| Bacterial meningitis has always been a big threat to human life. In recent years, with medical science continuously progressing, broad-spectrum antibiotics are widely used, and advanced neurosurgery and invasive procedures are frequently implemented, as a result, the incidence of nosocomial bacterial meningitis has risen remarkably, which lead to the change of the pathogenic bacteria spectrum of bacterial meningitis. Gram-negative bacteria, especially Acinetobacter spp. and Klebsiella spp. has become the major cause of nosocomial bacterial meningitis. In recent years, the emergence of antibiotic resistance has become a major problem in the field of antimicrobial treatment, carbapenem-resistant strains appeared and started to spread, and the treatment of bacterial meningitis is forced into a new dangerous position.Nosocomial bacterial meningitis is a severe kind of hospital-acquired infection, which may result from neurosurgery and invasive procedures(e.g placement of external ventricular catheters, lumbar puncture, or spinal anesthesia), and mortality rate is as high as 35%. Currently, diagnosis of bacterial meningitis still relies on cultures of cerebrospinal fluid. However, pathogenic diagnosis is hard to reach, as the culture of bacteria relies on careful operation to a large extent, and empirical use of antibiotic agents are recommended. A research analysed 2031 cerebrospinal fluid specimen from patients who are clinically diagnosed as bacterial meningitis, and result shows that the positive rate of bacterial culture is 3.1%. The most common bacteria that cause bacterial meningitis are Acinetobacter spp., Klebsiella spp., Staphylococcus spp. and pseudomonas aeruginosa, among which Acinetobacter spp. and Klebsiella spp. are the most important pathogenic bacteria because of the high resistant rate. Risk factors of nosocomial bacterial meningitis include neurosurgery, external ventricular drainage and cerebrospinal fluid leakage.The incidence of nosocomial meningitis is low. Research shows incidence rate of nosocomial meningitis after craniotomy ranges from 0.8%to 1.5%. Currently, there are few domestic reports on distribution and antibiotic resistance of pathogens of bacterial meningitis, and clinical research on nosocomial meningitis are also limited. Huashan Hospital is a tertiary care hospital in Shanghai, and the department of neurosurgery is one of the key disciplinary areas, the amount of operations of one year is over 15,000, which makes the study on nosocomial meningitis possible.In this study, we collected all the strains isolated from cerebrospinal fluid in Huashan Hospital during the year 2004-2013, to learn about distribution and prevalence of antimicrobial susceptibility in isolates from cerebrospinal fluid specimens in Huashan hospital. Then we collected and analysed the medical history of the patients with bacterial meningitis, to learn about clinical characteristics and risk factors of bacterial meningitis. The study includes the following three parts:Part 1 Distribution and prevalence of antimicrobial susceptibility in isolates from cerebrospinal fluid specimens in Huashan hospital,2004-2013.To learn about distribution and prevalence of antimicrobial susceptibility in isolates from cerebrospinal fluid specimens in Huashan hospital, We collected all the strains isolated from cerebrospinal fluid in Huashan hospital during the period of 2004-2013.Distribution of the cerebrospinal fluid isolates was analysed and the minimum inhibitory concentration of 20 kinds of antimicrobial drugs to all the strains was detected using the agar dilution method according to the 2013 updated version of the CLSI(Clinical and Laboratory Standard Institute) files.According to the record, a total number of 526 strains were isolated from cerebrospinal fluid in Huashan hospital during the ten years, among which 97.8% cases were hospital-acquired infection.The 526 isolates are consisted of 189(35.9%) gram-positive stains and 337(64.1%) gram-negative strains. The most frequent isolates are Acinetobacter spp., coagulase negative staphylococcus, Klebsiella spp., Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus spp. During the ten years, the frequency of Klebsiella spp. remarkably rises, while the frequency of Acinetobacter spp. rises around the year 2009, then shows a decending trend in recent years, and the frequency of Pseudomonas aeruginosa shows an overall decending trend.In the rest part of the study, we mainly worked on gram-negative bacteria for two reasons, first, among gram-positive bacteria, the constituent ratio of coagulase negative staphylococcus is 61.4%(189/526), but there’s possibility that the specimen is contaminated. Secondly, according to the results of disk diffusion, the distribution and antibiotic resistance of gram-positive bacteria isolated from cerebrospinal fluid showed no obvious change over the ten years.In this study, a total number of 267 gram-negative strains were collected(70 strains were lost or dead), including 97 strains of Enterobacteriaceae and 170 non-fermentative strains. Enterobacteriaceae are consisted of 68 strains of Klebsiella spp.,14 strains of Escherichia coli and 15 other strains. Non-fermentative strains are consisted of 125 strains of Acinetobacter spp.,25 strains of Pseudomonas aeruginosa and 14 strains of Pseudomonas maltophilia.Results of antimicrobial susceptibility test shows that the strains of Enterobacteriaceae present low susceptibility rates to the 3 rd and 4th generation of cephalosporins, while the susceptibility rates to carbapenems differ from one species to another. Klebsiella spp. are frequently resistant to carbapenems, the susceptibility rates to imipenem and meropenem are 63.2% and 66.2% separately. Susceptibility rates of Klebsiella spp. to carbapenem decreased remarkably during the ten years. Most of Escherichia coli and other strains of Enterobacteriaceae remain susceptible to carbapenems. Most of the strains of Enterobacteriaceae are susceptible to tigecycline. Among non-fermentative strains, the susceptible rates of Acinetobacter spp. to all kinds of antimicrobial agents, including carbapenems, are high, the susceptible rate to imipenem and meropenem are 49.6% and 52.8% separately. Susceptibility rates of Acinetobacter spp. to carbapenems also decreased remarkably during the ten years. Most strains of Pseudomonas aeruginosa are susceptible to β-lactamase inhibitors, amikacin, and ciprofloxacin, the susceptible rate to imipenem and meropenem are 52.0% and 88.0% separately. The emergence of resistant strains of Acinetobacter spp. and Klebsiella spp. is a major problem in antimicrobial therapy.Part Two β-lactamase production and homology analysis of Acinetobacter spp. and Klebsiella spp. isolated from cerebrospinal fluid.According to the results in part one, Acinetobacter spp. and Klebsiella spp. are the most frequent bacteria isolated from cerebrospinal fluid. In this study, we found that the susceptible rates of Acinetobacter spp. and Klebsiella spp. isolated from cerebrospinal fluid to carbapenems and the 3rd and 4th generation of cephalosporins are low.Acinetobacter spp. and Klebsiella spp. possess a wide array of (3-lactamases that hydrolyze and confer resistance to penicillins, cephalosporins, and carbapenems,which is one of the major mechanisms of resistance in the two species. To learn about P-lactamase production in the strains isolated from cerebrospinal fluid, we detected P-lactamase gene in the 62 carbapenem-nonsusceptible strains of Acinetobacter spp. and 68 strains of Klebsiella spp. (including 30 carbapenem-nonsusceptible strains) by PCR method. Result shows that Acinetobacter spp. mainly produce OXA type carbapenemases,82.3% strains produce OXA-23-like carbapenemases, and some of the other strains produce OXA-24-like and OXA-58-like carbapenemases. We also detected 2 strains producing NDM-1 metallo-P-lactamase and 1 strain producing SIM metallo-β-lactamase. Among the 68 strains of Klebsiella spp., CTX-M type is the major ESBLs type,19.1% strains produce CTX-M-group9 type ESBLs, which is the most frequent ESBLs type, and 11.8% strains produce CTX-M-groupl type ESBLs. In 7.4% strains, plasmid-borne AmpC gene were detected. Among 30 carbapenem-nonsusceptible strains,76.7% strains produce KPC-2 type carbapenemase.In this study, we also found that the frequency of Acinetobacter spp. rised before the year 2009 and reach the top in 2009, while the frequency of Klebsiella spp. kept rising in the past two years. To learn whether this phenomenon is caused by the spread of a single clone, we analysed homology of the two species. For Acinetobacter spp., we conducted ERIC PCR to analyse all the 93 isolates of Acinetobacter baumanii, then we analysed all the strains of Acinetobacter spp. that are separated during 2007 to 2009 by the method of PFGE. For Klebsiella spp., we analysed all the 63 strains of Klebsiella pneumoniae by the method of MLST. Result shows that all the 93 strains of Acinetobacter baumanii are divided into 6 type by ERIC PCR, A, B, and C type are the major type, the frequency are 60.2%,17.2% and 11.8% separately. The result of PFGE shows that the 31 strains of Acinetobacter baumanii that are collected during 2007-2009 are divided into 23 different PFGE-DNA type,9 strains of Acinetobacter calcoaceticus are divided into 8 PFGE-DNA type, and 5 strains of Acinetobacter lwoffii are of 5 different PFGE-DNA type, no evidence for single clone spreading were detected. MLST result for Klebsiella pneumoniae shows that the frequency of ST-11 type rised remarkably during 2010-2013, and this type account for 43.5% of all the 23 strains of Klebsiella pneumoniae that are separated during the year 2012 and 2013, which indicates the possibility of a single clone spreading in the ward.Part Three Studies on infections of the central nervous system caused by Acinetobacter baumanii and Klebsiella pneumoniaeNosocomial bacterial meningitis is a severe kind of hospital-acquired infection, and the major pathogen are different from community-acquired meningitis. In this study, Acinetobacter baumanii and Klebsiella pneumoniae are recognized as the most important pathogen of nosocomial bacterial meningitis for their high frequency in cerebrospinal fluid isolates, which is 45.1% and 22.8% separately.To learn about clinical characteristics and risk factors of nosocomial bacterial meningitis caused by Acinetobacter baumanii and Klebsiella pneumoniae, we collected the medical history of 105 patients with meningitis caused by Acinetobacter baumanii, including 59 cases of carbapenem-resistant;Acinetobacter baumanii(CRAB) infection and 46 cases of carbapenem-susceptible Acinetobacter baumanii(CSAB) infection, and 54 patients with meningitis caused by Klebsiella pneumoniae, including 24 cases of carbapenem-resistant Klebsiella pneumoniae infection and 30 cases of carbapenem-susceptible Klebsiella pneumoniae infection. We analysed the general condition and infection associated condition of the patients, and conducted two case-control studie separately to learn about risk factors of nosocomial bacterial meningitis caused by Acinetobacter baumanii and Klebsiella pneumoniae separately.Result shows that most of the 105 patients with Acinetobacter baumanii infection and 54 patients with Klebsiella pneumoniae infection are from the department of neurosurgery, the proportion are 72.3% and 81.5% separately, and ICU patients occupy 11.4% and 9.3% separately. Most of the patients have accepted neurosurgery. Among the 105 patients with Acinetobacter baumanii infection, 56.2%(59/105) are effectively treated,20.0%(21/105) are cured, and 13.3% (14/105) are dead during hospitalization. Among the 54 patients with Klebsiella pneumoniae infection,75.9%(41/54) are effectively treated,37.3%(20/54) are cured, and 9.3%(5/54) are dead during hospitalization.The 59 patients with CRAB infection and the 46 patients with CSAB infection show no significant difference in clinical manifestation. As for prognosis,44.1% (26/59)patients with CRAB infection are effectively treated, and the number is significantly lower than that of CSAB group, which is 71.7%(33/46) (P=0.005).10.2%(6/59) patients with CRAB infection are cured, which is also significantly lower than the 30.4%(14/46) of CSAB group. The 24 patients with carbapenem-resistant Klebsiella pneumoniae infection show no significant difference in clinical manifestation and prognosis compared with the 30 patients with carbapenem-susceptible Klebsiella pneumoniae infection.The result of the case-control study shows that indepent risk factors of nosocomial bacterial meningitis caused by Acinetobacter baumanii include external ventricular drainage (P=0.002), the frequency of neurogery (P=0.000) and general anaesthesia (P=0.004), and the incision of trachea (P=0.001). Indepent risk factors of nosocomial bacterial meningitis caused by CRAB include the usage of carbapenems before isolation (.P=0.001), the usage of proton pump inhibitor (P=0.008), the incision of trachea (P=0.026) and prophase hospitalization history (P=0.009). Indepent risk factors of nosocomial bacterial meningitis caused by Klebsiella pneumoniae include external ventricular drainage (P=0.001) and the placement of intravenous catheter (P=0.036). Indepent risk factors of nosocomial bacterial meningitis caused by carbapenem-resistant Klebsiella pneumoniae include the usage of carbapenems before isolation (P=0.003), the incision of trachea (P=0.014) and prophase hospitalization history (P=0.029)... |
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