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A rare case of Colistin-resistant Salmonella Enteritidis meningitis in an HIV-seropositive patient
Roxanne Rule1,2, Nontombi Mbelle3,4, John Osei Sekyere3
1Department of Medical Microbiology, Pathology Building, University of Pretoria, Prinshof Campus, Corner of Steve Biko Road and Dr Savage Road, Pretoria, 0084, South Africa. roxyrule@gmail.com.
Background:
Non-typhoidal salmonellae (NTS) have been associated with invasive disease, notably meningitis, in immunocompromised individuals. Infections of this nature carry high rates of morbidity and mortality. Colistin resistance in salmonellae is a rare finding, more so in an invasive isolate such as cerebrospinal fluid (CSF). Colistin resistance has important infection control implications and failure to manage this phenomenon may lead to the loss of our last line of defence against multi-drug resistant Gram-negative organisms. To our knowledge, this is the first reported clinical case of colistin-resistant Salmonella Enteritidis meningitis in South Africa.
Case Presentation:
We report a case of a young male patient with advanced human immunodeficiency virus (HIV) infection who presented to hospital with symptoms of meningitis. Cerebrospinal fluid (CSF) cultured a Salmonella Enteritidis strain. Antimicrobial susceptibility testing (AST) of the isolate, revealed the strain to be colistin resistant. Despite early and aggressive antimicrobial therapy, the patient succumbed to the illness after a short stay in hospital. Subsequent genomic analysis of the isolate showed no presence of the mcr genes or resistance-conferring mutations in phoPQ, pmrAB, pmrHFIJKLME/arnBCADTEF, mgrB, and acrAB genes, suggesting the presence of a novel colistin resistance mechanism.
Conclusion:
Invasive non-typhoidal salmonellae infection should be suspected in patients with advanced immunosuppression who present with clinical features of meningitis. Despite early and appropriate empiric therapy, these infections are commonly associated with adverse outcomes to the patient. Combination therapy with two active anti-Salmonella agents may be a consideration in the future to overcome the high mortality associated with NTS meningitis. Colistin resistance in clinical Salmonella isolates, although a rare finding at present, has significant public health and infection control implications. The causative mechanism of resistance should be sought in all cases.
Insights
A rare case of colistin-resistant Salmonella Enteritidis meningitis in an immunocompromised patient in South Africa highlights the urgent need for novel resistance mechanisms research. This invasive infection led to a fatal outcome despite aggressive treatment.
Area of Science:
- Infectious Diseases
- Microbiology
- Genomics
Background:
- Non-typhoidal Salmonellae (NTS) cause invasive infections, particularly meningitis, in immunocompromised individuals, associated with high mortality.
- Colistin resistance in Salmonella is rare, especially in invasive isolates like cerebrospinal fluid (CSF).
- Colistin resistance poses significant infection control challenges, potentially compromising last-resort antibiotic options against multidrug-resistant Gram-negative bacteria.
Observation:
- A young male with advanced human immunodeficiency virus (HIV) presented with meningitis symptoms.
- Cerebrospinal fluid (CSF) culture identified Salmonella Enteritidis.
- Antimicrobial susceptibility testing revealed the isolate was resistant to colistin.
Findings:
- Despite prompt and intensive antimicrobial therapy, the patient did not survive.
- Genomic analysis did not identify known colistin resistance genes (mcr) or mutations in key regulatory genes.
- This suggests a novel mechanism of colistin resistance in this Salmonella Enteritidis strain.
Implications:
- Invasive NTS meningitis requires high suspicion in severely immunocompromised patients presenting with meningitis symptoms.
- These infections carry a high risk of adverse outcomes, even with early, appropriate therapy.
- Investigating the mechanism of colistin resistance is crucial for public health and infection control, and combination therapy may be considered for NTS meningitis.
