Rare case of osteomyelitis caused by Gardnerella vaginalis and Streptococcus parasanguinis in a postmenopausal woman
- 1 Internal Medicine, Western Michigan University Homer Stryker MD School of Medicine, Kalamazoo, Michigan, USA
- 2 Department of Biomedical Sciences, Western Michigan University Homer Stryker MD School of Medicine, Kalamazoo, Michigan, USA
- Correspondence to Dr Laura D Bauler; laura.bauler@med.wmich.edu
Abstract
Vertebral osteomyelitis is an infection of the vertebrae that can lead to spinal degeneration, most commonly caused by Staphylococcus aureus. Here, we report an unusual case of pyogenic osteomyelitis caused by Gardnerella vaginalis and Streptococcus parasanguinis in a 61-year-old postmenopausal woman. The patient presented with a 2-week history of worsening lower back pain and fever and a recent episode of cystitis following re-engagement of sexual activity. Imaging revealed a deterioration of vertebrae discs and spinal canal stenosis at the L3-L4 levels with a formation of abscess in the right psoas muscle. Needle aspiration of the abscess identified G. vaginalis and S. parasanguinis and the patient was successfully treated with a 6-week course of ceftriaxone and metronidazole. This case describes an unusual coinfection of two pathogens that normally reside in the urogenital tract and oral cavity, respectively, and highlights the risk posed when these organisms breach the body’s normal barriers.
Background
Vertebral osteomyelitis (VO), also known as spondylodiscitis, is an infection of the vertebrae that can extend to adjacent discs and muscles. The slower blood flow in the vascular conduit of the spine allows for bacteria to attach to the surface and grow.1 VO can be caused by haematogenous spread or direct inoculation with pyogenic bacteria, parasites or tuberculosis associated granulomas. Pyogenic VO (PVO) is most commonly caused by a haematogenous seeding of Staphylococcus aureus (42%–58%).2 3
The incidence of VO is increasing due to longer life expectancy, better diagnostic tools and clinical ascertainment, and more frequent use of immunosuppressants and intravascular catheters.4 VO limits a patient’s functional status, increases the risk of falling, and causes complications due to the long-term antibiotic treatment needed to treat the infection. PVO occurs more frequently in older patients, with a mean age of 60 and has male predominance.2 3 Most patients present with back pain, fever, headache, and abdominal pain, but in severe cases, can present with debilitating neurologic deficits. The most prevalent predisposing risk factors of PVO are diabetes mellitus, immunosuppression, renal failure, malignancy, heart disease, liver cirrhosis, alcohol excess, intravenous drug use, HIV infection, spinal surgery and instrumentation, preceding bacteremia.2
Here, we describe a rare presentation of discitis–osteomyelitis in a 61-year-old woman caused by two common bacteria in an uncommon location. The patient suffered from chronic back pain and had recently experienced cystitis/vaginitis caused by recent re-engagement of sexual activity. This case underlines the risk of acute osteomyelitis by Gardnerella vaginalis in a postmenopausal woman with the shift in vaginal microbiome, fragile vaginal mucosa, and re-engagement of sexual activity.
Case presentation
A 61-year-old postmenopausal woman with a medical history of fibromyalgia, chronic back pain, Roux-en-Y gastric bypass surgery presented to the emergency department with a 2-week history of worsening lower back pain in the sacral area radiating to her lumbar spine and diffuse abdominal pain. The patient reported problems with gait due to radiation of pain to her left lower extremity (LLE) and had recently experienced an unprovoked fall at home without significant injury. Hydrocodone–acetaminophen and regular methylprednisolone injections were administered for the pain. The last injection occurred 10 days prior to admission but had not relieved her pain. The patient did not report any problems with sphincter control and had normal motor functions in lower extremities.
The patient had developed non-complicated cystitis 17 days prior to the admission, with pansensitive Escherichia coli, and finished a course of cephalexin. Since then, she reported two episodes of fever around 101°C and diffuse abdominal pain with decreased appetite. Surgical history includes Roux-en-Y gastric bypass (46 years old), pyloric perforation (56 years old) and an L2-L3 spinal fusion surgery more than 15 years ago. Her social history includes cigarette smoking of 15 pack years without intravenous drug or alcohol use. She reported engaging in sexual activities both penile–vaginal and oral–vaginal with two male partners in the last 5 months. Prior to 5 months ago, the patient had not been sexually active for more than 10 years.
Investigations
Physical examination revealed no abnormalities in her respiratory, cardiac, and gastrointestinal systems. There was tenderness in right sacroiliac area with palpation. There was no evidence of swelling or deformity. During the neurological examination, strength was normal in the upper and lower extremities bilaterally, however, deep tendon reflexes in lower extremities were absent. There was no saddle anaesthesia, urinary/faecal incontinence, or sensation deficits.
Laboratory tests revealed a peripheral white blood cell count of 7.6×109/L, a haemoglobin level of 107 g/L, a platelet count of 723×109/L, a C reactive protein (CRP) level of 100.7 mg/L and an erythrocyte sedimentation rate (ESR) of 91 mm/hour. The elevated levels of CRP and ESR indicated acute infection and prompted admission for further tests. Blood and urine cultures were negative. CT imaging of the abdomen and pelvis with contrast revealed discitis–osteomyelitis with perivertebral abscess at the L3-L4 level. Subsequent MRI of the lumbar spine demonstrated L3-L4 discitis and osteomyelitis of L3 and L4 and epidural phlegmon extending from L3-L4 to nearly the L4-L5 level posteriorly resulting in focal severe central canal stenosis and also noted was a right psoas muscle abscess (figures 1–3). The culture from a needle aspiration of the phlegmon was positive for Streptococcus parasanguinis and G. vaginalis.
MRI of the lumbar spine. Sagittal T2-weighted image, showing discitis at L3 (arrowhead).
MRI of the lumbar spine. Sagittal T1-weighted image showing osteomyelitis at the L3-L4 level (bracket).
MRI of the lumbar spine. Axial T1-weighted image showing an abscess in the right psoas muscle at L4-L5 (arrowhead).
Differential diagnosis
Inflammatory spinal diseases such as osteomyelitis–discitis were the top differential diagnosis due to progressive pain, fever, and elevated CRP and ESR. Based on the recent E. coli cystitis with acutely worsening pain and chronic back pain, there was initially some suspicion for pyelonephritis. However, this was unlikely given that the biopsies did not show the same organism. Given the patient’s prior gastric bypass surgery, postmenopausal state, and recent fall, a spinal fracture was also considered. Finally, neoplasm was also considered for acute worsening of the chronic back pain with radiation to the LLE and gait problems. Based on the imaging results, a diagnosis of abscess, osteomyelitis and discitis was most appropriate. The possible aetiology of the infection from steroid injection or prior back surgery with retained implants were initially considered. However, common contaminants from steroid injection are more likely to include skin organisms than vaginal or oral cavity organisms. Also, the spinal fusion of L2-L3 occurred more than 15 years prior and the osteomyelitis primarily affected L3 and below not at the L2-L3 region. Based on the culture results, identifying S. parasanguinis and G. vaginalis, and the prevalence of these organisms in the oral and vaginal cavity, respectively, it is more likely that these organisms were introduced via sexual activity.
Treatment
The patient initially received intravenous vancomycin and ceftriaxone and remained stable during the hospitalisation. She did not have recurrent fever nor chills. The pain improved with cyclobenzaprine. After aspirate culture returned, treatment was altered to metronidazole and ceftriaxone. These were continued for a total of 6 weeks as an outpatient.
Outcome and follow-up
After the course of treatment, her back pain improved and pain radiating to the lower extremities resolved, the patient regained normal deep tendon reflexes and strength in her lower extremities. She continued to report mild pain with bending and gait instability which improved with physical therapy and use of a walker. ESR and CRP were measured weekly during and after the treatment for 6 weeks. The inflammatory markers normalised: ESR came down to 14 and CRP to 3.2.
Discussion
The coinfection of G. vaginalis and S. parasanguinis in a vertebral disc and muscle abscess has to our knowledge never been reported. Mixed gram-positive cocci and anaerobic bone and joint infection are relatively common, but when it occurs is usually in the setting of diabetes mellitus or other vasculopathies. Two cases of G. vaginalis discitis were identified in the literature, reported in 1995 and 2009, describing a 50-year-old postmenopausal woman with a 2-month history of chronic lower back pain, and a 31-year-old premenopausal woman with a 5-day history of a worsening frontal headache, who later developed photophobia, vomiting, tenderness in the lumbosacral spine and progressive headache.5 6 G. vaginalis has also been reported as the causative agent for hip arthritis in a 48-year-old woman on immunosupression.7 In 2012, G. vaginalis was reported to cause septic loosening of a hip prothesis in a 71-year-old woman.8 These cases suggest that G. vaginalis can be a causative agent of spine, disc, and joint infections when it crosses the normal barriers of the skin and mucous membranes.
Menopause leads to inevitable changes in female genitourinary system due to hypoestrogenism, leading to vaginal atrophy characterised by decreased vaginal vascularisation, vaginal dryness, and thinning of the vaginal epithelium.9 Under hypoestrogenic conditions, the vaginal mucosa loses its barrier function, elasticity, and secretory action of the Bartholin glands, increasing risk for traumatisation and bacterial vaginosis (BV).10 Additionally, there are changes in the vaginal microbiome due to menopause. The premenopausal vaginal microbiome is dominated by Lactobacillus which uses glycogen to produce lactic acid contributing to a low vaginal pH which prevents infections of the urogenital tract.10 In postmenopausal women due to decreased exfoliation of the epithelium, limiting the nutrient substrate for the vaginal bacteria, the microbiome undergoes a shift, characterised by decreased Lactobacillus and increased susceptibility to dysbiosis.
G. vaginalis is a gram-negative coccobacillus that contributes to BV.11 It is a common cause of urinary and genital tract infections and affects 10%–30% of women in the USA.12 Menopausal women usually have a shift in their vaginal microbiome away from Lactobacillus species toward more diverse communities including pathogenic anaerobes including G. vaginalis.13 Some women with BV may have a malodorous vaginal discharge, but 50% of women with BV are not symptomatic which limits our understanding of the full extent of the pathogenesis of G. vaginalis in the human body.14 S. parasanguinis is a gram-positive bacterium that primarily colonises the human oral cavity. S. parasanguinis contributes to and grows in biofilms, forming dental plaques.15 S. parasanguinis is considered a commensal of the oral cavity; however, when it gains access to other parts of the body, it can cause a variety of disease, including meningitis and endocarditis.16 It is possible that the colonisation from S. parasanguinis resulted from oral–vaginal intercourse. The generation of biofilms is a shared virulence factor of both G. vaginalis and S. parasanguinis, potentially explaining the limitation of clearance of the bacteria by the immune response and contributing to the pathogenesis of these organisms.16 17
The diagnosis of PVO can be difficult due to its generalised and gradually developing symptoms. Thus, it requires a composite of clinical examination, laboratory findings and imaging studies with aspirate or biopsy for accurate diagnosis. Laboratory tests typically show signs of acute infection including increased white blood cells, platelets, CRP, and ESR.2 For the treatment of PVO, it is recommended that the infectious agent is identified, so treatment can be appropriately targeted.11 A recent randomised control trial for the treatment of osteomyelitis indicates that 6 weeks of antibiotics is as effective as 12 weeks with no significant difference in complications.18
Interestingly, our patient exhibited none of the common risk factors for osteomyelitis other than recent urinary tract infection. Considering that G. vaginalis can be part of the normal menopausal microbiome, the recent urinary tract infection, and the fact that our patient had recently re-engaged in sexual activity, it is possible that she developed osteomyelitis due to altered vaginal flora and trauma from sexual intercourse. A previous case report of PVO suggests that infectious agents can reach the L3-L4 spinal region through the Batson’s plexus, a network of veins that connect deep pelvic veins draining the bladder, rectum and genital tract to the internal vertebral venous plexus.6
Learning points
-
Gardnerella vaginalis and Streptococcus parasanguinis are pathogens typically associated with diabetes mellitus and vasculopathies, infection of the vertebrae is rare; furthermore, coinfection of these organisms has not previously been reported.
-
This case highlights the need for better documentation of social history and surveillance of bacterial vaginosis (BV) in postmenopausal women who engage in sexual activities.
-
BV and sexual activity are potential risk factors for extra-vaginal infections in a postmenopausal woman.
-
To prevent disruption of fragile postmenopausal vaginal mucosa, topical oestrogen therapy may be considered.
Footnotes
-
Contributors JJK, LDB and MS conceived of the manuscript. JJK wrote the first draft. All authors reviewed, edited and revised the final manuscript.
-
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
-
Competing interests None declared.
-
Patient consent for publication Obtained.
-
Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.
References
Use of this content is subject to our disclaimer