Evolution of a Distinct SARS-CoV-2 Lineage Identified during an Investigation of a Hospital Outbreak.

The SARS-CoV-2 virus steadily evolves, and numerous antigenically distinct variants have emerged over the past three years. Tracking the evolution of the virus would help us understand the process that generates the diverse variants and predict the future evolutionary trajectory of SARS-CoV-2. Here, we report the evolutionary trajectory of a unique Omicron lineage identified during an outbreak investigation that occurred in a residence unit in the healthcare system. The new lineage had four distinct non-synonymous and two distinct synonymous mutations apart from its parental lineage. Since this lineage of virus was exclusively found during the outbreak, we were able to track the detailed evolutionary history of the entire lineage along the transmission path. Furthermore, we estimated the evolutionary rate of the SARS-CoV-2 Omicron variant from the analysis of the evolution of the lineage. This new Omicron sub-lineage acquired 3 mutations in a 12-day period, and the evolutionary rate was estimated as 3.05 × 10-3 subs/site/year. This study provides more insight into an ever-evolving virus.

Universal MRSA nasal surveillance: characterization of outcomes at a tertiary care center and implications for infection control.

BACKGROUND: Recognition of methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage by active surveillance cultures has been widely debated. Our institution implemented universal nasal screening by polymerase chain reaction (PCR) for MRSA and isolation of screen positive patients in December 2007. Here we present data about the correlation between screen positivity and subsequent development of infection and the impact of isolation on surgical site infection rates. METHODS: This was a retrospective, observational study from January 1, 2008, through June 30, 2008, on all inpatient admissions with a nasal MRSA PCR screen. Genotype of 15 MRSA blood isolates was determined utilizing the Diversilab® (bioMérieux, Hazelwood, MO) system. A phenotypic rule was deduced and utilized for analyzing all MRSA clinical isolates. RESULTS: 5375 patients were screened at ≤48 hours following admission. 581 MRSA positive nasal carriers (10.80%) were identified. 496 (85.3%) were asymptomatic MRSA nasal carriers. There were a total of 158 MRSA clinical infections. 85 (14.6%) MRSA nasal carriers had clinical infection. Of the 4794 (89.1%) non-nasally colonized patients, 73 (1.5%) had MRSA clinical infection. MRSA surgical site infection rate remained unchanged during the intervention period. Phenotypic predictive rule inferred 59.8% community-acquired MRSA (CA-MRSA) infections and 40% hospital-acquired MRSA (HA-MRSA) infections. CONCLUSIONS: Our study showed a positive correlation between having a nasal screen positivity and subsequent development of infection. Isolation of MRSA screen positive patients alone as an intervention did not reduce the surgical site infection rates. Since most of our isolates are CA-MRSA, our institution is implementing several new interventions to further reduce the incidence of HA-MRSA conditions.

Brevibacillus brevis peritonitis.

We present what we believe is the first case of Brevibacillus (Bacillus) brevis peritonitis in a patient with hepatocellular carcinoma, possibly caused by the ingestion of fermented foods containing B. brevis spores. This case also demonstrates a pattern of antibiotic susceptibility with differing in vitro and in vivo bactericidal efficacy.

Cluster of Mycobacterium fortuitum prosthetic joint infections.

Mycobacterium fortuitum is a member of the rapidly growing nontuberculous mycobacteria. Although mortality is rare from M. fortuitum, morbidity depends on the localized site of infection. M. fortuitum is ubiquitous in the environment and has been reported to cause infections of prosthetic devices. There have been seven previously reported cases of prosthetic joint infections due to M. fortuitum. This article presents three additional cases of postoperative joint infections due to M. fortuitum. All three cases were confirmed to be genetically indistinguishable by pulse-field gel electrophoresis. Awareness of its importance is especially noteworthy in the realm of ongoing antibiotic resistance.