Microbiome characterization of defensive tissues in the model anemone Exaiptasia diaphana.

BACKGROUND: Coral reefs are among the most diverse and productive ecosystems on Earth. This success relies on the coral's association with a wide range of microorganisms, including dinoflagellates of the family Symbiodiniaceae that provide coral hosts with most of their organic carbon requirements. While bacterial associates have long been overlooked, research on these microorganisms is gaining traction, and deciphering bacterial identity and function is greatly enhancing our understanding of cnidarian biology. Here, we investigated bacterial communities in defensive tissues (acontia) of the coral model, the sea anemone Exaiptasia diaphana. Acontia are internal filaments that are ejected upon detection of an external threat and release toxins to repel predators. RESULTS: Using culturing techniques and 16S rRNA gene metabarcoding we identified bacterial communities associated with acontia of four Great Barrier Reef-sourced E. diaphana genotypes. We show that bacterial communities are similar across genotypes, and dominated by Alteromonadaceae, Vibrionaceae, Rhodobacteraceae, and Saprospiraceae. By analyzing abundant amplicon sequence variants (ASVs) from metabarcoding data from acontia and comparing these to data from whole anemones, we identified five potentially important bacterial genera of the acontia microbiome: Vibrio, Sulfitobacter, Marivita, Alteromonas, and Lewinella. The role of these bacteria within the acontia remains uninvestigated but could entail assistance in defense processes such as toxin production. CONCLUSIONS: This study provides insight into potential bacterial involvement in cnidarian defense tissues and highlights the need to study bacterial communities in individual compartments within a holobiont.

Sulfur availability for Vibrio fischeri growth during symbiosis establishment depends on biogeography within the squid light organ.

The fitness of host-associated microbes depends on their ability to access nutrients in vivo. Identifying these mechanisms is significant for understanding how microbes have evolved to fill specific ecological niches within a host. Vibrio fischeri is a bioluminescent bacterium that colonizes and proliferates within the light organ of the Hawaiian bobtail squid, which provides an opportunity to study how bacteria grow in vivo. Here, the transcription factor CysB is shown to be necessary for V. fischeri both to grow on several sulfur sources in vitro and to establish symbiosis with juvenile squid. CysB is also found to regulate several genes involved in sulfate assimilation and to contribute to the growth of V. fischeri on cystine, which is the oxidized form of cysteine. A mutant that grows on cystine but not sulfate could establish symbiosis, suggesting that V. fischeri acquires nutrients related to this compound within the host. Finally, CysB-regulated genes are shown to be differentially expressed among the V. fischeri populations occupying the various colonization sites found within the light organ. Together, these results suggest the biogeography of V. fischeri populations within the squid light organ impacts the physiology of this symbiotic bacterium in vivo through CysB-dependent gene regulation.

Experimental infection in mice with Erwinia persicina.

Erwinia persicinus (E. persicina) is a plant pathogenic bacterial species that was previously isolated from a case of human infection. This study aimed to create an experimental infection protocol for E. persicina in laboratory mice. Seventy-two adult mice were divided into four groups (18 animal/group): the control group (G1), the group infected with E. persicina (G2), the group immune-suppressed with cyclophosphamide (G3) and the group immune-suppressed with cyclophosphamide and infected with E. persicina (G4). G2 and G4 were injected with 200 µL of (1 × 1013 cfu/ml) concentration intraperitoneally. Clinical signs, such as diarrhoea, apathy and mortality were observed only in G2 and G4 animals. E. persicina was not detected in blood. Necropsies of the G2 and G4 animals showed lesions in the intestine, liver, kidney and lung tissue. These lesions were characterized by infiltration of inflammatory cells, hyperaemia and focal areas of tissue necrosis in the liver. The results of the pro-inflammatory cytokines analysis revealed a significant increase in the levels of TNF-α and IL1-ß in the liver tissue of the G4 group. E. persicina is an emerging bacterium that can cause pathological lesions into mammalian tissue, which warrants further investigation.

Modelling the immunopathophysiology of Brucella melitensis and its lipopolysaccharide in mice infected via oral route of exposure.

Brucella melitensis is one of the leading zoonotic pathogens with significant economic implications in animal industry worldwide. Lipopolysaccharide, however, remains by far the major virulence with substantial role in diseases pathogenesis. Nonetheless, the effect of B. melitensis and its lipopolysaccharide on immunopathophysiological aspects largely remains an enigma. This study examines the effect of B.melitensis and its lipopolysaccharide on immunopathophysiological parameters following experimental infection using mouse model. Eighty four (n = 84) mice, BALB/c, both sexes with equal gender distribution and 6-8 weeks-old were randomly assigned into three groups. Group 1-2 (n = 72) were orally inoculated with 0.4 mL containing 109 CFU/mL of B. melitensis and its LPS, respectively. Group 3 (n = 12) was challenged orally with phosphate buffered saline and served as a control group. Animals were observed for clinical signs, haematological and histopathological analysis for a period of 24 days post-infection. We hereby report that B.melitensis infected group demonstrated significant clinical signs and histopathological changes than LPS infected group. However, both infected groups showed elevated levels of interleukins (IL-1ß and IL-6) and antibody levels (IgM and IgG) with varying degrees of predominance in LPS infected group than B. melitensis infected group. For hormone analysis, low levels of progesterone, estradiol and testosterone were observed in both B. melitensis and LPS groups throughout the study period. Moreover, in B. melitensis infected group, the organism was re-isolated from the organs and tissues of gastrointestinal, respiratory and reproductive systems thereby confirming the infection and transmission dynamics. This report is the first detailed investigation comparing the infection progression and host responses in relation to the immunopathophysiological aspects in a mouse model after oral inoculation with B. melitensis and its lipopolysaccharide.

Determination of lethal dose of Aeromonas hydrophila Ah17 strain in snake head fish Channa striata.

Aeromonas hydrophila is a major bacterial fish pathogen which causes economic losses in the aquaculture. The study determined the Letha Dose (LD50-96h) of A. hydrophila Ah17 strain (isolated from EUS infected Channa striata) in C. striata. C. striata were challenged with three different concentration of A. hydrophila Ah17 strain 1.0 × 107, 1.0 × 108, 1.0 × 109 CFU/mL. The LD50-96h values were found to be 4.1 × 108 CFU/mL. Percentage of mortality was observed as 10%, 40% and 70% in 1.0 × 107, 1.0 × 108 and 1.0 × 109 CFU/mL respectively in challenged fish. Microbial load was calculated on muscle, kidney, liver and spleen with highest load was observed in muscle and lowest in kidney. Level of liver enzymes such as Aspartate aminotransferase (AST), Alanine Aminotransferase (ALT), and Alkaline Phosphatase (ALP) were increased compared to control fish. Level of mRNA expression of antioxidant genes such as Catalase (cat), Manganese Superoxide Dismutase (MnSOD), Glutathione Peroxidase (GPx) were high in liver tissue of all treated groups than control. Clinical signs were observed after intraperitoneal treatment of Ah17 in C. striata. Clinical signs such as lesions on the site of injection, imbalanced state, changes in the movement of pectoral fins, depigmentation on the tail of caudal fin and irregular lesions on the muscle region were observed. Thus the study concluded that, the LD50-96h value of A. hydrophila Ah17 strain was 4.1 × 108 CFU/mL and exhibited potential pathogenic effect upon experimental infection in snakehead murrel C. striata.

Recombinant Staphylococcal Antigen-F (r-ScaF), a novel vaccine candidate against methicillin resistant Staphylococcus aureus infection: Potency and efficacy studies.

Staphylococcus aureus is a human commensal and pathogen, its clinical importance is exacerbated by the spread of multi-drug resistant strains. The potential future failure of antibiotic therapy necessitates the development of novel control regimes, including new immunotherapeutic approaches. S. aureus has a large repertoire of surface components with potential for immunological targeting. The aim of this study was to evaluate the efficacy of a novel member of staphylococcal conserved antigen family (ScaF) as a factor to elicit cellular and humoral immunity. To determine the ScaF potential as a vaccine candidate, experimental groups of mice were immunized with recombinant Scaf (r-ScaF) formulated in Freund's and alum adjuvants or PBS and subsequently challenged in the sepsis model of S. aureus disease. The vaccine formulations induced robust cellular cytokines responses, including IFN-γ and IL-17, as well as increased production of IgG2a rather than other subclass of IgGs. Active immunization with r-ScaF with adjuvants led to decreased mortality of infected mice and a lower associated bacterial burden in the internal organs in comparison to the control group. Taken together, our Results indicate to the possibility of the r-ScaF protein to be considered as an important component of a multivalent prophylactic vaccine candidate.

The role of the wzy gene in lipopolysaccharide biosynthesis and pathogenesis of avian pathogenic Escherichia coli.

Avian pathogenic Escherichia coli (APEC) causes severe respiratory and systemic diseases in poultry. The wzy gene encodes the O-antigen polymerase (Wzy), which plays an important role in the synthesis of the lipopolysaccharide (LPS) of bacteria. However, the function of the wzy gene in APEC remains unclear. Hence, in this study, a strain harboring a wzy gene mutant (DE17Δwzy) was constructed and the characteristics of this strain were analyzed. The results showed that mutant of wzy changed the phenotype of the LPS and affected serum agglutination of the O-antigen. Decreased motility and biofilm formation was also observed, but the endotoxin titer of the LPS in APEC was not affected. In addition, the wzy mutation significantly decreased the adherence and invasion to DF-1 cells, especially the survival abilities in duck serum and complement. Furthermore, an LD50 assay revealed that the virulence of mutant strain DE17Δwzy was attenuated 132-fold compared with wild-type strain DE17. Moreover, the bacterial load in the blood, liver, spleen, and kidneys of ducks infected with DE17Δwzy was decreased significantly compared with wild-type strain DE17 (p < 0.0001). These results confirmed that the wzy gene is associated with LPS biosynthesis and bacterial pathogenicity in APEC.

Kocuria tytonis sp. nov., isolated from the uropygial gland of an American barn owl (Tyto furcata).

Avian uropygial glands have received increasing attention in recent years, but little is known about micro-organisms in uropygial glands. In this study, we isolated a strain of Gram-stain-positive, non-motile, non-spore-forming cocci, designated 442T, from the uropygial gland of an American barn owl (Tyto furcata) and characterized it using a polyphasic approach. 16S rRNA gene sequence analysis placed the isolate in the genus Kocuria. The G+C content was 70.8 mol%, the major menaquinone was MK-7(H2) and the predominant cellular fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C15 : 0. Phylogenetic analyses based on the 16S rRNA gene identified Kocuria rhizophila DSM 11926T (99.6 % similarity), Kocuria salsicia DSM 24776T (98.7 %), Kocuria varians DSM 20033T (98.3 %) and Kocuria marina DSM 16420T (98.3 %) as the most closely related species. However, average nucleotide identity values below 86 % indicated that the isolate differed from all species hitherto described. Chemotaxonomic analyses and whole-cell protein profiles corroborated these findings. Accordingly, the isolate is considered to be a member of a novel species, for which the name Kocuria tytonis sp. nov. is proposed. The type strain is 442T (=DSM 104130T=LMG 29944T).

The importance of Toll-like receptor 4 during experimental Sporothrix brasiliensis infection.

Here we investigated the importance of Toll-like receptor 4 (TLR-4) in innate immune response to Sporothrix brasiliensis, a virulent fungus of Sporothrix spp. In vitro assays, using C57Bl/6 (wild type [WT]) bone marrow-derived macrophages (BMDMs), and TLR-4 knockout (TLR-4-/-) showed that the absence of TLR-4 resulted in impaired phagocytosis and lower levels of tumor necrosis factor α (TNF-α), interleukin (IL)-6, and nitric oxide. In vivo assays were also performed, and the mice (WT and TLR-4-/-) were intraperitoneally infected with S. brasiliensis yeast ATCC MyA-4831 and euthanized on days 7, 14, and 28 postinfection, with the following parameters evaluated: fungal burden in liver, spleen, kidney, and brain, and the production of cytokines interferon γ (IFN-γ), TNF-α, IL-2, IL-4, IL-6, and IL-10. The results demonstrate the macrophages dependency on TLR-4 for inflammatory activation and in the absence of TLR-4 during experimental S. brasiliensis infection enhanced dissemination occurred after 14 and 28 days. These data show that TLR-4 signals are important for the recognition of S. brasiliensis by macrophages, and their absence promotes the persistence of the infection.

Assessment of the anti-biofilm effect of micafungin in an animal model of catheter-related candidemia.

In cases where catheter-related candidemia (CRC) must be managed without catheter withdrawal, antifungal lock therapy using highly active anti-biofilm (HAAB) agents is combined with systemic treatment. However, the activity of HAAB agents has never been studied in in vivo models using bioluminescence. We assessed the efficacy of micafungin using a bioluminescent Candida albicans SKCA23-ACTgLuc strain in an animal model of CRC. We divided 33 female Wistar rats into five groups: sham (A), infected nontreated (B), treated with lock therapy (0.16 mg/ml) (C), systemically treated only (1 mg/kg) (D), and systemically treated+lock (E). Catheters were colonized 24 h before insertion into the femoral vein (day 0). Treatment started on day 1 and lasted 7 days, followed by 7 days of surveillance. Bioluminescence assays were carried out on days 1, 3, 5, and 14, together with daily monitoring of clinical variables. Postmortem microbiological cultures from the catheter and several tissue samples were also obtained. Overall, 28 rats (84.8%) completed the study. Group B animals showed significant weight loss at days 2, 4, and 5 compared with groups C and D (P < .05). In group B, no animals survived after day 7, 75% had CRC, and bioluminescence remained constant 5 days after catheter implantation. Positive catheter culture rates in groups C, D, and E were, respectively, 83.3%, 62.5%, and 25.0% (P = .15). Micafungin proved to be a HAAB agent when administered both systemically and in lock therapy in an animal model of CRC, although the bioluminescence signal persists after treatment. This persistence should be further analyzed.

In Vivo Virulence Characterization of Pregnancy-Associated Listeria monocytogenes Infections.

Listeria monocytogenes is a foodborne pathogen that infects the placenta and can cause pregnancy complications. Listeriosis usually occurs as a sporadic infection, but large outbreaks are also reported. Virulence from clinical isolates is rarely analyzed due to the large number of animals required, but this knowledge could help guide the response to an outbreak. We implemented a DNA barcode system using signature tags that allowed us to efficiently assay variations in virulence across a large number of isolates. We tested 77 signature-tagged clones of clinical L. monocytogenes strains from 72 infected human placentas and 5 immunocompromised patients, all of which were isolated since 2000. These strains were tested for virulence in a modified competition assay in comparison to that of the laboratory strain 10403S. We used two in vivo models of listeriosis: the nonpregnant mouse and the pregnant guinea pig. Strains that were frequently found at a high abundance within infected organs were considered hypervirulent, while strains frequently found at a low abundance were considered hypovirulent. Virulence split relatively evenly among hypovirulent strains, hypervirulent strains, and strains as virulent as 10403S. The laboratory strain was found to have an intermediate virulence phenotype, supporting its suitability for use in pathogenesis studies. Further, we found that splenic virulence and placental virulence are closely linked in both the guinea pig and mouse models. This suggests that outbreak and sporadic pregnancy-associated L. monocytogenes strains are not generally more virulent than lab reference strains. However, some strains did show consistent and reproducible virulence differences, suggesting that their further study may reveal deeper insights into the biological underpinnings of listeriosis.

Activity of colistin alone or in combination with rifampicin or meropenem in a carbapenem-resistant bioluminescent Pseudomonas aeruginosa intraperitoneal murine infection model.

Background: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections represent a major therapeutic problem and combination therapy may be the chemotherapeutic option. Methods: Bioluminescent CRPA was developed through sequential subcultures in subinhibitory concentrations of meropenem from an engineered strain of bioluminescent PA Xen5. Then CRPA was injected intraperitoneally to establish an intraperitoneal murine infection model. Treatments of colistin alone or combined with rifampicin or meropenem were started 1 h after infection. In vivo bioluminescence imaging was applied dynamically at 0 h, and 2 and 5 h after treatment. Ex vivo bacterial counts from liver, kidney, spleen, lung and blood samples were also determined 5 h after treatment. Results: In vivo imaging showed that both low- and high-dose colistin combined with rifampicin resulted in a significant decrease in bioluminescence signals compared with monotherapy of colistin or rifampicin alone, whereas colistin and meropenem combination therapy did not show a greater bactericidal effect compared with monotherapy. Ex vivo bacterial count results also confirmed that combination of both low- and high-dose colistin with rifampicin resulted in significantly reduced colony counts from five kinds of tissue samples. However, only combination of high-dose colistin + meropenem resulted in reduced colony counts merely in lung and blood samples. Conclusions: Compared with single drugs, colistin and rifampicin combination therapy could exert synergistic effects, which might provide a better alternative when treating CRPA infections in clinical practice. Combination of colistin and meropenem should be considered with caution because it barely shows any synergism in the present in vivo model.

Estimating bacteria diversity in different organs of nine species of mosquito by next generation sequencing.

BACKGROUND: Symbiosis in insects is accumulating significant amount of studies: the description of a wide array of mutualistic associations across the evolutionary history of insects suggests that resident microbiota acts as a driving force by affecting several aspects of hosts biology. Among arthropods, mosquito midgut microbiota has been largely investigated, providing crucial insights on the role and implications of host-symbiont relationships. However, limited amount of studies addressed their efforts on the investigation of microbiota colonizing salivary glands and reproductive tracts, crucial organs for pathogen invasion and vertical transmission of symbiotic microorganisms. Using 16S rRNA gene sequencing-based approach, we analysed the microbiota of gut, salivary glands and reproductive tracts of several mosquito species, representing some of the main vectors of diseases, aiming at describing the dynamics of bacterial communities within the individual. RESULTS: We identified a shared core microbiota between different mosquito species, although interesting inter- and intra-species differences were detected. Additionally, our results showed deep divergences between genera, underlining microbiota specificity and adaptation to their host. CONCLUSIONS: The comprehensive landscape of the bacterial microbiota components may ultimately provide crucial insights and novel targets for possible application of symbionts in innovative strategies for the control of vector borne diseases, globally named Symbiotic Control (SC), and suggesting that the holobiont of different mosquito species may significantly vary. Moreover, mosquito species are characterized by distinctive microbiota in different organs, likely reflecting different functions and/or adaptation processes.

Comparative experimental study of Brucella melitensis and its lipopolysaccharide in mouse model infected via subcutaneous route of exposure.

Brucella melitensis is a major zoonotic pathogen in which lipopolysaccharide (LPS) is believed to play a major role in the diseases pathogenesis. To study the immunopathophysiological aspects, we established a mouse model experimentally infected with whole cell of B. melitensis and its lipopolysaccharide via subcutaneous route of exposure. Eighty four mice, BALB/c, both sexes with equal gender distribution and 6-8 weeks-old were randomly assigned into 3 groups. Group 1 (n = 36) were subcutaneoulsy inoculated with 0.4 mL 109 of B. melitensis while group 2 (n = 36) were subcutaneously challenged with 0.4 mL 109 of LPS. Group 3 (n = 12) was challenged subcuatneously with phosphate buffered saline and served as a control group. Animals were observed for clinical signs, haematological and histopathological analysis for a period of 24 days post-inoculation. Our results revealed that B. melitensis infected group demonstrated significant clinical signs and histopathological evidence than LPS infected group. However, both infected groups showed elevated levels of interleukins (IL-1ß & IL6), antibody levels (IgM & IgG) as early as 3 days post-infection with predominance in LPS infected group. For hormone analysis, low levels of progesterone, estradiol and testosterone were observed in both B. melitensis and LPS challenged groups throughout the study period. Moreover, in B. melitensis infected groups, the organism was re-isolated from the organs and tissues of gastrointestinal, respiratory and reproductive systems; thereby confirming the possible transmission of the disease dynamics. Moreover, LPS stimulated significantly the innate and acquired immune system without significant systemic dysfunction suggesting the potentiality of the protective properties of this component as an alternative vaccine for brucellosis infection. This report is the first detailed investigation comparing the infection progression and host responses in relation to the immunopathophysiological aspects in mouse model after subcutaneous inoculation with B. melitensis and its lipopolysaccharide.

Distribution of Salmonella Enteritidis in internal organs and variation of cecum microbiota in chicken after oral challenge.

The aim study was to explore the distribution of Salmonella Enteritidis (S. enteritidis) in internal organs and variation of cecum microbiota in newly hatched chicken after oral challenge during a 21-day period. The quantities of S. enteritidis DNA in different internal organs (heart, liver, spleen, stomach, pancreas, small intestine, blood and cecum contents) were determined by real-time fluorescent quantitative polymerase chain reaction (FQ-PCR). The result showed that all of the above-mentioned samples were positive at 12 h post inoculation (PI) after oral challenge. The highest copy numbers of S. enteritidis in all tissue were heart and liver, with about 2 × 102 to 6 × 106 copies of DNA target sequences/0.5 g. The copy number of S. enteritidis in the stomach was only lower than the heart and liver. The blood at 8 d PI, the pancreas at 10 d PI, the heart at 14 d PI and the stomach at 17 d PI didn't have a positive result. However, the liver, spleen, cecum contents and small intestine were all positive during the 21-day period. The cecum contents at 0 d PI, 4 d PI and 10 d PI from the control group and experiment group were collected for bacterial 16 S rRNA sequencing targeting the V3-V4 hypervariable region. The result showed that at the 0 d PI, the main cecum microbiota ingredient of the two-day old chicken was Enterobacteriaceae (Proteobacteria) and the other microbiology species were fewer. At the 10 d PI, the microbiota ingredient of cecum became abundant and stable mainly including the families Ruminococcaceae (Firmicutes), Enterobacteriaceae (Proteobacteria), Lachnospiraceae (Firmicutes) and clostridiacaea (Firmicutes) both of the two group, suggesting Salmonella infection with 2-day old chicken might not significantly change cecum microbiota community. The study indicated the major organs, which carried numerous S. enteritidis, providing a significantly guideline for salmonella detection in poultry and revealed the main microbiota ingredient of chicken cecum.

Increased Resistance to Intradermal Francisella tularensis LVS Infection by Inactivation of the Sts Phosphatases.

The Suppressor of TCR signaling proteins (Sts-1 and Sts-2) are two homologous phosphatases that negatively regulate signaling pathways in a number of hematopoietic lineages, including T lymphocytes. Mice lacking Sts expression are characterized by enhanced T cell responses. Additionally, a recent study demonstrated that Sts-/- mice are profoundly resistant to systemic infection by Candida albicans, with resistance characterized by enhanced survival, more rapid fungal clearance in key peripheral organs, and an altered inflammatory response. To investigate the role of Sts in the primary host response to infection by a bacterial pathogen, we evaluated the response of Sts-/- mice to infection by a Gram-negative bacterial pathogen. Francisella tularensis is a facultative bacterial pathogen that replicates intracellularly within a variety of cell types and is the causative agent of tularemia. Francisella infections are characterized by a delayed immune response, followed by an intense inflammatory reaction that causes widespread tissue damage and septic shock. Herein, we demonstrate that mice lacking Sts expression are significantly resistant to infection by the live vaccine strain (LVS) of F. tularensis Resistance is characterized by reduced lethality following high-dose intradermal infection, an altered cytokine response in the spleen, and enhanced bacterial clearance in multiple peripheral organs. Sts-/- bone marrow-derived monocytes and neutrophils, infected with F. tularensis LVS ex vivo, display enhanced restriction of intracellular bacteria. These observations suggest the Sts proteins play an important regulatory role in the host response to bacterial infection, and they underscore a role for Sts in regulating functionally relevant immune response pathways.

Within-host spatiotemporal dynamics of systemic Salmonella infection during and after antimicrobial treatment.

OBJECTIVES: We determined the interactions between efficacy of antibiotic treatment, pathogen growth rates and between-organ spread during systemic Salmonella infections. METHODS: We infected mice with isogenic molecularly tagged subpopulations of either a fast-growing WT or a slow-growing ΔaroC Salmonella strain. We monitored viable bacterial numbers and fluctuations in the proportions of each bacterial subpopulation in spleen, liver, blood and mesenteric lymph nodes (MLNs) before, during and after the cessation of treatment with ampicillin and ciprofloxacin. RESULTS: Both antimicrobials induced a reduction in viable bacterial numbers in the spleen, liver and blood. This reduction was biphasic in infections with fast-growing bacteria, with a rapid initial reduction followed by a phase of lower effect. Conversely, a slow and gradual reduction of the bacterial load was seen in infections with the slow-growing strain, indicating a positive correlation between bacterial net growth rates and the efficacy of ampicillin and ciprofloxacin. The viable numbers of either bacterial strain remained constant in MLNs throughout the treatment with a relapse of the infection with WT bacteria occurring after cessation of the treatment. The frequency of each tagged bacterial subpopulation was similar in the spleen and liver, but different from that of the MLNs before, during and after treatment. CONCLUSIONS: In Salmonella infections, bacterial growth rates correlate with treatment efficacy. MLNs are a site with a bacterial population structure different to those of the spleen and liver and where the total viable bacterial load remains largely unaffected by antimicrobials, but can resume growth after cessation of treatment.

Isolation and identification of bacterial populations of zoonotic importance from captive non-venomous snakes in Malaysia.

AIM: Captivity of non-venomous snakes such as python and boa are common in zoos, aquariums and as pets in households. Poor captivity conditions expose these reptiles to numerous pathogens which may result in disease conditions. The purpose of this study was to investigate the common bacteria isolated from necropsied captive snakes in Malaysia over a five year period. MATERIALS AND METHODS: A total of 27 snake carcasses presented for necropsy at the Universiti Putra Malaysia (UPM) were used in this survey. Samples were aseptically obtained at necropsy from different organs/tissues (lung, liver, heart, kindey, oesophagus, lymph node, stomach, spinal cord, spleen, intestine) and cultured onto 5% blood and McConkey agar, respectively. Gram staining, morphological evaluation and biochemical test such as oxidase, catalase and coagulase were used to tentatively identify the presumptive bacterial isolates. RESULTS: Pythons had the highest number of cases (81.3%) followed by anaconda (14.8%) and boa (3.7%). Mixed infection accounted for 81.5% in all snakes and was highest in pythons (63%). However, single infection was only observed in pythons (18.5%). A total of 82.7%, 95.4% and 100% of the bacterial isolates from python, anaconda and boa, respectively were gram negative. Aeromonas spp was the most frequently isolated bacteria in pythons and anaconda with incidences of 25 (18%) and 8 (36.6%) with no difference (p > 0.05) in incidence, respectively, while Salmonella spp was the most frequently isolated in boa and significantly higher (p < 0.05) than in python and anaconda. Bacteria species were most frequently isolated from the kidney of pythons 35 (25.2%), intestines of anacondas 11 (50%) and stomach of boa 3 (30%). CONCLUSION: This study showed that captive pythons harbored more bacterial species than anaconda or boa. Most of the bacterial species isolated from these snakes have public health importance and have been incriminated in human infections worldwide.

Vibrio fischeri-derived outer membrane vesicles trigger host development.

Outer membrane vesicles (OMV) are critical elements in many host-cell/microbe interactions. Previous studies of the symbiotic association between Euprymna scolopes and Vibrio fischeri had shown that within 12 h of colonizing crypts deep within the squid's light organ, the symbionts trigger an irreversible programme of tissue development in the host. Here, we report that OMV produced by V. fischeri are powerful contributors to this process. The first detectable host response to the OMV is an increased trafficking of macrophage-like cells called haemocytes into surface epithelial tissues. We showed that exposing the squid to other Vibrio species fails to induce this trafficking; however, addition of a high concentration of their OMV, which can diffuse into the crypts, does. We also provide evidence that tracheal cytotoxin released by the symbionts, which can induce haemocyte trafficking, is not part of the OMV cargo, suggesting two distinct mechanisms to induce the same morphogenesis event. By manipulating the timing and localization of OMV signal delivery, we showed that haemocyte trafficking is fully induced only when V. fischeri, the sole species able to reach and grow in the crypts, succeeds in establishing a sustained colonization. Further, our data suggest that the host's detection of OMV serves as a symbiotic checkpoint prior to inducing irreversible morphogenesis.

Extraintestinal infection of Helicobacter cinaedi induced by oral administration to Balb/c mice.

Although Helicobacter cinaedi was initially considered an opportunistic pathogen in immunocompromised patients, it was later shown to also infect immunocompetent and healthy individuals. Sporadic bacteremia due to H. cinaedi has frequently been reported; however, whether the bacterium can be translocated after passage through the intestinal mucosa remains unclear. In the present study, a preclinical small animal model that faithfully reproduces H. cinaedi infection in humans was developed. Balb/c male mice were orally inoculated with a single dose of 6.8 × 107 CFU of a human clinical H. cinaedi strain. The organism persistently colonized the intestinal tract of the mice, particularly the cecum and colon, for at least 56 days, and the bacteria were excreted in the feces. Although inoculated bacteria were recovered from the spleen, liver, kidney, lung, bladder and mesenteric lymph nodes during the first 2 weeks of bacteremia, the organism was not isolated from these organs after 4 weeks, suggesting that complement- and antibody-mediated serum sensitivity account for the relatively low frequency of systemic infection. However, H. cinaedi was isolated from the biceps femoris, triceps branchii, latissimus dorsi, and trapezius muscles beyond 2 weeks after infection and after production of specific anti-H. cinaedi IgM and IgG antibodies. The present findings suggest that experimental infection of Balb/c mice with H. cinaedi may be a useful model for further studies of H. cinaedi pathogenesis, prophylaxis or therapeutic interventions in vivo.