Zoonotic Endocarditis in a Man, the Netherlands

Deficiency of hasB accelerated the clearance of Streptococcus equi subsp. Zooepidemicus through gasdermin d-dependent neutrophil extracellular traps

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus, SEZ) is an essential zoonotic bacterial pathogen that can cause various inflammation, such as meningitis, endocarditis, and pneumonia. UDP-glucose dehydrogenase (hasB) is indispensable in synthesizing SEZ virulence factor hyaluronan capsules. Our study investigated the infection of hasB on mice response to SEZ by employing a constructed capsule-deficient mutant strain designated as the ΔhasB strain. This deficiency was associated with a reduced SEZ bacterial load in the mice's blood and peritoneal lavage fluid (PLF) post-infection. Besides, the ΔhasB SEZ strain exhibited a higher propensity for neutrophil infiltration and release of cell-free DNA (cfDNA) in vivo compared to the wild-type (WT) SEZ strain. In vitro experiments further revealed that ΔhasB SEZ more effectively induced the formation of neutrophil extracellular traps (NETs) containing histone 3 (H3), neutrophil elastase (NE), and DNA, than its WT counterpart. Moreover, the release of NETs was determined to be gasdermin D (GSDMD)-dependent during the infection process. Taken together, these findings underscore that the deficiency of the hasB gene in SEZ leads to enhanced GSDMD-dependent NET release from neutrophils, thereby reducing SEZ's capacity to resist NETs-mediated eradication during infection. Our finding paves the way for the development of innovative therapeutic strategies against SEZ.

A Rare Case of Streptococcus equi Subspecies Zooepidemicus Bacteremia

Streptococcus equi subspecies zooepidemicus (S. zooepidemicus) is a zoonotic pathogen that primarily infects horses, pigs, and dogs. Although rare, it has also been shown to infect humans who consume unpasteurized dairy food or have direct contact with horses. Here, we present a case of S. zooepidemicus bacteremia in a patient without a clear mode of transmission. An 86-year-old male with a past medical history of coronary artery disease, heart failure with reduced ejection fraction, complete heart block status post pacemaker, hypertension, hyperlipidemia, and type 2 diabetes mellitus presented to the Emergency Department with fever and chills. He had fevers and rigors for three days but denied weight loss, cough, sore throat, or rashes. In the Emergency Department, vital signs revealed a fever of 101.2 degrees Fahrenheit and a heart rate of 110 with other stable vital signs. The physical exam was unremarkable except for tachycardia, and laboratory work revealed no leukocytosis but elevated inflammatory markers and elevated lactate. Computed tomography of the chest, abdomen, and pelvis did not reveal any source of infection. Blood cultures grew S. zooepidemicus and the Infectious Diseases team was consulted, who started the patient on Penicillin G. Due to concern for pacer-lead infective endocarditis, transthoracic and transesophageal echocardiograms were performed, which did not show valvular vegetations. Repeat blood cultures showed clearance of the infection, and the patient was ultimately discharged on amoxicillin. While our patient denied consuming unpasteurized dairy products or having direct contact with horses, upon further questioning, he did endorse family members who occasionally interacted with horses. This case is valuable as it adds to the sparse literature on S. zooepidemicus infections specifically in humans. Extensive history taking is of utmost importance when a clear source of infection is not easily identifiable. Further research is also needed to better understand the various modes of transmission of this bacterium to better target and caution those at an increased risk of infection.

Gasdermin D protects against Streptococcus equi subsp. zooepidemicus infection through macrophage pyroptosis

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus, SEZ) is an essential zoonotic bacterial pathogen that can cause various inflammation, such as meningitis, endocarditis, and pneumonia. Gasdermin D (GSDMD) is involved in cytokine release and cell death, indicating an important role in controlling the microbial infection. This study investigated the protective role of GSDMD in mice infected with SEZ and examined the role of GSDMD in peritoneal macrophages in the infection. GSDMD-deficient mice were more susceptible to intraperitoneal infection with SEZ, and the white pulp structure of the spleen was seriously damaged in GSDMD-deficient mice. Although the increased proportion of macrophages did not depend on GSDMD in both spleen and peritoneal lavage fluid (PLF), deficiency of GSDMD caused the minor release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18) during the infection in vivo. In vitro, SEZ infection induced more release of IL-1β, IL-18, and lactate dehydrogenase (LDH) in wild-type macrophages than in GSDMD-deficient macrophages. Finally, we demonstrated that pore formation and pyroptosis of macrophages depended on GSDMD. Our findings highlight the host defense mechanisms of GSDMD against SEZ infection, providing a potential therapeutic target in SEZ infection.

Type A Aortic Dissection With Concurrent Aortic Valve Endocarditis, Subarachnoid Hemorrhage, and Disseminated Intravascular Coagulation

We describe surgical repair of a Stanford Type A aortic dissection with concurrent aortic valve Streptococcus equi endocarditis in the setting of subarachnoid hemorrhage and disseminated intravascular coagulation. Multidisciplinary collaboration among specialists from a variety of disciplines is essential when treating acutely ill cardiovascular patients with multisystem involvement. (Level of Difficulty: Beginner.)

Occurrence and Antimicrobial Susceptibility Profiles of Streptococcus equi subsp. zooepidemicus Strains Isolated from Mares with Fertility Problems

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus), is a β-hemolytic Streptococcus belonging to the Lancefield group C; it is a rare human pathogen, but in horses, it is frequently associated with endometritis. This study aimed to isolate S. zooepidemicus strains, associated with bacterial endometritis in mares, and to define their antimicrobial resistance profile. Twenty-three isolates were recovered from one hundred ninety-six equine uterine swabs (11.7%). Bacterial identification was carried out by Api 20 Strep and confirmed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), while antimicrobial susceptibility testing was performed by disk diffusion method on Muller Hinton agar plates. The antibiotic resistance profiles of the isolates revealed a high percentage of resistance to amikacin (95.6%), ampicillin (73.9%) and tetracycline (69.6%), while ceftiofur and ceftriaxone were highly effective with 82.6% and 78.3% of the isolates inhibited, respectively. An intriguing value of resistance to penicillin (34.8%), which represents the first-choice antibiotic in equine S. zooepidemicus infections, was observed. Furthermore, a high prevalence of multidrug-resistant strains (82.6%) was recorded. Continuous surveillance of this potential zoonotic pathogen and an appropriate antimicrobial stewardship program with the promotion of correct use of antimicrobials, after a proper diagnosis, are needed to allow an effective therapy.