Organic Turkey Flocks: A Reservoir of Streptococcus gallolyticus subspecies gallolyticus

Geese as reservoirs of human colon cancer-associated Streptococcus gallolyticus

Recently, an increased number of reports have described pathogens of animal origin that cause a variety of infections and a rise in their transmission to humans. Streptococcus gallolyticus, a member of the Streptococcus bovis/Streptococcus equinus complex (SBSEC), is one of these pathogens and infects a wide range of hosts from mammals to poultry and has a broad functionality ranging from pathogenicity to food fermentation. As S. gallolyticus causes complications including bacteremia, infective endocarditis, and colorectal malignancy in humans, it is important to investigate its occurrence in various hosts, including geese, to prevent potential zoonotic transmissions. This study aimed to investigate the presence of S. gallolyticus in the droppings of clinically healthy and diarrheic geese, which were raised intensively and semi-intensively, by the in vitro culture method, characterize the isolates recovered by PCR and sequence-based molecular methods and determine their antibiotic susceptibility by the disk diffusion and gradient test methods. For this purpose, 150 samples of fresh goose droppings were used. Culture positivity for S. gallolyticus was determined as 8% (12/150). PCR analysis identified 54.55% (n = 6) of the isolates as S. gallolyticus subsp. gallolyticus and 45.45% (n = 5) as S. gallolyticus subsp. pasteurianus. Following the 16S rRNA sequence and ERIC-PCR analyses, S. gallolyticus subspecies exhibited identical cluster and band profiles that could be easily distinguished from each other and were clonally identified. High rates of susceptibility to florfenicol, penicillin, rifampicin, and vancomycin were detected among the isolates, regardless of the subspecies diversity. Both subspecies showed high levels of resistance to bacitracin, clindamycin, doxycycline, tetracycline, trimethoprim-sulfamethoxazole, and erythromycin and multiple MDR profiles, indicating their potential to become superbugs. This first report from Türkiye demonstrates the occurrence of the S. gallolyticus subspecies in geese. In view of the recent increase of geese production and the consumption of goose meat in Türkiye, the occurrence of S. gallolyticus in geese should not be ignored to prevent zoonotic transmission.

Isolation, characterization, and experimental infection of Streptococcus gallolyticus subspecies pasteurianus from commercial turkeys with acute septicemia: a pilot study

Streptococcus gallolyticus (SG) is a Gram-positive cocci found as commensal gut flora in animals and humans. SG has emerged as a cause of disease in young poults between 1 and 3 wk of age. SG is associated with septicemia resulting in acute mortality with no premonitory signs in turkeys. Three SG isolates were obtained from clinical field cases of acute septicemia of commercial turkeys and used in three independent experiments. In Experiment 1, embryos were inoculated 25 d of embryogenesis with varying concentrations of SG1, SG2, or SG3. In Experiment 2, day of hatch, poults were inoculated with varying concentrations using different routes of administration of SG1, SG2, or SG3. In Experiment 3, day of hatch, poults were inoculated with only isolate SG1 using different paths. Poults were randomly selected for necropsy on d 8 and d 15 and sampled to collect spleen, heart, and liver for SG on d 21, the remaining poults were necropsied and cultured. Samples were plated on Columbia nalidixic acid and colistin agar (CNA) (40°C, 18-24 h). Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) confirmed suspect colonies. Data were analyzed using the chi-square test of independence, testing all possible combinations to determine significance (P < 0.05). Weight data were subjected to ANOVA using JMP with significance (P < 0.05). No differences were found in BW or BWG on d 0, 8, 15, or 22. Splenomegaly, focal heart necrosis, and pericarditis were observed in all groups in experiments 1 through 3. In Experiment 3, only airsacculitis was observed in a negative control in separate isolation (P > 0.05). On d 21 of Experiment 3, increased (P < 0.05) recovery of SG from spleens were observed in co-housed negative controls, as well as poults challenged by oral gavage (P > 0.05 for d 7 and d 14). These results confirm numerous previous studies indicating that SG subsp. pasteurianus is a primary infectious microorganism that causes septicemia in young poults.

Microbiological Quality and Safety of Fresh Turkey Meat at Retail Level, Including the Presence of ESBL-Producing Enterobacteriaceae and Methicillin-Resistant S. aureus

The aim of this work was to study the microbiological safety and quality of marketed fresh turkey meat, with special emphasis on methicillin-resistant S. aureus, ESBL-producing E. coli, and K. pneumoniae. A total of 51 fresh turkey meat samples were collected at retail level in Spain. Mesophile, Pseudomonas spp., enterococci, Enterobacteriaceae, and staphylococci counts were 5.10 ± 1.36, 3.17 ± 0.87, 2.03 ± 0.58, 3.18 ± 1.00, and 2.52 ± 0.96 log CFU/g, respectively. Neither Campylobacter spp. nor Clostridium perfringens was detected in any sample. ESBL-producing K. pneumoniae and E. coli were detected in 22 (43.14%), and three (5.88%) samples, respectively, all of which were multi-resistant. Resistance to antimicrobials of category A (monobactams, and glycilcyclines) and category B (cephalosporins of third or fourth generation, polymixins, and quinolones), according to the European Medicine Agency classification, was found among the Enterobacteriaceae isolates. S. aureus and methicillin-resistant S. aureus were detected in nine (17.65%) and four samples (7.84%), respectively. Resistance to antimicrobials of category A (mupirocin, linezolid, rifampicin, and vancomycin) and category B (cephalosporins of third- or fourth generation) was found among S. aureus, coagulase-negative staphylococci, and M. caseolyticus isolates.

Outbreaks of Streptococcus gallolyticus subsp. pasteurianus in Goslings Characterized by Central Nervous Symptoms

The present report describes outbreaks of Streptococcus gallolyticus subsp. pasteurianus in young geese flocks in Austria. The flocks, comprising 160-1450 goslings of 2-3 wk of age, experienced increased mortalities The clinical signs were characterized by severe central nervous symptoms, namely leg paddling and torticollis. The postmortem investigation revealed hepatitis, splenitis, and a low amount of liquid fluid in the coelomic cavity. Livers were of fragile texture, with white necrotic areas. The latter were also found in spleens. No macroscopic lesions were seen in brains. Bacteriologic investigation followed by bacterial identification by matrix-assisted laser desorption time-of-flight mass spectrometry and phylogenetic analysis of the partial 16S rRNA region revealed the presence in heart, liver, spleen, and brain of S. gallolyticus subsp. pasteurianus. Histologic investigation revealed multifocal necrosis in liver and spleen samples together with infiltration of mononuclear cells and heterophilic granulocytes. Furthermore, in the lesions, coccoid bacteria could be identified. No histopathologic changes were observed in brain samples from goslings, except in one bird in which accumulation of coccoid bacteria in blood vessels of the brain samples was present. Antibiotic sensitivity tests revealed identical profiles for all strains, which were susceptible to penicillins, cephalosporins, chloramphenicol, imipenem, and tylosin. However, resistance was found against quinolones, aminoglycosides, tetracycline, and trimethoprim-sulfamethoxazole, which are commonly used to treat infections with gram-positive bacteria.

Effect of supplementation of a dairy-originated probiotic bacterium, Propionibacterium freudenreichii subsp. freudenreichii, on the cecal microbiome of turkeys challenged with multidrug-resistant Salmonella Heidelberg

A dairy-originated probiotic bacterium, Propionibacterium freudenreichii subsp. freudenreichii B3523 (PF) was found to be effective in reducing multidrug-resistant Salmonella Heidelberg (MDR SH) colonization in turkey poults (2-week-old) and growing (7-week-old) and finishing (12-week-old) turkeys. In this study, we explored the potential for microbiome modulation in the cecum of turkeys of different age groups due to PF supplementation in conjunction with MDR SH challenge. One-day-old commercial turkey poults were allocated to 3 treatment groups: negative control (N; turkeys without PF supplementation or SH challenge), SH control (S; turkeys challenged with SH without PF supplementation), and test group (P; turkeys supplemented with PF and challenged with SH). Turkeys were supplemented with 10¹⁰ CFU PF in 5-gallon (18.9 L) water until 7 or 12 week of age. At the 6th or 11^th wk, turkeys were challenged with SH at 10⁶ and 10⁸ CFU/bird by crop gavage, respectively. After 2 and 7 d of challenge (2-d postinoculation [PI] and 7-d PI, respectively), cecal samples were collected and microbiome analysis was conducted using Illumina MiSeq. The experiments were repeated twice with 8 and 10 turkeys/group for 7- and 12-wk studies, respectively. Results indicated that the species richness and abundance (Shannon diversity index) was similar among the treatment groups. However, treatments caused apparent clustering of the samples among each other (P < 0.05). Firmicutes was the predominant phylum in the growing and finishing turkey cecum which was evenly distributed among the treatments except on wk 12 where the relative abundance of Firmicutes was significantly higher in P than in N (P = 0.02). The MDR SH challenge resulted in modulation of microflora such as Streptococcus, Gordonibacter, and Turicibacter (P < 0.05) in the S groups compared with the P and N groups, known to be associated with inflammatory responses in birds and mammals. The supplementation of PF increased the relative abundance of carbohydrate-fermenting and short-chain fatty acid–producing genera in the P group compared with the S group (P < 0.05). Moreover, the results revealed that PF supplementation potentially modulated the beneficial microbiota in the P group, which could mitigate SH carriage in turkeys.

Risk factors for the carriage of Streptococcus infantarius subspecies infantarius isolated from African fermented dairy products

Streptococcus infantarius subsp. infantarius (Sii) has been identified as predominant lactic acid bacteria in spontaneously fermented dairy products (FDPs) in sub-Saharan Africa including Côte d'Ivoire. However, Sii belongs to the Streptococcus bovis/Streptococcus equinus complex (SBSEC). Most SBSEC members are assumed to be involved as opportunistic pathogens in serious diseases in both humans and animals. A population-based cross-sectional survey, including 385 participants was conducted in Korhogo, northern Côte d'Ivoire, to identify risk factors for Sii fecal carriage, including consumption of local FDPs. A structured questionnaire was used to gather participant's socio-demographic and economic characteristics, their relation to livestock and dietary habits. In addition, fresh stool and milk samples were collected. The identification of Sii was done using a SBSEC-specific PCR assay targeting 16S rRNA and groEL genes. The overall prevalence of SBSEC and Sii carriage was 23.2% (confidence interval CI 95% = 18.9-27.5) and 12.0% (CI 95% = 8.4-15.5) for stool, respectively. Prevalence of Sii was significantly higher in consumers of artisanal butter compared with non-consumers (57.1% vs 10.1%, odds ratio OR: 11.9, 95% CI: 3.9-36.6), as well as in persons handling livestock (OR = 3.9; 95% CI = 1.6-9.3) and livestock primary products (OR = 5.7; 95% CI = 2.3-14.3). The closer contact with livestock was a risk factor for Sii fecal carriage. Sii strains were isolated from fresh and fermented milk products with a prevalence of 30.4% and 45.4%, respectively. Analysis of Sii population structure through the SBSEC multi locus sequence typing assay revealed a close relationship across human and dairy isolates, possibly linked to a Kenyan human isolate. All these outcomes underline the interest of in-depth investigations on the ecology, potential reservoirs and pathways of contamination by Sii at the human-animal-environment interface in comparison to yet to be collected data from Europe, Asia and the Americas to further elucidate the various roles of Sii.

Correlation between Streptococcus bovis bacteremia and density of cows in Galicia, northwest of Spain

BACKGROUND

There are few data on the epidemiology of infections caused by Streptococcus bovis (Sb). Some studies suggest that both residence in rural areas and contact with livestock could be potential risk factors.

METHODS

We performed a retrospective study for the period 2005-2016 of all cases of bacteremia caused by Sb in Galicia (a region in the northwest of Spain). The association between the incidence rate of Sb bacteremia and the number of cattle by province and district was analyzed.

RESULTS

677 cases were included with a median age of 76 years, 69.3% males. The most frequent infections were endocarditis (234 cases, 34.5%), primary bacteremia (213 cases, 31.5%) and biliary infection (119 cases, 17.5%). In 252 patients, colon neoplasms were detected (37.2%). S. gallolyticus subsp. gallolyticus was the predominant species (52.3%). Mortality was 15.5% (105 cases). The annual incidence rate was 20.2 cases/10⁶ inhabitants and was correlated with the density of cattle (p < 0.001), but not with rurality. When comparing the two provinces with a strong predominance of rural population, but with important differences in the number of cattle, such as Orense and Lugo, with 6% and 47.7% of Galician cattle, respectively, the rates were very different: 15.8 and 43.6 cases/10⁶, respectively, with an RR of 2.7 (95% CI, 2.08-3.71). Some districts of the province of Lugo had rates higher than 100 cases/10⁶ inhabitants.

CONCLUSIONS

Our study shows a significant correlation between the rates of Sb bacteremia and cattle density, suggesting a possible transmission of Sb from cows to people.

Open-access bacterial population genomics: BIGSdb software, the PubMLST.org website and their applications

The PubMLST.org website hosts a collection of open-access, curated databases that integrate population sequence data with provenance and phenotype information for over 100 different microbial species and genera.  Although the PubMLST website was conceived as part of the development of the first multi-locus sequence typing (MLST) scheme in 1998 the software it uses, the Bacterial Isolate Genome Sequence database (BIGSdb, published in 2010), enables PubMLST to include all levels of sequence data, from single gene sequences up to and including complete, finished genomes.  Here we describe developments in the BIGSdb software made from publication to June 2018 and show how the platform realises microbial population genomics for a wide range of applications.  The system is based on the gene-by-gene analysis of microbial genomes, with each deposited sequence annotated and curated to identify the genes present and systematically catalogue their variation.  Originally intended as a means of characterising isolates with typing schemes, the synthesis of sequences and records of genetic variation with provenance and phenotype data permits highly scalable (whole genome sequence data for tens of thousands of isolates) means of addressing a wide range of functional questions, including: the prediction of antimicrobial resistance; likely cross-reactivity with vaccine antigens; and the functional activities of different variants that lead to key phenotypes.  There are no limitations to the number of sequences, genetic loci, allelic variants or schemes (combinations of loci) that can be included, enabling each database to represent an expanding catalogue of the genetic variation of the population in question.  In addition to providing web-accessible analyses and links to third-party analysis and visualisation tools, the BIGSdb software includes a RESTful application programming interface (API) that enables access to all the underlying data for third-party applications and data analysis pipelines.

The Road to Infection: Host-Microbe Interactions Defining the Pathogenicity of Streptococcus bovis/Streptococcus equinus Complex Members

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) comprises several species inhabiting the animal and human gastrointestinal tract (GIT). They match the pathobiont description, are potential zoonotic agents and technological organisms in fermented foods. SBSEC members are associated with multiple diseases in humans and animals including ruminal acidosis, infective endocarditis (IE) and colorectal cancer (CRC). Therefore, this review aims to re-evaluate adhesion and colonization abilities of SBSEC members of animal, human and food origin paired with genomic and functional host-microbe interaction data on their road from colonization to infection. SBSEC seem to be a marginal population during GIT symbiosis that can proliferate as opportunistic pathogens. Risk factors for human colonization are considered living in rural areas and animal-feces contact. Niche adaptation plays a pivotal role where Streptococcus gallolyticus subsp. gallolyticus (SGG) retained the ability to proliferate in various environments. Other SBSEC members have undergone genome reduction and niche-specific gene gain to yield important commensal, pathobiont and technological species. Selective colonization of CRC tissue is suggested for SGG, possibly related to increased adhesion to cancerous cell types featuring enhanced collagen IV accessibility. SGG can colonize, proliferate and may shape the tumor microenvironment to their benefit by tumor promotion upon initial neoplasia development. Bacteria cell surface structures including lipotheichoic acids, capsular polysaccharides and pilus loci (pil1, pil2, and pil3) govern adhesion. Only human blood-derived SGG contain complete pilus loci and other disease-associated surface proteins. Rumen or feces-derived SGG and other SBSEC members lack or harbor mutated pili. Pili also contribute to binding to fibrinogen upon invasion and translocation of cells from the GIT into the blood system, subsequent immune evasion, human contact system activation and collagen-I-binding on damaged heart valves. Only SGG carrying complete pilus loci seem to have highest IE potential in humans with significant links between SGG bacteremia/IE and underlying diseases including CRC. Other SBSEC host-microbe combinations might rely on currently unknown mechanisms. Comparative genome data of blood, commensal and food isolates are limited but required to elucidate the role of pili and other virulence factors, understand pathogenicity mechanisms, host specificity and estimate health risks for animals, humans and food alike.

Case-control study: Determination of potential risk factors for the colonization of healthy volunteers with Streptococcus gallolyticus subsp. gallolyticus

Streptococcus gallolyticus subsp. gallolyticus was identified in humans and animals as commensal of the gut and can act as a causative agent of endocarditis and septicemia. A case-control study was performed to identify yet unknown risk factors for the transmission of this facultative pathogen. The prevalence in the gut of 99 healthy volunteers was determined using real-time polymerase chain reaction resulting in 62.5% S. gallolyticus subsp. gallolyticus positive excrements. Subsequent cultivation offered three isolates and epidemiological analysis based on MLST revealed sequence type (ST) 3 and ST 7, previously detected from bovine and endocarditis patients. These results support the hypotheses of the zoonotic potential of this bacterium. Participant questionnaires were evaluated concerning personal characteristics, nutritional habits and animal contact. Specifically, closer contact between participants and animals influenced the colonization of the human gut significantly and was further affected if volunteers used excrement for the fertilization of plants.