Fine-scale monitoring of insecticide resistance in Aedes aegypti (Diptera: Culicidae) from Sri Lanka and modeling the phenotypic resistance using rational approximation.

BACKGROUND: The unplanned and intensified use of insecticides to control mosquito-borne diseases has led to an upsurge of resistance to commonly used insecticides. Aedes aegypti, the main vector of dengue, chikungunya, and Zika virus, is primarily controlled through the application of adulticides (pyrethroid insecticides) and larvicides (temephos). Fine spatial-scale analysis of resistance may reveal important resistance-related patterns, and the application of mathematical models to determine the phenotypic resistance status lessens the cost and usage of resources, thus resulting in an enhanced and successful control program. METHODS: The phenotypic resistance for permethrin, deltamethrin, and malathion was monitored in the Ae. aegypti populations using the World Health Organization (WHO) adult bioassay method. Mosquitoes' resistance to permethrin and deltamethrin was evaluated for the commonly occurring base substitutions in the voltage-gated sodium channel (vgsc) gene. Rational functions were used to determine the relationship between the kdr alleles and the phenotypic resistant percentage of Ae. aegypti in Sri Lanka. RESULTS: The results of the bioassays revealed highly resistant Ae. aegypti populations for the two pyrethroid insecticides (permethrin and deltamethrin) tested. All populations were susceptible to 5% malathion insecticide. The study also revealed high frequencies of C1534 and G1016 in all the populations studied. The highest haplotype frequency was detected for the haplotype CC/VV, followed by FC/VV and CC/VG. Of the seven models obtained, this study suggests the prediction models using rational approximation considering the C allele frequencies and the total of C, G, and P allele frequencies and phenotypic resistance as the best fits for the area concerned. CONCLUSIONS: This is the first study to our knowledge to provide a model to predict phenotypic resistance using rational functions considering kdr alleles. The flexible nature of the rational functions has revealed the most suitable association among them. Thus, a general evaluation of kdr alleles prior to insecticide applications would unveil the phenotypic resistance percentage of the wild mosquito population. A site-specific strategy is recommended for monitoring resistance with a mathematical approach and management of insecticide applications for the vector population.

Discussions about end-of-life care in nursing homes.

OBJECTIVE: To measure the frequency with which nursing home residents and their surrogates discuss with clinicians the resident's wishes concerning future treatment and to assess the influence of the Patient Self Determination Act (PSDA) on the frequency and nature of such discussions. DESIGN: Retrospective cohort study of residents admitted to nursing homes before and after the PSDA. SETTING: Six large (at least 120 licensed chronic care beds), randomly selected nursing homes in Connecticut. PARTICIPANTS: Six hundred randomly selected nursing home residents admitted during 1990 and 1994 to one of the six study nursing homes. MEASUREMENTS: Documented discussions concerning future treatment wishes were abstracted from residents' nursing home medical records. Participants in the discussion, as well as the timing (i.e., date) and content of the documented discussions were recorded. Sociodemographic and health status factors were also obtained from the medical record. RESULTS: A large majority of residents (71.5%) had no discussion of future treatment wishes documented in their medical record. However, the percentage of residents with documented discussions had increased since the implementation of the PSDA (36.7% post-PSDA vs 20.3% pre-PSDA). Of those in the post-PSDA cohort who had had discussions, 90% had only one discussion within the first year of admission, and more than half (58.1%) of those who had discussions discussed only life-support systems (cardiopulmonary resuscitation, artificial nutrition and hydration, and ventilation) rather than broader preferences for future treatment, including proxy decision-making. CONCLUSIONS: Despite the increased prevalence of discussions about future treatment wishes since the enactment of the PSDA, no discussions were documented for most residents. For those with documented discussions, such conversations occurred rarely and were narrow in scope, suggesting that residents' and families' roles in medical decision-making in nursing homes may be limited.

Quantization effects in digitally behaving circuit implementations of Kohonen networks.

Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation.

Antimicrobial activity of cytotoxic drugs may influence isolation of bacteria and fungi from blood cultures.

The potential antimicrobial activity of cyclophosphamide, vincristine, and adriamycin against Gram positive and negative bacteria and Candida albicans was examined. The time taken for different microbial inocula to turn a simulated blood culture positive in the presence of different concentrations of these drugs was measured. Doxorubicin retarded the growth of Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus sanguis in a concentration dependent manner. Cyclophosphamide and vincristine showed minimal antimicrobial activity. Escherichia coli and Pseudomonas aeruginosa were unaffected by any of the drugs. An inoculum dependent effect was seen with some combinations of microbial inocula and cytotoxic drug concentrations.

Legionnaires' disease in elderly people: the first sign of an outbreak in the community?

Legionella pneumophila is responsible for up to 5% of cases of community-acquired pneumonia and mainly affects people aged over 50 years. The confirmation of legionellosis in two elderly patients living close to each other prompted a search for other cases. A total of eleven subjects with legionnaires' disease was recognized. The clinical findings are described and the diagnosis of legionellosis is discussed. Environmental investigations pointed to a cooling tower in the local town centre as the probable source of infection.

Rapid method for differentiating strains of Branhamella catarrhalis.

The ability of Branhamella catarrhalis to cause nosocomial infections is a matter of some controversy. The API ZYM research kit for detecting 89 enzymes was used on 49 isolates of B catarrhalis to select enzymes of potential use in differentiating clinical isolates. Twenty nine enzymes were produced by all isolates (13 strongly positive) and many of these were esterases; 16 enzymes were not detected in any isolate (40 if a more stringent criterion was used). Twenty enzymes were selected to form a prototype biotyping panel which allowed 17 different patterns of reactivity to be recognised. Of the 49, 34 isolates were confined to the three commonest patterns. Only one isolate was untypable using this panel due to lack of reactivity. A kit with these 20 substrates may be sufficiently discriminatory to be useful in the rapid study of outbreaks of infection caused by B catarrhalis.