Normal oropharyngeal flora consists of a variety of aerobes such as Streptococcus viridans,Neisseria spp.and anaerobes most prominently Peptostreptococci.Abnormal oropharyngeal flora composes opportunistic aerobic Gram-negative bacilli(AGNB) such as Haemophilus influenzae, Escherichia coli,Klebsiella spp.and yeast,e.g.Candida spp..Carriage of abnormal oropharyngeal flora appears in elderly,underlying diseases or seriously ill individuals.The elderly have an increased incidence of oropharyngeal colonization with respiratory pathogens.Changes in the oral milieu may occur secondary to decreased salivary production and abnormalities in swallowing.The decrease of immune function and impaired clearance of organisms cause the elderly have an increased incidence of oropharyngeal bacterial colonization,a well-known risk factor for the development of pneumonia.As oropharyngeal AGNB colonization can be associated with infections such as aspiration pneumonia,it is very important to know the bacterial species carried in oropharyngeal and their antimicrobial susceptibilities for making treatment strategies and for decreasing of mortality and costs of elderly pneumonia.A prospective study was undertaken in a population of 105 hospitalized and 501 non-hospitalized elderly to investigate the oropharyngeal bacterial carriage and the bacterial resistance profile,and to analyze the risk factors for the bacterial carriage.Comparison of oropharyngeal bacterial carriage in the hospitalized and non-hospitalized elderly was also performed.The produce of extended-spectrumβ-lactamases(ESBLs) and AmpCβ-lactamases,the major mechanisms of bacterial resistance toβ-lactam antibiotics in gram-negative bacilli,was also investigated. Part 1 Oropharyngeal bacterial carriage in elderly peopleObjective To investigate the oropharyngeal bacterial carriage in the hospitalized and non-hospitalized elderly and the bacterial resistance profile, and to analyze the risk factors for the bacterial carriage.Methods 105 hospitalized and 501 non-hospitalized elderly without acute infections were enrolled in this study.An oropharyngeal swab was taken from each elderly after they rinsed their mouths with sterile saline.Bacteria were cultured and identified with routine methods and the antimicrobial susceptibility testing was carried out with disk diffusion method.Results The oropharyngeal bacterial carriage rate was 55.2%(58/105) in the hospitalized elderly patients.62 pathogens were isolated including 56 strains of Gram-negative bacilli which was 90.3%of all bacteria,5(8.1%) Gram-positive cocci and 1 Candida albicans(1.6%).The oropharyngeal bacterial carriage rate was 32.1%(161/501) in non-hospitalized elderly.161 bacteria were isolated including 147 strains of Gram-negative bacilli which was 91.3%of all bacteria,14(8.7%) strains of Gram-positive cocci.Haemophilus spp.strains were the most common bacteria carried in oropharyngeal.Among Gram-negative bacilli,60.7%and 66.7%were Haemophilus spp.in the hospitalized elderly and non-hospitalized elderly, respectively.All of Haemophilus spp.strains were susceptible to antimicrobials tested.There were no significant difference in the rates of antibiotic sensitivity between strains isolated from hospitalized and from non-hospitalized elderly(P＞0.05).Ten strains of Klebsiella pneumoniae were isolated from hospitalized elderly.The antibiotic susceptibility rate was 60%to piperacillin,cefotaxime, gentamicin or amikacin,4 strains with extended-spectrumβ-lactamase positive were resistant to all above 4 antimicrobials.40 strains of K.pneumoniae isolated from non-hospitalized elderly were susceptible to different antibiotics (95%～100%).The susceptible rates of K.pneumoniae strains from the hospitalized elderly were higher than that from the non-hospitalized elderly for most antimicrobials tested except ciprofloxacin(P＜0.05).All of the elderly no matter in hospitalization or not had more than one basic diseases such as coronary heart disease,diabetes,malignant tumor,or central nervous system diseases.Hospitalized elderly had a higher frequency to have coronary heart disease,central nervous system diseases and malignant tumor than that in the non-hospitalized elderly(P＜0.05).Hospitalized elderly had a higher frequency to use chemotherapy,steroid and antibiotics within four weeks than that in the non-hospitalized elderly(P＜0.05).Denture-wearing rates were 72.4%and 48.9%in oropharyngeal bacterial carriage group and none carriage group in hospitalized elderly,respectively.The corresponding rates were 69.9%and 52.1%in non-hospitalized elderly population, respectively.Logistic analysis indicated that denture-wearing was the risk factor for the oropharyngeal bacterial carriage in both of the hospitalized and non-hospitalized elderly populations(P＜0.05).Conclusions Oropharyngeal bacterial carriage rates were very high in elderly, and the carriage rate was higher in the hospitalized elderly than that of the non-hospitalized elderly.The major colonized bacteria were Gram-negative bacilli.Denture-wearing was one of the risk factor for the oropharyngeal bacterial carriage in elderly. Part 2 Study on Extended-Spectrumβ-Lactamases and AmpC Enzymes in Gram-negative Bacilli Isolated from ElderlyThe production of extended-spectrumβ-lactamases(ESBLs) is the most common mechanism of resistance to the third generation cephalosporins in Enterobacteriaceae bacteria,especially E.coli and K.pneumoniae.Infections caused by ESBLs and AmpC producing bacteria are associated with less cure rate and higher cost than antiboitic-sensitive bacterial infections.According to several reports,the genotypes of ESBLs are different over the world.But the genotypes of plasmid-mediated AmpC enzymes are similar,mainly DHA-1,followed by CMY-2 AmpC.Objective To investigate ESBLs and AmpC producing rates and their genotypes in E.coli and K.pneumoniae strains isolated from elderly patients in Huashan Hospital in 2005.Methods Double disk confirmation testing was used for detection of ESBLs in E.coli and K.pneumoniae as recommended by CLSI.PCR was used to detect the genotype of CTX-M and AmpC enzymes.PCR products of ESBLs randomizedly selected and all AmpC were used to do DNA sequence.Results Among 246 K.pneumoniae strains from elderly in Huashan Hospital, 68.7%(169/246) produced ESBLs and 1.6%(4/246) produced AmpC,and of 231 E.coli,67.1%(155/231) produced ESBLs and 3.9%(9/231) produced AmpC.Of 169 ESBLs positive strains of K.pneumoniae,140(82.8%) had genotype of CTX-M,and 112 of 155 strains(72.3%) of ESBLs positive E.coli were CTX-M.Sequences of 50 PCR products(28 from K.pneumoniae and 22 from E. coli) showed that all were belonged to CTX-M-14 type ESBLs except one CTX-M-65.All 4 AmpCβ-lactamases from K.pneumoniae were belonged to DHA-1 type,and all 9 E.coli AmpCβ-lactamases were CMY-2 type.Conclusions ESBLs-producing rates in E.coli and K.pneumoniae strains isolated from elderly patients were pretty high.The main genotype of ESBLs was CTX-M.AmpCβ-lactamases produced in less than 4%of strains K. pneumoniae and E.coli with the major genotypes of CMY-2 and DHA-1.It was important to do sputum bacterial culture and to choose susceptible antimicrobials for the treatment of pneumonia in elderly.