Antibiotic resistance of microorganisms involved in ear, nose and throat infections

Developmental Population Pharmacokinetics-Pharmacodynamics of Meropenem in Chinese Neonates and Young Infants: Dosing Recommendations for Late-Onset Sepsis

The pharmacokinetic (PK) studies of meropenem in Chinese newborns with late-onset sepsis (LOS) are still lacking. Causative pathogens of LOS and their susceptibility patterns in China differ from the data abroad. We, therefore, conducted a developmental population pharmacokinetic−pharmacodynamic analysis in Chinese newborns with the goal to optimize meropenem dosing regimens for LOS therapy. An opportunistic sampling strategy was used to collect meropenem samples, followed by model building and validation. A Monte Carlo simulation was performed to show the probability of target attainment (PTA) for various dosages. The information from 78 newborns (postmenstrual age: 27.4−46.1 weeks) was compiled and had a good fit to a 1-compartment model that had first order elimination. The median (range) values of estimated weight−normalized volume of distribution (V)and clearance (CL) were 0.60 (0.51−0.69) L/kg and 0.16 (0.04−0.51) L/h/kg, respectively. Covariate analysis revealed that postnatal age (PNA), gestational age (GA) and current weight (CW) were the most important factors in describing meropenem PK. Simulation results showed for LOS with a minimal inhibitory concentration (MIC) of 8 mg/L, the doses of 30 mg/kg 3 times daily (TID) as a 1-h infusion for newborns with GA ≤ 37 weeks and 40 mg/kg TID as a 3-h infusion for those with GA > 37 weeks were optimal, with PTA of 71.71% and 75.08%, respectively. In conclusion, we proposed an evidence-based dosing regimen of meropenem for LOS in Chinese newborns by using the population pharmacokinetic−pharmacodynamic analysis, based on domestic common pathogens and their susceptibility patterns.

Simulation study of electric-guided delivery of 0.4µm monodisperse and polydisperse aerosols to the ostiomeatal complex

Despite the high prevalence of rhinosinusitis, current inhalation therapy shows limited efficacy due to extremely low drug delivery efficiency to the paranasal sinuses. Novel intranasal delivery systems are needed to enhance targeted delivery to the sinus with therapeutic dosages. An optimization framework for intranasal drug delivery was developed to target polydisperse charged aerosols to the ostiomeatal complex (OMC) with electric guidance. The delivery efficiency of a group of charged aerosols recently reported in the literature was numerically assessed and optimized in an anatomically accurate nose-sinus model. Key design variables included particle charge number, particle size and distribution, electrode strength, and inhalation velocity. Both monodisperse and polydisperse aerosol profiles were considered. Results showed that the OMC delivery efficiency was highly sensitive to the applied electric field and electrostatic charges carried by the particles. Through the synthesis of electric-guidance and point drug release, focused deposition with significantly enhanced dosage in the OMC can be achieved. For 0.4 µm charged aerosols, an OMC delivery efficiency of 51.6% was predicted for monodisperse aerosols and 34.4% for polydisperse aerosols. This difference suggested that the aerosol profile exerted a notable effect on intranasal deliveries. Sensitivity analysis indicated that the OMC deposition fraction was highly sensitive to the charge and size of particles and was less sensitive to the inhalation velocity considered in this study. Experimental studies are needed to validate the numerically optimized designs. Further studies are warranted to investigate the targeted OMC delivery with both electric and acoustics controls, the latter of which has the potential to further deliver the drug particles into the sinus cavity.

Numerical optimization of targeted delivery of charged nanoparticles to the ostiomeatal complex for treatment of rhinosinusitis

BACKGROUND

Despite the prevalence of rhinosinusitis that affects 10%-15% of the population, current inhalation therapy shows limited efficacy. Standard devices deliver <5% of the drugs to the sinuses due to the complexity of nose structure, secluded location of the sinus, poor ventilation, and lack of control of particle motions inside the nasal cavity.

METHODS

An electric-guided delivery system was developed to guide charged particles to the ostiomeatal complex (OMC). Its performance was numerically assessed in an MRI-based nose-sinus model. Key design variables related to the delivery device, drug particles, and patient breathing were determined using sensitivity analysis. A two-stage optimization of design variables was conducted to obtain the best performance of the delivery system using the Nelder-Mead algorithm.

RESULTS AND DISCUSSION

The OMC delivery system exhibited high sensitivity to the applied electric field and electrostatic charges carried by the particles. Through the synthesis of electric guidance and point drug release, the new delivery system eliminated particle deposition in the nasal valve and turbinate regions and significantly enhanced the OMC doses. An OMC delivery efficiency of 72.4% was obtained with the optimized design, which is one order of magnitude higher than the standard nasal devices. Moreover, optimization is imperative to achieve a sound delivery protocol because of the large number of design variables. The OMC dose increased from 45.0% in the baseline model to 72.4% in the optimized system. The optimization framework developed in this study can be easily adapted for the delivery of drugs to other sites in the nose such as the ethmoid sinus and olfactory region.

Trends in antibiotic resistance of respiratory tract pathogens in children in Geneva, Switzerland

Bacteria increasingly resistant to antibiotics are a major treatment concern of respiratory tract pathogens in children. The aim of this study was to assess the trends of resistance of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis to several classes of antibiotics in children<16 years of age and to compare its prevalence with surrounding countries. We studied retrospectively the susceptibility of respiratory tract pathogens isolated from specimens collected from patients at the Geneva Children's Hospital between 1989 and 2004. The susceptibility of S. pneumoniae to penicillin decreased from 98% to 58% (P<0.001) within 16 years, mainly due to strains intermediately resistant (MICs 0.12-1.0 microg/ml). Also erythromycin-susceptible pneumococci decreased from 97% to 63% (P<0.001). The susceptibility of H. influenzae to amoxicillin also significantly declined (87% vs. 82%, P<0.001), and the susceptibility of M. catarrhalis to this drug almost disappeared (29% vs. 5%, P<0.001). However, in 2004 these two bacteria remained 100% susceptible to amoxicillin-clavulanic acid, second and third generation cephalosporins. Invasive H. influenzae strains were significantly more resistant to ampicillin than non-invasive strains, but no susceptibility difference between invasive and non-invasive S. pneumoniae was determined.

CONCLUSION

During the 16 years studied, the antibiotic resistance of respiratory tract pathogens steadily and significantly increased in children, especially S. pneumoniae. This situation in Geneva is similar to neighbouring France rather than to the rest of Switzerland. A permanent surveillance of microbial susceptibility to antibiotics is essential and a limitation of antibiotic prescription together with information of the judicious use may impede the actual resistance trend.

Community prescribing and resistant Streptococcus pneumoniae

We investigated the association between prescribing antimicrobial agents and antimicrobial resistance of Streptococcus pneumoniae among children with acute otitis media in southern Israel. During a 6-year period, all prescriptions of a sample of ≈20% of Jewish and Bedouin children <5 years of age were recorded and all pneumococcal isolates from middle ear fluid were collected. Although antimicrobial drug use was significantly higher in Bedouin children, the proportion of S. pneumoniae isolates with penicillin MIC ≥1.0 μg/mL was significantly higher in Jewish children. In both populations, antimicrobial prescriptions were markedly reduced over time, especially for penicillins and erythromycin. In contrast, azithromycin prescriptions increased from 1998 to 2001 with a parallel increase in macrolide and multidrug resistance. Penicillin resistance was associated with macrolide resistance. These findings strongly suggest that azithromycin affects increased antimicrobial resistance, including multidrug resistance, in S. pneumoniae.

Ecological effects on the oro- and nasopharyngeal microflora in children after treatment of acute otitis media with cefuroxime axetil or amoxycillin-clavulanate as suspensions

OBJECTIVE

To evaluate if the extent of normal microflora disturbances differed between treatment with amoxycillin-clavulanate administered in an active form and cefuroxime axetil administered as an inactive prodrug.

METHODS

Twenty-eight children, 0.5-5 years old, diagnosed with acute otitis media (AOM), were treated with either amoxycillin-clavulanate (13.3 mg/kg 3 times daily) or cefuroxime axetil (15 mg/kg twice daily) for 7 days. Saliva samples and nasopharyngeal swabs were collected before, directly after and 2 weeks after treatment. The saliva samples were quantitatively and qualitatively analyzed and the nasopharyngeal swabs were qualitatively analyzed. All isolated strains were tested for beta-lactamase production.

RESULTS

Both treatment regimens gave rise to similar alterations of the normal oropharyngeal microflora. In both groups, the amount of Streptococcus salivarius was significantly reduced (P < 0.05). The most common causative pathogens of acute otitis were S. pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. On the day of enrollment, approximately half of the patients, in both groups, were infected with more than one pathogen. The rate of infection or colonization with more than one potential pathogen was low on day 7 but recurred 2 weeks after treatment to similar levels as on day 0. The total number of patients with reinfection, recolonization or recurrence of pathogens on day 21 was 11/12 in the amoxycillin-clavulanate group and 4/7 in the cefuroxime axetil group. The most common beta-lactamase producer was M. catarrhalis.

CONCLUSION

The local high concentration of antibiotics in the oropharynx immediately after intake of antibiotic suspensions seem to have little or no impact on the extent of disturbance of the microflora in this region. Children of this age group seem prone to either reinfection, recolonization or persistence of pathogens within 2 weeks after treatment. Furthermore, co-infection with more than one pathogen seems common in children with AOM and infection with beta-lactamase producing microorganisms occurs frequently.

Prevalence of penicillin-resistant Streptococcus pneumoniae in Kuwait

The worldwide incidence of penicillin-resistant Streptococcus pneumoniae has increased at an alarming rate during the past decade. However, there has been little published data about the extent of this problem in Kuwait. The present study was undertaken to ascertain the preponderance of S. pneumoniae, either resistant or intermediate-resistant to penicillin, other beta-lactams and non-beta-lactam antimicrobials in Kuwait. Two hundred and fifty fresh isolates from as many patients suffering from different clinical conditions were collected from all clinics and hospitals in Kuwait. Optochin sensitivity and bile solubility tests reconfirmed these. Susceptibility testing to penicillin, ampicillin, cefuroxime, ceftriaxone, cefotaxime, imipenem, erythromycin, chloramphenicol, ciprofloxacin and vancomycin was done using E-test strips and to oxacillin, tetracycline, trimethoprim and amoxicillin-clavulanate by disc diffusion technique. Full and intermediate resistance to penicillin was observed in 1.6% and 52.8% of the isolates respectively. Full resistance to third-generation cephalosporins ranged from 0.4% to 3.2%, however, intermediate resistance to these antibiotics varied between 18.8% and 21.2%. Ampicillin resistance was noted in 0.8%, but 40.4% of isolates were intermediately resistant. However, only 0.4% of the isolates showed either intermediate or full resistance to amoxicillin-clavulanate. Resistance to imipenem was observed in 0.4% and intermediate to 13.6% of the organisms. The rates of S. pneumoniae resistant to chloramphenicol, erythromycin, tetracycline and trimethoprim were between 8.4% and 37.6% and intermediate resistance between 1.2% and 17.6% while only 0.4% showed resistance to ciprofloxacin and none to vancomycin. Multiresistance to both beta-lactam and non-beta-lactam antibiotics was observed in 52% of the penicillin-resistant isolates.

Pharmacodynamics and pharmacokinetics of cefdinir, an oral extended spectrum cephalosporin

BACKGROUND

Oral second and third generation cephalosporins are undergoing continuing research and development in the arena of pediatric infectious disease in an attempt to fill voids created by existing agents in the quest for the "ideal" antimicrobial. This paper reviews the in vitro antimicrobial activity (pharmacodynamics) and pharmacokinetics of cefdinir, an extended spectrum oral cephalosporin, with an emphasis on those aspects relevant to the pediatric patient population.

METHODS

A MEDLINE literature search was conducted for the years 1985 through 2000, identifying all English language papers examining the in vitro antimicrobial activity and human pharmacokinetics of cefdinir. Bibliographies of these papers were reviewed, as were relevant data on file with the manufacturer.

DATA SYNTHESIS

Cefdinir exhibits broad range in vitro activity against Gram-positive and Gram-negative aerobes. It exhibits superior activity against Gram-positive aerobes, compared with drugs like cefixime, ceftibuten, cefuroxime and cefpodoxime. In addition it is stable to hydrolysis by many of the common betalactamases. The pharmacokinetic parameters of cefdinir in children are similar to those obtained in adults using similar milligram per m2 doses (300, 600 mg in adults = 7, 14 mg/kg in children, respectively).

CONCLUSIONS

The pharmacodynamic and pharmacokinetic characteristics of cefdinir as described in this paper, as well as the results of the clinical trials program, support the use of this agent in the treatment of a wide variety of pediatric infectious diseases.

Acute otitis media: bacteriology and bacterial resistance in 205 pediatric patients

Acute otitis media (AOM) is one of the most frequent diagnoses in children below the age of 2 years. Treatment is usually based on information included in the literature concerning bacteriology. The purpose of this work was to define the most frequent germs in the etiology of AOM within our community, in order to optimize therapeutics for this pathology. Cultures in middle ear secretions obtained through tympanocentesis were performed to this end, ensuring careful sample taking and processing. The results obtained are similar to those published in previous papers for which Streptococcus pneumoniae and Haemophilus influenzae proved to be the predominant germs. However, there are certain discrepancies concerning the incidence of Moraxella catarrhalis and this has a direct impact on the total percent of resistant strains, thus modifying therapeutic approaches for treatment of AOM. The antibiotic sensitivity profiles of the most frequent etiologic agents were studied in accordance with the principles established by the 'National Committee for Clinical Laboratory Standards' (NCCLS).

Acute mastoiditis in children: review of the current status

BACKGROUND

acute mastoiditis is the most common intratemporal complication of otitis media. Its management is still a challenge due to potentially serious consequences. This study was designed to evaluate the recent experience with pediatric acute mastoiditis at our institution and to determine if the incidence of this entity is changing over time.

MATERIAL AND METHODS

retrospective review of records of children with acute mastoiditis treated at the hospital of the Medical School at the University of Porto, Portugal, between July 1993 and June 1998. Criteria for the diagnosis of acute mastoiditis were postauricular swelling and erythema, protrusion of the auricle, and evidence of co-existent or recent otitis media.

RESULTS

43 patients fulfilled the entry criteria. Most were boys (69%). Ages ranged from 8 months to 14 years and 4 months; infants represented 40% of the total. Acute mastoiditis was the first recognized sign of otitis media in 48% of patients. More recent years of the study saw an increase in the number of children referred with acute mastoiditis. Upon admission, 56% were under antibiotic treatment, with an average intake of 5.8 days. All patients were hospitalized; 26 cases recovered after intravenous antibiotics plus myringotomy, and the rest required an additional surgical procedure. The most common organisms recovered from cultures were Streptococcus pneumoniae and Streptococcus pyogenes. In our series, associated complications occurred in 13.9%; facial paralysis in one, and involvement of the central nervous system in five.

CONCLUSIONS

pediatric acute mastoiditis continues to be a potentially dangerous infection in the antibiotic era. The incidence of this complication may be increasing recently in the community studied. Great care is required of clinicians to reach an early diagnosis in order to promote adequate management and prevent inherently severe complications.

Predictive value of pneumococcal nasopharyngeal cultures for the assessment of nonresponsive acute otitis media in children

BACKGROUND

Nonresponsive acute otitis media (NR-AOM) is reported in > 10% of children with AOM treated with antibiotics. Drug-resistant Streptococcus pneumoniae is currently considered the leading cause of antibiotic failures in AOM. Nasopharyngeal colonization with S. pneumoniae was found to increase significantly during episodes of AOM.

OBJECTIVES

To investigate the nasopharyngeal colonization with S. pneumoniae during NR-AOM and compare it with that found in AOM not recently treated with antibiotics (NT-AOM); to assess the predictive value of nasopharyngeal pneumococcal cultures results for the bacteriologic assessment of NR-AOM.

MATERIALS AND METHODS

Patients age 3 to 48 months with NT-AOM and NR-AOM were prospectively studied. Simultaneous nasopharyngeal cultures for S. pneumoniae and middle ear fluid cultures were obtained at enrollment. Antibiotic susceptibility testing was performed in all S. pneumoniae isolates. Penicillin and ceftriaxone MICs for S. pneumoniae were determined by E-test. The sensitivity, specificity and positive and negative predictive values of positive or negative nasopharyngeal cultures for the presence of S. pneumoniae in middle ear fluid were calculated.

RESULTS

We studied 362 and 217 children with NT-AOM and NR-AOM, respectively. Of the children with NT-AOM and NR-AOM, 95 and 97%, respectively, were younger than 2 years of age. S. pneumoniae was isolated in the nasopharynx of 66 and 58% of children with NT-AOM and NR-AOM, respectively. Penicillin-nonsusceptible S. pneumoniae was isolated more frequently from the nasopharynx of patients with NR-AOM than from those with NT-AOM (84% vs. 47%; P < 0.01). Antibiotic susceptibility patterns were similar for S. pneumoniae isolates recovered from the nasopharynx and those from the middle ear fluid in both NT-AOM and NR-AOM. A positive nasopharyngeal culture had only little predictive value for the presence of S. pneumoniae in middle ear fluid (41 and 51% for NT-AOM and NR-AOM, respectively). However, the negative predictive value of nasopharyngeal cultures for recovery of S. pneumoniae in NR-AOM was high and significantly higher in NR-AOM than in NT-AOM (91% vs. 78%, respectively; P = 0.009). The negative predictive value of nasopharyngeal cultures for recovery of antibiotic-resistant S. pneumoniae was 95 and 93% in NT-AOM and NR-AOM, respectively. Conclusions. A significantly higher nasopharyngeal colonization rate with antibiotic-resistant S. pneumoniae was found in patients with NR-AOM than in those with NT-AOM. Negative nasopharyngeal culture for antibiotic-resistant S. pneumoniae practically rules out its presence in middle ear fluid.

Pneumococcal resistance to beta-lactam antibiotics: a global geographic overview

beta-Lactam resistance in Streptococcus pneumoniae has spread over the entire world. The 10 main foci of resistant organisms are located in the following areas: (1) southwest Europe (Spain, France, Portugal), (2) central-east Europe (Hungary, Roumania, Bulgaria, Turkey) and Israel, (3) northwest Russia, (4) South Africa, (5) Japan and South Korea, (6) Papua-New Guinea, (7) Alaska, (8) southeast North America, (9) southwest North America, and (10) south cone in South America. A comparison of the presumed factors influencing the increase of pneumococcal resistance in these foci with those occurring in low incidence areas, such as central-north Europe, Scandinavia, north and western Africa, or middle-north Mediterranean countries (Italy, Greece) should provide the clues to predict and prevent further spread of resistant pneumococci.

Resistant bacteria in middle ear fluid at the time of tympanotomy tube surgery

This study was performed to determine the prevalence of resistant Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolated from middle ear fluid of children undergoing placement of ventilation tubes. The extent of resistance to commonly prescribed antibiotics and the risk factors associated with this resistance were also examined. Children who had fluid present in their middle ears at the time of ventilation tube placement from May 1996 to May 1997 were included in the study. Middle ear fluid was plated onto culture media in the operating room, and antimicrobial resistance of cultured organisms was ascertained. Risk factors for this resistance were determined from the medical history and analyzed. Cultures of 244 patients (355 ears) were positive for organisms in 29.6%. Penicillin resistance was found in 38.2% of S pneumoniae cultures. Beta-lactamase production was found in 65.1% and 100% of H influenzae and M catarrhalis specimens, respectively. Risk factor analysis revealed young age, day care attendance, and number of antibiotic courses to most reliably predict the presence of resistant microorganisms.

Dynamics of interleukin-1 production in middle ear fluid during acute otitis media treated with antibiotics

In an ongoing prospective study, IL-1 concentrations were measured in 78 children (aged 3-36 months) with acute otitis media receiving antibiotics. Middle ear fluid IL-1 concentrations were determined using ELISA kits. Ninety-eight middle ear fluid samples were obtained by tympanocentesis at enrollment (day 1) and 43 samples were collected on days 4-5. Ninety-two pathogens were isolated in 77/98 samples obtained on day 1: 55 Haemophilus influenzae, 34 Streptococcus pneumoniae, 2 Moraxella catarrhalis and 1 Streptococcus pyogenes. Among 37 paired samples initially culture-positive, eradication of the pathogen was achieved on day 4-5 in 20 while pathogens were still present in 17. On day 1, IL-1 was detected in 61/77 (79%) culture-positive samples vs 9/21 (43%) culture-negative ones (P = 0.003). The mean +/- SD middle ear fluid concentration of IL-1 on day 1 was significantly higher in culture-positive (316 +/- 508 pg/ml) than in culture-negative samples (111 +/- 245 pg/ml) (P = 0.01). When paired samples were evaluated, IL-1 decreased on days 4-5 in 13/20 (65%) ears where bacterial eradication was achieved, but also in 11/19 (58%) with persistent or new infection. The mean IL-1 concentrations decreased on days 4-5 in the 20 samples from ears where bacterial eradication was achieved (330 +/- 460 vs 118 +/- 294 pg/ml, P = 0.1) but also in the 17 samples where it was not (465 +/- 660 vs 232 +/- 289 pg/ml, P = 0.02). No significant differences were found between day 1 and days 4-5 in the mean IL-1 concentrations measured in patients with H. influenzae vs S. pneumoniae or concomitant H. influenzae and S. pneumoniae. It was concluded that: 1) IL-1 was detected in the middle ear fluid of most patients with acute otitis media; 2) significantly higher IL-1 concentrations were found in patients with culture-positive than in those with culture-negative acute otits media; 3) IL-1 concentrations decreased on days 4-5 of antibiotic therapy, whether the pathogen was eradicated or not.

The efficacy and safety of a new ciprofloxacin suspension compared with co-amoxiclav tablets in the treatment of acute exacerbations of chronic bronchitis

A multinational, multicentre, randomized, prospective, parallel-group study compared treatment with ciprofloxacin administered as an oral suspension (500 mg twice daily for 7 days) with co-amoxiclav tablets (625 mg three times daily for 7 days) in patients suffering from acute exacerbations of chronic bronchitis (AECB). A total of 147 of 165 cases treated with ciprofloxacin (89.1%) and 146 of 162 cases treated with co-amoxiclav (90.1%) were classified as being clinical successes at the primary efficacy assessment 7 days after the end of therapy (assessed as reduced cough, improvement in dyspnoea, reduction in 24-h sputum volume or reduced purulence of sputum). Treatment equivalence was statistically confirmed; treatment difference:--1.0%, 95% CI--6.6% and 4.5%. Before treatment, 128 bacterial strains were isolated from 103 patients (60 ciprofloxacin and 68 co-amoxiclav). The most commonly isolated organism was Haemophilus influenzae (60 isolates), followed by Moraxella catarrhalis (12 isolates), Streptococcus pneumoniae (11 isolates) and Staphylococcus aureus (10 isolates). At day 14, 40 of 46 ciprofloxacin-treated patients (87.0%) and 46 of 55 co-amoxiclav-treated patients (83.6%) who were valid for bacteriological analysis were classified as being bacteriological success (classed as eradication, eradication with colonization or presumed eradication; treatment difference: 3.3%, 95% CI--8.3% and 14.9%). The adverse event profile was comparable between treatment groups. Most adverse events considered possibly or probably related to study drug were related to the gastrointestinal system and were of mild or moderate severity: nausea (13% ciprofloxacin, 10.6% co-amoxiclav), flatulence (10.3% ciprofloxacin, 3.9% co-amoxiclav), abdominal pain (7.6% ciprofloxacin, 7.3% co-amoxiclav) and diarrhoea (4.3% ciprofloxacin, 6.7% co-amoxiclav). We concluded that a 7-day course of ciprofloxacin suspension is equivalent to a 7-day course of co-amoxiclav tablets in terms of clinical and bacteriological efficacy and tolerability for the treatment of AECB. Thus, ciprofloxacin suspension may offer a suitable alternative treatment for AECB patients who have difficulty in swallowing, or who prefer liquid medications to tablets.

The bactericidal activity of levofloxacin against ampicillin-resistant and ampicillin-susceptible Haemophilus influenzae in comparison with ofloxacin, ciprofloxacin and sparfloxacin

The bactericidal activity of levofloxacin against four Haemophilus influenzae clinical isolates (two ampicillin-resistant and two susceptible) was compared with that of ofloxacin, ciprofloxacin and sparfloxacin at concentrations simulating the peak serum concentrations obtained with the recommended oral doses. Bactericidal activity was assessed using time-kill curves and minimum kill-time values. Both concentrations of levofloxacin rapidly killed all the study strains, with mean kill times of 4 h and no viable bacteria remaining after 18-h exposure. The bactericidal activities of levofloxacin, ofloxacin and sparfloxacin were similar. The minimum kill-times for both concentrations of ciprofloxacin were 28-35% longer than those of levofloxacin. These results support the use of levofloxacin for H. influenzae infections, including ampicillin-resistant strains.

Bacteriologic efficacy of a three-day intramuscular ceftriaxone regimen in nonresponsive acute otitis media

OBJECTIVE

To determine the bacteriologic efficacy of ceftriaxone in nonresponsive acute otitis media in children.

METHODS

In a prospective study 92 patients ages 3 to 36 months (median, 11 months) with culture-proved nonresponsive acute otitis media were studied from January, 1995, through August, 1997. The patients were treated with intramuscular ceftriaxone (50 mg/kg/l/day) for 3 days. Middle ear fluid was aspirated for culture by tympanocentesis on day of enrollment (Day 1); a second tap was performed on Days 4 to 10. Additional middle ear fluid cultures were obtained if clinical relapse occurred. Bacteriologic failure was defined by positive culture on Days 4 to 10. Patients were followed until Day 17+/-2. Susceptibility was measured by E test.

RESULTS

The main drugs administered before enrollment were amoxicillin (38%), amoxicillinclavulanate (25%) and cefaclor (20%). Organisms recovered (n=105) were: Haemophilus influenzae, 54; Streptococcus pneumoniae, 47; Moraxella catarrhalis, 2; and Streptococcus pyogenes, 2. Thirty-four (72%) of the 47 S. pneumoniae isolates were intermediately resistant to penicillin (MIC 0.1 to 1.0 microg/ml), but all were susceptible to ceftriaxone (MIC < 0.5 microg/ml). Bacteriologic eradication was achieved in 100 of 105 (95%) cases: 54 of 54 (10O%) H. influenzae, 43 of 47 (92%) S. pneumoniae, 1 of 2 (50%) M. catarrhalis and 2 of 2 (100%) S. pyogenes. Bacteriologic success (with no relapse) occurred in 13 of 13 (100%) penicillin-susceptible S. pneumoniae vs. 28 of 34 (82%) S. pneumoniae intermediately resistant to penicillin (4 cases of bacteriologic failure and 2 cases of relapse).

CONCLUSION

A 3-day intramuscular ceftriaxone regimen is efficacious for the treatment of nonresponsive acute otitis media. The optimal duration of treatment in cases of nonresponsive acute otitis media and whether ceftriaxone is efficacious for the treatment of nonresponsive otitis media caused by S. pneumoniae highly resistant to penicillin is yet to be determined.

Resistance pattern of middle ear fluid isolates in acute otitis media recently treated with antibiotics

BACKGROUND

Little information is available about the effect of antibiotic treatment on the prevalence and MIC of the subsequently isolated pathogens in cases of acute otitis media (AOM) failing a course of antibiotic therapy. This information is important, particularly regarding the effectiveness of the oral antibiotics used in children failing initial therapy.

PATIENTS AND METHODS

One hundred eighty-one children with culture-positive AOM were prospectively studied between October, 1995, and July, 1996. Sixty-three (35%) patients received various antibiotics for variable periods during the 14 days preceding enrollment.

RESULTS

A total of 94 Streptococcus pneumoniae (Pnc) and 113 Haemophilus influenzae (Hi) were isolated. Thirty-eight Pnc and 35 Hi were isolated in the 63 patients with recently treated AOM. Pnc as a single isolate was more prevalent in patients recently treated with antibiotics (27 of 63, 43%) than among those not recently treated (32 of 118, 27%, P = 0.047). The MIC50 values of penicillin, cefaclor and cefuroxime axetil for Pnc were significantly higher in the pneumococci isolated from patients recently treated than among those isolated from patients not recently treated with antibiotics (0.38, 3 and 0.75 microg/ml vs. 0.094, 0.38 and 0.12 microg/ml, respectively). Seventy-nine percent of Pnc isolates in the recently treated group had MIC for penicillin of >0.1 microg/ml vs. only 47% in those not recently treated (P < 0.05). The respective figures for MIC >0.5 microg/ml of cefaclor were 79% vs. 41% for the recently treated and not recently treated groups (P < 0.001); cefuroxime MIC >0.5 microg/ml was found in 61 and 25%, respectively (P = 0.001).

CONCLUSIONS

Pneumococcus is more prevalent in AOM after a recent antibiotic treatment, and the MIC of the commonly used beta-lactam drugs for Pnc is considerably higher in this setting. In view of our data, the use of oral cephalosporins like cefaclor or cefuroxime as second line drugs in the treatment of unresponsive AOM, particularly in regions where resistant PNC is prevalent, should be reconsidered.

Self-reported prescribing of antibiotics for children with undifferentiated acute respiratory tract infections with cough

BACKGROUND

Physicians are often called on to manage children with acute respiratory tract infections with cough when the clinical presentation may not allow a differentiation between viral and bacterial etiology. To develop guidelines for appropriate antibiotic use, it is necessary to understand the present prescribing patterns of physicians who manage children presenting with such an undifferentiated acute respiratory tract infection with cough (UARTIC).

OBJECTIVES

To determine the variability of self-reported prescribing habits for antibiotics for children with UARTIC.

METHODS

In this cross-sectional survey by a modified Dillman's Total Design Method, a mail-out questionnaire was administered to a random sample of 181 primary care family physicians and pediatricians (Toronto, Ontario, Canada) to assess perceptions of their own antibiotic-prescribing habit.

RESULTS

Completed questionnaires were received from 136 (75%) eligible physicians; 32% reported that > 10% of their office visits were for UARTIC. For a 3-day history of UARTIC 24% reported prescribing antibiotics or antibiotics in reserve (i.e. a prescription to be filled if the patient's condition does not improve) always or most times. This increased to 45% when UARTIC had worsened in the 24 h before the office visit (P < 0.001).

CONCLUSION

When a pediatric patient presented with UARTIC, antibiotics or antibiotics in reserve were prescribed in the absence of clear indicators of bacterial infection. Research- and evidence-based guidelines are needed to support rational antibiotic use for UARTIC.

Influence of recent antibiotic therapy on antimicrobial resistance of Streptococcus pneumoniae in children with acute otitis media in Spain

BACKGROUND

Despite the high prevalence of penicillin resistance among Streptococcus pneumoniae strains in Spain (40 to 60% with MIC > or = 0.1 microg/ml), the data on acute otitis media (AOM) isolates are scarce. We conducted a prospective, longitudinal study to determine the rates of antimicrobial resistance of S. pneumoniae isolates from children with AOM in our country and to analyze the effect of previous antibiotic therapy on these rates.

METHODS

Tympanocentesis was performed on 169 children diagnosed with AOM (age range, 1 month to 14 years). Two groups were considered: Group A, 113 patients with non-antibiotic-treated AOM, subdivided into Group A1 (collected from 1989 to 1992) and Group A2 (1992 to 1996); Group B, 56 patients from the period 1992 to 1996, with AOM clinical failure, defined as worsening or persistent symptoms after at least 2 days of appropriate antibiotic therapy. Amoxicillin-clavulanate was the most frequent antibiotic used (68%), followed by azithromycin (21%), cefaclor and cefixime (11%).

RESULTS

A total of 63 S. pneumoniae isolates were recovered, 42 in Group A and 21 in Group B. Resistance to penicillin (MIC > or = 0.1 microg/ml) was found in 38% of strains in Group A (32% in A1 and 50% in A2), but in Group B the rate of resistance reached 90% (P = 0.0002). Erythromycin resistance was also increased from 35% (Group A2) to 62% (Group B), and trimethoprim-sulfamethoxazole resistance rose from 64% to 81%.

CONCLUSIONS

Resistance to penicillin among S. pneumoniae AOM isolates is frequent and is increasing in Spain. After failure of standard antibiotic therapy, the rates of penicillin resistance reached 90% of the isolates.

Myringotomy: a prerequisite for the development of myringosclerosis?

Streptococcus pneumoniae was inoculated into the left middle-ear cavity in two groups of rats, resulting in purulent otitis media. After 3 days, one group of infected animals and a third group of noninfected animals were subjected to left-sided myringotomy. The tympanic membranes were examined both otomicroscopically and histologically 1 and 3 months later. On otomicroscopic examination the noninfected myringotomized animals had developed extensive myringosclerotic lesions, whereas only minimal sclerotic deposits were noted in the myringotomized animals with acute otitis media (AOM). On histologic examination both the noninfected myringotomized animals and the myringotomized animals with AOM were similar in the frequency and extension of sclerotic lesions in the tympanic membrane. The nonmyringotomized rats with AOM were free of sclerotic lesions, except for minor changes found in one animal.

Efficacy and safety of a 10-day course of 400 or 600 milligrams of grepafloxacin once daily for treatment of acute bacterial exacerbations of chronic bronchitis: comparison with a 10-day course of 500 milligrams of ciprofloxacin twice daily

A randomized, prospective, double-blind, double-dummy, multicenter study investigated the efficacy and safety of 10 days of oral therapy with grepafloxacin at 400 mg once daily, grepafloxacin at 600 mg once daily, or ciprofloxacin at 500 mg twice daily in 624 patients with acute bacterial exacerbations of chronic bronchitis. At the end of treatment, clinical success (cure or improvement) was achieved for 93% (140 of 151), 88% (137 of 156), and 91% (145 of 160) of patients in the groups receiving grepafloxacin at 400 mg, grepafloxacin at 600 mg, and ciprofloxacin, respectively (clinically evaluable population). At follow-up (14 to 28 days posttreatment), the clinical success rates were 87% (124 of 143), 81% (122 of 151), and 80% (123 of 154) in the groups receiving grepafloxacin at 400 mg and 600 mg and ciprofloxacin, respectively. A total of 379 pathogens were isolated from 290 patients, with the most common isolates being Moraxella catarrhalis (21%), Staphylococcus aureus (20%), Haemophilus influenzae (18%), and Streptococcus pneumoniae (7%). For the evaluable population, successful bacteriologic response was obtained at the end of treatment for 96% (92 of 96), 98% (87 of 89), and 92% (82 of 90) of patients receiving grepafloxacin at 400 mg, grepafloxacin at 600 mg, and ciprofloxacin, respectively, and was maintained in 86% (82 of 95), 88% (78 of 89), and 82% (69 of 84) of patients, respectively, at follow-up. All pretreatment S. pneumoniae isolates were susceptible to grepafloxacin, but two strains were resistant to ciprofloxacin. All treatments were well tolerated, with the most frequently reported drug-related adverse events being nausea, taste perversion, and headache. All drug-related adverse events in the grepafloxacin groups were mild or moderate in severity. This study demonstrates that 10-day courses of grepafloxacin given at 400 or 600 mg once daily were as effective, clinically and bacteriologically, as ciprofloxacin given at 500 mg twice daily for the treatment of acute bacterial exacerbations of chronic bronchitis.

Macrolides in the management of streptococcal pharyngitis/tonsillitis

The most frequent bacterial cause of pharyngitis/tonsillitis, a common infection in children, is group A beta-hemolytic streptococci. Prevention of acute rheumatic fever is the principal goal of treatment, although antibiotic therapy may also relieve the signs and symptoms of infection, shorten the infective period and prevent suppurative complications. Penicillin is the drug of choice. Alternatives are required, however, for patients allergic to penicillin and may be needed if the rate of bacteriologic failure with penicillin observed during the past decade continues. Erythromycin is generally effective in this infection, but its use, especially in children, is complicated by the need for multiple daily doses, a lengthy treatment period and a high rate of gastrointestinal side effects. The newer macrolides clarithromycin and azithromycin offer lower rates of gastrointestinal complaints and more convenient dosing. Clarithromycin is recommended for twice daily and azithromycin for once daily administration. Because of its prolonged tissue half-life, the recommended duration of azithromycin therapy is 5 days, compared with 10 days for penicillin, erythromycin and clarithromycin. Newer macrolides are rational alternatives to erythromycin for streptococcal pharyngitis/tonsillitis in penicillin-allergic patients.

Causative pathogens, antibiotic resistance and therapeutic considerations in acute otitis media

Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis are the most frequently isolated pathogens in patients with acute otitis media (AOM). Other potential causative pathogens include Streptococcus pyogenes in older children and Chlamydia pneumoniae in younger children. The recent emergence of penicillin-resistant S. pneumoniae and the increasing frequency of beta-lactamase-producing strains of M. catarrhalis and H. influenzae are creating concerns regarding the use of amoxicillin as traditional first line empiric therapy for AOM in younger children. Both the in vitro antibiotic activity against these more resistant causative pathogens and the antibiotic concentrations achieved in middle ear fluid must be considered when selecting antibiotics for treatment of refractory AOM. The newer macrolides, azithromycin and clarithromycin, provide reasonable in vitro coverage against penicillin-resistant S. pneumoniae and beta-lactamase-producing H. influenzae, although azithromycin is more active against the latter. Both drugs also achieve notably higher, sustained concentrations in middle ear fluid than do beta-lactam antibiotics. Thus the newer macrolides represent important new rational alternatives for the management of AOM.

Sinusitis in children and adolescents

Sinusitis is common in children and adolescents, most frequently as a complication of a viral upper respiratory tract infection or allergic rhinitis. The diagnosis usually is suggested by symptoms of a viral upper respiratory tract infection persisting beyond 10 days without improvement or severe symptoms with fever and purulent rhinitis. Young children frequently do not have the symptoms (headache) or physical findings (sinus tenderness) seen in older patients. Radiographic evaluation may be helpful if the clinical presentation is atypical or severe. Antibiotics remain the primary therapeutic agent of choice in pediatric sinusitis, with other therapeutic modalities having little proven efficacy.

Streptococcal diagnostic testing and antibiotics prescribed for pediatric tonsillopharyngitis

BACKGROUND

This study examined a 1-year cross-sectional sample of Kentucky Medicaid claims for the use of streptococcal diagnostic tests for pediatric tonsillopharyngitis and the empiric use of antibiotics.

METHODS

Subjects were individuals older than 3 and younger than 18 years old seen in an ambulatory setting for tonsillopharyngitis; 3478 individuals accounted for the 5067 separate outpatient and emergency room encounters for pediatric tonsillopharyngitis; 849 encounters coded as streptococcal sore throat were also examined.

RESULTS

Diagnostic tests for group A streptococcal tonsillopharyngitis were performed in only 22% (n = 1130) of the tonsillopharyngitis encounters and 36% (n = 306) of the streptococcal sore throat encounters. Urban physicians were more likely than rural physicians to use a diagnostic test (P = 0.0001). Emergency room encounters and outpatient encounters were not significantly different in the likelihood of having a diagnostic test (P = 0.16). In encounters for tonsillopharyngitis antibiotics were prescribed in 72% of the total encounters and in 73% of the encounters without a diagnostic streptococcal test. In encounters for streptococcal sore throat, antibiotics were prescribed for 68% of the total encounters and 69% of the encounters without a diagnostic streptococcal test.

CONCLUSIONS

Current practices in the Kentucky Medicaid program do not follow the American Academy of Pediatrics guidelines for streptococcal tonsillopharyngitis.

Efficacy of single-dose ceftriaxone in experimental otitis media induced by penicillin- and cephalosporin-resistant Streptococcus pneumoniae

We used a gerbil model of otitis media to assess the efficacy of single-dose ceftriaxone against three Streptococcus pneumoniae strains highly resistant to penicillin (MICs, 4 to 8 micrograms/ml) and with various susceptibilities to ceftriaxone (MICs, 0.5, 4, and 8 micrograms/ml). Middle ear infection was induced by bilateral transbullar challenge with 10(7) bacteria per ear. Antibiotic treatment was administered subcutaneously at 2 h postinfection. Infection status was checked 2 days later by counting the bacteria in middle ear and cerebrospinal fluid samples. With the cefriaxone-susceptible strain (MIC, 0.5 microgram/ml), we tested doses of 5 to 100 mg/kg of body weight. With a dose of 50 mg/kg, treatment outcome was equivalent to that with amoxicillin, which was used as a reference (25 mg/kg, two injections); no bacteria were recovered from 82% of the middle ear samples, and the rate of cerebrospinal fluid culture positivity was significantly reduced to 6%, relative to 59% for the untreated controls. Similar efficacy was obtained with a dose of 100 mg/kg against the two ceftriaxone-resistant strains. Pharmacokinetic study indicates that the values of the parameters in plasma after the administration of a dose of 100 mg/kg (peak level of total drug, 268 +/- 33 micrograms/ml; elimination half-life, 0.8 h; area under concentration-time curve, 488 micrograms.h.ml-1) were still suboptimal compared with the values of the parameters measured in pediatric patients after intravenous or intramuscular administration of a dose of 50 mg/kg. Our results indicate the efficacy of ceftriaxone against experimental cephalosporin-resistant pneumococcal otitis and provide a basis for the clinical use of single-dose ceftriaxone against pneumococcal otitis media.

Healing of tympanic membrane after myringotomy during Streptococcus pneumoniae otitis media. An otomicroscopic and histologic study in the rat

The purpose of our study was to elucidate the course of healing of the tympanic membrane (TM) when myringotomy was performed during acute otitis media. The early and long-lasting structural changes of the TM were studied in an animal model. Rats were inoculated with Streptococcus pneumoniae (PnC) type 3 in the bulla. When the infection was manifest, myringotomy was performed. On days 4 and 12, and 3 and 6 months after myringotomy, the TM status was checked by otomicroscopy and TMs were prepared for light and electron microscopy. Comparison was made with PnC-infected TMs that were not perforated, as well as myringotomized noninfected TMs. The infection resolved more slowly in myringotomized ears compared to PnC-infected ears that were left untouched. After 6 months, the pars tensa of the myringotomized infected ears was thickened and showed a disorganized collagen structure, compared with myringotomized noninfected ears, in which TMs were normalized. The PnC-infected TMs without myringotomy were completely normalized after 2 months. We conclude that a combination of bacterial infection and myringotomy causes long-lasting changes in TM structure. This impaired structure of the connective tissue could be of importance in chronic middle ear disease as a presumptive site for retraction and perforation of the TM.

Sequential, single-dose pharmacokinetic evaluation of meropenem in hospitalized infants and children

Meropenem is a new carbapenem antibiotic which possesses a broad spectrum of antibacterial activity against many of the pathogens responsible for pediatric bacterial infections. In order to define meropenem dosing guidelines for children, an escalating, single-dose, pharmacokinetic study at 10, 20, and 40 mg/kg of body weight was performed. A total of 73 infants and children in four age groups were enrolled in the study: 2 to 5 months, 6 to 23 months, 2 to 5 years, and 6 to 12 years. The first patients enrolled were those in the oldest age group, who received the lowest dose. Subsequent enrollment was determined by decreasing age and increasing dose. Complete studies were performed on 63 patients. No age- or dose-dependent effects on pharmacokinetic parameter estimates were noted. Mean pharmacokinetic parameter estimates were as follows: half-life, 1.13 +/- 0.15 h; volume of distribution at steady state, 0.43 +/- 0.06 liters/kg; mean residence time, 1.57 +/- 0.11 h; clearance, 5.63 +/- 0.75 ml/min/kg; and renal clearance, 2.53 +/- 0.50 ml/min/liters kg. Approximately 55% of the administered dose was recovered as unchanged drug in the urine during the 12 h after dosing. No significant side effects were reported in any patients. By using the derived pharmacokinetic parameter estimates, a dose of 20 mg/kg given every 8 h will maintain plasma meropenem concentrations above the MIC that inhibits 90% of strains tested for virtually all potentially susceptible bacterial pathogens.

The problem of resistant bacteria for the management of acute otitis media

The emergence of pneumococci resistant to penicillin has prompted an examination of the role of resistant organisms in the response to treatment for AOM. At this time, antibiotic-resistant organisms play a small role in the number of episodes of AOM that do not respond to initial therapy. Amoxicillin remains the drug of choice for treatment of AOM. For children who do not respond, assessment of clinical status is important. Children who are well-appearing may respond to a beta-lactamase stable oral agent. Children who are ill may require tympanostomy and presumptive therapy for infection due to resistant organisms.