Identification of a 3-deoxy-D-manno-octulosonic acid biosynthetic operon in Moraxella catarrhalis and analysis of a KdsA-deficient isogenic mutant

Lipooligosaccharide (LOS), a predominant surface-exposed component of the outer membrane, has been implicated as a virulence factor in the pathogenesis of Moraxella catarrhalis infections. However, the critical steps involved in the biosynthesis and assembly of M. catarrhalis LOS currently remain undefined. In this study, we used random transposon mutagenesis to identify a 3-deoxy-D-manno-octulosonic acid (KDO) biosynthetic operon in M. catarrhalis with the gene order pyrG-kdsA-eno. The lipid A-KDO molecule serves as the acceptor onto which a variety of glycosyl transferases sequentially add the core and branch oligosaccharide extensions for the LOS molecule. KdsA, the KDO-8-phosphate synthase, catalyzes the first step of KDO biosynthesis and is an essential enzyme in gram-negative enteric bacteria for maintenance of bacterial viability. We report the construction of an isogenic M. catarrhalis kdsA mutant in strain 7169 by allelic exchange. Our data indicate that an LOS molecule consisting only of lipid A and lacking KDO glycosylation is sufficient to sustain M. catarrhalis survival in vitro. In addition, comparative growth and susceptibility assays were performed to assess the sensitivity of 7169kdsA11 compared to that of the parental strain. The results of these studies demonstrate that the native LOS molecule is an important factor in maintaining the integrity of the outer membrane and suggest that LOS is a critical component involved in the ability of M. catarrhalis to resist the bactericidal activity of human sera.

Comparison of BSAC agar dilution and NCCLS broth microdilution MIC methods for in vitro susceptibility testing of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis: the BSAC Respiratory Resistance Surveillance Programme

OBJECTIVE

The aim of this study was to establish the degree of comparability between the NCCLS broth microdilution and BSAC agar dilution MIC methods of antimicrobial susceptibility testing.

METHODS

Six hundred and sixty-one clinical isolates of Streptococcus pneumoniae, 936 Haemophilus influenzae and 421 Moraxella catarrhalis, collected in the winter of 1999-2000 by 20 laboratories in the UK and Eire from patients with presumed community-acquired lower respiratory infections, were tested by the two methods. MIC agreement was defined as excellent (good) if results were within +/- 1 doubling dilution for > or =90% (> or =80%) of isolates and within +/- 2 doubling dilutions for > or =95%. Isolates were categorized as susceptible, intermediate or resistant using the breakpoints appropriate to the testing method.

RESULTS

MIC agreement was good or excellent in 27 of 36 organism-agent combinations. Agreement was less for M. catarrhalis than for other species, and lower in all three species for cefaclor and trimethoprim than for other antimicrobials. Discrepancies in categorization occurred only occasionally, and were generally explained by differences in breakpoints rather than in measured MICs. One exception was S. pneumoniae with penicillin. Despite excellent MIC agreement and identical breakpoints, 9% of these had minor discrepancies, mainly because 7% of isolates were found intermediate by the BSAC method but resistant by the NCCLS method.

CONCLUSION

There is generally very good agreement between the MICs obtained by the BSAC agar dilution and NCCLS broth microdilution methods in this population of isolates, comparable to the level of agreement achieved between different laboratories using a single method. Breakpoint differences contribute to most of the discrepancies in susceptibility categorization.

Antimicrobial susceptibility of lower respiratory tract pathogens in Great Britain and Ireland 1999-2001 related to demographic and geographical factors: the BSAC Respiratory Resistance Surveillance Programme

OBJECTIVE

The aim of this study was to assess the antimicrobial susceptibility of community-acquired lower respiratory pathogens in Great Britain and Ireland, and investigate its relationship with demographic and geographical factors using multiple logistic regression analysis.

METHODS

A total of 1328 isolates of Streptococcus pneumoniae, 1894 Haemophilus influenzae and 845 Moraxella catarrhalis were collected from lower respiratory clinical specimens (primarily sputum) by 20 laboratories in Great Britain (England, Wales and Scotland) and Ireland (Northern Ireland and Eire) between 1999 and 2001.

RESULTS

Of 1154 S. pneumoniae from Great Britain, 92-100% were susceptible to beta-lactams (only 0.2% having penicillin MICs > or =2 mg/L), 89% were susceptible to erythromycin, 93% susceptible to tetracycline, and 94-100% intermediate or susceptible to fluoroquinolones. Susceptibility to agents other than fluoroquinolones was less frequent in the 174 isolates from Ireland: beta-lactam susceptibility was 68-99% (3.4% having penicillin MICs > or =2 mg/L), erythromycin susceptibility was 78% and tetracycline susceptibility was 82%. In multivariate analysis, susceptibility in S. pneumoniae was associated with country and patient age, being most common overall in the 20-49 years age group. Of 1894 H. influenzae, 15% produced beta-lactamase and 79-100% were susceptible to beta-lactams other than cefaclor. Ninety-six per cent were intermediate and 1% susceptible to erythromycin, 97% susceptible to tetracycline, and 89% susceptible to trimethoprim. Only one isolate showed resistance to ciprofloxacin. H. influenzae from sputum were more likely to be susceptible than isolates from other sources. Of 845 M. catarrhalis, 92% produced beta-lactamase and 9% were susceptible to ampicillin, >99% were susceptible to co-amoxiclav, cefotaxime, erythromycin and fluoroquinolones.

CONCLUSIONS

Clinically relevant demographic factors predictive of susceptibility were country and patient age in S. pneumoniae, and specimen type (sputum/non-sputum) in H. influenzae. Susceptibility to most antimicrobials remains high in Ireland and very high in Great Britain.

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

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

In vitro activity of telithromycin compared with macrolides and fluoroquinolones against Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis

The in vitro activity of telithromycin was compared with erythromycin A, azithromycin, clarithromycin, moxifloxacin, gemifloxacin, levofloxacin, ciprofloxacin, penicillin G, ampicillin, cefuroxime and ceftriaxone against 336 consecutive strains (83 Streptococcus pneumoniae, 168 Haemophilus influenzae and 85 Moraxella catarrhalis) isolated from patients with community-acquired respiratory tract infections. Telithromycin (MIC(90), 0.008 mg/l) was the most active drug against S. pneumoniae. Telithromycin was also highly active against M. catarrhalis (MIC(90), 0.06 mg/l), but less active against H. influenzae (MIC(90), 4 mg/l).

Contemporary evaluation of the in vitro activity and spectrum of cefdinir compared with other orally administered antimicrobials tested against common respiratory tract pathogens (2000-2002)

Cefdinir is an oral cephalosporin approved by the Food and Drug Administration in 1997 for the treatment of acute exacerbation of chronic bronchitis, pharyngitis-tonsillitis, community-acquired pneumonia, acute maxillary sinusitis, and uncomplicated skin and skin structure infections in adults and adolescents, and acute otitis media, pharyngitis-tonsillitis, and uncomplicated skin and skin structure infections in children. Although cefdinir showed similar activity to other cephalosporins in the early studies, very limited data has been generated over the last decade. In this report, we summarize the contemporary in vitro activity and spectrum of cefdinir in comparison to numerous other orally administrated antimicrobials available for treatment of community-acquired respiratory infections. A total of 8,326 non-duplicate recent clinical isolates, including Haemophilus influenzae (3,438), Moraxella catarrhalis (1,688), and Streptococcus pneumoniae (3,200), were collected from 35 medical centers in North America during 2000 through 2002, and susceptibility tested by reference broth microdilution methods. Pneumococcal susceptibility patterns for beta-lactams and macrolides were also analyzed according to the year of isolation and the age group of the patients. Cefdinir had the greatest activity against H. influenzae among the cephalosporins tested with susceptibility rates of 97.1 to 99.0%. All of the agents tested had complete or near complete activity against M. catarrhalis. Against S. pneumoniae, cefdinir and other cephalosporins showed similar susceptibility patterns, but improved rates were observed in 2002 (78.5-79.4%) when compared to the previous monitored period (71.8-74.5%). This increase in susceptibility was mainly because of a declining the occurrence of high-level penicillin resistance (MIC >/=2 microg/ml) across all age groups. Macrolide resistance also decreased among S. pneumoniae in 2002 when compared to 2000 through 2001; however, resistance to levofloxacin continued to increase from 0.9% in 2000 to 1.4% in 2002. These results indicate a significant change in emerging beta-lactam resistance patterns (including cefdinir) with a decrease possibly influenced by greater pneumococcal vaccine use in children and the elderly. These rates of increased susceptibility could sustain and enhance the clinical activity of orally administered beta-lactams such as cefdinir.

Susceptibility trends of haemophilus influenzae and Moraxella catarrhalis against orally administered antimicrobial agents: five-year report from the SENTRY Antimicrobial Surveillance Program

The assessment of orally administered antimicrobial susceptibilities of common pathogens that cause community-acquired respiratory tract infections (CARTI) has become exceedingly important due to the number of office visits for this indication. Numerous local, regional and global studies have documented the susceptibilities of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis, the most common CARTI pathogens. SENTRY Antimicrobial Surveillance Program sites in North and Latin America, and Europe were requested to send a combined total of 100 isolates of these pathogens to the local monitor for reference broth microdilution testing (1997-2001). This study compared the susceptibility profiles of H. influenzae and M. catarrhalis isolates (13,370 strains) from the three geographic regions over a five year period. beta-lactamase mediated ampicillin resistance among H. influenzae was highest among North American isolates (27.9%) compared to Latin America and Europe (16.2 to 16.3%), although it was noted that during the five year study period, ampicillin resistance was steadily increasing in the latter two regions. Cefprozil (84.3% susceptible) and clarithromycin (81.1% susceptible) were also less active against North American H. influenzae isolates. Latin American isolates were much less susceptible to trimethoprim/sulfamethoxazole (T/S; 59.3%) compared to the other regions (75.8 to 78.6%). M. catarrhalis isolates were also significantly less susceptible to T/S in Latin America (10.5% resistance). The production of beta-lactamase enzymes among the M. catarrhalis isolates exceeded >95% in all three regions during the five year period. The fluoroquinolones (FQ) remained very active against these two respiratory pathogens with rare isolates with elevated FQ MIC results. It is apparent from this investigation that many commonly prescribed empiric treatments remain viable therapeutic options for CARTI caused by these two Gram-negative respiratory tract pathogens.

Macrolide resistance: an increasing concern for treatment failure in children

BACKGROUND

Antimicrobial treatment of pediatric respiratory tract infections has evolved during the past 30 years as a result of antimicrobial resistance. The focus of antimicrobial therapy in these conditions has shifted from penicillins to other agents because of the dramatic increase in antimicrobial resistance among common respiratory pathogens, including Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. It is important for clinicians to understand how resistance develops so that they can help prevent this phenomenon from occurring with other antimicrobials.

METHODS

This article reviews the published literature on resistance to macrolide antimicrobials among common pediatric respiratory tract pathogens and clinical and bacteriologic outcomes of infections with these pathogens.

RESULTS

Resistance among common pediatric respiratory tract pathogens to macrolides occurs through two main mechanisms, alteration of the target site and active efflux. Although resistance patterns vary by geographic region, the widespread use of macrolides has contributed to the emergence of both types of macrolide-resistant organisms. Conditions that favor the selection and proliferation of resistant strains include children with repeated, close contact who frequently receive antimicrobial treatment or prophylaxis, such as children who attend day care. Recent US surveillance data show that 20 to 30% of S. pneumoniae are resistant to macrolides, with approximately two-thirds of macrolide-resistant strains associated with an efflux mechanism and the remainder associated with a ribosomal methylase. Additionally, although less well-known, virtually all strains of H. influenzae have an intrinsic macrolide efflux pump. As resistance to macrolides has increased, clinical failures have resulted, and these agents are no longer considered appropriate for empiric first line antimicrobial therapy of acute otitis media and sinusitis unless patients are truly penicillin-allergic. Therefore, other antimicrobials are recommended for the empiric treatment of children with respiratory tract infections, including higher doses of amoxicillin and amoxicillin/clavulanate (90 mg/kg/day amoxicillin), cefuroxime axetil and intramuscular ceftriaxone.

CONCLUSIONS

As resistance to macrolides increases and clinical failures in children become more common with this class of antimicrobials, judicious use of antimicrobials is needed. This includes limiting antimicrobial use for viral infections and using the most effective agents when antimicrobials are clinically indicated, such as higher doses of amoxicillin and amoxicillin/clavulanate. Application of these principles may prevent proliferation and further development of resistance.

Amoxicillin/clavulanate for infections in infants and children: past, present and future

Chemical synthesis of the penicillin nucleus in the 1950s made introduction of a broad array of new and important antimicrobials, including ampicillin and amoxicillin, possible. Ampicillin was introduced in 1962 in oral and parenteral forms as the first of the semisynthetic penicillins to provide increased activity against Gram-negative bacteria. Amoxicillin replaced oral ampicillin beginning in 1974 because amoxicillin resulted in higher and more prolonged serum concentrations than did equivalent doses of ampicillin. Amoxicillin/clavulanate (Augmentin) was introduced in the United States in 1984 to enhance the activity of amoxicillin by addition of the beta-lactamase inhibitor, clavulanic acid. During the past 20 years, amoxicillin/clavulanate has proven effective for a variety of pediatric infectious diseases, particularly acute otitis media (AOM). In 2001, a new pediatric formulation, high dose amoxicillin/clavulanate (Augmentin ES-600) was approved for use in the United States. The high dose preparation addressed the needs of pediatricians by providing greater amounts of amoxicillin while maintaining the same daily dose of clavulanic acid as the regular strength formulation. Doubling the dose of amoxicillin for management of recurrent and persistent AOM was recommended in 1999 by the Centers for Disease Control and Prevention because of concern about the increased incidence of nonsusceptible strains of Streptococcus pneumoniae. The original formulation combined amoxicillin/clavulanate in a 4:1 ratio and was followed by a 7:1 ratio formulation. The high dose formulation (600 mg of amoxicillin per 5 ml) provides a 14:1 ratio of amoxicillin to clavulanate. Although management of AOM will likely undergo changes in the coming years, amoxicillin is expected to remain first line therapy for AOM. For children who fail initial therapy with amoxicillin, high dose amoxicillin/clavulanate, an oral cephalosporin or parenteral ceftriaxone is recommended.

The Alexander Project 1998-2000: susceptibility of pathogens isolated from community-acquired respiratory tract infection to commonly used antimicrobial agents

OBJECTIVES

The Alexander Project is a continuing surveillance study, begun in 1992, examining the susceptibility of pathogens involved in adult community-acquired respiratory tract infections (CARTI) to a range of antimicrobial agents.

MATERIALS AND METHODS

This study tested the susceptibility of isolates of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis collected between 1998 and 2000 to 23 antimicrobials. Minimum inhibitory concentrations of agents were determined using the broth microdilution method and interpreted according to NCCLS and pharmacokinetic/pharmacodynamic (PK/PD) breakpoints.

RESULTS

In total, 8882 isolates of S. pneumoniae, 8523 isolates of H. influenzae and 874 isolates of M. catarrhalis were collected during 1998-2000 from centres in 26 countries. The world-wide prevalence of penicillin resistance (penicillin MICs > or = 2 mg/l) in isolates of S. pneumoniae was 18.2% over the study period, and the prevalence of macrolide resistance (erythromycin MICs > or = 1 mg/l) in this pathogen was 24.6%. Over the study period, macrolide resistance exceeded penicillin resistance in 19 of the 26 countries included in the study. Of the non-fluoroquinolone agents, the only oral agents to which over 90% of S. pneumoniae isolates were susceptible at both NCCLS and PK/PD breakpoints were amoxicillin (95.1%) and co-amoxiclav (95.5-97.9%). The prevalence of fluoroquinolone-resistant S. pneumoniae (ofloxacin MICs > or = 8 mg/l) was 1.1%. Gemifloxacin was the most potent fluoroquinolone tested against S. pneumoniae (99.9% susceptible). In isolates of H. influenzae, beta-lactamase production was 16.9%, whereas the prevalence of beta-lactamase-negative, ampicillin-resistant strains was low (0.2%). beta-Lactamase production in M. catarrhalis world-wide remained high over the period studied (92.1%). Using PK/PD breakpoints, the most active non-fluoroquinolone agents against H. influenzae were ceftriaxone (100% susceptible), cefixime (99.8%) and co-amoxiclav (98.1-99.6%). Co-amoxiclav, cefdinir and cefixime (100%) were the most active beta-lactams against M. catarrhalis. Both H. influenzae and M. catarrhalis were highly susceptible to the fluoroquinolones.

CONCLUSIONS

These data demonstrate the continued evolution of and geographical variation in bacterial resistance and highlight the need for appropriate prescribing of antimicrobials in CARTI, using agents with adequate activity, based on local susceptibility profiles and PK/PD parameters.

Worldwide trends in antimicrobial resistance among common respiratory tract pathogens in children

BACKGROUND

Respiratory tract infections among children are a common reason for health care provider visits and the primary reason for antimicrobial prescribing in this population. The increased prevalence of resistance among Streptococcus pneumoniae and Haemophilus influenzae pathogens poses a serious challenge in the successful treatment of respiratory tract infections caused by these pathogens.

METHODS

This paper reviews worldwide trends in antimicrobial resistance among common respiratory tract pathogens, highlighting data obtained from the pediatric population where available.

RESULTS

S. pneumoniae resistance to beta-lactams is mediated through alterations in the penicillin-binding proteins and macrolide resistance to acquisition of efflux or methylation genes. The mechanisms of resistance to the fluoroquinolones include target enzyme alterations via genetic mutations and transport out of the bacterial cell via an efflux pump. Beta-lactamase production is the primary mechanism of resistance to penicillins among H. influenzae isolates. Although S. pneumoniae with reduced susceptibility to penicillin was first documented > 30 years ago, resistance has increased at an alarming rate worldwide in the past decade. According to recent surveillance data, the worldwide prevalence of S. pneumoniae with reduced susceptibility to penicillin is 18.2%. Beta-lactamase production among H. influenzae ranges from approximately 4% in Russia to 26% in the United States and to 31% in France. The prevalence of beta-lactamase-negative, ampicillin-resistant H. influenzae remains very low (< 1%) worldwide, except in Japan, where the incidence is higher. In general, the highest rates of resistance are observed in isolates obtained from children, and risk factors for infection with a resistant pathogen include young age, the site of infection, day-care center attendance and recent antimicrobial use.

CONCLUSIONS

Increased prevalence of antimicrobial resistance among respiratory tract pathogens isolated from children and adults is evident worldwide. Treatment of infections caused by S. pneumoniae and H. influenzae with older agents or ineffective dosing regimens may not eradicate infections and may contribute to the spread of resistance. These observations confirm the need for appropriate antimicrobial use to halt or at least limit the spread of resistance.

Antimicrobial activity of LB10827, a new orally administered cephalosporin, tested against Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae

A new orally administered cephalosporin, LB10827, was compared to 16 other antimicrobial agents tested against Streptococcus pneumoniae (520 strains), Haemophilus influenzae (302 strains) and Moraxella catarrhalis (188 strains) by reference broth microdilution methods. LB10827 (MIC90, 0.12 mg/L; highest MIC, 0.5 mg/L) was 8-16-fold more potent than cefdinir, cefpodoxime or cefuroxime when tested against S. pneumoniae. All Gram-negative strains were inhibited at </= 0.5 mg/L LB10827, which is an activity equal or superior to that of currently available and tested oral beta-lactams. LB10827 appears to be a promising agent worthy of continued investigations both in vitro and in vivo.

In vitro susceptibility of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis: a European multicenter study during 2000-2001

OBJECTIVE

To assess the current (2001) activity of respiratory fluoroquinolones and comparator agents against respiratory pathogens isolated in European countries.

METHODS

During 2000-2001, we prospectively collected 1995 isolates of Haemophilus influenzae, 1870 isolates of Streptococcus pneumoniae and 649 isolates of Moraxella catarrhalis from hospital laboratories in France, Germany, Greece, Italy, Spain and the UK. National Committee for Clinical Laboratory Standards (NCCLS)-approved broth microdilution antimicrobial susceptibility testing methods and interpretive criteria were used throughout.

RESULTS

Of the S. pneumoniae isolates, 99.6% were susceptible to moxifloxacin, gatifloxacin and levofloxacin; the corresponding figure for H. influenzae was 100%. All M. catarrhalis isolates had moxifloxacin MICs </= 0.12 mg/L. For all three pathogens, fluoroquinolone susceptibility remained unchanged from the previous 1997-98 study. The incidence of penicillin non-susceptibility in the S. pneumoniae isolates tested remained similar to or higher than that recorded in previous studies: France, 165/291 (56.7%); Germany, 46/506 (9.1%); Greece, 20/55 (36.4%); Italy, 45/364 (12.4%); Spain, 146/268 (54.5%); and the UK, 26/386 (6.7%). Significant levels of resistance to oral compounds (cefuroxime, cefaclor, cefdinir, clarithromycin, azithromycin, tetracycline, and trimethoprim-sulfamethoxazole) were detected among S. pneumoniae isolates. beta-Lactamase production among H. influenzae isolates ranged from 6.2% to 33.1% per country, and ampicillin, clarithromycin or trimethoprim-sulfamethoxazole resistance were the most common phenotypes detected. beta-Lactamase production among M. catarrhalis isolates ranged from 94.1% to 100% per country.

CONCLUSIONS

With the exception of a few localized reports, resistance to moxifloxacin and other new fluoroquinolones in common respiratory pathogens is a rare occurrence, despite significant resistance to other compound classes. Surveillance will play a key role in tracking changes in fluoroquinolone susceptibility in European countries.

Antimicrobial resistance in Haemophilus influenzae and Moraxella catarrhalis respiratory tract isolates: results of the Canadian Respiratory Organism Susceptibility Study, 1997 to 2002

A total of 7,566 unique patient isolates of Haemophilus influenzae and 2,314 unique patient isolates of Moraxella catarrhalis were collected between October 1997 and June 2002 from 25 medical centers in 9 of the 10 Canadian provinces. Among the 7,566 H. influenzae isolates, 22.5% produced beta-lactamase, while 92.4% of the 2,314 M. catarrhalis isolates produced beta-lactamase. The incidence of beta-lactamase-producing H. influenzae isolates decreased significantly over the 5-year study period, from 24.2% in 1997-1998 to 18.6% in 2001-2002 (P < 0.01). The incidence of beta-lactamase-producing M. catarrhalis isolates did not change over the study period. The overall rates of resistance to amoxicillin and amoxicillin-clavulanate for H. influenzae were 19.3 and 0.1%, respectively. The rank order of cephalosporin activity based on the MICs at which 90% of isolates were inhibited (MIC(90)s) was cefotaxime > cefixime > cefuroxime > cefprozil > cefaclor. On the basis of the MICs, azithromycin was more active than clarithromycin (14-OH clarithromycin was not tested); however, on the basis of the NCCLS breakpoints, resistance rates were 2.1 and 1.6%, respectively. Rates of resistance to other agents were as follows: doxycycline, 1.5%; trimethoprim-sulfamethoxazole, 14.2%; and chloramphenicol, 0.2%. All fluoroquinolones tested, including the investigational fluoroquinolones BMS284756 (garenoxacin) and ABT-492, displayed potent activities against H. influenzae, with MIC(90)s of < or = 0.03 microg/ml. The MIC(90)s of the investigational ketolides telithromycin and ABT-773 were 2 and 4 microg/ml, respectively, and the MIC(90) of the investigational glycylcycline GAR-936 (tigecycline) was 4 microg/ml. Among the M. catarrhalis isolates tested, the resistance rates derived by using the NCCLS breakpoint criteria for H. influenzae were <1% for all antibiotics tested except trimethoprim-sulfamethoxazole (1.5%). In summary, the incidence of beta-lactamase-positive H. influenzae strains in Canada is decreasing (18.6% in 2001-2002), while the incidence of beta-lactamase-positive M. catarrhalis strains has remained constant (90.0% in 2001-2002).

The in vitro effects of faropenem on lower respiratory tract pathogens isolated in the United Kingdom

Faropenem is a new oral penem with a structure different from current beta-lactams including carbapenems. The susceptibility of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis to faropenem, a macrolide, a beta-lactam, a beta-lactam/beta-lactamase inhibitor combination and two fluoroquinolones was investigated. S. pneumoniae was the most susceptible of the three species to faropenem. The MIC(90)s of faropenem against M. catarrhalis and H. influenzae were 0.5 and 1 mg/l, respectively. They were similar to amoxiclav (MIC (90)s of 0.25 and 0.5 mg/l). The quinolones showed strong activity against H. influenzae. A cluster analysis of the activities of amoxycillin and faropenem demonstrated a direct relationship between the two antimicrobial agent's activities and resistance profiles against both S. pneumoniae and H. influenzae.

Susceptibilities to levofloxacin in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis clinical isolates from children: results from 2000-2001 and 2001-2002 TRUST studies in the United States

Among respiratory tract isolates of Streptococcus pneumoniae from children, resistance to penicillins, cephalosporins, macrolides, and trimethoprim-sulfamethoxazole (SXT) increases on an annual basis. Pediatric patients who do not respond to conventional therapy for respiratory tract infections someday may be treated with fluoroquinolones. In this study, MICs of beta-lactams, azithromycin, SXT, and levofloxacin were determined and interpreted by using NCCLS guidelines for isolates of S. pneumoniae (2,834 from children and 10,966 from adults), Haemophilus influenzae (629 from children and 2,281 from adults), and Moraxella catarrhalis (389 from children and 1,357 from adults) collected during the 2000-2001 and 2001-2002 respiratory illness seasons in the United States as part of the ongoing TRUST surveillance studies. Rates of resistance to penicillin, azithromycin, and SXT were > or = 7.5% higher among patients < or = 4 years old than among patients 5 to 10, 11 to 17, and > or = 18 years old in both the 2000-2001 and the 2001-2002 respiratory illness seasons. Levofloxacin resistance was detected in 2 of 2,834 isolates (0.07%) from patients <18 years old. Levofloxacin MICs of 0.25 to 1 micro g/ml accounted for 99.6, 99.5, 99.3, 99.7, 98.4, and 98.0% of isolates from patients < 2, 2 to 4, 5 to 10, 11 to 17, 18 to 64, and > 64 years old. Multidrug resistance was twice as common among patients < or = 4 years old (25.3%) as among patients 5 to 10 years old (13.7%), 11 to 17 years old (11.9%), 18 to 64 years old (12.1%), and > 64 years old (12.4%). The most common multidrug resistance phenotype in S. pneumoniae isolates for all age groups was resistance to penicillin, azithromycin, and SXT (70.3 to 76.6%). For H. influenzae and M. catarrhalis isolates from patients < 2, 2 to 4, 5 to 10, 11 to 17, 18 to 64, and > 64 years old, levofloxacin MICs at which 90% of the isolates were inhibited were 0.015 and 0.03 to 0.06 microg/ml, respectively, in the 2000-2001 and 2001-2002 respiratory illness seasons. In the 2000-2001 and 2001-2002 respiratory illness season surveillance studies in the United States, 99.9% of pediatric isolates of S. pneumoniae were susceptible to levofloxacin. If fluoroquinolones become a treatment option for pediatric patients, careful monitoring of fluoroquinolone susceptibilities will be increasingly important in future surveillance studies.

[Antimicrobial activities of macrolides against recent clinical isolates, and analysis of resistant mechanisms]

We examined antibacterial activities of 4 kinds of macrolides, erythromycin (EM), clarithromycin (CAM), azithromycin (AZM) and rokitamycin (RKM), against 6 bacterial species of clinical strains isoleted in 2002. Bacterial isolates used were each 50 strains of methicillin-susceptible Staphylococcus aureus (MSSA), Streptococcus pyogenes, Streptococcus agalactiae, Moraxella (Branhamella) catarrhalis, Haemophilus influenzae and 43 strains of Streptococcus pneumoniae. S. agalactiae were derived from gynecological samples, and other species were isolated from respiratory specimens. Antimicrobial activities against S. aureus, S. pyogenes, S. agalactiae, M. catarrhalis and H. influenzae of 14-membered macrolides, such as EM and CAM, were higher than those of 16-membered macrolide, RKM. By contrast, against S. pneumoniae, RKM was more effective than 14-membered macrolides. Six, three and four strains of S. aureus, S. pyogenes and S. agalactiae, respectively, were resistant to macrolides. Thirty-five among 43 pneumococcal isolates were resistant, and 15 of the 35 were highly-resistant, MIC of > 128 micrograms/ml, to any one of EM, CAM or AZM. Isolation frequency of resistant strains to RKM was lower than those to 14- and 15-membered macrolides: only one strain was highly-resistant and 12 were intermediately-resistant. No resistant strain was recognized in M. catarrhalis and H. influenzae. Further, we analyzed the resistant mechanisms, methylation or efflux, of macrolide resistant strains by the double-disk method. Methylation was major mechanism in S. aureus, and in S. pyogenes, all of the resistance was caused by methylation. In S. agalactiae and S. pneumoniae, methylation and efflux shared about half and half.

Resistance in respiratory tract pathogens and antimicrobial use in Icelandic and Lithuanian children

To assess resistance rates among respiratory tract pathogens and antimicrobial usage of children in Iceland and Lithuania, and to correlate usage patterns with resistance rates, nasopharyngeal swabs were taken from healthy children attending day-care centres in Reykjavik (n = 6) and Vilnius (n = 13), and cultured for pneumococci, Haemophilus influenzae and Moraxella catarrhalis. Information about recent antimicrobial use was obtained by a questionnaire. 50% and 51% carried pneumococci, 59% and 67% carried H. influenzae and 60% and 46% carried M. catarrhalis, in Reykjavik (n = 297) and Vilnius (n = 508), respectively. The prevalence of penicillin non-susceptible pneumococci was 11% in Reykjavik (mainly serotype 6B) and 5% in Vilnius (mainly 23F). At the time of sampling 3% of the children in Reykjavik and 8% in Vilnius were receiving antimicrobials. Children carrying penicillin non-susceptible pneumococci had used antimicrobials more frequently in the preceding month and this was significant for the Icelandic children (p < 0.0002). Antimicrobial use was more common in Vilnius than in Reykjavik, yet antimicrobial resistance was more common in Reykjavik. Resistance rates cannot be predicted only on the basis of recent antimicrobial use.

Antibiotic treatment of acute otorrhea through tympanostomy tube: randomized double-blind placebo-controlled study with daily follow-up

OBJECTIVE

The role of routine antimicrobial treatment of acute middle-ear infections is under debate, because the efficacy of antimicrobials in the resolution of middle-ear fluid has not been unambiguously proven. Acute tube otorrhea is regarded as evidence of acute otitis media, and for methodologic reasons it was chosen to provide objectivity for diagnostics and outcome assessment. The objective of this study was to assess whether amoxicillin-clavulanate accelerates the resolution of acute tube otorrhea.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled study in outpatient setting.

PATIENTS

Volunteer sample of basically healthy 6- to 72-month-old children with a tympanostomy tube. Eligibility required having acute tube otorrhea of <48 hours' of duration and no prior treatment within the last 2 weeks. The mean age of the participants was 25 months; they had a history of 3 episodes of acute otitis media (median), and 99% had manifestations of a concomitant respiratory infection. Of 79 randomized patients, 7 were withdrawn because of adverse events; 66 patients completed the study.

INTERVENTIONS

Amoxicillin-clavulanate (N = 34; 45 mg/kg/d) or matching placebo (N = 32) for 7 days and daily suction of middle-ear fluid through tympanostomy tube.

MAIN OUTCOME MEASURES

Duration of acute tube otorrhea and duration of bacterial growth in middle-ear fluid.

RESULTS

The median duration of tube otorrhea was significantly shorter in amoxicillin-clavulanate than in the placebo group (3 vs 8 days). At the end of the 7-day medication period, tube otorrhea was resolved in 28 of 34 children receiving amoxicillin-clavulanate compared with 13 of 32 children on placebo (treatment-control difference 41%; 95% confidence interval, 20%-63%; number needed to treat, 2.4). The median duration of bacterial growth in middle-ear fluid was shorter in amoxicillin-clavulanate than in the placebo group (1 vs 8 days).

CONCLUSIONS

Oral antibiotic treatment significantly accelerates the resolution of acute tube otorrhea by reducing bacterial growth in middle-ear fluid.

Pathogens in acute otitis media--impact of intermittent penicillin V prophylaxis on infant nasopharyngeal flora

OBJECTIVE

To investigate whether intermittent short-term courses of penicillin V (PcV) administered as intermittent prophylaxis against acute otitis media (AOM) during upper respiratory tract infections altered the nasopharyngeal bacterial flora and/or its susceptibility to penicillin.

METHODS

In a double blind, placebo controlled study 70 children (30 in the PcV group and 40 in the placebo group) were followed for 1 year. At episodes of upper respiratory tract infection the children were given PcV or placebo and then seen by one of the investigators within 3 days. The tympanic membranes were examined by otomicroscopy and a culture from the nasopharynx was obtained. If AOM was found PcV was given (25 mg/kg bw b.i.d) for 5 days. If the child presented normal eardrums or signs of secretory otitis media (SOM) the study treatment was continued for a total of 5 days. All children were also examined bimonthly throughout the study irrespective of episodes of URTI or AOM.

RESULTS

No increase in the number of isolates of S. pneumoniae with reduced susceptibility to penicillin (MIC> or =0.125 mg/l) was noted in either group compared with the incidence in the population in Sweden at the time of the study (when ca. 10% of pneumococci had a reduced susceptibility to penicillin). The number of cultures positive for S. pneumoniae were statistically reduced in children during treatment with PcV compared with children receiving placebo, while the number of cultures positive for H. influenzae and M. catarrhalis were unaffected. No increase in the number of cultures positive for beta-lactamase producing H. influenzae was noted (ca. 10%).

CONCLUSION

Repetitive short term PcV courses during URTI in infants did not increase the number of cultures positive for S. pneumoniae with reduced susceptibility to penicillin or beta-lactamase producing H. influenzae.

The use and resistance to antibiotics in the community

The frequency of resistance to antibiotics among common community-acquired pathogens, and the number of drugs to which they are resistant have been increasing worldwide. The relationship between antibiotic usage and resistance is strongly supported by data from several studies. Countries with the highest per capita antibiotic consumption have the highest resistance. The emergence of penicillin-resistant Streptococcus pneumoniae is related to high consumption of antibiotics in general, as well as to increased use of aminopenicillins and/or probably to wider use of oral cephalosporins. Increased consumption of macrolides, especially the long-acting ones, correlates significantly with the level of macrolide resistance of group A streptococci and S. pneumoniae while increased use of oral cephalosporins might be associated with the increase of beta-lactamase-producing strains of Moraxella catarrhalis. Trimethoprim/sulphamethoxazole resistance is strongly associated with resistance to penicillin. A rise in consumption of fluoroquinolones is consonant with a higher rate of resistance to quinolones of S. pneumoniae, Escherichia coli and other Gram-negative bacteria. Paediatric bacterial isolates are more often resistant to various antimicrobial agents than isolates from adult patients; this higher resistance rate may be due to more frequent antimicrobial treatments in children, and extensive child to child transmission. Reliable data on antimicrobial consumption and resistance should form a basis for national policies devised to reduce the resistance of microorganisms to antibiotics.

Comparative activity of garenoxacin (BMS 284756), a novel desfluoroquinolone, tested against 8,331 isolates from community-acquired respiratory tract infections: North American results from the SENTRY Antimicrobial Surveillance Program (1999-2001)

Emerging resistances to orally administered antimicrobials have escalated among bacteria causing community-acquired respiratory infections (CARTI). The spectrum and potency of garenoxacin, (formerly BMS 284756) was assessed against a collection of CARTI isolates from North American medical centers during a longitudinal surveillance study, the SENTRY Antimicrobial Surveillance Program (1999-2001). A total of 8,331 strains of Hemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae were tested by reference methods and compared to numerous other marketed antimicrobials. Nearly all (95.1%) M. catarrhalis were penicillin-resistant, 27.9% of H. influenzae were ampicillin-resistant and 35.0% of S. pneumoniae had MICs at > or = 0.12 microg/ml for penicillin. Garenoxacin was very active against the three monitored species with MIC(90) values of < or =0.06 microg/ml. Garenoxacin and other quinolones were equally active against the Gram-negative pathogens (except moxifloxacin which was at least twofold less potent versus M. catarrhalis). However, against pneumococci the rank order of potency (MIC(50) in microg/ml) was: gemifloxacin (0.015) > garenoxacin (0.06) > trovafloxacin = moxifloxacin (0.12) > gatifloxacin (0.25) > levofloxacin = ciprofloxacin (1). A trend toward greater resistance worldwide was observed for ciprofloxacin (MIC, > or = 4 microg/ml), increasing from 1.5% in 1999 to 6.8% in 2001. The highest quinolone resistance rate was observed in North America. Garenoxacin, a new desfluoro(6)quinolone, was documented to be very active in vitro (MIC, < or =2 microg/ml) against > 99.9% of all CARTI isolates in the SENTRY Program. Evolving resistances to other antimicrobial classes or among currently used quinolones appear to position this investigational desfluoro(6)quinolone as a potential treatment option for future clinical use in ambulatory patients.

Synthesis and biological evaluation of novel leucomycin analogues modified at the C-3 position. I. Epimerization and methylation of the 3-hydroxyl group

The synthesis and biological evaluation of sixteen-membered macrolides modified at the C-3 position are described. 3-Epi-leucomycin A7 (9), 3-O-acyl-3-epi-leucomycin A7 analogues (11a-11e), 3-O-acylleucomycin A7 analogues (13b-13e) and 3-O-methylleucomycin analogues (16a, 16b and 22) were synthesized via fully protected intermediates (7, 5a, 5b and 20). After appropriate modification, subsequent deprotections were performed to furnish a variety of leucomycin analogues. Methylation of the 3-hydroxyl group was found to improve the pharmacoprofile of leucomycin antibiotics. 3-O-Methylrokitamycin (16b) showed enhanced antibacterial activity in vitro and 3,3''-di-O-methyl-4''-O-(3-methylbutyl)leucomycin V (22) exhibited improved metabolic stability in rat plasma in vitro.

Oral antimicrobial susceptibilities of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolates from Japanese children

The minimum inhibitory concentrations (MICs) of 11 oral antibiotics were measured for 140 Streptococcus pneumoniae, 115 Haemophilus influenzae, and 46 Moraxella catarrhalis strains isolated from Japanese children. The antibiotics selected included a range of commonly prescribed agents together with a selection of new cefems and a penem. Cefditoren was most active against the highly penicillin resistant S. pneumoniae, beta-lactamase-producing H. influenzae and beta-lactamase-negative ampicillin-resistant H. influenzae. However, amoxycillin retained good activity against the penicillin-susceptible or -intermediately resistant S. pneumoniae (88.6%) and most of ampicillin-susceptible or -intermediately resistant H. influenzae (87.9%). We thus consider that amoxycillin remains a useful initial choice for the treatment of paediatric respiratory infections in Japan.

How can we predict bacterial eradication?

Antimicrobial efficacy is measured in vitro by determination of minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of antimicrobials, but these values do not account for fluctuations of drug concentrations within the body or the time course of the drug's in vivo antibacterial activity. However, in vivo bacteriologic efficacy can be predicted by pharmacokinetic/pharmacodynamic (PK/PD) parameters, such as the time for which the serum drug concentration is above the MIC (T>MIC), the ratio of peak serum concentration to the MIC, and the ratio of the area under the 24-h serum concentration-time curve to the MIC (AUC/MIC). Different patterns of antibacterial activity correlate with different PK/PD parameters. For example, a T>MIC of 40-50% of the dosing interval is a good predictor of bacteriologic efficacy for penicillins, cephalosporins, and most macrolides, and an AUC/MIC ratio of at least 25 is required for efficacy with fluoroquinolones and azalides. The PK/PD breakpoint for susceptibility of an organism to a specific dosing regimen of an agent can be determined as the highest MIC met by the relevant PK/PD parameter for bacteriologic efficacy for that agent. These parameters have been validated extensively in animal models, as well as in many human studies where bacteriologic outcome has been determined. The PK/PD breakpoint of an agent is determined primarily by the dosing regimen, and generally applies to all pathogens causing disease at sites where extracellular tissue levels are similar to non-protein-bound serum levels. On this basis, many parenteral beta-lactams are active against almost all strains of Streptococcus pneumoniae, including 'penicillin-non-susceptible' strains, in all body sites except for the central nervous system. Application of PK/PD breakpoints to standard dosing regimens of oral beta-lactams predicts that agents such as cefaclor and cefixime will have efficacy only against penicillin-susceptible strains of S. pneumoniae, while cefuroxime axetil, cefpodoxime and cefdinir will be effective against all penicillin-susceptible as well as many penicillin-intermediate strains. However, the most active oral beta-lactams, amoxicillin and amoxicillin-clavulanate, have predicted efficacy against all penicillin-susceptible and -intermediate pneumococci, as well as against most penicillin-resistant strains, at amoxicillin doses of 45-90 mg/kg per day in children and 1.75-4.0 g/day in adults. These predictions are supported by evidence from animal studies of bacteriologic efficacy. The use of PK/PD parameters to predict bacterial eradication therefore allows an evidence-based approach to the selection of appropriate antimicrobial therapy.

Current status of bacterial resistance in the otolaryngology field: results from the Second Nationwide Survey in Japan

The study reported here was a nationwide assessment of otitis media (466 patients with acute suppurative otitis media and 476 with chronic suppurative otitis media), sinusitis (447 with acute sinusitis and 426 with chronic sinusitis), acute tonsillitis (724 patients), and peritonsillar abscess (141 patients) performed between November 1998 and March 1999. Eighty university hospitals, 79 affiliated hospitals, and 103 general practitioners participated. Methicillin-resistant Staphylococcus aureus(MRSA) comprised 15.6% of the 786 isolated strains of S. aureus. MRSA was frequently detected in patients with suppurative otitis media, but was uncommon in those with acute tonsillitis or peritonsillar abscess, and it was more common in those who had already been treated than in those who had not, with a significant difference between the groups. Vancomycin (VCM) showed the highest antimicrobial activity against MRSA and no VCM resistance was detected. Penicillin-sensitive Streptococcus pneumoniae(PSSP), penicillin-intermediate-resistant S. pneumoniae (PISP), and penicillin-resistant S. pneumoniae (PRSP) accounted for 49.6%, 28.5%, and 21.9% of the 228 isolated strains of S. pneumoniae, respectively. PISP and PRSP were frequently detected in children aged 5 years or younger. beta-Lactamase was produced by 96 of the 100 strains (96%) of Moraxella (Branhamella) catarrhalis. The 281 strains of Haemophilus influenzae isolated consisted of 199 beta-lactamase-negative, ampicillin-sensitive (BLNASe) strains (70.8%), 65 beta-lactamase-negative ampicillin-resistant (BLNAR) strains (23.1%), and 17 beta-lactamase-producing strains (6.0%). BLNAR strains were frequently detected in pretreated patients. Of these 281 strains of H. influenzae, 214 had nontypable capsules. In conclusion, the major bacterial species showed resistance to beta-lactams, indicating that care should be taken when selecting an appropriate antimicrobial agent.

Differences in nasopharyngeal bacterial flora in children with nonsevere recurrent acute otitis media and chronic otitis media with effusion: implications for management

BACKGROUND

The interactions between nasopharyngeal flora and the individual entities covered by the broad term otitis media have not been completely elucidated. We investigated in infants and children ages 6 months to 7 years with nonsevere recurrent acute otitis media (rAOM) or with chronic otitis media with effusion (cOME): (1) the nasopharyngeal carriage rate and bacterial density of respiratory pathogens and alpha-hemolytic streptococci in comparison with healthy children; (2) the resistance pattern of respiratory pathogens; and (3) the relationship between the type of nasopharyngeal colonization and long term outcome.

METHODS

Nasopharyngeal cultures were obtained from 85 children with rAOM,113 children with cOME and 55 controls. A semiquantitative analysis was used in the reading of cultures. A 12-week follow-up without treatment was planned.

RESULTS

The carrier rate of respiratory pathogens was significantly greater in cOME (70%) than in rAOM (45%) (P = 0.0006) or controls (31%) (P < 0.0001). Similarly colonization density was significantly greater in cOME than in rAOM. The carriage rate and the colonization density of alpha-hemolytic streptococci were significantly lower in rAOM than in cOME or controls. The incidence of resistant (R) strains was greater in rAOM (Streptococcus pneumoniae penicillin-R, 24%; macrolide-R, 64%; Haemophilus influenzae amoxicillin-R, 24%) compared with cOME (S. pneumoniae penicillin-R,18%; macrolide-R, 44%; H. influenzae amoxicillin-R, 5%) or controls (S. pneumoniae penicillin-R, 8%; macrolide-R, 23%; H. influenzae amoxicillin-R, 10%). During the follow-up period persistence of OME and occurrence of AOM were greater among carriers of respiratory pathogens at baseline.

CONCLUSIONS

There are substantial differences in nasopharyngeal flora between children with nonsevere rAOM and children with cOME. The results of nasopharyngeal cultures should be taken into account to avoid treatment with drugs that are ineffective and likely to select resistant organisms.

Antibacterial resistance of community-acquired respiratory tract pathogens recovered from patients in Latin America: results from the PROTEKT surveillance study (1999-2000)

PROTEKT (Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin) is a global surveillance study established in 1999 to monitor antibacterial resistance of respiratory tract organisms. Thirteen centers from Argentina, Brazil and Mexico participated during 1999-2000; they collected 1806 isolates (Streptococcus pneumoniae 518, Haemophilus influenzae 520, Moraxella catarrhalis 140, Staphylococcus aureus 351, S. pyogenes 277). Overall, 218 (42.1%) of the S. pneumoniae isolates had reduced susceptibility to penicillin, 79 (15.3%) were penicillin-resistant and 79 (15.3%) were erythromycin-resistant. Mexico had the highest prevalence of penicillin (76.5%) and erythromycin (31.2%) resistance. Of 77 erythromycin-resistant S. pneumoniae tested for resistance genotype, 43 possessed mef(A), 33 possessed erm(B) and 1 possessed both erm(B) and mef(A) mechanism. All S. pneumoniae isolates were fully susceptible to telithromycin, linezolid, teicoplanin and vancomycin. Among H. influenzae isolates, 88 (16.9%) produced beta-lactamase, ranging from 11% (Brazil) to 24.5% (Mexico). Among M. catarrhalis isolates, 138 (98.6%) produced beta-lactamase. Twenty-four (8.7%) of the S. pyogenes isolates were erythromycin-resistant; resistance being attributable to mefA (n=18), ermTR (n=5) and ermB (n=1). All H. influenzae, M. catarrhalis and S. pyogenes were fully susceptible to telithromycin. Methicillin resistance was found in 26.5% of the S. aureus isolates (Argentina 15%; Mexico 20%; Brazil 31.3%). Telithromycin was effective against 97.7% of methicillin-susceptible isolates. PROTEKT confirms that antibacterial resistance is an emerging problem in Latin America. The previously reported high levels of pneumococcal resistance to the beta-lactam and macrolides were exceeded. New agents that do not induce resistance or that exert low selective pressure, e.g. telithromycin, are essential to safeguard future antibacterial efficacy.

Activity of nine oral agents against gram-positive and gram-negative bacteria encountered in community-acquired infections: use of pharmacokinetic/pharmacodynamic breakpoints in the comparative assessment of beta-lactam and macrolide antimicrobial agents

BACKGROUND

The application of pharmacokinetic (PK) and pharmacodynamic (PD) data in conjunction with minimum inhibitory concentrations (MICs) of antibacterial agents has been shown to allow for improved selection and appropriate dosing of antimicrobial agents for specific infections, increasing the likelihood of bacteriologic cure and, through this, reducing the risk for the development of resistant organisms.

OBJECTIVES

This study was undertaken to provide data on current levels of resistance among common community-acquired bacterial species to 7 betalactam antimicrobial agents (including the combination product amoxicillin/clavulanate), azithromycin, and clarithromycin, determined through application of the PK/PD breakpoints based on time-above-MIC for the beta-lactams and the nonazalide macrolide clarithromycin, and on 24-hour serum area under the curve divided by MIC for the azalide macrolide azithromycin.

METHODS

The antimicrobial products tested were amoxicillin/clavylanate, cefpodoxime, cefdinir, cefditoren, cefprozil, cefuroxime, cefixime, azithromycin, and clarithromycin. The bacterial species comprised 70 penicillin-susceptible, 68 penicillin-intermediate, and 69 penicillin-resistant strains of Streptococcus pneumoniae; 46 beta-lactamase-positive and 54 beta-lactamase-negative strains of Haemophilus influenzae; 49 strains of Moraxella catarrhalis; and 100 methicillin-sensitive strains of Staphylococcus aureus (MSSA). Strains were isolated from clinical specimens obtained from outpatient-acquired infections in 1 clinical center in the Northeast and 1 in the north-central area of the United States within the past 2 years. National Committee for Clinical Laboratory Standards microdilution MIC methodology was used. PK/PD breakpoints were obtained from previously published studies and were based on blood values.

RESULTS

Amoxicillin/clavulanate was the product to which the greatest percentage of susceptible, intermediate, and resistant strains of pneumococci were sensitive at the PK/PD breakpoint, followed by cefditoren, cefpodoxime, cefuroxime, cefdinir, and cefprozil. None of the cephalosporins were active against penicillin-resistant pneumococci. Cefditoren and cefpodozime were the agents to which the greatest percentage of beta-lactamase-positive and beta-lactamase-negative strains of H influenzae were sensitive, followed by amoxicillin/clavulanate, cefdinir, and cefuroxime. Cefprozil was inactive against H influenzae. All of the beta-lactam products were active against M catarrhalis. All but cefpodoxime, cefditoren, and cefixime were active against MSSA.

CONCLUSIONS

In this study, based on PK/PD breakpoints, amoxicillin/clavulanate had the best overall activity of the 9 antimicrobial products tested. Cefpodoxime and cefditoren were active against >or=90% of strains of penicillin-susceptible and penicillin-intermediate pneumococci, H influenzae, and M catarrhalis. The macrolides azithromycin and clarithromycin were active against penicillin-susceptible and penicillin-intermediate pneumococci and M catarrhalis; they were inactive against H influenzae and penicillin-resistant pneumococci.

[Alexander Project--5 years in Poland]

The aim of the Alexander Project is to monitor resistance and its trends among the most common bacterial pathogens responsible for community-acquired lower respiratory tract infections and to compare the results obtained between different countries. In Poland, from 1996 to 2000 the percentage of Streptococcus pneumoniae isolates non-susceptible to penicillin was 14.1%. Most often decreased susceptibility to penicillin co-existed with resistance to other classes of antibiotics (multi-drug resistance). The biggest number of pneumococci were resistant to co-trimoxazole (35.2%) and doxycycline (33.6%). Of Haemophilus influenzae isolates, 5.3% produced beta-lactamases. All H. influenzae isolates were susceptible to amoxicillin/clavulanic acid and 3rd-generation cephalosporins. Many isolates of this species were resistant to co-trimoxazole (19.1%). The results of the Alexander Project provide crucial data for guiding national recommendations for empirical treatment of respiratory tract infections.

Resistance issues and community-acquired respiratory infections

Antimicrobial resistance, associated with both excessive and inappropriate use of antimicrobial agents, is a global problem. It is a particular problem in the management of community-acquired respiratory infections, which most often result in the use of antimicrobial therapy. Infections caused by resistant and multiresistant pathogens may also result in high hospitalization rates, long lengths of stay, severe illness, and high mortality, all of which have a great impact on health care costs. The Tracking Resistance in the United States Today (TRUST) Program, the largest longitudinal continuous-surveillance program of its kind, has been conducted every year since 1996 and tracks consecutive respiratory seasons on a year-to-year basis to monitor resistance patterns of respiratory pathogens. This article discusses some of the findings of the TRUST Program, particularly trends in Streptococcus pneumoniae resistance.

Surveillance of resistance in bacteria causing community-acquired respiratory tract infections

Bacterial resistance to antibiotics in community-acquired respiratory tract infections is a serious problem and is increasing in prevalence world-wide at an alarming rate. Streptococcus pneumoniae, one of the main organisms implicated in respiratory tract infections, has developed multiple resistance mechanisms to combat the effects of most commonly used classes of antibiotics, particularly the beta-lactams (penicillin, aminopenicillins and cephalosporins) and macrolides. Furthermore, multidrug-resistant strains of S. pneumoniae have spread to all regions of the world, often via resistant genetic clones. A similar spread of resistance has been reported for other major respiratory tract pathogens, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes. To develop and support resistance control strategies it is imperative to obtain accurate data on the prevalence, geographic distribution and antibiotic susceptibility of respiratory tract pathogens and how this relates to antibiotic prescribing patterns. In recent years, significant progress has been made in developing longitudinal national and international surveillance programs to monitor antibiotic resistance, such that the prevalence of resistance and underlying trends over time are now well documented for most parts of Europe, and many parts of Asia and the Americas. However, resistance surveillance data from parts of the developing world (regions of Central America, Africa, Asia and Central/Eastern Europe) remain poor. The quantity and quality of surveillance data is very heterogeneous; thus there is a clear need to standardize or validate the data collection, analysis and interpretative criteria used across studies. If disseminated effectively these data can be used to guide empiric antibiotic therapy, and to support-and monitor the impact of-interventions on antibiotic resistance.

2D-QSAR in hydroxamic acid derivatives as peptide deformylase inhibitors and antibacterial agents

Peptide deformylase catalyzes the removal of N-formyl group from the N-formylmethionine of ribosome synthesized polypeptide in eubacteria. Quantitative structure-activity relationship (QSAR) studies have been carried out in a series of beta-sulfonyl and beta-sulfinyl hydroxamic acid derivatives for their PDF enzyme inhibitory and antibacterial activities against Escherichia coli DC2 and Moraxella catarrhalis RA21 which demonstrate that the PDF inhibitory activity in cell free and whole cell system increases with increase in molar refractivity and hydrophobicity. The comparison of the QSARs between the cell free and whole cell system indicate that the active binding sites in PDF isolated from E. coli and in M. catarrhalis RA21 are similar and the whole cell antibacterial activity is mainly due to the inhibition of PDF. Apart from this the QSARs on some matrixmetelloproteins (COL-1, COL-3, MAT and HME) and natural endopeptidase (NEP) indicate the possibilities of introducing selectivity in these hydroxamic acid derivatives for their PDF inhibitory activity.

Dynamics of nasopharyngeal colonization by potential respiratory pathogens

Studies have shown that colonization of the nasopharynx by potential respiratory pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis is established early in childhood, although rates vary greatly according to locality, sampling frequency, individual and social factors. Factors influencing colonization and elimination are not as yet fully understood, but adhesion to mucosal receptors and immune responses are implicated in addition to bacterial properties and colonization resistance dynamics. Colonization in children and adults has been intensively studied in various localities. Potential pathogens are more likely to colonize the nasopharynx of children prone to recurrent otitis media, where impaired local immunity and repeated exposure to respiratory pathogens are additional risk factors. Adults with chronic respiratory tract disease also have higher carriage rates. The factors contributing to increased risk of carriage of potential respiratory pathogens, as well as to clinical infection and antimicrobial resistance, are summarized in this review.

[In vitro activity of moxifloxacin against respiratory pathogens in Latin America]

We compared the in vitro activity of moxifloxacin, levofloxacin and six other antibiotics frequently used in respiratory tract infections, against 1563 Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Haemophilus influenzae and Moraxella catarrhalis clinical isolates from 21 centers in 10 Latin American countries from March 2000 to April 2001. Moxifloxacin was the most active compound against all the species included. Moxifloxacin was 2- to 4-fold more active than levofloxacin against Gram-positive bacteria. This difference was much higher against levofloxacin-resistant S. pneumoniae isolates (MIC: 0.5 mg/l vs 8 mg/l). The activity of moxifloxacin against H. influenzae and M. catarrhalis was similar to levofloxacin; all the isolates were inhibited at < or = 1 mg/l concentrations of moxifloxacin and levofloxacin.

Activity of oral beta-lactam antimicrobial agents versus respiratory tract isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the era of antibiotic resistance

The management of outpatient respiratory tract infections with oral beta-lactam antimicrobial agents has been complicated by the emergence of beta-lactamase-producing strains of Haemophilus influenzae and Moraxella catarrhalis and isolates of Streptococcus pneumoniae that express varying levels of beta-lactam resistance because of altered penicillin-binding proteins. There is no question that all 3 of these important respiratory tract pathogens have changed conspicuously in the context of decreased activity of beta-lactam antimicrobial agents. The question arises, what does this change mean from a clinical perspective? In this review, the in vitro activity of various oral beta-lactam antimicrobial agents versus contemporary isolates of H influenzae, M catarrhalis, and S pneumoniae will be compared. The approach that is used in defining organisms as being susceptible or resistant to beta-lactam antimicrobial agents will be elucidated. Finally, an effort will be made to assess the ramifications of beta-lactam resistance for therapeutic efficacy in patients with respiratory tract infections caused by these 3 bacteria. We conclude that, notwithstanding diminished beta-lactam activity for many clinical isolates of H influenzae, M catarrhalis, and S pneumoniae, certain agents remain effective in treating outpatient respiratory tract infections.

Comparison of the in vitro activities of several new fluoroquinolones against respiratory pathogens and their abilities to select fluoroquinolone resistance

In this study the in vitro activities and pharmacodynamic properties of moxifloxacin, levofloxacin, gatifloxacin and gemifloxacin were compared on recently isolated respiratory pathogens and strains of Streptococcus pneumoniae with known mechanisms of fluoroquinolone resistance. In addition, the resistance selection frequencies of moxifloxacin and levofloxacin on three recently isolated respiratory pathogens and four strains of S. pneumoniae with known mechanisms of fluoroquinolone resistance were investigated. The four fluoroquinolones had similar activities against both Moraxella catarrhalis (MIC(90)s 0.015-0.06 mg/L) and Haemophilus influenzae (MIC(90)s 0.008-0.03 mg/L). More marked differences in activity were noted with S. pneumoniae, with MIC(90)s of 0.25, 1, 0.5 and 0.03 mg/L for moxifloxacin, levofloxacin, gatifloxacin and gemifloxacin, respectively. With the S. pneumoniae strains, the four fluoroquinolones exhibited similar concentration-dependent time-kill kinetics. The resistance selection frequencies of levofloxacin were higher than those of moxifloxacin at concentrations equivalent to those at the end of the dosing interval. Therefore moxifloxacin may have less of an impact on the development of resistance than levofloxacin.

In vitro activity of ertapenem against common clinical isolates in relation to human pharmacokinetics

The in vitro activity of ertapenem against bacterial pathogens isolated from patients with moderate to severe complicated intra-abdominal, complicated skin/skin structure, acute pelvic, or complicated urinary tract infection or community acquired pneumonia was compared to ceftriaxone and piperacillin-tazobactam and related to known plasma concentrations of the three agents. Ertapenem was more potent against methicillin-susceptible Staphylococcus aureus (MSSA) than ceftriaxone and piperacillin-tazobactam and was more potent and more active than both of these agents against Enterobacteriaceae and anaerobes. Piperacillin-tazobactam was the most active agent against enterococci and Pseudomonas aeruginosa. All isolates of Enterobacteriaceae (n=1088), Streptococcus pyogenes (n=37), Streptococcus agalactiae (n=48), MSSA (n=187), Haemophilus influenzae (n=59), and Moraxella catarrhalis (n=9) were susceptible to ertapenem; < 1% of 1284 anaerobes and only 1 of 113 Streptococcus pneumoniae (a penicillin-resistant isolate) were resistant to ertapenem. The MIC value at which 90% of all Enterobacteriaceae, streptococci, MSSA, H. influenzae, M. catarrhalis, and anaerobes were inhibited (MIC90) was < or = 1 microg/ml and below the mean plasma concentration of total ertapenem following a 1 g intravenous infusion for at least 24 hours, i.e., the entire recommended dosing interval, and below the free drug concentration for at least 8 h.

The Italian Epidemiological Survey 1997-1999. Antimicrobial susceptibility data of Haemophilus influenzae, Haemophilus parainfluenzae and Moraxella catarrhalis in Italy

The Italian Epidemiological Survey began a surveillance study with the aim of monitoring the antimicrobial resistance of respiratory pathogens. From 1997 to 1999, 2028 strains of Haemophilus influenzae and 523 strains of Haemophilus parainfluenzae were collected from 59 Clinical Microbiology Laboratories distributed throughout Italy. In 1998, the study was extended to include Moraxella catarrhalis and a total of 360 isolates were collected. There was a significant increase in the beta-lactamase production both for H. influenzae (from 5% in 1997 to 16% in 1999) and for H. parainfluenzae (from 5% in 1997 to 22% in 1999). Beta-lactamase production in M. catarrhalis was 84% in 1998 and 87% in 1999. Beta-lactamase production affected the susceptibility to unprotected penicillins (87% in H. influenzae, 85% in H. parainfluenzae and 34% in M. catarrhalis), and in part the susceptibility to cefaclor (about 98%). Amoxycillin/clavulanate, cefixime, ceftriaxone and ciprofloxacin were active against all strains of H. influenzae, H. parainfluenzae and M. catarrhalis.

[Antimicrobial susceptibility and beta-lactamase types among clinical isolates during January and February 2000 in the Kinki area of Japan]

We studied antimicrobial susceptibility and beta-lactamase types among clinical isolates in the Kinki area of Japan. Eight hundreds isolates of eight organisms were collected by seven medical institutions during January and February 2000. The rates of beta-lactamase producing by using the chromogenic nitrocephin test were 68.0% against Staphylococcus aureus isolates, 6.0% against Haemophilus influenzae isolates, 98.0% against Moraxella catarrhalis isolates. The rate of beta-lactamase negative ampicillin-resistant H. influenzae was 4.0% (4 out of 100). The result of beta-lactamase producing by using the acid-metric method were as follows the penicillinase and cephalosporinase: 27.0% and 37.0% against Escherichia coli isolates, 37.0% and 1.0% against Klebsiella pneumoniae isolates, 21.8% and 100% against Enterobacter cloacae isolates, 24.2% and 96.0% against Serratia marcescens isolates, 7.0% and 22.0% against Pseudomonas aeruginosa isolates. We identified beta-lactamase type of each isolate detected by polymerase chain reaction: SHV-derived extended-spectrum beta-lactamase (ESBLs) (1 isolate of E. coli and 1 isolate of K. pneumoniae), CTX-M-1-derived ESBLs (1 isolate of K. pneumoniae, 1 of E. cloacae and 4 of S. marcescens), and IMP-1-derived metallo beta-lactamases (2 isolates of S. marcescens).

[Antimicrobial susceptibility and beta-lactamase producibility of bacteria clinically isolated during the period from December 1999 to February 2000]

Antimicrobial susceptibility and beta-lactamase producibility were tested in 848 clinical strains collected at 8 hospitals in Kanagawa prefecture during the period from December 1999 to February 2000. Positive rates of beta-lactamase used the nitrocefin method (Cefinase) were 21.9% of Staphylococcus aureus, 10.0% of Haemophilus influenzae, and 99.0% of Moraxella catarrhalis. Furthermore, on the acidometric method (P/Case test) penicillinase (PCase), cephalosporinase (CEPase), and both of PCase and CEPase were found to be positive in 19.0%, 16.0%, and 16.0% for Escherichia coli, 6.2/0/3.1% for Klebsiella pneumoniae, 0/66.3/26.5% for Enterobacter cloacae, 2.8/57.7/15.5% for Serratia marcescens, and 4.0/15.0/22.0% for Pseudomonas aeruginosa, respectively. Based on the assessment of minimal inhibitory concentrations (MICs) of antibacterial agents among beta-lactamase producing strains, there were 5 strains (4 strains of K. pneumoniae and 1 strain of E. coli) that may be ESBLs producing bacteria out of a total of 466 strains of Enterobacteriaceae and P. aeruginosa. During this process, 1 strain of class-B beta-lactamase-producing E. cloacae was isolated. MRSA were found in 79.2% of S. aureus, and BLNAR were found in 8.9% of H. influenzae.

[Drug sensitivity and beta-lactamase producibility of various types of bacteria clinically isolated during the period from December 1999 to February 2000]

beta-Lactamase activity and drug sensitivity were measured in 744 strains from 8 species of bacteria isolated at medical institutions in Chikugo District of Fukuoka Prefecture during the period from December 1999 to February 2000. Nitrocefin test revealed that beta-lactamase was positive in 48% of S. aureus, 7% of H. influenzae, and 92% of M. catarrhalis, and acidometry revealed that penicillinase/cephalosporinase were positive in 13%/14% of E. coli, 22%/8% of K. pneumoniae, 47%/97% of E. cloacae, 3%/65% of S. marcescens, and 10%/36% of P. aeruginosa. Based on the assessment of the MIC values of various types of antibacterial drugs for beta-lactamase-producing strains, there were 11 strains (1 strain of K. pneumonia, 6 strains of E. cloacae, and 4 strains of P. aeruginosa) of class-B beta-lactamase-producing bacteria out of a total of 496 strains of Enterobacteriaceae and Pseudomonas aeruginosa. The results of PCR analysis suggested that 1 strain of K. pneumonia, 1 strain of E. cloacae, and 4 strains of P. aeruginosa produced metallo-beta-lactamase. There was no strain (E. coli and K. pneumoniae) of ESBL-producing bacteria. BLNAR strains, on the other hand, were found in 9% (9/100) of H. influenzae.

[Antimicrobial susceptibility and beta-lactamase productivity of recent clinical isolates during the period between December 1999 and February 2000]

Antimicrobial susceptibility testings of 24 antimicrobial agents against 605 clinical strains belonging to 10 species were carried out according to the micro-broth dilution method of NCCLS M7-A4. The productivity of beta-lactamase was also determined against them isolated at 8 medical facilities in Nagano prefecture, Japan during the period between December 1999 and February 2000. When applied the nitrocefin method, beta-lactamase productivity was demonstrated to be positive for 89.2% of 74 S. aureus, 4.3% of 94 H. influenzae, and 100% of 69 M. (B.) catarrhalis isolates. On the other hand, when used the acidometry method, penicillinase/cephalosporinase were found to be positive for 21.2%/9.6% of 52 E. coli, 29.0%/3.2% of 31 K. pneumoniae, 53.2%/100% of 47 E. cloacae, 0%/11.1% of 99 S. marcescens, and 25.9%/55.6% of 54 P. aeruginosa isolates, respectively. Among the beta-lactamase-producers including P. aeruginosa isolates, only 2 E. coli isolates were found to be ESBL-producers. Besides, 9.6% (9/94) of H. influenzae isolates were proved to be BLNAR strains.

[Beta-lactamase activity and susceptibilities to antibiotics among some species of bacteria isolated from medical institution between December 1999 and February 2000]

We studied the beta-lactamase activity and susceptibilities to antibiotics in 604 strains among 10 species of bacteria isolated from 10 medical institutions in Tottori and Shimane Prefectures between December 1999 and February 2000. beta-Lactamase activity was measured by the nitrocefin test and penicillinase/cephalosporinase activities were measured by acidometry. beta-Lactamase activity was detected in 72.1% of S. aureus, 18.8% of H. influenzae, and 96.3% of M. catarrhalis. Penicillinase/cephalosporinase activities were detected in 17.8%/22.2% of E. coli, 9.7%/0.0% of K. pneumoniae, 18.6%/95.3% of E. cloacae, 12.7%/79.4% of S. marcescens, and 7.1%/31.8% of P. aeruginosa. Three of 72 strains (4.2%) of K. pneumoniae and 5 of 90 strains (5.6%) of E. coli were assessed as ESBL-producing bacteria using the NCCLS proposed screening method based on routine susceptibility testing results. BLNAR were detected in 13 of 69 strains (18.8%) of H. influenzae.

[Antimicrobial susceptibility and prevalence of beta-lactamase producing clinical isolates in southern Kyushu. The results of collaborative study from 1999 to 2000]

The positivity of beta-lactamase and antimicrobial susceptibility were determined in a total of 1,358 clinical isolates at 15 hospitals and clinics in four prefectures in southern Kyushu (Okinawa, Miyazaki, Kagoshima and Kumamoto) during the period from December 1999 to February 2000. The isolates collected comprised of 176 strains of S. aureus, 203 of H. influenzae, 102 of M. catarrhalis, 206 of E. coli, 153 of K. pneumoniae, 99 of E. cloacae, 95 of S. marcescens, 201 of P. aeruginosa, 79 of E. faecalis, and 44 of E. faecium. The frequency of CPDX resistance among E. coli in particular varied geographically, and was found to be higher in Kumamoto and Kagoshima. The strains of K. pneumoniae and E. cloacae resistant to common antimicrobial agents were particularly found in Kagoshima, and one strain of IPM-resistant E. cloacae was isolated in Miyazaki. Also, the geographical difference in the frequency of LVFX resistance among the isolates of E. cloacae was noted, the results indicating the higher prevalence in Okinawa and Kagoshima. Resistant isolates of P. aeruginosa were less common in Kagoshima, and four isolates of P. aeruginosa from Miyazaki were found to be resistant to CAZ and IPM. None of the isolates of S. aureus and Enterococcus spp. was resistant to VCM or TEIC at all. The isolates of E. faecalis resistant at high-level GM (500 micrograms/ml) and SM (1,000 micrograms/ml) were found in 27.8% and 22.8%, and those of E. faecium were 6.8% and 38.6%, respectively. Overall, the ratio of MRSA among S. aureus was 67.6%, and three isolates were resistant to ABK with no less than 8 micrograms/ml of MIC. The frequency of BLNAR (beta-lactamase-negative, ampicillin resistant) among H. influenzae isolated in Okinawa was markedly higher (isolation ratio, 37.9%) when compared with other prefectures, and the isolates of BLPACR (beta-lactamase-positive, AMPC/CVA resistant) were found only in Okinawa with a ratio of 41.6%. A total of 18 strains of ESBL defined by the NCCLS criteria (M100-S11) were isolated, eight strains of K. pneumoniae and 10 strains of E. coli. Of 18 isolates of ESBL, 13 were from Kagoshima and the remaining five were from Kumamoto.

The PROTEKT surveillance study: antimicrobial susceptibility of Haemophilus influenzae and Moraxella catarrhalis from community-acquired respiratory tract infections

This paper presents data relating to Haemophilus influenzae and Moraxella catarrhalis from PROTEKT (1999-2000), a surveillance study that examined the susceptibility of respiratory pathogens to current and new antibacterials. Beta-lactamase production is the principal mechanism of resistance to ampicillin and other beta-lactam antibacterials in H. influenzae and M. catarrhalis. The PROTEKT study showed that globally, the prevalence of beta-lactamase production in H. influenzae varied considerably: of 2948 isolates, 489 (16.6%) were beta-lactamase-positive [range: 1.8% (Italy) to 65% (South Korea)]. Beta-lactamase-negative, ampicillin-resistant (BLNAR) strains of H. influenzae were uncommon (<0.1%) but their very detection highlights the need for continued vigilance. Overall, few isolates of H. influenzae showed resistance to either macrolides or telithromycin. The emergence of clarithromycin-resistant strains is worrying, however, as such isolates may also show resistance to other macrolides. There was a geographical correlation between beta-lactamase production and the prevalence of resistance to chloramphenicol and tetracycline among the H. influenzae isolates. Of 1131 M. catarrhalis isolates, 92% were beta-lactamase-positive. Most isolates, however, were fully susceptible to nearly all the antibacterials tested, except ampicillin. The most active were ciprofloxacin and levofloxacin (both having MIC(90) values of 0.03 mg/L), moxifloxacin (MIC(90) 0.06 mg/L), azithromycin (MIC(90) < or = 0.06 mg/L) and telithromycin (MIC(90) 0.12 mg/L). Overall, there were no concerns in terms of resistance to fluoroquinolones for both H. influenzae and M. catarrhalis. In summary, the PROTEKT surveillance study confirmed the problem of widespread prevalence of beta-lactamase-producing strains of H. influenzae and M. catarrhalis, although these pathogens generally remain susceptible to macrolides, fluoroquinolones and the new ketolide telithromycin.