defined the R strains as the BLNAR group and the S and I strains as the non-BLNAR group. We measured the patient's background, Pneumonia Severity Index (PSI), drug sensitivity of H. influenzae, and evaluation of antibiotic choices. There were no significant clinical differences between the beta-lactamase-negative, ampicillin-susceptible and the beta-lactamase-negative, ampicillin-resistant groups. However, BLNAR pneumonia was more prominent in the younger than the older patients. This study should provide useful information for understanding the clinical characteristics of BLNAR pneumonia.

Antimicrobial susceptibility of community-acquired respiratory tract pathogens in the UK during 2002/3 determined locally and centrally by BSAC methods

OBJECTIVES

To determine the antimicrobial susceptibility of Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae causing community-acquired lower respiratory tract infection in the UK during 2002/2003 and to compare susceptibilities determined locally by disc diffusion with agar dilution MICs determined at a central laboratory.

METHODS

H. influenzae, M. catarrhalis and S. pneumoniae were isolated in 30 laboratories and susceptibility determined locally by the BSAC standardized disc diffusion method. At a central laboratory, isolates were re-identified, tested for beta-lactamase production (H. influenzae and M. catarrhalis only) and MICs determined using the BSAC agar dilution method.

RESULTS

Five hundred and eighty-one H. influenzae, 269 M. catarrhalis and 519 S. pneumoniae were collected. Over 93% of M. catarrhalis and nearly 15% of H. influenzae were beta-lactamase positive rendering these sub-populations resistant to aminopenicillins. Overall, the antibacterial susceptibility rates for the isolates were high. However, macrolides showed poor activity against H. influenzae (0.86-1.38% susceptible by disc or MIC methods) and, compared with other antimicrobials, against S. pneumoniae (approximately 88% susceptible). Between 84% and 95% of H. influenzae, M. catarrhalis and S. pneumoniae were susceptible to cefuroxime but all isolates were susceptible to cefotaxime. Eighty-five percent of H. influenzae were susceptible to trimethoprim. The fluoroquinolones were very active against the isolates, with moxifloxacin showing lower MICs than levofloxacin against S. pneumoniae. Susceptibility determined locally by disc diffusion was in general agreement with that determined centrally by agar dilution MIC testing. However, there was one inconsistency with H. influenzae where disc diffusion indicated 22.9% and 46.8% resistance to clarithromycin and erythromycin, respectively but by MIC, only 0.9% and 6.9% were resistant, respectively.

CONCLUSIONS

Rates of resistance within community-acquired respiratory tract isolates were relatively low in the UK, in agreement with other studies. Moxifloxacin was the only antibacterial with over 99% isolates susceptible for each of the three pathogens investigated where breakpoints are available. The comparison between disc susceptibility testing and MIC determination using BSAC methods indicated generally good correlation but has highlighted a methodological problem with macrolides against H. influenzae in particular.

Chronic obstructive pulmonary disease: the clinical management of an acute exacerbation

Exacerbations of chronic obstructive pulmonary disease impose a considerable burden of morbidity, mortality, and health care cost. Management guidelines outlining best practice, based largely on consensus expert opinion, were produced by a number of organisations during the last decade. Current interest in the field is high. This has resulted in the publication of many further studies which have extended our understanding of the pathology involved and provided, for the first time, an evidence base for many of the therapeutic options. In this review we aim to bring the non-specialist reader up to date with current management principles and the evidence underlying such interventions.

In vitro activities of piperacillin against beta-lactamase-negative ampicillin-resistant Haemophilus influenzae

The in vitro activities of piperacillin (PIP) against beta-lactamase-negative ampicillin (AMP)-resistant (BLNAR) Haemophilus influenzae were compared with those of cefotaxime (CTX) and ceftriaxone (CRO), and the potency of PIP as therapy for meningitis caused by BLNAR is also discussed. PIP showed good activity (MIC at which 90% of strains are inhibited, 0.25 micro g/ml) against 69 BLNAR strains, and its activity was comparable to that of CRO and superior to that of CTX. No significant correlation was observed between the MICs of PIP and CTX or CRO or AMP, whereas a high correlation was observed between the MICs of CTX and CRO. In the killing study, PIP showed potent bactericidal activity compared with those of CTX and CRO. By microscopic examination, PIP caused the formation of a spindle and short filamentous cells with bulges and induced cell lysis in BLNAR strains, while treatment with CTX and CRO resulted in the formation of large, spherical cells without any obvious lysis. The affinity of Bocillin FL, a fluorescent penicillin used for determination of the 50% inhibitory concentration (IC(50)s) for penicillin-binding proteins (PBPs), to PBPs 3a and 3b of BLNAR strains was drastically decreased compared with that to an AMP-susceptible strain (ATCC 33391). In the case of the BLNAR strains, the IC(50)s for PBPs 1a, 1b, and 2 were similar to those for the PBPs of ATCC 33391. Since the affinity of binding to PBPs 3a and 3b of the BLNAR strains decreased drastically, the second targets among the PBPs were PBP 2 for PIP, PBP1 (1a and 1b) for CTX and CRO. In conclusion, PIP showed excellent activities against BLNAR strains in a manner different from those of cephem antibiotics, suggesting that it could be a candidate therapeutic agent for the treatment of meningitis caused by BLNAR strains.

Correlation between susceptibility and BRO type enzyme of Moraxella catarrhalis strains

Clinical isolates of Moraxella catarrhalis (76 isolates) were screened for beta-lactamase production and antibiotic susceptibility. beta-Lactamases (detected in 90.8% of isolates) were typed using isoelectric focusing to BRO-1 (87%) and BRO-2 (13%). Minor variations in electrofocusing patterns between the two types were seen. Isolates expressing BRO type enzymes showed solid resistance to penicillin, ampicillin and cephalothin, in particular BRO-1 producers. BRO-1 isolates were less susceptible to cephems and to beta-lactamase inhibitors than BRO-2 isolates. Isolates harbouring BRO-1 enzymes have more enzymatic activity than those expressed by BRO-2 isolates. Apart from resistance to tetracycline (14.5%), all isolates were consistently susceptible to erythromycin, chloramphenicol, ciprofloxacin and gentamicin. The conjugal transfer of BRO beta-lactamase gene(s) between M. catarrhalis isolates occurred with a frequency of 10(-5) to 10(-7)/donor cell. The data emphasize the importance of M. catarrhalis as an etiological agent spreading beta-lactamases that may inhibit some beta-lactams and lead to failure in treatment of mixed infections.

Antibiotics

This chapter discusses the bacterial pathogens that cause infective exacerbations, trials of antimicrobial therapy, individual antimicrobial agents, and guidelines for their use in the treatment of both asthma and chronic obstructive pulmonary disease (COPD). The relationship between respiratory tract infection, especially viral infection, and exacerbations of airway diseases is very well established. However, research is required to find new ways to distinguish between the colonization and infective exacerbations of COPD to gain a better understanding of the role of infection in the disease. With advances in molecular biology, the antigenic structures of bacteria and the evaluation of the antibody response to antigens can become the basis for identifying an acute exacerbation of COPD (AECB). Most clinical trials of antibiotics were performed for licensing, and patients with pathogens resistant to different antimicrobials were excluded. Future studies of new antimicrobials should examine clinical efficacy more stringently based on a classification system that would help select patients most likely to benefit from an antibiotic. These studies should also include well-defined prospective economic analyses and quality-of-life assessment to ascertain the cost utility of the antibiotic in question.

Epidemiological aspects of antibiotic resistance in respiratory pathogens

Respiratory infections are the most frequent reason for primary health care consultation. The main causes of respiratory tract infections in children are viruses and the most common types are upper respiratory tract infections: common cold, pharyngitis, otitis media and sinusitis. Pneumonia is much more serious. As well as viruses, bacteria are often involved in respiratory tract infections. Three bacterial species are most commonly isolated: Streptococcus pneumoniae, non-encapsulated Haemophilus influenzae and Moraxella (Branhamella) catarrhalis. The most common bacterial cause of pharyngitis is Streptococcus pyogenes. Bacteria isolated from community-acquired infection usually are sensitive to the majority of suitable drugs, but during the past two decades, significant antibiotic resistance has emerged. Resistance to penicillins has spread among H. influenzae and S. pneumoniae. The mechanism of penicillin resistance in H. influenzae is mainly by production of beta-lactamases TEM-1 and ROB-1, whereas in S. pneumoniae resistance is an effect of the changes in penicillin binding proteins. Among respiratory pathogens, resistance to tetracyclines, macrolides, trimethoprim-sulphamethoxazole and fluoroquinolones has also appeared. Several mechanisms depending on changes in target, active efflux and modifying enzymes are involved.

Worldwide prevalence of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the SENTRY Antimicrobial Surveillance Program, 1997-1999

The in vitro activities of numerous antimicrobials against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis from patients with bloodstream and respiratory tract infections in the United States, Canada, Europe, Latin America, and the Asia-Pacific region were studied in the SENTRY Antimicrobial Surveillance Program. Penicillin resistance (minimum inhibitory concentration, > or =2 microg/mL) was noted in all 5 geographic regions, and a high and increasing rate of macrolide resistance among S. pneumoniae isolates was observed. Elevated rates of resistance to clindamycin, trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline were seen. beta-Lactamase-mediated resistance in H. influenzae to amoxicillin and variable trimethoprim-sulfamethoxazole resistance by region were documented. Resistance to several drugs continues to emerge among pneumococci worldwide, but more stable resistance patterns have been noted for H. influenzae and M. catarrhalis. Continued surveillance of this pathogen group appears to be prudent.

beta-Lactamase activities and resistance to antibiotics of Haemophilus influenzae, H. parainfluenzae and H. aphrophilus strains identified in throat cultures from children

Haemophilus bacteria are normally present in the upper respiratory tract of healthy individuals. However, these bacteria could be opportunistic pathogens especially in children. The present study was conducted to determine beta-lactamase activity of Haemophilus from the throat cultures of children with upper respiratory tract infections. 154 Haemophilus strains were isolated from throat swabs of 208 children whom had upper respiratory tract infections. Among the 154 Haemophilus strains isolated, 117 H. influenzae (76%), 35 H. parainfluenzae (22.7%), and two H. aphrophilus (13%) were identified by API NH. beta-Lactamase activity was positive in 42 isolates of 117 H. influenzae isolates, while it was negative in 75 isolates. beta-Lactamase activity was positive in 20 H. parainfluenzae isolates, and negative in 15. All the H. aphrophilus isolates were beta-lactamase negative. It is known that beta-lactamase positive Haemophilus bacteria are resistant to some antibiotics. Therefore, the antibiotic resistance of Haemophilus was further investigated in relation to beta-lactamase activity. The in vitro antibacterial susceptibilities of Haemophilus strains for ampicillin, sulbactam-ampicillin, trimethoprim-sulfamethoxazole, gentamicin, chloramphenicol and ciprofloxacin were tested by disk diffusion method on chocolate agar. In 42 beta-lactamase-positive H. influenzae isolates, 32 isolates were resistant against ampicillin. In 20 beta-lactamase-positive H. parainfluenzae isolates, 16 were resistant against ampicillin. The two beta-lactamase negative H. aphrophilus were sensitive to ampicillin. Biotypes and serotypes were also investigated. Biotypes of H. influenzae strains were as follows: 40 strains biotype II, 25 strains biotype I, 14 strains biotype III, and 38 strains biotypes VII, VIII, V, and IV. Biotypes of 35 H. parainfluenzae strains were: 6 strains biotype III, 5 strains biotype I, 5 strains biotype IV. Biotypes of remaining 19 isolates were II, VIII, VI and VII. The serotypes of H. influenzae strains were determined by specific antiserums. Serotypes of 117 H. influenzae found were type a, b, c, d, and f.

Antibiotics are associated with lower relapse rates in outpatients with acute exacerbations of COPD

BACKGROUND

COPD is a complex disease with exacerbations characterized by worsening of symptoms resulting in deteriorating lung function.

STUDY OBJECTIVE

To assess predictive factors of relapse for patients with acute exacerbations of COPD (AECB).

DESIGN

Retrospective cohort analysis of visits for AECB.

SETTING

Veterans Affairs Medical Center.

PATIENTS

Three hundred sixty-two visits (173 patients) with documented COPD treated as outpatients for AECB.

MEASUREMENTS

Severity of underlying COPD, severity of AECB, comorbid conditions, therapy, and relapse rates (return visit within 14 days with persistent or worsening symptoms).

RESULTS

Each visit was analyzed individually (referred to as a patient-visit). One group received antibiotics (270 patient-visits), and the second group (92 patient-visits) did not. Both groups had similar demographics and severity of underlying COPD. The overall relapse rate was 22%. The majority of patient-visits (95%) with severe symptoms at presentation were prescribed antibiotics vs only 40% of those with mild symptoms. Twenty-nine of 92 patient-visits (32%) were followed by relapse in the group that was not given antibiotics, whereas only 50 of 270 (19%) treated with antibiotics relapsed (p < 0.001). Those treated with amoxicillin had an even higher relapse rate (20 of 37 patient-visits, or 54%) than those who did not receive antibiotics (p = 0.006).

CONCLUSIONS

Relapse from AECB was not related to the severity of underlying disease or to the severity of the acute exacerbation. Patients treated with antibiotics had significantly lower relapse rates than those who did not receive antibiotics. However, the specific choice of antibiotic is important because those treated with amoxicillin had the highest relapse rates of all groups.

Antimicrobial resistance patterns of Haemophilus influenzae isolated from patients with meningitis in São Paulo, Brazil

From 1989 to 1995, a total of 391 Haemophilus influenzae isolates were recovered from the cerebrospinal fluid (CSF) of hospitalized patients in São Paulo, Brazil. The majority of strains were isolated from infants aged less than 5 years. Strains belonging to biotype I (64.7%), biotype II (34.5%) and biotype IV (0.76%) were detected. Ninety-nine percent of these strains were serotype b. Minimal inhibitory concentration (MIC) was determined for ampicillin, chloramphenicol and ceftriaxone. The ss-lactamase assay was performed for all strains. The rate of ss-lactamase producer strains ranged from 10 to 21.4% during a period of 7 years, with an overall rate of 13.8%. Of the 391 strains analyzed, none was ss-lactamase negative ampicillin resistant (BLNAR). A total of 9.7% of strains showed resistance to both ampicillin and chloramphenicol; however, 4% of them were resistant to ampicillin only and 2% to chloramphenicol. All strains were susceptible to ceftriaxone and the MIC90 was 0.007 microg/ml, suggesting that ceftriaxone could be an option for the treatment of bacterial meningitis in pediatric patients who have not been screened for drug sensitivity.

Variation in the composition and pore function of major outer membrane pore protein P2 of Haemophilus influenzae from cystic fibrosis patients

We investigated the relationship between susceptibility to beta-lactam antibiotics and variation in the major outer membrane protein P2 (OmpP2; also called porin) of persistent nonencapsulated Haemophilus influenzae isolated from cystic fibrosis patients. Nine OmpP2 variants were selected from two distinct H. influenzae strains from two patients extensively treated with beta-lactam antibiotics. The variants differed in their susceptibilities to at least two beta-lactam antibiotics. By detergent extraction and column chromatography, OmpP2 was purified from two variants that were derived from strain 70 and that differed notably in their susceptibilities to beta-lactam antibiotics. The proteins were reconstituted into black lipid membranes for measurement of porin function. OmpP2 from the more resistant isolate (isolate 70b) had a smaller channel conductance than OmpP2 of the more susceptible isolate (isolate 70f). DNA sequencing of ompP2 of these isolates revealed single nonsynonymous base differences; there were changes in the amino acid sequence corresponding to surface-exposed loops 4, 5, 6, and 8. Changes in loops 4, 5, and 6 were previously shown to result in antigenic differences. Beside these mutations, variants of strain 70 showed additional mutations in loop 1 and nonexposed loop 3. Taken together, our results suggest that in variants of strain 70, nonsynonymous point mutations accumulated both in the sequences of ompP2 coding for antigen-variable loops and in other loops, notably, loops 1 and 3. The latter changes are suggested to affect the permeability of the porin channel.

Interaction of Streptococcus pneumoniae and Moraxella catarrhalis: investigation of the indirect pathogenic role of beta-lactamase-producing moraxellae by use of a continuous-culture biofilm system

The majority of clinical isolates of Moraxella catarrhalis produce beta-lactamase. The role of this enzyme in the phenomenon of indirect pathogenicity, in which a true pathogen such as Streptococcus pneumoniae is protected from the action of certain beta-lactam antibiotics, is well recognized. By using a simple continuous-culture biofilm system, it has been shown that the pneumococcus attains high titers in excess of 10(12) CFU/biofilm; furthermore, the penicillin-sensitive pneumococcus used remained susceptible to a range of beta-lactam antibiotics in these biofilms (R. K. Budhani and J. K. Struthers, J. Antimicrob. Chemother. 40:601-602, 1997). This system was used to characterize the antibiotic susceptibility of this isolate when grown with beta-lactamase-negative or -positive moraxellae. When grown with beta-lactamase-producing moraxellae in the presence of either benzylpenicillin or amoxicillin, the pneumococcus was protected in the range of the antibiotic concentrations to which it would be considered resistant. With amoxicillin-clavulanic acid the titers of the two organisms collapsed at the antibiotic concentration at which moraxellae became susceptible. The levels of beta-lactamase activity in cell-free supernatants of broth culture, in biofilm, and in biofilm effluent revealed distinct differences in this activity; levels in biofilm were significantly lower than those in broth culture supernatants. The system appears suitable for studying organisms under antibiotic stress and for investigating the interactions of bacteria under such conditions.

The Nearchus project: antibiotic susceptibility of respiratory pathogens and clinical outcome in lower respiratory tract infections at 27 centres in the UK

Community-acquired respiratory infections are usually treated empirically by the primary care physician. Increasing antibiotic resistance, for example, in pneumococci, prompted a UK survey of antibiotic susceptibility of three major lower respiratory tract pathogens, Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Each of 27 centres was asked to collect up to 100 isolates of the three species and submit them for confirmation of identity and for susceptibility testing to a central laboratory. In addition, general practitioners were asked for demographic details on the patient, their treatment and the clinical outcome. Of 1689 viable pathogens collected, there were 1078 (64%) strains of H. influenzae, 258 (15%) of M. catarrhalis and 353 (21%) of S. pneumoniae. Production of beta-lactamase was detected in 163 (15%) of 1078 isolates of H. influenzae and in 243 (94%) isolates of M. catarrhalis. For S. pneumoniae, moderate resistance to penicillin (MIC 0.12-1 mg/l) was found in 12 (3.4%) isolates and high level resistance (MIC > or = 2 mg/l) in 13 (3.7%) isolates. The most common individual treatments were amoxycillin, amoxycillin/clavulanate (amoxyclav) , and erythromycin. Complete or partial clinical resolution was achieved in 88% of 809 patients infected with H. influenzae, 83% of 197 infected with M. catarrhalis and 90% of 255 infected with S. pneumoniae.

Comparison of the efficacy and safety of a short course of ceftibuten with that of amoxycillin/clavulanate in the treatment of acute exacerbations of chronic bronchitis

The efficay and safety of short course ceftibuten (400 mg od for 5 days; n = 163) were compared with that of amoxycillin/clavulanate (AMX/CA) (250/125 mg tds for 10 days; n = 172) in a multicentre, single-blind, parallel-group trial in 335 adults with acute exacerbations of chronic bronchitis (AECB). Clinical response was equivalent, with cure or improvement in 134/145 (92.4%) ceftibuten-treated patients and 139/150 (92.7%) AMX/CA-treated patients (95% CI: -7.00%, +6.50%). The overall eradication rates were similar (ceftibuten 88.3%; AMX/CA 87.5%) and also the incidence of adverse events which occurred in 24/163 (14.7%) ceftibuten-treated and 27/172 (15.5%) AMX/CA-treated patients. Ceftibuten 400 mg od for 5 days is as effective and well tolerated as AMX/CA 250 mg tds for 10 days in the treatment of AECB.

Antimicrobial susceptibility of Haemophilus influenzae in the respiratory tracts of patients with cystic fibrosis

We analyzed the antimicrobial susceptibilities of Haemophilus influenzae isolates from 157 sputum specimens prospectively collected from 39 cystic fibrosis (CF) patients during a 2-year study. These isolates were characterized by random amplified polymorphic DNA analysis and major outer membrane protein (MOMP) analysis to identify H. influenzae strains and MOMP variants and to assess their persistence in the respiratory tract. Among the 247 H. influenzae isolates, 16 (6.5%) produced beta-lactamase. The 231 beta-lactamase-negative isolates represented 85 H. influenzae strains, 61 MOMP variants derived from 27 of these strains, and 85 persistent isolates identical to strains or MOMP variants. All beta-lactamase-negative isolates were tested for susceptibility to ampicillin, amoxicillin-clavulanic acid, cefuroxime, cefotaxime, cefaclor, imipenem, tetracycline, and trimethoprim-sulfamethoxazole by disk diffusion testing. Eleven (13%) H. influenzae strains, 18 (30%) MOMP variants, and 30 (35%) persistent isolates were resistant to one or more of the antibiotics tested. Antimicrobial susceptibility was decreased among MOMP variants and persistent isolates compared to nonpersistent H. influenzae strains, and changes in susceptibility occurred irrespective of MOMP variation. We conclude that the decreased antimicrobial susceptibility of H. influenzae during persistence contributes to the poor eradication of H. influenzae from the respiratory tracts of CF patients.

Treatment of experimental pneumonia due to penicillin-resistant Streptococcus pneumoniae in immunocompetent rats

A model of pneumonia due to Streptococcus pneumoniae resistant to penicillin was developed in immunocompetent Wistar rats and was used to evaluate the efficacies of different doses of penicillin, cefotaxime, cefpirome, and vancomycin. Adult Wistar rats were challenged by intratracheal inoculation with 3 x 10(9) CFU of one strain of S. pneumoniae resistant to penicillin (MICs of penicillin, cefotaxime, cefpirome, and vancomycin, 2, 1, 0.5, and 0.5 microg/ml, respectively) suspended in brain heart broth supplemented with 0.7% agar. The rats experienced a fatal pneumonia, dying within 5 days and with peak mortality (70 to 80%) occurring 48 to 72 h after infection, and the bacterial counts in the lungs persisted from 8.87 +/- 0.3 log10 CFU/g of lung at 24 h of the infection to 9.1 +/- 0.3 log10 CFU/g at 72 h. Four hours after infection the animals were randomized into the following treatment groups: (i) control without treatment, (ii) penicillin G at 100,000 IU/kg of body weight every 2 h, (iii) penicillin G at 250,000 IU/kg every 2 h, (iv) cefotaxime at 100 mg/kg every 2 h, (v) cefpirome at 200 mg/kg every 2 h, and (vi) vancomycin at 50 mg/kg every 8 h. Two different protocols were used for the therapeutic efficacy studies: four doses of beta-lactams and one dose of vancomycin or eight doses of beta-lactams and two doses of vancomycin. Results of the therapy for experimental pneumonia caused by penicillin-resistant S. pneumoniae showed that initially, all the antimicrobial agents tested had similar efficacies, but when we prolonged the treatment, higher doses of penicillin, cefotaxime, and cefpirome were more effective than penicillin at lower doses in decreasing the residual bacterial titers in the lungs. Also, when we extended the treatment, vancomycin was more efficacious than penicillin at lower doses but was less efficacious than higher doses of penicillin or cefpirome. The model that we have developed is simple and amenable for inducing pneumonia in immunocompetent rats and could be used to explore the pathophysiology and to evaluate optimal therapy of this infection in the immunocompetent host.

Antibiotic susceptibilities of Haemophilus influenzae in central Scotland

OBJECTIVE: To ascertain the incidence of antibiotic resistance in Haemophilus influenzae in central Scotland and the beta-lactamases produced by these isolates. METHODS: A total of 213 H. influenzae isolates from four medical centers in Scotland [Aberdeen (n=58), Edinburgh (n=55), Glasgow (n=64) and Dundee (n=36)] were tested for susceptibility to a range of antimicrobials including beta-lactams, beta-lactam/beta-lactamase-inhibitor combinations, and a representative 4-quinolone, antifolate and macrolide. Susceptibility testing of the beta-lactam/beta-lactamase-inhibitor combination amoxicillin plus clavulanic acid was conducted at both 2:1 and 4:1 ratios and with clavulanic acid fixed at a concentration of 2 mg/L. Each strain was further investigated for the presence of beta-lactamase activity. RESULTS: Although the incidence of resistance to amoxicillin was 15%, in the presence of clavulanic acid, this resistance was reduced to 4.2%, 5.6% and 4.2% with the 2:1 ratio, 4:1 ratio and 2 mg/L fixed concentration, respectively. Sixteen percent of the isolates demonstrated immediate beta-lactamase production. Isoelectric focusing showed that 77.4%, 16.1% and 6.5% of the beta-lactamase-positive strains were found to contain TEM-1, VAT-1 and both TEM-1 and VAT-1 beta-lactamases, respectively. A further 29% of the strains were recognized as being beta-lactamase-positive after prolonged incubation with nitrocephin. CONCLUSIONS: This study suggests that current testing for beta-lactamases may underestimate the prevalence of beta-lactamase production in H. influenzae.

Trends in antimicrobial susceptibility of bacterial pathogens of the respiratory tract

Rates of antimicrobial resistance have been increasing in bacteria responsible for community-acquired lower respiratory tract infections in the United States. Nearly 100% of clinical isolates of Moraxella catarrhalis now produce beta-lactamase, an enzyme that renders this pathogen resistant to such agents as penicillin, ampicillin, and amoxicillin. However, this organism remains nearly uniformly susceptible to alternative oral antimicrobials, such as cephalosporins, macrolides, tetracyclines, beta-lactamase inhibitor combinations, and the combination of trimethoprim/sulfamethoxazole. The susceptibility of M. catarrhalis to these agents is not expected to change markedly in the next few years. A linear increase in the prevalence of beta-lactamase-mediated ampicillin resistance has been evident among isolates of nontypeable Haemophilus influenzae during the past decade in the United States. By the year 2000, 45-50% of isolates are likely to produce beta-lactamase. Although the susceptibility of this organism to alternative oral antimicrobials varies, rates of resistance to cefuroxime axetil, cefpodoxime, cefixime, azithromycin, and perhaps clarithromycin remain < 1%. The rate of penicillin resistance among isolates of Streptococcus pneumoniae, which has increased steadily in recent years, currently stands at approximately 25% in the United States and will likely reach 40-50% during the next 5-10 years. Because of cross-resistance, in general all beta-lactam antimicrobials have reduced activity against penicillin-resistant strains of S. pneumoniae. A 1994-1995 survey found that 3.4% of S. pneumoniae isolates were highly resistant to cefotaxime, and 4-8% were resistant to chloramphenicol, tetracycline, and the macrolides. Resistance to these antimicrobials has usually followed the emergence of penicillin resistance in other countries. Therefore, S. pneumoniae resistance to these drugs is expected to increase markedly during the next few years in the United States.

Antibiotic resistance among respiratory pathogens in preschool children

OBJECTIVE

To determine the prevalence of antibiotic resistance among common respiratory pathogens circulating in the community.

DESIGN

Survey of common respiratory pathogens isolated from nasal discharges.

SETTING

117 childcare centres and kindergartens in metropolitan Melbourne between May and July 1991-1993 and 42 from sociodemographically matching suburbs in Sydney between May and July, 1993.

SUBJECTS

Children aged six years and under with nasal discharge.

OUTCOME MEASURES

Resistance to penicillins, erythromycin and tetracycline among isolates of Haemophilus influenzae, Streptococcus pneumoniae, Moraxella (Branhamella) catarrhalis and Staphylococcus aureus.

RESULTS

A total of 2286 nasal discharge swabs were collected. Amoxycillin resistance was detected in 99 of 711 isolates of H. influenzae (13.9%) and penicillin resistance in 781 of 834 isolates of M. catarrhalis (93.6%), 342 of 375 isolates of S. aureus (91.2%), and 30 of 781 isolates of S. pneumoniae (3.9%). Of 86 strains of H. influenzae type b isolated, 20 (23.3%) produced beta-lactamase. Penicillin resistance tended to become more common among isolates of H. influenzae and S. pneumoniae during the three-year period.

CONCLUSION

Antibiotic resistance, mediated by beta-lactamase or altered penicillin-binding proteins, among respiratory pathogens carried by preschool children was significant and possibly increasing. This highlights the impact of prescribed antibiotics in the community and the folly of prescribing the limited store of antibiotics for viral infections.

Antimicrobial agents for community-acquired respiratory tract infections

Chemotherapy of community-acquired respiratory tract infections was reviewed from a microbiological perspective. The current worldwide spread of penicillin-resistant Streptococcus pneumoniae and of ampicillin-resistant Haemophilus influenzae has required a reassessment of the antimicrobial agents being used for empiric therapy. In vitro data with different orally administered antibiotics were reviewed in order to identify any deficiencies in their spectra of activity against four common respiratory tract pathogens. Cefixime, cefuroxime axetil, cefprozil, amoxicillin-clavulanic acid and trimethoprim-sulfamethoxazole were active against all four species other than penicillin-resistant pneumococci.

In vitro activities of 12 orally administered antimicrobial agents against four species of bacterial respiratory pathogens from U.S. Medical Centers in 1992 and 1993

Clinical isolates of Haemophilus influenzae, Streptococcus pneumoniae, Streptococcus pyogenes, and Moraxella catarrhalis were gathered from 19 different clinical laboratories throughout the continental United States. The in vitro activities of 12 orally administered antimicrobial agents were compared by broth microdilution tests with 3,151 bacterial isolates. Among 890 H. influenzae isolates, 30% were capable of producing beta-lactamase enzymes (12 to 41% in different medical centers). Most of the 619 beta-lactamase-negative H. influenzae strains were susceptible to ampicillicin (MIC, < or = 1.0 micrograms/ml): 5 strains were intermediate in susceptibility (MIC, 2.0 micrograms/ml) and 1 strain was ampilicillin resistant (MIC, 4.0 micrograms/ml). Ninety-two percent of 698 M. catarrhalis strains were beta-lactamase positive. Of 799 S. pneumoniae isolates, 15% were intermediate in susceptibility to penicillin and 7% were resistant to penicillin. The prevalence of penicillin-susceptible pneumococci in different institutions ranged from 63 to 95%. Only 1% of 764 S. pyogenes isolates were resistant to the macrolides, but 5% of S. pneumoniae isolates were macrolide resistant. Only 71% of 58 penicillin-resistant S. pneumoniae isolates were erythromycin susceptible, whereas 97% of the 622 penicillin-susceptible strains were erythromycin susceptible. Penicillin-resistant pneumococci were also relatively resistant to the cephalosporins and amoxicillin. Penicillin-susceptible pneumococci were susceptible to amoxicillin-clavulanic acid (MIC for 90% of isolates tested [MIC90], < or = 0.12/0.06 microgram/ml), cefixime (MIC90, 0.25 microgram/ml), cefuroxime axetil (MIC90, < or = 0.5 microgram/ml), cefprozil (MIC90, < or = 0.5 micrograms/ml), cefaclor (MIC90, 0.5 microgram/ml), and loracarbef (MIC90, 1.0 microgram/ml). Most strains of the other species remained susceptible to the study drugs other than amoxicillin.

Moraxella catarrhalis in upper respiratory tract of healthy Yemeni children/adults and paediatric patients: detection and significance

A highly variable carriage rate of Moraxella catarrhalis has been reported in the literature. In order to assess the reasons for this variability, detection rates of this organism from various sites of the upper respiratory tract of children and adults were studied. Throat swabs, oral swabs and nasal swabs from 131 children, 96 adults and 64 paediatric patients with upper respiratory tract infections were cultured on a selective medium. Detection rates of 31.4% in children less than three years of age, 38.5% in children between 4 and 12 years, 11.7% in adults and 21.9% in patients were found, respectively. The reasons for high variability in the carriage rates were many including the number and site of specimen collection, media used for isolation and identification criteria. All isolates were sensitive to amoxycillin-clavulanic acid and co-trimoxazole. A significantly higher share of M. catarrhalis isolates from patients were beta-lactamase producers (12/14, 85.7%) as compared to normal healthy subjects (41.9%), suggesting a cautious approach in the use of beta-lactam antibiotic in respiratory tract infections.

High rate of erythromycin and clarithromycin resistance among Streptococcus pneumoniae isolates from blood cultures from Providence, R.I

Four (5%) of 81 recent isolates of Streptococcus pneumoniae from the blood of adult patients but no isolates from pediatric patients (n = 51) were resistant (MIC, > or = 1 microgram/ml) to erythromycin. The MICs of clarithromycin were slightly lower than those of erythromycin, but there was complete cross-resistance. Routine testing and surveillance are needed to determine whether erythromycin resistance among S. pneumoniae isolates is increasing throughout the United States.

Susceptibility of Haemophilus influenzae to piperacillin-tazobactam combinations: interpretive criteria and quality control limits for standardized tests

In vitro studies evaluated methods for testing the susceptibility of Haemophilus influenzae to piperacillin-tazobactam combinations. Ampicillin-resistant beta-lactamase-nonproducing strains of H. influenzae may be presumed to be relatively resistant to combinations of piperacillin-tazobactam, even though they frequently appear to be susceptible by disk diffusion methods. Other ampicillin-resistant or -susceptible strains were predictably susceptible; i.e., 130 such strains gave zones of inhibition > or = 26 mm in diameter, and MICs for these strains were < or = 0.125/4.0 micrograms/ml (< or = 1.0/0.12 micrograms/ml when an 8:1 ratio was tested). A resistant category has yet to be defined. For quality control purposes, H. influenzae ATCC 49247 should give zones of inhibition 32 to 38 mm in diameter, and broth microdilution MICs should be 0.12/4.0 to 0.5/4.0 micrograms/ml.

Susceptibilities of beta-lactamase-producing and -nonproducing ampicillin-resistant strains of Haemophilus influenzae to ceftibuten, cefaclor, cefuroxime, cefixime, cefotaxime, and amoxicillin-clavulanic acid

In in vitro studies we evaluated the susceptibilities of beta-lactamase-producing and -nonproducing, ampicillin-resistant strains of Haemophilus influenzae and compared them with those of ampicillin-susceptible strains. Ampicillin, amoxicillin-clavulanic acid, ceftibuten, cefaclor, cefuroxime, cefixime, and cefotaxime were evaluated by broth microdilution tests and disk diffusion tests. The disk diffusion tests accurately categorized beta-lactamase-producing strains and ampicillin-susceptible strains as being susceptible to the study drugs other than ampicillin. Ampicillin-resistant, beta-lactamase-nonproducing strains were relatively resistant to all seven study drugs, but the disk diffusion test did not always predict that resistance. The clinical relevance of the decreased susceptibility to various agents remains unclear, but to be conservative, all ampicillin-resistant, beta-lactamase-nonproducing strains might be assumed to be resistant to other beta-lactams. After excluding that small group of isolates, reliable susceptibility test results were obtained with lots of Haemophilus Test Medium that met quality assurance criteria.

In vitro susceptibility of Haemophilus influenzae to cefaclor, cefixime, cefetamet and loracarbef

The susceptibility of 2,212 Haemophilus influenzae isolates cultured in UK clinical laboratories in 1991 was determined for four orally-administered beta-lactam drugs. These isolates included 1,893 ampicillin-susceptible, 191 beta-lactamase-positive and 128 ampicillin-resistant, beta-lactamase-negative Haemophilus influenzae. While 150 (6.8%) isolates were resistant to cefaclor (MIC > or = 16 mg/l) and 85 (3.8%) to loracarbef, all were inhibited by < or = 2 mg/l cefetamet and < or = 1 mg/l cefixime and were therefore susceptible to these agents. Ranges and modes of inhibition zone diameters and MICs indicated that the susceptibility of a variable proportion of the 191 beta-lactamase-positive isolates to cefaclor, loracarbef and cefetamet was reduced compared with the fully susceptible population. In contrast, a major reduction in susceptibility to all four antimicrobial agents was seen among the 128 ampicillin-resistant (MIC 1-64 mg/l) beta-lactamase-negative isolates such that these accounted for 53% and 67% of the total number of organisms resistant to cefaclor and loracarbef respectively. In addition, 23 of 25 isolates inhibited only by > or = 1 mg/l cefetamet and all eight inhibited only by > or = 0.5 mg/l cefixime showed this type of resistance to ampicillin. Results indicate the importance of detecting non-beta-lactamase-mediated resistance to ampicillin and any concomitant diminished susceptibility to other beta-lactam drugs.