Retrospective analysis of molecular characteristics, risk factors, and outcomes in carbapenem-resistant Klebsiella pneumoniae bloodstream infections.

BACKGROUND: Klebsiella pneumoniae (KP) is the second most prevalent Gram-negative bacterium causing bloodstream infections (BSIs). In recent years, the management of BSIs caused by KP has become increasingly complex due to the emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP). Although numerous studies have explored the risk factors for the development of CRKP-BSIs, the mortality of patients with KP-BSIs, and the molecular epidemiological characteristics of CRKP, the variability in data across different populations, countries, and hospitals has led to inconsistent conclusions. In this single-center retrospective observational study, we utilized logistic regression analyses to identify independent risk factors for CRKP-BSIs and factors associated with mortality in KP-BSI patients. Furthermore, a risk factor-based prediction model was developed. CRKP isolates underwent whole-genome sequencing (WGS), followed by an evaluation of microbiological characteristics, including antimicrobial resistance and virulence genes, as well as epidemiological characteristics and phylogenetic analysis. RESULTS: Our study included a total of 134 patients with KP-BSIs, comprising 50 individuals infected with CRKP and 84 with carbapenem-susceptible Klebsiella pneumoniae (CSKP). The independent risk factors for CRKP-BSIs were identified as gastric catheterization (OR = 9.143; CI = 1.357-61.618; P = 0.023), prior ICU hospitalization (OR = 4.642; CI = 1.312-16.422; P = 0.017), and detection of CRKP in non-blood sites (OR = 8.112; CI = 2.130-30.894; P = 0.002). Multivariate analysis revealed that microbiologic eradication after 6 days (OR = 3.569; CI = 1.119-11.387; P = 0.032), high Pitt bacteremia score (OR = 1.609; CI = 1.226-2.111; P = 0.001), and inappropriate empirical treatment after BSIs (OR = 6.756; CI = 1.922-23.753; P = 0.003) were independent risk factors for the 28-day mortality in KP-BSIs. The prediction model confirmed that microbiologic eradication after 6.5 days and a Pitt bacteremia score of 4.5 or higher were significant predictors of the 28-day mortality. Bioinformatics analysis identified ST11 as the predominant CRKP sequence type, with blaKPC-2 as the most prevalent gene variant. CRKP stains carried multiple plasmid-mediated resistance genes along with some virulence genes. Phylogenetic analysis indicated the presence of nosocomial transmission of ST11 CRKP within the ICU. CONCLUSIONS: The analysis of risk factors for developing CRKP-BSIs and the association between KP-BSIs and 28-day mortality, along with the development of a risk factor-based prediction model and the characterization of CRKP strains, enhances clinicians' understanding of the pathogens responsible for BSIs. This understanding may help in the timely administration of antibiotic therapy for patients with suspected KP-BSIs, potentially improving outcomes.

Progress in the Study of Epidemiologic Characteristics and Influencing Factors of Asymptomatic Malaria Infection in Africa.

Malaria is caused by protozoan parasitic Plasmodium infections. Plasmodium falciparum is common in Africa; P ovale, P malaria and P vivax infections are less prevalent and globally confined, contributing to major causes of global mortality and morbidity, particularly in children in sub-Saharan African countries. In 2018, the total incidence of malaria increased from 221 million to 229 million, with an estimated 503 000 deaths reported. Sub-Saharan Africa has the highest number of cases of malaria and highest mortality rate compared with other countries, like southeastern Asia, east Pacific, western, and America with an estimated 213 million cases. In addition, continuous exposure to Plasmodium parasites results in the production of partial immunity to guard against more problems, resulting in asymptomatic carriers. The diagnosis of asymptomatic malaria is not simple because of the apparent absence of clinical factors and sometimes low levels of parasites. The most basic concept appears to be parasitemia and a lack of malaria signs, primarily fever (axillary temperature <37.5° C). Thus, a better awareness of asymptomatic malaria epidemiology in affected countries will help improve strategies to reduce the local burden of malaria and its health consequences. Therefore, the objective of this study was to determine the magnitude of asymptomatic malaria pathology and related risk factors with epidemiologic characteristics in individuals on the African continent.

Nocardia Infection in Nephrotic Syndrome Patients: Three Case Studies and A Systematic Literature Review.

OBJECTIVE: The multicenter literature review and case studies of 3 patients were undertaken to provide an updated understanding of nocardiosis, an opportunistic bacterial infection affecting immunosuppressed nephrotic syndrome (NS) patients receiving long-term glucocorticoid and immunosuppressant treatment. The results provided clinical and microbiological data to assist physicians in managing nocardiosis patients. METHODS: Three cases between 2017 and 2018 from a single center were reported. Additionally, a systematic review of multicenter cases described in the NCBI PubMed, Web of Science, and Embase in English between January 1, 2001 and May 10, 2021 was conducted. RESULTS: This study described three cases of Nocardia infection in NS patients. The systematic literature review identified 24 cases with sufficient individual patient data. A total of 27 cases extracted from the literature review showed that most patients were > 50 years of age and 70.4% were male. Furthermore, the glucocorticoid or corticosteroid mean dose was 30.9 ± 13.7 mg per day. The average time between hormone therapy and Nocardia infection was 8.5 ± 9.7 months. Pulmonary (85.2%) and skin (44.4%) infections were the most common manifestations in NS patients, with disseminated infections in 77.8% of patients. Nodule/masses and consolidations were the major radiological manifestations. Most patients showed elevated inflammatory biomarkers levels, including white blood cell counts, neutrophils percentage, and C-reactive protein. Twenty-five patients received trimethoprim-sulfamethoxazole monotherapy (18.5%) or trimethoprim-sulfamethoxazole-based multidrug therapy (74.1%), and the remaining two patients (7.4%) received biapenem monotherapy. All patients, except the two who were lost to follow-up, survived without relapse after antibiotic therapy. CONCLUSIONS: Nephrotic syndrome patients are at high risk of Nocardia infection even if receiving low-dose glucocorticoid during the maintenance therapy. The most common manifestations of nocardiosis in NS patients include abnormal lungs revealing nodules and consolidations, skin and subcutaneous abscesses. The NS patients have a high rate of disseminated and cutaneous infections but a low mortality rate. Accurate and prompt microbiological diagnosis is critical for early treatment, besides the combination of appropriate antibiotic therapy and surgical drainage when needed for an improved prognosis.

PCR-detectable Candida DNA exists a short period in the blood of systemic candidiasis murine model.

Invasive candidiasis is a major challenge to clinical medicine today. However, traditional fungal diagnostic techniques and empirical treatments have shown great limitations. Although efforts are necessarily needed in methodology standardization and multicenter validation, polymerase chain reaction (PCR) is a very promising assay in detecting fungal pathogens. Using a "heat-shock" DNA preparation method, a rapid and simple PCR protocol for quantification of the Candida albicans (C. albicans) ribosomal DNA was established. The PCR assay could detect Candida DNA as low as 10 CFU/mL in samples prepared by the heat-shock protocol, without any cross-reaction with DNA prepared from other Candida spp. and bacterial pathogens. For simulated blood samples, the PCR test sensitivity of whole blood samples was better than that of plasma and blood cells. In the systemic candidiasis murine model, detectable DNA was only observed within 24 h after C. albicans SC5314 injection, which is much shorter than that observed in the kidney.

[Analysis of prevention of mother-to-child transmission of HIV (PMTCT) work in Zhumadian city, 2001 - 2009].

OBJECTIVE: To analyze the current status of maternal HIV infection, mother to child transmission, and the work accomplishments in preventing mother-to-child transmission of HIV (PMTCT). METHODS: During October, 2001 to May, 2009, HIV voluntary consultation and examination were carried out in 339 866 pregnant women in the urban areas, while 594 pregnant women who tested positive were intervened, and interventions were also conducted among 326 babies who were born to HIV positive mothers, including HIV immune body examination on the babies when they were 12 months and 18 months old. RESULTS: A total of 594 pregnant women were found HIV positive, with the positive rate of 0.17% (594/339 866). And the rate was declining year by year. The highest rate was 0.47% (37/7837) in 2002, and the lowest rate was 0.12% (86/73 343) in 2008. Of the 594 positive pregnant women, 228 (38.38%) terminated pregnancy voluntarily, 43 (7.24%) kept on pregnancy and 317 (53.37%) parturients. Of 326 babies born by the 317 parturients, 317 survived.298 received curbing intervention for mother to child transmission (PMTCT), the ratio was 94.01% (298/317). Of 224 babies who were 18 months old, 221 accepted examination, and 7 HIV positive. The maternal infant transmission rate after intervention was 3.17% (7/221). CONCLUSION: Through the prevention of mother-to-child transmission of HIV, the HIV infection status in the pregnant women can be timely observed, which can effectively decrease the level of mother-to-child transmission of HIV.

Development of a Lateral Flow Immunoassay for the Rapid Diagnosis of Invasive Candidiasis.

Early and accurate diagnosis of invasive candidiasis (IC) is very important. In this study, a lateral flow immunoassay (LFIA) was developed to detect antibody against Candida albicans enolase (Eno). Colloidal gold particle labeled mouse anti human IgG (1.0 mg/L) was used as the detector reagent. Recombinant enolase (rEno, 1.0 mg/L) and goat anti IgG (1.0 mg/L) were immobilized in test and control lines, respectively, of a nitrocellulose membrane, acting as the capture reagents. The LFIA was used to detect anti Eno in 38 sera from clinically proven IC patients, as well as in 50 healthy control subjects. Compared with an indirect ELISA designed as a reference test, the specificity and sensitivity of the LFIA were 98.2 and 84.8%, respectively. Excellent agreement between the results obtained by ELISA and the LFIA (κ = 0.851) was observed in this study. In addition, the agreement between the blood culture results and LFIA test is strong (κ = 0.658). The data presented in the study indicate that the LFIA test is a suitable tool for the serological surveillance of IC in the field or in poorly equipped laboratories.

PELA microspheres loaded H. pylori lysates and their mucosal immune response.

AIM: To prepare poly (D,L-lactide)-polyethylene glycol copolymer (PELA) microspheres loaded H.pylori lysates or Cystografin and observe their targeting in gastrointestinal mucous membrane or analyze the mucosal immune responses by oral administration. METHODS: PELA microspheres loaded H.pylori lysates or Cystografin were prepared by double emulsion evaporation method. Their distribution in gastrointestinal mucous membrane was observed by CT. Balb/c mice orally immunized in mucosal immune responses, whose antibody production in salivary and gut washing and antibody secreting cells in Peyer's patches (PP) were estimated by ELISA and ELISPOT, respectively. The microspheres physical properties, such as particle size, protein level and morphology were investigated. RESULTS: All prepared microspheres were found to have a smooth surface morphology from 3.20-4.05 microm in diameter and high encapsulation efficiency from 74.9-82.2 %. No significant correlation in their physical properties was shown, depending on their molecular weight at the similar composition ratio. Immunization with all types of PELA-Hp microspheres elevated the saliva sIgA level at week 3 by approximately 3-4 times that with soluble antigen, which was greatly enhanced after boosting. At one week after last immunization with all types of PELA-Hp microspheres (week 8), the specific sIgA-ASCs, IgG-ASCs and sIgA in salivary rose obviously. In intestinal Peyer's patches, the specific sIgA-ASCs were 5.92-6.98X10(4)/ml cell and IgG-ASCs were 3.47-4.02X10(4)/ml cell, about 5-9 times higher than those with soluble antigen (P<0.01). ASCs in intestine were more than those in stomach and the majority of the ASCs were sIgA-ASCs. The sIgA in gut washing fluid was 1.62-1.85 OD, about 3-6 times tthat of those with soluble antigen. There were significant differences of the ASCs and sIgA in gut washing fluid as compared with those of PBS and MS-0 (P<0.05). There appeared to be good correlation between sIgA level in gut washing fluid and sIgA-ASCs in intestinal Peyer's patches. CONCLUSION: PELA microspheres may be used as vehicle to delivery antigen and adjuvant in designing oral vaccination.

[Recombinant Helicobacter pylori urease B subunit and its biological properties].

OBJECTIVE: To perform genetic recombination of the urease B subunit (UreB) of Helicobacter pylori (Hp) and examine the biological properties of the recombinant protein. METHODS: The gene fragment encoding Hp UreB was isolated clinically from Chinese subjects by means of PCR, and cloned subsequently into an expression vector pET-11C-UreB for the non-fusion protein expression in E.coli BL21 (DE3) strain. RESULTS: The expression of recombinant UreB was achieved in E.coli BL21 with a relative molecular weight of approximately 62,000 at the expression ratio of 26%, and the first 15 amino acids of recombinant UreB were MKKISREYVSMYGP. The results of peptide mapping and amino acid compositional analysis were consistent with previous theoretical prediction, and enzyme-linked immunosorbent assay together with Western blotting indicated strong immunogenicity and reactivity of the recombinant protein in BalB/c mice, which were specifically recognized by polyclonal BalB/c mice anti-Hp sera or human sera infected with Hp. CONCLUSION: The results of this study has laid an solid immunological foundation for incorporating recombinant UreB as a subunit vaccine component against Hp.

Proteomic analysis of the Ehrlichia chaffeensis phagosome in cultured DH82 cells.

Ehrlichia chaffeensis is an obligately intracellular bacterium that resides and multiplies within cytoplasmic vacuoles of phagocytes. The Ehrlichia-containing vacuole (ECV) does not fuse with lysosomes, an essential condition for Ehrlichia to survive inside phagocytes, but the mechanism of inhibiting the fusion of the phagosome with lysosomes is not clear. Understanding the ECV molecular composition may decipher the mechanism by which Ehrlichia inhibits phagosome-lysosome fusion. In this study, we obtained highly purified ECVs from E. chaffeensis-infected DH82 cells by sucrose density gradient centrifugation and analyzed their composition by mass spectrometry-based proteomics. The ECV composition was compared with that of phagolysosomes containing latex beads. Lysosomal proteins such as cathepsin D, cathepsin S, and lysosomal acid phosphatase were not detected in E. chaffeensis phagosome preparations. Some small GTPases, involved in membrane dynamics and phagocytic trafficking, were detected in ECVs. A notable finding was that Rab7, a late endosomal marker, was consistently detected in E. chaffeensis phagosomes by mass spectrometry. Confocal microscopy confirmed that E. chaffeensis phagosomes contained Rab7 and were acidified at approximately pH 5.2, suggesting that the E. chaffeensis vacuole was an acidified late endosomal compartment. Our results also demonstrated by mass spectrometry and immunofluorescence analysis that Ehrlichia morulae were not associated with the autophagic pathway. Ehrlichia chaffeensis did not inhibit phagosomes containing latex beads from fusing with lysosomes in infected cells. We concluded that the E. chaffeensis vacuole was a late endosome and E. chaffeensis might inhibit phagosome-lysosome fusion by modifying its vacuolar membrane composition, rather than by regulating the expression of host genes involved in trafficking.