Serotonin is an important neuroactive substance in all the parasitic helminths. In Schistosoma mansoni, serotonin is strongly myoexcitatory; it potentiates contraction of the body wall muscles and stimulates motor activity. This is considered to be a critical mechanism of motor control in the parasite, but the mode of action of serotonin is poorly understood. Here we provide the first molecular evidence of a functional serotonin receptor (Sm5HTR) in S. mansoni. The schistosome receptor belongs to the G protein-coupled receptor (GPCR) superfamily and is distantly related to serotonergic type 7 (5HT7) receptors from other species. Functional expression studies in transfected HEK 293 cells showed that Sm5HTR is a specific serotonin receptor and it signals through an increase in intracellular cAMP, consistent with a 5HT7 signaling mechanism. Immunolocalization studies with a specific anti-Sm5HTR antibody revealed that the receptor is abundantly distributed in the worm's nervous system, including the cerebral ganglia and main nerve cords of the central nervous system and the peripheral innervation of the body wall muscles and tegument. RNA interference (RNAi) was performed both in schistosomulae and adult worms to test whether the receptor is required for parasite motility. The RNAi-suppressed adults and larvae were markedly hypoactive compared to the corresponding controls and they were also resistant to exogenous serotonin treatment. These results show that Sm5HTR is at least one of the receptors responsible for the motor effects of serotonin in S. mansoni. The fact that Sm5HTR is expressed in nerve tissue further suggests that serotonin stimulates movement via this receptor by modulating neuronal output to the musculature. Together, the evidence identifies Sm5HTR as an important neuronal protein and a key component of the motor control apparatus in S. mansoni.

BackgroundZika virus (ZIKV), first isolated in Uganda in 1947, is currently spreading rapidly through South America and the Caribbean. In Brazil, infection has been linked with microcephaly and other serious complications, leading to declaration of a public health emergency of international concern; however, there currently are only limited data on the virus (and its possible sources and manifestations) in the Caribbean.MethodsFrom May, 2014-February, 2015, in conjunction with studies of chikungunya (CHIKV) and dengue (DENV) virus infections, blood samples were collected from children in the Gressier/Leogane region of Haiti who presented to a school clinic with undifferentiated febrile illness. Samples were initially screened by RT-PCR for CHIKV and DENV, with samples negative in these assays further screened by viral culture.FindingsOf 177 samples screened, three were positive for ZIKV, confirmed by viral sequencing; DENV-1 was also identified in culture from one of the three positive case patients. Patients were from two different schools and 3 different towns, with all three cases occurring within a single week, consistent with the occurrence of an outbreak in the region. Phylogenetic analysis of known full genome viral sequences demonstrated a close relationship with ZIKV from Brazil; additional analysis of the NS5 gene, for which more sequences are currently available, showed the Haitian strains clustering within a monophyletic clade distinct from Brazilian, Puerto Rican and Guatemalan sequences, with all part of a larger clade including isolates from Easter Island. Phylogeography also clarified that at least three major African sub-lineages exist, and confirmed that the South American epidemic is most likely to have originated from an initial ZIKV introduction from French Polynesia into Easter Island, and then to the remainder of the Americas.ConclusionsZIKV epidemics in South America, as well as in Africa, show complex dissemination patterns. The virus appears to have been circulating in Haiti prior to the first reported cases in Brazil. Factors contributing to transmission and the possible linkage of this early Haitian outbreak with microcephaly remain to be determined.

Staphylococcus aureus is an important pathogen of humans and animals, and antibiotic resistance is a public health concern. Biofilm formation is essential in virulence and pathogenesis, and the ability to resist antibiotic treatment results in difficult-to-treat and persistent infections. As such, novel antimicrobial approaches are of great interest to the scientific, medical, and agriculture communities. We recently proposed that modulating levels of the cyclic dinucleotide signaling molecule, c-di-GMP (cyclic diguanylate [3,5-cyclic diguanylic acid], cGpGp), has utility in regulating phenotypes of prokaryotes. We report that extracellular c-di-GMP shows activity against human clinical and bovine intramammary mastitis isolates of S. aureus, including methicillinresistant S. aureus (MRSA) isolates. We show that chemically synthesized c-di-GMP is soluble and stable in water and physiological saline and stable following boiling and exposure to acid and alkali. Treatment of S. aureus with extracellular c-di-GMP inhibited cell-to-cell (intercellular) adhesive interactions in liquid medium and reduced (>50%) biofilm formation in human and bovine isolates compared to untreated controls. c-di-GMP inhibited the adherence of S. aureus to human epithelial HeLa cells. The cyclic nucleotide analogs cyclic GMP and cyclic AMP had a lesser inhibitory effect on biofilms, while 5-GMP had no major effect. We propose that cyclic dinucleotides such as c-di-GMP, used either alone or in combination with other antimicrobial agents, represent a novel and attractive approach in the development of intervention strategies for the prevention of biofilms and the control and treatment of infection.

Vibrio cholerae can shift to a "rugose" phenotype, thereby producing copious exopolysaccharide (EPS), which promotes its environmental survival and persistence. We report conditions that promote high-frequency rugose EPS production (HFRP), whereby cells switch at high frequency (up to 80%) to rugose EPS production. HFRP appeared to be more common in clinical strains, as HFRP was found in 6 of 19 clinical strains (32%) (including classical, El Tor, and non-O1 strains) but in only 1 of 16 environmental strains (6%). Differences were found between strains in rugose colony morphology, conditions promoting HFRP, the frequency of rugose-to-smooth (R-S) cell reversion, and biofilm formation. We propose that rugose EPS and HFRP provide an evolutionary and adaptive advantage to specific epidemic V. cholerae strains for increased persistence in the environment.Cholera, caused by Vibrio cholerae, is a severe, life-threatening diarrheal disease which continues to be a scourge throughout much of the world; there have been seven global pandemics recorded since 1817 (15). The explosive epidemic nature and severity of the disease have prompted its listing as a high-priority organism in biodefense research. Epidemic V. cholerae strains can persist for many years in the marine environment while regularly causing significant cholera epidemics (3,5,6,9,16,20,21); however, the specific mechanism underlying the adaptation to long-term persistence, particularly that of epidemic strains, has remained a mystery. Several studies have proposed that the persistence of V. cholerae in the environment is due to a viable but nonculturable state (VBNC) in response to starvation and cold (4,18,19,27); however, it is not known whether the VBNC phenotype promotes persistence in regions where cholera is endemic and under conditions other than starvation and cold. Alternatively, "rugose" exopolysaccharide (rEPS) production might promote the survival and persistence of V. cholerae in the aquatic environment.A rugose colony phenotype was first reported and described in both sixth (classical biotype) and seventh (El Tor biotype) pandemic strains in the late 1930s by Bruce White (25,26) and is characterized by wrinkled colonies expressing copious amounts of EPS. Since then, studies have shown that smooth V. cholerae cells under nutrient-limiting conditions can spontaneously shift at a low frequency to express rEPS and exhibit wrinkled (rugose) colonies (13,14,22,25,26,29) that are virulent in rabbit ileal loop models and in human volunteers (14,17). Although a gene cluster (vps) for the biosynthesis of rEPS and a gene (vpsR) that regulates the expression of several vps biosynthetic genes have been identified (2, 28, 29), the physiology, genetics, and importance of rEPS expression are not well understood and studies on the rugose phenotype have been hampered by the low frequency of switching to the rugose phenotype when available conditions are used. Previously, Morris et al. (14) reported the isolation of only spontaneous rugose variants from a variety ...

Altered El Tor Vibrio cholerae O1, with classical cholera toxin B gene, was isolated from 16 patients with severe diarrhea at St. Mark’s Hospital, Arbonite, Haiti, <3 weeks after onset of the current cholera epidemic. Variable-number tandem-repeat typing of 187 isolates showed minimal diversity, consistent with a point source for the epidemic.