A MALDI-TOF MS database for fast identification of Vibrio spp. potentially pathogenic to marine mollusks

In mollusk aquaculture, a large number of Vibrio species are considered major pathogens. Conventional methods based on DNA amplification and sequencing used to accurately identify Vibrio species are unsuitable for monitoring programs because they are time-consuming and expensive. The aim of this study was, therefore, to develop the MALDI-TOF MS method in order to establish a rapid identification technique for a large panel of Vibrio species. We created the EnviBase containing 120 main spectra projections (MSP) of the Vibrio species that are potentially responsible for mollusk diseases, comprising 25 species: V. aestuarianus, V. cortegadensis, V. tapetis and species belonging to the Coralliilyticus, Harveyi, Mediterranei, and Orientalis clades. Each MSP was constructed by the merger of raw spectra obtained from three different media and generated by three collaborating laboratories to increase the diversity of the conditions and thus obtain a good technique robustness. Perfect discrimination was obtained with all of the MSP created for the Vibrio species and even for very closely related species as V. europaeus and V. bivalvicida. The new EnviBase library was validated through a blind test on 100 Vibrio strains performed by our three collaborators who used the direct transfer and protein extraction methods. The majority of the Vibrio strains were successfully identified with the newly created EnviBase by the three laboratories for both protocol methods. This study documents the first development of a freely accessible database exclusively devoted to Vibrio found in marine environments, taking into account the high diversity of this genus. KEY POINTS: • Development of a MALDI-TOF MS database to quickly affiliate Vibrio species. • Increase of the reactivity when faced with Vibrio associated with mollusk diseases. • Validation of MALDI-TOF MS as routine diagnostic tool.

External pH modulation during the growth of Vibrio tapetis, the aetiological agent of brown ring disease

AIMS

Brown ring disease (BRD) is an infection of the Manila clam Ruditapes philippinarum due to the pathogen Vibrio tapetis. During BRD, clams are facing immunodepression and shell biomineralization alteration. In this paper, we studied the role of pH on the growth of the pathogen and formulated hypothesis on the establishment of BRD by V. tapetis.

METHODS AND RESULTS

In this study, we monitored the evolution of pH during the growth of V. tapetis in a range of pH and temperatures. We also measured the pH of Manila clam haemolymph and extrapallial fluids (EPFs) during infection by V. tapetis. We highlighted that V. tapetis modulates the external pH during its growth, to a value of 7·70. During the development of BRD, V. tapetis also influences EPFs and haemolymph pH in vitro in the first hours of exposure and in vivo after 3 days of infection.

CONCLUSIONS

Our experiments have shown a close interaction between V. tapetis CECT4600, a pathogen of Manila clam that induces BRD, and the pH of different compartments of the animals during infection. These results indicate that the bacterium, through a direct mechanism or as a consequence of physiological changes encountered in the animal during infection, is able to interfere with the pH of Manila clam fluids. This pH modification might promote the infection process or at least create an imbalance within the animal that would favour its persistence. This last hypothesis should be tested in future experiment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first observation of pH modifications in the context of BRD and might orient future research on the fine mechanisms of pH modulation associated with BRD.

Efficacy of recent chemotherapy regimen in advanced small bowel carcinoma

15112

Background: Small bowel carcinoma (SBC) is a rare tumour. Very few data concerning the chemotherapy efficacy are published. The overall survivals previously reported were 8 to 14 months. The aim of the study was to evaluate the efficacy of recent chemotherapy regimen in advanced SBC. Methods: All the consecutive patients treated recently by first line chemotherapy for advanced SBC were included retrospectively in a multicentric study. Clinical and radiological evaluations were performed every 2 or 3 months according to WHO criteria. Chemotherapy was stopped in case of progression, severe toxicity or patient willing. Results: Fifty seven patients (33 men, 24 women), median age 56 years [32–83] treated from 1994 to 2006 in 10 institutions were included. Primary tumours were: duodenum n=35 (61%), jejunum n=14 (25%) and ileum n=8 (14%). Three patients had Crohn disease and one HNPCC syndrome. The tumour were locally advanced in 6 patients (10%), or with metastasis in 51 (90%), synchronous n=35 or metachronous n=16. The mains metastasis sites were peritoneal carcinomatosis in 29, liver in 19 and nodes in 13 patients. Sixteen patients have had an initial R0 surgery and 8 had received, before inclusion, adjuvant chemotherapy. The regimens used in first line were: FOLFOX n=21 (37%), LV5FU2-cisplatine n=13 (23%), LV5FU2 n=12 (21%), FOLFIRI n=10 (17%). Twenty five (44%) patients have had grade 3 or 4 toxicity. A toxic death occurred after a cure of FOLFOX. Chemotherapy was stopped in relation to toxicity in 7 (12%) patients. A dose reduction was done in 15 (26%) patients for a total of 16% of the cures. Tumor was measurable in 42 (73%) pts. A partial response was observed in 13 patients (31%), stabilisation in 14 (33%) and progression in 15 (36%). Thirty six (63%) pts had a second line chemotherapy. Time to treatment failure was 6 [1–21] months in all patients and 7 [2–19], 7 [2–20], 5 [1–21] and 4 [1–10] months according to treatment by FOLFOX, LV5FU2, FOLFIRI or LV5FU2-cisplatine respectively. Overall survival was 11 months [1–36]. Overall survival according to the primary localization were: duodenum: 9 [1–34], jejunum: 18 [3–32], ileum: 15 [4- 36]. Conclusions: Advanced SBC have a bad prognosis. The chemotherapy regimen used in colon cancer did not reach the same efficacy in SBC.

No significant financial relationships to disclose.

Genetic elements of Thermococcales

This minireview summarizes our current knowledge about archaeal genetic elements in the hyperthermophilic order Thermococcales in the phylum Euryarchaeota. This includes recent work on the first virus of Pyrococcus, PAV1, the discovery of novel unique virus morphotypes in hot deep-sea environments, and preliminary observations on novel cryptic plasmids. We also review the work accomplished over the last 5 years in the development of genetic tools for members of the Pyrococcus and Thermococcus genera, mainly in our laboratories.