Changes in physiology and virulence during the selection of resistant Yersinia ruckeri mutants under subinhibitory cefotaxime concentrations

Abstract

Bacterial antibiotic resistance is one of the main healthcare problems currently. Apart from reducing antibiotic efficacy, it has awakened the interest of scientists due to its association with bacterial fitness and virulence. Interestingly, antibiotic resistance can be a source of both increased fitness and decreased fitness, even though the molecular basis of these relationships remains unknown. The aim of this work is to define the effects of sub‐MIC concentrations of cefotaxime, an antibiotic extensively used in clinical practice, on the physiology and virulence of Yersinia ruckeri and to determine the importance of these sub‐MIC concentrations for the selection of antibiotic‐resistant mutants in the aquatic environment. Results indicated that exposure to sub‐MIC concentrations of cefotaxime selected Y. ruckeri populations with irreversible alterations in the physiology, such as slow growth, aggregation in liquid cultures and modification of the colony morphology. These bacteria also displayed changes in the OMPs and LPS profiles and a full attenuation of virulence. An overexpression of the envelope stress regulator RpoE was also detected after exposure to the antibiotic. In conclusion, exposure to cefotaxime selected, at high frequency, Y. ruckeri strains that survive the antibiotic stress at the expense of a fitness cost and the loss of virulence.

Sub-Inhibitory Concentrations of Amoxicillin and Tylosin Affect the Biofilm Formation and Virulence of Streptococcus suis

“…The tissue organ distribution ( Figure 4 ) showed that, after treatment with 1/4MIC Amoxicillin and Tylosin, the amount of bacteria in the lung, liver, and spleen of the mice was significantly lower than that in the control group. We speculate that this may be caused by the down-regulation of virulence factors by sub-concentration antibiotics [ 35 ]. Furthermore, the results of tissue HE staining ( Figure 5 ) showed that, after treatment with 1/4MIC Amoxicillin and Tylosin, respectively, the damage degree of each tissue was significantly lower than that of the control group, which indicates that 1/4MIC Amoxicillin and Tylosin might be involved in the expression of multiple genes that regulate bacterial virulence [ 36 ].…”

Effect of Licorice (Glycyrrhiza glabra) Extract as an Immunostimulant on Serum and Skin Mucus Immune Parameters, Transcriptomic Responses of Immune-Related Gene, and Disease Resistance Against Yersinia ruckeri in Rainbow Trout (Oncorhynchus mykiss)

“…In brief, the bacterium was cultivated in a nutrient broth, washed, and suspended in phosphate-buffered saline (PBS). The optical density of the bacterial suspension was adjusted to 0.5 at 600 nm ( 33 ). This suspension was serially diluted five times (1:10) by PBS.…”

Estimation of pharmacological properties of ceftiofur, an injectable cephalosporin antibiotic, for treatment of streptococcosis in cultured olive flounderParalichthys olivaceus

“…There are several semisynthetic 3rd‐generation cephalosporins like cefotaxime, ceftriaxone, ceftazidime, cefixime and ceftiofur. These drugs have been examined for their antibacterial activity against bacterial fish pathogens (Blackburn et al., 2010; Chu et al., 2016; García‐Torrico et al., 2019; Kumar et al., 2015; Ottem et al., 2007; Rose et al., 2013), and some are possibly in use for some aquaculture purposes (Yanong, 2019).…”