Transmission ecology of Trypanosoma cruzi by Rhodnius prolixus (Reduviidae: Triatominae) infesting palm-tree species in the Colombian Orinoco, indicates risks to human populations

BACKGROUND

Chagas disease, affecting approximately eight million individuals in tropical regions, is primarily transmitted by vectors. Rhodnius prolixus, a triatomine vector, commonly inhabits in ecotopes with diverse palm tree species, creating optimal conditions for vector proliferation. This study aims to explore the transmission ecology of Trypanosoma cruzi, the causative parasite of Chagas disease, by investigating the feeding patterns and natural infection rates of R. prolixus specimens collected from various wild palm species in the Colombian Orinoco region.

MATERIALS AND METHODS

To achieve this objective, we sampled 35 individuals from three palm species (Attalea butyracea, Acrocomia aculeata, and Mauritia flexuosa) in a riparian forest in the Casanare department of eastern Colombia, totaling 105 sampled palm trees. DNA was extracted and analyzed from 115 R. prolixus specimens at different developmental stages using quantitative PCR (qPCR) for T. cruzi detection and identification of discrete typing units. Feeding preferences were determined by sequencing the 12S rRNA gene amplicon through next-generation sequencing.

RESULTS

A total of 676 R. prolixus specimens were collected from the sampled palms. The study revealed variation in population densities and developmental stages of R. prolixus among palm tree species, with higher densities observed in A. butyracea and lower densities in M. flexuosa. TcI was the exclusive T. cruzi discrete typing unit (DTU) found, with infection frequency positively correlated with R. prolixus abundance. Insects captured in A. butyracea exhibited higher abundance and infection rates than those from other palm species. The feeding sources comprised 13 mammal species, showing no significant differences between palm species in terms of blood sources. However, Didelphis marsupialis and Homo sapiens were present in all examined R. prolixus, and Dasypus novemcinctus was found in 89.47% of the insects.

CONCLUSION

This study highlights the significance of wild palms, particularly A. butyracea, as a substantial risk factor for T. cruzi transmission to humans in these environments. High population densities and infection rates of R. prolixus were observed in each examined palm tree species.

Characterizing the blood microbiota of omnivorous and frugivorous bats (Chiroptera: Phyllostomidae) in Casanare, eastern Colombia

Bats are known reservoirs of seemingly-innocuous pathogenic microorganisms (including viruses, bacteria, fungi, and protozoa), which are associated with triggering disease in other zoonotic groups. The taxonomic diversity of the bats' microbiome is likely associated with species-specific phenotypic, metabolic, and immunogenic capacities. To date, few studies have described the diversity of bat blood microbial communities. Then, this study used amplicon-based next generation sequencing of the V4 hypervariable region of the 16S-rRNA gene in blood samples from omnivorous (n = 16) and frugivorous (n = 9) bats from the department of Casanare in eastern Colombia. We found the blood microbiota in bats to be composed of, among others, Bartonella and Mycoplasma bacterial genera which are associated with various disease phenotypes in other mammals. Furthermore, our results suggest that the bats' dietary habits might determine the composition and the persistence of some pathogens over others in their bloodstream. This study is among the first to describe the blood microbiota in bats, to reflect on co-infection rates of multiple pathogens in the same individual, and to consider the influence of diet as a factor affecting the animal's endogenous microbial community.

Trypanosoma cruzi Parasite Burdens of Several Triatomine Species in Colombia

Trypanosoma cruzi, the causal agent of Chagas disease, is mainly transmitted by insects of the Triatominae subfamily. In Colombia, there are 26 triatomine species, and 16 of them are naturally infected with the parasite. The parasite loads of naturally infected vectors can be significant in targeting specific species that can affect the epidemiology of the disease. Studying their ecology and behavior is vital to understand their role in T. cruzi transmission dynamics. We evaluated the parasite loads of 182 field-collected triatomines corresponding to 10 species in 13 departments across Colombia. We standardized a methodology to quantify T. cruzi DNA in these insects. We obtained a LOD (limit of detection) of 3.05 p-eq/mL. The 82% of triatomines we evaluated were positive for T. cruzi infection, with loads ranging from hundreds to millions of equivalent parasites per milliliter. Panstrongylus geniculatus, Rhodnius prolixus, and Triatoma dimidiata were the species with the highest loads of T. cruzi; however, other species whose role as vectors is still unknown were also found with high loads of parasites. Our results suggest the relevance of secondary species for T. cruzi transmission in Colombia. We hope our data can help improve entomological surveillance and vector control programs in the country and the region.

An overview of the trypanosomatid (Kinetoplastida: Trypanosomatidae) parasites infecting several mammal species in Colombia

BACKGROUND

Trypanosomatids are among the most critical parasites for public health due to their impact on human, animal, and plant health. Diseases associated with these pathogens manifest mainly in poor and vulnerable populations, where social, environmental, and biological factors modulate the case incidence and geographical distribution.

METHODS

We used Sanger and amplicon-based next-generation sequencing (NGS) in samples from different mammals to identify trypanosomatid infections in several departments in Colombia. A total of 174 DNA samples (18 humans, 83 dogs, and 73 wild mammals) were analyzed by conventional PCR using a fragment of the heat shock protein 70 (Hsp70) gene and Sanger sequenced the positive samples. Twenty-seven samples were sent for amplicon-based NGS using the same gene fragment. Data obtained were used to perform diversity analyses.

RESULTS

One hundred and thirteen samples were positive for PCR by Hsp70 fragment; these corresponded to 22.1% Leishmania spp., 18.6% L. amazonensis, 9.7% L. braziliensis, 14.2% L. infantum, 8% L. panamensis, and 27.4% Trypanosoma cruzi. Comparison of the identified species by the two sequencing technologies used resulted in 97% concordance. Alpha and beta diversity indices were significant, mainly for dogs; there was an interesting index of coinfection events in the analyzed samples: different Leishmania species and the simultaneous presence of T. cruzi and even T. rangeli in one of the samples analyzed. Moreover, a low presence of L. braziliensis was observed in samples from wild mammals. Interestingly, to our knowledge, this is the first report of Leishmania detection in Hydrochaeris hydrochaeris (capybara) in Colombia.

CONCLUSIONS

The Hsp70 fragment used in this study is an optimal molecular marker for trypanosomatid identification in many hosts and allows the identification of different species in the same sample when amplicon-based sequencing is used. However, the use of this fragment for molecular diagnosis through conventional PCR should be carefully interpreted because of this same capacity to identify several parasites. This point is of pivotal importance in highly endemic countries across South America because of the co-circulation of different genera from the Trypanosomatidae family. The findings show an interesting starting point for One Health approaches in which coevolution and vector-host interactions can be studied.

Towards environmental detection of Chagas disease vectors and pathogen

Chagas disease vector control relies on prompt, accurate identification of houses infested with triatomine bugs for targeted insecticide spraying. However, most current detection methods are laborious, lack standardization, have substantial operational costs and limited sensitivity, especially when triatomine bug densities are low or highly focal. We evaluated the use of FTA cards or cotton-tipped swabs to develop a low-technology, non-invasive method of detecting environmental DNA (eDNA) from both triatomine bugs and Trypanosoma cruzi for use in household surveillance in eastern Colombia, an endemic region for Chagas disease. Study findings demonstrated that Rhodnius prolixus eDNA, collected on FTA cards, can be detected at temperatures between 21 and 32 °C, when deposited by individual, recently blood-fed nymphs. Additionally, cotton-tipped swabs are a feasible tool for field sampling of both T. cruzi and R. prolixus eDNA in infested households and may be preferable due to their lower cost. eDNA detection should not yet replace current surveillance tools, but instead be evaluated in parallel as a more sensitive, higher-throughput, lower cost alternative. eDNA collection requires virtually no skills or resources in situ and therefore has the potential to be implemented in endemic communities as part of citizen science initiatives to control Chagas disease transmission.

Phylogenetic relationships and evolutionary patterns of the genus Psammolestes Bergroth, 1911 (Hemiptera: Reduviidae: Triatominae)

BACKGROUND

The evolutionary history of biodiversity in South America has been poorly studied in the seasonal dry tropical forest (SDTF). Species diversification in this ecosystem may have a twofold explanation. First, intermittent connections in the middle and late Pleistocene promoted species dispersal and/or genetic connectivity between lineages isolated in disjunct patches of forest. Second, allopatric speciation proceeded immediately after the formation and colonization of the SDTF in the Neogene. Here we studied the diversification of Psammolestes, a genus endemic of the SDTF and naturally infected with Trypanosoma cruzi (agent of Chagas disease), using a combination of phylogenetic, population genetics and niche model methods, and evaluated the reliability of the three morphospecies currently recognized.

RESULTS

Our multilocus analyses recovered P. coreodes and P. tertius in a monophyletic clade sister to P. arthuri. Species delimitation tests recovered these lineages as different species despite the shared genetic variation observed between P. coreodes and P. tertius in five genes. Also, genetic variation of the genus clustered in three groups that were consistent with the three morphospecies. Our demographic model predicted a scenario of divergence in absence of gene flow, suggesting that mixed haplotypes may be the result of shared ancestral variation since the divergence of the subtropical-temperate species P. coreodes and P. tertius. In contrast, the tropical species P. arthuri was highly differentiated from the other two in all tests of genetic structure, and consistently, the Monmonier's algorithm identified a clear geographical barrier that separates this species from P. coreodes and P. tertius.

CONCLUSIONS

We found three genetically structured lineages within Psammolestes that diverged in absence of gene flow in the late Miocene. This result supports a scenario of species formation driven by geographical isolation rather than by divergence in the face of gene flow associated with climatic oscillations in the Pleistocene. Also, we identified the Amazon basin as a climatic barrier that separates tropical from subtropical-temperate species, thus promoting allopatric speciation after long range dispersion. Finally, each species of Psammolestes occupies different climatic niches suggesting that niche conservatism is not crucial for species differentiation. These findings influence the current vector surveillance programs of Chagas disease in the region.

Species-dependent variation of the gut bacterial communities across Trypanosoma cruzi insect vectors

Triatomines (Hemiptera: Reduviidae) are the insect vectors of Trypanosoma cruzi, the causative agent of Chagas disease. The gut bacterial communities affect the development of T. cruzi inside the vector, making the characterization of its composition important in the understanding of infection development. We collected 54 triatomine bugs corresponding to four genera in different departments of Colombia. DNA extraction and PCR were performed to evaluate T. cruzi presence and to determine the discrete typing unit (DTU) of the parasite. PCR products of the bacterial 16S rRNA gene were pooled and sequenced. Resulting reads were denoised and QIIME 2 was used for the identification of amplicon sequence variants (ASVs). Diversity (alpha and beta diversity) and richness analyses, Circos plots, and principal component analysis (PCA) were also performed. The overall T. cruzi infection frequency was 75.9%, with TcI being the predominant DTU. Approximately 500,000 sequences were analyzed and 27 bacterial phyla were identified. The most abundant phyla were Proteobacteria (33.9%), Actinobacteria (32.4%), Firmicutes (19.6%), and Bacteroidetes (7.6%), which together accounted for over 90% of the gut communities identified in this study. Genera were identified for these main bacterial phyla, revealing the presence of important bacteria such as Rhodococcus, Serratia, and Wolbachia. The composition of bacterial phyla in the gut of the insects was significantly different between triatomine species, whereas no significant difference was seen between the state of T. cruzi infection. We suggest further investigation with the evaluation of additional variables and a larger sample size. To our knowledge, this study is the first characterization of the gut bacterial structure of the main triatomine genera in Colombia.

Identification of blood-feeding sources in Panstrongylus, Psammolestes, Rhodnius and Triatoma using amplicon-based next-generation sequencing

BACKGROUND

Triatomines are hematophagous insects that play an important role as vectors of Trypanosoma cruzi, the causative agent of Chagas disease. These insects have adapted to multiple blood-feeding sources that can affect relevant aspects of their life-cycle and interactions, thereby influencing parasitic transmission dynamics. We conducted a characterization of the feeding sources of individuals from the primary circulating triatomine genera in Colombia using amplicon-based next-generation sequencing (NGS).

METHODS

We used 42 triatomines collected in different departments of Colombia. DNA was extracted from the gut. The presence of T. cruzi was identified using real-time PCR, and discrete typing units (DTUs) were determined by conventional PCR. For blood-feeding source identification, PCR products of the vertebrate 12S rRNA gene were obtained and sequenced by next-generation sequencing (NGS). Blood-meal sources were inferred using blastn against a curated reference dataset containing the 12S rRNA sequences belonging to vertebrates with a distribution in South America that represent a potential feeding source for triatomine bugs. Mean and median comparison tests were performed to evaluate differences in triatomine blood-feeding sources, infection state, and geographical regions. Lastly, the inverse Simpson's diversity index was calculated.

RESULTS

The overall frequency of T. cruzi infection was 83.3%. TcI was found as the most predominant DTU (65.7%). A total of 67 feeding sources were detected from the analyses of approximately 7 million reads. The predominant feeding source found was Homo sapiens (76.8%), followed by birds (10.5%), artiodactyls (4.4%), and non-human primates (3.9%). There were differences among numerous feeding sources of triatomines of different species. The diversity of feeding sources also differed depending on the presence of T. cruzi.

CONCLUSIONS

To the best of our knowledge, this is the first study to employ amplicon-based NGS of the 12S rRNA gene to depict blood-feeding sources of multiple triatomine species collected in different regions of Colombia. Our findings report a striking read diversity that has not been reported previously. This is a powerful approach to unravel transmission dynamics at microgeographical levels.

Molecular detection and genotyping of intestinal protozoa from different biogeographical regions of Colombia

Background

Intestinal parasitic protozoa represent a serious problem of public health particularly in developing countries. Protozoa such as Blastocystis, Giardia intestinalis, Entamoeba histolytica and Cryptosporidium spp. are associated with diarrheal symptoms. In Colombia, there is little region-specific data on the frequency and circulating genotypes/species of these microorganisms. Therefore, the main objective of our study was to employ molecular detection and genotyping of G. intestinalis and Blastocystis, Cryptosporidium and Entamoeba spp. in samples from different biogeographical regions of Colombia.

Methods

We collected 649 human fecal samples from five biogeographical regions of Colombia: the Amazon, Andean, Caribbean, Orinoco and Pacific regions. Blastocystis, G. intestinalis, Cryptosporidium spp. and Entamoeba complex were detected by microscopy and conventional PCR. Molecular genotyping was conducted to identify Blastocystis subtypes (STs) (18s), G. intestinalis assemblages (triose phosphate isomerase and glutamate dehydrogenase) and Cryptosporidium species (18s). Genetic diversity indices were determined using dnasp.5.

Results

We detected G. intestinalis in 45.4% (n = 280) of samples, Blastocystis in 54.5% (n = 336) of samples, Cryptosporidium spp. in 7.3% (n = 45) of samples, Entamoeba dispar in 1.5% (n = 9) of samples, and Entamoeba moshkovskii in 0.32% (n = 2) of samples. Blastocystis STs 1–4, 8 and 9 and G. intestinalis assemblages AII, BIII, BIV, D and G were identified. The following Cryptosporidium species were identified: C. hominis, C. parvum, C. bovis, C. andersoni, C. muris, C. ubiquitum and C. felis. The Caribbean region had the highest frequency for each of the microorganisms evaluated (91.9% for G. duodenalis, 97.3% for Blastocystis, 10.8% for Cryptosporidium spp., 13.5% for E. dispar and 2.7% for E. moshkovskii). The Orinoco region had a high frequency of Blastocystis (97.2%) and the Andean region had a high frequency of G. intestinalis (69.4%). High and active transmission was apparent in several regions of the country, implying that mechanisms for prevention and control of intestinal parasitosis in different parts of the country must be improved.

Temporal Variation of the Presence of Rhodnius prolixus (Hemiptera: Reduviidae) Into Rural Dwellings in the Department of Casanare, Eastern Colombia

Rhodnius prolixus (Stål, 1859) is the major vector of Trypanosoma cruzi in Colombia and Venezuela. The species is strongly associated with high-altitude ecotopes, such as sylvatic palms (Attalea butyracea), where spatially and temporally stable infestations are established. We investigated temporal variation in regards to the presence of R. prolixus in rural dwellings in the department of Casanare (eastern Colombia) over a period of 12 mo. Thirty houses were sampled from January to December 2017 by installing Maria sensors, collecting triatomines through community entomological surveillance, and conducting a monthly search in each house. The collection of specimens from the houses varied significantly by month with the higher number of collections occurring in the low-rainfall season and the lower number of collections occurring in the months of increased precipitation. The proportions of males, females, and nymphs also varied significantly throughout the time period: nymphs (fifth instar only) were reported only during May, July, and September and significantly greater numbers of females than males were reported in the inspected dwellings in all months. Density, crowding, and colonization indices varied according to the season. A bloodmeal analysis revealed 17 different hosts. A total of 42 randomly selected R. prolixus specimens were subjected to molecular analyses for detection of T. cruzi DNA with 22 found positive (infection prevalence of 52%). In conclusion, we observed a high presence of R. prolixus (infected with T. cruzi) in dwellings close to native palm plantations. These findings indicate a high risk of vector transmission of T. cruzi for people in the study areas and challenges for the current vector control schemes in the region.

Trypanosoma cruzi infection, discrete typing units and feeding sources among Psammolestes arthuri (Reduviidae: Triatominae) collected in eastern Colombia

BACKGROUND

Chagas disease (CD) is caused by the protozoan parasite Trypanosoma cruzi, and is transmitted by hematophagous insects of the family Reduviidae. Psammolestes arthuri is a sylvatic triatomine distributed in Colombia and Venezuela which feeds on birds and there are a few studies that have reported Ps. arthuri naturally infected with T. cruzi. In Colombia, Ps. arthuri has been found in dwellings, making it important to evaluate its possible role in the T. cruzi transmission cycle. We aimed to evaluate the presence of T. cruzi and feeding sources of Ps. arthuri to elucidate new possible scenarios of T. cruzi transmission in the country.

METHODS

A total of 60 Ps. arthuri were collected in Arauca and Casanare, Colombia. We detected and genotyped T. cruzi and identified feeding sources. The frequency of the presence of T. cruzi was obtained and compared with different eco-epidemiological variables. Multiple correspondence analysis was conducted to explore associations between eco-epidemiological variables and the presence of T. cruzi; with these results, a logistic regression was used to determine statistical associations.

RESULTS

The infection rate of T. cruzi was 70.7% and was mostly associated with insect stage, sex, bird nest and feeding source. Regarding discrete typing units (DTUs), TcI was found in 54.7% samples, of which 21.7% (5/23) were TcI_Dom, 52.1% (12/23) had mixed infection (TcI_Dom-TcI_Sylv), and single infection with TcI_Sylv was not detected. Mixed infections (TcI/TcII-TcVI) were found in 9.52% (4/42) of the samples; of these, 14.2% (6/42) were TcII-TcVI. A total of 15 feeding sources were identified and the most frequent were: Cranioleuca baroni (35.85%), Homo sapiens (26.42%), Thraupis episcopus (11.32%) and Serinus albogularis (3.77%).

CONCLUSIONS

Although Ps. arthuri is mainly ornithophilic, this species may be feeding on other animals that can be infected with T. cruzi, possibly playing a role maintaining the zoonotic cycle of the parasite. Further studies with molecular techniques and wider sampling are needed to improve information regarding infection rates, ecotopes and habits with the aim of evaluating whether Ps. arthuri could be a potential T. cruzi vector.

Effect of the physiognomy of Attalea butyracea (Arecoideae) on population density and age distribution of Rhodnius prolixus (Triatominae)

BACKGROUND

Rhodnius prolixus Stål, 1859 is one of the main vectors of Trypanosoma (Schyzotrypanum) cruzi Chagas, 1909. In its natural forest environment, this triatomine is mainly found in palm tree crowns, where it easily establishes and develops dense populations. The aim of this study was to evaluate the effect of the physiognomy and reproductive status of Attalea butyracea on the population relative density and age structure of R. prolixus and to determine the vector's population stratification according to the vertical and horizontal profile of an A. butyracea forest.

METHODS

Using live bait traps, 150 individuals of A. butyracea with different physiognomy and 40 individuals with similar physiognomy (crown size, number of leaves, palm tree height, diameter at breast height, reproductive status) were sampled for triatomines in Yopal, Casanare-Colombia. Temperature and relative humidity were measured in the crown of the palm tree. Entomological indices and natural infection rates were also determined.

RESULTS

The relative population density of R. prolixus on natural A. butyracea groves is associated with the palm's height, number of leaves and crown volume. The young immature stages were present mostly at the crown's base and the advanced immature stages and adults were present mostly at the crown of the palm tree. This distribution correlates with the temperature stability and relative humidity in the base and the fluctuation of both environmental variables in the palm's crown. A higher density of R. prolixus was found as the palm tree height increased and as the distance of the palm with respect to the forest border decreased, especially towards anthropically intervened areas. A density index of 12.6 individuals per palm tree with an infestation index of 88.9% and a colonization index of 98.7% was observed. 85.2% was the infection index with T. cruzi.

CONCLUSION

The physiognomy of palm trees affects the relative population density and the distribution of developmental stages of R. prolixus. Therefore, they constitute a risk factor for the potential migration of infected insects from wild environments towards residential environments and the subsequent epidemiological risk of transmission of T. cruzi to people.

[Predictors of cesarean delivery in the Kinkanda general hospital in Matadi (Democratic Republic of Congo)]

OBJECTIVE

To identify predictors of cesarean delivery in the Kinkanda general hospital.

METHOD

Cross-sectional study conducted from 1st January 2012 to 31st December 2012, on women in labor who delivered at the maternity of Kinkanda. Predictors of cesarean delivery were identified by using binary logistic regression.

RESULTS

A uterine height of at least 33 cm at induction of labor (AOR 3.93 95% CI 2.04 to 7.59; p <0.001), primiparity (AOR 2.1 95%CI:1.06 to 4.15; p = 0.033), non-membership of the pregnant woman to this particular health center area (AOR 4.26 95%CI 2.16 to 8.42; p <0.001) and a weight of the newborn of at least 4000g (AOR 7.8 95%CI 2.3 to 26.44; p <0.001) were identified as risk factors for cesarean delivery.

CONCLUSION

Primiparity, uterine height of at least 33 cm, living in another health area than the Matadi area and fetal macrosomia are the main predictors of cesarean delivery during the year 2012 at the Kinkanda general hospital.

Burden of unidentifiable mycobacteria in a reference laboratory

Modern identification techniques at the genomic level have greatly improved the taxonomic knowledge of mycobacteria. In adjunct to nucleic acid sequences, mycobacterial identification has been endorsed by investigation of the lipidic patterns of unique mycolic acids in such organisms. In the present investigation, the routine use of high-performance liquid chromatography (HPLC) of mycolic acids, followed by the sequencing of the 16S rRNA, allowed us to select 72 mycobacterial strains, out of 1,035 screened, that do not belong to any of the officially recognized mycobacterial species. Most strains (i.e., 47) were isolated from humans, 13 were from the environment, 3 were from animals, and 9 were from unknown sources. The majority of human isolates were grown from the respiratory tract and were therefore most likely not clinically significant. Some, however, were isolated from sterile sites (blood, pleural biopsy, central venous catheter, or pus). Many isolates, including several clusters of two or more strains, mostly slow growers and scotochromogenic, presented unique genetic and lipidic features. We hope the data reported here, including the results of major conventional identification tests, the HPLC profiles of strains isolated several times, and the whole sequences of the 16S rRNA hypervariable regions of all 72 mycobacteria, may encourage reporting of new cases. The taxonomy of the genus Mycobacterium is, in our opinion, still far from being fully elucidated, and the reporting of unusual strains provides the best background for the recognition of new species. Our report also shows the usefulness of the integration of novel technology to routine diagnosis, especially in cases involving slow-growing microorganisms such as mycobacteria.

The Reoviridae family

The members of the Reoviridae family are extremely varied in host ranges and have such diverse natural histories that it is compelling to conclude that their structural asset and replication strategy are uniquely successful in evolutionary terms. It follows that their study addresses fundamental aspects of virology, besides the ones which are customary with important pathogens affecting humans, animals and plants. We deal here with the present taxonomy of the family Reoviridae and of its genera, two of which (Orbivirus and Rotavirus) are treated separately in this issue. Along with a cursory presentation of the remaining genera, we give a concise update of recent findings on the genus Orthoreovirus.

Tentative evidence of AIDS-associated biotype of Mycobacterium kansasii

Previous studies revealed heterogeneous behavior within the species Mycobacterium kansasii against commercially available DNA probes (Accuprobe M. kansasii culture identification test; Gen-Probe); several isolates, conventionally identified as M. kansasii, failed in fact to hybridize. Looking for a possible association with phenotypic features, we tested a fully characterized panel of 69 clinical isolates of M. kansasii (19 of which were Accuprobe negative) with a semiquantitative micromethod which tests for 19 enzymatic activities (Api Zym; BioMérieux). The strains were from 25 hospitals in 18 Italian towns; 20 isolates came from human immunodeficiency virus type 1-positive patients who fulfilled the Centers for Disease Control criteria for AIDS diagnosis. On the basis of the whole set of phenotypic traits, our strains clustered in two groups, allowing the differentiation of biotypes within the species. There was a perfect association between biotype 2 and hybridization failures with Accuprobe and a very significant association between this novel biotype 2 and AIDS status, which suggests that it differs in virulence.

Nosocomial diarrhoeas in a surgical division hyperendemic for Clostridium difficile: epidemiologic aspects emerging from an analysis of clinical records

Having previously shown that Clostridium difficile was responsible for an intense and protracted endemic of nosocomial diarrhoeas in the surgical division of a Tuscan hospital, we started a retrospective analysis on all records from the affected division, to cover a period of 15 months. A statistical description is given of a large series of nosocomial diarrhoeas, as well as direct estimates of their incidence rates in selected high risk subgroups. The situation described is epidemiologically unique, and its study tells how an endemic may reach a steady state of high nosocomial morbidity.

Epidemiological studies of Pseudomonas aeruginosa infections in leg ulcers

A 6-month prospective study was carried out in an angiology ward on patients with leg ulcers. Pseudomonas aeruginosa was isolated from about half of the samples from the patients. Of the isolates, 85 were serotyped, fingerprinted as to passive pyocin sensitivity and characterized for antibiotic susceptibility pattern. According to all criteria, the isolates belonged to six strains, two of which were clearly epidemic: one infected 11 patients yielding 52 identical isolates, the other infected 4 patients (19 isolates).

Age-related changes in the prevalence of precipitating antibodies to BK virus in infants and children

Nearly 1000 sera from children were tested by immunoelectro-osmophoresis against BK virus, and age-specific prevalence rates were estimated from birth until the age of 12 years. Declining rates during the first 12 months showed the waning of passive immunity, which at birth reflects the mother's immune status. The changes of prevalence suggested that the peak incidence of primary infections occurred at about 2 years, with an estimated peak annual rate of 24.6%.

[Role of viruses in acute gastroenteritis]

In a two years screening carried out on Florentine children we confirmed that Rotaviruses are the most important ethiological agents of acute gastroenteritis in infants less than two years old, irrespective of sex. We had evidence that Rotavirus diarrhea does not occur with the same incidence every year. Rotavirus gastroenteritis is characterized by profuse diarrhea, vomiting, fever and often by respiratory symptoms. Severe complications have not been observed.

Immunoelectroosmophoresis for the human papovavirus BK

The reaction between BK virus and its antibodies may well be visualized with immunoelectroosmophoresis (IEOP). Serum antibody levels may be compared or graded by reacting them against a continuous antigen front. In seroepidemiologic surveys IEOP compares favourably with hemagglutination inhibition in terms of sensitivity, practicability and reproducibility. Technical conditions are described which are suitable for antigen detection, quantification and identification.

[Serodiagnosis of rotavirus infections in gastroenteritis of infants]

We report the use of the line immunoelectroosmophoresis (LIEOP), a modification of the immunoelectroosmophoresis (IEOP), for the serodiagnosis of rotavirus infection, in comparison with the complement fixation test. We tested 17 paired and 29 single sera from hospitalized children affected by acute gastroenteritis; rotavirus had been searched in the stools both by electron microscopy and IEOP. The LIEOP showed seroconversion in all the 11 cases with positive stools and also in 5 out of 5 patients whose stool sample had been negative. Either we had not been able to detect the virus, or there was an intervening (nosocomial) rotavirus infection. All sera which were reactive by complement fixation with bovine rotavirus were also reactive by LIEOP. Some of the sera which reacted by LIEOP, both with the homologous and the heterologous antigen, were negative by complement fixation.

[Pyocin typing of 111 strains of Pseudomonas aeruginosa isolated in Tuscany, using the Gillies and Govan method]

Pseudomonas aeruginosa strains from Tuscany have been typed for pyocine production against Govan and Gillies' extended set of indicator strains; results have been expressed following a binary code. Among 111 strains only 6 could not be typed; the remaining 105 strains (94.6%) presented 59 different patterns, 44 of which were represented by one isolate only. The most commonly encountered pattern (n. 8045, corresponding to Govan and Gillies' subtype 1e) was shared by 13 strains. Isolates from outpatients or from the environment tended to a uniform distribution of pyocine patterns; those from two different hospitals tended to group into distinct subtypes.

Surface glycosaminoglycans and calcium distribution in 3T3 cells

Resting 3T3 cells have relatively more sulphated glycosaminoglycans and Ca2+ in their cell coat than do growing or SV40-virus-transformed cells. It is suggested that the different Ca2+-binding capacity controls cellular activities by affecting the distribution of Ca2+ between the intra- and ecto-cellular compartments.

Biometrical implications of factorial experiments for the study of lymphocyte mitogenic response

Lymphocyte responsiveness to mitogens is affected by a number of experimental variables; the latter may be conveniently studied several at a time, following a factorial design that allows the complete evaluation of the effects of each variable and of their interplays. Statistical inferences may be drawn through an analysis of variance, provided that the data conform to the underlying model, i.e. that the effects are additive and that the errors are normally distributed and homoscedastic. Thymidine incorporation data should first be transformed to log cpm; the effects on the metameter may then be assumed to be additive, and their errors approach normality; the error variances may be affected by the experimental variables involved, so that the homogeneity of the error must be checked before relying on the pooled estimate of the error for parametric tests of significance. The above considerations have been illustrated with factorial experiments on [3H]TdR incorporation by rabbit spleen cells stimulated with varying amounts of PHA-P or PHA-M, under a variety of culture conditions.

[Multivariate analysis of aminoacyl-tRNA synthetase activities of liver and hepatomas (author's transl)]

Data on the aminoacyl-tRNA synthetase activities in normal liver and in three transplantable rat hepatomas, viz Yoshida's AH 130 and Morris's 5123C and 7793, were studied by means of factor analysis, a powerful technique of multivariate analysis particularly suitable foridentifying factors which theoretically may account for the pattern of interrelations between several variables. The analysis has been performed on 51 patterns of enzyme activities, covering 17 out of the 20 aminoacyl-tRNA synthetases; 80% on average of the total variability of the 17 enzyme activities may be accounted for by the first 4 factors extracted. The enzymes seem to fall into different groups, depending on their relationship with the factors thus identified. The results suggest that enzymes belonging to the same group share a common control mechanism, and are independent of the enzymes belonging to different groups, both in normal liver and in hepatomas.