Examining the competitive advantage of Diuraphis noxia (Hemiptera: Aphididae) biotype 2 over biotype 1.

The Russian wheat aphid, Diuraphis noxia (Kurdjumov) is a serious pest of small grains, such as wheat and barley. High population growth rates and a broad gramineae host range have allowed this aphid to successfully establish and become pestiferous across much of North America since its invasion in the mid-1980s. Resistant wheat cultivars were developed and provided control ofD. noxia until 2003, when a new biotype (designated RWA2, as contrasted with the original biotype's designation, RWA1) emerged and rapidly spread through dryland winter wheat-growing regions. RWA2 displaced RWA1 more quickly than expected, based on RWA2's advantage in RWA1-resistant wheat cultivars. Previous research suggested that RWA2 may out-compete RWA1 in cooler temperatures. Thus, we sought to determine if RWA2 had a competitive advantage over RWA1 during the overwintering period. We placed a known distribution of RWA1 and RWA2 aphids in the field for the winter at three sites across a latitudinal gradient (from northern Colorado to Texas) to test for a competitive advantage between these biotypes. We found overwhelming support for an overwintering competitive advantage by RWA2 over RWA1, with evidence suggesting a > 10-fold advantage even at our Texas site (i.e., the site with the mildest winter). This substantial overwintering advantage helps explain the quick dispersion and displacement of RWA1 by RWA2.

Pathogenicity of exopolysaccharide-producing Actinomyces oris isolated from an apical abscess lesion.

AIM: To demonstrate a capacity for producing exopolysaccharides (EPSs) and an ability to form biofilm on abiotic materials of Actinomyces oris strain K20. METHODOLOGY: The productivity of EPSs and the ability to form biofilm of strain K20 were evaluated by measuring viscosity of spent culture media and by scanning electron microscopy (SEM) and the biofilm assay on microtitre plates, respectively. High-performance liquid chromatography was used to determine the chemical composition of the viscous materials. To examine the role of the viscous materials attributable to the pathogenicity in this organism, the ability of strain K20 to induce abscess formation was compared in mice to that of ATCC 27044. RESULTS: The viscosity of the spent culture media of K20 was significantly higher than that of ATCC 27044. Strain K20 showed dense meshwork structures around the cells and formed biofilms on microtitre plates, whereas ATCC 27044 did not. Chemical analysis of the viscous materials revealed that they were mainly composed of neutral sugars with mannose constituting 77.5% of the polysaccharides. Strain K20 induced persistent abscesses in mice lasting at least 5 days at a concentration of 10(8) cells mL(-1), whereas abscesses induced by ATCC 27044 healed and disappeared or decreased in size at day 5. CONCLUSIONS: Strain K20 produced EPSs, mainly consisting of mannose, and formed biofilms. This phenotype might play an important role for A. oris to express virulence through the progression of apical periodontitis.

Microbiological characterization in children with aggressive periodontitis.

UNLABELLED: The objective of this study was to characterize the subgingival microbiota of African-American children with Localized Aggressive Periodontitis (LAP). Fifty-one children were included. Subgingival plaque samples were taken from diseased (DD) and healthy sites (DH) in LAP and from healthy sites in HS and HC and analyzed by 16S rRNA-based microarrays. Aggregatibacter actinomycetemcomitans (Aa) was the only species found to be both more prevalent (OR = 8.3, p = 0.0025) and abundant (p < 0.01) in DD. Filifactor alocis (Fa) was also found to be more prevalent in DD (OR 2.31, CI 1.06-5.01, p = 0.03). Most prevalent species in healthy sites were Selenomonas spp, Veillonella spp, Streptococcus spp, Bergeyella sp, and Kingella oralis. Overall, Streptococcus spp, Campylobacter gracilis, Capnocytophaga granulosa, Haemophilus parainfluenzae, and Lautropia mirabilis were most abundant in healthy children, while Aa, Fa, Tannerella sp, Solobacterium moorei, Parvimonas micra, and Capnocytophaga sp were most abundant in LAP. Based on a comprehensive analysis with 16S rRNA-based microarrays, Aa was strongly associated and site-specific in LAP. In contrast, other species were found to be associated with healthy sites and individuals (ClinicalTrials.gov number CT01330719). ABBREVIATIONS: healthy site in healthy sibling (HS); healthy site in healthy control child (HC).

Nitrosopumilus maritimus genome reveals unique mechanisms for nitrification and autotrophy in globally distributed marine crenarchaea.

Ammonia-oxidizing archaea are ubiquitous in marine and terrestrial environments and now thought to be significant contributors to carbon and nitrogen cycling. The isolation of Candidatus "Nitrosopumilus maritimus" strain SCM1 provided the opportunity for linking its chemolithotrophic physiology with a genomic inventory of the globally distributed archaea. Here we report the 1,645,259-bp closed genome of strain SCM1, revealing highly copper-dependent systems for ammonia oxidation and electron transport that are distinctly different from known ammonia-oxidizing bacteria. Consistent with in situ isotopic studies of marine archaea, the genome sequence indicates N. maritimus grows autotrophically using a variant of the 3-hydroxypropionate/4-hydroxybutryrate pathway for carbon assimilation, while maintaining limited capacity for assimilation of organic carbon. This unique instance of archaeal biosynthesis of the osmoprotectant ectoine and an unprecedented enrichment of multicopper oxidases, thioredoxin-like proteins, and transcriptional regulators points to an organism responsive to environmental cues and adapted to handling reactive copper and nitrogen species that likely derive from its distinctive biochemistry. The conservation of N. maritimus gene content and organization within marine metagenomes indicates that the unique physiology of these specialized oligophiles may play a significant role in the biogeochemical cycles of carbon and nitrogen.

A novel exopolysaccharide from a clinical isolate of Prevotella nigrescens: purification, chemical characterization and possible role in modifying human leukocyte phagocytosis.

Prevotella nigrescens, a gram-negative black-pigmented anaerobic rod, has frequently been isolated from periodontitis and periapical periodontitis lesions. We have isolated an exopolysaccharide-producing P. nigrescens, strain 22, from a chronic periodontitis lesion. The purpose of this study was to determine the chemical composition and function of the exopolysaccharide associated with this clinical isolate. The chemical composition and structure of the purified exopolysaccharide from strain 22 were determined by high performance liquid chromatography and methylation analysis. To define the biological function of this exopolysaccharide, a chemically induced exopolysaccharide nonproducing mutant, strain 328, which was derived from strain 22, was established. The biological effects of exopolysaccharide were determined by comparing the ability of strain 22, strain 328 or heat-killed strain 22 to form abscesses in mice and to interfere with the phagocytic activity of peripheral blood polymorphonuclear leukocytes. Chemical analysis showed that isolated exopolysaccharide consisted of mannose (521.6 microg/mg), glucose (25.6 microg/mg), fructose (65.8 microg/mg), galactose (12.5 microg/mg), arabinose (6.2 microg/mg), xylose (3.2 microg/mg), rhamnose (6.1 microg/mg), and ribose (0.6 microg/mg). Methylation analysis of exopolysaccharide indicated that the linkages of mannose were primarily (1-->2, 1-->6) (1-->2) (1-->6), and (1-->3). Strain 22 and, to a lesser extent, its heat-killed counterpart induced greater abscess formation in mice than strain 328, even though the enzymatic profile of strain 22 was similar to that of strain 328. The ability of strain 328 to induce abscess formation was restored by adding the purified exopolysaccharide isolated from strain 22 to the cell suspension of strain 328. Exopolysaccharide alone failed to induce abscess formation in mice. Further, strain 328 but not the untreated or heat-killed strain 22, was phagocytosed by polymorphonuclear leukocytes both in the presence and in the absence of opsonic factors. The results suggest that these polysaccharides isolated from strain 22, which primarily consisted of mannose, may play a key role in the development of the chronic inflammatory lesion from which this strain was isolated.

Beta-lactamase production and antimicrobial susceptibility of subgingival bacteria from refractory periodontitis.

This study assessed the extent of beta-lactamase-producing bacteria in subgingival plaque samples obtained from 25 patients with refractory marginal periodontitis in the USA. beta-Lactamase-positive isolates were characterized using commercial diagnostic kits and partial sequencing of the 16S rRNA gene. The susceptibilities to different antimicrobial agents were tested and, in addition, the isolates were screened for the presence of extended spectrum beta-lactamases (ESBLs). beta-lactamase-producing bacteria were detected in 18 (72%) patients. The most prominent beta-lactamase-producing organisms belonged to the anaerobic genus Prevotella. Other enzyme-producing anaerobic strains were Fusobacterium nucleatum, Propionibacterium acnes and Peptostreptococcus sp. Facultative bacteria, such as Burkholderia spp., Ralstonia pickettii, Capnocytophaga spp., Bacillus spp., Staphylococcus spp. and Neisseria sp., were also detected among the enzyme-producers. Minimum inhibitory concentrations (MICs) of ampicillin and amoxicillin were in the range 1.5-256 micrograms/ml and 4-256 micrograms/ml, respectively, for the isolates of the Prevotella species. All Prevotella isolates were susceptible to amoxicillin/clavulanate and metronidazole, but they showed variable resistance to tetracyclines. Two of the Prevotella isolates had high MICs of cefotaxime and ceftazidime. ESBL activity was not detected in any of the beta-lactamase-producing isolates by the Etest method. Thus, our study demonstrated a wide variety of beta-lactamase-producing bacteria that may play a role in refractory periodontal disease.

The utilitarian core hypothesis: cases for testing the stability of languages in the wake of conquest.

Based on the "utilitarian core hypothesis" that the most common words of a language develop early and resist change, the current exploratory study examined three test cases to suggest what happens to the common core of a language when its speakers are conquered. Whissell (1998) raised this issue by implication through demonstrating that the common core of English is largely Anglo-Saxon and thus survived the Norman Conquest. The notion that unique merits of English accounted for its success has a long history dating at least to Verstegan (1605/1976). We suggested that there are also instances of conquest in history illustrating the persistence of other languages despite the political subjugation of their speakers. Test cases included, in addition to the Norman Conquest of England, the Arab-Berber Conquest of most of the Iberian Peninsula, and Russian domination of modern Uzbekistan. The combined results suggest that persistence of a utilitarian core despite conquest is not an isolated instance. As a phenomenon it offers a more parsimonious account than do appeals to the special merits of English, Spanish, or Modern Uzbek. We have integrated these findings within a psychological framework pertaining to language use and change.

The effects of sustained release doxycycline on the anaerobic flora and antibiotic-resistant patterns in subgingival plaque and saliva.

BACKGROUND: The purpose of this study was to determine the effects of periodontal treatment with a sustained-release, biodegradable gel containing 8.5% doxycycline on the anaerobic flora and on antibiotic susceptibility patterns associated with subgingival plaque and saliva. METHODS: Forty-five subjects with adult periodontitis were entered into a parallel design, single-blind study of 6 months' duration. The subjects were randomized to receive either doxycycline treatment (n = 23) or oral hygiene instruction/reinforcement (n = 22). Saliva and subgingival plaque samples were collected prior to and at 7, 21, 91, and 182 days after initiation of treatment. The proportion of the cultivable flora resistant to 10 microg doxycycline/ml was determined relative to total anaerobic counts, and the 3 most predominant colony types resistant to doxycycline were individually enumerated. A representative of each was subcultured, identified to genus and species level, and tested for its susceptibilities to 6 antibiotics. RESULTS: A significant decrease (P <0.01) in total anaerobic counts following doxycycline treatment caused a transient increase in the proportion, but not in the actual counts, of doxycycline-resistant bacteria recovered from both plaque and saliva at 7 and 21 days but not at 91 or 182 days. The same doxycycline-resistant taxa were recovered at all sample periods including baseline. Regardless of treatment, the isolates were similarly distributed and belonged to the same bacterial groups. CONCLUSIONS: Doxycycline treatment significantly reduced the anaerobic population in plaque but did not result in a change in either the number of resistant bacteria present or the acquisition of antibiotic resistance.

Minimal access surgery for cholelithiasis induces an attenuated acute phase response.

BACKGROUND: Some benefits of laparoscopic (LC) and minilaparotomy (MC) cholecystectomy may reflect attenuation of the acute phase response. The authors examined components of this response. METHODS: Patients were randomized to LC (n = 11) or MC (n = 11). C-reactive protein (CRP), alpha-1-antitrypsin (AAT), retinol-binding protein (RBP), transferrin, and albumin were measured preoperatively and on postoperative days 1, 2, 4, and 7. Interleukin-1 receptor antagonist (IL-1ra), IL-6, and tumor necrosis factor (TNF-alpha) were measured more frequently perioperatively. Peak expiratory flow rate, forced expiratory volume in 1 second, and forced vital capacity were measured daily. RESULTS: The IL-6 increase was more persistent and marked in the MC patients from hour 8 to day 7 postoperatively (P < 0.05). Alterations in CRP, AAT, and albumin were similar. Postoperative deficits of respiratory function correlated with the magnitude of acute phase protein alteration. CONCLUSIONS: Minimal access surgery induces an acute phase response that is less prominent after a laparoscopic technique.

Minimal modulation of lymphocyte and natural killer cell subsets following minimal access surgery.

BACKGROUND: Trauma, whether accidental or surgically induced, is known to cause significant modulation of the cell-mediated immune response. Minimal access surgery (MAS) has been shown to improve postoperative recovery and enhance rehabilitation. The degree of immunosuppression resulting from two MAS techniques was studied and compared by measuring the circulating T lymphocyte and natural killer (NK) cell subsets. METHOD: This investigation was a randomized prospective study of patients admitted to the Professorial Surgical Unit, Aberdeen Royal Infirmary for elective cholecystectomy. Two methods of MAS were studied-laparoscopy and minilaparotomy. RESULTS: Laparoscopy was found to cause significantly less reduction in the number of cells expressing T lymphocyte phenotypic surface markers (CD2, CD3, CD8, CD4:CD8 ratio), activation markers (CD71 and HLA-DR), and NK cell subsets (CD11b, CD16, CD56 and CD57), when compared with the minilaparotomy technique. CONCLUSIONS: These data show that host defences are less suppressed after laparoscopic cholecystectomy, and this may have important implications for the use of laparoscopic techniques in major surgical resections, especially for malignant disease.

Detection and prevalence of the tetracycline resistance determinant Tet Q in the microbiota associated with adult periodontitis.

Subgingival plaque samples were collected from 68 patients with a history of moderate to severe adult periodontitis and enumerated on Trypticase-soy blood agar plates, with and without tetracycline at 4 micrograms/ml. Each different colony morphotype was enumerated, and a representative colony was subcultured for identification and examined for the tetracycline resistance gene tet(Q) by polymerase chain reaction (PCR) amplification and DNA hybridization, using a fragment of tetA(Q)2 from Bacteroides fragilis 1126. PCR primers (5'-GGCTTCTACGACATCTATTA-3' and 5'-CATCAACATTTATCTCTCTG-3') were chosen to amplify a 755 bp region of tet(Q). The subgingival plaque samples were also tested by PCR. Approximately 12% of the total cultivable flora was resistant to tetracycline, and the percentage of the tetracycline-resistant cultivable flora with the tet(Q) gene varied greatly from one patient to another with a range from 0.0 to 67%. Half of the 68 subgingival plaque samples were positive or weakly positive for tet(Q) by PCR. Approximately 15% of the 210 isolates subcultured with resistance to tetracycline, (> or = 4 micrograms/ml) contained tet(Q), and 60% contained tet(M). All of the tet(Q)-resistant isolates were gram-negative anaerobic bacilli and included all of the Prevotella and Bacteroides isolates.

Refractory periodontitis or recurrence of disease.

Refractory periodontal disease is characterized by low plaque scores and low responsiveness to periodontal therapy. The patients often have a history of antibiotic therapy and therefore have a high incidence of resistance in the subgingival microflora. The above features are in contrast to adult chronic periodontal disease and recurrence of disease. The subgingival microflora of refractory disease may be either predominantly gram-positive with elevated levels of Streptococcus intermedius or may be gram negative and contain elevated levels of the classical periodontal pathogens. In some cases serum IgG antibodies against Porphyromonas gingivalis are elevated and seem to decrease after therapy. Smoking may be an important factor in refractory periodontal disease. Treatment with directed antibiotic therapy as an adjunct to scaling and root planing retards the progression of disease for a limited time. Many questions are still not answered and suggestions are made for future directions in research.

Hemolytic, but not cell-invasive activity, of adenylate cyclase toxin is selectively affected by differential fatty-acylation in Escherichia coli.

Adenylate cyclase toxin from Bordetella pertussis requires posttranslational acylation of lysine 983 for the ability to deliver its catalytic domain to the target cell interior and produce cyclic adenosine monophosphate (cell-invasive activity) and to form transmembrane channels (hemolytic activity). When the toxin is expressed in Escherichia coli, it has reduced hemolytic activity, but comparable cell-invasive activity to that of adenylate cyclase toxin from B. pertussis. In contrast to the native protein from B. pertussis, which is exclusively palmitoylated, recombinant toxin from E. coli is acylated at lysine 983 with about 87% palmitoylated and the remainder myristoylated. Furthermore, the recombinant toxin contains an additional palmitoylation on approximately two-thirds of the lysines at position 860. These observations suggest that the site and nature of posttranslational fatty-acylation can be dictated by the bacterial host used for expression and can have a significant, but selective, effect on protein function.

Detection and incidence of the tetracycline resistance determinant tet(M) in the microflora associated with adult periodontitis.

Subgingival plaque samples were collected from 68 patients with adult periodontitis, enumerated on Trypticase-soy blood agar plates, with and without tetracycline at 4 micrograms/ml, and incubated anaerobically for 5 days. Each different colony morphotype was enumerated, and a representative colony was subcultured for identification and examined for the tetracycline resistance gene tet(M). Both PCR amplification and DNA hybridization, using a fragment of tet(M) from Tn1545, were used to detect tet(M). The PCR primers (5'-GACACGCCAGGACATATGG-3' and 5'-TGCTTTCCTCTTGTTCGAG-3') were chosen to amplify a 397 bp region of tet(M). Tetracycline-resistant bacteria represented approximately 12% of the total viable count. The percentage of tet(M)-positive bacteria in the tetracycline resistant microflora varied from < or = 0.05 to 83% (mean of 10%). tet(M) was detected in 60% of 204 tetracycline-resistant strains subcultured and identified. The tet(M) containing strains consisted of streptococci (55%, mainly S. intermedius, S. oralis, S. sanguis, and Streptococcus SM4), Actinomyces D01 (14%), Bifidobacterium D05 (11%), and Veillonella spp. (10%). Tetracycline-resistant strains in which tet(M) was not detected included the Prevotella and Bacteroides species (41%, mainly Bacteroides D28, P. intermedia, P. nigrescens, and P. oris). These results suggest that tet(M) is widely spread in the adult periodontal microflora, but it appears, with the exception of S. intermedius, to be mainly associated with microorganisms not considered to be periodontopathogens. Assessment of other tetracycline-resistant genes in oral organisms is needed to fully evaluate the nature of resistance to this antibiotic in the oral flora.

Treatment of subjects with refractory periodontal disease.

The aim of the present study was to evaluate the effect of non-surgical periodontal therapy with the adjunct of a selected antibiotic in subjects diagnosed with refractory periodontal disease. 21 subjects were selected for the study; all had a history of periodontal surgery, tetracycline therapy, and regular maintenance by a periodontist. When disease activity was detected, a bacterial sample was taken and a whole plaque susceptibility test was performed. Before the outcome of the susceptibility test the subjects were assigned to either antibiotic or placebo therapy. All subjects received scaling and rootplaning prior to antibiotic or placebo therapy. Based on the susceptibility test, subjects in the antibiotic group were treated either with Augmentin or clindamycin. The results demonstrated that in subjects with refractory periodontal disease there was no significant difference (N.S.) in the proportion of sites losing attachment before and after treatment (11.3% and 12.4%, respectively) over a 2-year post therapy observation period. However, the proportion of sites showing gain of attachment increased from 0.9% before therapy to 5.1% (p = 0.029) following selective antibiotic therapy when combined with scaling and rootplaning. The remainder of sites showed no change between pre- and post-therapy monitoring periods. The progression of attachment loss in the active sites could not be completely stopped over the entire 2-year period. After 12-15 months following therapy, there was a tendency towards new loss of attachment and an increase of pocket depth. However, all 4 subjects treated with placebo drug demonstrated continuous deterioration and had to be retreated. Although the proportion of sites losing attachment decreased from 5.1% to 2.3% (N.S.), the proportion of sites gaining attachment also decreased from 2.0% to 1.0% (N.S.). The results suggest that scaling and rootplaning together with selected antibiotic therapy repeated every 12-15 months may be beneficial for these subjects although it may not completely stop progressive attachment loss.

Sequencing of a tet(Q) gene isolated from Bacteroides fragilis 1126.

Recently, Tet Q, a tetracycline resistance determinant that confers resistance by a ribosome protection mechanism, was described and added to the two previously described classes, Tet M and Tet O. The first representative of this class, tetA(Q)1, was isolated from Bacteroides thetaiotaomicron DOT. We report the sequencing of a gene isolated from B. fragilis 1126 which also confers tetracycline resistance. Because of its high degree of identity (97%) with the tetA(Q)1 gene, we defined it as tetA(Q)2. MIC studies revealed that tetA(Q)2 provides a low level of resistance to tetracycline when cloned into Escherichia coli. The extensive homology between tetA(Q)1 and tetA(Q)2 supports the idea of a recent horizontal transfer of tet(Q) genes among Bacteroides spp.

Comparative analysis between a modified ultrasonic tip and hand instruments on clinical parameters of periodontal disease.

The goal of this study was to determine whether an ultrasonic scaler with a modified tip is as effective as a curet in providing supportive periodontal treatment for patients, based on clinical parameters of periodontal disease. Nine patients with 10 sites exhibiting probing pocket depth > or = 3 mm were treated at 0, 90, and 180 days in a single-blind, split-mouth design for supportive periodontal treatment with either Gracey curets (GC) or an ultrasonic scaler with a modified tip (MU). Clinical parameters included plaque index, gingival index, bleeding on probing, darkfield microscopy, and elastase presence. Probing pocket depths and attachment levels were measured using an electronic probe. Measurements of clinical parameters were taken at 0, 14, 45, 90, 135, and 180 days. The results showed that treatment with MU was as effective as treatment with GC in all clinical parameters measured. Both treatment modalities were effective in reducing the elastase levels. Instrumentation time was significantly reduced with the MU (3.9 minutes vs. 5.9 minutes, P < 0.05). The MU instrument effectively reduced the microbial environment in a significantly shorter time as compared to GC.