Fulminant neonatal sepsis due to Streptococcus alactolyticus - A case report and review

Case Report: Streptococcus alactolyticus as a Rare Pathogen of Mitral Endocarditis

Streptococcus bovis/Streptococcus equinus complex (SBSEC) is a group of non-enterococcal group D Streptococci that colonizes both humans and animals. Due to gastrointestinal disease, they can switch in opportunistic pathogens passing through intestinal mucosal barrier and may cause bacteremia and distant organs damage. Despite infective endocarditis (IE), extra-cardiac manifestations of organs damage include osteoarticular infections, meningitis, and biliary infections among others; moreover, the association with colonic pathological lesions has been largely described. Streptococcus alactolyticus as a species included in SBSEC may share pathophysiological similarities, although it represents an extremely rare cause of distant organ infections, being reported in literature as causative agent of IE in only two other cases. We describe a case of 69-year-old male admitted to our institution due to mild-moderate dyspnea and fever, affected by cervico-brachialgia for 3 weeks. Streptococcus alactolyticus was identified as causative agent of IE on the mitral valve, causing severe regurgitation.

Pathogenicity and drug resistance of animal streptococci responsible for human infections

Bacteria of the genus Streptococcus, earlier considered typically animal, currently have also been causing infections in humans. It is necessary to make clinicians aware of the emergence of new species that may cause the development of human diseases. There is an increasing frequency of isolation of streptococci such as S. suis, S. dysgalactiae, S. iniae and S. equi from people. Isolation of Streptococcus bovis/Streptococcus equinus complex bacteria has also been reported. The streptococcal species described in this review are gaining new properties and virulence factors by which they can thrive in new environments. It shows the potential of these bacteria to changes in the genome and the settlement of new hosts. Information is presented on clinical cases that concern streptococcus species belonging to the groups Bovis, Pyogenic and Suis. We also present the antibiotic resistance profiles of these bacteria. The emerging resistance to β-lactams has been reported. In this review, the classification, clinical characteristics and antibiotic resistance of groups and species of streptococci considered as animal pathogens are summarized.

Comparative assessment of faecal microbial composition and metabonome of swine, farmers and human control

The gastrointestinal tract of humans and swine consist of a wide range of bacteria which interact with hosts metabolism. Due to the differences in co-evolution and co-adaptation, a large fraction of the gut microbiome is host-specific. In this study, we evaluated the effect of close human-animal interaction to the faecal metagenome and metabonome of swine, farmer and human control. Three distinct clusters were observed based on T-RFLP-derived faecal microbial composition. However, 16S-inferred faecal microbiota and metabolic profiles showed that only human control was significantly different from the swine (P < 0.05). The metabonome of farmers and human controls were highly similar. Notably, higher trimethylamine N-oxide (TMAO) and butyrate were detected in human control and swine, respectively. The relative abundance of TMAO was positively correlated with Prevotella copri. Overall, we compared and established the relationship between the metabolites and microbiota composition of swine, farmers and human control. Based on the data obtained, we deduced that long term occupational exposure to swine and farm environment had affected the gut bacterial composition of farmers. Nonetheless, the effect was less prominent in the metabolite profiles, suggesting the gut bacteria expressed high functional plasticity and are therefore resilience to the level of community shift detected.

Antimicrobial Resistance in Streptococcus spp

The genus Streptococcus includes Gram-positive organisms shaped in cocci and organized in chains. They are commensals, pathogens, and opportunistic pathogens for humans and animals. Most Streptococcus species of veterinary relevance have a specific ecological niche, such as S. uberis, which is almost exclusively an environmental pathogen causing bovine mastitis. In contrast, S. suis can be considered as a true zoonotic pathogen, causing specific diseases in humans after contact with infected animals or derived food products. Finally, Streptococcus species such as S. agalactiae can be sporadically zoonotic, even though they are pathogens of both humans and animals independently. For clarification, a short taxonomical overview will be given here to highlight the diversity of streptococci that infect animals. Several families of antibiotics are used to treat animals for streptococcal infections. First-line treatments are penicillins (alone or in combination with aminoglycosides), macrolides and lincosamides, fluoroquinolones, and tetracyclines. Because of the selecting role of antibiotics, resistance phenotypes have been reported in streptococci isolated from animals worldwide. Globally, the dynamic of resistance acquisition in streptococci is slower than what is experienced in Enterobacteriaceae, probably due to the much more limited horizontal spread of resistance genes. Nonetheless, transposons or integrative and conjugative elements can disseminate resistance determinants among streptococci. Besides providing key elements on the prevalence of resistance in streptococci from animals, this article will also largely consider the mechanisms and molecular epidemiology of the major types of resistance to antimicrobials encountered in the most important streptococcal species in veterinary medicine.

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.

Unusual cause of severe diabetic ketoacidosis precipitated by Streptococcus bovis/equinus (SBSEC) bacteremia: Case report and review of literature

Diabetic ketoacidosis is a feared complication in patients with diabetes mellitus and poses high risk of mortality and morbidity unless treated in timely manner. Infection is one of the most common precipitating factors for the development of diabetic ketoacidosis. Bacteremia with Group A and Group B beta hemolytic streptococcal strains are well known, however nonenterococcal Group D strains such as the Streptococcus bovis/Streptococcus equinus complex (SBSEC) still remains an understudied entity. Here we present a case of a 35-year-old Type I diabetic female presenting with severe diabetic ketoacidosis with overlapping features of hyperosmolar hyperglycemia, precipitated by Streptococcus alactolyticus bacteremia, successfully treated with four-week course of parenteral ceftriaxone. This case report emphasizes the potential importance of SBSEC as an emerging pathologic strain and culprit for triggering diabetic ketoacidosis which requires prompt diagnosis and targeted therapy.

A Rare Case of Streptococcus alactolyticus Infective Endocarditis Complicated by Septic Emboli and Mycotic Left Middle Cerebral Artery Aneurysm

To date, S. alactolyticus endocarditis complicated by middle cerebral artery aneurysm has not been reported. We describe the case of a 65-year-old female with a history of hypertrophic cardiomyopathy with left ventricular outflow tract obstruction presenting with confusion and a apical holosystolic murmur. Angiography of the brain identified new bilobed left middle cerebral artery aneurysm. Serial blood cultures grew S. alactolyticus, and aortic and mitral valve vegetation were discovered on transesophageal echocardiography. The patient was treated with antimicrobial therapy, mitral and aortic valve replacements, and microsurgical clipping of cerebral aneurysm. This case serves to highlight the pathogenicity of a sparsely described bacterium belonging to the heterogenous S. bovis complex.

Hyperbaric hyperoxia alters innate immune functional properties during NASA Extreme Environment Mission Operation (NEEMO)

BACKGROUND

Spaceflight is associated with immune dysregulation which is considered as risk factor for the performance of exploration-class missions. Among the consequences of confinement and other environmental factors of living in hostile environments, the role of different oxygen concentrations is of importance as either low (e.g. as considered for lunar or Martian habitats) or high (e.g. during extravehicular activities) can trigger immune dysfunction. The aim of this study was to investigate the impact of increased oxygen availability--generated through hyperbaricity--on innate immune functions in the course of a 14 days NEEMO mission.

METHODS

6 male subjects were included into a 14 days undersea deployment at the Aquarius station (Key Largo, FL, USA). The underwater habitat is located at an operating depth of 47 ft. The 2.5 times higher atmospheric pressure in the habitat leads to hyperoxia. The collection of biological samples occurred 6 days before (L-6), at day 7 (MD7) and 11/13 (MD11/13) during the mission, and 90 days thereafter (R). Blood analyses included differential blood cell count, ex vivo innate immune activation status and inhibitory competences of granulocytes.

RESULTS

The absolute leukocyte count showed an increase during deployment as well as the granulocyte and monocyte count. Lymphocyte count was decreased on MD7. The assessments of native adhesion molecules on granulocytes (CD11b, CD62L) indicated a highly significant cellular activation (L-6 vs. MD7/MD13) during mission. In contrast, granulocytes were more sensitive towards anti-inflammatory stimuli (adenosine) on MD13.

CONCLUSION

Living in the NEEMO habitat for 14 days induced significant immune alterations as seen by an activation of adhesion molecules and vice versa higher sensitivity towards inhibition. This investigation under hyperbaric hyperoxia is important especially for Astronauts' immune competence during extravehicular activities when exposed to similar conditions.