Molecular characterisation and antimicrobial resistance of Streptococcus agalactiae isolates from dairy farms in China

Resistance gene	Primer sequence (5-3’)	Annealing temperature (°C)	PCR product size (base pairs)	Reference
tet(M)	F: GTGGAGTACTACTACATTTACGAG R: GAAGCGGATCACTATCTGAG	55	359	31
tet(O)	F: GCGGAACATTGCATTTGAGGG R: CTCTATGGACAACCCGACAGAAG	51	538
tet(L)	F: GGATCGATAGTAGCCATGGG R: GTATCCCACCAATGTAGCCG	53	516
tet(S)	F: CGCTACATTTGCGAGACTCAG R: GGCTCTCATACTGAATGCCAC	55	569
erm(A)	F: TCTAAAAAGCATGTAAAAGAA R: CTTCGATAGTTTATTAATATTAGT	52	645	27
erm(B)	F: GAAAAGGTACTCAACCAAATA R: CAGTAACGGTACTTAAATTGTTTAC	52	639
mef(A)	F: CGTAGCATTGGAACAGC R: TGCCGTAGTACAGCCAT	50	316
lnu(B)	F: CCTACCTATTGTTTGTGGAA R: ATAACGTTACTCTCCTATTC	57	944	4

Table 2.

Serotyping and sequence types in 21 Streptococcus agalactiae strains

ST	Allelic profile							Number of isolates in MLST (%)	Serotypes (Number of isolates)
ST	adhP	pheS	atr	glnA	sdhA	glcK	tkt	Number of isolates in MLST (%)	Serotypes (Number of isolates)
103	16	1	6	2	9	9	2	11 (52.4%)	Ia (10) NT (1)
312	13	1	1	13	1	9	5	2 (9.5%)	II (2)
67	13	1	1	13	1	1	5	1 (4.8%)	II (1)
309	13	1	1	2	1	9	1	1 (4.8%)	III (1)
1878	13	1	1	13	1	204	5	6 (28.6%)	II (6)

1 MLST – multilocus sequence typing; NT – not typeable

Table 3.

Antimicrobial resistance of Streptococcus agalactiae isolates

Antimicrobial	Phenotypic isolates (n = 21)			MIC (μg/mL)
Antimicrobial	Susceptible	Intermediate	Resistant	Range	MIC₅₀	MIC₉₀
penicillin	21 (100%)	0	0	≤0.13–>64.00	0.13	0.25
ampicillin	15 (71.4%)	0	6 (28.6%)	≤0.13–>64.00	0.25	1.00
amoxicillin/clavulanic acid	18 (85.7%)	1 (4.8%)	2 (9.5%)	≤0.25/0.12–>128.00/64.00	0.25/0.12	0.50/0.25
oxacillin	19 (90.5%)	0	2 (9.5%)	≤0.25–>128.00	0.50	1.00
cephalothin	19 (90.5%)	0	2 (9.5%)	≤0.25–>128.00	0.25	2.00
ceftiofur	20 (95.2%)	0	1 (4.8%)	≤0.25~>128.00	0.25	0.50
erythromycin	8 (38.1%)	3 (14.3%)	10 (47.6%)	≤0.25–>128.00	4.00	128.00
clindamycin	8 (38.1%)	1 (4.8%)	12 (52.1%)	≤0.13–>64.00	32.00	64.00
gentamicin	20 (95.2%)	0	1 (4.8%)	≤0.25–>128.00	1.00	4.00
doxycycline	6 (28.6%)	8 (38.1%)	7 (33.3%)	≤0.25–>128.00	8.00	16.00
florfenicol	20 (95.2%)	0	1 (4.8%)	≤0.25–>128.00	2.00	4.00
tetracycline	3 (14.3%)	0	18 (85.7%)	≤0.25–>128.00	64.00	128.00
kanamycin	14 (66.7%)	4 (19.0%)	3 (14.3%)	≤0.50–>256.00	16.00	64.00
ciprofloxacin	14 (66.7%)	3 (14.3%)	4 (19.0%)	≤0.13–>64.00	1.00	16.00
sulfisoxazole	15 (71.4%)	0	6 (28.6%)	≤2.00–>1024.00	4.00	1024.00
sulfamethoxazole	20 (95.2%)	0	1 (4.8%)	≤0.12/2.40–>64.00/1216.00	0.25/4.80	0.50/9.50

1 MIC₅₀/MIC₉₀ – minimum inhibitory concentration of antimicrobial agents in which 50%/90% of the strains were inhibited in growth

Table 4.

The correlations between resistance phenotypes and drug resistance genes of Streptococcus agalactiae isolates

Antimicrobial classes	Resistant gene	Number of strains with genotype	Number of phenotypes of resistance	Consistency rate (%)
tetracyclines	tet(M)	10	18	55.6%
	tet(O)	7		38.9%
	tet(L)	0		0
	tet(S)	2		11.1%
macrolides	erm(A)	0	10	0
	erm(B)	8		80.0%
	mef(A)	0		0
lincosamides	lnu(B)	0	12	0

Articles in this issue

DOI: https://doi.org/10.2478/jvetres-2023-0027 | Journal eISSN: 2450-8608 (formerly 2300-3235)

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Language: English

Page range: 161 - 167

Submitted on: Dec 23, 2022

Accepted on: Apr 25, 2023

Published on: Jun 16, 2023

Published by: National Veterinary Research Institute in Pulawy

In partnership with: Paradigm Publishing Services

Keywords:

Streptococcus agalactiae,

serotype,

molecular characterisation,

antimicrobial resistance,

drug resistance gene

Related subjects:

Life sciences,

Molecular biology,

Microbiology and virology,

Life sciences, other,

Medicine,

Veterinary medicine

© 2023 Xiaojiao Ma, He Chen, Fulan Wang, Shuai Wang, Yating Wu, Xianlan Ma, Yong Wei, Wei Shao, Yankun Zhao, published by National Veterinary Research Institute in Pulawy
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Volume 67 (2023): Issue 2 (June 2023)