A rare case of Salmonella Enteritidis meningitis in an HIV-infected patient
Question 1: What differential diagnosis should be considered in this patient?
Answer to Question 1
Question 2: Describe the typical findings in cerebrospinal fluid parameters with bacterial meningitis, cryptococcal meningitis, viral meningitis and TB meningitis
Answer to Question 2The full blood count showed a mild normocytic hypochromic anaemia with Hb of 10.3g/dL, a white cell count of 10.53 x 109/L with a neutrophilia of 8.49 x 109/L, and a platelet count of 460 x 109/L. C-reactive protein and erythrocyte sedimentation rate values were elevated at 130 mg/L and 125 mm/hr respectively. Renal function tests revealed an elevated urea of 13.5 mmol/L with a normal creatinine of 80 μmol/L. The electrolytes were within normal range. Liver function tests revealed a mild elevation in aspartate transaminase (51 U/L) and gamma-glutamyl transferase (92 U/L). Serum cryptococcal antigen and rapid plasma reagin were both negative. Hepatitis B surface antigen was also negative.
Question 3: How does invasive infection with non-typhoidal Salmonellae (NTS) occur in HIV-infected patients?
Answer to Question 3NTS are transmitted through contaminated food or water, contact with animals, and in some cases contact with infected humans. The infectious dose ranges from 103 - 106 organisms. Once ingested, NTS colonise the terminal ileum and colon. A fraction of NTS invade intestinal epithelial cells resulting in intestinal inflammation. NTS exploit this gut mucosal inflammatory response and are able to out-compete the normal gut flora. Crossing the epithelium results in a bacteraemia, following which the NTS enter and survive within macrophages and dendritic cells. This may result in a bloodstream infection or other foci of extraintestinal disease Additionally, persistence in macrophages in systemic tissues can result in recrudescence of invasive disease.
Question 4: What are the risk factors for invasive NTS infections?
Answer to Question 4
Question 5: What is the treatment of choice for NTS meningitis?
Answer to Question 5Therapy should be guided by antimicrobial susceptibility testing. The agent of choice is ceftriaxone, but in cases where the isolate is resistant to ceftriaxone, meropenem is advised. Therapy for at least 3 weeks is recommended. This form of invasive NTS disease typically has a high case-fatality ratio (20%-60%) despite appropriate treatment.
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