Isolation and identification of an Enterobacter cloacae strain producing a novel subtype of Shiga toxin type 1.
We describe here the isolation and identification of a Shiga toxin 1 (Stx1)-producing Enterobacter cloacae strain, M12X01451, from a human clinical specimen. The bacterial isolate was identified as E. cloacae using a polyphasic approach that included phenotypic, genetic, and proteomic analyses. The M12X01451 stx1 was sequenced, and the holotoxin was found to share only 87% amino acid sequence identity with the nearest Stx1 subtype reference sequence. Sequence analysis of the regions immediately flanking stx1 displayed similarities with bacteriophage-related sequences, suggesting a prophage origin. The stx1 gene was a stable element within the M12X01451 genome, as demonstrated by real-time PCR detection following successive subculturing of the bacterial isolate. Culture supernatant from M12X01451 was cytotoxic to Vero cells but was not neutralized by an anti-Stx1 monoclonal antibody. In addition, Stx1 from M12X01451 demonstrated limited antigenicity with two commercially available lateral flow immunoassays. The M12X01451 Stx represents a new Stx1 subtype based on the degree of sequence dissimilarity with Stx1 subtype reference sequences and its limited reactivity with anti-Stx1 antibodies.
Microbial Diseases Laboratory Branch, California Department of Public Health, Richmond, California, USA will.probert@cdph.ca.gov.
William S
WS
Probert
Microbial Diseases Laboratory Branch, California Department of Public Health, Richmond, California, USA.
Cassandra
C
McQuaid
Microbial Diseases Laboratory Branch, California Department of Public Health, Richmond, California, USA.
Kimmi
K
Schrader
D000595:Amino Acid Sequence; D000818:Animals; D015373:Bacterial Typing Techniques; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016972:Enterobacter cloacae / Q000235:genetics* / Q000302:isolation & purification*; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D006801:Humans; D008969:Molecular Sequence Data; D039002:Prophages / Q000235:genetics; D020543:Proteome / Q000032:analysis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D022621:Shiga Toxin / Q000235:genetics* / Q000378:metabolism*; D014709:Vero Cells
D004269:DNA, Bacterial; D020543:Proteome; D022621:Shiga Toxin