Molecular epidemiology and genetic characterisation of carbapenem-resistant Acinetobacter baumannii isolates from Guangdong Province, South China.

OBJECTIVES: Carbapenem-resistant Acinetobacter baumannii (CRAB) has become a worldwide issue. This study aimed to characterise the epidemiology and genetic relationships of A. baumannii isolates in Guangdong Province, China. METHODS: CRAB isolates were collected from five municipal hospitals from June-December 2017. The 16S-23S rRNA intergenic spacer region was used for confirmation of strain identity. Antimicrobial susceptibility testing and the CarbAcineto NP test were performed to analyse the resistance spectrum and carbapenemase production of the isolates. PCR-based assays were used to detect ß-lactamase genes and related mobile genetic elements. Genetic diversity among the isolates was analysed by enterobacterial repetitive intergenic consensus (ERIC)-PCR, multilocus sequence typing (MLST) and multiplex PCR. RESULTS: A total of 122 isolates were confirmed as A. baumannii; all were resistant to the tested antibiotics except for tigecycline and colistin. The CarbAcineto NP test showed that 93.4% of the isolates produced a carbapenemase. blaOXA-23-like and extended-spectrum ß-lactamase-encoding genes were found by PCR in 94.3% and 91.8% of the isolates, respectively. Furthermore, the genetic environment of blaOXA-23-like was mainly associated with transposons Tn2008 (46.1%), Tn2006 (27.0%) and Tn2009 (20.9%). MLST identified six existing sequence types (STs) and three novel STs, of which ST195 (35.7%) and ST208 (32.1%) were the most common, belonging to clonal group 92 and European clone II. CONCLUSION: This study suggests that co-production of ß-lactamases was the major resistance mechanism of CRAB isolates. Dissemination of blaOXA-23-like may be facilitated by transposable elements. ST195 and ST208 were the predominant epidemic types of A. baumannii in Guangdong Province.

None of polymorphism of ovine fecundity major genes FecB and FecX was tested in goat.

The polymorphism of mutation Q249R in BMPR-IB gene (FecB) and loci FecX(I), FecX(H), FecX(G), FecX(B) in BMP15 gene was analyzed by forced PCR-RFLP method in 550 individuals from 6 flocks or breeds of goats with litter size varied from 1.4 to 2.7 including Boer (209), Haimen (128), second generation of Boer goat crossed with Huanghuai goat (82), Huanghuai (71), Nubi (37) and Matou (23) goat. None of mutations was detected in these goat breeds and their crossbreed. These results suggest that fecundity of goat is not linked to the same loci in BMPR-IB and BMP15 as sheep. Therefore, it is necessary to seek for other genes or loci in order to develop marker assistance selection techniques and study the prolific mechanism of the goat.

[Relationship between genetic diversity of chromosome 6 determined by microsatellite markers and litter size in Hu sheep].

Genetic diversity and relationship with litter size were analyzed in Hu sheep using 6 microsatellite markers LSCV043, BMS2508, GC101, 300U, Bulge5, and 471U, which were closely linked to FecB gene. Thirty-four alleles and 53 genotypes were detected at 6 microsatellite loci, which were all polymorphic. Three markers LSCV043, BMS2508 and 300 U were highly polymorphic loci. The polymorphism information content (PIC) were 0.6674, 0.6035, and 0.5615, respectively. The total mean of litter size of genotype LSCV043 107 bp/123 bp was significantly higher than that of genotype 110 bp/123 bp. The litter size of the first lambing for genotypes BMS2508 154 bp/154 bp, 154 bp/170 bp and 154 bp/200 bp were significantly higher than that of genotype 170 bp/170 bp (P<0.05). Furthermore, total litter size for BMS2508 170 bp/170 bp was the lowest in all the genotypes within this locus (P<0.05). No significant difference was detected in other genotypes.

Polymorphism of FecB gene in nine sheep breeds or strains and its effects on litter size, lamb growth and development.

Nine sheep breeds or strains, including 615 individuals were screened with forced PCR RFLP method for the FecB gene to study the polymorphism and its effects on litter size, body weight and body size. Results showed that the polymorphism frequencies of FecB gene were significantly imbalanced in these breeds or strains. The Hu sheep were all homozygous carriers of FecB gene(BB). In the Chinese Merino prolific meat strain, the genotype frequencies of BB, B+ and ++ were 51%, 30% and 19%, respectively, whereas all the other flocks had only the wild-type (++) genotype. Results within the Chinese Merino prolific meat strain showed that the mean litter size of ewes with genotype BB and B+ were 2.8 (+/-0.74) and 2.3 (+/- 0.63) (P < 0.05), whereas ++ genotype ewes had a litter size of only 1.2 (+/-0.68) (P < 0.01). At day 90 after birth, the body weights of BB/B+ genotype lambs were higher than that of ++ genotype lambs (18.6 +/- 3.70 kg, 18.0 +/- 3.71 kg vs 15.6 +/- 2.22 kg, P < 0.05). In addition, the heart girth and chest width of BB/B+ genotype lambs were significantly longer than those of the ++ lambs (P < 0.05). No significant differences were observed in either body weight or body size at day 120. Litter size at first lambing from Hu at Natural Source Conservative Region was found to be significantly higher than that from the other two regions sampled (P < 0.05). In addition to the additive effect on litter size, these findings showed for the first time that the FecB gene had a positive effect on early postnatal body growth.