Table 2.

Resistome in the digestive tract of poultry based on metagenome sequencing

Sample	Use of antimicrobials	Name of antimicrobial	Major findings	Reference
Feces (n = 6)	NM	–	–Predominant by tetracycline, MLS, aminoglycoside, and β-lactam.	[30]
Feces (n = 4)	Yes	NS	–Predominant by tetracycline, followed by aminoglycoside.	[120, 121]
Feces (n = 178)	Yes	NS	–Tetracycline, macrolide, β-lactam and aminoglycoside AMR made up the majority of ARGs.	[122]
Feces (n = 12)	Yes	Chlortetracycline	–Predominant by MDR, followed by aminoglycoside, and tetracycline. –Chlortetracycline at low or therapeutic doses did not alter the relative abundance of total ARGs and predominant ARG classes.	[126, 138]
Feces (n = 63)	Yes	NS	–Predominant by tetracycline, followed by MLS, aminoglycoside, and β-lactam. –More abundant ARGs in the fecal samples collected in markets than farms.	[139]
Feces (n = 15)	Yes	Ampicillin	–Predominant by tetracycline. –Ampicillin led to the increase in the abundance of ARGs belonging to β-lactam and bacitracin, and decrease of those belonging to tetracycline. –Increase in β-lactam, bacitracin-resistance, and MDR genes were more evident for oral than intramuscular administration of ampicillin.	[140]
Cecum (n = 10)	Yes	NS	–Predominant by tetracycline, MLS, and cephalosporin resistant genes are the most abundant in two altitudes (730 m and 3300 m). –Differential abundant MLS, cephalosporin, and tetracycline between low and high altitudes.	[141]

ARG antimicrobial resistant gene, MLS macrolide-lincosamide-streptogramin, MDR multidrug resistance, NM not mentioned, NS not specified.