Pharmacokinetic/pharmacodynamic predictors of time to clinical resolution in patients with acute bacterial exacerbations of chronic bronchitis treated with a fluoroquinolone

Forty nine subjects with acute bacterial exacerbations of chronic bronchitis (ABECB) treated with grepafloxacin were evaluated for parameters predictive of clinical outcome. Signs and symptoms associated with ABECB were serially collected and evaluated for changes. Coughs per day, sputum volume and the percentage of sputum neutrophils were associated with clinical outcome. A by groups analysis, based on clinical success was performed using Cox regression analysis to determine factors associated with time to clinical success and time to reduction in sputum volume, coughs per day and sputum neutrophil percent. Factors evaluated included AUIC (AUC/MIC), isolate species, years and type of underlying lung disease, alcohol use, smoking history and number of ABECB within the previous 12 months. AUIC<276 (mg h/l)/mg/l (P<0.03) and or the presence of mild bronchiectasis (P<0.01) were associated with longer time to clinical success. In addition a relationship was found between AUIC>212 (mg h/l)/mg/l (P<0.01) and AUIC>576 (mg h/l)/mg/l (P<0.02) and decreasing days to sputum volume reduction and coughs per day, respectively. A diagnosis of mild bronchiectasis prolonged the time to reduce coughs per day (P<0.03) and neutrophil percentage (P<0.01). Patients with mild bronchiectasis were found to have an increase in the time to clinical success, coughs per day improvement and sputum neutrophil percent improvement. AUIC is an important PK/PD parameter predictive of successful outcome in ABECB, even in subjects with mild bronchiectasis. Grepafloxicin has been withdrawn from sale since these studies were carried out. This work is published to illustrate the relationship between pharmacodynamics and clinical efficacy and the use of AUIC as a valuable predictive parameter for fluoroquinolones.

A single intramuscular dose of ceftriaxone changes nasopharyngeal bacterial flora in children with acute otitis media

The increasing prevalence of drug-resistant bacteria is attributed to the extensive use of antibiotics, which causes selective pressure on the nasopharyngeal bacterial flora. Shortened courses of antibiotics have been proposed to decrease the development of resistant strains. We determined the effect of a single intramuscular dose of ceftriaxone (50 mg/kg) on the nasopharyngeal bacterial flora in 167 children (median age 13 mo) with acute otitis media. Nasopharyngeal samples for bacterial culture were obtained before and 5 d after treatment with ceftriaxone. Before treatment, Moraxella catarrhalis was isolated in 99 (59%) children, Streptococcus pneumoniae in 87 (52%), and Haemophilus influenzae in 53 (32%). After treatment, M. catarrhalis was found in 62 (37%) children, which constitutes a 37% decrease in the colonization rate by this pathogen (p < 0.001). S. pneumoniae was isolated in 50 (30%; 43% decrease) and H. influenzae in 17 (10%; 68% decrease) children after treatment (p < 0.001 for both). Before treatment, 60% of pneumococcal isolates were sensitive to penicillin, 26% were of intermediate susceptibility, and 14% were penicillin-resistant. Eradication of S. pneumoniae occurred mainly in children with penicillin-sensitive isolates. As a consequence, only 24% of pneumococcal isolates that remained after treatment were sensitive to penicillin, 59% were penicillin-intermediate, and 16% were penicillin-resistant. A single dose of ceftriaxone resulted in significant changes in the nasopharyngeal bacterial flora, increasing the relative prevalence of pneumococcal strains with decreased susceptibility to penicillin.

In vitro activity of moxifloxacin(BAY 12-8039) against respiratory tract pathogens from six Latin-American countries

The in vitro antibacterial activity of moxifloxacin (BAY 12-8039) was evaluated against 636 isolates of respiratory tract pathogens. The isolates were collected from July 1997 to August 1998 in the frame of a multinational Latin American study. E-test strips calibrated to read moxifloxacin MIC ranges from 0.002 to 32 microg/ml were used in susceptibility testing. Weekly quality control tests in each laboratory ensured reproducibility. Laboratories from Argentina, Brazil, Chile, Colombia, Mexico and Uruguay participated. MIC(90) for moxifloxacin were as follows: Streptococcus pneumoniae (304 isolates) 0.25 microg/ml, Haemophilus influenzae (135 isolates) 0.125 microg/ ml, Streptococcus pyogenes (66 isolates) 0.25 microg/ml, Moraxella catarrhalis (62 isolates) 0. 25 microg/ml and methicillin-sensitive Staphylococcus aureus (69 isolates) 0.25 microg/ml. These results agreed with reports from other areas. Moxifloxacin showed excellent activity against respiratory pathogens from participant countries.

Epidemiological survey of bacterial resistance in upper respiratory tract infections in italy

The vast majority of infections in the upper airways are caused by four bacterial species;, in Italy as elsewhere, antibiotics resistant strains are emerging. Enzymatic resistance to beta-lactams in Haemophilus influenzae is becoming more important and affects 15% of isolates. On the other hand less than 0.3% of H. influenzae strains are fluoroquinolone-resistant. The number of beta-lactamase-producing Moraxella catarrhalis strains in Italy has been thought to be lower than in other countries, but recent studies suggest 90% of strains are positive, a figure similar to figures reported in the international literature. The most recent data estimate high-level resistance to penicillin in pneumococci to be around 5%, but varies greatly in different geographical areas and with the different origins of the isolates. In spite of the low incidence of penicillin-resistant strains, the most recent figures for macrolide-resistance in Streptococcus pneumoniae range from 26.4 to 31.7%. More than 3 years after the dramatic increase in erythromycin-resistant Streptococcus pyogenes, the resistance levels in Italy are still among the highest in the world. Unlike the experience in other countries, resistance is often related not to the active efflux of antibiotic from the bacterial cell but to ribosomal methylation, thus affecting not only 14- and 15-membered macrolides, but also 16-membered compounds and lincosamides.

Treatment of acute otitis media with an antiadhesive oligosaccharide: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Antiadhesive compounds are promising candidates for prevention or treatment of infections. We have investigated the efficacy of such an agent, 3'-sialyllacto-N-neotetraose (NE-1530), given intranasally for prophylaxis of acute otitis media and for effect on nasopharyngeal carriage of bacteria.

METHODS

We did a randomised, double-blind placebo-controlled study at one study site. 507 healthy children were randomly assigned either NE-1530 (n=254) or placebo (253) as intranasal sprays twice daily during 3 months. The children were examined by the study physicians once a month and during illness. Treatment efficacy was estimated from Cox proportional hazards model. A sample of nasopharyngeal secretion was taken at every visit for culture of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Adverse events were recorded in study diaries.

FINDINGS

At least one event of acute otitis media was diagnosed in 108 (43%) of 254 children in the NE-1530 group and in 86 (34%) of 253 children in the placebo group. The efficacy of treatment was negative, -27% (95% CI -68 to 5; p=0.10). The nasopharyngeal carriage of S pneumoniae, H. influenzae, and M. catarrhalis was not affected by treatment, and the adverse event profiles were almost identical for NE-1530 and placebo.

INTERPRETATION

NE-1530 did not have a beneficial effect on the occurrence of acute otitis media or on the nasopharyngeal carriage of bacteria in children.

Benchmarking the in vitro activities of moxifloxacin and comparator agents against recent respiratory isolates from 377 medical centers throughout the United States

To benchmark the activity of moxifloxacin (a newer fluoroquinolone), a U.S. study comprising 16,141 contemporary isolates of Streptococcus pneumoniae (5,640), Haemophilus influenzae (6,583), and Moraxella catarrhalis (3,648) referred from 377 institutions during 1998 is described. For S. pneumoniae the modal MIC and MIC at which 90% of the isolates were inhibited (MIC(90)) for moxifloxacin were 0.12 and 0.25 microg/ml, respectively, independent of susceptibility to other drug classes, geography, or site of infection. Eleven isolates were intermediate or resistant to levofloxacin and grepafloxacin; of these isolates, 1 remained susceptible to sparfloxacin, 2 remained susceptible to moxifloxacin, and 4 remained susceptible to trovafloxacin. All 11 isolates possessed classic mutations in gyrA and/or parC known to confer reduced susceptibility to fluoroquinolones. Four isolates (originating from four separate states) belonging to a multidrug-resistant, fluoroquinolone-resistant clone were identified by pulsed-field gel electrophoresis. For moxifloxacin and trovafloxacin, at least 87% of isolates demonstrated MICs > or =3 twofold concentrations below the susceptibility breakpoints, in contrast to no more than 15% for levofloxacin, grepafloxacin, and sparfloxacin. Of the isolates that were multidrug resistant (7.4%), >98% remained susceptible to moxifloxacin. The modal MIC and MIC(90) for M. catarrhalis (both 0.06 microg/ml) and for H. influenzae (both 0.03 microg/ml) were independent of beta-lactamase production. These data demonstrate the in vitro activity of moxifloxacin and establish a baseline for future studies.

In vitro antimicrobial activity of propolis dry extract

In this study the antibacterial and antifungal properties of propolis, a natural product of bees, have been investigated against different pathogens. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined according to NCCLS standards on 320 strains including Staphylococcus aureus, Group A beta-hemolytic streptococci, Streptococcus pneumoniae, Moraxella catarrhalis, Haemophilus influenzae, Klebsiella pneumoniae, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Candida albicans. Time-kill curves were assessed for susceptible microorganisms, testing 0, 0.5, 1, 2, 4 x MIC for propolis, by counting viable bacteria after 0, 3, 6, 24 hours and viable yeasts after 0, 3, 6, 24 and 48 hours. Propolis showed good antimicrobial activity against most of the isolates, particularly S. pneumoniae, H. influenzae and M. catarrhalis, but not against Enterobacteriaceae. Time-kill curves demonstrated bacteriostatic rather than bactericidal activity of propolis, the latter being evident only at high concentrations.

Prevalence of antimicrobial resistance among respiratory tract isolates in Latin America: results from SENTRY antimicrobial surveillance program (1997-98)

One thousand seventy-three bacterial isolates were collected from patients with community acquired respiratory tract infections (CARTI) in 11 Latin American centers (7 countries) during 1997 and 1998. They were tested against numerous antimicrobial agents by the reference broth microdilution method as part of the ongoing multinational SENTRY Antimicrobial Surveillance Program. Among Streptococcus pneumoniae (553 isolates), approximately 61% were susceptible to penicillin. There was a great variation of the penicillin susceptibility rates among participating countries. The highest susceptibility rates were found in Argentina (76.7%) and Brazil (71.9%), while the lowest rate of penicillin susceptibility was detected in Mexico (33.3%). High level resistance to penicillin and resistance to cefotaxime were observed in nearly 10% of the isolates. The newer quinolones, levofloxacin (MIC(90) 2 microg/mL) and gatifloxacin (MIC90 0.5 microg/mL), were active against 100% of the isolates tested. Among the other non-beta-lactams drugs tested, the rank order of susceptibility against the pneumococci was: chloramphenicol (93.9%)>clindamycin (93.2%)> azithromycin (89.1%) > clarithromycin (88.7%)>tetracycline (78.5%)> trimethoprim/sulfamethoxazole (55.7%). The percentage of Haemophilus influenzae (361 isolates) isolates resistant to amoxicillin was 12. 7% (beta-lactamase positive). Among Moraxella catarrhalis (159 isolates) isolates, only 8.2% were susceptible. Clavulanic acid restored the activity of amoxicillin against both species. Trimethoprim/sulfamethoxazole was active against only 59.5% of H. influenzae, while susceptibility to this compound among M. catarrhalis was 96.1%. All other compounds tested were active against>95% of H. influenzae and M. catarrhalis isolates. These species were susceptible to levofloxacin (MIC90 < or = 0.5 microg/mL for both) and gatifloxacin (MIC90 < or = 0.03 microg/mL for both) with very low MICs. Our results indicate that penicillin resistance rates are particularly high among pneumococci in some countries. The newer fluoroquinolones show an excellent potency and spectrum against pathogens causing community acquired respiratory infections in Latin America.

Resistance in respiratory tract pathogens: an international study 1997-1998

Multiple antibiotic resistance threatens current treatment for community-acquired pneumonia (CAP). This paper presents a summary of resistance data for Streptococcus pneumoniae (6,223 isolates), Haemophilus influenzae (4,016) and Moraxella catarrhalis (1,263) collected from 153 centers throughout Japan, China, UK, Germany, Spain, France, Italy, Brazil and USA. Antiobiotics tested were: beta-lactams (penicillin, ampicillin, co-amoxiclav, cefuroxime, and ceftriaxone), macrolides (azithromycin and clarithromycin), sulphonamide (trimethoprim-sulfamethoxazole), glycopeptide (vancomycin) and fluoroquinolone (levofloxacin). S. pneumoniae with reduced susceptibility to penicillin were predominant in France, Spain and Japan (54-65%), ,beta-lactamase-producing H. influenzae most common in the USA, France and Spain (>25%) and most M. catarrhalis produced beta-lactamase irrespective of origin. S. pneumoniae susceptibility to azithromycin and clarithromycin varied widely. Levofloxacin was active against almost all isolates in all countries and none was resistant to vancomycin. Because of increasing resistance to older drugs, the newer fluoroquinolones have a role in the therapy of CAP and other respiratory infections, although surveillance studies must continue.

Antibiotic medication and bacterial resistance to antibiotics: a survey of children in a Vietnamese community

OBJECTIVE

To investigate antibiotic use and antibiotic susceptibility of respiratory tract pathogens in children aged 1-5 years in Bavi, Vietnam.

METHOD

Nasopharynx and throat specimens were collected from 200 children from randomly selected households in a demographically defined population. Respiratory isolates were tested for antibiotic susceptibility according to the standard disk diffusion method. A questionnaire survey of carers elicited information on type of antibiotic used, duration of treatment, where the antibiotics had been purchased, type of treatment information retained by carers and episodes of illness preceding the study.

RESULTS

82% of the children had at least one symptom of acute respiratory tract infection (ARI) in the 4 weeks prior to the study, and of these 91% were treated with antibiotics. The most commonly used antibiotics were ampicillin (74%), penicillin (12%), amoxicillin (11%), erythromycin (5%), tetracycline (4%) and streptomycin (2%). Ampicillin was used for 3.3 days on average (SD:1.8) and penicillin for 2.6 days (SD:0.7). When deciding which antibiotic to use, 67% of the carers consulted the pharmacy seller, 11% decided themselves and 22% followed the doctor's prescription. The carrier rate of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis was 50%, 39% and 17%, respectively. Isolates from 145 children were susceptibility tested, and 74% were found to carry resistant pathogens. Of the tested isolates, 90% of S. pneumoniae, 68% of H. influenzae and 74% of M. catarrhalis were resistant to at least one antibiotic. The mean number of antibiotics (susceptible strains excluded) to which resistance was found was 2.0 (SD:1.2), 2.5 (SD:1.8) and 2.1 (SD:0.9), respectively. S. pneumoniae and H. influenzae showed high resistance to tetracycline (88% and 32%, respectively), trimethoprim/sulphonamide (32% and 44%), and chloramphenicol (25% and 24%). 23% of S. pneumoniae were erythromycin-resistant and 18% of H. influenzae isolates were resistant to ampicillin. There was a significant difference in ampicillin and penicillin resistance between the group of children previously treated with beta lactam antibiotics and the group of children who did not receive antibiotics.

CONCLUSION

As reported by the carers, children in Bavi are treated with antibiotics frequently. Most antibiotics were obtained without consulting a doctor. High levels of antibiotic resistance and high prevalence of multidrug-resistant strains were found among respiratory pathogens. The existence of a large reservoir of resistance genes among children in low-income countries represents a threat to the success of antibiotic therapy throughout the world. Multi-faceted programmes to improve rational use of antibiotics in Vietnam are urgently needed.

Moraxella catarrhalis endocarditis: case report and review of the literature

A case of bacterial endocarditis caused by Moraxella catarrhalis in an apparently immunocompetent Greek male is presented, which was diagnosed after a 2-month history of low-grade fever of unknown origin. The agent seems to be a rare pathogen, but due to the high mortality rate, it should always be considered in the differential diagnosis of relevant cases. Beta-lactamase production by many strains complicates the choice of antibiotic.

Antimicrobial susceptibility patterns of respiratory pathogens--a global perspective

Antimicrobial resistance among respiratory tract pathogens poses a major challenge for the ongoing use of antimicrobial agents for treating infected patients. Global antimicrobial susceptibility data has documented the existence of widespread resistance issues. Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis constitute the principal community-acquired respiratory tract bacterial pathogens. For H. influenzae, resistance to ampicillin varies from less than 5% in some European countries to greater than 30% in North America and Southeast Asia. For H. influenzae, resistance to trimethoprim/sulfamethoxazole has been shown to range from less than 5% in North America and Europe to greater than 25% in Europe, the Middle East, and India. For M. catarrhalis, 85% to 100% of isolates worldwide are beta-lactamase positive and, therefore, ampicillin and amoxicillin resistant. Penicillin-resistant S. pneumoniae shows considerable variability worldwide ranging from 6% to 80% whereas macrolide resistance among the pneumococci range from 0% to 90%. Clearly, documenting and understanding the emergence, dissemination, and infection with pathogens resistant to antimicrobial agents is essential for developing strategies to deal with this global problem. This article highlights the frequency of antimicrobial resistance among the respiratory pathogens from a global perspective. Also, mechanisms of resistance and factors associated with the emergence, dissemination, and colonization of resistant organisms are discussed.

In vitro comparative dynamics of modified-release clarithromycin and of azithromycin

Antibacterial kinetics of modified-release clarithromycin (CLA) and azithromycin (AZI) against respiratory tract pathogens were compared in relation to their pharmacokinetic profile. The study was carried out in three strains of Streptococcus pneumoniae, group A beta-hemolytic Streptococcus pyogenes, Moraxella catarrhalis and Haemophilus influenzae, respectively, exposed to concentration gradients of CLA and AZI simulating human serum pharmacokinetics after administration of 500 mg p.o. in a single dose. Bactericidal kinetics were assessed by counting the number of survivors before each change in concentration over a period of 36 h. The minimal inhibitory concentrations (MICs) of CLA and AZI were evaluated at time 0 and after 36 h of exposure to antibiotics in the surviving organisms. The results showed that CLA and AZI, in the experimental conditions adopted, had different antibacterial kinetics. Moreover, the addition of the 14-OH metabolite of CLA at the same concentrations reached in human serum exerted a bactericidal effect against two strains of H. influenzae resistant to CLA and AZI. An increase in MICs was observed against S. pyogenes and H. influenzae, with higher values for AZI.

Comparative in vitro activity of older and newer fluoroquinolones against respiratory tract pathogens

The aim of this study was to evaluate the antibacterial activity of older (ciprofloxacin and ofloxacin) and newer (moxifloxacin, grepafloxacin, sparfloxacin and levofloxacin) fluoroquinolones. Minimal inhibitory concentrations (MICs) were determined, according to the NCCLS guidelines, against the following respiratory tract pathogens: penicillin-susceptible and -resistant Streptococcus pneumoniae, beta-lactamase-positive and beta-lactamase-negative Haemophilus influenzae and beta-lactamase-positive Moraxella catarrhalis. In addition, we evaluated the minimal bactericidal concentrations of the same antibiotics against all the pneumococci and the haemophili. Finally, the activity of ciprofloxacin, ofloxacin, sparfloxacin and moxifloxacin against 15 pneumococci were investigated by time-kill analysis. All fluoroquinolones tested exhibited a similar, good activity against H. influenzae and M. catarrhalis. Against S. pneumoniae, irrespective of penicillin susceptibility, moxifloxacin, grepafloxacin, sparfloxacin and levofloxacin exhibited excellent activity, better than ciprofloxacin and ofloxacin. Time-kill analysis showed that 99.9% killing of all strains was obtained after 24 h with moxifloxacin at 2 x MIC, whereas other antimicrobials obtained similar results at 4 x MIC. Moxifloxacin is characterized by an improved activity against respiratory pathogens, including penicillin-resistant and -susceptible S. pneumoniae. Its activity is not influenced by beta-lactamase production. These results suggest that moxifloxacin represents a promising alternative for treatment of respiratory tract infections.

Isolation of Moraxella catarrhalis in patients at King Khalid University Hospital, Riyadh

OBJECTIVE

A retrospective study was carried out to assess the clinical significance of Moraxella catarrhalis (M. catarrhalis) isolated from 32 specimens received from patients seen during a 2 year period.

METHODS

The identity of isolates was confirmed by DNAse production and reduction of nitrate to nitrite. Susceptibility testing and B-lactamase production was carried out for each isolate.

RESULTS

Twenty three of the patients were adults and 9 were children. Twelve (37%) of the isolates were from the sputum of patients aged more than 50 years with a clinical diagnosis of pneumonia, bronchitis or bronchiactesis. Six (18%) had M. catarrhalis isolated from sputum and had underlying cardiac, liver diseases or diabetes mellitus. The organism was isolated from the blood of one patient with pneumonia and one with leukaemia. It was also isolated from patients with sinusitis, conjunctivitis or otitis media. Twenty seven (84%) of the 32 strains produced B-lactamase, resistance to erythromycin and clindamycin was detected in 13% of the isolates. All isolates were susceptible to ciprofloxacin, tetracycline, trimethoprim-sulfamethoxazle, gentamicin, chloramphenicol, polymyxin B and neomycin.

CONCLUSION

This study showed that M. catarrhalis can be an important respiratory tract pathogen in adults and children, able to invade the blood stream of patients with predisposing respiratory conditions and underlying systemic illnesses, as well as immunocompetent patients. Since most strains produce B-lactamase, antibiotic therapy should be guided by in-vitro susceptibility tests.

Activity of gatifloxacin compared to those of seven agents against bacteria recovered from outpatients with respiratory tract infection

The in vitro activity of gatifloxacin and levofloxacin, ciprofloxacin, penicillin, ampicillin, ampicillin-sulbactam, ceftriaxone and clarithromycin was evaluated against 173 S. pneumoniae strains (128, penicillin-susceptible strains; 32, intermediate penicillin- resistant strains and 13, penicillin-resistant strains), 163 H. influenzae strains (128, beta-lactamase non-producer; 35, beta-lactamase producers), 111 M. catarrhalis (9, beta-lactamase non-producer; 102, beta-lactamase producers), 95 Streptococcus pyogenes and 116 S. aureus strains (96, methicillin-susceptible; 20, methicillin-resistant) recovered from outpatients with respiratory tract infection. Based upon the MICs at which 50% and 90% of the isolates were inhibited we concluded that gatifloxacin proved to be the most active antibiotic against respiratory pathogens, including all the penicillin-resistant pneumococci and H. influenzae or M. catarrhalis producing beta-lactamase. Furthermore, their MICs against S. pneumoniae and methicillin-resistant S. aureus were lower than those of levofloxacin and ciprofloxacin.Therefore, this new fluoroquinolone displayed in vitro features that make it suitable for treating community-acquired respiratory tract infections.

Gemifloxacin versus amoxicillin/clavulanate in the treatment of acute exacerbations of chronic bronchitis. The 070 Clinical Study group

Six hundred patients were evaluated in this randomized, double-blind, double-dummy, multicenter, parallel-group study comparing the efficacy and safety of gemifloxacin (320 mg once-daily for 5 days) and amoxicillin/clavulanate (500/125 mg three-times daily for 7 days) for the treatment of acute exacerbations of chronic bronchitis (AECB). Of note, more than 90% of study participants had stage 2 disease at study entry. The two drugs were found to be equally effective, with clinical success rates of 93.6% for gemifloxacin and 93.2% on amoxicillin/clavulanate (95% CI -3.9 to 4.6). Bacteriological success rates favored gemifloxacin (90.9% compared with 79.5% for amoxicillin/clavulanate; 95% CI -3.3 to 26.0); however, this difference was not statistically significant. Gemifloxacin and amoxicillin/clavulanate were both well tolerated. In summary, gemifloxacin was found to be well tolerated and effective for the treatment of AECB, suggesting it is well suited for empirical treatment of this common respiratory condition in the current clinical environment.

Impact of antimicrobial therapy on nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Branhamella catarrhalis in children with respiratory tract infections

We conducted a multicenter prospective study to document changes in nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Branhamella catarrhalis during antibiotic therapy. A cohort of 629 children with respiratory tract infections underwent nasopharyngeal sampling before and after antibiotic treatment. Susceptibility testing, serotyping, arbitrarily primed polymerase chain reaction, and pulsed-field gel electrophoresis were used to compare pretreatment and posttreatment strains of S. pneumoniae. A significant decrease in carriage of all 3 species (especially S. pneumoniae and B. catarrhalis) was recorded. The increase in the proportion of penicillin-resistant pneumococci (PRP; 66% vs. 44%) was due to the decreased carriage of penicillin-susceptible pneumococci (71 of 629 vs. 176 of 629). The risk of PRP carriage in a given child did not increase. None of the children was found to harbor genetically related strains with increased minimum inhibitory concentrations. Given the multiple resistance of PRP, beta-lactam antibiotic therapy also increased the incidence of macrolide-resistant strains, whereas macrolides selected both macrolide- and penicillin-resistant strains.

Antimicrobial resistance in respiratory tract pathogens: results of an international surveillance study

An international surveillance study was performed to assess the resistance patterns among respiratory tract pathogens during the winter of 1997-1998. The pathogens studied included Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. The antibiotics tested included five beta-lactams (penicillin, ampicillin, amoxicillin, amoxicillin-clavulanic acid, cefuroxime axetil and ceftriaxone), two macrolides (azithromycin and clarithromycin), one sulfonamide (trimethoprim-sulfamethoxazole), one glycopeptide (vancomycin) and one fluoroquinolone (levofloxacin). A total of 11,502 isolates were tested from nine countries, using microdilution susceptibility tests as recommended by National Committee for Clinical Laboratory Standards (NCCLS) guidelines. The susceptibility rates varied greatly around the world. Ninety percent of M. catarrhalis isolates produced beta-lactamase, making them resistant to ampicillin. beta-Lactamase production by H. influenzae ranged from 5% in Germany to 34% in the USA (mean 17.5%). Of the S. pneumoniae isolates, 32.8% had some resistance to penicillin, but this ranged greatly from 7.8% in Germany to 66.5% in France. Penicillin resistance in S. pneumoniae was associated with resistance to other beta-lactams, macrolides and sulfonamides, but not to levofloxacin or vancomycin. All isolates of H. influenzae and M. catarrhalis were susceptible to levofloxacin. Results of this study support the conclusion that these three respiratory tract pathogens are becoming more resistant to selected antimicrobials, and that the level of resistance in these isolates to the antimicrobials varies greatly from one country to another.

Epidemiology of resistance to antimicrobial drugs in the major respiratory pathogens circulating in Europe

There is an overwhelming consensus on the fact that Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis represent the prevailing bacterial pathogens of community-acquired lower respiratory tract infections. Their specific incidence as causative agents of the more common syndromes is known to vary even profoundly depending on geographic location, and the same holds true for the rates of resistance to antimicrobial drugs. Europe does not escape the threat posed by the present pandemic spread of penicillin resistance in S. pneumoniae although, as expected, countries like Spain and France are greatly affected, while others including Germany, Italy, The Netherlands and the Scandinavian region are comparatively spared. In several sites multiple resistance has been described in S. pneumoniae and the most affected drugs include penicillin, the macrolides, co-trimoxazole and tetracycline. In H. influenzae synthesis of beta-lactamases the main trait of resistance is expressed. Lack of susceptibility to beta-lactams dictated by a different mechanism remains extremely rare. Considerable variations in the incidence of this characteristic are apparent when European countries are considered. France and Spain are again widely affected, while Germany, The Netherlands and Italy display rates of beta-lactamase-positive H. influenzae of about 10%. M. catarrhalis must be considered generally resistant to non-protected aminopenicillins since over 90% of these organisms produce beta-lactamases.

The evolving threat of antibiotic resistance in Europe: new data from the Alexander Project

The Alexander Project was established in 1992 to examine the antimicrobial susceptibility of community-acquired lower respiratory tract bacterial pathogens to a range of compounds. Since then it has expanded both geographically and in the number of antimicrobial agents tested. Within Europe, the most recent data have confirmed that the prevalence of penicillin resistance among isolates of Streptococcus pneumoniae is high in France and Spain, with both intermediate (MIC 0.12-1 mg/L) and resistant (MIC > or = 2 mg/L) phenotypes, and combined resistance rates of >50%. Macrolide resistance is increasing generally both among penicillin-resistant and penicillin-susceptible isolates of S. pneumoniae and its prevalence now exceeds that of penicillin resistance, overall (16.5% and 10.4%, respectively, in 1996; 21.9% and 14.1% in 1997; 16.5% and 11.6% in 1998). Beta-lactamase production was the principal mechanism of resistance observed among isolates of Haemophilus influenzae and Moraxella catarrhalis.

In vitro study of the post-antibiotic effect and the bactericidal activity of Cefditoren and ten other oral antimicrobial agents against upper and lower respiratory tract pathogens

The in vitro post-antibiotic effect (PAE) and batericidal activity of cefditoren was compared to that of cefixime, cefuroxime, loracarbef, cefaclor, amoxicillin, amoxicillin/clavulanate, clarithromycin, azithromycin, erythromycin, and ciprofloxacin against ATCC culture strains and clinical respiratory isolates. A PAE > 1 h was observed for cefditoren and generally for the macrolides against Streptococcus pneumoniae, beta-lactamase-negative Moraxella catarrhalis, and Streptococcus pyogenes, whereas the other beta-lactams showed mixed results. Cefditoren was the only beta-lactam showing significant bactericidal activity (>3 log reduction of viable cells) within 4 h against penicillin-resistant S. pneumoniae. Only cefditoren and ciprofloxacin showed significant bactericidal activity against beta-lactamase-negative (after 24 h) and beta-lactamase-positive strains of H. influenzae (after 12 h). Against beta-lactamase-positive strains of M. catarrhalis, cefditoren was the only agent to show significant bactericidal activity at 6 h (versus cefuroxime and ciprofloxacin at 12 h).

Inhibitory and bactericidal effects of hydrogen peroxide production by Streptococcus pneumoniae on other inhabitants of the upper respiratory tract

An inverse correlation between colonization of the human nasopharynx by Streptococcus pneumoniae and Haemophilus influenzae, both common upper respiratory pathogens, has been reported. Studies were undertaken to determine if either of these organisms produces substances which inhibit growth of the other. Culture supernatants from S. pneumoniae inhibited growth of H. influenzae, whereas culture supernatants from H. influenzae had no effect on the growth of S. pneumoniae. Moreover, coculture of S. pneumoniae and H. influenzae led to a rapid decrease in viable counts of H. influenzae. The addition of purified catalase prevented killing of H. influenzae in coculture experiments, suggesting that hydrogen peroxide may be responsible for this bactericidal activity. H. influenzae was killed by concentrations of hydrogen peroxide similar to that produced by S. pneumoniae. Hydrogen peroxide is produced by the pneumococcus through the action of pyruvate oxidase (SpxB) under conditions of aerobic growth. Both an spxB mutant and a naturally occurring variant of S. pneumoniae, which is downregulated in SpxB expression, were unable to kill H. influenzae. A catalase-reversible inhibitory effect of S. pneumoniae on the growth of the respiratory tract pathogens Moraxella catarrhalis and Neisseria meningitidis was also observed. Elevated hydrogen peroxide production, therefore, may be a means by which S. pneumoniae is able to inhibit a variety of competing organisms in the aerobic environment of the upper respiratory tract.