Benchmarking the in vitro activity of moxifloxacin against recent isolates of Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae. A European multi-centre study

To benchmark the activity of moxifloxacin, a European study comprising 900 Streptococcus pneumoniae, 1051 Haemophilus influenzae, and 226 Moraxella catarrhalis referred from 30 institutions during 1998 is described. For S. pneumoniae, moxifloxacin and trovafloxacin MIC(90) and modal MICs values were 0.12 microg/ml and independent of susceptibility to other drug classes, geography, or site of infection. MIC(90)/modal MICs were, respectively, 0.25/0.12 microg/ml for grepafloxacin, 0.25/0.25 microg/ml for sparfloxacin, and 1.0/0.5 microg/ml for levofloxacin. The moxifloxacin C(max):MIC ratio of 20.8-26.3 is higher than comparator fluoroquinolones. Five isolates were intermediate or resistant to grepafloxacin, sparfloxacin, or levofloxacin of which four and three remained susceptible to trovafloxacin and moxifloxacin, respectively. For moxifloxacin, > 90% of S. pneumoniae isolates demonstrated MICs > or =3 dilutions below the susceptibility breakpoint used. Modal MICs and MIC(90) for M. catarrhalis (both 0.03 microg/ml) and H. influenzae (0.03 microg/ml and 0.06 microg/ml) were independent of beta-lactamase production. These data demonstrate the in vitro activity of moxifloxacin and establish a baseline for future surveillance studies that will be important for detecting and tracking any trends in changing activity of this fluoroquinolone.

Comparative in vitro potency of gemifloxacin against European respiratory tract pathogens isolated in the Alexander Project

European isolates collected in 1998 for the Alexander Project were tested for their susceptibility to ciprofloxacin, ofloxacin and a novel fluoroquinolone, gemifloxacin, which has a spectrum of activity including common and atypical respiratory pathogens. MIC90s of gemifloxacin for Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis were 0.03, 0.06 and 0.015 mg/L, respectively. On the basis of MIC90s, gemifloxacin was the most potent antimicrobial tested against S. pneumoniae and M. catarrhalis. Against H. influenzae, gemifloxacin was one tube dilution more potent than ofloxacin and one tube dilution less potent than ciprofloxacin. As resistance to currently available antimicrobial agents increases, gemifloxacin offers potential as a promising new agent for the treatment of respiratory tract infection.

Hydroxamic acid derivatives as potent peptide deformylase inhibitors and antibacterial agents

Low-molecular-weight beta-sulfonyl- and beta-sulfinylhydroxamic acid derivatives have been synthesized and found to be potent inhibitors of Escherichia coli peptide deformylase (PDF). Most of the compounds synthesized and tested displayed antibacterial activities that cover several pathogens found in respiratory tract infections, including Chlamydia pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The potential of these compounds as antibacterial agents is discussed with respect to selectivity, intracellular concentrations in bacteria, and potential for resistance development.

Stimulation of bacterial adherence by neutrophil defensins varies among bacterial species but not among host cell types

Adherence of Haemophilus influenzae to bronchial epithelial cells is enhanced by neutrophil defensins, which are released from activated neutrophils during inflammation [Gorter et al. (1998) J. Infect. Dis. 178, 1067-1078]. In this study, we showed that the adherence of H. influenzae to various epithelial, fibroblast-like and endothelial cell types was significantly enhanced by defensins (20 microg ml(-1)). Defensins stimulated also the adherence of Moraxella catarrhalis, Neisseria meningitidis and nonencapsulated Streptococcus pneumoniae to the NCI-H292 cell line. In contrast, defensins did not affect the adherence of Pseudomonas aeruginosa, encapsulated S. pneumoniae, Escherichia coli and Staphylococcus epidermidis. These results suggest that the defensin-enhanced adherence might support the adherence and possibly persistence of the selected bacterial species using the respiratory tract as port of entry.

Antimicrobial activity of advanced-spectrum fluoroquinolones tested against more than 2000 contemporary bacterial isolates of species causing community-acquired respiratory tract infections in the United States (1999)

In vitro activity of four newer fluoroquinolones (clinafloxacin, gemifloxacin, moxifloxacin, sitafloxacin) and an equal number control drugs in the same class (ciprofloxacin, grepafloxacin, levofloxacin, trovafloxacin) was determined by reference dilution tests against 2156 recent United States clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. All the fluoroquinolones demonstrated excellent in vitro activity against these pathogens. Streptococcus pneumoniae isolates were fully susceptible to clinafloxacin, sitafloxacin, and gemifloxacin at 0.5 microg/ml, and over 98% of sampled strains had MICs of </=1 microg/ml for grepafloxacin, moxifloxacin and trovafloxacin. Penicillin resistance did not influence the potency of the tested fluoroquinolones. All the isolates of H. influenzae and M. catarrhalis were inhibited by the investigational, as well as comparator fluoroquinolones at </=0.5 microg/ml, irrespective of their beta-lactamase producing abilities. In conclusion, the investigational fluoroquinolones demonstrated excellent activity against these major respiratory tract pathogens isolated in 1999, and some remain safe candidates for empiric therapy of community-acquired respiratory tract infections and selected infections in hospitalized patients.

Antimicrobial activity and in vitro susceptibility test development for cefditoren against Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus species

Cefditoren, a third generation orally administered aminothiazolyl cephalosporin, has demonstrated bactericidal activity against many Gram positive and negative bacterial pathogens and stability against clinically important beta-lactamases. Cefditoren was compared to cefaclor, cefixime, and penicillins against 1 435 recently isolated strains of streptococci (312 Streptococcus pneumoniae, 165 viridans group streptococci, 142 beta-haemolytic streptococci), Haemophilus influenzae (521 strains), and Moraxella catarrhalis (295 strains). Streptococcus pneumoniae and viridans group streptococci had penicillin nonsusceptible rates of 37.8 and 35.8%, respectively. Cefditoren (MIC(90) in microg/ml/% susceptible) activity against all tested H. influenzae (0.03/100) and M. catarrhalis (0.06-0.5/100) was comparable to cefixime and significantly greater than cefaclor. Cefditoren (MIC(90), 0.5 microg/ml) was 4- to 128-fold more active than comparison beta-lactams against the pneumoococci and was the most potent beta-lactam (including penicillin) versus beta-haemolytic streptococci. Cefditoren pharmacokinetics demonstrate a T(1/2) of 1.5-2 h and C(max) values of 2.8 and 4.6 microg/ml, respectively with 200 or 400 mg doses of cefditoren pivoxil; plasma concentrations exceed 1 microg/ml for 4 to 6 hours (33-50% of dosing interval). Consequently, a susceptible MIC of </= 1 microg/ml or </= 2 microg/ml was proposed with zone diameter correlates of >/= 18 and >/= 15 mm (5-microg disk) for all cited fastidious species tested. Categorical agreement between MIC and disk tests was 94.6 to 100% with a correlation coefficient (r) range of 0.50 to 0.90 for streptococci. H. influenzae intermethod comparison results using the same interpretive criteria were in complete agreement, but exhibited a low r = 0.39. Cefditoren clearly possesses the most potent activity among currently studied oral cephalosporins or penicillin against commonly isolated bacterial pathogens causing bronchitis, pneumonia, sinusitis, or pharyngitis and was active against nearly all penicillin-resistant streptococci at </= 0.5 microg/ml. Expanded clinical investigations seem warranted.

In vitro activity of quinupristin/dalfopristin against gram-positive bacteria Haemophilus influenzae and Branhamella catarrhalis in Taiwan

BACKGROUND

Over the past decade, resistance of Gram-positive cocci to common antibiotics has steadily increased. New antibacterial agents that are active against multidrug-resistant pathogens are urgently needed for the treatment of these pathogens. We conducted an in vitro study on the activity of quinupristin/dalfopristin and other antibiotics against common clinical isolates of the gram-positive cocci, Haemophilus influenzae and Branhamella catarrhalis.

METHODS

The agar dilution method described by the National Committee for Clinical Laboratory Standards was used to determine the minimum inhibitory concentrations (MICs) of bacterial isolates from clinical specimens obtained from patients in a medical center.

RESULTS

All Staphylococcus aureus isolates were inhibited by quinupristin/dalfopristin (< or = 2 micrograms/ml). The MIC90s were 1 mg/ml for both methicillin-sensitive and -resistant S aureus. Quinupristin/dalfopristin inhibited streptococci at a concentration of 1 microgram/ml or less. The MIC90s were 1 microgram/ml for Streptococcus pneumoniae, S pyogenes and viridans streptococci. Ampicillin-resistant Enterococcus faecium was inhibited by quinupristin/dalfopristin at 0.5 to 4 micrograms/ml, with an MIC90 of 1 microgram/ml. H influenzae was inhibited by quinupristin/dalfopristin at 0.25 to 8 micrograms/ml, with an MIC90 of 4 micrograms/ml. B catarrhalis was inhibited by quinupristin/dalfopristin at 0.25 to 1 microgram/ml, with an MIC90 of 1 microgram/ml.

CONCLUSIONS

We found that quinupristin/dalfopristin showed good in vitro activity against staphylococci, streptococci and B catarrhalis but less in vitro activity against H influenzae.

A pharmacodynamic model to support a 12-hour dosing interval for amoxicillin/sulbactam, a novel oral combination, in the treatment of community-acquired lower respiratory tract infections

We evaluated, by time-kill studies, the pharmacodynamics of amoxicillin/sulbactam (AMX/SUL, 875 mg/125 mg), a novel oral combination, against the major respiratory pathogens in 12 volunteers receiving a single dose. The sera corresponding to 50% of a 12-h dosing interval displayed either bactericidal or inhibitory activity against both a penicillin-susceptible and a penicillin-intermediate Streptococcus pneumoniae strain (penicillin MIC of 0.03 and 0.25 microg/ml, respectively), as well as against a beta-lactamase-positive Moraxella catarrhalis and a beta-lactamase-negative Haemophilus influenzae strain. Both the peak samples and those corresponding to 4 h after dose (i.e. 33% of a 12-h dosing interval) proved active against both a penicillin-resistant S. pneumoniae (MIC, 2 microg/ml) and a beta-lactamase-positive H. influenzae strain. The AMX-SUL formulation evaluated in this study showed pharmacodynamic features that support clinical trials to assess its efficacy in the treatment of lower respiratory tract infections with a 12-h dosing interval regimen.

Interrelationship between the pharmacokinetics and pharmacodynamics of cefaclor advanced formulation in patients with acute exacerbation of chronic bronchitis

Cefaclor advanced formulation (cefaclor AF) is an extended-release form of the oral cephalosporin cefaclor. When cefaclor AF 750 mg twice-daily and cefaclor immediate release 500 mg three-times-a-day are compared there is a skew to the right of the pharmacokinetic profile and higher levels are achieved. Based on this pharmacokinetic finding, we examined the relationship between the bacterial susceptibility to cefaclor (MIC), the achieved cefaclor AF serum and sputum concentrations, and in vivo eradication of the bacteria in 36 patients with acute exacerbations of chronic bronchitis. The mean peak concentrations in serum and sputum 5 h after administration were 8.6 microg/ml (95% CI: 8.1 microg/ml - 9.1 microg/ml) and 1.5 microg/ml (95% CI: 1.4 microg/ml - 1.7 microg/ml), respectively. Cefaclor was always detectable 8 h after administration. At post therapy, treatment was successful in 31 (86.1%) patients. Cefaclor concentrations in serum persisted above the MIC for more than 40% of dosing interval in 31 subjects, and those in sputum in 24 patients. Treatment was successful in all subjects with percent of time above the MIC in serum of >40%, whereas the time that levels in sputum stayed above the MIC was not the pharmacodynamic parameter that correlated best with therapeutic efficacy for cefaclor. Our data demonstrate that when cefaclor AF is dosed twice-daily, the in vivo pharmacodynamic susceptibility breakpoint is 8 microg/ml. The good activity and pharmacokinetics of cefaclor AF provide serum concentrations higher than the MIC of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis for more than 40% of the validated dosing interval. Therefore, it might be considered for first choice treatment of acute exacerbations of chronic bronchitis.

Resistant bacteria in the adenoids: a preliminary report

OBJECTIVE

To determine the incidence of resistant bacteria in adenoid cultures from children with and without middle ear disease and rhinosinusitis symptoms.

DESIGN

Children meeting the requirement for tympanostomy tube placement underwent an adjuvant adenoidectomy for symptoms of adenoid hypertrophy or recurrent rhinosinusitis. Adenoid tissue and coexisting middle ear fluid, if present, were cultured.

SETTING

Tertiary referral children's hospital with community-based satellite clinics.

PATIENTS

Forty-six patients ranging in age from 1 to 11 years (68% <3 years) with recurrent or persistent otitis media and symptoms of adenoid hypertrophy or rhinosinusitis (study patients) underwent tympanostomy tube placement and adenoidectomy with culture of the adenoids and middle ear effusions. Eighteen patients with adenoid hypertrophy without ear disease or rhinosinusitis were used as controls.

INTERVENTIONS

Tympanostomy tube placement and adenoidectomy.

MAIN OUTCOME MEASURES

Presence or absence of resistant bacteria.

RESULTS

Resistant bacteria were found in cultures of the adenoids in 56% (26/46) of the study group compared with 22% (4/18) of the control patients (P<.02). Also, strains of Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis were found in cultures from 78% (36/ 46) of the study group, compared with 44% (8/18) of those from the control group (P<.01). Resistant isolates were found in 65% (23/35) of the S. pneumoniae, 37% (18/49) of the H. influenzae, and 100% (19/19) of the M. catarrhalis cultures from the adenoids or middle ear spaces.

CONCLUSION

Resistant bacteria are present in significant amounts in the adenoids of children with middle ear disease and rhinosinusitis symptoms compared with patients without those diseases or symptoms.

Multicenter surveillance of antimicrobial resistance of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in Taiwan during the 1998-1999 respiratory season

A susceptibility surveillance study of 276 isolates of Streptococcus pneumoniae, 301 of Haemophilus influenzae, and 110 of Moraxella catarrhalis was carried out from November 1998 to May 1999 in Taiwan. High rates of nonsusceptibility to penicillin (76%), extended-spectrum cephalosporins (56%), azithromycin (94%), clarithromycin (95%), and trimethoprim-sulfamethoxazole (TMP-SMX) (65%) for S. pneumoniae isolates and high rates of nonsusceptibility to amoxicillin (58%) and TMP-SMX (52%) for H. influenzae isolates were found. Higher percentages of S. pneumoniae isolates nonsusceptible to aminopenicillins, extended-spectrum cephalosporins, macrolides, and TMP-SMX were observed among penicillin-intermediate and -resistant isolates. All quinolones tested were active in vitro against these three organisms.

Antibiotic resistance in respiratory tract isolates of Haemophilus influenzae and Moraxella catarrhalis collected from across Canada in 1997-1998

Between September 1997 and November 1998 respiratory tract isolates of Haemophilus influenzae (n = 1352) and Moraxella catarrhalis (n = 428) were collected by 18 Canadian medical centres. beta-Lactamase was produced by 24.0 and 94.2% of H. influenzae and M. catarrhalis isolates, respectively. Resistance rates for H. influenzae were highest for ampicillin (24.0%), trimethoprim/sulphamethoxazole (13. 7%), loracarbef (6.1%) and cefaclor (4.2%), and </= 1% for amoxycillin/clavulanate, cefotaxime, cefprozil, cefixime, imipenem, ciprofloxacin, levofloxacin, grepafloxacin, trovafloxacin and chloramphenicol. M. catarrhalis resistance rates, derived using NCCLS breakpoint criteria for Haemophilus spp., were </= 1% for all antibiotics tested except ampicillin (49.5%) and trimethoprim/sulphamethoxazole (1.6%).

Moraxella catarrhalis: a review of an important human mucosal pathogen

Moraxella catarrhalis has again been recognized as a significant pathogen. The past decade has witnessed an increased amount of research and understanding of the pathogenesis of the organism. This review will summarize the research pertaining to the epidemiology and components of pathogenesis in M. catarrhalis.

Antimicrobial susceptibility of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis collected from five centers in Brazil, 1997-98

OBJECTIVE

To assess the susceptibility of the key respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis to antimicrobial agents used to treat respiratory tract infections.

METHODS

Isolates were collected from five centers in Brazil during 1997-98, and susceptibility testing was conducted at a central laboratory according to National Committee for Clinical Laboratory Standards criteria.

RESULTS

Of the 359Streptococcus pneumoniae isolates tested, 77% were susceptible, 19% were intermediate and 4% were resistant to penicillin. The susceptibility of S. pneumoniae to other beta-lactams and macrolides was greater than 90%, but cotrimoxazole was active against only 48% of the isolates. The prevalence of susceptible isolates was 100.0% for vancomycin and 99.7% for levofloxacin. beta-Lactam, macrolide, and cotrimoxazole activities were negatively associated with penicillin resistance. Of the 219 isolates of Haemophilus influenzae tested, 11% produced beta-lactamase and 11% were not susceptible to ampicillin. Nearly all H. influenzae isolates were susceptible to all other drugs, except cotrimoxazole (47% susceptibility). Of the 52 Moraxella catarrhalis isolates, 98% produced beta-lactamase, and the MIC of all drugs was </=4 mg/L, with the exception of ampicillin, where the MIC90 was> 8 mg/L.

CONCLUSIONS

When these data are compared with previous reports, our findings suggest that the prevalence of pneumococci that are resistant to agents such as penicillin and cotrimoxazole may be increasing in Brazil, which highlights the need to continue surveillance programs.

In vitro antibacterial activity of gemifloxacin and comparator compounds against common respiratory pathogens

This study investigated the in vitro potency of the novel quinolone agent gemifloxacin (SB-265805), in comparison with other quionolones, beta-lactams, macrolides and trimethoprim- sulphamethoxazole, against a panel of common respiratory pathogens. This panel comprised recent clinical isolates of Streptococcus pneumoniae (n = 347), Haemophilus influenzae (n = 256) and Moraxella catarrhalis (n = 184). Overall, the quinolones were highly active against H. influenzae and were the most potent agents against M. catarrhalis. Gemifloxacin was the most potent quinolone tested against all three species and was four- to 512-fold more potent against pneumococci than trovafloxacin, grepafloxacin, levofloxacin, ciprofloxacin, ofloxacin, gentamicin, cefuroxime, penicillin, ampicillin, clarithromycin, azithromycin or trimethoprim- sulphamethoxazole. Against 19 ofloxacin-intermediate and 52 ofloxacin-resistant strains of S. pneumoniae, gemifloxacin retained activity, and was the only agent tested with MICs of < or =0.5 mg/L. The results of this study demonstrate the excellent in vitro antibacterial activity of gemifloxacin against pathogens commonly associated with respiratory tract infections and suggest that gemifloxacin has significant potential in the treatment of such infections, including those caused by pneumococci considered resistant to other quinolones.

Fluoroquinolone-resistant Haemophilus influenzae: frequency of occurrence and analysis of confirmed strains in the SENTRY antimicrobial surveillance program (North and Latin America)

The incidence of fluoroquinolone-resistant (FQR) Haemophilus influenzae and Moraxella catarrhalis isolated from clinical specimens remains very rare, and the identification of such strains has been previously limited to case reports from diverse geographic locations. During the 1997 through 1998 SENTRY Antimicrobial Surveillance Program, four FQR-H. influenzae (0.13% of all strains) and one FQR-M. catarrhalis strains were identified and confirmed as having elevated MICs to > or =5 FQ class drugs. Among H. influenzae strains, MICs to marketed FQs were > or =0.12 microg/ml with ciprofloxacin MIC results > or =8-fold higher than wild type susceptible strains. The FQR-H. influenzae isolates were then compared with two previously reported strains that were determined to be identical using ribotyping and other molecular methods. In contrast, the SENTRY isolates were all genetically distinct and had mutations in parC and/or gyrA. Isolates having the lowest MIC elevations had a single mutation in gyrA, while isolates with higher MICs had at least one mutation in both studied genes. In general, the single gyr A mutations involved the same position but differed in the amino acid substitution (Ser84Leu or Phe or Ala). The isolates reported outside the SENTRY Program (controls) had an unusual mutation in par C (Gly82Asp) and two mutations in gyr A; producing the highest recorded FQR MICs. The FQR-M. catarrhalis strain was discovered in late 1997 and has been reported before. Although detection of these FQR isolates remains at <1% of all contemporary H. influenzae and M. catarrhalis isolates, surveillance programs will be an important detection method to determine the extent of emerging novel resistance patterns among clinically prevalent fastidious pathogens.

Clinical significance of resistant organisms in otitis media

BACKGROUND

Otitis media is an important health care problem of childhood. The bacteriology of otitis media comprises three main pathogens: Streptococcus pneumoniae, nontypable Haemophilus influenzae and Moraxella catarrhalis. Although the prevalence of resistant strains varies geographically and temporally, antimicrobial resistance is widespread and increasing.

RESISTANCE TO ANTIBIOTIC DRUGS

Among the risk factors for development of resistance in otitis media are antimicrobial use, young age, day-care attendance and prior hospitalization. The increasing rate of resistance to antibiotic drugs is associated with a decreased rate of successful eradication of pathogens from middle ear fluid, which is associated with clinical failure. A bacteriologic cure rate of 80 to 85% is observed for S. pneumoniae and nontypable H. influenzae when serum concentrations exceed the MIC for 40 to 50% of dosing interval. Comparative trials indicate that some of the beta-lactams can achieve bacteriologic eradication in acute otitis media, although major differences in outcome exist among agents based on pathogen, beta-lactamase status and MIC values.

ANTIBIOTIC CHOICE

Overall the choice of antibiotics for treatment of otitis media should take into consideration their in vitro activity against the locally prevalent organisms, especially resistant organisms, and results obtained from studies in which bacteriologic outcome was used as the endpoint.

Resistance surveillance of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis isolated in Asia and Europe, 1997-1998

A multicentre, collaborative study was performed in Asia and Europe during the winter of 1997-1998 to determine the in vitro activity of selected antimicrobial agents against common respiratory pathogens. Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis isolates were collected from 48 sites in China, France, Germany, Italy, Japan, Spain and the UK and tested in a central laboratory in the USA. Broth microdilution MICs were determined for beta-lactams (penicillin, amoxycillin/clavulanate, cefuroxime, ceftriaxone), macrolides (azithromycin, clarithromycin), sulphonamides (co-trimoxazole), glycopeptides (vancomycin) and fluoroquinolones (levofloxacin). The percentage of isolates susceptible to each antimicrobial class varied substantially by country. Penicillin susceptibility amongst pneumococci ranged from 34% in France and Spain to 92% in Germany, and macrolide susceptibility varied between 26% in China and 91% in the UK. In most countries beta-lactam, macrolide and cotrimoxazole resistance was more prevalent amongst penicillin-intermediate and -resistant S. pneumoniae isolates. However, little or no resistance was detected to levofloxacin (0.3% intermediate and resistant) or vancomycin (0% intermediate and resistant). For H. influenzae the prevalence of beta-lactamase production varied from 6% in China and Germany to 32% in Spain, and for M. catarrhalis, from 79% in Germany to 98% in Japan. With the exception of ampicillin, beta-lactamase production had a minimal effect on beta-lactam activity against H. influenzae or M. catarrhalis. Our findings demonstrate that antimicrobial resistance profiles of common respiratory isolates differ dramatically between countries in Asia and Europe.

Carriage of respiratory tract pathogens and molecular epidemiology of Streptococcus pneumoniae colonization in healthy children attending day care centers in Lisbon, Portugal

In an effort to establish the rate of carriage of antibiotic resistant respiratory pathogens in children attending urban day care centers (DCC) in Portugal, seven DCC in Lisbon were selected for determining the rate of nasopharyngeal colonization of children between the ages of 6 months to 6 years by Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Of the 586 children studied between January and March 1996, 47% carried S. pneumoniae, 72% H. influenzae, and 54% M. catarrhalis. Twenty-four percent of the pneumococci had reduced susceptibility to penicillin, and most of these belonged to serogroups 19, 23, 14, and 6. An additional 19% were fully susceptible to penicillin but showed decreased susceptibility to other antimicrobials. These isolates expressed serogroups 6, 11, 14, 18, 19, and 34. The majority (96%) of M. catarrhalis and 20% of H. influenzae were penicillin resistant due to the production of beta-lactamases. Recent antimicrobial use was associated with carriage of penicillin non-susceptible pneumococci and beta-lactamase producing H. influenzae (p < 0.05). Individual DCC differed substantially from one another in their rates of carriage of antibiotic resistant H. influenzae and S. pneumoniae. Characterization of antibiotic resistant S. pneumoniae isolates by molecular fingerprinting techniques showed that each DCC had a unique microbiological profile, suggesting little, if any, exchange of the resistant microbial flora among them. An exception to this was the presence of isolates belonging to two internationally spread epidemic clones: the multiresistant Spanish/USA clone expressing serotype 23F, and the penicillin and sulfamethoxazole-trimethoprim resistant French/Spanish clone (serotype 14) which were detected in four and three DCC, respectively.

Substituent effects on the antibacterial activity of nitrogen-carbon-linked (azolylphenyl)oxazolidinones with expanded activity against the fastidious gram-negative organisms Haemophilus influenzae and Moraxella catarrhalis

A series of new nitrogen-carbon-linked (azolylphenyl)oxazolidinone antibacterial agents has been prepared in an effort to expand the spectrum of activity of this class of antibiotics to include Gram-negative organisms. Pyrrole, pyrazole, imidazole, triazole, and tetrazole moieties have been used to replace the morpholine ring of linezolid (2). These changes resulted in the preparation of compounds with good activity against the fastidious Gram-negative organisms Haemophilus influenzae and Moraxella catarrhalis. The unsubstituted pyrrolyl analogue 3 and the 1H-1,2,3-triazolyl analogue 6 have MICs against H. influenzae = 4 microgram/mL and M. catarrhalis = 2 microgram/mL. Various substituents were also placed on the azole moieties in order to study their effects on antibacterial activity in vitro and in vivo. Interesting differences in activity were observed for many analogues that cannot be rationalized solely on the basis of sterics and position/number of nitrogen atoms in the azole ring. Differences in activity rely strongly on subtle changes in the electronic character of the overall azole systems. Aldehyde, aldoxime, and cyano azoles generally led to dramatic improvements in activity against both Gram-positive and Gram-negative bacteria relative to unsubstituted counterparts. However, amide, ester, amino, hydroxy, alkoxy, and alkyl substituents resulted in no improvement or a loss in antibacterial activity. The placement of a cyano moiety on the azole often generates analogues with interesting antibacterial activity in vitro and in vivo. In particular, the 3-cyanopyrrole, 4-cyanopyrazole, and 4-cyano-1H-1,2,3-triazole congeners 28, 50, and 90 had S. aureus MICs </= 0.5-1 microgram/mL and H. influenzae and M. catarrhalis MICs = 2-4 microgram/mL. These analogues are also very effective versus S. aureus and S. pneumoniae in mouse models of human infection with ED(50)s in the range of 1. 2-1.9 mg/kg versus 2.8-4.0 mg/kg for the eperezolid (1) control.

Activities and postantibiotic effects of gemifloxacin compared to those of 11 other agents against Haemophilus influenzae and Moraxella catarrhalis

The activity of gemifloxacin against Haemophilus influenzae and Moraxella catarrhalis was compared to those of 11 other agents. All quinolones were very active (MICs, </=0.125 microgram/ml) against 248 quinolone-susceptible H. influenzae isolates (40.7% of which were beta-lactamase positive); cefixime (MICs, </=0.125 microgram/ml) and amoxicillin-clavulanate (MICs </=4.0 microgram/ml) were active, followed by cefuroxime (MICs, </=16.0 microgram/ml); azithromycin MICs were </=4.0 microg/ml. For nine H. influenzae isolates with reduced quinolone susceptibilities, the MICs at which 50% of isolates are inhibited (MIC(50)s) were 0.25 microgram/ml for gemifloxacin and 1.0 microgram/ml for the other quinolones tested. All strains had mutations in GyrA (Ser84, Asp88); most also had mutations in ParC (Asp83, Ser84, Glu88) and ParE (Asp420, Ser458), and only one had a mutation in GyrB (Gln468). All quinolones tested were equally active (MICs, </=0.06 microgram/ml) against 50 M. catarrhalis strains; amoxicillin-clavulanate, cefixime, cefuroxime, and azithromycin were very active. Against 10 H. influenzae strains gemifloxacin, levofloxacin, sparfloxacin, and trovafloxacin at 2x the MIC and ciprofloxacin at 4x the MIC were uniformly bactericidal after 24 h, and against 9 of 10 strains grepafloxacin at 2x the MIC was bactericidal after 24 h. After 24 h bactericidal activity was seen with amoxicillin-clavulanate at 2x the MIC for all strains, cefixime at 2x the MIC for 9 of 10 strains, cefuroxime at 4x the MIC for all strains, and azithromycin at 2x the MIC for all strains. All quinolones except grepafloxacin (which was bactericidal against four of five strains) and all ss-lactams at 2x to 4x the MIC were bactericidal against five M. catarrhalis strains after 24 h; azithromycin at the MIC was bactericidal against all strains after 24 h. The postantibiotic effects (PAEs) against four quinolone-susceptible H. influenzae strains were as follows: gemifloxacin, 0.3 to 2.3 h; ciprofloxacin, 1.3 to 4.2 h; levofloxacin, 2.8 to 6.2 h; sparfloxacin, 0.6 to 3.0 h; grepafloxacin, 0 to 2.1 h; trovafloxacin, 0.8 to 2.8 h. At 10x the MIC, no quinolone PAEs were found against the strain for which quinolone MICs were increased. Azithromycin PAEs were 3.7 to 7.3 h.

[National multicenter study of the in vitro activity of moxifloxacin against respiratory tract pathogens. Spanish Study Group on Moxifloxacin]

The activity of moxifloxacin, a novel 8-methoxyquinolone, was evaluated against 1,218 respiratory pathogens isolated in nine Spanish hospitals and was compared with ciprofloxacin, sparfloxacin, amoxicillin, amoxicillin-clavulanic acid, cefuroxime, erythromycin and clarithromycin. Moxifloxacin exhibited an excellent in vitro activity against most tested isolates with MIC90 values of 0.25 mg/l for Streptococcus pneumoniae and viridans group streptococci; 0.12 mg/l for Streptococcus pyogenes; 0.25 mg/l for Streptococcus agalactiae; 0.06 and 4 mg/l for methicillin-susceptible and -resistant Staphylococcus aureus, respectively; 0.06 mg/l for Haemophilus influenzae and 0.12 mg/l for Moraxella catarrhalis. Moxifloxacin susceptibility rates were not affected by penicillin resistance in S. pneumoniae and S. viridans, by the betalactamase production in H. influenzae and M. catarrhalis or by macrolide resistance. Moxifloxacin was twice as active as sparfloxacin and four to sixteen times more active than ciprofloxacin against Gram-positive isolates. Sparfloxacin and ciprofloxacin were slightly more active than moxifloxacin when tested against H. influenzae and M. catarrhalis isolates. The microbiological data obtained confirm that moxifloxacin is a promising antimicrobial agent for treating respiratory tract infections.

Antibiotic-sensitivity of Moraxella catarrhalis isolated from clinical materials in 1997-1998

Moraxella catarrhalis (M. catarrhalis) may normally be found in the upper respiratory tract. This bacterium, however, may cause infections such as acute otitis media, sinusitis, conjunctivitis, bronchitis chronica, pneumonia, endocarditis, septicaemia and meningitis. Haemophilus influenzae, Streptococcus pneumoniae and M. catarrhalis were the main causative agents responsible for respiratory tract infections. The major resistance problems associated with these species are those which cause resistance to beta-lactams. beta-lactamase was produced by > 80% M. catarrhalis strains. The susceptibility to ampicillin, amoxicillin/clavulanic acid, cefuroxime, erythromycin, ciprofloxacin was tested in 137 M. catarrhalis strains. All the strains resistant to ampicillin produced beta-lactamase and were sensitive to amoxicillin/clavulanic acid. For M. catarrhalis, the most active antimicrobials included cefuroxime (99%), ciprofloxacin (99%) and erythromycin (93%).

Bacteriologic and clinical efficacy of amoxicillin/clavulanate vs. azithromycin in acute otitis media

OBJECTIVES

To compare the bacteriologic and clinical efficacy of amoxicillin/clavulanate and azithromycin in patients with acute otitis media (AOM), particularly the ability to eradicate the predominant AOM pathogens from middle ear fluid as assessed by mandatory second tympanocentesis.

METHODS

In this single blind study 238 infants and children with AOM were randomized to receive amoxicillin/clavulanate (45/6.4 mg/kg/day in two divided doses for 10 days) or azithromycin (10 mg/kg on Day 1, then 5 mg/kg daily on Days 2 through 5). Tympanocentesis was performed before the first dose and repeated on Day 4, 5 or 6. Clinical response was assessed at end of therapy between Days 12 and 14 and at follow-up between Days 22 and 28.

RESULTS

Amoxicillin/clavulanate was significantly more likely to eradicate all bacterial pathogens [83% (54 of 65) vs. 49% (35 of 71), P = 0.001] and Haemophilus influenzae [87% (26 of 30) vs. 39% (13 of 33), P = 0.0001] from middle ear fluid than was azithromycin. Amoxicillin/clavulanate was also more likely to eradicate Streptococcus pneumoniae, but the difference was not statistically significant [90% (18 of 20) vs. 68% (13 of 19) [corrected], P = 0.095]. On Days 12 to 14, signs and symptoms were more likely to resolve completely or improve in all culture-positive patients [86% (60 of 70) vs. 70% (51 of 73), P = 0.023] and in those with H. influenzae infections [91% (30 of 33) vs. 65% (22 of 34), P = 0.010] who received amoxicillin/clavulanate compared with those who received azithromycin. Otherwise there were no significant differences between groups in clinical outcomes on Days 12 to 14 or at follow-up.

CONCLUSIONS

Our findings indicate that amoxicillin/clavulanate has superior bacteriologic and clinical efficacy compared with azithromycin in children with AOM.