Table 1.

Changes in expression of virulence factors mediated by exposure to sub-inhibitory concentrations of antibiotics. MDR, multidrug resistant.

bacteria	antibiotic	effect on virulence	references
S. Typhimurium	tetracycline	induction of genes involved in regulation of SPI-1, iron uptake and acid tolerance and motility. Increased invasiveness of epithelial cells	[4]
Pseudomonas aeruginosa	azithromycin	decrease quorum-sensing, motility, synthesis of virulence factors and oxidative stress response. Induction of type III secretion system	[5]
S. Typhimurium	cationic peptides	induction of PhoP/PhoQ and RpoS virulence-related regulons. Repression of genes required for flagella synthesis and the invasion-associated type III secretion system	[6]
S. Typhimurium	amoxicillin, tetracycline	hypervirulence in vitro and in vivo (HEp2 cells and C. elegans, respectively)	[7]
MDR S. Typhimurium	tetracycline	accelerates invasiveness of epithelial cells	[8]
Staphylococcus aureus	cell wall-active antibiotics and fluoroquinolones	induction of virulence factors and quorum-sensing genes	[9]
S. aureus	cell wall-active antibiotics	induction of virulence genes	[10]
Chromobacterium violaceum	protein synthesis inhibitors	induction of quorum-sensing-related virulence factors. Induction of biofilm formation	[11]
S. Typhimurium	nalidixic acid	induction of SPI-2, PhoP/PhoQ, efflux pumps and peptidoglycan synthesis-related genes. Repression of SPI-1, lipopolysaccharide synthesis, motility-related and porins genes	[12]
S. aureus	ciprofloxacin and trimethoprim	induction of recA (SOS response), Φ13 phage-related genes and phage-encoded virulence staphylokinase (sak) gene	[13]
P. aeruginosa and Proteus mirabilis	mupirocin	reduction in flagellin expression which causes inhibition of formation of flagella and reduced bacterial motility	[14]