Antibiotic resistance in patients with liver cirrhosis: Prevalence and current approach to tackle

Table 1 Examples of intrinsic (natural) antibiotic resistance pathways in bacteria

Resistance mechanism	Molecule/process involved	Resistance to antibiotic	Primary host	Genome-encoded	Plasmid-encoded
Decrease in bacterial wall permeability	Reduced porin expression	Different antibiotics	Gram-negative bacteria	oprD gene	No
Increase in efflux	Tripartite RND pump family	Different antibiotics	Gram-negative bacteria	Yes	Yes
Antibiotic inactivation by chemical group transfer	Modification	Aminoglycosides	Gram-negative and Gram-positive bacteria	Yes	Yes
	Oxidation	Tetracyclines	Many bacteria	Tet(X) genes	Yes
Antibiotic hydrolysis	AmpC beta-lactamases	Broad-spectrum beta-lactams	Gram-negative bacteria: Enterobacteriaceae	Yes	Yes
	Carbapenemases	A variety of beta-lactams	Enterobacteriaceae	Yes	Yes
Modification of antibiotic target	Modification of peptidoglycan precursors	Glycopeptides: vancomycin	Gram-positive cocci: Enterococcaceae	vanC, vanD operons	vanA gene claster
	Alteration of LPS	Polymyxins: colistin	Gram-negative: Enterobacteriaceae	Yes	Yes
	Exchange of conventional PBP to PBP2a	Beta-lactams	Staphylococcaceae	mecA gene	Yes

RND: Resistance-nodulation-division pump family; LPS: Lipopolysaccharide; PBP: Penicillin binding protein.