Bacterial Culture Of Surgical Specimens From Patients With Chronic Rhinosinusitis

ObjectiveChronic rhinosinusitis(CRS) is a common disease characterized by mucosal inflammation of nasal cavity and sinuses. It is generally considered that rhinosinusitis is not simply an infectious disease but a complex and multifactorial disorder. Factors associated with the disease may be (bacterial, fungal or viral) infection, anatomic variation of ostiomeatal complex, allergy, mucociliary impairment of mucosa, and so on. The role of bacterial infection in acute rhinosinusitis has already been determined. Even so the contribution of bacteria to development of CRS has not been identified while broad-spectrum antibiotics are usually administered to patients with CRS preoperatively.With widespread use of antibiotics, attention has been paid to the emergence of antibiotic-resistant mutants among bacteria. Beta-lactamase has been induced in Staphylococcus, Streptococcus pneumoniae and Hemophilus influenzae species, and extended-spectrum beta-lactamase has been induced in Escherichia coli and Klebsiella pneumoniae species. These bacteria are resistant to penicillins and some other beta-lactam antibiotics. In addition, methicillin-resistant Staphylococci (MRS) are characterized by resistance to all beta-lactam antibiotics.In the present study, patients with CRS were evaluated microbiologically by using surgical specimens of the anterior ethmoid sinus mucosa near the ostium of the maxillary sinus. Bacterial cultures for aerobes and anaerobes were performed on 134 specimens from 67 patients. Beta-lactamase-producing bacteria (P-LPB), extended-spectrum beta-lactamase-producing bacteria and MRS were detected, and antibiotic susceptibility test was carried out according to the recommendation of Clinical and Laboratory Standards Institute (CLSI). The purpose of the present study was to characterize the aerobic and anaerobic flora of patients with CRS and to evaluate antibiotic resistance of clinical isolates. Materials and Methods1. PatientsA total of 67 patients with CRS who underwent endoscopic sinus surgery were enrolled during the period between October 2005 and January 2008 in department of otolaryngology of the Central Hospital, Jinhua. According to standard classification (ESS-1997, Haikou), these 67 cases of CRS were classified as stageⅡ-Ⅱ(n=51), stageⅡ-Ⅲ(n=7), and stageⅢ(n=9). All patients received antibiotic treatment before the surgery.2. Specimen collectionThe specimens of the anterior ethmoid sinus mucosa near the ostium of the maxillary sinus were inoculated onto a plate with anaerobic blood agar with plate streak method. The plate was then closed into a GENbag with GENbag anaer. Other specimens were obtained and placed into a sterile cube. Both the GENbag and the sterile cube were referred to the laboratory within half an hour.3. Culture and identificationSpecimens in the sterile cube were respectively inoculated with plate streak method onto a plate with 5% sheep blood agar, a plate with McConkey agar and a plate with chocolate agar. These plates were incubated at 35℃in an atmosphere containing 5% carbon dioxide and examined at 18 and 24 hours. The GENbag was also incubated at 35℃in an atmosphere containing 5% carbon dioxide and examined at 48 hours.Bacterioscopic examination for pathogen was carried out using the Gram dye, catalase test or oxidase test. According to the result of examination, pathogen was identified by Vitek AutoMicrobic System to species level. According to the recommendation of CLSI, nitrocefin disks were used to test the beta-lactamase of isolates, and the combined disk method (cefotaxime and cefotaxime -clavulanic acid disks, or ceftazidime and ceftazidime-clavulanic acid disks) was used to confirm the presence of extended-spectrum beta-lactamase of isolates. Cefoxitin disks were used to detect methicillin resistance in Staphylococci.4. Antibiotic susceptibility testAntibiotic susceptibility test discs were chosen based on the recommendation of CLSI-2005 and clinical custom of antibiotic therapy. Antibiotic susceptibility test was determined by Kirby-Bauer's disc diffusion method according to criteria recommended by CLSI-2005. Antibiotic susceptibility test for Hemophilus influenzae was guided by the procedure of Hemophilus influenzae test strips. Results1.Results of culture and identificationA total of 40 isolates were obtained from 134 specimens, including 38 aerobic isolates (95%) and 2 anaerobic isolates (5%). Only one species of aerobic organisms were found in 36 patients. Only one species of anaerobic organisms were found in 2 patients. Tow species of aerobic organisms was found in 1 patient. The positive rate was 58.2%(39/67).The predominant species of gram-positive aerobic bacteria were coagulase-negative staphylococci (95.2%) (Table 1).Table 1 Gram-positive aerobic bacteria isolated from Specimens The predominant species of gram-negative aerobic bacteria were Enteric bacilli (88.2%) (Table 2).Table 2 Gram-negative aerobic bacteria isolated from SpecimensOne isolate of Peptostreptococcus prevotii and 1 isolate of Fusobacterium nucleatum were identified (Table 3).Table 3 Anaerobic bacteria isolated from Specimens There were 15 isolates of MRS (71.4%) in Staphylococci (Table 4).Table 4 Staphylococci and MRS isolated from SpecimensThere were 20 isolates ofβ-LPB (95.2%) in Staphylococci (Table 5).Table 5 Staphylococci andβ-LPB isolated from Specimens 2. Results of antibiotic susceptibility testVancomycin and rifampicin were highly effective against Staphylococci in vitro (Table 6).Table 6 Antibiotic susceptibility of StaphylococciImipenem, cefepime, ceftazidime and gentamycin were highly effective against Enteric bacilli in vitro (Table 7).Table 7 Antibiotic susceptibility of Enteric bacilli Conclusion1.All of bacterial isolates of specimens from patients with CRS belong to normal microflora of nasal cavity and most of them are opportunistic pathogens. Therefore, infection of a pathogen does not play an important role in development of CRS.2.Attention should be paid to the high percentage of P-LPB and MRS in Staphylococci isolated from patients with CRS. Overuse of antibiotics for patients with CRS should avoid.