Comparison of Phenotypic and Genotypic Patterns of Antimicrobial-Resistant Bacteroides fragilis Group Isolated from Healthy Individuals in Vietnam and Japan

Figures & data

Table 1 Identification of Isolations from Form Healthy Individuals in Vietnam and Japan

Species	Number of Isolations
	Vietnam	Japan
Bacteroides caccae	1	0
Bacteroides cellulosilyticus	0	1
Bacteroides fragilis	3	9
Bacteroides ovatus	5	15
Bacteroides stercoris	9	5
Bacteroides thetaiotaomicron	15	6
Bacteroides uniformis	1	1
Bacteroides massiliensis	2	0
Parabacteroides distasonis	27	10
Parabacteroides merdae	0	2
Phocaeicola vulgatus	13	14
Total	76	63

Table 2 Minimum Inhibitory Concentration (MIC) of 18 Antimicrobial Agents Against BFG Isolations from Healthy Individuals in Vietnam and Japan

Antimicrobial Agents	Resistant Breakpoint (µg/mL)^a	Vietnam (n=76)				Japan (n=63)				P value
		MIC Range (µg/mL)	MIC50 (µg/mL)	MIC90 (µg/mL)	%R^c	MIC Range (µg /mL)	MIC50 (µg/mL)	MIC90 (µg/mL)	%R^d	(^c and ^d)
Ampicillin	≥ 2	16 to >128	>128	>128	100	8 to >128	>128	>128	100	_
Ampicillin/sulbactam	≥ 32/16	0.5 to 64	8	32	17.1	1 to 32	8	32	7.9	0.109
Piperacillin	≥ 128	2 to >128	>128	>128	75	4 to >128	128	>128	50.8	0.003
Piperacillin/tazobactam	≥ 128/4	≤0.015 to 128	4	16	1.3	≤0.015 to 32	4	16	0	0.361
Cefazolin	_	16 to >128	>128	>128	_	8 to >128	128	>128	_	_
Cefmetazole	≥ 64	8 to >128	64	>128	61.8	2 to >128	32	128	41.3	0.016
Ceftriaxone	_	16 to >128	>128	>128	_	4 to >128	>128	>128	_	_
Ceftazidime	_	≥128	>128	>128	_	32 to >128	>128	>128	_	_
Meropenem	≥ 16	0.25 to 16	0.5	2	1.3	0.125 to 16	0.25	2	1.6	0.894
Metronidazole	≥ 16	0.25 to 4	1	2	0	0.25 to 2	1	1	0	_
Clindamycin	≥ 8	0.03 to >128	>128	>128	78.9	≤ 0.015 to >128	>128	>128	57.1	0.006
Clarithromycin	_	0.5 to >128	>128	>128	_	0.25 to >128	>128	>128	_	_
Erythromycin	_	2 to >128	>128	>128	_	1 to >128	>128	>128	_	_
Tetracycline	≥ 16	0.25 to 128	32	64	90.8	0.125 to 128	16	64	65.1	< 0.001
Minocycline	≥ 16^b	≤0.015 to 32	4	16	17.1	≤0.015 to 32	4	8	4.8	0.023
Levofloxacin	_	0.5 to 64	4	32	_	0.5 to 64	4	32	_	_
Ciprofloxacin	_	4 to 128	16	64	_	4 to >128	16	128	_	_
Sulfamethoxazole	_	64 to >128	>128	>128	_	32 to >128	>128	>128	_	_

Notes: ^aResistant breakpoints from Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility testing. 30th ed. CLSI supplement M100. ^bThe breakpoint of tetracycline was used to calculate the resistance percentage of minocycline. ^c,dPercentage of resistant isolations to antibiotics based on CLSI in Vietnam and Japan, respectively. ^c,dColumn values were used to calculate the P value at the last column.

Table 3 Distribution of Antibiotic Resistance Genes in B. fragilis and Other Bacteroides in Vietnam and Japan

			Number of Resistance Genes (%)
		n	cepA	cfxA	cfiA	ermF	ermG	linA	mefA	msrSA	tetQ	tetX	tetX1	bexA	qnrB	qnrS
Vietnam	B. fragilis	3	3 (100)	0 (0)	0 (0)	3 (100)	0 (0)	3 (100)	0 (0)	_	3 (100)	0 (0)	_	0 (0)	0 (0)	0 (0)
	Non-fragilis Bacteroides	73	3 (4.1)	37 (50.7)	4 (5.5)	29 (39.7)	5 (6.8)	25 (34.2)	2 (2.7)	_	59 (80.8)	11 (15.1)	_	13 (17.8)	1 (1.4)	5 (6.8)
Total positive strains (%)^a			6 (7.9)	37 (48.7)	4 (5.26)	32 (42.1)	5 (6.6)	28 (36.8)	2 (2.6)	0 (0)	62 (81.6)	11 (14.5)	0 (0)	13 (17.1)	1 (1.3)	5 (6.6)
Japan	B. fragilis	9	8 (88.9)	2 (22.2)	0 (0)	5 (55.5)	0 (0)	2 (22.2)	0 (0)	0 (0)	9 (100)	0 (0)	0 (0)	0 (0)	_	_
	Non-fragilis Bacteroides	54	1 (1.8)	23 (42.6)	3 (5.56)	23 (42.6)	19 (36.1)	8 (14.8)	9 (16.7)	4 (7.4)	38 (70.4)	8 (14.8)	1 (1.9)	6 (11.1)	_	_
Total positive strains (%)^b			9 (14.3)	25 (39.7)	3 (4.8)	28 (44.4)	19 (35.2)	10 (15.9)	9 (14.3)	4 (6.3)	47 (74.6)	8 (12.7)	1 (1.6)	6 (9.5)	0 (0)	0 (0)
P value (^a and ^b)			0.227	0.288	0.892	0.781	<0.001	0.006	0.012	0.026	0.319	0.761	0.270	0.195	0.361	0.038

Notes: cepA, cfxA, cfiA: β-lactamase resistance genes. ermB, ermF, ermG, limA, mefA, msrSA: macrolide–lincomycin–streptogramin (MLS) resistance genes. tetM, tetQ, tetX, tetX1, tet36: tetracycline resistance genes. bexA, qnrA, qnrB, qnrS are quinolone resistance genes. nim: metronidazole resistance genes. catA:chloramphenicol resistance gene. ErmB, tet36, tetM, nim, catA, and qnrA were not found in either country. ^a,bAre percentage of resistant gene positive strains in Vietnam and Japan, respectively. ^a,bAre used for calculating the P value in the last row.

Figure 1 The distribution of cepA, cfxA, and cfiA in BFG strains in Vietnam and Japan based on MIC values for ampicillin.

Abbreviations: BFG, Bacteroides fragilis group; MIC, minimum inhibitory concentration; VN, Vietnam; JP, Japan.

Figure 2 The distribution of resistance genes responsible for tetracycline resistance (tetQ, tetX, tetX1) found in Bacteroides strains in Vietnam and Japan based on MIC values for tetracycline and minocycline. (A) MIC values for tetracycline in Vietnam and Japan (µg/mL). (B) MIC values for minocycline in Vietnam and Japan (µg/mL).

Abbreviations: VN, Vietnam; JP, Japan.