Isolates of Candida albicans that differ in virulence for mice elicit strain-specific antibody-mediated protective responses

Three distinct isolates of Candida albicans were used to establish systemic and oral infections in inbred mice that are genetically resistant or susceptible to tissue damage. Patterns of infection differed significantly between both yeasts and mouse strains. Systemic infection conferred significant protection against re-challenge with the homologous, but not the heterologous yeast; however, the protective effect was more evident in the tissue-susceptible CBA/CaH mice than in the resistant BALB/c strain. In contrast, oral infection induced protection against both homologous and heterologous oral challenge, although this was significant only in the CBA/CaH mice. CBA/CaH mice produced antibodies of both IgG1 and IgG2a subclasses, whereas BALB/c mice produced predominantly IgG1. Western blotting demonstrated considerable differences between epitopes recognised by serum antibodies from mice of both strains after immunisation with each of the three yeasts. Thus, different strains of yeast show considerable specificity in antibody responses elicited by either systemic or oral infection. (c) 2005 Elsevier SAS. All rights reserved.

Oral viral infections and the therapeutic use of antiviral agents in dentistry

This paper reviews the current concepts of viral classification, infection and replication. The clinical presentation of common oral viral infections encountered in the dental practice are discussed, including: herpes simplex virus types 1 and 2; Epstein-Barr virus; varicella-zoster virus; Coxsackie virus; human papilloma virus; and human immunodeficiency virus. The diagnosis, principles of management and pharmacological agents available for the treatment of oral viral infections are also discussed.

Canine model for investigating the impact of oral enrofloxacin on commensal coliforms and colonization with multidrug-resistant Escherichia coli

A model was developed in dogs to determine the impact of oral enrofloxacin administration on the indigenous coliform population in the gastrointestinal tract and subsequent disposition to colonization by a strain of multidrug-resistant Escherichia coli (MDREC). Dogs given a daily oral dose of 5 mg enrofloxacin kg(-1) for 21 consecutive days showed a significant decline in faecal coliforms to levels below detectable limits by 72 In of administration. Subsequently, faecal coliforms remained suppressed throughout the period of enrofloxacin dosing. Upon termination of antibiotic administration, the number of excreted faecal coliforms slowly returned over an 8-day period, to levels comparable to those seen prior to antibiotic treatment. Enrofloxacin-treated dogs were more effectively colonized by MDREC, evidenced by a significantly increased count of MDREC in the faeces (7.1 +/- 1.5 log(10) g(-1)) compared with non-antibiotic-treated dogs (5.2 +/- 1.2; P = 0.003). Furthermore, antibiotic treatment also sustained a significantly longer period of MDREC excretion in the faeces (26.8 +/- 10.5 days) compared with animals not treated with enrofloxacin (8.5 +/- 5.4 days; P = 0.0215). These results confirm the importance of sustained delivery of an antimicrobial agent to maintain and expand the colonization potential of drug-resistant bacteria in vivo, achieved in part by reducing the competing commensal coliforms in the gastrointestinal tract to below detectable levels in the faeces. Without in vivo antimicrobial selection pressure, commensal coliforms dominated the gastrointestinal tract at the expense of the MDREC population. Conceivably, the model developed could be used to test the efficacy of novel non-antibiotic strategies aimed at monitoring and controlling gastrointestinal colonization by multidrug-resistant members of the Enterobacteriaceae that cause nosocomial infections.

Oral candidosis and the therapeutic use of antifungal agents in dentistry

This paper reviews the current concepts of mycology and candidal infections as they relate to the oral cavity. Proposed classification for the presentation of oral candidosis is outlined as are examples of these topical infections, such as erythematous, pseudomembranous and hyperplastic candidosis, as well as angular chelitis and median rhomboid glossitis. The diagnosis and principles of management of oral candidosis are discussed, the therapeutic agents available for the management of these infections are presented and a treatment protocol for the management of patients with oral candidosis is given.

Wolbachia infections of tephritid fruit flies: molecular evidence for five distinct strains in a single host species

Endosymbiotic bacteria of the genus Wolbachia are widespread among arthropods and can induce cytoplasmic incompatibility, thelytokous parthenogenesis, male-killing or feminization in their hosts. Here, we report phylogenetic relationships of Wolbachia in tephritid fruit flies based on wsp gene sequences. We also report, for the first time, five distinct strains of Wolbachia in Bactrocera ascita sp. B. Four of the five Wolbachia strains found in this species were in the same groups as those found in other tephritid fruit flies, suggesting possible horizontal transmission of Wolbachia from other fruit flies into B. ascita sp. B. The unreliability of wsp-specific group primers demonstrated in this study suggests that these primers might be useful only for preliminary identification of Wolbachia. Final determination of group affiliation needs to be verified with wsp sequence data.

Wolbachia infections of phlebotomine sand flies (Diptera: Psychodidae)

Old and New World phlebotomine sand fly species were screened for infection with Wolbachia, intracellular bacterial endosymbionts found in many arthropods and filarial nematodes. Of 53 samples representing 15 species, nine samples of four species were found positive for Wolbachia by polymerase chain reaction amplification using primers for the Wolbachia surface protein (wsp) gene. Five of the wsp gene fragments from four species were cloned, sequenced, and used for phylogenetic analysis. These wsp sequences were placed in three different clades within the arthropod associated Wolbachia (groups A and B), suggesting that Wolbachia has infected sand flies on more than one occasion. Two distantly related sand fly species, Lutzomyia (Psanthyromyia) shannoni (Dyar) and Lutzomyia (Nyssomyia) whitmani (Antunes & Coutinho), infected with an identical Wolbachia strain suggest a very recent horizontal transmission.

Wolbachia infections are distributed throughout insect somatic and germ line tissues

Wolbachia are intracellular microorganisms that form maternally-inherited infections within numerous arthropod species. These bacteria have drawn much attention, due in part to the reproductive alterations that they induce in their hosts including cytoplasmic incompatibility (CI), feminization and parthenogenesis. Although Wolbachia's presence within insect reproductive tissues has been well described, relatively few studies have examined the extent to which Wolbachia infects other tissues. We have examined Wolbachia tissue tropism in a number of representative insect hosts by western blot, dot blot hybridization and diagnostic PCR. Results from these studies indicate that Wolbachia are much more widely distributed in host tissues than previously appreciated. Furthermore, the distribution of Wolbachia in somatic tissues varied between different Wolbachia/host associations. Some associations showed Wolbachia disseminated throughout most tissues while others appeared to be much more restricted, being predominantly limited to the reproductive tissues. We discuss the relevance of these infection patterns to the evolution of Wolbachia/host symbioses and to potential applied uses of Wolbachia.

Wolbachia infections and arthropod reproduction

Wolbachia is an intracellular bacterium that is almost exclusively maternally transmitted, and its reproductive effects favor transmission of the intracellular bacterial agent at the expense of the arthropod population that is not infected. Wolbachia can cause cytoplasmic incompatibility, parthenogenesis and feminization in many arthropods.

Wolbachia infections and the expression of cytoplasmic incompatibility in Drosophila sechellia and D. mauritiana

Various stocks of Drosophila mauritiana and D. sechellia were found to be infected with Wolbachia, a Rickettsia-like bacterium that is known to cause cytoplasmic incompatibility and other reproductive abnormalities in arthropods. Testing for the expression of cytoplasmic incompatibility in these two species showed partial incompatibility in D. sechellia but no expression of incompatibility in D. mauritiana. To determine whether absence of cytoplasmic incompatibility in D. mauritiana was due to either the bacterial or host genome, we transferred bacteria from D. mauritiana into an uninfected strain of D. simulans, a host species known to express high levels of incompatibility with endogenous Wolbachia. We also performed the reciprocal transfer of the natural D. simulans Riverside infection into a tetracycline-treated stock of D. mauritiana. In each case, the ability to express incompatibility was unaltered by the different host genetic background. These experiments indicate that in D. simulans and D. mauritiana expression of the cytoplasmic incompatibility phenotype is determined by the bacterial strain and that D. mauritiana harbors a neutral strain of Wolbachia.

The use of calcium hydroxide, antibiotics and biocides as antimicrobial medicaments in endodontics

Bacteria have been implicated in the pathogenesis and progression of pulp and periapical diseases. The primary aim of endodontic treatment is to remove as many bacteria as possible from the root canal system and then to create an environment in which any remaining organisms cannot survive. This can only be achieved through the use of a combination of aseptic treatment techniques, chemomechanical preparation of the root canal, antimicrobial irrigating solutions and intracanal medicaments. The choice of which intracanal medicament to use is dependent on having an accurate diagnosis of the condition being treated, as well as a thorough knowledge of the type of organisms likely to be involved and. their mechanisms of growth and survival. Since the disease is likely to have been caused by the presence of bacteria within the root canal, the use of an antimicrobial agent is essential. Many medicaments have been used in an attempt to achieve the above aims, but no single preparation has been found to be completely predictable or effective. Commonly used medicaments include calcium hydroxide, antibiotics; non-phenolic biocides, phenolic biocides and iodine compounds. Each has advantages and disadvantages, and further research is required to determine which is best suited for root canal infections.

Task Complexity and Variation in L2 Learner’s Oral Discourse

There are many factors which affect the L2 learner’s performance at the levels of phonology, morphology and syntax. Consequently when L2 learners attempt to communicate in the target language, their language production will show systematic variability across the above mentioned linguistic domains. This variation can be attributed to some factors such as interlocutors, topic familiarity, prior knowledge, task condition, planning time and tasks types. This paper reports the results of an on going research investigating the issue of variability attributed to the task type. It is hypothesized that the particular type of task learners are required to perform will result in variation in their performance. Results of the statistical analyses of this study investigating the issue of variation in the performance of twenty L2 learners at the English department of Tabriz University provided evidence in support of the hypothesis that performance of L2 learners show systematic variability attributed to task.

Minocycline and oral pigmentation

Minocycline is a semisynthetic tetracycline used in the treatment of inflammatory acne because of its broad spectrum of activity, less common development of resistant organisms, and its anti-inflammatory effects. A number of adverse reactions are reported, including skin and oral pigmentation. This paper details the pharmacology of minocycline and describes the pigmentation and likely mechanisms active in both hard and soft tissues. Oral pigmentation usually involves the hard tissues only and presents typically as a discrete band occupying the central zone of the alveolar mucosa and palate. As with other sites, it may persist following withdrawal of the drug. Early recognition by the dental practitioner may allow an alternative form of therapy to be sought, minimizing the likelihood of a longterm aesthetic problem.