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We describe a case of Salmonella typhimurium osteomyelitis in an immunocompetent adult male patient without sickle cell disease. We are not aware of a previous report of this combination.
A decrease in incidence of food-borne salmonellosis has been reported in the US and the UK.1 In contrast, the rates of resistance and multidrug resistance are increasing world-wide. Of particular concern are the increasing rates of multidrug resistant Salmonella typhimurium.1 Systemic infections are, therefore, becoming an increasing problem for clinicians. There are no unified clinical studies or antibiotic and surgical guidelines in the management of the condition.
S. typhimurium multiplies in the gastrointestinal tract of many animal species where it usually causes no disease. In humans, its growth causes gastroenteritis, usually 6–48 h after ingestion of contaminated water or food (usually poultry or beef). Illness may begin with nausea and vomiting, followed by diarrhoea. In healthy adults, the disease is usually self-limiting with good medical care. It is more serious in the young, the elderly and those with underlying medical conditions. The case-fatality ratio can be as high as 5–10% in nurseries and nursing homes. Isolations of Salmonella causing gastroenteritis in humans have increased in recent years in developed countries, primarily because modern methods of animal husbandry, food preparation, and distribution encourage the spread of Salmonella spp.
We describe a case of S. typhimurium osteomyelitis in an immunocompetent adult male patient without sickle cell disease. We are not aware of a previous report of this combination.
A 58-year-old Caucasian man was referred to our out-patient department with a 4-month history of pain and swelling in his right chest wall of spontaneous onset. Two months prior to attending the clinic, two sinuses developed on his right chest wall, which started to drain serous fluid. Swabs taken at the time grew methicillin-sensitive Staphylococcus aureus (MSSA). He was initially treated appropriately by his general practitioner, but these sinuses continued to heal and then re-open, at which point he was referred to us (Fig. 1). He denied any history of gastrointestinal symptoms in the preceding 12 weeks. Initially, a debridement and rib resection was performed and samples were sent for histology and microbiology. This demonstrated the staphylococcus and chronic inflammatory changes. No acid-fast bacilli were observed. The wound was primarily closed, the patient recovered well and was discharged with a low white cell count (WCC) and decreasing C-reactive protein (CRP) level on appropriate antibiotics.
On clinic follow-up, the wound was found to be developing discharging sinuses again, and a bone scan showed a focal uptake in the remaining 6th rib costochondral junction and surrounding soft tissues, consistent with infection. CRP and WCC continued to increase, despite continued antibiotic therapy. Differential diagnosis at this stage included tuberculosis and staphylococcus osteomyelitis.
The patient was re-admitted and a more extensive chest wall resection was performed (Fig. 2). A vacuum dressing was applied to achieve wound closure by secondary intent. Samples were once again taken for histology and microbiology, including cultures for acid-fast bacilli.
On this occasion, culture of the rib grew S. typhimurium, sensitive to ciprofloxacin, which was promptly prescribed. On further questioning, he denied any history of travel, or episodes of diarrhoea. Sexual history did not reveal any other possible source of infection and his sickle cell screen was negative. He is currently still being followed-up in our out-patient department, continuing on antibiotic treatment and vacuum dressings. The wound is closing steadily and there are no macroscopic signs of infection (Fig. 3), the WCC and inflammatory markers are within normal limits.
There are over 2000 sero-species in the Salmonella genus, Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Typhi being the two most important in human disease. Serovar Typhimurium is mainly responsible for gastroenteritis in humans (salmonellosis or food poisoning), whereas typhoid fever is associated with S. enterica serovar Typhi.2 Both variants are associated with faeco-oral spread. Extra-intestinal manifestations of salmonella infections include arterial infection, meningitis, abscess formation and osteomyelitis.3
Various case reports of salmonella osteomyelitis and septic arthritis exist. These are associated with immune suppression, sickle cell disease, haematological malignancies and involved mainly infants and neonates.4,5 In all reports, it was also remarked how similar the presentation was to tuberculous osteomyelitis.6 Salmonella infections are common in the developing world. In England and Wales, S. typhimurium accounts for 25% of infections.1 This makes it the second most frequently isolated species.
Treatment of salmonella osteomyelitis can be difficult. No randomised or case-control studies have been reported. There is no consensus for antimicrobial guidelines and indications of surgery for treatment of acute or chronic infection. Treatment is based on case reports and case series. There is no consensus on ways to prevent chronic or relapsing osteomyelitis. There are reports advocating aggressive treatment with surgery and intravenous antibiotics,7 whilst others favour prolonged parenteral antibiotics to decrease future relapsing infection.8
The antibiotic choice, as in our case, should be guided by the results of in vitro susceptibility studies. It is, therefore, important not to commence treatment before samples can be obtained for microbiological, culture and sensitivity analyses. Penicillins, chloramphenicol, third-generation cephalosporins, aminoglycosides and quinolones are all useful alone or in combination treatment for salmonella osteomyelitis.9 There are, however, cases of microbial resistance with the development of chronic infection. Our patient was treated successfully with repeated wide surgical resection and subsequent parenteral antibiotics. On first presentation, early surgery to remove deep-seated, infected tissue followed by an aggressive antibiotic regimen guided by microbiological sensitivities is essential in achieving long-term cure.
Ciprofloxacin has been recommended for the treatment of chronic infections as it has excellent bone penetration.10 The optimum duration of treatment is not defined but is best guided by the clinical state of the patient and biomarkers of infection (WCC and CRP). We cannot be certain that the infection has been completely eradicated, hence the patient remains under surveillance. Other modalities of treatment that have been attempted include hyperbaric oxygen treatment.10
Unusual causative organisms must be borne in mind when a patient presents with osteomyelitis. Early surgical debridement and resection followed by sensitivity-guided antibiotic treatment are vital with prolonged follow-up to ensure eradication of infection.