In vitro effect of amoxicillin and clarithromycin on the 3’ region of cagA gene in Helicobacter pylori isolates

Table 1 Minimum inhibitory concentration of the antibiotics and percentages of resistance among strains

Antibiotic	MIC (μg/mL)			Resistance (n = 149)
	MIC50	MIC90	Range	n (%)
Amoxicillin	2	4	0.25-4.0	6 (4)
Clarithromycin	2	4	0.25-4.0	4 (2.7)

2% (3/149) of the isolates showed double resistance. MIC: Minimum inhibitory concentration.

Table 2 Distribution of cagA genotypes (Glu-Pro-Ile-Tyr-Ala motifs) and vacA s and m among Helicobacter pylori isolates obtained from patients with chronic gastritis coming from a region of high risk for gastric cancer, according to profile of in vitro antibiotic resistance

Antibiotic resistance	Isolates	Patients (n = 13)	Genotype	Diagnosis	MIC	EPIYA motifs (molecular weight in pairs of bases)
						Baseline	0.25	0.5	1	2	4
Amoxicillin	Single	SV301	cagA+/vacA s1m1	NAG	4	495	495	495	495	495/200	-
		SV310	cagA+/vacA s1m1	NAG	2	495	495	495	495	-	-
		SV333	cagA+/vacA s1m1	NAG	2	495	495	595/495	595/495	-	-
		SV328	cagA+/vacA s1m1	IM	2	695/595/495	495/300/200	495	NA	-	-
		SV338	cagA+/vacA s1m1	NAG	2	595/495	NA2	NA	NA	-	-
	Mixed	SV316	cagA+/vacA s1m1 cagA-/vacA s1m1	NAG	> 4	495	NA	NA	595/495	495	NA
Clarithromycin	Single	SV336	cagA+/vacA s1m1	NAG	2	595	595	595	595	-	-
		SV440	cagA+/vacA s2m2	NAG	> 4	595	595/495	595/495	NA	NA	NA
	Mixed	SV415	cagA+/vacA s1m1 cagA-/vacA s1m1	NAG	> 4	495	495	495	495	495	2NA
		SV438	Undefined	IM	2	NA2	NA1	NA1	NA	-	-
		SV323	cagA+/vacA s1m1	MAG	2	495	NA	NA	495/200	-	-
					4		NA2	NA2	NA2	NA2
Amoxicillin + Clarithromycin	Single	SV399	cagA+/vacA s1m1	MAG	2	495	NA	495	495	-	-
					2		495/200	NA	495	-	-
		SV433	cagA+/vacA s1m1	NAG	> 4	495	NA	1NA	495	595/495	200
					> 4		495	495	495	495	495

¹Positive for empty-site PCR;

²Negative for EPIYA PCR, cagA-specific PCR and cag empty-site PCR. NA: Did not amplify; PCR: Polymerase chain reaction; EPIYA: Glu-Pro-Ile-Tyr-Ala; NAG: non-atrophic gastritis; MIC: Minimum inhibitory concentration; IM: Intestinal metaplasia; MAG: Multifocal atrophic gastritis without intestinal metaplasia.

Table 3 Detection of cag pathogenicity island in Helicobacter pylori isolates resistant in baseline and in antibiotic dilutions by amplification of the cagA gene n (%)

Method	Detection of the cag PAI
		Dilutions
	Baseline	Amoxicillin	Clarithromycin
	(n = 13)	(n = 32)	(n = 28)
cagA PCR	11 (84.6)	30 (93.8)	22 (78.6)
EPIYA PCR	12 (92.3)	20 (62.5)	16 (57.1)
P value	> 0.05	0.006	0.031

PAI: Pathogenicity island; PCR: Polymerase chain reaction; EPIYA: Glu-Pro-Ile-Tyr-Ala.