Molecular epidemiology and carbapenem resistance characteristics of Acinetobacter baumannii causing bloodstream infection from 2009 to 2018 in northwest China.

Bloodstream infection (BSI) caused by Acinetobacter baumannii poses a serious threat to health and is correlated with high mortality in patients with hospital-acquired infections, so the molecular epidemiology and antimicrobial resistance characteristics of this pathogen urgently need to be explored. A. baumannii isolates from BSI patients were collected in three tertiary hospitals in northwest China from 2009 to 2018. Antimicrobial susceptibility testing was used to determine the MICs of the A. baumannii isolates. Whole-genome sequencing based on the Illumina platform was performed for molecular epidemiological analyses and acquired resistance gene screening. The efflux pump phenotype was detected by examining the influence of an efflux pump inhibitor. The expression of efflux pump genes was evaluated by RT-PCR. In total, 47 A. baumannii isolates causing BSI were collected and they presented multidrug resistance, including resistance to carbapenems. Clone complex (CC) 92 was the most prevalent with 30 isolates, among which a cluster was observed in the phylogenetic tree based on the core genome multi-locus sequence type, indicating the dissemination of a dominant clone. BSI-related A. baumannii isolates normally harbour multiple resistance determinants, of which oxacillinase genes are most common. Except for the intrinsic bla OXA-51 family, there are some carbapenem-resistant determinants in these A. baumannii isolates, including bla OXA-23, which is encoded within the Tn2006, Tn2008 or Tn2009 transposon structures and bla OXA-72. The transfer of bla OXA-72 was suggested by XerC/D site-specific recombination. The AdeABC efflux pump system contributed to carbapenem resistance in A. baumannii isolates, as evidenced by the high expression of some of its encoding genes. Both the clone dissemination and carbapenem resistance mediated by oxacillinase or efflux pumps suggest an effective strategy for hospital infection control.

Corrigendum: Whole-genome sequencing provides insight into antimicrobial resistance and molecular characteristics of Salmonella from livestock meat and diarrhea patient in Hanzhong, China.

[This corrects the article DOI: 10.3389/fmicb.2022.899024.].

Whole-Genome Sequencing Provides Insight Into Antimicrobial Resistance and Molecular Characteristics of Salmonella From Livestock Meat and Diarrhea Patient in Hanzhong, China.

Salmonella is a major zoonotic pathogen, which usually contaminates food resulting in salmonellosis in humans. Exploring the characteristics and origins of Salmonella is essential in formulating prevention and control measures for Salmonella infection. We used slide agglutination, antimicrobial susceptibility testing, and whole-genome sequencing to analyze and compare Salmonella's phenotype, genotyping diversity, and genetic relatedness from livestock meat and diarrhea patients in Hanzhong, China, from 2018 to 2020. Totally 216 Salmonella enterica isolates were screened from frozen whole chicken carcasses (44.3%, 70/158), frozen raw ground pork (36.2%, 59/163), and diarrhea patients (4.4%, 87/1964). Salmonella Typhimurium was the dominant serotype. Notably, compared with other sources, isolates obtained from frozen whole chicken carcasses showed significant resistance to third-generation cephalosporin and fluoroquinolones (p < 0.05). All strains were assigned into 36 sequence types (STs) and two novel STs, and an excellent consistency was observed between ST and serotype. Genomic data revealed that extended-spectrum ß-lactamase genes were responsible for third-generation cephalosporin resistance in 52 Salmonella strains, and the most predominant resistance determinant was bla CTX-M. Furthermore, of the 60 ciprofloxacin-resistant isolates, five single-base mutations in quinolone resistance-determining regions were identified in gyrA or parC, and the plasmid-mediated quinolone resistance gene aac(6')Ib-cr was most often detected. The cgMLST clusters show that five clusters among four serotypes (including S. Typhimurium, S. London, S. Derby, and S. Agona) cover samples from diarrhea patients and livestock meat pathway isolate, indicating a possibility of cross-host transmission. In conclusion, the livestock meat isolates have a higher level of resistance than diarrhea patients' isolates and could be an essential source of human Salmonella infection.

Risk factors and outcomes of bloodstream infections caused by Acinetobacter baumannii: a case-control study.

The risk factors and outcomes of patients with bloodstream infections (BSIs) caused by Acinetobacter baumannii are major concerns in clinical therapy. Multicenter case-control studies were performed to compare the clinical characteristics of 47 A. baumannii BSI patients and 124 matched controls with nonbloodstream A. baumannii infections and the clinical and molecular characteristics of BSI survivors and nonsurvivors. Additionally, the mortality of BSIs was assessed. The clinical characteristics, including neutropenia, ICU admission prior to positive culture, primary infection in the central nervous system, and carbapenem use prior to positive culture, were independently associated with BSI caused by A. baumannii. The mortality of the BSI patients was significantly higher than that of the controls. A high Pitt bacteremia score was found to be an independent predictor of mortality in the BSI patients. The healthcare-associated factors, disease severity level, or antibiotic usage increased the risks of A. baumannii BSI and related mortality.

[Analysis of community-associated bloodstream infections caused by Escherichia coli producing extended-spectrum ß-lactamase].

OBJECTIVE: To compare the risk factors and resistance characterizations between the Community-associated (CA) and Hospital-associated (HA) bloodstream infections (BSIs) caused by extended-spectrum ß-lactamase-producing ESBLs) Escherichia coli. Infections control strategy must be made for the spread of CA E. Coli. METHODS: Fifty-one samples of ESBLs-producing BSI E. Coli were collected in 3201 hospital affiliated of Xi'an jiaotong University School of Medicine from 2008 to 2013. Antimicrobial agents susceptibility test and ESBLs confirmation test were determined by K-B method. PFGE was used to investigate the clonality of clinical isolates. PCR amplification and sequencing were used to screen ESBLs genes. Plasmid conjugation assay was used by filter mating. An S1-PFGE assay on plasmid and southern blot were performed to determine the plasmid molecular size and resistance genes location. RESULTS: There were 27 community-associated samples, while 24 hospital-associated samples in 51. And patients with community-acquired infections were increasing year by year. Also there was a significant difference between patients with urinary tract infection and cancer in CA and HA. Cases of urinary tract infection were mainly CA, reaching to 18. 40 of OR value, and from 2. 161 to 156. 7 of 95% confidence interval. While Cases of cancer gave priority to HA, OR value was 0. 147 7 with 0. 034 85 to 0. 626 30 of 95% confidence interval. PFGE results did not support the evidence of clone dissemination. Among 51 strains, 26 TEM genotype, including 12 CA strains, 12 SHV genotype, including 5 CA strains, 21 CTX-M-1 genotype, including 10 CA strains , and 25 CTX-M-9 genotype. including 13 CA strains. All ESBLs resistant genotypes were no significant differences in the two groups. Conclusions Urinary tract infection is risk factor for community-aassociated bloodstream infection caused by E. Coli relatively. Degree of drug resistance of ESBLs-producing E. Coli isolated from Community-Associated Bloodstream Infections is close to Hospital-Associated. So the public health control measures are needed to prevent the further spread of CA ESBLs-producing E. Coli. [Key words] Bloodstream infection; Risk factor; Resistance; Pulsed field gel electrophoresis; Plasmid