Meningitis due to an unusual human pathogen: Streptococcus equi subspecies equi

A case of bacteremia and pneumonia caused by Streptococcus equi subspecies equi infection in a 70-year-old female following horse exposure in rural Wyoming

BACKGROUND

The occurrence of zoonotic infections following an animal exposure continues to be an important consideration for all patients, especially those within agricultural communities. Streptococcus equi subspecies equi (S. equi subsp. equi) is a bacteria known to cause a common infection called 'Strangles' in horses. This article highlights a new case of pneumonia and bacteremia in a patient caused by S. equi subsp. equi following strangles exposure in a horse. Rarely has there been reported horse to human transmission of subsp. equi.

CASE PRESENTATION

A 70-year-old woman attended a rural emergency department with complaints of dry heaving, fever, chills, shakes, and nausea and presented with a cough. She had undergone a screening colonoscopy two days prior with no other significant medical history. The patient had computed tomography (CT) evidence of a pneumonia and positive blood cultures growing S. equi subsp. equi consistent with bacteremia. The patient later disclosed the recent passing of her horse following its sudden illness six days prior to her emergency department presentation. She had cuddled and kissed the horse prior to its death. The patient was treated with IV lactated ringers during the initial evaluation and admission and also received IV piperacillin-tazobactam 4.5 g every eight hours intravenously during her hospital stay. She was transitioned to an oral antibiotic on discharge. Subsequent blood cultures drawn the day after discharge were negative for S. equi subsp. equi, indicating successful treatment of her bacteremia.

CONCLUSIONS

This report discusses an atypical presentation of S. equi subsp. equi infection in an otherwise healthy individual, manifesting as early sepsis, pneumonia, and bacteremia. The patient likely developed this infection following direct contact exposure to her horse who had died from presumed strangles a few days prior to her symptom onset. This case highlights the importance of investigating potential exposures to S. equi subsp. equi in rural areas, areas where farming and ranching are prevalent, particularly among individuals working with horses. It is especially important to acknowledge high risk populations such as immunocompromised individuals with signs and symptoms of meningitis or bacteremia.

Streptococcus equi subsp. equi in Retropharyngeal Abscess: Case Report and Review of Literature

Retropharyngeal abscesses (RPAs) represent the group of deep space infections of the neck. Although RPA is a well-known condition, some aspects of it still may be challenging. Localization, symptoms, and etiology may confuse even the most experienced physicians. S. equi subspecies are zoonotic agents and cause multiple diseases in diverse animals. Infections in humans are rare. This report presents an extremely rare case of retropharyngeal abscess in a 12-year-old girl caused by an infection of Streptococcus equi subsp. equi.

Streptococcus equi subspecies zooepidemicus Meningitis, Septicemia, and Brain Infarcts in a Costa Rican Infant

Streptococcus equi, an equine commensal bacterium, is a rare etiology of septicemia and meningoencephalitis in humans and is extremely infrequent in children. Scarce literature has been published about its clinical presentation, treatment and outcomes in infants. Here, we describe a case of S. equi subsp. zooepidemicus septicemia and meningoencephalitis in a five-month-old Costa Rican infant that was confirmed by peripheral blood and cerebrospinal fluid (CSF) cultures in a regional hospital of the Pacific coast of Costa Rica who developed multiple ischemic cerebral infarcts secondary to infectious vasculitis, a subdural empyema and serious neurological sequelae. We also reviewed the literature on S. equi meningitis in infants under one year of age. This is the first reported case in our country, the fourth reported in infants under one year of age and the second describing multiple cerebral infarcts and subdural empyema in an infant.

Meningoencephalitis with Streptococcus equi Subspecies equi Leading to a Dural Arteriovenous Fistula

Invasive infection with Lancefield group C streptococci in humans is extremely rare, with the vast majority of clinical isolates belonging to Streptococcus dysgalactiae subsp. equisimilis. We report a case of meningoencephalitis in a 69-year-old man caused by Streptococcus equi subsp. equi, a microbe that causes strangles in Equus caballus (i.e., the horse). This is only the fourth infection with this subtype of the central nervous system (CNS) reported in humans. The invasiveness of these bacteria, known to be capable of releasing strongly immunogenic exotoxins, is illustrated by white matter lesions that are present in the acute phase. This patient initially recovered well after treatment with antibiotics and glucocorticoids. However, the patient was readmitted 5 months later with multiple intraparenchymatous cerebral haemorrhages. Cerebral angiography confirmed the presence of a suspected superficial dural arteriovenous fistula (DAVF), which is seldom reported after CNS infection. The invasiveness of these bacteria was illustrated by white matter lesions present in the acute phase and the occurrence of a de novo dural arteriovenous fistula in the follow-up period.

Streptococcus equi subsp. equi meningitis, septicemia and subdural empyema in a child

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Streptococcus equi subsp. equi is a rare cause of meningitis in human hosts.

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Infection may lead to important suppurative complications such as subdural empyema.

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Infection often follows reported contact with horses.

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Outcome is often poor following S. equi subsp. equi meningitis.

Streptococcus equi subsp. equi is a group C β-hemolytic streptococcus, and is an invasive pathogen with a very restricted host, causing the equine infection known as ‘strangles’. It is a poor colonizer in horses, preferentially causing invasion and infection, compared with its ancestor Streptococcus equi subsp. zooepidemicus, which is considered an opportunistic commensal of the equine upper respiratory tract. In humans, S. equi subsp. equi causes invasive infections in immunocompromised hosts, often following close contact with horses. Such infections are associated with a high mortality, as well as a poor neurological outcome in survivors. Beta-lactam antimicrobials form the mainstay of treatment, while neurosurgical intervention is occasionally required. We present the case of a 13-year old boy with systemic lupus erythematosus being treated with hydroxychloroquine, who presented with S. equi subsp. equi meningitis and sepsis after contact with a sick pony. Although he recovered fully following eight weeks of intravenous ceftriaxone and oral rifampin, the clinical course was complicated by subdural empyema requiring neurosurgical evacuation.

Streptococcus equi Infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles-Revised Consensus Statement

This consensus statement update reflects our current published knowledge and opinion about clinical signs, pathogenesis, epidemiology, treatment, complications, and control of strangles. This updated statement emphasizes varying presentations in the context of existing underlying immunity and carrier states of strangles in the transmission of disease. The statement redefines the “gold standard” for detection of possible infection and reviews the new technologies available in polymerase chain reaction diagnosis and serology and their use in outbreak control and prevention. We reiterate the importance of judicious use of antibiotics in horses with strangles. This updated consensus statement reviews current vaccine technology and the importance of linking vaccination with currently advocated disease control and prevention programs to facilitate the eradication of endemic infections while safely maintaining herd immunity. Differentiation between immune responses to primary and repeated exposure of subclinically infected animals and responses induced by vaccination is also addressed.

Prevalence of Streptococcus dysgalactiae subsp. equisimilis and S. equi subsp. zooepidemicus in a sample of healthy dogs, cats and horses

AIMS

To estimate the prevalence of β-haemolytic Lancefield group C streptococci in healthy dogs, cats and horses; to determine if frequent contact with horses was associated with isolation of these species from dogs and cats; and to characterise recovered S. equi subsp. zooepidemicus isolates by multilocus sequence typing.

METHODS

Oropharyngeal swabs were collected from 197 dogs and 72 cats, and nasopharyngeal swabs from 93 horses. Sampling was carried out at the Massey University Veterinary Teaching Hospital, on sheep and beef farms or on premises where horses were present. All animals were healthy and were categorised as Urban dogs and cats (minimal contact with horses or farm livestock), Farm dogs (minimal contact with horses) and Stable dogs and cats (frequent contact with horses). Swabs were cultured for β-haemolytic Streptococcus spp. and Lancefield group C streptococcal subspecies were confirmed by phenotypic and molecular techniques.

RESULTS

Of the 197 dogs sampled, 21 (10.7 (95% CI= 4.0-25.4)%) tested positive for S. dysgalactiae subsp. equisimilis and 4 (2.0 (95% CI=0.7-5.5)%) tested positive for S. equi subsp. zooepidemicus. All these isolates, except for one S. dysgalactiae subsp. equisimilis isolate in an Urban dog, were from Stable dogs. S. dysgalactiae subsp. equisimilis was isolated from one Stable cat. Of the 93 horses, 22 (23.7 (95% CI=12.3-40.6)%) and 6 (6.5 (95% CI=2.8-14.1)%) had confirmed S. dysgalactiae subsp. equisimilis and S. equi subsp. zooepidemicus isolation respectively. Isolation of S. dysgalactiae subsp. equisimilis from dogs was associated with frequent contact with horses (OR=9.8 (95% CI=2.6-72.8)). Three different multilocus sequence type profiles of S. equi subsp. zooepidemicus that have not been previously reported in dogs were recovered.

CONCLUSIONS AND CLINICAL RELEVANCE

Subclinical infection or colonisation by S. equi subsp. zooepidemicus and S. dysgalactiae subsp. equisimilis occurs in dogs and further research on inter-species transmission and the pathogenic potential of these Lancefield group C streptococci is needed. Complete speciation of β-haemolytic streptococci should be recommended in clinical cases and the possible exposure to horses and their environment should be considered in epidemiological investigations.

Endovascular aortic stent graft infection with Streptococcus equi: the first documented case

Streptococcus equi is a common equine infectious disease, but transmission to man is rare and confined to those who commonly come into close contact with horses. Similarly, prosthetic stent graft infection is a rare complication of endovascular aortic aneurysm repair. We describe the first reported case of aortic stent graft with S. equi occurring in a professional racehorse trainer. Clinical presentation, investigations, imaging and management of this case are described. In conclusion, clinicians should consider infection with rare organisms in patients with prosthetic implants who regularly come into contact with horses and other ruminants.

Meningitis due to group C Streptococcus: a case report and review of the literature

Group C streptococci (GCS) are common causes of veterinary diseases and may colonize humans. Human diseases due to GCS are uncommon and generally occur in the elderly and persons exposed to animals or animal products. We report a case of Streptococcus equi subsp. zooepidemicus meningitis in a horse trainer and review 36 cases of GCS meningitis reported in the literature. The median age was 48 y and the majority of patients were previously healthy. Thirty-one percent (11/36) of the reported cases followed equine exposure and 19% (7/36) ingestion of dairy products. Sixty-seven percent (24/36) were found to have concomitant bacteraemia. The case fatality rate was 31% (11/36), and 28% (7/25) of survivors were reported to have residual neurological impairments. At least 4 days of antibiotics were typically required before symptoms improved. Isolates were generally susceptible to beta-lactams. In conclusion, it is important to consider GCS in the differential of bacterial meningitis, in particular in elderly patients exposed to horses or dairy products. Beta-lactams are first-line therapy, but outcomes are poor.

Needlestick and infection with horse vaccine

This report describes a case of accidental needlestick injury involving a live equine vaccination, Equilis StrepE. A vet presented herself to the Emergency Department having accidentally injected herself with an equine vaccination. Her left thumb (injury site) was inflamed and had lymphangitis progressing proximally along her left arm. Her inflammatory markers were not raised. The swelling, erythma and lymphangitis had improved markedly with intravenous antibiotics. She had no sequelae at follow-up. Equilis StrepE is a vaccine for submucosal administration containing a modified live avirulent strain of Streptococcus equi subspecies equi (Strain TW). Group C streptococci infections are pathogenic in horses and uncommon in humans. A search of the literature revealed no prior case report of similar adverse reaction to this vaccine. The vaccine may have harmful effect on human health, if injected accidentally but more evidence needs to be collected.

Development of an unambiguous and discriminatory multilocus sequence typing scheme for the Streptococcus zooepidemicus group

The zoonotic pathogen Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) is commonly found harmlessly colonizing the equine nasopharynx. Occasionally, strains can invade host tissues or cross species barriers, and S. zooepidemicus is associated with numerous different diseases in a variety of hosts, including inflammatory airway disease and abortion in horses, pneumonia in dogs and meningitis in humans. A biovar of S. zooepidemicus, Streptococcus equi subsp. equi, is the causative agent of strangles, one of the most important infections of horses worldwide. We report here the development of the first multilocus sequence typing (MLST) scheme for S. zooepidemicus and its exploitation to define the population genetic structure of these related pathogens. A total of 130 unique sequence types were identified from 277 isolates of diverse geographical and temporal origin. Isolates of S. equi shared a recent evolutionary ancestor with isolates of S. zooepidemicus that were significantly associated with cases of uterine infection or abortion in horses (P<0.001). Isolates of S. zooepidemicus from three UK outbreaks of acute fatal haemorrhagic pneumonia in dogs during 1999, 2001 and 2008 were found to be related to isolates from three outbreaks of this disease in the USA during 2005, 1993 and 2006, respectively. Our data provide strong evidence that S. equi evolved from an ancestral S. zooepidemicus strain and that certain related strains of S. zooepidemicus have a greater propensity to infect particular hosts and tissues.