I was phoned a few evenings ago by a very excited orthopaedic surgeon who was convinced he had clinically diagnosed a case of Mycobacterium tuberculosis (MTB) osteomyelitis. The patient had been living and working
in Sub-Saharan Africa for a year and had presented with a painful swelling of the distal end of his clavicle associated with a fever. A sample of pus had been aspirated from the bone by the radiologists and the surgeon wanted an urgent ZN stain for MTB.
in Sub-Saharan Africa for a year and had presented with a painful swelling of the distal end of his clavicle associated with a fever. A sample of pus had been aspirated from the bone by the radiologists and the surgeon wanted an urgent ZN stain for MTB.
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After the discussion I suggested not starting the anti-TB
medication because in my experience these were usually caused by Salmonella spp. and occasionally Staphylococcus aureus. I could tell the surgeon didn’t really believe me but they followed my advice and started IV Ceftriaxone instead.
The ZN was negative as I expected and the next day a Salmonella spp. was growing happily on all of the agar plates. Was I smug? Huh you bet! But what evidence do I have for my decision? Was my reasoning sound?
Salmonella osteomyelitis is reported to be a rare condition,
occurring in 1 in 200 cases of osteomyelitis and representing only 1% of all Salmonella infections. It can be caused by almost any species of Salmonella, the only caveat is that it arises from haematogenous seeding of the bone and
therefore the patient has to have been bacteraemic. Diagnosis of salmonella osteomyelitis requires the isolation of the bacterium from either a blood culture or bone sample. In the UK this usually means the organism will be Salmonella enteritidis, as organisms like Salmonella typhi or Salmonella
paratyphi are rare.
The odd thing about salmonella osteomyelitis is that it only
really seems to affect long bones such as the femur, tibia, humerus and clavicle, as well as the vertebrae. In fact, in the 13 years I’ve been practicing microbiology, I have seen Salmonella spp. 4 times in the clavicle and only once in another bone (the humerus). In contrast I have only seen Staphylococcus aureus, the most common cause of osteomyelitis, twice in the clavicle. So in my experience Salmonella spp. are more common than Staphylococcus
aureus in causing osteomyelitis of the clavicle. I have looked in the literature and cannot find which bones salmonella osteomyelitis would most commonly occur in, nor can I find evidence as to why it may favour settling in the clavicle.
Although not so in my patient, there is a strong association
between salmonella osteomyelitis and sickle cell disease. The reasons for this are likely to be twofold:
• Sickle haemoglobin precipitates out in blood vessels when it becomes deoxygenated leading to obstruction of blood flow through the capillaries and damage to various tissues, especially bone, and hence a bacteria in the bloodstream will be more likely to settle in the damaged bone tissue
• Sickle cell disease decreases the function of the spleen leading to the body failing to fight infections appropriately. This predisposes them to more bacteraemias which in turn results in more secondary seeding of bones and joints
Salmonella osteomyelitis tends to present in the same way as any other type of bone infection with the acute onset of fever, pain, swelling and inability to weight bear.
The treatment is relatively straight forward with at least 2
weeks of IV antibiotics followed by 4 weeks of oral antibiotics with good bioavailability. A common combination is IV Ceftriaxone followed by PO Ciprofloxacin, but the final choice should be guided by antibiotic sensitivity testing.
It is always important in cases where the presentation is
unusual to ask the question, “Why did this patient get this infection?” In this case of salmonella osteomyelitis, it is sensible to ask:
• Does the patient have sickle cell disease or sickle cell trait?
• Does the patient have an abnormally functioning spleen?
If the answer is yes to either of these questions it changes the future management of the patient; both of these patient groups need long-term antibiotic prophylaxis with Penicillin V, as well as immunisation against capsular bacteria such as Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae.
So as little literature exists, what’s your experience of salmonella osteomyelitis? How many times have you seen it? What’s the most common organism that you have seen causing osteomyelitis of the clavicle? Let me and others know by adding a comment either on FaceBook or this blog page.
medication because in my experience these were usually caused by Salmonella spp. and occasionally Staphylococcus aureus. I could tell the surgeon didn’t really believe me but they followed my advice and started IV Ceftriaxone instead.
The ZN was negative as I expected and the next day a Salmonella spp. was growing happily on all of the agar plates. Was I smug? Huh you bet! But what evidence do I have for my decision? Was my reasoning sound?
Salmonella osteomyelitis is reported to be a rare condition,
occurring in 1 in 200 cases of osteomyelitis and representing only 1% of all Salmonella infections. It can be caused by almost any species of Salmonella, the only caveat is that it arises from haematogenous seeding of the bone and
therefore the patient has to have been bacteraemic. Diagnosis of salmonella osteomyelitis requires the isolation of the bacterium from either a blood culture or bone sample. In the UK this usually means the organism will be Salmonella enteritidis, as organisms like Salmonella typhi or Salmonella
paratyphi are rare.
The odd thing about salmonella osteomyelitis is that it only
really seems to affect long bones such as the femur, tibia, humerus and clavicle, as well as the vertebrae. In fact, in the 13 years I’ve been practicing microbiology, I have seen Salmonella spp. 4 times in the clavicle and only once in another bone (the humerus). In contrast I have only seen Staphylococcus aureus, the most common cause of osteomyelitis, twice in the clavicle. So in my experience Salmonella spp. are more common than Staphylococcus
aureus in causing osteomyelitis of the clavicle. I have looked in the literature and cannot find which bones salmonella osteomyelitis would most commonly occur in, nor can I find evidence as to why it may favour settling in the clavicle.
Although not so in my patient, there is a strong association
between salmonella osteomyelitis and sickle cell disease. The reasons for this are likely to be twofold:
• Sickle haemoglobin precipitates out in blood vessels when it becomes deoxygenated leading to obstruction of blood flow through the capillaries and damage to various tissues, especially bone, and hence a bacteria in the bloodstream will be more likely to settle in the damaged bone tissue
• Sickle cell disease decreases the function of the spleen leading to the body failing to fight infections appropriately. This predisposes them to more bacteraemias which in turn results in more secondary seeding of bones and joints
Salmonella osteomyelitis tends to present in the same way as any other type of bone infection with the acute onset of fever, pain, swelling and inability to weight bear.
The treatment is relatively straight forward with at least 2
weeks of IV antibiotics followed by 4 weeks of oral antibiotics with good bioavailability. A common combination is IV Ceftriaxone followed by PO Ciprofloxacin, but the final choice should be guided by antibiotic sensitivity testing.
It is always important in cases where the presentation is
unusual to ask the question, “Why did this patient get this infection?” In this case of salmonella osteomyelitis, it is sensible to ask:
• Does the patient have sickle cell disease or sickle cell trait?
• Does the patient have an abnormally functioning spleen?
If the answer is yes to either of these questions it changes the future management of the patient; both of these patient groups need long-term antibiotic prophylaxis with Penicillin V, as well as immunisation against capsular bacteria such as Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae.
So as little literature exists, what’s your experience of salmonella osteomyelitis? How many times have you seen it? What’s the most common organism that you have seen causing osteomyelitis of the clavicle? Let me and others know by adding a comment either on FaceBook or this blog page.
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