What Organisms Cause Osteomyelitis?

Patient Presentation
A 5 week-old white male came to the emergency room with a 1 day history of fever to 39.4 degree Celsius and crying.
He had some loose stools for the past several days but they had no blood, mucous or color change. His brother attended a day care and has had some loose stools for a few days.
There have been no recent day care illnesses or with anyone else the patient has been in contact with.
He had been well with no rashes, emesis, cold symptoms, or coughing. He had been growing well with breastmilk and formula.
There was no history of trauma, including birth injuries.
The past medical history revealed an uncomplicated pregnancy and delivery. He had been seen by his local physician at 1 and 2 weeks of age and was growing well.
The family history was non-contributory.
The pertinent physical exam showed a fussy infant with a temperature of 39.2 degrees Celsius, respiratory rate of 40 respirations/minute, heart rate of 150 beats/minutes, blood pressure of 90/55 mm Hg, weight was 4100 g (50%), height 56 cm (50%) and head circumference 37 cm (25-50%).
The head showed a non-bulging anterior fontanelle. HEENT were normal. Lungs were clear. Heart showed a regular rate and rhythm with no murmurs. There were strong symmetrical peripheral pulses.
Abdomen and GU examinations were normal. Extremity examination showed increased fussiness with general movement of the right leg. There was no redness, warmth or distention to the skin or the leg itself. There was no point tenderness. There was full range of motion in the hips, knees, ankles and toes of both extremities.
The neurological and skin examinations were normal.
The laboratory evaluation and work-up included a complete blood count with a hemoglobin of 13.5 g/dL, hematocrit of 40%, and a white blood cell count of 22,400 x 1000/mm2 with a differential of 50% neutrophils, 20% bands, and 30% lymphocytes.
A C-reactive protein was 1 mg/L (normal 0.08-3.1 mg/L) and the erythrocyte sedimentation rate was 45 mg/hr (normal 1-25 mm/hr).
Cerebrospinal fluid (CSF) examination revealed 2 mononuclear white cells and 5 red blood cells with normal protein and glucose.
Blood, CSF and stool were sent for cultures.
The radiologic evaluation of plain radiographs of the right lower extremity and hip were normal.
During the patient’s clinical course he was begun on Vancomycin and Gentamicin for coverage of common neonatal infections.
Two days after admission the patient’s blood culture grew Salmonella serotype Enteriditis.
The patient continued with fevers and general fussiness for 6 days and then he had increased tenderness to palpation in the right femur. The repeat plain radiographs of the right femr showed an osteolytic lesion in the metaphysis consistent with osteomyelitis on day 6. He was changed to ceftriaxone only after the organism’s sensitivities were finalized on day 7. He became afebrile on day 9. Final cultures of the CSF were negative. Initial stool culture grew Salmonella serotype Enteriditis, but repeated ones were negative. Repeated blood cultures from day 1 and 2 grew the same organism but repeated ones were negative.
Stool cultures for family members were negative and the day care facility was being investigated by the local health department as a potential source. A total of 5 weeks of antibiotics for the diagnosis of salmonella bacteremia with osteomyelitis was planned at discharge.

Salmonella is a gram-negative bacilli belonging to the Enterobacteriaceae family.
There are more than 2460 serotypes that are classified by O-antigen groups (A-E).
The most common serotypes were Typhimurium, Enteritidis and Newport.
Main reservoirs for non-typhoidal Salmonella include livestock, poultry, reptiles and pets.
Transmission is mainly by contaminated food but also contaminated water, medicines, medical equipment, and through animal contacts.
Non-typhoidal Salmonella infections cause gastroenteritis (most common), asymptomatic carriage, bacteremia and focal infections such as osteomyelitis and meningitis.
Intermittent or sustained bacteremia can occur and up to 10% of patients with bacteremia develop focal infections.

Salmonella typhi (serotype group D) is only found in humans and is spread by direct contact or contaminated items. It is uncommon in the US (i.e. ~400 cases/year) but endemic in many other countries.
It causes a protracted bacteremic illness that can include fever, abdominal pain, hepatosplenomegaly, skin changes and mental status changes.
Diarrhea and constipation can occur.

Risks of invasive Salmonella infection and mortality are higher in infants, the elderly, hemoglobinopathies (especially sickle cell anemia) and immunosuppressive conditions.
Children < 5 years excrete the organisms for a longer time than older children and adults. Antibiotic therapy also prolongs the excretion. Chronic carriers (1%) are those who excrete for more than 1 year.
Treatment for localized invasive disease such as osteomyelitis is recommended for 4 or more weeks (6 for meningitis) with ampicillin, ceftriaxone or cefotaxime once organism susceptibilities are known.

Osteomyelitis is an infection of the bone whose exact cause is not well understood but main mechanisms include bacteremia, trauma or local invasion. It can affect any bone but most commonly affects the long bones.
Diagnosis can be difficult as it can present insidiously in children with fever, pain, difficulty walking or bearing weight. Laboratory and radiographic testing may be negative early on and therefore should be re-checked. Radiographic changes on plain radiograph are often not apparent until 10-14 days after illness onset.
Bone scans or magnetic resonance imaging are often used for diagnosis. Empiric treatments should be begun for the clinical situation but should include treatment for S. aureus.
For methicillin-susceptable S. aureus, nafcillin, oxacillin or clindamycin are often used. Vancomycin for methicilin-resistance S. aureus is the usual standard.

Surgical drainage of osteomyelitis can be helpful if a subperiosteal or intraosseous abscess is present. If there is direct extension of an infection, direct inoculation or chronic osteomyelitis, then surgical debridement is necessary. Hyperbaric oxygen can also be helpful with chronic osteomyelitis.

Learning Point
In up to 50% of children, a bacterial organism for osteomyelitis is not identified.

Most common causes of acute osteomyelitis include:

  • Staphylococcus aureus – including an increasing amount of methicillin-resistant organisms
  • Streptococcus pneumoniae
  • Streptococcus pyogenes

Other causes include:

  • Anaerobes – including Bacteroides, Clostridium, Fusobacterium, and Peptostreptococcus
  • Bartonella henselae
  • Kingella kingae – associated with osteoarticular infections
  • Gram-negative enteric organisms – seen in neonates
  • Group B Streptococcus – seen in neonates
  • Pseudomonas aeruginosa – can be associated with puncture wounds to the feet
  • Salmonella species

Haemophilus influenzae used to be a common organism but is less common due to vaccination.

Chronic osteomyelitis is commonly caused by S. aureus and gram-negative enteric bacteria.

Questions for Further Discussion
1. When can a child with Salmonella return to childcare?
2. What type of Salmonella typhi vaccines are available and at what ages can they be given?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Information prescriptions for patients can be found at MedlinePlus for these topics: Bone Diseases and Salmonella Infections
and at Pediatric Common Questions, Quick Answers for this topic: Salmonella

To view current news articles on this topic check Google News.

Kaplan SL. Osteomyelitis in Children. Infect Dis Clin North Am. 2005;19(4):787-97.

American Academy of Pediatrics. Salmonella Infections, In Pickering LD, Baker CJ, Long SS, McMillan JA, eds. Red Book: 2006 Report of the Committee on Infectious Diseases. 27th edit. Elk Grove Village, IL: American Academy of Pediatrics; 2006;59-584.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    7. All medical and invasive procedures considered essential for the area of practice are competency performed.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Interpersonal and Communication Skills
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Systems Based Practice
    23. Differing types of medical practice and delivery systems including methods of controlling health care costs and allocating resources are known.
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.
    26. Partnering with health care managers and health care providers to assess, coordinate, and improve health care and how these activities can affect system performance are known.

    Donna M. D’Alessandro, MD
    Associate Professor of Pediatrics, Children’s Hospital of Iowa

    October 30, 2006