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
Additional file 1: Annotation results of S. Enteritidis strain EC20120916
genome. MLST, pathogenicity island, plasmid typing, resistance gene and
pathogenicity of the strain determined to be ST11, five (C63PI, SPI-5, SPI-
13, SPI-3, SPI-14), IncFII(S) and IncFIB(S), 0.94, and aac (6′)-Iaa respectively.
Additional file 2: Metadata of isolates used for phylogenetic tree Fig.
Additional file 3: Metadata of isolates used for phylogenetic tree Fig. 2B