A review of the public health management of shigellosis in Australia in the era of culture‐independent diagnostic testing

Abstract

Objective: To review the national case definition for shigellosis following the introduction of culture independent diagnostic testing by clinical laboratories and provide evidence to reform jurisdictional public health practices for the management shigellosis., . Methods:A review of all Australian jurisdictional public health guidelines for shigellosis was conducted. Victorian 2014 shigellosis data were analysed: demographics and risk factors for cases identified by conventional culture or culture-independent diagnostic methods were described.

Culture‐positive shigellosis cases are epidemiologically different to culture‐negative/PCR‐positive cases

“…This study confirmed some previously identified epidemiological differences between Shigella culture-positive and Shigella culture-negative/PCR-positive cases in Victoria, 21 including the difference in time between symptom onset and specimen collection, and risk factors for disease. However, this review also uniquely identified differences in clinical severity between culture-positive and culturenegative/PCR-positive cases by number of symptoms reported and hospitalisation rates.…”

“…However, this review also uniquely identified differences in clinical severity between culture‐positive and culture‐negative/PCR‐positive cases by number of symptoms reported and hospitalisation rates. Identifying these additional epidemiological differences in NSW adds to the evidence base for informing potential recommendations for changes to the national shigellosis case definition 12,21 . However, before changes can be recommended, further studies on the laboratory differentiation of culture‐negative/PCR‐positive cases are required to determine the true prevalence of Shigella versus EIEC in this group of cases that are currently excluded from public health follow‐up in NSW and some other jurisdictions.…”

“…There is growing evidence for the need to consider whether Shigella culture‐negative/PCR‐positive cases should be included in the national surveillance case definition for shigellosis 21 . Three jurisdictions in Australia do not automatically exclude culture‐negative/ ipaH PCR‐positive cases and classify them as “ Shigella species not typed”, “ Shigella not specified” or “probable Shigella /EIEC” 21 .…”

“…Identifying these additional epidemiological differences in NSW adds to the evidence base for informing potential recommendations for changes to the national shigellosis case definition. 12,21 However, before changes can be recommended, further studies on the laboratory differentiation of culture-negative/ PCR-positive cases are required to determine the true prevalence of Shigella versus EIEC in this group of cases that are currently excluded from public health follow-up in NSW and some other jurisdictions. Determining the true burden of shigellosis throughout Australia is important for public health control.…”

“…However, as this gene is present in both EIEC and Shigella 20 and, as EIEC is not a notifiable disease in Australia, the use of this gene for the diagnosis of shigellosis must factor in a possible alternative diagnosis of EIEC when setting case definitions. A previous Victorian study 21 examined the epidemiological differences between culture‐positive and culture‐negative (but ipaH PCR‐positive) cases of shigellosis to help inform discussions about a change in national case definitions; however, this has not been repeated in other jurisdictions. We therefore audited a series of culture‐positive and culture‐negative (but ipaH PCR‐positive) cases of shigellosis in the high‐prevalence area of Sydney LHD (SLHD), NSW, to determine whether there are any significant differences between these groups to provide further evidence for determining whether a change to the national case definition for shigellosis should be recommended.…”