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Jeffrey N. Weiser - One of the best experts on this subject based on the ideXlab platform.

  • host to host transmission of streptococcus pneumoniae is driven by its inflammatory toxin pneumolysin
    Cell Host & Microbe, 2017
    Co-Authors: Ammar M Zafar, Yang Wang, Shigeto Hamaguchi, Jeffrey N. Weiser
    Abstract:

    Host-to-host transmission is a critical step for infection. Here we studied transmission of the opportunistic pathogen Streptococcus pneumoniae in an infant mouse model. Transmission from nasally colonized pups required high levels of Bacterial Shedding in nasal secretions and was temporally correlated with, and dependent upon, the acute inflammatory response. Pneumolysin, a pore-forming cytotoxin and major virulence determinant, was both necessary and sufficient to promote inflammation, which increased Shedding and allowed for intralitter transmission. Direct contact between pups was not required for transmission indicating the importance of an environmental reservoir. An additional in vivo effect of pneumolysin was to enhance Bacterial survival outside of the host. Our findings provide experimental evidence of a microbial strategy for transit to new hosts and explain why an organism expresses a toxin that damages the host upon which it depends.

  • Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection.
    Infection and immunity, 2016
    Co-Authors: M. Ammar Zafar, Yang Wang, Masamitsu Kono, Tonia Zangari, Jeffrey N. Weiser
    Abstract:

    One of the least understood aspects of the bacterium Streptococcus pneumoniae (pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal Shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, Shedding, and transmission during Bacterial monoinfection. Using this model, we demonstrated that the level of Bacterial Shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal Shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized "index" pups to uncolonized "contact" pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of Shedding. This model can be used to examine Bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.

  • TLR2 signaling decreases transmission of Streptococcus pneumoniae by limiting Bacterial Shedding in an infant mouse Influenza A co-infection model.
    PLoS pathogens, 2014
    Co-Authors: Aimee L. Richard, Steven J. Siegel, Jan Erikson, Jeffrey N. Weiser
    Abstract:

    While the importance of transmission of pathogens is widely accepted, there is currently little mechanistic understanding of this process. Nasal carriage of Streptococcus pneumoniae (the pneumococcus) is common in humans, especially in early childhood, and is a prerequisite for the development of disease and transmission among hosts. In this study, we adapted an infant mouse model to elucidate host determinants of transmission of S. pneumoniae from inoculated index mice to uninfected contact mice. In the context of co-infection with influenza A virus, the pneumococcus was transmitted among wildtype littermates, with approximately half of the contact mice acquiring colonization. Mice deficient for TLR2 were colonized to a similar density but transmitted S. pneumoniae more efficiently (100% transmission) than wildtype animals and showed decreased expression of interferon α and higher viral titers. The greater viral burden in tlr2−/− mice correlated with heightened inflammation, and was responsible for an increase in Bacterial Shedding from the mouse nose. The role of TLR2 signaling was confirmed by intranasal treatment of wildtype mice with the agonist Pam3Cys, which decreased inflammation and reduced Bacterial Shedding and transmission. Taken together, these results suggest that the innate immune response to influenza virus promotes Bacterial Shedding, allowing the bacteria to transit from host to host. These findings provide insight into the role of host factors in the increased pneumococcal carriage rates seen during flu season and contribute to our overall understanding of pathogen transmission.

Yang Wang - One of the best experts on this subject based on the ideXlab platform.

  • host to host transmission of streptococcus pneumoniae is driven by its inflammatory toxin pneumolysin
    Cell Host & Microbe, 2017
    Co-Authors: Ammar M Zafar, Yang Wang, Shigeto Hamaguchi, Jeffrey N. Weiser
    Abstract:

    Host-to-host transmission is a critical step for infection. Here we studied transmission of the opportunistic pathogen Streptococcus pneumoniae in an infant mouse model. Transmission from nasally colonized pups required high levels of Bacterial Shedding in nasal secretions and was temporally correlated with, and dependent upon, the acute inflammatory response. Pneumolysin, a pore-forming cytotoxin and major virulence determinant, was both necessary and sufficient to promote inflammation, which increased Shedding and allowed for intralitter transmission. Direct contact between pups was not required for transmission indicating the importance of an environmental reservoir. An additional in vivo effect of pneumolysin was to enhance Bacterial survival outside of the host. Our findings provide experimental evidence of a microbial strategy for transit to new hosts and explain why an organism expresses a toxin that damages the host upon which it depends.

  • Infant Mouse Model for the Study of Shedding and Transmission during Streptococcus pneumoniae Monoinfection.
    Infection and immunity, 2016
    Co-Authors: M. Ammar Zafar, Yang Wang, Masamitsu Kono, Tonia Zangari, Jeffrey N. Weiser
    Abstract:

    One of the least understood aspects of the bacterium Streptococcus pneumoniae (pneumococcus) is its transmission from host to host, the critical first step in both the carrier state and the disease state. To date, transmission models have depended on influenza A virus coinfection, which greatly enhances pneumococcal Shedding to levels that allow acquisition by a new host. Here, we describe an infant mouse model that can be utilized to study pneumococcal colonization, Shedding, and transmission during Bacterial monoinfection. Using this model, we demonstrated that the level of Bacterial Shedding is highest in pups infected intranasally at age 4 days and peaks over the first 4 days postchallenge. Shedding results differed among isolates of five different pneumococcal types. Colonization density was found to be a major factor in the level of pneumococcal Shedding and required expression of capsule. Transmission within a litter occurred when there was a high ratio of colonized "index" pups to uncolonized "contact" pups. Transmission was observed for each of the well-colonizing pneumococcal isolates, with the rate of transmission proportional to the level of Shedding. This model can be used to examine Bacterial and host factors that contribute to pneumococcal transmission without the effects of viral coinfection.

T. Olyhoek - One of the best experts on this subject based on the ideXlab platform.

  • Effective treatment with dihydrostreptomycin of naturally infected cows Shedding Leptospira interrogans serovar hardjo subtype hardjobovis.
    American journal of veterinary research, 1994
    Co-Authors: M. J. Gerritsen, M. J. Koopmans, T. C. E. M. Dekker, M.c.m. De Jong, A. Moerman, T. Olyhoek
    Abstract:

    Abstract The efficacy of dihydrostreptomycin in stopping the Shedding of Leptospira hardjo subtype hardjobovis was studied in naturally infected cows. Blood and urine samples were collected from dairy cows kept on a farm where the farmer had contracted L hardjobovis infection. A microscopic agglutination test and an ELISA were used to determine specific antibody responses in serum. Polymerase chain reaction was used to detect Bacterial Shedding in urine. On the first sample collection date, 6 cows were seropositive, and 3 of those shed leptospires in the urine. These 3 cows were treated once with 25 mg of dihydrostreptomycin/kg of body weight. Within 1 week, the 3 cows stopped Shedding leptospires. Six weeks later, 8 more lactating cows were found to be Shedding leptospires. These cows were also treated once with dihydrostreptomycin, and they too stopped Shedding leptospires within 1 week. From then on, the whole herd was examined weekly for a period of 2 months, and all cows Leptospira-positive by polymerase chain reaction were treated once with dihydrostreptomycin. Again, all cows stopped Shedding leptospires in the urine within 1 week after treatment with dihydrostreptomycin. After a single treatment of the whole herd at the same time, new infections were not seen.

  • Sheep as maintenance host for Leptospira interrogans serovar hardjo subtype hardjobovis.
    American journal of veterinary research, 1994
    Co-Authors: M. J. Gerritsen, M. J. Koopmans, Peterse D, T. Olyhoek
    Abstract:

    Transmission of Leptospira interrogans serovar hardjo subtype hardjobovis from naturally infected sheep to uninfected sheep and calves was studied. A microscopic agglutination test and ELISA were used to determine specific antibody responses in serum. Polymerase chain reaction was used to detect Bacterial Shedding in urine. Six sheep were derived from a dairy farm where cows were infected with L hardjobovis. Three of these sheep were seropositive for L hardjobovis, and 1 also shed leptospires in the urine. The other 2 sheep shed leptospires in the urine 7 days after the first observation date. The 6 sheep were placed on an isolated pasture together with a second group of 6 noninfected sheep. During the observation period of 140 days, 1 sheep of the second group became infected with L hardjobovis. On 5 consecutive days, a urine mixture from the 4 infected sheep was sprayed on the heads of 4 noninfected calves. Within 56 days, all calves that had been sprayed with urine shed L hardjobovis in the urine and became seropositive for L hardjobovis.

  • Effect of streptomycin treatment on the Shedding of and the serologic responses to Leptospira interrogans serovar hardjo subtype hardjobovis in experimentally infected cows.
    Veterinary microbiology, 1993
    Co-Authors: M. J. Gerritsen, M. J. Koopmans, T. Olyhoek
    Abstract:

    Shedding patterns of and serologic responses to Leptospira interrogans serovar hardjo subtype hardjobovis (L. hardjobovis) have been studied in experimentally infected cows treated with streptomycin in comparison to experimentally infected cows receiving no such treatment. Fourteen cows were experimentally infected with L. hardjobovis, and blood and urine samples were collected weekly for 24 weeks. The microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA) were used to determine serologic responses. The polymerase chain reaction (PCR) was used to determine Bacterial Shedding in urine. Six weeks after infection six cows were treated with the antibiotic streptomycin (25 mg/kg body weight/day); three cows were treated only once, and the remaining three were treated for five consecutive days. After treatment all six cows had lower serologic responses compared to the untreated cows. The treated cows became also PCR-negative two days after the first treatment, whereas the eight untreated cows remained PCR-positive for at least 70 days. Cows that stopped Shedding did not resume Shedding within the observation period. Since streptomycin treatment reduces the period of Shedding, transmission of leptospira via contaminated urine might be prevented by a single treatment of an infected herd.

William B. Kilgore - One of the best experts on this subject based on the ideXlab platform.

Kapil K. Chousalkar - One of the best experts on this subject based on the ideXlab platform.

  • Shedding of Salmonella Typhimurium in vaccinated and unvaccinated hens during early lay in field conditions: a randomised controlled trial.
    BMC microbiology, 2018
    Co-Authors: Pardeep Sharma, Andrea R. Mcwhorter, Charles G. B. Caraguel, Margaret Sexton, Greg Underwood, Karen M. Holden, Kapil K. Chousalkar
    Abstract:

    Background Salmonella vaccination is one of the control measure that farmers can use to reduce Bacterial Shedding in their flocks. This study aimed to examine the efficacy of the Vaxsafe® ST (Strain STM-1) attenuated live vaccine administered as ocular and oral doses followed by an intramuscular (IM) dose in rearing, in reducing contamination by Salmonellae of both eggs and the environment in the commercial multi-age cage layer sheds. A randomised controlled trial was conducted up to 26 weeks post last vaccine on two different multi-age caged egg farms.

  • Correlating Bacterial Shedding with fecal corticosterone levels and serological responses from layer hens experimentally infected with Salmonella Typhimurium
    Veterinary Research, 2018
    Co-Authors: Pardeep Sharma, Vivek V. Pande, Talia S. Moyle, Andrea R. Mcwhorter, Kapil K. Chousalkar
    Abstract:

    Salmonella Enteriditis and Salmonella Typhimurium are commonly isolated during egg-related outbreaks of salmonellosis and represent a significant international public health issue. In Australia, Salmonella Typhimurium is the most common serovar identified in egg product related foodborne outbreaks. While a number of studies have investigated Salmonella Shedding and host responses to infection, they have been conducted over a short time period. The present study sought to characterise Bacterial Shedding and host responses to infection in hens infected with only Salmonella Typhimurium or co-infected with both Salmonella Typhimurium and Salmonella Mbandaka over a 16 week period. Salmonella Shedding was quantified using the most probable number and qPCR methods and was highly variable over the course of the experiment. On day 1, fecal corticosterone metabolites in birds infected with Salmonella Typhimurium (674.2 ± 109.3 pg/mg) were significantly higher than control (238.0 ± 12.62 pg/mg) or co-infected (175.4 ± 8.58 pg/mg) birds. The onset of lay occurred between weeks 6–8 post-infection (pi) and Fecal corticosterone metabolite (FCM) concentrations increased in both control and co-infected birds. Antibody responses to infection were monitored in both serum and yolk samples. Salmonella Typhimurium specific antibody was lower in co-infected animals than monoinfected animals. Bacterial loads in internal organs were characterised to determine persistence. Spleen, liver and caecal tonsils were positive for bacteria in both groups, indicating that Salmonella was not cleared from the birds and internal organ colonization could serve as a reservoir for continued Bacterial Shedding.

  • Bacterial contamination of eggs and behaviour of poultry flocks in the free range environment.
    Comparative immunology microbiology and infectious diseases, 2016
    Co-Authors: Talia S. Moyle, Kapil K. Chousalkar, Kelly Drake, Vaibhav C. Gole, Susan J. Hazel
    Abstract:

    The free range production system is becoming more common in Australia and is expected to increase. Free range hens are exposed to more stressors in comparison to hens from barn and cage systems and it is suggested that stress can increase Bacterial Shedding on eggs. The aims of this study were to examine the level of total bacteria and Enterobacteriaceae populations, as well as the presence of Salmonella and Campylobacter, in eggs collected from two free range flocks on two different farms and to conduct longitudinal observations of the behaviour and welfare of hens in the free range production system. Hen age (weeks) was shown to have a significant effect (increase) on the level of total bacteria on the egg shell surface and in shell pores, as well as having an effect on feather condition score. As the hens aged, the frequency of external visual egg characteristics increased, as did feather condition score (where feather condition was poorer). These observations indicate areas which should be investigated further to improve the food safety of eggs and optimise the welfare of free range hens.