Pathogenetic detection, retrospective and pathogenicity analysis of a fatal case of Vibrio vulnificus in Shenzhen, China.

We report a 36-year-old male patient died of V. vulnificus-induced septicaemia and multiple organ failure syndrome after oyster consumption at a restaurant. We isolated and identified V. vulnificus vv16015 from the patient's blood sample and antibiotic susceptibility tests indicated sensitivity to all 21 antibiotics. Oyster samples were subsequently collected from the restaurant's supplier and three strains of V. vulnificus were isolated. Whole genome sequencing and analysis revealed vv16015 to be distantly related to these strains and confirmed that V. vulnificus contamination was present in the seafood of the restaurant and supplier. Using a Galleria mellonella larvae infection model, the virulence of vv16015 was determined to be higher than that of comparison strains isolated from a surviving patient (vv15018) and an oyster (vv220015). The human and environment distribution of V. vulnificus in Shenzhen is sporadic and heterogeneous, and vv16015 is highly virulent compared to other strains.

Distribution of drug-resistant genes in alveolar lavage fluid from patients with psittacosis and traceability analysis of causative organisms.

Background: Chlamydia psittaci is a small bacterium often found in birds, including poultry, and domesticated mammals, which causes psittacosis (or parrot fever) in humans. Different strains of C. psittaci respond variably to antibiotics, suggesting a possible risk of antibiotic resistance. In general, different genotypes of C. psittaci have relatively stable hosts and different pathogenicity. Methods: Macrogenomic sequencing was performed using nucleic acids extracted from psittacosis patients' alveolar lavage fluid samples and analyzed for genetic variability and antibiotic resistance genes. Nucleic acid amplification sequences specific to the core coding region of the C. psittaci ompA gene were used, and a phylogenetic tree was constructed with C. psittaci genotypic sequences from other sources, including Chinese published sources. The C. psittaci found in each patient were genotyped by comparing ompA gene sequences. In addition, to better illustrate the relationship between genotype and host of C. psittaci, 60 bird fecal samples were collected from bird-selling stores for screening and C. psittaci typing. Results: Macrogenomic sequence alignment revealed the presence of resistance genes in varying abundance in samples from all three patients, including C. psittaci resistance gene sequences from two patients that matched those previously published on NCBI. Based on ompA genotyping, two patients were infected with C. psittaci genotype A and one patient was infected with genotype B. All five C. psittaci-positive samples obtained from bird-selling stores were genotype A. Both genotypes are reported to be infectious to humans. The host origin of the samples and the previously reported main sources of each genotype suggested that all but one of the C. psittaci genotype A in this study were derived from parrots, while genotype B was probably derived from chickens. Conclusion: The presence of bacterial resistance genes in psittacosis patients may affect the efficacy of clinical antibiotic therapy. Focusing on the developmental progression of bacterial resistance genes and differences in the therapeutic efficacy may facilitate effective treatment of clinical bacterial infections. Pathogenicity genotypes (e.g., genotype A and genotype B) are not limited to one animal host, suggesting that monitoring the development and changes of C. psittaci may help prevent transmission to humans.

Epidemiological and genomic analyses of human isolates of Streptococcus suis between 2005 and 2021 in Shenzhen, China.

Streptococcus suis (S. suis) is an important food-borne zoonotic pathogen that causes swine streptococcosis, which threatens human health and brings economic loss to the swine industry. Three-quarters of human S. suis infections are caused by serotype 2. A retrospective analysis of human S. suis cases in Shenzhen, a megacity in China, with high pork consumption, between 2005 and 2021 was conducted to understand its genomic epidemiology, pathogen virulence, and drug resistance characteristics. The epidemiological investigation showed that human cases of S. suis in Shenzhen were mainly associated with people who had been in close contact with raw pork or other swine products. Whole-genome sequence analysis showed that 33 human isolates in Shenzhen were dominated by serotype 2 (75.76%), followed by serotype 14 (24.24%), and the most prevalent sequence types (STs) were ST7 (48.48%) and ST1 (39.40%). ST242 (9.09%) and ST25 (3.03%), which were rarely reported, were also found. Phylogenetic analysis showed that the Shenzhen human isolates had close genetic relatedness to isolates from Guangxi (China), Sichuan (China), and Vietnam. We found a new 82 KB pathogenicity island (PAI) in the serotype 2 isolate that may play a role in sepsis. Similarly, a serotype 14 isolate, containing 78 KB PAI, was isolated from a patient presenting with streptococcal toxic shock syndrome (STSLS) who subsequently died. Multi-drug resistance (MDR) was high in human isolates of S. suis from Shenzhen. Most human isolates were resistant to tetracycline, streptomycin, erythromycin, and clindamycin, and 13 isolates had intermediate resistance to penicillin. In conclusion, swine importation from Guangxi, Sichuan, and Vietnam should be more closely monitored, and the use of antibiotics limited to reduce the potential for antimicrobial resistance (AMR).

Pathogenetic characterization of a Micrococcus luteus strain isolated from an infant.

Purpose: To explore the clinical characteristics of Micrococcus luteus bloodstream infection in an infant and characterize the phenotype and genotype of the isolated strains, as well as seek suitable infection models for assessing virulence. Methods: Clinical data was collected from an infant patient diagnosed with M. luteus bloodstream infection. Metagenomic sequencing was performed on the isolated blood sample. The strain was isolated and underwent mass spectrometry, biochemical tests, antibiotic susceptibility assays, and whole-genome sequencing. The Galleria mellonella infection model was used to assess M. luteus virulence. Results: Patient responded poorly to cephalosporins, but recovered after Linezolid treatment. Metagenomic sequencing identified M. luteus as the predominant species in the sample, confirming infection. They were identified as M. luteus with a high confidence level of 98.99% using mass spectrometry. The strain showed positive results for Catalase, Oxidase, and Urea tests, and negative results for Mannose, Xylose, Lactose, Mannitol, Arginine, and Galactose tests, consistent with the biochemical profile of M. luteus reference standards. M. luteus susceptibility to 15 antibiotics was demonstrated and no resistance genes were detected. Predicted virulence genes, including clpB, were associated with metabolic pathways and the type VI secretion system. The infection model demonstrated dose-dependent survival rates. Conclusion: The infant likely developed a bloodstream infection with M. luteus due to compromised immunity. Although the isolated strain is sensitive to cephalosporin antibiotics and has low pathogenicity in infection models, clinical treatment with cephalosporins was ineffective. Linezolid proved to be effective, providing valuable guidance for future clinical management of such rare infections.