Prolonged Outbreak of Multidrug-Resistant Shigella sonnei Harboring bla _CTX-M-27 in Victoria, Australia

Abstract

Objectives: In Australia, cases of shigellosis usually occur in returned travellers from shigellosis-endemic regions, or in men who have sex with men. Resistance to multiple antibiotics has significantly increased in Shigella sonnei and represents a significant public health concern. Here we investigate an outbreak of multidrug-resistant S. sonnei in Victoria, Australia. Methods: We undertook whole genome sequencing of 54 extended-spectrum beta-lactamase (ESBL) producing S. sonnei received at the Microbiological Diagnostic Unit Public Health Laboratory between January 2019 and March 2020. The population structure and antimicrobial resistance profiles were identified by genomic analyses, with 73 previously characterised Australian S. sonnei to provide context. Epidemiological data including age and sex of the shigellosis cases were also collected. Results: There was a significant increase in cases of ESBL S. sonnei from July 2019. Most of the ESBL S. sonnei (65%) fell within a single cluster, that was predominantly comprised of male cases, and were characterised by the presence of blaCTX-M-27 gene conferring resistance to extended-spectrum cephalosporins. These isolates were also multidrug-resistant, including resistance to azithromycin and co-trimoxazole and reduced susceptibility to ciprofloxacin. Conclusions: Our data has uncovered a prolonged clonal outbreak of ESBL S. sonnei that was likely first introduced by returned travellers and has subsequently been circulating locally in Australia. The emergence of a local outbreak of ESBL S. sonnei, with a multidrug-resistant profile, including reduced susceptibility to ciprofloxacin, represents a significant public health threat.

Acquisition and loss of CTX-M plasmids in Shigella species associated with MSM transmission in the UK

“…bla CTX-M-27 -positive S. sonnei has recently driven a prolonged MSM outbreak in Australia [17], with one successful sublineage harbouring an AMR profile consistent with one isolate in this study, 598 080 ( mphA, ermB, dfrA1 and sul2 genes with gyrA S83L). Typing of S.…”

“…In this study, aph(6)-Id/aph(3)-Ib / sul2/tet(A ) carriage was on a large (~103 kbp) IncB/O/K/Z plasmid with Australian links. bla CTX-M-27 -positive S. sonnei has recently driven a prolonged MSM outbreak in Australia [ 17 ], with one successful sublineage harbouring an AMR profile consistent with one isolate in this study, 598 080 ( mphA, ermB, dfrA1 and sul2 genes with gyrA S83L). Typing of S. sonnei isolates 598 080 and 607 387 determined them as VN2.KH1.Aus; Australian isolates emerging from Kahnh Hoa Subclone 1 [ 47 ].…”

“…This element recently drove a prolonged S. sonnei outbreak among MSM in Victoria, Australia [17] but few CTX-M Shigella plasmids have been characterised [18]; seemingly only one other has been described in detail, in a Swiss S. sonnei isolate [19].…”

“…However, in 2015 Public Health England (PHE) described an ESBL-producing S. sonnei MSM cluster [ 16 ] conferred by a pKSR100-like plasmid (p183660), which had acquired bla CTX-M-27 . This element recently drove a prolonged S. sonnei outbreak among MSM in Victoria, Australia [ 17 ] but few CTX-M Shigella plasmids have been characterised [ 18 ]; seemingly only one other has been described in detail, in a Swiss S. sonnei isolate [ 19 ].…”

Emergence of novel strains of Shigella flexneri associated with sexual transmission in adult men in England, 2019–2020

“…sonnei , and outbreaks of extended-spectrum beta-lactamase-producing S. sonnei have been described [1, 11, 17–22]. Overuse of certain antimicrobials is likely to be a contributing factor in driving increasing resistance to the same class of antimicrobials.…”