Epidemiological Investigation and Antimicrobial Resistance Profiles of Salmonella Isolated From Breeder Chicken Hatcheries in Henan, China

Abstract

The emergence of antimicrobial-resistant (AR) Salmonella has a major concern worldwide. This study was designed to determine the AR profiles and serovars distribution of Salmonella enterica isolated from different breeds of breeder chickens in the province of Henan, China. For this, 2,139 dead embryo samples were collected from 28 breeder chicken hatcheries, representing two domestic and four foreign breeds. The samples were subjected to the isolation and identification of Salmonella by PCR. The confirmed strains were serotyped according to the Kauffmann-White scheme and their AR profiles against 20 antimicrobial agents were determined by Kirby-Bauer (K-B) disc diffusion method. The results of this study showed the prevalence of Salmonella in 504 strains (23.56%) with a high abundance in southern regions of Yellow River (28.66%, n = 495, N = 1,727) compared to the northern regions (2.18%, n = 9, N = 412) (p < 0.0001). The domestic breeds were more contaminated than imported breeds (p < 0.0001). However, the contamination rate of samples recovered from M-hatcheries was the highest (p < 0.0001). Serotyping method identified 12 serovars, with the dominance of S. Pullorum (75.79%), followed by S. Enteritidis (7.14%). The AR assay showed high resistant to ciprofloxacin (77.00%), sulfisoxazole (73.00%), and ampicillin (55.60%), as well as 98.81% (n = 498) of the isolated strains, were resistant to at least one antimicrobial and 69.64% (n = 351) were resistant to three or more antimicrobials. Among them, one strain of S. Thompson was resistant to 15 antimicrobial agents belonging to eight different classes. In conclusion, Salmonella strains isolated in this study were multidrug-resistant (MDR), presenting a serious problem for human and animal health. Therefore, it is necessary to monitor, control, and rationalize the use of antimicrobials agents in chicken farms in order to limit the increasing resistance against the recent antimicrobial agents.

Keywords: Salmonella; antimicrobial resistance; chicken; embryo; hatchery scale; ma breed; prevalence; san huang breed.

Figure 1

Geographic Distribution of the Sampling Sites Across Different Regions in Henan, China. Sampling sites are denoted as small-scale hatcheries (S), medium-scale hatcheries (M), large-scale hatcheries (L), and unknown-scale hatcheries (Unknown). The blue line denotes the Yellow River, flowing through the province to the east into the Bohai Sea. The arrow shows the geographical north. This map is not drawn to scale.

Figure 2

The hatchery scale variation in the distribution of prevalence of 12 serovars. Serogroup: O:4(B), Entebbe; O:7(C1), Edinburg/Thompson/Tennessee/Tamilnadu; O:8(C2-C3), Fillmore/Gatuni; O:9(D1), Gallinarum (Pullorum)/Enteritidis/Blegdam/Kimpese; O:18(K), Cerro. ***The differencee in prevalence rate of S. Pullorum between M-hatcheries and L-hatcheries was statistically significant (p < 0.001). ****The differencee in prevalence rate of S. Gallinarum between M-hatcheries and L-hatcheries was statistically highly significant (p < 0.0001).

Figure 3

Distribution of the average antimicrobial resistance (in percent) of individual antimicrobials in Salmonella isolates from samples collected across L-hatcheries, M-hatcheries. S-hatcheries have no positive samples. The overall average resistance of Salmonella isolated from M-hatcheries was higher than that of L-hatcheries (p = 0.0013), and the difference in resistance to the individual antimicrobial was statistically highly significant (p < 0.0001).

Figure 4

The prevalence of resistance among Salmonella isolates against the different classes of antimicrobials. The distribution of the average antimicrobial resistance (in percent) of various serotypes to 20 antimicrobials of 12 different classes independent of the source of the strains. The color of individual cells varies with the percentage of antimicrobial resistance. The number in individual cells represents number of resistant strains (n). The names of the antimicrobials (XX′) are abbreviated as KAN, kanamycin; GEN, gentamicin; AMK, amikacin; AMP, ampicillin; AMC, amoxicillin-clavulanic; CRO, ceftriaxone; CAZ, ceftazidime; CFZ, cefazolin; MEM, meropenem; IPM, imipenem; ATM, aztreonam; TET, tetracycline; OTC, oxytetracycline; CST, colistin; CHL, chloramphenicol; ENR, enrofloxacin; CIP, ciprofloxacin; SXT, sulfamethoxazole-trimethoprim; SIZ, sulfisoxazole; NIT, nitrofurantoin.

Figure 5

Prevalence of Antimicrobial Resistance and Serovars between L-hatcheries and M-hatcheries. The upper 3 rows are the distribution in the large-scale hatcheries while the lower rows are the distribution in medium-scale hatcheries. The color of individual cells varies with the percentage of antimicrobial resistance. The number in individual cells represents number of resistant strains (n).

Figure 6

Distribution of Multi-drug resistance (MDR) Strains. MDR patterns for the number of antimicrobials and the distribution of multidrug-resistant strains.

Figure 7

Serovar distribution of Multi-drug resistance (MDR) Prevalence. The left Y-axis shows tetra- and hexa-drug resistance while the right Y-axis shows hepta-drug resistance, except in serovar Enteritidis and octa-drug resistance (see only in S. Pullorum).

Figure 8

Hatchery scale distribution of multi-drug resistance (MDR) prevalence of Pullorum. Hatchery scale are denoted as medium-scale hatcheries (M) and large-scale hatcheries (L). Due to the low diversity of serotypes isolated from L-hatcheries, there were no Thompson, Enteritidis, or Gatuni isolated from L-hatcheries, so here we only compared the MDR strains of Pullorum in L-hatcheries and M-hatcheries (S-hatcheries had no positive samples).