ABSTRACT Minor O-serogroups of Shiga toxin-producing Escherichia coli (STEC) can cause severe clinical complications in humans, including hemolytic uremic syndrome (HUS). However, detection and isolation of these minor serogroups of STEC are challenging due to the lack of specific isolation methods. Here, we present a case of HUS in which STEC was not isolated by routine diagnostic tests for the major serotypes. Therefore, we tried a new diagnostic and isolation method that combines PCR screening, immunomagnetic bead separation, and serum agglutination tests and successfully isolated STEC O76. Subsequent genomic analyses of the STEC O76 isolates revealed that several isolates of this serogroup carrying stx2 were related to severe infections. The complete genome of the HUS-derived isolates provided two important implications. First, using a complete genome as a reference in core genome single nucleotide polymorphism analysis leads to the highest resolution of the analysis. Second, the HUS-derived STEC O76:H7 possessed two copies of Stx2a prophages, and one of them showed a “prophage integrating into prophage” structure, as described in STEC O145:H28. These results demonstrate that our detection methods contribute to the diagnosis and isolation of minor serogroups of STECs and complete genomic analyses can illuminate the pathogenic potential of STECs. IMPORTANCE Hemolytic uremic syndrome (HUS) is a life-threatening disease caused by Shiga toxin-producing Escherichia coli (STEC) infection. The treatment approaches for STEC-mediated typical HUS and atypical HUS differ, underscoring the importance of rapid and accurate diagnosis. However, specific detection methods for STECs other than major serogroups, such as O157, O26, and O111, are limited. This study focuses on the utility of PCR-based O-serotyping, serum agglutination tests utilizing antibodies against the identified Og type, and isolation techniques employing antibody-conjugated immunomagnetic beads for STEC isolation. By employing these methods, we successfully isolated a STEC strain of a minor serotype, O76:H7, from a HUS patient.
Public health interventions have played an important role in controlling coronavirus disease 2019 (COVID-19), which is a rapidly spreading infectious disease. To contribute to future COVID-19 countermeasures, we aimed to verify the results of the countermeasures employed by public health centers (PHCs) against the first wave of COVID-19 in Yamagata Prefecture, Japan (Yamagata). Between January and May 2020, 1,253 patients suspected of SARS-CoV-2 infection were invited for testing. Simultaneously, based on retrospective contact tracings, PHCs investigated the infection sources and transmission routes of laboratory-confirmed COVID-19 cases and tested 928 contacts. Consequently, 69 cases were confirmed between March 31 and May 4, 58 of whom were from among the contacts (84.1%; 95% confidence interval [CI] 75.5-92.7). The spread of infection was triggered in cases harboring epidemiological links outside Yamagata. Subsequently, the number of cases rapidly increased. However, PHCs identified epidemiological links in 61 (88.4%; 95% CI 80.8-96.0) of the 69 cases, and transmission chains up to the fifth generation. Finally, the spread of infection ended after approximately one month. Our results indicate that the identification of infection sources and active case finding from contacts based on retrospective contact tracing was likely to be an effective strategy in ending the first wave of COVID-19 in Yamagata.
Legionella pneumophila serogroup (SG) 1, the main cause of Legionnaires' disease, can be diagnosed with urinary antigen testing kits; however, lower respiratory tract specimen culture is necessary to identify L. pneumophila SG 2–15. We attempted to detect L. pneumophila SG-specific genes in a culture-negative sputum specimen from a patient with pneumonia suspected to have Legionnaires' disease. Two multiplex PCR methods targeting L. pneumophila were modified and amplicons considered to be SG13 specific were detected. Direct sequencing revealed that the amplicons were identical to the nucleotide sequence of L. pneumophila SG13. Based on the presentation and clinical course (fever, muscle pain, disturbance of consciousness, high C-reactive protein titer, rhabdomyolysis, hypophosphatemia, and symptomatic improvement with levofloxacin treatment) in combination with the detection of L. pneumophila SG-specific genes, we suspected L. pneumophila SG13 pneumonia. L. pneumophila non-SG1 pneumonia is thought to be underestimated due to of its difficult laboratory diagnosis. The modified multiplex PCR system for lower respiratory tract specimens shown in this study is likely to increase the diagnosis of Legionnaires' disease caused by L. pneumophila SG13 and other SGs.
