The emergence of antimicrobial-resistant bacteria is an increasingly serious threat to global health, necessitating the development of innovative antimicrobials. Here we report the development of a series of CRISPR-Cas13a-based antibacterial nucleocapsids, termed Cap-sidCas13a(s), capable of sequence-specific killing of carbapenem-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus by recognizing corresponding antimicrobial resistance genes. CapsidCas13a constructs are generated by packaging programmed CRISPR-Cas13a into a bacteriophage capsid to target antimicrobial resistance genes. Contrary to Cas9-based antimicrobials that lack bacterial killing capacity when the target genes are located on a plasmid, the CapsidCas13a(s) exhibit strong bacterial killing activities upon recognizing target genes regardless of their location. Moreover, we also demonstrate that the CapsidCas13a(s) can be applied to detect bacterial genes through gene-specific depletion of bacteria without employing nucleic acid manipulation and optical visualization devices. Our data underscore the potential of CapsidCas13a(s) as both therapeutic agents against antimicrobial-resistant bacteria and nonchemical agents for detection of bacterial genes.

We describe an outbreak of Bacillus cereus bacteremia that occurred at Jichi Medical University Hospital in 2006. This study aimed to identify the source of this outbreak and to implement appropriate control measures. We reviewed the charts of patients with blood cultures positive for B. cereus, and investigated B. cereus contamination within the hospital environment. Genetic relationships among B. cereus isolates were analyzed. Eleven patients developed B. cereus bacteremia between January and August 2006. The hospital linens and the washing machine were highly contaminated with B. cereus, which was also isolated from the intravenous fluid. All of the contaminated linens were autoclaved, the washing machine was cleaned with a detergent, and hand hygiene was promoted among the hospital staff. The number of patients per month that developed new B. cereus bacteremia rapidly decreased after implementing these measures. The source of this outbreak was B. cereus contamination of hospital linens, and B. cereus was transmitted from the linens to patients via catheter infection. Our findings demonstrated that bacterial contamination of hospital linens can cause nosocomial bacteremia. Thus, blood cultures that are positive for B. cereus should not be regarded as false positives in the clinical setting.

Bacillus cereus (B. cereus) is a pathogen in opportunistic infections. Here we show that Bacillus cereus sphingomyelinase (Bc-SMase) is a virulence factor for septicemia. Clinical isolates produced large amounts of Bc-SMase, grew in vivo, and caused death among mice, but ATCC strains isolated from soil did not. A transformant of the ATCC strain carrying a recombinant plasmid containing the Bc-SMase gene grew in vivo, but that with the gene for E53A, which has little enzymatic activity, did not. Administration of an anti-Bc-SMase antibody and immunization against Bc-SMase prevented death caused by the clinical isolates, showing that Bc-SMase plays an important role in the diseases caused by B. cereus. Treatment of mouse macrophages with Bc-SMase resulted in a reduction in the generation of H2O2 and phagocytosis of macrophages induced by peptidoglycan (PGN), but no effect on the release of TNF-α and little release of LDH under our experimental conditions. Confocal laser microscopy showed that the treatment of mouse macrophages with Bc-SMase resulted in the formation of ceramide-rich domains. A photobleaching analysis suggested that the cells treated with Bc-SMase exhibited a reduction in membrane fluidity. The results suggest that Bc-SMase is essential for the hydrolysis of SM in membranes, leading to a reduction in phagocytosis.

ImportanceGlobal studies have reported that the incidence of Kawasaki disease (KD) declined during the COVID-19 pandemic. These studies suggest that the global pandemic and its accompanying mitigation measures may provide an important opportunity to explore the hypothesis of a KD pathogenesis.ObjectiveTo compare changes in KD incidence in Japan before and after the start of the COVID-19 pandemic.Design, Setting, and ParticipantsThis cohort study was conducted using the data set from Japan’s 26th nationwide KD survey that obtained information on patients who were diagnosed with KD in Japan from January 1, 2019, through December 31, 2020.Main Outcomes and MeasuresKawasaki disease incidence rates were calculated by referring to the national population data in the vital statistics data for Japan.ResultsA total of 28 520 patients were identified (16 236 male individuals [56.9%]; median [IQR] age, 26 [14-44] months). A total of 17 347 patients were diagnosed with KD in 2019 and 11 173 were diagnosed in 2020, representing a 35.6% reduction in the number of patients diagnosed in 2020 compared with the previous year. Patient distributions for days of illness at the first hospital visit were almost identical in 2019 and 2020, suggesting that the decrease in KD incidence likely was not associated with pandemic-related delays in seeking treatment. The proportion of patients diagnosed with KD who were younger than 12 months was significantly larger in 2020 than in 2019 (21.6% vs 19.4%; P < .001). Compared with KD incidence among younger patients, the incidence among those 24 months and older declined rapidly after initiation of COVID-19 special mitigation measures, with a greater percentage reduction (58.3% reduction in July), but rebounded faster after the end of the special mitigation period. By contrast, the incidence among patients younger than 12 months declined moderately after the initiation of the special mitigation period, with a lower percentage reduction (40.3% reduction in October), and rebounded at a later phase.Conclusions and RelevanceIn this cohort study, the number of patients diagnosed with KD decreased by approximately one-third across Japan in 2020, with no indication that parents avoided a hospital visit. Differences in KD incidence reduction patterns before and after the initiation of COVID-19 pandemic mitigation measures were found in patients with KD aged younger than 12 months compared with those 24 months or older, suggesting a potential KD pathogenesis involving transmission among children.

We first reported a phenomenon of cross-resistance to vancomycin (VCM) and daptomycin (DAP) in methicillin-resistant Staphylococcus aureus (MRSA) in 2006, but mechanisms underlying the cross-resistance remain incompletely understood. Here, we present a follow-up study aimed to investigate genetic determinants associated with the cross-resistance. Using 12 sets of paired DAP susceptible (DAPS) and DAP non-susceptible (DAPR) MRSA isolates from 12 patients who had DAP therapy, we (i) assessed susceptibility to DAP and VCM, (ii) compared whole-genome sequences, (iii) identified mutations associated with cross-resistance to DAP and VCM, and (iv) investigated the impact of altered gene expression and metabolic pathway relevant to the cross-resistance. We found that all 12 DAPR strains exhibiting cross-resistance to DAP and VCM carried mutations in mprF, while one DAPR strain with reduced susceptibility to only DAP carried a lacF mutation. On the other hand, among the 32 vancomycin-intermediate S. aureus (VISA) strains isolated from patients treated with VCM, five out of the 18 strains showing cross-resistance to DAP and VCM carried a mprF mutation, while 14 strains resistant to only VCM had no mprF mutation. Moreover, substitution of mprF in a DAPS strain with mutated mprF resulted in cross-resistance and vice versa. The elevated lysyl-phosphatidylglycerol (L-PG) production, increased positive bacterial surface charges and activated cell wall (CW) synthetic pathways were commonly found in both clinical isolates and laboratory-developed mutants that carry mprF mutations. We conclude that mprF mutation is responsible for the cross-resistance of MRSA to DAP and VCM, and treatment with DAP is more likely to select for mprF-mediated cross-resistance than is with VCM.