Substrate-independent luminescent phage-based biosensor to specifically detect enteric bacteria such as E. coli

Water quality is a major safety consideration in environments that are impacted by human activity. The key challenge of the COMBITOX project is to develop a unique instrument that can accommodate several biodetector systems (see the accompanying COMBITOX papers) able to detect different pollutants such as bacteria, toxins, and heavy metals. The output signal chosen by our consortium is based on luminescence detection. Our group recently developed phage-based biosensors using gfp as a reporter gene to detect enteric bacteria in complex environments such as sea water, and the main challenge we faced was to adapt our biodetector to a luminescent signal that could fit the COMBITOX project requirements. Another key point was to use a substrate-independent reporter system in order to avoid substrate addition in the detection prototype. This paper describes the development of a phage-based biodetector using a luminescent and substrate-independent output to detect some enteric bacteria, such as Escherichia coli, in water samples. We have successfully engineered various prototypes using the HK620 and HK97 bacteriophages that use different packaging systems, and both proved functional for the integration of the full luxCDABE operon controlled by two different bacterial promoters. We show that the luxCDABE operon controlled by the PrplU bacterial promoter is the most efficient in terms of signal emission. The emission of luminescence is specific and allows the detection of 10⁴ bacteria per milliliter in 1.5 h post-infection with neither a concentration nor enrichment step.

Depth of insertion of right internal jugular central venous catheter: Comparison of topographic and formula methods

BACKGROUND

Central venous catheters (CVCs) are inserted in many critically ill patients, but there is no gold standard in estimating their approximate depth of insertion. Many techniques have been described in literature. In this study, we compare the topographic method with the standard formula technique.

MATERIALS AND METHODS

260 patients, in whom central venous catheterization was warranted, were randomly assigned to either topographic method or formula method (130 in each group). The position of the CVC tip in relation to carina was measured on a postprocedure chest X-ray. The primary endpoint was the need for catheter repositioning.

RESULTS

The majority of the CVCs tips positioned by the formula method were situated below the carina, and 68% of these catheters required repositioning after obtaining postprocedure chest X-ray (P < 0.001).

CONCLUSION

The topographic method is superior to formula approach in estimating the depth of insertion of right internal jugular CVCs.

Phage-Based Fluorescent Biosensor Prototypes to Specifically Detect Enteric Bacteria Such as E. coli and Salmonella enterica Typhimurium

Water safety is a major concern for public health and for natural environment preservation. We propose to use bacteriophages to develop biosensor tools able to detect human and animal pathogens present in water. For this purpose, we take advantage of the highly discriminating properties of the bacteriophages, which specifically infect their bacterial hosts. The challenge is to use a fluorescent reporter protein that will be synthesized, and thus detected, only once the specific recognition step between a genetically modified temperate bacteriophage and its bacterial host has occurred. To ensure the accuracy and the execution speed of our system, we developed a test that does not require bacterial growth, since a simple 1-hour infection step is required. To ensure a high sensitivity of our tool and in order to detect up to a single bacterium, fluorescence is measured using a portable flow cytometer, also allowing on-site detection. In this study, we have constructed and characterized several "phagosensor" prototypes using the HK620 bacteriophage and its host Escherichia coli TD2158 and we successfully adapted this method to Salmonella detection. We show that the method is fast, robust and sensitive, allowing the detection of as few as 10 bacteria per ml with no concentration nor enrichment step. Moreover, the test is functional in sea water and allows the detection of alive bacteria. Further development will aim to develop phagosensors adapted on demand to the detection of any human or animal pathogen that may be present in water.

Availability of essential medicines: A primary health care perspective

The present study was undertaken to assess the availability of the essential medicines to the people of Kunijarla, Khammam district, AP. This was done in two steps: 1) Comparison of PHC-EML (primary health care essential medicines list) with AP-EML (Andhra Pradesh essential medicines list) and NEML (National essential medicines list); and 2) Assessment of availability of the listed medicines in adequate quantity to meet the needs of people of kunijarla. Results showed that the PHC-EML is on par with AP-EML and NEML. The hospital has 100% availability of the listed medicines; however, there was a need for certain add-on drugs like phenytoin tablets, valproic acid, and activated charcoal since they were prescribed frequently and were not included in PHC-EML. All the drugs which were listed in PHC-EML were being used and none were considered as non-utility supply. Suggestions were given for the revision of PHC-EML according to the criteria for identifying medicines for inclusion in the revised list which was mentioned in NEML.

Study of the thiol/disulfide redox systems of the anaerobe Desulfovibrio vulgaris points out pyruvate:ferredoxin oxidoreductase as a new target for thioredoxin 1

Sulfate reducers have developed a multifaceted adaptative strategy to survive against oxidative stresses. Along with this oxidative stress response, we recently characterized an elegant reversible disulfide bond-dependent protective mechanism in the pyruvate:ferredoxin oxidoreductase (PFOR) of various Desulfovibrio species. Here, we searched for thiol redox systems involved in this mechanism. Using thiol fluorescent labeling, we show that glutathione is not the major thiol/disulfide balance-controlling compound in four different Desulfovibrio species and that no other plentiful low molecular weight thiol can be detected. Enzymatic analyses of two thioredoxins (Trxs) and three thioredoxin reductases allow us to propose the existence of two independent Trx systems in Desulfovibrio vulgaris Hildenborough (DvH). The TR1/Trx1 system corresponds to the typical bacterial Trx system. We measured a TR1 apparent K(m) value for Trx1 of 8.9 μM. Moreover, our results showed that activity of TR1 was NADPH-dependent. The second system named TR3/Trx3 corresponds to an unconventional Trx system as TR3 used preferentially NADH (K(m) for NADPH, 743 μM; K(m) for NADH, 5.6 μM), and Trx3 was unable to reduce insulin. The K(m) value of TR3 for Trx3 was 1.12 μM. In vitro experiments demonstrated that the TR1/Trx1 system was the only one able to reactivate the oxygen-protected form of Desulfovibrio africanus PFOR. Moreover, ex vivo pulldown assays using the mutant Trx1(C33S) as bait allowed us to capture PFOR from the DvH extract. Altogether, these data demonstrate that PFOR is a new target for Trx1, which is probably involved in the protective switch mechanism of the enzyme.

A coverage evaluation survey of JE vaccination in two districts of Karnataka

A coverage evaluation survey was conducted in Mandya and Koppal districts of Karnataka state following the Japanese Encephalitis (JE) vaccination campaign. The purposes of the survey were to assess coverage of children in target age group by JE vaccination and to assess adverse events following immunisation against JE, the knowledge of health care providers and community about JE & mass vaccination for JE. The study design consisted of both quantitative and qualitative methods. The quantitative data was used to know the coverage levels for children. The qualitative data collected through interviews of head of the family in the sample households, selected health care workers using a structured pretested questionnaire. The standard cluster sampling method was used for selecting the sample of children to be evaluated. In Mandya district the evaluation showed 92% coverage in the selected sample of 313 children against the reported 83.85%. In Koppal district the evaluation showed 70% coverage, among the selected sample of 251 children, against the reported coverage of 69.8%. The incidence of adverse events was 4% in Mandya sample and 6.37% in Koppal sample. In Mandya district, about 42% of households had knowledge of JE. About 68% of households had prior knowledge of the immunization day. In Koppal district, the survey has revealed that only 19.85% of the heads of household had the knowledge of JE and 48.53% had the knowledge of JE vaccination before the day of vaccination campaign.