Prevalence and molecular characteristics of ceftazidime-avibactam resistance among carbapenem-resistant Pseudomonas aeruginosa clinical isolates.

OBJECTIVES: Resistance against ceftazidime-avibactam (CZA) in carbapenem-resistant Pseudomonas aeruginosa (CRPA) is emerging. This study was aimed at detecting the prevalence and molecular characteristics of CZA-resistant CRPA clinical isolates in Guangdong Province, China. METHODS: The antimicrobial susceptibility profile of these strains was determined. A subset of 16 CZA-resistant CRPA isolates was analysed by whole-genome sequencing (WGS). Genetic surroundings of carbapenem resistance genes and pan-genome-wide association analysis were further studied. RESULTS: Of the 250 CRPA isolates, CZA resistance rate was 6.4% (16/250). The minimum inhibitory concentration (MIC) of CZA range was from 0.25 to >256 mg/L. MIC50 and MIC90 were 2/4 and 8/4 mg/L, respectively. Among the 16 CZA-resistant CRPA strains, 31.3% (5/16) of them carried class B carbapenem resistance genes, including blaIMP-4, blaIMP-45, and blaVIM-2, located on IncP-2 megaplasmids or chromosomes, respectively. Pan-genome-wide association analysis of accessory genes for CZA-susceptible or -resistant CRPA isolates showed that PA1874, a hypothetical protein containing BapA prefix-like domain, was enriched in CZA-resistant group significantly. CONCLUSIONS: Class B carbapenem resistance genes play important roles in CZA resistance. Meanwhile, the PA1874 gene may be a novel mechanism involving in CZA resistance. It is necessary to continually monitor CZA-resistant CRPA isolates.

Dynamic evolution of ceftazidime-avibactam resistance due to interchanges between blaKPC-2 and blaKPC-145 during treatment of Klebsiella pneumoniae infection.

Background: The emergence of ceftazidime-avibactam (CZA) resistance among carbapenem-resistant Klebsiella pneumoniae (CRKP) is of major concern due to limited therapeutic options. Methods: In this study, 10 CRKP strains were isolated from different samples of a patient with CRKP infection receiving CZA treatment. Whole-genome sequencing (WGS) and conjugation experiments were performed to determine the transferability of the carbapenem resistance gene. Results: This infection began with a KPC-2-producing K. pneumoniae (CZA MIC = 2 µg/mL, imipenem MIC ≥ 16 µg/mL). After 20 days of CZA treatment, the strains switched to the amino acid substitution of T263A caused by a novel KPC-producing gene, blaKPC-145, which restored carbapenem susceptibility but showed CZA resistance (CZA MIC ≥ 256 µg/mL, imipenem MIC = 1 µg/mL). The blaKPC-145 gene was located on a 148,185-bp untransformable IncFII-type plasmid. The subsequent use of carbapenem against KPC-145-producing K. pneumoniae infection led to a reversion of KPC-2 production (CZA MIC = 2 µg/mL, imipenem MIC ≥ 16 µg/mL). WGS analysis showed that all isolates belonged to ST11-KL47, and the number of SNPs was 14. This implied that these blaKPC-positive K. pneumoniae isolates might originate from a single clone and have been colonized for a long time during the 120-day treatment period. Conclusion: This is the first report of CZA resistance caused by blaKPC-145, which emerged during the treatment with CZA against blaKPC-2-positive K. pneumoniae-associated infection in China. These findings indicated that routine testing for antibiotic susceptibility and carbapenemase genotype is essential during CZA treatment.

EBV-Upregulated B7-H3 Inhibits NK cell-Mediated Antitumor Function and Contributes to Nasopharyngeal Carcinoma Progression.

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated epithelial malignancy characterized by the presence of prominent infiltration of lymphocytes, including natural killer (NK) cells. Although NK cells can directly target EBV-infected tumor cells without restriction by the MHC, EBV-positive (EBV+) NPC cells often develop resistance mechanisms that allow them to evade immune surveillance by NK cells. Elucidating the mechanisms involved in EBV-induced NK-cell dysfunction will contribute to the design of novel NK cell-based immunotherapies to treat NPC. Herein, we confirmed that the cytotoxic function of NK cells was impaired in EBV+ NPC tissues and found that EBV infection-induced expression of B7-H3 in NPC negatively correlated with NK-cell function. The inhibitory effect of EBV+ tumor expression of B7-H3 on NK-cell function was clarified in vitro and in vivo. Mechanistically, activation of the PI3K/AKT/mTOR signaling pathway via EBV latent membrane protein 1 (LMP1) was responsible for EBV infection-induced upregulation of B7-H3 expression. In an NPC xenograft mouse model with adoptive transfer of primary NK cells, deletion of B7-H3 on tumor cells in combination with anti-PD-L1 treatment restored NK cell-mediated antitumor activity and significantly improved the antitumor efficacy of NK cells. On the basis of our findings, we conclude that EBV infection can inhibit NK cell-mediated antitumor function by inducing upregulation of B7-H3 expression and provide a rationale for NK cell-based immunotherapies in combination of PD-L1 blockade and overcoming the immunosuppression of B7-H3 to treat EBV-associated NPC.

Risk factors and mortality for elderly patients with bloodstream infection of carbapenem resistance Klebsiella pneumoniae: a 10-year longitudinal study.

BACKGROUND: Bloodstream infection (BSI) caused by carbapenem resistant Klebsiella pneumoniae (CRKP), especially in elderly patients, results in higher morbidity and mortality. The purpose of this study was to assess risk factors associated with CRKP BSI and short-term mortality among elderly patients in China. METHODS: In this retrospective cohort study, we enrolled 252 inpatients aged ≥ 65 years with BSI caused by KP from January 2011 to December 2020 in China. Data regarding demographic, microbiological characteristics, and clinical outcome were collected. RESULT: Among the 252 BSI patients, there were 29 patients (11.5%) caused by CRKP and 223 patients (88.5%) by carbapenem-susceptible KP (CSKP). The overall 28-day mortality rate of elderly patients with a KP BSI episode was 10.7% (27/252), of which CRKP BSI patients (14 / 29, 48.3%) were significantly higher than CSKP patients (13 / 223, 5.83%) (P < 0.001). Hypertension (OR: 13.789, [95% CI: 3.883-48.969], P < 0.001), exposure to carbapenems (OR: 8.073, [95% CI: 2.066-31.537], P = 0.003), and ICU stay (OR: 11.180, [95% CI: 2.663-46.933], P = 0.001) were found to be associated with the development of CRKP BSI in elderly patients. A multivariate analysis showed that isolation of CRKP (OR 2.881, 95% CI 1.228-6.756, P = 0.015) and KP isolated in ICU (OR 11.731, 95% CI 4.226-32.563, P < 0.001) were independent risk factors for 28-day mortality of KP BSI. CONCLUSION: In elderly patients, hypertension, exposure to carbapenems and ICU stay were associated with the development of CRKP BSI. Active screening of CRKP for the high-risk populations, especially elderly patients, is significant for early detection and successful management of CRKP infection.

EBV Infection in Epithelial Malignancies Induces Resistance to Antitumor Natural Killer Cells via F3-Mediated Platelet Aggregation.

Nasopharyngeal carcinoma (NPC) and Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) are two major EBV-associated epithelial malignancies, both of which are characterized by the infiltration of a large number of lymphocytes, including natural killer (NK) cells. Although NK cells can prevent the development of EBV-associated epithelial malignancies, EBV-infected tumor cells often develop resistance to surveillance by NK cells. Elucidating the interactions between NK cells and EBV-infected tumor cells will facilitate the development of more effective NK-mediated therapies for treating EBV-associated malignancies. Here we investigated the cytotoxic function of NK cells in EBV-associated epithelial malignancies and discovered that EBV infection-induced upregulation of F3 expression correlates with NK-cell dysfunction in NPC and EBVaGC. The subsequent inhibitory effect of F3-mediated platelet aggregation on NK-cell function was verified in vitro and in vivo. Mechanistically, EBV latent membrane protein 2A (LMP2A) mediated upregulation of F3 through the PI3K/AKT signaling pathway. In an NPC xenograft mouse model, inhibition of F3 restored the antitumor function of NK cells and showed therapeutic efficacy when administered with NK-cell transfer. On the basis of these findings, EBV infection induces F3-mediated platelet aggregation that inhibits the antitumor function of NK cells, providing a rationale for developing and combining NK-cell-based therapies with F3 inhibitors to treat EBV-associated epithelial malignancies. SIGNIFICANCE: This study reveals a mechanism by which EBV-associated epithelial malignancies escape NK-cell-mediated immune surveillance, providing a new target for improving NK-cell immunotherapy.

Identification and Antifungal Susceptibility Analysis of Stephanoascus ciferrii Complex Species Isolated From Patients With Chronic Suppurative Otitis Media.

BACKGROUND: Stephanoascus ciferrii is a heterothallic ascomycetous yeast-like fungus. Recently, the concept of S. ciferrii complex has been proposed and it consists of S. ciferrii, Candida allociferrii, and Candida mucifera. We aimed to identify 32 strains of S. ciferrii complex isolated from patients with chronic suppurative otitis media (CSOM) at the species level and analyze the morphology and antifungal susceptibility profiles of the three species. METHOD: The sequencing of the internal transcribed spacer (ITS) region and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were used to identify S. ciferrii complex species. The SARAMIS software was used for cluster analysis of the mass spectra. All the strains were cultured on Sabouraud dextrose agar (SDA) and CHROM plates for 7 days. In the meantime, colonies of the 32 strains went through Gram staining. The Sensititre YeastOne YO10 colorimetric panel was used for the antifungal susceptibility analysis. RESULTS: There were 10 strains of C. allociferrii (31.25%), six strains of C. mucifera (18.75%), and 16 strains of S. ciferrii (50%) in the 32 strains of S. ciferrii complex according to the sequencing of the ITS region. MALDI-TOF MS could identify S. ciferrii but showed no results for C. allociferrii and C. mucifera. The cluster analysis of the mass spectra by SARAMIS indicated that the MALDI-TOF MS could distinguish the three species. The morphology characteristics of the three species were similar. As for antifungal susceptibility, S. ciferrii and C. mucifera tended to have high fluconazole MICs compared with C. allociferrii. C. mucifera and C. allociferrii had relatively low flucytosine MICs while S. ciferrii owned high flucytosine MICs. Besides, C. mucifera tended to have a higher MIC value than S. ciferrii for amphotericin B and C. allociferrii for anidulafungin, micafungin, and caspofungin. CONCLUSION: The antifungal susceptibility profiles of the three species of S. ciferrii complex had their own characteristics. Besides, more mass spectra of C. allociferrii and C. mucifera are needed to construct the reference database for S. ciferrii complex species, enabling MALDI-TOF MS to identify S. ciferrii complex at species level.

Chronic suppurative otitis media due to Streptomyces cacaoi, the second case report in human infection.

BACKGROUND: Streptomyces cacaoi, Gram-positive, branched, filamentous bacillus forms without fragmentation, are saprophytic soil organisms rarely known to cause invasive infections other than mycetoma. Here we describe a case of chronic suppurative otitis media caused by Streptomyces cacaoi in a patient with hyperlipidemia in China. CASE PRESENTATION: A 62-year-old female patient with hyperlipidemia suffered chronic suppurative otitis media caused by Streptomyces cacaoi. She had a favorable outcome with a 4-week course of ofloxacin ear drops. CONCLUSIONS: Streptomyces cacaoi is rarely reported to cause human infection. The introduction of molecular techniques improves the ability to identify rare species such as Streptomyces considerably. We report the case improve our ability to identify this pathogen and expand the range of known bacterial causes of human infection.

Serum levels of apolipoprotein E correlates with disease progression and poor prognosis in breast cancer.

ApoE has been reported to be associated with tumorigenesis and tumor progression. In this study, we explored the potential diagnostic and prognostic role of serum ApoE in breast cancer patients. Subject cohorts consisted of 152 normal healthy controls female and 257 breast cancer cases. Serum levels of ApoE were determined with turbidimetric immunoassay. The serum levels of ApoE were significantly elevated in breast cancer patients compared with normal healthy controls (45.82 ± 13.96 mg/L vs. 33.61 ± 6.44 mg/L, respectively, P < 0.0001) and also significantly associated with TNM stage and lymph nodes status (all P < 0.05). Area under receiver operating characteristic curve for serum ApoE discriminate breast cancer patients from controls was 0.786 with specificity of 0.974 and sensitivity of 0.541, the cut-off value of ApoE was 43.15 mg/L. Kaplan-Meier log rank analysis showed that the high serum ApoE group (serum ApoE ≥ 43.15 mg/L) had a poorer progression-free survival and overall survival compared with low serum ApoE group (serum ApoE < 43.15 mg/L) (all P < 0.05). In addition, univariate and multivariate Cox regression analysis displayed serum ApoE as an independent risk factor of breast cancer patients prognosis (all P < 0.05). Serum ApoE played a role as serological biomarkers that indicated diagnostic and prognostic evaluation in breast cancer patients.