Biology subjects

Lourenco, J.

Publications and source records attributed to Lourenco, J..

40 records · Page 3Linked to original sources

bioRxiv2017

Vaccination Can Drive An Increase In Frequencies Of Antibiotic Resistance Among Non-Vaccine Serotypes Of Streptococcus pneumoniae

The bacterial pathogen Streptococcus pneumoniae is a major public health concern, being responsible for more than 1.5 million deaths annually through pneumonia, meningitis and septicemia. In spite of vaccination efforts, pneumococcal carriage and disease remain high, since available vaccines target only a subset of serotypes and vaccination is often accompanied by a rise in non-vaccine serotypes. Epidemiological studies suggest that such a change in serotype frequencies is often coupled with an increase of antibiotic resistance among non-vaccine serotypes. Building on previous multi-locus models for bacterial pathogen population structure, we have developed a theoretical framework incorporating variation in serotype and antibiotic resistance to examine how their associations may be affected by vaccination. Using this framework, we find that vaccination can result in rapid increase in frequency of pre-existing resistant variants of non-vaccine serotypes due to the removal of competition from vaccine serotypes.

epidemiology↗

bioRxiv2017

Emergence and persistence of the Chikungunya virus East-Central-South-African genotype in Northeast Brazil

We investigate an outbreak of exanthematous illness in Maceio, Alagoas, using molecular surveillance. Of 273 samples, 76% tested RT-qPCR positive for Chikungunya virus. Phylogenetic analysis reveals that the outbreak was caused by the East-Central-South-African genotype, and that this lineage has likely persisted since mid-2014 in Northeast Brazil.\n\nArticle summary lineTransmission of the Chikungunya virus East-Central-South-African genotype has been ongoing in the Northeast region of Brazil since mid-2014.

epidemiology↗

bioRxiv2017

Epidemiological and ecological determinants of Zika virus transmission in an urban setting.

Zika has emerged as a global public health concern. Although its rapid geographic expansion can be attributed to the success of its Aedes mosquito vectors, local epidemiological drivers are still poorly understood. The city of Feira de Santana played a pivotal role in the early phases of the Chikungunya and Zika epidemics in Brazil. Here, using a climate-driven transmission model, we show that low Zika observation rates and a high vectorial capacity in this region were responsible for a high attack rate during the 2015 outbreak and the subsequent decline in cases in 2016, when the epidemic was peaking in the rest of the country. Our projections indicate that the balance between the loss of herd-immunity and the frequency of viral re-importation will dictate the transmission potential of Zika in this region in the near future. Sporadic outbreaks are expected but unlikely to be detected under current surveillance systems.

epidemiology↗

bioRxiv2016

Signatures of non-neutral processes within the population structure of Streptococcus pneumoniae

Populations of Streptococcus pneumoniae (SP) are typically structured into groups of closely related organisms or lineages, but it is not clear whether they are maintained by selection or neutral processes. Here, we attempt to address this question by applying a machine learning technique to SP whole genomes. Our results indicate that lineages evolved through immune selection on the groEL chaperone protein. The groEL protein is part of the groESL operon and enables a large range of proteins to fold correctly within the physical environment of the nasopharynx, thereby explaining why lineage structure is so stable within SP despite high levels of genetic transfer. SP is also antigenically diverse, exhibiting a variety of distinct capsular serotypes. Associations exist between lineage and capsular serotype but these can be easily perturbed, such as by vaccination. Overall, our analyses indicate that the evolution of SP can be conceptualized as the rearrangement of modular functional units occurring on several different timescales under different pressures: some patterns have locked in early (such as the epistatic interactions between groESL and a constellation of other genes) and preserve the differentiation of lineages, while others (such as the associations between capsular serotype and lineage) remain in continuous flux.

epidemiology↗