Survival, Virulence Gene Expression and Difference in the Drug Susceptibility of Non-typhoidal Salmonella in Gut Physiological Conditions
Abstract Salmonella is one among the most versatile and resilient enteric pathogens that known to have developed various survival strategies within the host system. The ability of the bacteria to circumvent the physiological parameters as well as dodge the antimicrobial stress environment within the host is one of the most crucial steps in establishing an infection. With an alarming rise in multi-drug resistant serovars of non-typhoidal Salmonella and lack of vaccine for combatting the infections, behaviour of the bacteria in the presence of host physiological gut conditions (NaCl, high and low iron) and antibiotics will help in understanding the survival strategies as well as mechanisms of resistance. 59 non-typhoidal Salmonella serovars isolated from poultry and seafood were used in the study. The isolates were screened for their antibiotic susceptibility patterns. Two multi-drug resistant and two sensitive serovars were used for growth kinetics and virulence gene expression study. The results obtained revealed that despite similar resistance pattern, the effect of individual class of antibiotics on the growth of serovars varied. On contrary, no significant difference was observed in growth pattern on exposure to in vitro gut like experimental conditions. Nevertheless, the in-vitro gut conditions and exposure to antibiotics have drastically reduced the minimum inhibitory concentration of antibiotics in resistant strains. A first of its kind study that draws attention on the significant effect of antibiotics and gut physiological conditions on MIC and expression of virulence genes from Salmonella pathogenicity island (SPI) 1 and 2 between resistant and sensitive non typhoidal Salmonella serovars.