Boar Semen Bacterial Contamination in Italy and Antibiotic Efficacy in a Modified Extender

Figures & data

Table 1. Composition (% w/w) of the modified extender used in the study.

Component	ME-S
Fructose^°	78.60
Potassium chloride^#	1.56
Sodium bicarbonate^#	2.67
Na EDTA^#	2.67
Sodium citrate^#	12.00
Amikacin sulphate^#	2.50

ME-S, Modified extender short-term; EDTA, Ethylenediaminetetraacetic acid.

°Supplier: Acef SpA, Fiorenzuola D’Arda (PC), Italy;

^#supplier: Sigma-Aldrich, St. Louis, MO, USA.

Table 2. Bacterial contaminants and antibiotic resistance in raw semen.

Antibiotic	E. coli n=20	Staph. epidermidis n=8	Serratia marcescens n=6	Proteus mirabilis n=4	Streptococcus spp. n=2	Staph. aureus n=2	Pseudomonas spp. n=1
Amikacin (30 μg)	10 (50%)	1 (12.5%)	4 (66.6%)	1(25%)	0 (0%)	0 (0%)	0 (0%)
Amox. + Clav. acid (30 μg)	11 (55%)	2 (25%)	4 (66.6%)	2 (50%)	0 (0%)	1 (50%)	1 (100%)
Ampicillin (25 μg)	15 (75%)	3 (37.5%)	5 (83.3%)	3(75%)	0 (0%)	1 (50%)	1 (100%)
Aztreonam (30 μg)	11 (55%)	0 (0%)	3 (50%)	1(25%)	0 (0%)	1 (50%)	1 (100%)
Aminosidine (60 μg)	nd	3 (37.5%)	4 (66.6%)	nd	nd	1 (50%)	nd
Cefapirin (30 μg)	nd	2 (25%)	nd	nd	nd	nd	0(0%)
Cefazolin (30 μg)	11 (55%)	3 (37.5%)	5 (83.3%)	3(75%)	0 (0%)	1 (50%)	1 (100%)
Cefoperazone (30 μg)	13 (65%)	1 (12.5%)	5 (83.3%)	2 (50%)	0 (0%)	1 (50%)	N.D.
Ceftiofur (30 μg)	4 (20%)	1 (12.5%)	4 (66.6%)	0 (0%)	0 (0%)	1 (50%)	1 (100%)
Ceftriaxone (30 μg)	nd	0 (0%)	nd	nd	0 (0%)	nd	nd
Cefquinome (30 μg)	7 (35%)	3 (37.5%)	5 (83.3%)	3(75%)	0 (0%)	0 (0%)	0(0%)
Colistin (10 μg)	19 (95%)	7 (87.5%)	6 (100%)	4(100%)	1 (50%)	2 (100%)	1 (100%)
Doxiciclina (20 μg)	17 (85%)	3 (37.5%)	5 (83.3%)	1(25%)	0 (0%)	1 (50%)	1 (100%)
Danofloxacin (5 μg)	17 (85%)	3 (37.5%)	5 (83.3%)	4(100%)	0 (0%)	1 (50%)	1 (100%)
Enrofloxacin (5 μg)	1 (5%)	0 (0%)	6 (60%)	1(25%)	0 (0%)	0 (0%)	1 (100%)
Florfenicol (30 μg)	13 (65%)	2 (25%)	3 (50%)	3(75%)	0 (0%)	0 (0%)	1 (100%)
Flumequine (30 μg)	12 (60%)	2 (25%)	5 (83.3%)	3(75%)	0 (0%)	1 (50%)	1 (100%)
Gentamicin (10 μg)	14 (70%)	4 (50%)	3 (50%)	2 (50%)	1 (50%)	2 (100%)	0 (0%)
Marbofloxacin (5 μg)	0 (0%)	0 (0%)	0 (0%)	1(25%)	0 (0%)	0 (0%)	0 (0%)
Oxitetracyclin (30 μg)	17 (85%)	3 (37.5%)	5 (83.3%)	4(100%)	0 (0%)	1 (50%)	1 (100%)
Penicillin G (10 μg)	17 (85%)	3 (37.5%)	5 (83.3%)	4(100%)	0 (0%)	1 (50%)	1 (100%)
Rifaximin (40 μg)	14 (70%)	3 (37.5%)	5 (83.3%)	1(25%)	0 (0%)	1 (50%)	1 (100%)
Streptomycin (10 μg)	17 (85%)	3 (37.5%)	5 (83.3%)	3(75%)	0 (0%)	1 (50%)	1 (100%)
Tiamulin (30 μg)	20 (100%)	7 (87.5%)	6 (100%)	4(100%)	1 (50%)	2 (100%)	1 (100%)
Tylosin (30 μg)	20 (100%)	7 (87.5%)	6 (100%)	4(100%)	2 (100%)	2 (100%)	1 (100%)

nd, not detected.

Table 3. Comparison of bacterial contamination in extenders containing amikacin (ME-S) and gentamicin (CRONOS^TM) during storage at 15±1°C.

		Survival of bacteria isolated in diluted semen
Bacterial isolates	Semen samples diluted		Semen storage 48 h		Semen storage 120 h
	ME-S (n=35)	CRONOS^TM (n=25)	ME-S (n=35)	CRONOS^TM (n=25)	ME-S (n=35)	CRONOS^TM (n=25)
Escherichia coli	12	8	3 (25%)	4 (50%)	3 (25%)	4 (50%)
Staphylococcus epidermidis	5	3	0	0	0	0
Serratia marcescens	2	4	0	2 (50%)	0	2 (50%)
Proteus spp.	0	4	0	1 (25%)	0	1 (25%)
Streptococcus spp.	2	0	0	0	0	0
Pseudomonas spp.	1	0	0	0	0	0
Staphylococcus aureus	1	1	0	1 (100%)	0	1 (100%)
Total strains	26	17	4	7	4	7

ME-S, modified extender short-term.

Table 4. Analysis of variance (P) of factors affecting boar semen contamination.

	Type of extender	Breed of boar	Herd	RSE	R^2
Raw semen
Aerobic	ns	ns	0.035	0.544	0.503
Anaerobic^°	ns	ns	0.028	0.474	0.373
Diluted semen, 48 h
Aerobic	0.083	ns	0.021	0.311	0.556
Anaerobic^°	ns	ns	0.004	0.114	0.492
Diluted semen, 120 h
Aerobic	0.083	ns	0.021	0.311	0.556
Anaerobic^°	ns	ns	0.004	0.114	0.492

ns, not significant; RSE, relative selection efficiency.

°Facultative anaerobic.

Table 5. Least squares means of degree of contamination as affected by type of extender.

	Raw semen		Diluted semen^°
Group	ME-S	CRONOS^TM	ME-S	CRONOS^TM
Aerobic	0.641±0.099	0.784±0.118	0.094±0.057^a	0.284±0.068^b
Anaerobic^#	0.318±0.087	0.353±0.103	0.000±0.021	0.029±0.025

ME-S, Modified extender short-term. Degree of contamination refers to the following parameters: 0=sterile, 1=contaminated by one bacteria species, 2=contaminated by two bacteria species.

°After 48 and 120 h;

^#facultative anaerobic.

^a,bMeans in the same raw with different superscript are significantly different at 0.10<P>0.05.