广谱抗生素对脓毒症大鼠肠道微生态环境的影响

目的 探讨广谱抗生素对脓毒症大鼠肠道微生态环境的影响.方法 56只健康SD大鼠被随机分为正常对照组、烫伤组和脓毒症组.于大鼠背部造成30%总体表面积Ⅲ度烫伤后24 h,间隔12 h分两次腹腔注射内毒素(20mg/kg)进行"二次打击"制备脓毒症模型.分别于烫伤及"二次打击"后24 h,间隔12 h分两次腹腔注射头孢曲松进行治疗,各组于治疗前及治疗3 d和9 d活杀8只大鼠,取胃窦、小肠、结肠内容物及结肠黏膜行细菌定量培养、菌种鉴定.结果 单纯烫伤对结肠内容物杆菌数量和种类无明显影响,"二次打击"后,杆菌数升高上千倍(P<0.01),应用头孢曲松治疗后大鼠结肠内容物杆菌数量明显减少(P均<0.01),小肠内容物肠杆菌亦有类似变化,而胃内容物肠杆菌数量变化不显著.经烫伤及"二次打击"后肠道杆菌数量显著增加,球/杆比值负值增大;应用头孢曲松后,肠球菌数量显著增多,球/杆比值严重倒置;厌氧菌数量亦有所减少,但差异不显著.结论 广谱抗生素使定植于肠道的厌氧菌和肠杆菌数量锐减,使肠球菌、耐药菌选择为优势菌群成为可能,造成肠道微生态环境破坏.     

The Effect of Photodynamic Therapy in Root Canal Disinfection: A Systematic Review

Introduction

Effective root canal disinfection is a fundamental component of successful root canal treatment. Photodynamic therapy (PDT) has been proposed as a new adjunctive method for additional disinfection of the root canal system with the possibility of improved treatment outcomes. The aim of this systematic review was to investigate the effect of PDT on bacterial load reduction during root canal disinfection.

Methods

Two reviewers independently conducted a comprehensive literature search using a combination of medical subject heading terms and key words to identify studies relevant to the Population Intervention Control Outcome question. The selection of articles for inclusion was performed in 2 phases based on predetermined eligibility criteria according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Inter-reviewer agreement for each phase was recorded. The effect of PDT on bacterial load reduction during root canal disinfection was evaluated as the primary outcome variable during data extraction.

Results

The literature search provided 57 titles and abstracts. Three articles met the inclusion criteria and were selected for this systematic review. The reasons for study exclusion in each phase were recorded. Because of the heterogeneity in clinical indications and PDT protocols among the included studies, a meta-analysis could not be performed. All included studies showed a positive effect of PDT in the reduction of microbial load in root canal treatment ranging from 91.3%–100%.

Conclusions

Limited clinical information is currently available on the use of PDT in root canal disinfection. If supported by future clinical research, PDT may have efficacy for additional root canal disinfection, especially in the presence of multi–drug-resistant bacteria.     

常州地区医院制剂室空气中尘粒和细菌总数的检测

在检测的常州地区１４所医院制剂室的超净工作台与洁净间空气中，细菌总数未超标者仅有１所，空气中尘粒数均未超标者亦仅７所。为此，应加强对制剂室防止空气污染的管理与监测。     

关于现代病原生物学教学改革的探讨

病原生物学是必不可少的医学基础学科。为适应现代医学发展趋式,病原生物学的教学改革势在必行。本文结合本院实际,通过对病原生物学教学中所存在问题的分析,论述近年来所采取的相应教学改革措施及其所取得的成果。     

Profilaxis antibiótica «dirigida» por cultivos rectales antes de la biopsia prostática transrectal: reducción de complicaciones infecciosas y costes de atención sanitaria

Background

Transrectal ultrasound-guided prostate biopsy (TUPB) is associated with infectious complications (ICs), which are related to a greater prevalence of ciprofloxacin-resistant bacteria (CRB) in rectal flora. We examined the ICs that occurred in 2 groups: A guided antibiotic prophylaxis (GP) group and an empiric prophylaxis (EP) group. We assessed the financial impact of GP.

From the Cover: Contribution of cyanobacterial alkane production to the ocean hydrocarbon cycle

Hydrocarbons are ubiquitous in the ocean, where alkanes such as pentadecane and heptadecane can be found even in waters minimally polluted with crude oil. Populations of hydrocarbon-degrading bacteria, which are responsible for the turnover of these compounds, are also found throughout marine systems, including in unpolluted waters. These observations suggest the existence of an unknown and widespread source of hydrocarbons in the oceans. Here, we report that strains of the two most abundant marine cyanobacteria, Prochlorococcus and Synechococcus, produce and accumulate hydrocarbons, predominantly C15 and C17 alkanes, between 0.022 and 0.368% of dry cell weight. Based on global population sizes and turnover rates, we estimate that these species have the capacity to produce 2–540 pg alkanes per mL per day, which translates into a global ocean yield of ∼308–771 million tons of hydrocarbons annually. We also demonstrate that both obligate and facultative marine hydrocarbon-degrading bacteria can consume cyanobacterial alkanes, which likely prevents these hydrocarbons from accumulating in the environment. Our findings implicate cyanobacteria and hydrocarbon degraders as key players in a notable internal hydrocarbon cycle within the upper ocean, where alkanes are continually produced and subsequently consumed within days. Furthermore we show that cyanobacterial alkane production is likely sufficient to sustain populations of hydrocarbon-degrading bacteria, whose abundances can rapidly expand upon localized release of crude oil from natural seepage and human activities.Hydrocarbons are ubiquitous in the oceans, where natural seepage and human activities are estimated to release between 0.4 and 4.0 million tons of crude oil into the ocean ecosystem annually (1). Even in minimally polluted marine surface waters, alkanes such as pentadecane and heptadecane have been found at concentrations ranging from 2 to 130 pg/mL (2, 3), although their sources remain unclear. A small proportion of alkanes, from 1 to 60 fg/mL, is associated with particulate matter >0.7 µm in diameter (4). Larger amounts may be associated with particulate matter <0.7 µm in diameter, because ocean concentrations are higher than the solubility of pentadecane and heptadecane, which is ∼10 pg/mL and 1 pg/mL, respectively (2). Populations of hydrocarbon-degrading bacteria, referred to as hydrocarbonoclastic bacteria, including many species that cannot use other carbon sources, are present in marine systems and play an important role in turnover of these compounds (5–9). Because obligate hydrocarbon-degrading bacteria are found in waters without significant levels of crude oil pollution, these organisms must use an alternate hydrocarbon source (9–11).Here, we investigate the extent to which cyanobacteria may contribute to these marine hydrocarbon pools. Cyanobacteria (oxygenic photosynthetic bacteria) can synthesize C15 to C19 hydrocarbons via two separate pathways. The first produces alkanes, predominantly pentadecane, heptadecane, and methyl-heptadecane, in addition to smaller amounts of alkenes, via acyl-ACP reductase (FAR) and aldehyde deformylating oxygenase (FAD) enzymes (12). The second pathway generates alkenes, primarily nonadecene and 1,14-nonadecadiene, via a polyketide synthase enzyme (Ols) (13). The abundance and ubiquity of cyanobacteria in the marine environment suggests hydrocarbon production in the oceans could be considerable and broadly distributed geographically (14, 15).We focused our studies on the two most abundant marine cyanobacteria, Prochlorococcus and Synechococcus (16). These genera have estimated global population sizes of 2.9 ± 0.1 × 10²⁷ and 7.0 ± 0.3 × 10²⁶ cells, respectively (14), and are together responsible for approximately a quarter of marine net primary production (14). These are also the only cyanobacterial genera for which global population size estimates have been compiled (14). Although the distribution patterns of both genera overlap (14, 17), Prochlorococcus cells dominate low-nutrient open-ocean areas between 40°N and 40°S and can be found at depths of up to 200 m (16, 18). Synechococcus are more numerous in coastal and temperate regions where conditions and nutrient levels are more variable (14, 16) but are still widely distributed in high abundance.     

Detection of Sulphate-Reducing Bacteria and Others Cultivable Facultative Bacteria in Dental Tissues

Aim

To detect for the presence of sulphate-reducing bacteria (SRB) and evaluate the possible association between SRB and cultivable facultative bacterial of oral sites with different periodontal conditions.

Methods

The study was carried out on 9 samples from different oral sites in 8 patients (two samples were collected from the same patient). Material was collected using modified Postgate E culture medium, indicated for the growth and isolation of SRB. In addition, a reducing solution for anaerobic bacteria was used as a transport solution for facultative bacteria and identified by polymerase chain reaction amplification (PCR) and sequencing of the 16S rRNA gene.

Results

SRB was found in 3 patient samples: the first in a root fragment, the second in a root fragment and a healthy tooth with vertical bone loss and a mobility degree of 3; and the third in a healthy tooth extracted for orthodontic treatment. In the final patient, the cultivable facultative species Lactobacillus casei was identified. Other facultative bacterial species were identified in patient 5 (Kurthia Gibsonii) and patient 7 (Pseudomonas aeruginosa).

Conclusions

The detection of SRB in different dental tissues with distinct periodontal features demonstrated that new studies need to be developed in order to determine the true role of SRB in the oral microbiota. In addition, it was possible to verify the presence of Lactobacillus casei together with SRB in one sample.     

Susceptibility of As-yet-uncultivated and Difficult-to-culture Bacteria to Chemomechanical Procedures

Introduction

A significant portion of the bacteria taking part of the microbiome associated with apical periodontitis still remain to be cultivated and phenotypically characterized. This molecular study evaluated the prevalence of selected as-yet-uncultivated and difficult-to-culture bacterial taxa in infected root canals and their susceptibility to chemomechanical procedures.

Methods

Root canals of single-rooted teeth with apical periodontitis were prepared using rotary nickel-titanium instruments and 2.5% sodium hypochlorite as the irrigant. DNA extracts from samples taken before (S1) and after (S2) chemomechanical preparation were surveyed for the presence of 7 as-yet-uncultivated phylotypes and 1 difficult-to-culture species using end-point polymerase chain reaction. Samples were also subjected to quantitative analysis of total bacteria and levels of the 2 most prevalent taxa.

Results

Bacteroidaceae sp. HOT-272 (24%) and Fretibacterium fastidiosum (20%) were the most prevalent taxa in S1. Their mean counts in S1 were 8.25 × 10³ and 2.13 × 10³ rRNA gene copies, corresponding to 0.18% and 0.55% of the total bacteria. Chemomechanical debridement promoted a highly statistically significant reduction in total bacterial counts (P < .001), but 64% of the canals were still positive for bacterial presence. Of the target taxa, only Bacteroidaceae sp. HOT-272 and F. fastidiosum were detected in S2 (each one in 1 sample). The reduction in counts of both taxa was also highly significant (P < .001).

Conclusions

Findings confirmed that several as-yet-uncultivated and difficult-to-grow bacterial taxa can participate in the microbiome associated with apical periodontitis. Two of them were found in relatively high prevalence but rarely as a dominant species. Chemomechanical procedures were highly effective in completely eliminating these taxa or at least substantially reducing their numbers.     

Protection from lethal gram-positive infection by macrophage scavenger receptor-dependent phagocytosis

Infections with gram-positive bacteria are a major cause of morbidity and mortality in humans. Opsonin-dependent phagocytosis plays a major role in protection against and recovery from gram-positive infections. Inborn and acquired defects in opsonin generation and/or recognition by phagocytes are associated with an increased susceptibility to bacterial infections. In contrast, the physiological significance of opsonin-independent phagocytosis is unknown. Type I and II class A scavenger receptors (SR-AI/II) recognize a variety of polyanions including bacterial cell wall products such as lipopolysaccharide (LPS) and lipoteichoic acid (LTA), suggesting a role for SR-AI/II in innate immunity to bacterial infections. Here, we show that SR-AI/II-deficient mice (MSR-A(-/-)) are more susceptible to intraperitoneal infection with a prototypic gram-positive pathogen, Staphylococcus aureus, than MSR-A(+/+) control mice. MSR-A(-/-) mice display an impaired ability to clear bacteria from the site of infection despite normal killing of S. aureus by neutrophils and die as a result of disseminated infection. Opsonin-independent phagocytosis of gram-positive bacteria by MSR-A(-/-) macrophages is significantly decreased although their phagocytic machinery is intact. Peritoneal macrophages from control mice phagocytose a variety of gram-positive bacteria in an SR-AI/II-dependent manner. Our findings demonstrate that SR-AI/II mediate opsonin-independent phagocytosis of gram-positive bacteria, and provide the first evidence that opsonin-independent phagocytosis plays a critical role in host defense against bacterial infections in vivo.     

Aerobic and anaerobic infection associated with malignancy

The goal of this work was to study the microbiology and clinical characteristics of patients with infections associated with malignancy treated over a period of 17 years. A total of 668 specimens were obtained from 605 patients. The malignancies include 224 hematological malignancies and 381 nonhematogenic malignancies. Anaerobic bacteria only were isolated in 201 (30%) specimens, aerobic bacteria in 226 (34%), mixed aerobic–anaerobic bacteria in 231 (35%) and Candida spp. in 10 (1%). A total of 683 anaerobic (1.0 isolates per specimens) and 592 aerobic or facultative (0.9 per specimen) organisms were recovered. The predominant anaerobic bacteria included Bacteroides fragilis group isolates (181), Peptostreptococcus spp. (166), Prevotella spp. (106), Clostridium spp. (70), and Fusobacterium spp. (43). The predominant aerobic bacteria included Escherichia coli (133), Staphylococcus aureus (100), Klebsiella pneumoniae (48), and Pseudomonas aeroginosa (45). The type of infections included abscesses (221), bacteremia (198), wounds (175), including 61 cellulitis, 24 postsurgical wounds and 23 decubitus ulcers), peritonitis (48), empyema (12), cholecystitis (6) and thrombophlebitis (5). S. aureus and Peptostreptococcus spp. were isolated from all sites. However, organisms of the oropharyngeal flora (Prevotella and Fusobacterium spp.) predominated in local infections and bacteremia that originated from this site (head and neck wounds and abscesses and pulmonary infections), and organisms of the gastrointestinal tract flora predominated in infections that originated from this site (peritonitis, abdominal abscesses and decubitus ulcers). This retrospective study demonstrates polymicrobial features of many infections associated with malignancies.