Latin America has experienced two of the largest cholera epidemics in modern history; one in 1991 and the other in 2010. However, confusion still surrounds the relationships between globally circulating pandemic Vibrio cholerae clones and local bacterial populations. We used whole-genome sequencing to characterize cholera across the Americas over a 40-year time span. We found that both epidemics were the result of intercontinental introductions of seventh pandemic El Tor V. cholerae and that at least seven lineages local to the Americas are associated with disease that differs epidemiologically from epidemic cholera. Our results consolidate historical accounts of pandemic cholera with data to show the importance of local lineages, presenting an integrated view of cholera that is important to the design of future disease control strategies.

BackgroundPseudomonas aeruginosa is an opportunistic pathogen with a high incidence of hospital infections that represents a threat to immune compromised patients. Genomic studies have shown that, in contrast to other pathogenic bacteria, clinical and environmental isolates do not show particular genomic differences. In addition, genetic variability of all the P. aeruginosa strains whose genomes have been sequenced is extremely low. This low genomic variability might be explained if clinical strains constitute a subpopulation of this bacterial species present in environments that are close to human populations, which preferentially produce virulence associated traits.ResultsIn this work, we sequenced the genomes and performed phenotypic descriptions for four non-human P. aeruginosa isolates collected from a plant, the ocean, a water-spring, and from dolphin stomach. We show that the four strains are phenotypically diverse and that this is not reflected in genomic variability, since their genomes are almost identical. Furthermore, we performed a detailed comparative genomic analysis of the four strains studied in this work with the thirteen previously reported P. aeruginosa genomes by means of describing their core and pan-genomes.ConclusionsContrary to what has been described for other bacteria we have found that the P. aeruginosa core genome is constituted by a high proportion of genes and that its pan-genome is thus relatively small. Considering the high degree of genomic conservation between isolates of P. aeruginosa from diverse environments, including human tissues, some implications for the treatment of infections are discussed. This work also represents a methodological contribution for the genomic study of P. aeruginosa, since we provide a database of the comparison of all the proteins encoded by the seventeen strains analyzed.

Vibrio cholerae O1 biotype El Tor (ET), the cause of the current 7th pandemic, has recently been replaced in Asia and Africa by an altered ET biotype possessing cholera toxin (CTX) of the classical (CL) biotype that originally caused the first six pandemics before becoming extinct in the 1980s. Until recently, the ET prototype was the biotype circulating in Peru; a detailed understanding of the evolutionary trend of V. cholerae causing endemic cholera in Latin America is lacking. The present retrospective microbiological, molecular, and phylogenetic study of V. cholerae isolates recovered in Mexico (n ‫؍‬ 91; 1983 to 1997) shows the existence of the pre-1991 CL biotype and the ET and CL biotypes together with the altered ET biotype in both epidemic and endemic cholera between 1991 and 1997. According to sero-and biotyping data, the altered ET, which has shown predominance in Mexico since 1991, emerged locally from ET and CL progenitors that were found coexisting until 1997. In Latin America, ET and CL variants shared a variable number of phenotypic markers, while the altered ET strains had genes encoding the CL CTX (CTX CL ) prophage, ctxB CL and rstR CL , in addition to resident rstR ET , as the underlying regional signature. The distinct regional fingerprints for ET in Mexico and Peru and their divergence from ET in Asia and Africa, as confirmed by subclustering patterns in a pulsed-field gel electrophoresis (NotI)-based dendrogram, suggest that the Mexico epidemic in 1991 may have been a local event and not an extension of the epidemics occurring in Asia and South America. Finally, the CL biotype reservoir in Mexico is unprecedented and must have contributed to the changing epidemiology of global cholera in ways that need to be understood.

Rhamnolipids produced by Pseudomonas aeruginosa are biosurfactants with a high biotechnological potential, but their extensive commercialization is limited by the potential virulence of P. aeruginosa and by restrictions in producing these surfactants in heterologous hosts. In this work, we report the characterization of P. aeruginosa strain ATCC 9027 in terms of its genome-sequence, virulence, antibiotic resistance, and its ability to produce mono-rhamnolipids when carrying plasmids with different cloned genes from the type strain PAO1. The genes that were expressed from the plasmids are those coding for enzymes involved in the synthesis of this biosurfactant (rhlA and rhlB), as well as the gene that codes for the RhlR transcriptional regulator. We confirm that strain ATCC 9027 forms part of the PA7 clade, but contrary to strain PA7, it is sensitive to antibiotics and is completely avirulent in a mouse model. We also report that strain ATCC 9027 mono-rhamnolipid synthesis is limited by the expression of the rhlAB-R operon. Thus, this strain carrying the rhlAB-R operon produces similar rhamnolipids levels as PAO1 strain. We determined that strain ATCC 9027 with rhlAB-R operon was not virulent to mice. These results show that strain ATCC 9027, expressing PAO1 rhlAB-R operon, has a high biotechnological potential for industrial mono-rhamnolipid production.

Pseudomonas aeruginosa is an opportunistic pathogen and is associated with nosocomial infections. Its ability to thrive in a broad range of environments is due to a large and diverse genome of which its accessory genome is part. The objective of this study was to characterize P. aeruginosa strains isolated from children who developed bacteremia, using pulse-field gel electrophoresis, and in terms of its genomic islands, virulence genes, multilocus sequence type, and antimicrobial susceptibility. Our results showed that P. aeruginosa strains presented the seven virulence genes: toxA, lasB, lecA, algR, plcH, phzA1, and toxR, a type IV pilin alleles (TFP) group I or II. Additionally, we detected a novel pilin and accessory gene, expanding the number of TFP alleles to group VI. All strains presented the PAPI-2 Island and the majority were exoU+ and exoS+ genotype. Ten percent of the strains were multi-drug resistant phenotype, 18% extensively drug-resistant, 68% moderately resistant and only 3% were susceptible to all the antimicrobial tested. The most prevalent acquired β-Lactamase was KPC. We identified a group of ST309 strains, as a potential high risk clone. Our finding also showed that the strains isolated from patients with bacteremia have important virulence factors involved in colonization and dissemination as: a TFP group I or II; the presence of the exoU gene within the PAPI-2 island and the presence of the exoS gene.