This nosocomial outbreak of infection due to a highly vancomycin-resistant strain of Enterococcus is the first epidemic in which an electronic thermometer has been implicated as the vehicle of transmission for an infectious agent.

To our knowledge, this is the first US study to report a reemergence of gram-negative organisms as a cause of PHA-BSIs. This finding does not seem to be related to changes in specific gram-negative organisms or to antimicrobial resistance. If this trend continues, it will have important implications for the management of bloodstream infections.

Enterobacter hormaechei was first identified as a unique species in 1989. Between 29 November 1992 and 17 March 1993, an outbreak of E. hormaechei occurred among premature infants in the intensive care nursery (ICN) at The Hospital of the University of Pennsylvania. The 10 infants whose cultures were positive for E. hormaechei (six were infected and four were colonized) had a lower median estimated gestational age and birth weight than did other ICN infants; other risk factors for infection or colonization with E. hormaechei were not identified. Cultures from three isolettes and a doorknob in the ICN were positive for E. hormaechei. Pulsed-field gel electrophoresis of isolates from six patients and two isolettes were identical. Observations of health care workers revealed breaks in infection control techniques that may have allowed transmission of this organism. We found that E. hormaechei is a nosocomial pathogen that can infect vulnerable hospitalized patients and that can be transmitted from patient to patient when infection control techniques are inadequate.

Staphylococci producing exfoliative toxins are the causative agents of staphylococcal scalded skin syndrome (SSSS). Exfoliative toxin A (ETA) is encoded by eta, which is harbored on a temperate bacteriophage ΦETA. A recent increase in the incidence of SSSS in North America has been observed; yet it is largely unknown whether this is the result of host range expansion of ΦETA or migration and emergence of established lineages. Here, we detail an outbreak investigation of SSSS in a neonatal intensive care unit, for which we applied whole-genome sequencing (WGS) and phylogenetic analysis of Staphylococcus aureus isolates collected from cases and screening of healthcare workers. We identified the causative strain as a methicillin-susceptible S. aureus (MSSA) sequence type 582 (ST582) possessing ΦETA. To then elucidate the global distribution of ΦETA among staphylococci, we used a recently developed tool to query extant bacterial WGS data for biosamples containing eta, which yielded 436 genomes collected between 1994 and 2019 from 32 countries. Applying population genomic analysis, we resolved the global distribution of S. aureus with lysogenized ΦETA and assessed antibiotic resistance determinants as well as the diversity of ΦETA. The population is highly structured with eight dominant sequence clusters (SCs) that generally aligned with S. aureus ST clonal complexes. The most prevalent STs included ST109 (24.3%), ST15 (13.1%), ST121 (10.1%), and ST582 (7.1%). Among strains with available data, there was an even distribution of isolates from carriage and disease. Only the SC containing ST121 had significantly more isolates collected from disease (69%, n = 46) than carriage (31%, n = 21). Further, we identified 10.6% (46/436) of strains as methicillin-resistant S. aureus (MRSA) based on the presence of mecA and the SCCmec element. Assessment of ΦETA diversity based on nucleotide identity revealed 27 phylogroups, and prophage gene content further resolved 62 clusters. ΦETA was relatively stable within lineages, yet prophage variation is geographically structured. This suggests that the reported increase in incidence is associated with migration and expansion of existing lineages, not the movement of ΦETA to new genomic backgrounds. This revised global view reveals that ΦETA is diverse and is widely distributed on multiple genomic backgrounds whose distribution varies geographically.

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