Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy

The molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy was studied in a five-month period in 1996, during which all S. aureus isolated were collected. All MRSA isolates (95) and a sample of methicillin-susceptible S. aureus (20) were typed with a variety of phenotypic and genotypic methods. Clonal identities were determined by pulsed-field gel electrophoresis (PFGE) of chromosomal SmaI digests and, for MRSA isolates, by probing ClaI digests with a mecA probe and a Tn554 probe. Overall, MRSA represented 32.3% of all isolates, with very high percentages from the intensive care units (adult and neonatal). PFGE after restriction with SmaI resolved genomic DNA of 95 MRSA strains into 26 major PFGE patterns. The use of southern blot hybridization of ClaI genomic digests with mecA and Tn554 allowed us a significant increase in discrimination, differentiating at least 32 different clones. Two major clones, however, each sharing common ClaI-mecA and Tn554 type and PFGE pattern as well as a common resistance phenotype, represented more than 50% of all MRSA isolates. The recovery of these two clones in the majority of the isolates of adult and neonatal intensive care units, respectively, is indicative of typical nosocomial outbreaks and clonal spread. It is concluded that intensive care units are major areas requiring preventative interventions.     

Methicillin-resistant Staphylococcus aureus ST30-SCCmec IVc clone as the major cause of community-acquired invasive infections in Argentina

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA to evaluate clinical features and genotype of strains causing invasive infections in Argentina. A total of 55 patients with invasive CA-MRSA infections were included. Most patients (60%) had bloodstream infections, 42% required admission to intensive care unit and 16% died. No CA-MRSA isolates were multiresistant (resistant ⩾3 classes of antibiotics). All isolates carried Panton-Valentine leukocidin (PVL) genes and staphylococcal cassette chromosome (SCCmec) type IV. The majority CA-MRSA strains belonged to ST30 and had identical pulsed-field gel electrophoresis (PFGE) patterns, qualifying as a clonal dissemination of a highly transmissible strain. The main clone recovered from patients with CA-MRSA invasive infections was genotyped as pulsed-field gel electrophoresis type C-ST30, SCCmec type IVc-spa type 019, PVL positive. It has become predominant and replaced the previously described CA-MRSA clone (PFGE type A, ST5, SCCmec type IV, spa type 311).     

Investigation of classical epidemiological links between patients harbouring identical, non-predominant meticillin-resistant Staphylococcus aureus genotypes and lessons for epidemiological tracking

According to molecular epidemiology theory, two isolates belong to the same chain of transmission if they are similar according to a highly discriminatory molecular typing method. This has been demonstrated in outbreaks, but is rarely studied in endemic situations. Person-to-person transmission cannot be established when isolates of meticillin-resistant Staphylococcus aureus (MRSA) belong to endemically predominant genotypes. By contrast, isolates of infrequent genotypes might be more suitable for epidemiological tracking. The objective of the present study was to determine, in newly identified patients harbouring non-predominant MRSA genotypes, whether putative epidemiological links inferred from molecular typing could replace classical epidemiology in the context of a regional surveillance programme. MRSA genotypes were defined using double-locus sequence typing (DLST) combining clfB and spa genes. A total of 1,268 non-repetitive MRSA isolates recovered between 2005 and 2006 in Western Switzerland were typed: 897 isolates (71%) belonged to four predominant genotypes, 231 (18%) to 55 non-predominant genotypes, and 140 (11%) were unique. Obvious epidemiological links were found in only 106/231 (46%) patients carrying isolates with non-predominant genotypes suggesting that molecular surveillance identified twice as many clusters as those that may have been suspected with classical epidemiological links. However, not all of these molecular clusters represented person-to-person transmission. Thus, molecular typing cannot replace classical epidemiology but is complementary. A prospective surveillance of MRSA genotypes could help to target epidemiological tracking in order to recognise new risk factors in hospital and community settings, or emergence of new epidemic clones.     

Safety,immunogenicity, and efficacy of NDV-3A against Staphylococcus aureus colonization: A phase 2 vaccine trial among US Army Infantry trainees

BackgroundMilitary trainees are at increased risk for Staphylococcus aureus colonization and infection. Disease prevention strategies are needed, but a S. aureus vaccine does not currently exist.MethodsWe enrolled US Army Infantry trainees (Fort Benning, GA) in a phase 2, randomized, double-blind, placebo-controlled trial of NDV-3A, a vaccine containing a recombinant adhesin/invasion protein of Candida albicans that has structural similarity to the S. aureus protein clumping factor A. Study participants received one intramuscular dose of NDV-3A or placebo (adjuvant alone) within 72 h of arrival on base. Longitudinal nasal and oral (throat) swabs were collected throughout the 14-week Infantry training cycle. Safety, immunogenicity, and efficacy of NDV-3A against S. aureus nasal / oral acquisition were the endpoints.ResultsThe NDV-3A candidate had minimal reactogenicity and elicited robust antigen-specific B- and T-cell responses. During the 56-day post-vaccination period, there was no difference in the incidence of S. aureus nasal acquisition between those who were randomized to receive NDV-3A vs. placebo (25.6% vs. 29.1%; vaccine efficacy [VE]: 12.1%; p = 0.31). In time-to-event analysis, there was no difference between study groups with respect to the S. aureus colonization-free interval (VE: 13%; p = 0.29). Similarly, the efficacy of NDV-3A against S. aureus oral acquisition was poor (VE: 2.4%; p = 0.52).ConclusionsA single dose of NDV-3A did not prevent nasal nor oral acquisition of S. aureus in a population of military trainees at high risk for colonization.     

金黄色葡萄球菌医院感染的临床及耐药性分析

目的探讨金黄色葡萄球菌所致医院感染的危险因素、临床特点及耐药情况,为临床治疗金黄色葡萄球菌医院感染提供指导。方法收集确诊为金黄色葡萄球菌医院感染病例的临床资料,分析发病的危险因素及临床特点,对分离到的菌株进行药物敏感性测定。结果共73例金黄色葡萄球菌医院感染患者,均存在着严重的基础疾病,82.19%的患者接受过侵入性操作,感染部位以肺部最多见;共分离出79株金黄色葡萄球菌,包括耐甲氧西林金黄色葡萄球菌（MRSA）66株（83.54%）和甲氧西林敏感金黄色葡萄球菌（MSSA）13株（16.46%）;金黄色葡萄球菌对多种抗菌药物呈普遍耐药,而MRSA的耐药性明显高于MSSA（P〈0.01）,未发现对耐万古霉素MRSA菌株。结论金黄色葡萄球菌医院感染常发生在有严重基础疾病、接受侵入性操作的患者,肺部感染最常见,MRSA表现为多药高度耐药,但糖肽类药物敏感性高。     

创伤患者金黄色葡萄球菌感染的分子流行病学研究

目的通过对创伤病房金黄色葡萄球菌(SA)感染的分子流行病学研究,为临床预防和治疗SA感染提供科学依据. 方法收集创伤病房近3年SA培养阳性病例29例,采用多重PCR扩增SA的毒素基因tst和sec,分析毒素基因的存在与发热的关系;通过PCR扩增MRSA基因组稀有限制区旁的DNA序列,对MRSA进行基因分型. 结果 29例患者中,12例为甲氧西林敏感金黄色葡萄球菌(MSSA);17例为耐甲氧西林金黄色葡萄球菌(MRSA);MRSA携带tst和sec基因比率(均为88.2%)显著高于MSSA(分别为33.3%和41.7%, P=0.014);19例伴有发热,其中16例含有tst和sec基因,10例不伴发热,其中4例含tst和sec基因,发热组携带两种基因比率显著高于不发热组(P=0.032);稀有限制区PCR(IRS-PCR)分型表明2001年感染MRSA的10例患者有8例为同种基因型. 结论 tst和sec基因的存在可能与金黄色葡萄球菌引起的发热有关,2001年创伤病房可能存在MRSA暴发流行.     

47株金黄色葡萄球菌临床血流感染分离株的基因分型研究

目的 研究金黄色葡萄球菌临床血流感染分离株的分子流行病学特征.方法 收集2006年1月至2008年12月解放军总医院分离的临床血流感染金黄色葡萄球菌菌株(共47株),标本来源均为患者静脉血.采用琼脂稀释法检测所有菌株对多种抗生素的耐药性,PCR方法 检测pvl毒素基因,DiversiLab~(TM)Rep-PCR分型系统分析菌株的同源性;对耐甲氧西林金黄色葡萄球菌(MRSA)进行葡萄球菌染色体/mec(SCCmec)分型以及ST239型别的快速筛查;综合分型和药敏试验结果,挑选部分代表菌株进行多位点序列分型(MLST).结果 47株血流感染金黄色葡萄球菌中,pvl基因检出率为4.3%.MRSA占51.1%.MRSA均为SCCmec Ⅲ型菌株;Rep-PCR分为A～L共12个型,其中A型为最主要的型,共22株(46.8%),所有的MRSA均属于A、B两型.结论 47株临床血流感染金黄色葡萄球菌中的MRSA绝大部分为多重耐药克隆ST239-MRSA-SCCmecⅢ型.     

Phylogenetic analysis of macrorestriction fragments as a measure of genetic relatedness in Staphylococcus aureus: The epidemiological impact of methicillin resistance

The present study was undertaken for the purpose of defining the epidemiology and genetic relatedness of Staphylococcus aureus strains in a region of Italy by investigating the molecular background for which resistance to methicillin, mediated by the acquisition of another penicillin-binding protein gene, is embedded. Restriction fragment length polymorphism (RFLP) data were used for phylogenetic analyses, since genetic distance values can be used as a general measure of the number of events generating distinct clones. The percentages of methicillin-resistant S. aureus (MRSA) isolates in a six-month period from inpatients and outpatients were, respectively, 12% (22 out of 180) and 0.4% (1 out of 257). On the basis of RFLP obtained after pulsed field gel electrophoresis (PFGE), it was possible to designate isolates as indistinguishable, closely related, possibly related and unrelated. We were able to demonstrate the occurrence of at least five distinct MRSA cross-infection episodes in two hospitals, four involving two patients each and one involving four patients. Phylogenetic analyses overcame the simple pairwise comparison of common bands between strains, and provided a comprehensive epidemiological scenario, identifying three major clusters of MRSA, including different levels of genetic relatedness, while excluding the circulation of a single clone in Italy. Moreover, multidimensional scaling analysis of the obtained genetic distance confirmed that MRSA strains belong to a restricted set of clones, thus demonstrating the relatedness of broad evolutionary lineages within the species S. aureus.     

Staphylococcus aureus native arthritis over 10 years

ObjectivesSeptic arthritis is associated with significant case fatality and morbidity. Staphylococcus aureus is the most common cause of arthritis. We aimed to analyze the microbiological features of S. aureus causing native arthritis and to investigate their influence on the clinical outcome of the infection.Patients and methodsWe conducted a retrospective study including all episodes of S. aureus native arthritis between 2005–2015. Phenotypic (antimicrobial susceptibility, β-hemolysis, agr functionality, biofilm formation) and genotypic characteristics (pulsed-field gel electrophoresis, DNA microarrays) were investigated. The primary endpoint was microbiological failure of treatment, including infection relapse, persistence, or attributable death.ResultsTwenty-nine patients were included (65.5% of men, mean age: 59): seven (24.1%) patients presenting with methicillin-resistant S. aureus (MRSA) native arthritis and 19 with methicillin-susceptible S. aureus (MSSA) native arthritis. Treatment failure occurred in seven (26.9%) patients (4/7 patients [57.1%] among MRSA infections vs. 3/19 [15.8%] among MSSA infections). The persistence rate was similar in MRSA and MSSA infections (1/7 vs. 3/19). However, the case fatality was significantly higher in patients with MRSA infection (3/7 vs. 0/19). The most frequent clonal complex (CC) was CC5 (38.1%). MSSA showed higher genetic variability (nine CCs) versus MRSA (3 CCs).ConclusionsBeyond methicillin resistance, we did not find phenotypic or genotypic factors associated with the poor outcome of S. aureus native arthritis. CC5 was the major CC, showing the higher genetic variability of MSSA versus MRSA.     

A protein A based Staphylococcus aureus vaccine with improved safety

Exposure to Staphylococcus aureus does not lead to immunity as evidenced by the persistent colonization of one third of the human population. S. aureus immune escape is mediated by factors that preempt complement activation, destroy phagocytes, and modify B and T cell responses. One such factor, Staphylococcal protein A (SpA) encompasses five Immunoglobulin binding domains (IgBDs) that associate with the Fcγ domain to block phagocytosis. IgBDs also associate with Fab encoded by V_H3 clan related genes. SpA binding to V_H3-IgM that serves as a B cell receptor results in B cell expansion and secretion of antibodies with no specificity for S. aureus. SpA crosslinking of V_H3-IgG and V_H3-IgE bound to cognate receptors of mast cells and basophils promotes histamine release and anaphylaxis. Earlier work developed a prototype variant SpA_KKAA with four amino acid substitutions in each IgBD. When tested in animal models, SpA_KKAA elicited neutralizing antibodies and protection against infection. We show here that SpA_KKAA retains crosslinking activity for V_H3-IgG and V_H3-IgE. We use a rational approach to design and test 67 new SpA variants for loss of V_H3 binding and anaphylactic activities. We identify two detoxified candidates that elicit SpA-neutralizing antibodies and protect animals from S. aureus colonization and bloodstream infection. The new detoxified SpA candidates bear three instead of four amino acid substitutions thus increasing the development of SpA-specific antibodies. We propose that detoxified SpA variants unable to crosslink V_H3-idiotypic immunoglobulin may be suitably developed as clinical-grade vaccines for safety and efficacy testing in humans.     

Multidrug-Resistant Methicillin-Resistant Staphylococcus aureus Associated with Bacteremia and Monocyte Evasion,Rio de Janeiro,Brazil

We typed 600 methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 51 hospitals in the Rio de Janeiro, Brazil, metropolitan area during 2014–2017. We found that multiple new clonal complex (CC) 5 sequence types had replaced previously dominant MRSA lineages in hospitals. Whole-genome analysis of 208 isolates revealed an emerging sublineage of multidrug-resistant MRSA, sequence type 105, staphylococcal cassette chromosome mec II, spa t002, which we designated the Rio de Janeiro (RdJ) clone. Using molecular clock analysis, we hypothesized that this lineage began to expand in the Rio de Janeiro metropolitan area in 2009. Multivariate analysis supported an association between bloodstream infections and the CC5 lineage that includes the RdJ clone. Compared with other closely related isolates, representative isolates of the RdJ clone more effectively evaded immune function related to monocytic cells, as evidenced by decreased phagocytosis rate and increased numbers of viable unphagocytosed (free) bacteria after in vitro exposure to monocytes.     

A change in Belgian epidemic methicillin-resistant Staphylococcus aureus phage types in 2000: phenotypic and genotypic characterization of isolates from a general hospital

During 2000, new methicillin-resistant Staphylococcus aureus (MRSA) epidemic phage types became preponderant in Belgium. In the present study, phenotypic and genotypic characteristics of 130 MRSA isolates from a general Belgian hospital were investigated. The MRSA nature of the isolates was confirmed by coagulase test, oxacillin screen plate test and detection of the mecA gene by polymerase chain reaction. Phage typing categorized the MRSA strains into two main groups: the [O]* types and the [J]* types. SmaI macrorestriction analysis by pulsed-field gel electrophoresis gave the same pulsotype in the majority of strains. All strains of the [O]* and [J]* groups, except one, belonged to this pulsotype. Aminoglycoside-modifying-enzyme genes could only be detected in a minority of strains. Although the epidemic phage types of the mid-1990s appear to have been supplanted by the [O]* and [J]* groups, the MRSA population examined showed a remarkably uniform profile corresponding to the previous major clone B.     

铜绿假单胞菌氨基糖苷类修饰酶基因分子流行病学研究

目的研究铜绿假单胞菌氨基糖苷类修饰酶基因分子流行病学. 方法用PCR方法对35株铜绿假单胞菌的氨基糖苷类耐药相关基因、氨基糖苷类修饰酶基因aac(3)-Ⅰ、aac(3)-Ⅱ、aac(3)-Ⅲ、aac(3)-Ⅳ、aac(6′)-Ⅰ、aac(6′)-Ⅱ、 aph(3′)-Ⅵ、ant(3″)-Ⅰ和ant(2″)-Ⅰ等9种基因进行了检测与分析. 结果35株中20株检出氨基糖苷类修饰酶基因(57.1%);9种基因由高到低的检出率分别为aac(6′)-Ⅱ(34.2%)、ant(2″)-Ⅰ(28.6%)、aac(3)-Ⅱ(17.1%)、aac(6′)-Ⅰ(17.1%)、ant(3″)-Ⅰ(14.3%) 、aac(3)-Ⅰ(0)、aac(3)-Ⅲ(0)、aac(3)-Ⅳ(0)、aph(3′)-Ⅵ(0). 结论本研究表明,湖北襄樊地区铜绿假单胞菌耐氨基糖苷类药物,主要机制为产氨基糖苷类修饰酶(57.1%),本组铜绿假单胞菌中另有15株表型为氨基糖苷类药物不敏感但9种基因检测为阴性,可能存在其他修饰酶基因,或者存在16S rRNA基因突变.     

Appearance of methicillin-resistant Staphylococcus aureus (MRSA) sensitive to gentamicin in a hospital with a previous endemic distinct MRSA

Since 1990 a clone of gentamicin and methicillin-resistant Staphylococcus aureus (MRSA) has remained endemic in our hospital, but since January 1996 a gentamicin-sensitive strain has progressively replaced the previous clone. We characterized the phenotypic and molecular pattern of the MRSA strains isolated in our hospital in 1996 and compared prospectively the epidemiological, clinical and evolutionary characteristics of ninety patients infected or colonized by gentamicin-sensitive MRSA (GS-MRSA) (49) and by gentamicin-resistant MRSA (GR-MRSA) (41). Finally we studied the variation of aminoglycoside consumption in our hospital from 1989 to 1996. We observed two antibiotypes (GS-MRSA and GR-MRSA) corresponding to two major chromosomal patterns. Patients with GS-MRSA usually acquired the infection 72 hours after hospital admission. No significant differences were observed in epidemiological characteristics, clinical presentation and evolution between patients with GS-MRSA and GR-MRSA. Since 1989 aminoglycoside intake in our hospital has decreased by 46%.     

Immune mechanisms induced by an HSV-1 mutant strain: Discrepancy analysis of the immune system gene profile in comparison with a wild-type strain

Herpes simplex virus is a prevalent pathogen of humans of various age groups. The fact that no prophylactic or therapeutic vaccine is currently available suggests a significant need to further investigate the immune mechanisms induced by the virus and various vaccine candidates. We previously generated an HSV-1 mutant strain, M3, with partial deletions in ul7, ul41 and LAT that produced an attenuated phenotype in mice. In the present study, we performed a comparative analysis to characterize the immune responses induced by M3 versus wild-type HSV-1 in a mouse model. Infection with wild-type HSV-1 triggered an inflammatory-dominated response and adaptive immunity suppression and was accompanied by severe pathological damage. In contrast, infection with M3 induced a systematic immune response involving full activation of both innate and adaptive immunity and was accompanied by no obvious pathological changes. Furthermore, the immune response induced by M3 protected mice from lethal challenge with wild-type strains of HSV-1 and restrained virus proliferation and impaired latency. These data are useful for further HSV-1 vaccine development using a mutant strain construction strategy.     

A 12-year review of Staphylococcus aureus bloodstream infections in haemodialysis patients: more work to be done

Staphylococcus aureus bloodstream infections (BSI) are a significant cause of morbidity and mortality in haemodialysis patients. This study describes a 12-year retrospective review of S. aureus BSI in a large haemodialysis centre in a tertiary referral hospital. The overall rate of S. aureus BSI was 17.9 per 100 patient-years (range 9.7–36.8). The rate of meticillin-resistant S. aureus (MRSA) BSI was 5.6 per 100 patient-years (range 0.9–13.8). Infective complications occurred in 11% of episodes, the most common being infective endocarditis (7.6%). Ten percent of patients died within 30 days of S. aureus being isolated from blood. Most cases of S. aureus BSI (83%) were related to vascular catheters. The provision of lower-risk vascular access, such as arteriovenous fistulae, and reduced use of intravascular catheters should be priorities in all haemodialysis units. Where alternative vascular access cannot be established, interventions to reduce the risk of catheter-related infections should be implemented to reduce morbidity and mortality in this vulnerable patient group.     

Impact of the reinforcement of a Methicillin-Resistant Staphylococcus aureus Control Programme: A 3-year evaluation by several indicators in a French University Hospital

Our objective was to evaluate the impact of the reinforcement of a methicillin-resistant Staphylococcus aureus (MRSA) control programme and to assess the impact of risk adjustment on the interpretation of data. A stepwise, retrospective analysis of 3-year prospectively collected data was performed in a 600-bed French teaching hospital in the Parisian area. A reinforcement of a pre-existing programme for limiting the spread of MRSA was implemented in 2002 and 2003 by increasing the frequency of the feedback of surveillance data, by using alcohol-based disinfectants, and by increasing patient screening. Different indicators were used to follow the change over time of MRSA transmission: the proportion of MRSA acquired in our hospital, the incidence of newly acquired MRSA/1,000 patient-days (PD) (incidence of newly acquired MRSA), the incidence of newly acquired MRSA isolated in at least one clinical specimen/1,000 PD (incidence of newly acquired clinical MRSA), and a risk-adjusted indicator, the incidence of newly acquired-MRSA isolated in at least one clinical specimen/1,000 PD of carriers identified at admission (incidence related to the risk of acquisition). The change over time of these indicators was studied with the chi-square test for trend. During the study, all indicators decreased significantly, with a mean drop of 0.07/1,000 PD for the incidence of newly acquired clinical MRSA, and a mean drop of 3.0/1,000 PD for the incidence related to the risk of acquisition. The proportion of MRSA acquired in our hospital decreased from 49.3% in 2002 to 24.1% in 2004. Concurrently, between 2002 and 2004, the number of patients screened on admission to hospital or at the time of intra-hospital transfer increased by 31% and the consumption of waterless alcohol-based hand disinfectants increased by 244%. The decreasing trend of all indicators emphasizes the effectiveness of the reinforcement of our MRSA control programme. From 2002 to 2004, the trend of the indicator related to the risk of acquisition over time is similar to those of other indicators. Further studies should be useful to assess if risk-adjustment is absolutely necessary when tracking rates within a single institution.     

The safety and immunogenicity of a recombinant five-antigen Staphylococcus aureus vaccine among patients undergoing elective surgery for closed fractures: A randomized,double-blind,placebo-controlled,multicenter phase 2 clinical trial

BackgroundVaccines are urgently required to control Staphylococcus aureus hospital and community infections and reduce the use of antibiotics. Here, we report the safety and immunogenicity of a recombinant five-antigen Staphylococcus aureus vaccine (rFSAV) in patients undergoing elective surgery for closed fractures.MethodsA randomized, double-blind, placebo-controlled, multicenter phase 2 clinical trial was carried out in 10 clinical research centers in China. Patients undergoing elective surgery for closed fractures, aged 18–70 years, were randomly allocated at a ratio of 1:1 to receive the rFSAV or placebo at a regimen of two doses on day 0 and another dose on day 7. All participants and investigators remained blinded during the study period. The safety endpoint was the incidence of adverse events within 180 days. The immunogenicity endpoints included the level of specific antibodies to five antigens after vaccination, as well as opsonophagocytic antibodies.ResultsA total of 348 eligible participants were randomized to the rFSAV (n = 174) and placebo (n = 174) groups. No grade 3 local adverse events occurred. There was no significant difference in the incidence of overall systemic adverse events between the experimental (40.24 %) and control groups (33.72 %) within 180 days after the first immunization. The antigen-specific binding antibodies started to increase at days 7 and reached their peaks at 10–14 days after the first immunization. The rapid and potent opsonophagocytic antibodies were also substantially above the background levels.ConclusionsrFSAV is safe and well-tolerated in patients undergoing elective surgery for closed fractures. It elicited rapid and robust specific humoral immune responses using the perioperative immunization procedure. These results provide evidence for further clinical trials to confirm the vaccine efficacy.China's Drug Clinical Trials Registration and Information Publicity Platform registration number: CTR20181788. WHO International Clinical Trial Registry Platform identifier: ChiCTR2200066259.     

机械通气患者下呼吸道和气路细菌学监测与分子流行病学研究

目的分析RICU机械通气患者气路、下呼吸道病原学、药敏和克隆传播情况. 方法通过前瞻性研究,动态采集15例机械通气患者下呼吸道、呼吸机管路、RICU工作人员手拭子及纤支镜(用于气道管理)标本,常规方法分离病原菌. 结果患者下呼吸道平均分离病原菌(3.86±1.57)种;分离率较高的细菌包括嗜麦芽寡养单胞菌(PMA)、表皮葡萄球菌、粪肠球菌、念珠菌属和鲍氏不动杆菌;其中60%的患者分离出PMA;这些细菌对大多数常用的抗菌药物耐药率＞60%. 结论机械通气患者下呼吸道和呼吸机管路存在着较严重的多耐药复合菌感染(定植);病原菌在不同患者间存在克隆传播.     

Experimental iron-inactivated Pasteurella multocida A: 1 vaccine adjuvanted with bacterial DNA is safe and protects chickens from fowl cholera

Fowl cholera is a serious problem in large and small scale poultry production. The present study describes the development and testing of an inactivated whole-cell, low-cost, safe, and effective vaccine for fowl cholera based on a previous work (Vaccine 23:5590–5598). Pasteurella multocida A: 1 grown in the presence of low FeCl₃ concentrations, inactivated with higher concentrations of FeCl₃, and adjuvanted with bacterial DNA from P. multocida B: 2 containing immunostimulatory CpG motifs protect chickens with a lethal P. multocida A: 1 challenge. Chickens were immunized with two whole-cell inactivated vaccine doses at 4 weeks apart and challenged 4 weeks after booster immunization. Experimental vaccines were pure, easy injectable, and caused very little distress in chickens due to their aqueous consistency. Vaccines and bacterial DNA (bDNA) posed no safety problems when chickens were injected subcutaneously (s.c.) with a single, double, and overdose of these preparations. Immunized chickens produced systemic IgY antibodies (Ab) responses and vaccine adjuvanted with bDNA protected 100% chickens from lethal intrapertoneal (i.p.) P. multocida A: 1 challenge. This work suggests that use of bDNA as an adjuvant can improve the cost-effectiveness of inactivated veterinary vaccines for their use in developing countries. Our future studies will focus on safety and potency evaluation of experimental and current vaccines using bDNA as an adjuvant.