Accurate and timely diagnosis of severe acute respiratory syndrome coronavirus (SARS-CoV) infection is a critical step in preventing another global outbreak. In this study, 829 serum specimens were collected from 643 patients initially reported to be infected with SARS-CoV. The sera were tested for the N protein of SARS-CoV by using an antigen capture enzyme-linked immunosorbent assay (ELISA) based on monoclonal antibodies against the N protein of SARS-CoV and compared to 197 control serum samples from healthy donors and non-SARS febrile patients. The results of the N protein detection analysis were directly related to the serological analysis data. From 27 SARS patients who tested positive with the neutralization test, 100% of the 24 sera collected from 1 to 10 days after the onset of symptoms were positive for the N protein. N protein was not detected beyond day 11 in this group. The positive rates of N protein for sera collected at 1 to 5, 6 to 10, 11 to 15, and 16 to 20 days after the onset of symptoms for 414 samples from 298 serologically confirmed patients were 92.9, 69.8, 36.4, and 21.1%, respectively. For 294 sera from 248 serological test-negative patients, the rates were 25.6, 16.7, 9.3, and 0%, respectively. The N protein was not detected in 66 patients with cases of what was initially suspected to be SARS but serologically proven to be negative for SARS and in 197 serum samples from healthy donors and non-SARS febrile patients. The specificity of the assay was 100%. Furthermore, of 16 sera collected from four patients during the SARS recurrence in Guangzhou, 5 sera collected from 7 to 9 days after the onset of symptoms were positive for the N protein. N protein detection exhibited a high positive rate, 96 to 100%, between day 3 and day 5 after the onset of symptoms for 27 neutralization test-positive SARS patients and 298 serologically confirmed patients. The N protein detection rate continually decreased beginning with day 10, and N protein was not detected beyond day 19 after the onset of symptoms. In conclusion, an antigen capture ELISA reveals a high N protein detection rate in acute-phase sera of patients with SARS, which makes it useful for early diagnosis of SARS.

In the face of the abundant production of various types of carbapenemases, the antibacterial efficiency of imipenem, seen as “the last line of defense”, is weakening. Following, the incidence of carbapenem-resistant Acinetobacter baumannii (CRAB), which can generate antibiotic-resistant biofilms, is increasing. Based on the superior antimicrobial activity of silver nanoparticles against multifarious bacterial strains compared with common antibiotics, we constructed the IPM@AgNPs-PEG-NOTA nanocomposite (silver nanoparticles were coated with SH-PEG-NOTA as well as loaded by imipenem) whose core was a silver nanoparticle to address the current challenge, and IPM@AgNPs-PEG-NOTA was able to function as a novel smart pH-sensitive nanodrug system. Synergistic bactericidal effects of silver nanoparticles and imipenem as well as drug-resistance reversal via protection of the β-ring of carbapenem due to AgNPs-PEG-NOTA were observed; thus, this nanocomposite confers multiple advantages for efficient antibacterial activity. Additionally, IPM@AgNPs-PEG-NOTA not only offers immune regulation and accelerates tissue repair to improve therapeutic efficacy in vivo but also can prevent the interaction of pathogens and hosts. Compared with free imipenem or silver nanoparticles, this platform significantly enhanced antibacterial efficiency while increasing reactive oxygen species (ROS) production and membrane damage, as well as affecting cell wall formation and metabolic pathways. According to the results of crystal violet staining, LIVE/DEAD backlight bacterial viability staining, and real-time quantitative polymerase chain reaction (RT-qPCR), this silver nanocomposite downregulated the levels of ompA expression to prevent formation of biofilms. In summary, this research demonstrated that the IPM@AgNPs-PEG-NOTA nanocomposite is a promising antibacterial agent of security, pH sensitivity, and high efficiency in reversing resistance and synergistically combatting carbapenem-resistant A. baumannii. In the future, various embellishments and selected loads for silver nanoparticles will be the focus of research in the domains of medicine and nanotechnology.

Cronobacter sakazakii, Bacillus cereus, and Salmonella spp. are common food-borne pathogens. The aim of this study was to develop a sensitive, specific, and rapid method for the simultaneous detection of these 3 pathogens in milk and milk products. Three specific primers were designed based on ompA, invA, and cesB of C. sakazakii, Salmonella spp. and B. cereus, respectively, for use in a multiplex PCR (mPCR). To eliminate false-positive results, cells were pretreated with propidium monoazide (PMA) for the selective elimination of the genomic DNA of dead cells. An internal amplification control was applied as an indicator of false-negative results from the interference of inhibitors in the food matrix. Results showed that, in pure culture, the limits of detection of the assay for C. sakazakii, Salmonella Enteritidis, and B. cereus were 9.5 × 10, 7.4 × 10, and 7.5 × 10 cfu/mL, respectively. Moreover, 8 cfu/mL of viable B. cereus cells were detected after 5 h of enrichment, and 9 cfu/mL of viable C. sakazakii and 7 cfu/mL of Salmonella Enteritidis were detected after 7 h of enrichment in spiked pure milk, walnut peanut milk, and whole-wheat milk. To validate the PMA-mPCR assay, the PMA-mPCR assay and the traditional culture method were performed to detect the 3 bacterial strains in 1,165 milk product samples. The PMA-mPCR assay obtained the same results as the culture-based method. Results demonstrated that the PMA-mPCR assay has excellent sensitivity and specificity for the simultaneous detection of viable C. sakazakii, Salmonella Enteritidis, and B. cereus in milk and milk products.

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