blaCTX-M-I group extended spectrum beta lactamase-producing Salmonella typhi from hospitalized patients in Lagos, Nigeria

PURPOSE The global spread of bla CTX-M-I extended-spectrum beta-lactamase (ESBL)-producing Salmonella spp. remains a major threat to treatment and control. Evidence of emergence and spread of this marker are lacking in Nigeria. This study investigated bla CTX-M-I ESBL production among Salmonella isolates from hospitalized patients. METHODS Patients (158 total) made up of two groups were evaluated. Group A was composed of 135 patients with persistent pyrexia and group B was composed of 23 gastroenteritis patients and their stool samples. Samples were cultured, and isolates were identified and were subjected to antibiotic susceptibility testing by standard methods. Isolates were further screened for ESBL production, bla CTX-M-I genes and transferability by double disk synergy test, plasmid extraction, polymerase chain reaction, and conjugation experiment. RESULTS Thirty-five (25.9%) Salmonella isolates were identified from group A, of which 74.3% were S. typhi, 22.9% were S. paratyphi and two (5.7%) were invasive non-typhoidal S. enteritidis. Nine Plasmodium falciparum infections were recorded, four of which were identified as co-infections with typhoidal Salmonella. Only two (8.7%) S. enteritidis samples were obtained from group B (P>0.05). A total of 24 isolates were ESBL-positive, eliciting resistance to five to seven antibiotics, and were multiple-drug resistant. ESBL production due to the bla CTX-M-I gene cluster was detected in eleven (45.8%) Salmonella isolates. Nine (81.8%) of the eleven bla CTX-M-I ESBL producers were S. typhi and two (18.2%) isolates were S. enteritidis. Four of nine S. typhi bla CTX-M-I ESBL-producing strains harbored 23 kb self-transmissible plasmid that was co-transferred with cefotaxime and augmentin resistance to Escherichia coli j53-2 transconjugants. CONCLUSION This study revealed the emergence of bla CTX-M-I S. typhi as an agent of persistent pyrexia with potential to spread to other Enterobacteriaceae in Lagos, Nigeria. Cautionary prescription and judicious use of third-generation cephalosporins, particularly cefotaxime, for the treatment of typhoid fever and routine screening for P. falciparum co-infection with ESBL-producing Salmonella in the laboratories during diagnosis of persistent pyrexia conditions in patients are recommended.