1

Introduction

Bacterial rhinosinusitis is one of the most common pediatric infections leading to consults with general practitioners. These infections are important not only as a cause of frequent morbidity but also for the tremendous health care expenditures from antibiotic prescriptions . Although most acute bacterial rhinosinusitis is effectively treated with antibiotics of adequate spectrum, chronic rhinosinusitis in children is a more difficult problem and is often refractory to standard antimicrobial therapy. This may be due to limited understanding about the disease, as well as the dramatic rise of antibiotic resistance in the past decades.

Although the bacteriology of pediatric chronic rhinosinusitis appears to be well established, inquiries on current bacterial resistance patterns are limited. Numerous studies have been conducted to characterize antibiotic resistance in rhinosinusitis recently, either via endoscopic middle meatus sampling or intraoperative biopsy . The subjects of these studies, however, are mainly adults, and pediatric patients are seldom included. Furthermore, a large-scale surveillance examining the antimicrobial susceptibility of upper respiratory pathogens reveals an ongoing evolution and geographic variation in bacterial resistance , which highlights the need for updated data on antimicrobial susceptibility in different regions and countries.

Therefore, the purpose of this study was to characterize current infectious profile and antimicrobial resistance in pediatric chronic rhinosinusitis for a 6-year period.

2

Materials and methods

A retrospective review of children with community-acquired rhinosinusitis undergoing a maxillary sinus puncture was conducted at the Chung Shan Medical University Hospital, Taichung, Taiwan, from January 2001 to December 2006. Patients were included if they presented with typical symptoms of rhinosinusitis (purulent nasal drainage/postnasal discharge and nasal congestion) lasting more than 12 weeks. All of them received adequate antimicrobial therapy previously and showed limited improvement in nasal symptoms. Careful ear, nose, and throat examination revealed purulence either within the nasal cavities or along the posterior wall of the oropharynx. The diagnosis of rhinosinusitis was aided by consistent radiographic abnormalities (sinus clouding or air-fluid level) and preoperative endoscopic findings, such as purulence or mucosa swelling in the middle meatus. There was no restriction on the interval from the antibiotic therapy to maxillary sinus puncture. Patients with systemic diseases or prior nasal surgery were excluded. This study was approved and accorded with the standards of the ethics committee at Chung Shan Medical University.

A maxillary sinus puncture was done to the patients, with an attempt to irrigate their sinuses and collect purulent discharge for bacterial cultivation. For younger children, the procedure was performed in an operating room under general anesthesia. For older children or those who could tolerate the procedure, a sinus puncture was done in the outpatient setting under local anesthesia. Sterile gauzes drenched in solution containing 1:100 000 epinephrine and 10% lidocaine were used for decongestion and topical anesthesia. The nostrils and portal of puncture were disinfected with povidone-iodine and 75% alcohol. The maxillary sinus was then tapped by a sinus trocar through the lateral wall of the inferior meatus, followed by aspiration of sinus contents into a 15-mL syringe. If aspiration failed to yield any secretion, the needle was held in place and sterile saline was injected into the sinus and aspirated for collection of pathologic secretions. After successful sampling, saline irrigation was done to achieve complete washout of the antrum contents. Samples from the sinus puncture were sent to the microbiologic laboratory within 1 hour.

In the microbiology laboratory, the aerobic specimens were plated on blood agar plate, eosin methylene blue agar, and chocolate agar, and cultured for 24 hours at 35°C in an incubator containing 5% CO ₂ . Anaerobic cultivation was performed using a blood agar plate agar and incubated anaerobically (10% CO ₂ + 5% H ₂ + 85% N ₂ ). The plates were examined for growth of bacterial colonies at 48 hours of incubation. Potentially pathogenic organisms that grew on culture were identified and reported semiquantitatively by standard techniques.

Analysis of the patterns of antimicrobial resistance was conducted for specific antibiotics according to different aerobic bacteria by disk diffusion test at 35°C for 18 to 24 hours. Antibiotic resistance of Staphylococcus aureus was tested by disk diffusion for vancomycin (Becton, Dickinson and Company, Franklin Lakes, NJ), whereas that of Streptococcus pneumoniae was by E-test for penicillin (AB Biodisk, Solna, Sweden) and by disk diffusion for clindamycin, erythromycin, and co-trimoxazole (Becton, Dickinson and Company). Antibiotic susceptibility testing for Haemophilus influenzae was done using disk diffusion for ampicillin, co-trimoxazole, co-amoxiclav, cefuroxime, and ciprofloxacin (Becton, Dickinson and Company). Resistance breakpoints for minimum inhibitory concentrations (MICs) were determined using the criteria approved by the National Committee for Clinical Laboratory Standards . β -Lactamase testing of H influenzae and Moraxella catarrhalis isolates was done using the Cefinase test (Becton, Dickinson and Company).

To investigate the trends in antimicrobial resistance of pathogenic organisms recovered from pediatric chronic rhinosinusitis, we divided the study time into 2 periods. The earlier period was from 2001 to 2003 and the latter period from 2004 to 2006. Comparisons of antimicrobial resistance between these 2 periods were made to determine if there was a temporal increase in antibiotic resistance.

χ ² and Fisher exact tests were the statistical analyses used to assess differences in resistance rates of individual antibiotics in each organism over the study period.

2

Materials and methods

A retrospective review of children with community-acquired rhinosinusitis undergoing a maxillary sinus puncture was conducted at the Chung Shan Medical University Hospital, Taichung, Taiwan, from January 2001 to December 2006. Patients were included if they presented with typical symptoms of rhinosinusitis (purulent nasal drainage/postnasal discharge and nasal congestion) lasting more than 12 weeks. All of them received adequate antimicrobial therapy previously and showed limited improvement in nasal symptoms. Careful ear, nose, and throat examination revealed purulence either within the nasal cavities or along the posterior wall of the oropharynx. The diagnosis of rhinosinusitis was aided by consistent radiographic abnormalities (sinus clouding or air-fluid level) and preoperative endoscopic findings, such as purulence or mucosa swelling in the middle meatus. There was no restriction on the interval from the antibiotic therapy to maxillary sinus puncture. Patients with systemic diseases or prior nasal surgery were excluded. This study was approved and accorded with the standards of the ethics committee at Chung Shan Medical University.

A maxillary sinus puncture was done to the patients, with an attempt to irrigate their sinuses and collect purulent discharge for bacterial cultivation. For younger children, the procedure was performed in an operating room under general anesthesia. For older children or those who could tolerate the procedure, a sinus puncture was done in the outpatient setting under local anesthesia. Sterile gauzes drenched in solution containing 1:100 000 epinephrine and 10% lidocaine were used for decongestion and topical anesthesia. The nostrils and portal of puncture were disinfected with povidone-iodine and 75% alcohol. The maxillary sinus was then tapped by a sinus trocar through the lateral wall of the inferior meatus, followed by aspiration of sinus contents into a 15-mL syringe. If aspiration failed to yield any secretion, the needle was held in place and sterile saline was injected into the sinus and aspirated for collection of pathologic secretions. After successful sampling, saline irrigation was done to achieve complete washout of the antrum contents. Samples from the sinus puncture were sent to the microbiologic laboratory within 1 hour.

In the microbiology laboratory, the aerobic specimens were plated on blood agar plate, eosin methylene blue agar, and chocolate agar, and cultured for 24 hours at 35°C in an incubator containing 5% CO ₂ . Anaerobic cultivation was performed using a blood agar plate agar and incubated anaerobically (10% CO ₂ + 5% H ₂ + 85% N ₂ ). The plates were examined for growth of bacterial colonies at 48 hours of incubation. Potentially pathogenic organisms that grew on culture were identified and reported semiquantitatively by standard techniques.

Analysis of the patterns of antimicrobial resistance was conducted for specific antibiotics according to different aerobic bacteria by disk diffusion test at 35°C for 18 to 24 hours. Antibiotic resistance of Staphylococcus aureus was tested by disk diffusion for vancomycin (Becton, Dickinson and Company, Franklin Lakes, NJ), whereas that of Streptococcus pneumoniae was by E-test for penicillin (AB Biodisk, Solna, Sweden) and by disk diffusion for clindamycin, erythromycin, and co-trimoxazole (Becton, Dickinson and Company). Antibiotic susceptibility testing for Haemophilus influenzae was done using disk diffusion for ampicillin, co-trimoxazole, co-amoxiclav, cefuroxime, and ciprofloxacin (Becton, Dickinson and Company). Resistance breakpoints for minimum inhibitory concentrations (MICs) were determined using the criteria approved by the National Committee for Clinical Laboratory Standards . β -Lactamase testing of H influenzae and Moraxella catarrhalis isolates was done using the Cefinase test (Becton, Dickinson and Company).

To investigate the trends in antimicrobial resistance of pathogenic organisms recovered from pediatric chronic rhinosinusitis, we divided the study time into 2 periods. The earlier period was from 2001 to 2003 and the latter period from 2004 to 2006. Comparisons of antimicrobial resistance between these 2 periods were made to determine if there was a temporal increase in antibiotic resistance.

χ ² and Fisher exact tests were the statistical analyses used to assess differences in resistance rates of individual antibiotics in each organism over the study period.