Mutant prevention concentrations of ABT-492, levofloxacin, moxifloxacin, and gatifloxacin against three common respiratory pathogens

The purpose of this study was to compare the mutant prevention concentration (MPC) of ABT-492 to those of levofloxacin, moxifloxacin, and gatifloxacin against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The fluoroquinolones had comparable mutation selection windows, which is the ratio of MPC/MIC, for all isolates.

Pharmacodynamics of an 800-mg dose of telithromycin in patients with community-acquired pneumonia caused by extracellular pathogens

The pharmacodynamics of telithromycin, a new ketolide antibacterial, was examined in 115 patients with community-acquired pneumonia (CAP). Patients received telithromycin 800 mg qd for 7-10 days. Pharmacokinetic parameters were determined, and exposure was linked to microbiological outcome using logistic regression analysis. A breakpoint for increased probability of microbiological eradication was developed and was found to be the ratio of area under the concentration-time curve (AUC) to minimum inhibitory concentration (MIC) of 3.375. The final logistic regression model of microbiological outcome included body weight and AUC/MIC ratio breakpoint. This model was found in analyses of the entire population and when Streptococcus pneumoniae and Haemophilus influenzae were examined separately. The AUC/MIC ratio target attainment rate is expected to be >99.9% for S. pneumoniae and Moraxella catarrhalis and 93.1% for H. influenzae. This study demonstrated a relationship between telithromycin drug exposure and microbiological outcome. Telithromycin is expected to achieve the drug exposure breakpoint for the majority of isolates causing CAP.

In vitro investigation of the indirect pathogenicity of beta-lactamase-producing microorganisms in the nasopharyngeal microflora

OBJECTIVE

Nasopharyngeal microflora contains some beta-lactamase-producing microorganisms. In this study, we investigated in vitro on the indirect pathogenicities of Haemophilus parainfluenzae (H. parainfluenzae) and Moraxella catarrhalis (M. catarrhalis) against the antipneumococcul activities of some beta-lactams.

METHODS

We compared the antimicrobial and bactericidal activities of beta-lactams against penicillin-susceptible Streptococcus pneumoniae (PSSP) with or without presence of the enzymes of two species of beta-lactamase-producing microorganisms, H. parainfluenzae and M. catarrhalis.

RESULTS

When adding the enzymes extracted from these two beta-lactamase-producing microorganisms in equivalent amounts of 10(7) CFU/spot, the minimum inhibitory concentrations of amoxicillin (AMPC) and cefaclor (CCL) increased to >64 microg/mL. Even third-generation cephalosporins, such as cefditren (CDTR) and ceftriaxone (CTRX) showed marked increases with the enzyme of M. catarrhalis. In time-kill kinetics, same phenomenon was observed in mixed culture indicating the indirect pathogenicities of distinct bacteria, not extracted enzymes, on the cidal activities of beta-lactams against PSSP. Clavulanic acid (CVA)/AMPC, faropenem (FRPM), and imipenem (IPM) were not affected by these beta-lactamase-producing strains with respect to their activities against PSSP. However, these two beta-lactamase-producing strains and their enzymes did not show any significant influence on the antipneumococcul activities of beta-lactams, until the number of bacterial cells reached >10(8) CFU/mL.

CONCLUSION

Our results suggest that these two species of beta-lactamase-producing microorganisms in the nasopharyngeal microflora may act as indirect pathogens on the antipneumococcul activities of beta-lactams with reflecting their substrate profiles, but this is dependent on sufficient amounts of enzyme for their influence as indirect pathogens.

In vitro activities of novel 2-fluoro-naphthyridine-containing ketolides

In vitro activities of erythromycin A, telithromycin, and two investigational ketolides, JNJ-17155437 and JNJ-17155528, were evaluated against clinical bacterial strains, including selected common respiratory tract pathogens. Against 46 macrolide-susceptible and -resistant Streptococcus pneumoniae strains, the MIC(90) (MIC at which 90% of the isolates tested were inhibited) of the investigational ketolides was 0.25 microg/ml, twofold lower than that of telithromycin and at least 64-fold lower than that of erythromycin A. Against erm(B)-containing pneumococci, the MIC(90) of all the ketolides was 0.06 microg/ml. The MIC(90) of the investigational ketolides against mef(A)-containing pneumococci or pneumococci with both mef(A) and erm(B) was 0.25 microg/ml, two-and fourfold lower, respectively, than that of telithromycin. In contrast, the MICs of the investigational ketolides against macrolide-resistant S. pneumoniae strains with ribosomal mutations were similar to or, in some cases, as much as eightfold higher than those of telithromycin. Against Haemophilus influenzae, MICs of all the ketolides were < or =2 microg/ml. Against three Moraxella catarrhalis isolates, the MIC of the ketolides was 0.25 microg/ml. The ketolides inhibited in vitro protein synthesis, with 50% inhibitory concentrations ranging from 0.23 to 0.27 microM. In time-kill studies against macrolide-susceptible and erm- or mef-containing pneumococci, the ketolides were bacteriostatic to slowly bactericidal, with 24-h log(10) decreases ranging from 2.0 to 4.1 CFU. Intervals of postantibiotic effects for the ketolides against macrolide-susceptible and -resistant S. pneumoniae were 3.0 to 8.1 h.

Efficacy and safety of pharmacokinetically enhanced amoxicillin-clavulanate at 2,000/125 milligrams twice daily for 5 days versus amoxicillin-clavulanate at 875/125 milligrams twice daily for 7 days in the treatment of acute exacerbations of chronic bronchitis

This randomized, controlled trial was designed to show that a short, 5-day course of pharmacokinetically enhanced amoxicillin-clavulanate at 2,000/125 mg (Augmentin XR) is as effective clinically as a longer, 7-day course of conventional amoxicillin-clavulanate at 875/125 mg (both given twice daily) in the treatment of acute exacerbations of chronic bronchitis (AECB). Amoxicillin-clavulanate at 2,000/125 mg was designed to extend the therapeutic levels of amoxicillin in serum over the 12-h dosing interval, compared with conventional formulations, to eradicate bacterial strains for which amoxicillin MICs were < or =4 microg/ml while retaining efficacy against beta-lactamase-producing pathogens. A total of 893 patients were randomized and received study medication (amoxicillin-clavulanate at 2,000/125 mg for 443 patients and 875/125 mg for 450 patients). Overall, 141 patients receiving amoxicillin-clavulanate at 2,000/125 mg and 135 receiving the comparator formulation had at least one pathogen identified at screening. Amoxicillin-clavulanate at 2,000/125 mg was as effective clinically in the per-protocol (PP) population at the test of cure (days 14 to 21, primary efficacy endpoint) as amoxicillin-clavulanate at 875/125 mg (clinical success rates of 93.0 and 91.2%, respectively; treatment difference, 1.8; 95% confidence interval [CI], -2.2, 5.7). Bacteriological success in the bacteriology PP population was high for both formulations (amoxicillin-clavulanate at 2,000/125 mg, 76.7%; amoxicillin-clavulanate at 875/125 mg, 73.0%; treatment difference, 3.8; 95% CI, -7.5, 15.0). Both therapies were well tolerated, with a similar incidence of adverse events. Fewer than 5% of patients in each group withdrew from the study due to adverse events. The shorter, 5-day course of amoxicillin-clavulanate at 2,000/125 mg was shown to be as effective clinically as a longer, 7-day course of amoxicillin-clavulanate at 875/125 mg, with high bacteriological efficacy and no difference in tolerability.

Pharmacokinetic-pharmacodynamic modelling of antibacterial activity of cefpodoxime and cefixime in in vitro kinetic models

The bacterial time-kill curves of cefpodoxime and cefixime against four bacterial strains (Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae/penicillin sensitive and S. pneumoniae/penicillin intermediate) were compared in in vitro infection models in which various human pharmacokinetic profiles of unbound antibiotic were simulated. This approach offers more detailed information than the minimum inhibitory concentration (MIC) does about the time course of antibacterial efficacy of an antibiotic. A pharmacokinetic-pharmacodynamic (PK-PD) model based on unbound antibiotic concentrations at the site of infection, and a sigmoid Emax-relationship with EC50 as the antibiotic concentration necessary to produce 50% of the maximum effect, effectively described the antimicrobial efficacy of both cefpodoxime and cefixime. The EC50 values of cefpodoxime and cefixime were consistent with their respective MIC values. Both antibiotics had similar high potency against H. influenzae (EC50: 0.04 mg/L) and M. catarrhalis (EC50: 0.12 mg/L), while the potency of cefpodoxime against S. pneumoniae strains was about 10-fold higher than that of cefixime (EC50s/sensitive strain: 0.02 mg/L versus 0.27 mg/L; EC50s/intermediate strain: 0.09 mg/L versus 0.69 mg/L). Applications of this model and unbound tissue PK profiles obtained from a previous clinical study performed in our group, showed that cefpodoxime has higher bacteriological potency than cefixime against S. pneumoniae. Simulations based on this model allow the comparison of antibacterial efficacy of different antibiotics and dosing regimens.

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.

Antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and group A β-haemolytic streptococci in 2002–2003

A multinational surveillance study, GRASP, was conducted between November 2002 and April 2003 with the aim of assessing rates of antimicrobial resistance among 2656 isolates of Streptococcus pneumoniae, 2486 isolates of group A beta-haemolytic streptococci, 1358 isolates of Haemophilus influenzae and 1047 of Moraxella catarrhalis from 20 countries in Europe, eastern Asia and southern Africa. Conspicuous differences between various countries were noted in the S. pneumoniae resistance rates observed for penicillin (0-79.2%) and erythromycin (4-66%), along with other antimicrobials. The percentage of MDR strains was above 25% in 8 of the 20 countries studied. Group A streptococcal macrolide resistance rates ranged from 0% to 35% by country, while rates of beta-lactamase production ranged from 0% to 39% for H. influenzae and 80-100% for M. catarrhalis. Antibiotic resistance in S. pneumoniae remains a significant problem world wide.

Hepatoprotective and antibacterial effects of extracts from Trichilia emetica Vahl. (Meliaceae)

Trichilia emetica Vahl. (Meliaceae) is a tree widely distributed in Tropical Africa. It has been used in Mali folk medicine for the treatment of various illnesses. The aim of this work was to study the hepatoprotective and antibacterial effects of a crude aqueous extract from Trichilia emetica root. An ethyl ether fraction from the aqueous extract was also prepared and studied. We have examined the hepatoprotective activity of the extracts on CCl4-induced damage in rat hepatocytes, their toxicity using the brine shrimp bioassay and their antibacterial activity against clinical isolated bacterial strains, which are commonly responsible for respiratory infections. A preliminary phytochemical analysis showed a high polyphenolic content in the aqueous extract and the presence of limonoids in the ethyl ether fraction. These latter compounds may be considered responsible for the good activity against the bacterial strains tested. Trichilia emetica extracts exerted also a significant (P<0.05) hepatoprotective effect at a dose of 1000 microg/ml both on plasma membrane and mitochondrial function as compared to silymarin used as a positive control. These activities may be a result of the presence of either polyphenols or limonoids. Finally, both the aqueous extract and its ethyl ether fraction did not show toxicity (LC50>1000 microg/ml) in the brine shrimp bioassay.

Antimicrobial resistance in the nasopharyngeal flora of children with acute otitis media and otitis media recurring after amoxicillin therapy

The objective of this study was to investigate the antimicrobial susceptibility of the organisms isolated from the nasopharynx of children who presented with acute otitis media (AOM) or otitis media that recurred after amoxicillin therapy. Nasopharyngeal cultures obtained from 72 patients, 40 with AOM and 32 with recurrent otitis media (ROM), were analysed. Thirty-six potentially pathogenic organisms were recovered in 34 (85 %) of the children from the AOM group, and 42 were isolated from 29 (91 %) of the children from the ROM group. The organisms isolated were Streptococcus pneumoniae (n = 26), Haemophilus influenzae non-type b (n = 22), Moraxella catarrhalis (n = 13), Streptococcus pyogenes (n = 8) and Staphylococcus aureus (n = 9). Resistance to the eight antimicrobial agents used was found in 37 instances in the AOM group as compared to 99 instances in the ROM group (P < 0.005). The difference between AOM and ROM was significant with Streptococcus pneumoniae resistance to amoxicillin (P < 0.005), to amoxicillin/clavulanate (P < 0.005), to trimethoprim/sulfamethoxazole (P < 0.01), to cefixime (P < 0.01) and to azithromycin (P < 0.01), and for H. influenzae resistance to amoxicillin (P < 0.025). These data illustrate the higher recovery rate of antimicrobial-resistant Streptococcus pneumoniae and H. influenzae from the nasopharynx of children who had otitis media that recurred after amoxicillin therapy than those with AOM.

Antimicrobial activities of tosufloxacin against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella branhamella catarrhalis isolated from otolaryngological infectious diseases

In 2003, the Japan Society for Infectious Diseases in Otolaryngology conducted its third nationwide survey of clinical isolates from otolaryngological infectious diseases. We selected three primary causative organisms of otolaryngological infectious diseases, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella Branhamella catarrhalis, and evaluated their sensitivities to tosufloxacin (TFLX), a new oral quinolone, because the survey revealed a rise in drug-resistant strains, suggesting potential problems with the antibiotics commonly used against these organisms. The minimum inhibitory concentration (MIC)(90) values of TFLX against S. pneumoniae, H. influenzae, and M. catarrhalis were 0.25 microg/ml, <or=0.06 microg/ml, and <or=0.06 microg/ml respectively, and TFLX was shown to be as effective as or superior to other new quinolones. In addition, TFLX showed sufficient antimicrobial effects against frequently detected drug-resistant bacteria such as penicillin-resistant S. pneumoniae (PRSP) and beta-lactamase-negative, ampicillin-resistant strains of H. influenzae (BLNAR). Furthermore, only a few strains of bacteria showed resistance to TFLX.

PROTEKT 1999–2000: a multicentre study of the antimicrobial susceptibility of respiratory tract pathogens in Japan

DESIGN

A six-centre study in Japan during the winter of 1999-2000 assessed the in vitro activity of >20 antimicrobial agents against the common respiratory pathogens Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis. The minimum inhibitory concentrations (MIC) of each antimicrobial was determined against these isolates using National Committee for Clinical Laboratory Standards (NCCLS) methodology.

RESULTS

Among S. pneumoniae isolates, 44.5% were penicillin resistant. The macrolide resistance rate was 77.9% with 90.5% of penicillin-resistant strains also being macrolide resistant. Resistance mechanisms in macrolide-resistant isolates were identified as mef(A) or erm(B) in 42.5% and 52.5%, respectively. Of the fluoroquinolone-resistant isolates (1.3%), most were also penicillin and macrolide resistant. All strains were inhibited by telithromycin at <or=1mg/L. Among S. pyogenes isolates, erythromycin resistance was 17.5% overall but showed considerable variation among the six centres. For H. influenzae, 8.5% produced beta-lactamase and a single beta-lactamase-negative, ampicillin-resistant isolate (0.36%) was obtained, and there was no fluoroquinolone resistance. All isolates were susceptible to telithromycin. Most antimicrobials showed good activity against M. catarrhalis, although 96.7% were beta-lactamase positive.

CONCLUSION

The prevalence of antimicrobial resistance to macrolides, penicillin and the fluoroquinolones among the common respiratory pathogens is high in Japan.

In vitro activity of quinolones against S. pneumoniae, H. influenzae and M. catarrhalis in Saudi Arabia

Susceptibility of 88 clinical Streptococcus pneumoniae isolates, 116 Haemophilus influenzae isolates and 80 Moraxella catarrhalis isolates to 6 fluoroquinolones--ciprofloxacin, ofloxacin, levofloxacin, trovafloxacin, grepafloxacin and gemifloxacin--were determined. Isolates were from patients with invasive disease at 4 hospitals in Saudi Arabia between 1996 and 1998. S. pneumoniae isolates were fully susceptible to trovafloxacin, grepafloxacin and gemifloxacin; susceptibility to ofloxacin and levofloxacin was 97.7% and 98.9% respectively. H. influenzae isolates were susceptible to all agents, except for trovafloxacin (99.1%). M. catarrhalis strains were fully sensitive to all agents except ofloxacin (97.5%). No isolates were resistant to gemifloxacin or grepafloxacin.

Characteristics of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolated from the nasopharynges of asymptomatic children and molecular analysis of S. pneumoniae and H. influenzae strain replacement in the nasopharynx

Nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in 226 children in different settings (in a crèche [day care center], in an orphanage, and at home) during two seasons (winter and spring) was studied. The rates of carriage of S. pneumoniae and H. influenzae were markedly higher in the crèche and in the orphanage than in the home setting (e.g., 56.5, 63.3, and 25.9%, respectively, for S. pneumoniae in winter). Approximately 80% of the S. pneumoniae isolates identified in the crèche and in the orphanage belonged to the serotypes represented in the seven-valent pneumococcal vaccine, and 4.4% of the children were colonized by H. influenzae type b. Almost all H. influenzae isolates were fully susceptible to the antimicrobial agents tested, and only five (3.6%) produced beta-lactamase; in contrast, 100% of the M. catarrhalis isolates were beta-lactamase positive. Among S. pneumoniae isolates, 36.2% were nonsusceptible to penicillin (PNSP) and 11.8% were fully resistant to penicillin (PRP). All PNSP isolates were obtained from children at the crèche and at the orphanage but not among children brought up at home, and all PRP isolates showed a multiresistant phenotype. Colonization by PRP isolates correlated well with prior treatment with beta-lactams. For the majority of children colonized at both sampling times, strain replacement of S. pneumoniae and H. influenzae was observed; long-term colonization by a single strain was rare.

In vitro activity of ertapenem against selected respiratory pathogens

OBJECTIVES

The in vitro activity of ertapenem was evaluated in comparison to 21 selected agents against a large collection of recently isolated respiratory tract pathogens including: 180 Streptococcus pneumoniae, 100 Streptococcus pyogenes, 70 Haemophilus influenzae, 70 Moraxella catarrhalis, 100 methicillin-susceptible Staphylococcus aureus and 30 Klebsiella pneumoniae. Additional in vitro tests (time-kill curves with ertapenem alone and in combination with four other agents) for S. pneumoniae were carried out.

METHODS

MIC determinations and time-kill curves were carried out following the procedures suggested by the NCCLS.

RESULTS

According to NCCLS susceptibility breakpoints, ertapenem was comparable to the most potent compounds tested for all pathogens studied. Ertapenem was 100% active against penicillin-susceptible and -intermediate S. pneumoniae and against 60% of penicillin-resistant strains. Time-kill tests at 4x MIC confirmed a pronounced bactericidal potency of ertapenem against these organisms. Interactions of ertapenem with several other agents against pneumococci resulted in clear synergic interactions (98.4%). Indifference was extremely rare and antagonism was not observed. All S. pyogenes strains tested were inhibited by ertapenem, irrespective of their macrolide resistance phenotypes. Ertapenem was also fully active against H. influenzae (100% susceptible) and M. catarrhalis (MIC90 0.015-0.03 mg/L) even when capable of synthesizing beta-lactamases. Methicillin-susceptible S. aureus and K. pneumoniae, including extended-spectrum beta-lactamase-producing strains, were 100% susceptible to ertapenem.

CONCLUSIONS

Our results indicate that ertapenem has a suitable spectrum of activity against organisms encountered in community-acquired bacterial respiratory tract infections.

High prevalence of antibiotic resistance in isolates from the middle meatus of children and adults with acute rhinosinusitis

BACKGROUND

The pathogens in acute rhinosinusitis are similar worldwide. An increase in antibiotic resistance has been shown in a large number of studies in recent years. The prevalence of resistance varies greatly in different countries. This study was performed to determine the endemic prevalence of antibiotic resistance in pathogens of acute rhinosinusitis in Taiwan.

METHODS

Middle meatus discharge was taken for aerobic culture in 133 outpatients with the diagnosis of acute rhinosinusitis.

RESULTS

One hundred two isolates of pathogens were found, including three major bacteria: Haemophilus influenzae (37.3%), Streptococcus pneumoniae (28.4%), and Moraxella catarrhalis (11.8%). Polymicrobial infections and positive cultures occurred more frequently in pediatric patients, as did recovery of M. catarrhalis infection. An extremely high percentage of resistance to first-line antibiotics was noted, viz., penicillin-nonsusceptible S. pneumoniae (PNSSP) (72.4%), ampicillin-resistant H. influenzae (60.5%), and M. catarrhalis (58.3%).

CONCLUSION

The high prevalence of drug resistance is a great threat to public health. Antibiotic use should be more prudent, especially in pediatric patients, who were found to be more susceptible to bacterial rhinosinusitis and multiple pathogenic infection.

Comparative in vitro activity of a pharmacokinetically enhanced oral formulation of amoxicillin/clavulanic acid (2000/125 mg twice daily) against 9172 respiratory isolates collected worldwide in 2000

OBJECTIVES

A new, pharmacokinetically enhanced, oral formulation of amoxicillin/clavulanic acid has been developed to overcome resistance in the major bacterial respiratory pathogen Streptococcus pneumoniae, while maintaining excellent activity against Haemophilus influenzae and Moraxella catarrhalis, including beta-lactamase producing strains. This study was conducted to provide in vitro susceptibility data for amoxicillin/clavulanic acid and 16 comparator agents against the key respiratory tract pathogens.

METHODS

Susceptibility testing was performed on 9172 isolates collected from 95 centers in North America, Europe, Australia, and Hong Kong by broth microdilution MIC determination, according to NCCLS methods, using amoxicillin/clavulanic acid and 16 comparator antimicrobial agents. Results were interpreted according to NCCLS breakpoints and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints based on oral dosing regimens.

RESULTS

Overall, 93.5% of Streptococcus pneumoniae isolates were susceptible to amoxicillin/clavulanic acid at the current susceptible breakpoint of < or =2 microg/mL and 97.3% at the PK/PD susceptible breakpoint of < or =4 microg/mL for the extended release formulation. Proportions of isolates that were penicillin intermediate and resistant were 13% and 16.5%, respectively, while 25% were macrolide resistant and 21.8% trimethoprim/sulfamethoxazole resistant. 21.9% of Haemophilus influenzae were beta-lactamase producers and 16.8% trimethoprim/sulfamethoxazole resistant, >99% of isolates were susceptible to amoxicillin/clavulanic acid, cefixime, ciprofloxacin and levofloxacin at NCCLS breakpoints. The most active agents against Moraxella catarrhalis were amoxicillin/clavulanic acid, macrolides, cefixime, fluoroquinolones, and doxycycline. Overall, 13% of Streptococcus pyogenes were resistant to macrolides.

CONCLUSION

The extended release formulation of amoxicillin/clavulanic acid has potential for empiric use against many respiratory tract infections worldwide due to its activity against species resistant to many agents currently in use.

Evaluation of restriction endonuclease analysis of BRO beta-lactamases in clinical and carrier isolates of Moraxella catarrhalis

A rapid increase in the prevalance of beta-lactamase producing M. catarrhalis isolates has highlighted its pathogenic potential. In this study, we aimed to detect the BRO beta-lactamases of our clinical (n = 32) and carrier (n =32) strains of Moraxella catarrhalis and compare the relationship of the enzyme type in assesment of MIC results of the antibiotics tested. BRO beta-lactamases were differentiated by restriction endonuclease analysis. Antibiotic susceptibility was performed by the agar dilution method recommended by NCCLS (M7A5). The clinical isolates produced 96.9%, whereas the carrier strains produced 90.6% beta-lactamase positivity by the restriction enzyme analysis. BRO-1 was isolated as 90.6% (n =29) while the BRO-2 and non-beta-lactamase producers (NBLP) were isolated as 6.3% (n =2) and 3.1% (n =1) respectively among clinical isolates. The rate of BRO-1 in the carrier strains was 75.0% (n =24), BRO-2 was 15.6% (n =5) and NBLP was 9.4%, (n =3). The beta-lactamase production with nitrocefin test was 96.9% (31/32) in clinical isolates and 90.6% (29/32) in carrier strains. M. catarrhalis needs a continous monitoring of antibiotic susceptibility; in this era restriction endonuclease analysis could be useful to screen BRO beta-lactamase genes.

[Molecular characterization of BRO beta-lactamases of Moraxella catarrhalis strains isolated from carrier children]

Nasopharyngeal carriage of Moraxella catarrhalis is a risk factor for upper respiratory tract infections and otitis media. In this study, we aimed to characterize BRO beta-lactamases of M. catarrhalis strains isolated from 64 children without any symptoms of respiratory disease. Gram negative diplococci grown on selective media and which are catalase, oxidase, DNase, nitrate reduction positive, glucose, maltose, sucrose and lactose fermentation negative, were diagnosed as M. catarrhalis. Antibiotic susceptibility testing was performed by agar dilution method recommended by NCCLS. BRO beta-lactamases were differentiated by restriction enzyme analysis method. The resistance rate for ampicillin was 18.8% and all the isolates were found to be sensitive to amoxicillin-clavulanate, cefazolin, cefaclor, azithromycin and ciprofloxacin. Out of 64 M. catarrhalis isolates, 57 (89%) were found beta-lactamase positive with nitrocefin disk test (Remel, USA). The presence of BRO beta-lactamases in these 57 strains (89%) was also confirmed by restriction enzyme analysis, while 7 (11%) of them were found to be negative. Among the positive strains, 47 (73.4%) were typed as BRO-1, and 10 (15.6%) were typed as BRO-2. The characterization of BRO beta-lactamases of M. catarrhalis strains in carrier children is important since the high rate of carriage predisposes to respiratory tract infections. As a result, BRO beta-lactamase typing will guide the treatment regimen against the respiratory infections that can occur due to M. catarrhalis in carrier children.

Multicenter surveillance of antimicrobial resistance of Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis to 14 oral antibiotics

BACKGROUND AND PURPOSE

Data on the in vitro activities of orally administered cephalosporins, particularly third-generation cephalosporins, against recent pathogens responsible for community-respiratory tract infection are lacking.

METHODS

A susceptibility surveillance of 267 isolates of Streptococcus pneumoniae, 205 of Streptococcus pyogenes, 204 of Haemophilus influenzae, and 147 of Moraxella catarrhalis to 14 oral antimicrobial agents using the agar dilution method was carried out from March 2002 to October 2002 in Taiwan.

RESULTS

High rates of non-susceptibility to penicillin (60%), cefaclor (67%), cefuroxime (62%), cefpodoxime (64%), clarithromycin (91%), and trimethoprim-sulfamethoxazole (98%) for S. pneumoniae isolates and high rates of non-susceptibility to ampicillin (70%), clarithromycin (34%), and trimethoprim-sulfamethoxazole (63%) for H. influenzae isolates were found. The rank order of oral cephalosporin activity based on the minimum concentrations at which 90% of the isolates were inhibited (MIC90s) for S. pneumoniae was cefpodoxime > cefuroxime > cefixime > cefaclor, cephradine > cephalexin and for H. influenzae and M. catarrhalis was cefixime > cefpodoxime > cefuroxime > cefaclor > cephalexin, cephradine. Among the 75 S. pneumoniae isolates resistant to penicillin (MICs ranged 2 to 4 mg/L), 4% were intermediate to amoxicillin and > 90% were resistant to cefaclor, cefuroxime, and cefpodoxime. For S. pyogenes isolates, all were susceptible to penicillin, 21% were not susceptible to clarithromycin and 4% were not susceptible to clindamycin. Thirty four percent of H. influenzae isolates were not susceptible to clarithromycin. The MIC90 of clarithromycin against M. catarrhalis isolates was 0.5 mg/L.

CONCLUSIONS

Cefpodoxime, cefixime, and cefuroxime are promising agents against these bacterial pathogens, except for penicillin-non-susceptible S. pneumoniae isolates.

Antibiotic susceptibility of acute otitis media pathogens in otitis-prone Belgian children

A regional surveillance study was carried out in children with recurrent acute otitis media (AOM) to determine the antimicrobial susceptibility of three common AOM pathogens. Susceptibility to relevant antimicrobial agents was determined on 149 Streptococcus pneumoniae, 246 Haemophilus influenzae and 119 Moraxella catarrhalis strains isolated between January 1999 and January 2002, either from the nasopharynx or middle ear of 74 children with recurrent AOM, the majority (77%) being otitis-prone. Overall pneumococcal resistance to penicillin was 9.4% (6.7% penicillin-intermediate resistant, 2.7% penicillin-resistant), whereas cotrimoxazole and erythromycin resistance accounted for 25.5% and 38.9% respectively. The prevalence of antimicrobial-non-susceptible S. pneumoniae was the highest in middle ear isolates (P<0.05) and in otitis-prone children (P<0.01). Moreover, otitis-prone children harboured significantly more pneumococci resistant to at least two antimicrobial agents (24.3% versus 7.4%; P<0.01). No patient age related variation was observed. Five serogroups (6, 19, 23, 14 and 9) covered by the 7-valent pneumococcal conjugate vaccine, constituted most of the antibiotic resistant pneumococci. Among nasopharyngeal and middle ear H. influenzae isolates, 17.1% were resistant to ampicillin and 16.3% to cotrimoxazole. For M. catarrhalis, 92.4% of all isolates was ampicillin-resistant.

CONCLUSION

This study confirms international and national differences in antimicrobial susceptibility profiles of three acute otitis media pathogens with relatively favourable antibiotic resistance rates in Belgian children with frequent acute otitis media. This "at risk" population of otitis-prone children is shown to harbour more antimicrobial resistant and multidrug resistant pneumococci. If antimicrobial therapy in this group of children is indicated, high dose amoxicillin is recommended whereas the use of macrolides is obsolete.

Clinical and bacteriological efficacy and safety of 5 and 7 day regimens of telithromycin once daily compared with a 10 day regimen of clarithromycin twice daily in patients with mild to moderate community-acquired pneumonia

OBJECTIVES

This study was conducted to investigate the potential equivalence in clinical efficacy and assess safety of a 5 or 7 day regimen of oral telithromycin (800 mg once daily) and a 10 day regimen of oral clarithromycin (500 mg twice daily) in treating community-acquired pneumonia (CAP). Bacteriological efficacy was also compared.

METHODS

This was a multicentre, randomized, double-blind, active-controlled study. Patients with mild to moderate CAP received telithromycin 800 mg once a day for 5 (n=193) or 7 (n=195) days or clarithromycin 500 mg twice a day for 10 days (n=187). In these groups, 159, 161 and 146 patients, respectively, completed the study.

RESULTS

At the post-therapy/test-of-cure evaluation, clinical cure rates (per-protocol clinical population) were 89.3% (5 days) and 88.8% (7 days) for telithromycin, and 91.8% for clarithromycin 10 days. Satisfactory bacteriological outcome rates (per-protocol bacteriological population) were 87.7% and 80.0% for 5 and 7 days of telithromycin, respectively, and 83.3% for 10 days of clarithromycin. Bacteriological eradication rates in the respective treatment groups were, for Streptococcus pneumoniae, 95.8% (23/24), 96.7% (29/30) and 88.5% (23/26); for Haemophilus influenzae, 88.0% (22/25), 84.0% (21/25) and 88.2% (15/17) and for Moraxella catarrhalis, 1/1, 4/5 and 3/4. Both telithromycin regimens demonstrated clinical efficacy against pneumococcal bacteraemia (19/19), atypical pathogens (9/9) and erythromycin-resistant S. pneumoniae isolates (5/5). Most treatment-emergent adverse events were mild to moderate in intensity with most commonly reported adverse events involving the gastrointestinal system.

CONCLUSIONS

Telithromycin 800 mg administered once a day for 5 or 7 days was as effective and safe as clarithromycin 500 mg administered twice a day for 10 days in treating patients with CAP caused by common respiratory pathogens, including macrolide-resistant isolates, and pneumococcal bacteraemia.

Susceptibility of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis to 17 oral antimicrobial agents based on pharmacodynamic parameters: 1998-2001 U S Surveillance Study

Pharmacokinetic/pharmacodynamic parameters were used to interpret susceptibility data for the oral agents tested in a clinically meaningful way. Among S pneumoniae isolates, >99% were susceptible to respiratory fluoroquinolones, 91.6% to amoxicillin, 92.1% to amoxicillin/clavulanic acid (95.2% at the extended-release formulation breakpoint), 90.6% to clindamycin, 80.4% to doxycycline, 71.0% to azithromycin, 72.3% to clarithromycin, 71.8% to cefprozil and cefdinir, 72.6% to cefuroxime axetil, 66.3% to cexime, 63.7% to trimethoprim/sulfamethoxazole, and 19.7% to cefaclor. Among H influenzae isolates, 28.6% were b-lactamase positive, but virtually all were susceptible to amoxicillin/clavulanic acid (98.3%, with 99.8% at the extended-release formulation breakpoint), cexime (100%), and uoroquinolones (99.8%), whereas 93.5% were susceptible to cefdinir, 82.8% to cefuroxime axetil, 78.1% to trimethoprim/sulfamethoxazole, 70.2% to amoxicillin, 25.1% to doxycycline, 23.2% to cefprozil, and 5% to cefaclor, azithromycin and clarithromycin. Most isolates of M catarrhalis were resistant to amoxicillin, cefaclor, cefprozil, and trimethoprim/sulfamethoxazole. Thus significant b-lactam and macrolide/azalide resistance in Streptococcus pneumoniae and b-lactamase production and trimethoprim/sulfamethoxazole resistance in untypeable Haemophilus influenzae are still present. The results of this study should therefore be applied to clinical practice based on the clinical presentation of the patient, the probability of the patient's having a bacterial rather than a viral infection, the natural history of the disease, the potential of pathogens to be susceptible to various oral antimicrobial agents, the potential for cross-resistance between agents with S pneumoniae, and the potential for pathogens to develop further resistance. Antibiotics should be used judiciously to maintain remaining activity and chosen carefully based on activity determined by pharmacokinetic/pharmacodynamic-based breakpoints to avoid these bacteria developing further resistance, particularly to fluoroquinolones.