Plasmid Carriage and ESBL Production among Salmonella Enterica Serovar Typhi from Some Parts of Adamawa State, Nigeria

Abstract

Effective treatment of typhoid fever caused by Salmonella enterica serovar Typhi has been hampered by the emergence of multidrug-resistant and extended-spectrum beta-lactamase (ESBL) producing strains, thus making the organism an important public health pathogen, especially in developing countries. This study was aimed at screening Salmonella ser. Typhi isolates from suspected enteric fever patients for the presence of plasmids as well as ESBL production. Eighty-four (84) Salmonella ser. Typhi isolates were obtained from blood and stool cultures, giving a prevalence of 17.5%. Results of susceptibility screening revealed that 37.5% of the isolates demonstrated the ability to produce extended-spectrum beta-lactamase in vitro, out of which 37.5% were isolates from Yola, while 40% were isolates recovered from Gombi. Furthermore, 41 (48.8%) of the isolates from this study bore plasmids, out of which 25 (47.1%) were from Yola metropolis, while 13 (41.9%) were from Gombi Local Government Area. The most common antibiotic-resistant marker borne on the plasmids carried by S. ser. Typhi in the study area was resistance to AmpC Co (20), followed by the resistance gene for ceftriaxone (10). Screening of the isolates for extended-spectrum beta-lactamase activity using the double disk synergy test revealed that 9 isolates, namely; Salmonella ser. Typhi isolates GMB1, 6, 13, 26 and Salmonella ser. Typhi YLA 4, 11, 22, 31, and 42, showed positive ESBL activity. The PCR analysis revealed the presence of the Blactx gene cluster in 4/25 (16%) of S. Typhi isolates. The detection of some strains with resistance to ceftriaxone as well as the ability to produce ESBL is an early warning sign, indicating the need for more controlled use of this drug in the country, especially in the study area.