Spatial and Temporal Variation of Enterobacter Genotypes in Sediments and the Underlying Hyporheic Zone of an Agricultural Stream

Population studies of enteric bacteria in an agriculturally impacted stream (Ledbetter Creek, Murray, Kentucky, USA) were conducted over a period of 2 years. Total number of bacteria, cultivated heterotrophic aerobic bacteria, and enteric bacteria showed significant differences between winter and summer. The cultivated numbers of heterotrophic aerobic bacteria and enteric bacteria were significantly more abundant in summer than in winter. The abundance of enteric bacteria was 12.9% in an upwelling zone and 9.8% in a downwelling zone in summer. Most of the enteric bacterial strains isolated on MacConkey agar were assigned to Enterobacter cloacae and E. agglomerans by API 20E and an analysis of the restriction patterns produced by amplified DNA coding for 16S rRNA (ARDRA) with the enzyme Hpa II. E. cloacae and E. agglomerans genotypes isolated from three hyporheic and gravel bar depth intervals (0-10 cm, 15-25 cm, and 30-40 cm) in summer and fall showed significant spatial variation and were heterogeneously distributed along the stream. Temperature, inorganic nutrients, and occurrence of anoxic zones affected the distribution of enteric bacteria. These techniques can be used as a model to monitor shifts among different species in the stream ecosystem.     

The action of combinations of the nonapeptide polymyxin B with antibiotics on gram-negative bacteria

Activity of polymyxin B nonapeptide alone and in combination with other antibiotics against clinical strains of Pseudomonas and enteric bacteria was studied. It was shown that nonapeptide was highly active against Pseudomonas and moderately active against enteric bacteria. In combination with rifampicin, fusidic acid or erythromycin the nonapeptide had a potentiating effect on the tested strains.     

烧伤后大鼠肠道菌群的改变及其易位

本文报告了25％烧伤后注射免疫抑制剂(地寨米松磷酸钠)大鼠7种肠道细菌的定量、内脏及血液的细菌培养和肠壁的病理形态学改变。单纯烧伤组(B组)和单纯注射免疫抑制剂组(Ⅰ组)动物肠壁的病理改变较轻,肠道菌群改变不明显,其肠道细菌易位率也很低。烧伤后注射免疫抑制剂的动物(BⅠ组)肠壁病变严重,肠道菌群改变明显。其中,肠杆菌在回肠、盲肠,结肠内容物中的菌量均明显升高;回肠内容物中拟杆菌的菌量明显减少;该组动物肠道细菌易位率也明显增高,达60％。此外,BⅠ组、Ⅰ组部分动物发生了由棒状杆菌及由棒状扦菌和肠杆菌混合引起的内源性感染。根据不同肠段肠壁病变严重程度、菌群变化的部位以及不同部位肠管生理功能的不同,我们推测,回肠以上肠段是肠道细菌易位的主要部位。     

Differential elimination of enteric bacteria by protists in a freshwater system

J. IRIBERRI, I. AZÚA, A. LABIRUA-ITURBURU, I. ARTOLOZAGA AND I. BARCINA. 1994. The short-term (1 h) and long-term (3 d) elimination of low and high densities of five enteric bacteria, Klebsiella pneumoniae, Aeromonas hydrophila, Escherichia coli, Enterococcus faecalis and Staphylococcus epidermidis, by flagellate and ciliate protists were measured in a freshwater system. In addition, the two processes, ingestion and digestion, which cause the disappearance of those enteric bacteria as time passes, were quantified.
The results showed that the elimination of these enteric bacteria by protists depends on their initial density, which confirms that the lower the bacterial density the more difficult is their elimination. On the other hand, the short-term and long-term elimination rates of each enteric bacteria were different, and moreover, the order of priority for elimination in the two cases was not the same. Escherichia coli showed the highest elimination rate in short-term experiments, while Aer. hydrophila disappeared at highest rates in long-term experiments. This different order of priority in the elimination rates and the different digestion rates on the five enteric bacteria by phagotrophic protists indicated that the elimination in time is very much influenced by the digestive capacity on each enteric bacteria of those protists. Thus, the low digestion rates of Ent. faecalis and Staph. epidermidis by flagellates and ciliates as well as their low disappearance percentages in the long-term experiments confirm that enteric Gram-positive bacteria are eliminated from the aquatic systems at lower rates, because their digestion is difficult.     

环境水体中肠道感染菌群与几种典型致病菌的QPCR检测及相关性分析

利用定量PCR(QPCR)方法,对环境水体中的肠道感染菌群及几种致病菌进行4个月的连续检测。结果表明:在污染严重的水体中,埃希氏大肠菌(E.coli)是水中肠道感染菌群的主体,其强度接近于用通用引物检测出的肠道感染菌群强度。当肠道感染菌群拷贝数超过10⁴copies·100 mL^-1时,沙门氏菌(S.typhrmurium)和志贺氏痢疾杆菌(Shigella flexneri)也持续被检出,可以认为是水体病原污染的标志之一;在轻度污染和清洁水体中,当肠道感染菌群拷贝数低于10⁴copies·100 mL^-1时,通过通用引物检测到的肠道感染菌群主要是上述3种病原细菌以外的细菌,且3种病原细菌的出现频度和强度与肠道感染菌群之间没有明显的相关性。     

Expanding the Role of the Virome: Commensalism in the Gut

Viruses affect host physiology beyond causing acute disease, thereby giving rise to the concept that the virome is a component of the microbiome. However, the role of the enteric virome is understudied relative to the fast-paced research examining commensal bacteria in the intestine. In this article, I discuss our recent work on murine norovirus indicating that an animal virus in the intestine can provide many of the signals to the host that have been attributed to commensal bacteria. Our findings suggest that the surge in microbiome research should incorporate examination of the enteric virome.     

The role of enteric bacteria in the anaerobic metabolism of 5-aminosalicylate

The primary (and inactive) enteric metabolite of 5-aminosalicylate is N-acetyl-5-aminosalicylate. Previous studies have demonstrated acetylation of this anti-inflammatory agent by intestinal and bacterial homogenates. To assess the contribution of anaerobic bacteria to the N-acetylation in vivo, we have measured the production of N-acetyl-5-aminosalicylate in anaerobic microculture. Our results indicate that enteric bacteria play a minor role in N-acetylation, but may contribute to the production of other metabolites of pharmacologic and toxicological interest.     

Chemotactic transducer proteins of Escherichia coli exhibit homology with methyl-accepting proteins from distantly related bacteria.

Transducers are transmembrane, methyl-accepting proteins central to the chemotactic systems of the enteric bacteria Escherichia coli and Salmonella typhimurium. Methyl-accepting proteins have been reported in a number of species in addition to these enteric bacteria. Those species include Bacillus subtilis and Spirochaeta aurantia, representatives of groups that diverged from ancestral enteric bacteria and from each other very early in bacterial evolution. An antiserum that reacts with all transducers of E. coli precipitated specifically methyl-accepting proteins from B. subtilis and S. aurantia, indicating that these proteins share antigenic determinants with transducers of E. coli. In addition, analysis of tryptic peptides by high-pressure liquid chromatography revealed similarities in the regions of methyl-accepting sites for proteins from all three species. These observations imply that structural features have been preserved in the three species from transducers contained in a common ancestor of eubacteria. It is thus reasonable to predict that other flagellated, chemotactic bacteria will be found to contain methyl-accepting proteins homologous to transducers of enteric bacteria.     

Comparative evaluation of commercial test systems for the identification of gram-negative bacteria

Diagnostic efficiency of 5 test-systems i.e. Enterotube 11, Oxi-Ferm Tube, API 20E, API 20NE and MS-2 BID was estimated comparatively with using collection and clinical strains of enteric bacteria and nonfermenting organisms. The accuracy of the enteric bacteria identification as compared to that with the use of the routine methods was more than 90 per cent. The diagnostic mistakes were more frequent with species differentiation of Klebsiella and Enterobacter. In the studies with nonfermenting bacteria the results were less stable and statistically significant differences in identification of separate strains were stated. Advantages and disadvantages of various test-systems are discussed.     

几种抗菌药物对腹泻羔羊肠道细菌的影响及临床观察

通过对治疗前后腹泻羔羊粪便细菌检查及临床观察,以查明两种抗菌药物对腹泻羔羊肠道细菌的影响。结果表明,腹泻羔羊治疗前粪便中的革兰氏阳性杆菌,革兰氏阳性球菌及革兰氏阴性杆菌的比例分别为20％、10％和70％。用敌菌净治疗的效果显著,其羔羊肠道细菌的比例接近健康羔羊。用庆大霉素治疗的羔羊,部分出现不良反应,其肠道细菌出现失调状态。     

The role of enteric bacteria in the anerobic metabolism of 5-aminosalicylate

The primary (and inactive) enteric metabolite of 5-aminosalicylate is N-acetyl-5-amino-salicylate. Previous studies have demonstrated acetylation of this anti-inflammatory agent by intestinal and bacterial homogenates. To assess the contribution of anerobic bacteria to the N-acetylation in vivo, we have measured the production of N-acetyl-5-aminosalicylate in anerobic microculture. Our results indicate that enteric bacteria play a minor role in N-acetylation, but may contribute to the production of other metabolites of pharmacologic and toxicological interest.     

婴幼儿腹泻病原学及其快速诊断

目的探讨小儿腹泻标本病原学特点及流行病学特征,寻求小儿感染性腹泻的快速诊断方法。方法对我院2003年10月至2005年9月门诊及住院的1160例2个月-5岁腹泻患儿的腹泻标本进行细菌学检查及pH检测。结果(1)1160例患儿腹泻标本病原学阳性605例(52.16%),检出病原20种621株,外源性肠道病原菌、内源性肠道条件致病菌以及轮状病毒3种病原构成比依次为35.75%、32.69%、31.56%。主要病原:(1)轮状病毒196株(31.56%),志贺菌118株(19.00%),克雷伯菌86株(13.8%),枸橼酸杆菌67株(10.79%),致泻性大肠埃希菌60株(9.66%)。(2)1160例患儿腹泻标本6个月-2岁患儿占881例(69.91%)。轮状病毒腹泻多发于秋冬季、大便为水样、多见于2岁以内婴幼儿,志贺菌以夏秋季与脓血便检出率较高。(3)病原菌分离阳性腹泻标本pH>7占明显优势,轮状病毒阳性标本、病原检查阴性标本、健康体检对照标本pH<6占明显优势,前者pH与后三者pH统计学比较,差异有高度显著性(P<0.01)。结论引起小儿腹泻的病原种类繁多,轮状病毒居首位,内源性肠道条件致病菌在腹泻标本中的构成比已接近外源性肠道致病菌而成为腹泻的重要病原菌,大便pH可作为急性腹泻病早期简单、快速、准确、价廉的初步诊断及合理应用抗生素的重要指标。     

Mechanisms of bacterial resistance and response to bile

Enteric bacteria are resistant to the bactericidal effects of intestinal bile, but these resistance mechanisms are not completely understood. It is becoming increasingly apparent that enteric bacteria have evolved to utilize bile as a signal for the temporal production of virulence factors and other adaptive mechanisms. A greater understanding of the resistance and response of bacteria to bile may assist the development of novel therapeutic, prevention, and diagnostic strategies to treat enteric and extraintestinal infections.     

Antimicrobial properties of garlic oil against human enteric bacteria: evaluation of methodologies and comparisons with garlic oil sulfides and garlic powder

The antimicrobial effects of aqueous garlic extracts are well established but those of garlic oil (GO) are little known. Methodologies for estimating the antimicrobial activity of GO were assessed and GO, GO sulfide constituents, and garlic powder (GP) were compared in tests against human enteric bacteria. Test methodologies were identified as capable of producing underestimates of GO activity. Antimicrobial activity was greater in media lacking tryptone or cysteine, suggesting that, as for allicin, GO effects may involve sulfhydryl reactivity. All bacteria tested, which included both gram-negative and -positive bacteria and pathogenic forms, were susceptible to garlic materials. On a weight-of-product basis, 24 h MICs for GO (0.02 to 5.5 mg/ml, 62 enteric isolates) and dimethyl trisulfide (0.02 to 0.31 mg/ml, 6 enteric isolates) were lower than those for a mixture of diallyl sulfides (0.63 to 25 mg/ml, 6 enteric isolates) and for GP, which also exhibited a smaller MIC range (6.25 to 12.5 mg/ml, 29 enteric isolates). Viability time studies of GO and GP against Enterobacter aerogenes showed time- and dose-dependent effects. Based upon its thiosulfinate content, GP was more active than GO against most bacteria, although some properties of GO are identified as offering greater therapeutic potential. Further exploration of the potential of GP and GO in enteric disease control appears warranted.     

宁波市城区内河肠道病原细菌定量 PCR 分析

了解城市内河中病原菌含量对城市生态安全具有重要意义。应用定量PCR（ qPCR）方法,对宁波市城区6条重要内河水体中的病原菌含量及主要水质指标进行分析。结果表明,祖关山河、苏家河、南北河、后西河、史魏家河和直落河每升水体中含有病原菌基因的拷贝数分别为：3.34×105、1.47×105、4.68×105、1.75×106、9.65×106和1.33×106;且病原菌基因的含量与水体溶解氧负相关,与总氮、氨氮、浊度、总磷、高锰酸钾指数、叶绿素a和电导率呈正相关关系,但与水体透明度、温度和酸碱度无明显关系。定量PCR分析结果可望为评价城市内河水体质量提供重要参考。     

Antimicrobial Properties of Garlic Oil against Human Enteric Bacteria: Evaluation of Methodologies and Comparisons with Garlic Oil Sulfides and Garlic Powder

The antimicrobial effects of aqueous garlic extracts are well established but those of garlic oil (GO) are little known. Methodologies for estimating the antimicrobial activity of GO were assessed and GO, GO sulfide constituents, and garlic powder (GP) were compared in tests against human enteric bacteria. Test methodologies were identified as capable of producing underestimates of GO activity. Antimicrobial activity was greater in media lacking tryptone or cysteine, suggesting that, as for allicin, GO effects may involve sulfhydryl reactivity. All bacteria tested, which included both gram-negative and -positive bacteria and pathogenic forms, were susceptible to garlic materials. On a weight-of-product basis, 24 h MICs for GO (0.02 to 5.5 mg/ml, 62 enteric isolates) and dimethyl trisulfide (0.02 to 0.31 mg/ml, 6 enteric isolates) were lower than those for a mixture of diallyl sulfides (0.63 to 25 mg/ml, 6 enteric isolates) and for GP, which also exhibited a smaller MIC range (6.25 to 12.5 mg/ml, 29 enteric isolates). Viability time studies of GO and GP against Enterobacter aerogenes showed time- and dose-dependent effects. Based upon its thiosulfinate content, GP was more active than GO against most bacteria, although some properties of GO are identified as offering greater therapeutic potential. Further exploration of the potential of GP and GO in enteric disease control appears warranted.     

Modeling the Infection Dynamics of Bacteriophages in Enteric Escherichia coli: Estimating the Contribution of Transduction to Antimicrobial Gene Spread

Animal-associated bacterial communities are infected by bacteriophages, although the dynamics of these infections are poorly understood. Transduction by bacteriophages may contribute to transfer of antimicrobial resistance genes, but the relative importance of transduction among other gene transfer mechanisms is unknown. We therefore developed a candidate deterministic mathematical model of the infection dynamics of enteric coliphages in commensal Escherichia coli in the large intestine of cattle. We assumed the phages were associated with the intestine and were predominantly temperate. Model simulations demonstrated how, given the bacterial ecology and infection dynamics, most (>90%) commensal enteric E. coli bacteria may become lysogens of enteric coliphages during intestinal transit. Using the model and the most liberal assumptions about transduction efficiency and resistance gene frequency, we approximated the upper numerical limits (“worst-case scenario”) of gene transfer through specialized and generalized transduction in E. coli by enteric coliphages when the transduced genetic segment is picked at random. The estimates were consistent with a relatively small contribution of transduction to lateral gene spread; for example, generalized transduction delivered the chromosomal resistance gene to up to 8 E. coli bacteria/hour within the population of 1.47 × 10⁸ E. coli bacteria/liter luminal contents. In comparison, the plasmidic bla_CMY-2 gene carried by ∼2% of enteric E. coli was transferred by conjugation at a rate at least 1.4 × 10³ times greater than our generalized transduction estimate. The estimated numbers of transductants varied nonlinearly depending on the ecology of bacteria available for phages to infect, that is, on the assumed rates of turnover and replication of enteric E. coli.     

Homology of Escherichia coli R773 arsA, arsB, and arsC genes in arsenic-resistant bacteria isolated from raw sewage and arsenic-enriched creek waters.

The occurrence and diversity of the Escherichia coli R773 ars operon were investigated among arsenic-resistant enteric and nonenteric bacteria isolated from raw sewage and arsenic-enriched creek waters. Selected isolates from each creek location were screened for ars genes by colony hybridization and PCR. The occurrence of arsA, arsB, and arsC determined by low-stringency colony hybridization (31 to 53% estimated mismatch) was 81, 87, and 86%, respectively, for 84 bacteria isolated on arsenate- and arsenite-amended media from three locations. At moderate stringency (21 to 36% estimated mismatch), the occurrence decreased to 42, 56, and 63% for arsA, arsB, and arsC, respectively. PCR results showed that the ars operon is conserved in some enteric bacteria isolated from creek waters and raw sewage. The occurrence of the arsBC genotype was about 50% in raw sewage enteric bacteria, while arsA was detected in only 9.4% of the isolates (n = 32). The arsABC and arsBC genotypes occurred more frequently in enteric bacteria isolated from creek samples: 71.4 and 85.7% (n = 7), respectively. Average sequence divergence within arsB for six creek enteric bacteria was 20% compared to that of the E. coli R773 ars operon. Only 1 of 11 pseudomonads screened by PCR was positive for arsB. The results from this study suggest that significant divergence has occurred in the ars operon among As-resistant E. coli strains and in Pseudomonas spp.     

Complete Genome Sequence of the B12-Producing Shimwellia blattae Strain DSM 4481, Isolated from a Cockroach

Here we announce the complete genome sequence of the coenzyme B(12)-producing enteric bacterium Shimwellia blattae (formerly Escherichia blattae). The genome consists of a single chromosome (4,158,636 bp). The genome size is smaller than that of most other enteric bacteria. Genome comparison revealed significant differences from the Escherichia coli genome.     

Major heat-modifiable outer membrane protein in gram-negative bacteria: comparison with the ompA protein of Escherichia coli.

The outer membranes of several strains of Escherichia coli, other enteric bacteria, and a variety of nonenteric gram-negative bacteria all contain a major heat-modifiable protein similar to the OmpA protein of E. coli K-12. The heat-modifiable proteins from these bacteria resemble the K-12 protein in molecular weight, in preferential release from the outer membrane by sodium dodecyl sulfate in the presence of Mg2+, and in characteristic cleavage by proteases to yield a smaller fragment which remains membrane bound. Antiserum directed against the K-12 protein precipitated the heat-modifiable protein from all strains of Enterobacteriaceae, and chemical comparison by isoelectric focusing, cyanogen bromide cleavage profiles, and proteolytic peptide analysis indicated that the proteins from the various enteric bacteria were nearly identical in primary structure. The heat-modifiable proteins from bacteria phylogenically distant from E. coli shared many of the properties of the E. coli protein but were chemically distinct. Thus, it appears that the structure (and, presumably, the function) of the heat-modifiable protein of gram-negative bacteria is strongly conserved during evolution.