Infection of the hip joint by Serratia marcescens

Abstract

A 72-year-old male patient presented to the hospital because of sudden inability to bear weight and without a history of trauma. A fracture of the head of the femur was identified on CT scan of the pelvis. In his history, the patient had a hospital admission 3 months earlier, during which he had a urinary catheter, and a urine specimen was analysed. The same pathogen was found in the patient urine and in the head of the femur specimen. This is a report of blood-borne spread of Serratia marcescens infection from the urothelium to the hip joint, responsible for spontaneous fracture of the femoral head without history of trauma.

Background

Since its discovery in 1819, Serratia marcescens has been considered an ubiquitous and relatively virulent saprophyte.¹ Infections associated with S. marcescens have been found and reported at various sites of the human body, however, localisation in a joint is rare. S. marcescens is an important nosocomial pathogen. Its genetic diversity, and high virulence has led to emergence of multi-drug resistant strains, which makes it a challenge to treat.² Major joint infections with S. marcescens have been sporadically reported in the literature. Cases included in those studies had significant comorbidities such as chronic systemic diseases, drug addiction intravenous lines, arterial lines, urinary catheters and endotracheal tubes or those on prolonged treatment with antibiotics, steroids or immunosuppressive agents.^3–7

We report the first documented case of septic arthritis of the left hip caused by S. marcescens leading to an atraumatic femoral head fracture.

Case presentation

A 72-year-old man presented to the emergency department with an inability to bear weight due to severe pain in his left hip. He was walking the previous day, and woke up unable to mobilise. He denied any recent fall or another trauma. He had a medical history of diabetes mellitus type 2, hypertension, hypercholesterolaemia, alcoholism, gout and diverticulitis. His body mass index was 22.

On examination, he appeared generally well, apyrexial, well oriented and fully conscious. Local examination of the left hip and groin revealed no erythema, swelling, scars or muscle wasting around the affected hip. He did not have any gross deformities of the left lower limb. Palpation of the left hip elicited tenderness on the anterior and lateral regions. He presented with a reduced range of motion. Passive flexion of the left hip was very painful. Minimal discomfort was elicited during internal and external rotation, there was no flexion deformity and Thomas’ test was negative. The affected limb was neurovascularly intact.

Investigations

Plain radiographs of the pelvis were performed and described as free from any obvious fractures around the hip and no obvious soft tissue swelling (figure 1). The blood results showed a slightly elevated white blood cell count (11.8×10⁹/L) and C reactive protein (8.3 mg/L).

Figure 1.

Radiographs on admission — Anteroposterior view of the pelvis.

Following the failed attempt to mobilise with physiotherapy support, the presence of an occult fracture of the left hip was suggested. A CT was performed and the undisplaced fracture of the left head of femur was discovered (figures 2 and 3).

Figure 2.

Computed Tomography scan on admission — Anteroposterior view of the pelvis.

Figure 3.

Computed tomography scan on admission — Axial view of the pelvis.

Reviewing the patient’s previous medical notes, we found that he was admitted to the hospital 3 months earlier and was diagnosed with giant cell arteritis and viral encephalitis. He developed type 1 acute respiratory distress syndrome and was treated with steroids. This hospital admission accounted for 20 days. The patient represented a week later and was readmitted for 3 weeks due to urinary obstruction. During these two admissions, the patient had a urine catheter for the whole period.

Treatment

In the lights of the CT findings, the patient was scheduled for hemiarthroplasty 3 days after admission. During the arthrotomy, 20 mL of turbid yellowish fluid in the hip joint was revealed. This fluid was aspirated and sent for culture and sensitivity, the joint was thoroughly washed, and a cemented bipolar hemiarthroplasty was performed aiming for early mobility and pain relief. Initially, empirical antibiotics (teicoplanin, 400 mg two times a day) were administered for 2 days (figure 4).

Figure 4.

Postoperative X-ray — Anteroposterior view of the pelvis.

The microbiology report confirmed the presence of S. marcescens in the fluid aspirated from the hip. Looking at the patient records, this organism had been isolated 3 months earlier in a urine sample. The organism, a gram-negative bacillus, was sensitive to co-trimoxazole, ciprofloxacin and gentamicin. Antibiotic therapy was therefore adjusted and co-trimoxazole 960 mg two times a day was prescribed for 3 days.

Five days after surgery, the patient was feverish at 38.7°C. Based on the senior microbiologist recommendation, the antibiotic was changed to ciprofloxacin 750 mg two times a day for 6 weeks. The temperature decreased and the patient’s general health began to improve. The histology report showed osteonecrosis with superimposed fracture of the articular surface of the femoral head with no evidence of any neoplasia.

Outcome and follow-up

During the postoperative period his mobility levels consistently improved, and after 7 days from surgery, he could sit comfortably and walk using a Zimmer frame. The patient also developed hospital-acquired pneumonia which was successfully treated with doxycycline initially 200 mg for a single dose followed up by 100 mg daily for 5 days in total, and he was discharged from the hospital 3 weeks following admission.

At the 1-year postoperative follow-up, the patient was mobilising and had a positive Trendelenburg test (figure 5). The wound has healed nicely, with no signs of infection or inflammation. No pain or tenderness elicited on examination of the hip. Blood investigations were normal.

Figure 5.

One-year follow-up X-ray — Anteroposterior view of the pelvis.

The patient was last reviewed 18 months after his hemiarthroplasty, with a similar clinical status (using one stick, and positive Trendelenburg test). The hip and pelvis radiographs were satisfactory, with integrated left hemiarthroplasty in situ, no sign of recurrent infection.

Discussion

S. marcescens infection and femoral head fracture without history of trauma is an unusual finding. To our knowledge, no similar case was previously reported in the literature.

S. marcescens is known to colonise human urothelium^8–10 and around 90% of S. marcescens urinary tract infections are found after instrumentation of the urinary tract.¹⁰ Infection by this organism is more prevalent in patients suffering from urinary tract obstruction and diabetes mellitus. In this clinical case-study: diabetes, alcoholism and prolonged catheterisation contributed to colonisation of the patient’s urinary tract system by S. marcescens.

Septic arthritis itself carries an 11%–15% mortality rate, and around 40% of patients will require surgical intervention.^11–13 S. marcescens septicaemia carries an overall mortality of about 30%¹⁴ with a risk of developing endocarditis and meningitis.¹⁵ Therefore, such cases require careful follow-up and monitoring to ensure that no further colonisation takes place.

The antibiotics of choice, according to microbiological report, were co-trimoxazole, ciprofloxacin and gentamycin. The patient was started on the first two antibiotics shortly after the organism was identified. This ubiquitous and nosocomial pathogen has intrinsic and acquired resistance to antibiotics.¹ The rise of infection rate of multi-resistant variants of S. marcescens has been particularly described in the intensive treatment unit setting.^{16 17} Genomic analysis conducted on S. marcescens have described genetic mechanisms responsible for the emergence of strains highly resistant to numerous antimicrobials therapy.² There is rising resistance to trimethoprim, ampicillin, cefotaxime and piperacillin in particular.^{2 18}

During the surgery, the presence of turbid fluid in the joint increased the likelihood of infection. Therefore, broad-spectrum intravenous antibiotics were started. They were later adjusted according to the culture and sensitivity following the advice of the microbiologists and the guidelines of the British Society of Rheumatology.¹⁹

The spontaneous head of femur fracture on an otherwise healthy bone, with no history of trauma, yet a background of prolonged urinary tract infection requiring catheterisation, and recent lengthy hospitalisation should raise supsition of high-risk gram-negative sepsis.

Musculoskeletal infections by S. marcescens reported in the literature are related to nosocomial infections, chronic wound infections and major traumatic wounds.

Various nosocomial origins of S. marcescens osteomyelitis have been reported, such as isolation of S. marcescens from tubal irrigation fluids used for osteomyelitis treatment, contaminated bottles of solution used to disinfect cardiopulmonary bypass equipment.²⁰ S. marcescens infections were also reported after uses of metal work in orthopaedic surgery such as: nailing for non-union of the fracture of the forearm,²¹ closed fracture of femoral shaft several surgical procedures including intramedullary rodding and plate fixation; in this latter case, the infection and delayed wound healing took over 4 years with chronic sinus before resolving,²¹ or open reduction and internal fixation of a closed fracture of the femur of a young, healthy patient following a road traffic accident.²² A case of S. marcescens infection 4 weeks following a total knee arthroplasty has also been described.²³

Examples of chronic wound infection were sternal infection by S. marcescens declared 13 years after coronary artery bypass surgery,²⁴ and 15 years after a cardiac transplant are also reported. In the first case, the patient postoperative recovery was complicated by a superficial sternal infection, treated with antibiotics. Off note, he presented 3 months prior to surgery with an abscess and sinus on his distal sternum. In the second case, the patient also suffered from sternal folliculitis, and S. marcescens was isolated 7 months before surgery. At the time of surgery, there was no sign of sternal infection. Fifteen years following the cardiac transplantation, this patient represented with fever and sinus on the sternal wound: a CT of his chest showed presternal infection. The collection was drained under echography and S. marcescens was isolated from the microbiology samples. The patient died from multi-visceral organ failure caused by metabolic disorders and acute renal failure.²⁵ The authors speculated that bacterial persistence and re-emergence might have occurred as a consequence of limited antibiotic penetration into the site of infection, phenotypic adaptation by the organism, and possible existence of dormant bacteria in a chronically immunosuppressed patient.²⁵

S. marcescens has been also described in major traumatic wounds infections involving young and healthy adults suffering from open fractures, initially debrided, reduced and primarily closed without materials left in situ.^{21 26}

S. marcescens is an opportunistic and nosocomial pathogen. It accounts for 3.5% of all gram-negative infection in non-intensive care unit patients. Septic arthritis is a serious diagnosis with a fatality of 11%. The British Society of Rheumatology recommends investigating the synovial fluid and imaging, antibiotics and eventually surgical opinion and urgent open debridment is often necessary.¹⁹

In the present case, washout and thorough debridment during hemiarthroplasty implantation followed by 6 weeks of ciprofloxacin 750 mg two times a day allowed us to treat the patient adequately, with good clinical and radiological outcomes at the 18-month follow-up.

Learning points.

• Infection with Serratia marcescens (a gram-negative bacillus) is rare but can colonise the urothelium of patients who have undergone prolonged catheterisation.

• In the reported case, prolonged catheterisation, treatment with steroids, alcoholism and diabetes mellitus may all have contributed to the blood-borne spread of the infection from the urothelium to the hip joint.

• S. marcescens infection should be considered in patients with joint pain and a history of prolonged catheterisation and multiple comorbidities.