Shiga Toxin 1-Producing Shigella sonnei Infections, California, United States, 2014-2015.

Shiga toxins (Stx) are primarily associated with Shiga toxin-producing Escherichia coli and Shigella dysenteriae serotype 1. Stx production by other shigellae is uncommon, but in 2014, Stx1-producing S. sonnei infections were detected in California. Surveillance was enhanced to test S. sonnei isolates for the presence and expression of stx genes, perform DNA subtyping, describe clinical and epidemiologic characteristics of case-patients, and investigate for sources of infection. During June 2014-April 2015, we identified 56 cases of Stx1-producing S. sonnei, in 2 clusters. All isolates encoded stx1 and produced active Stx1. Multiple pulsed-field gel electrophoresis patterns were identified. Bloody diarrhea was reported by 71% of case-patients; none had hemolytic uremic syndrome. Some initial cases were epidemiologically linked to travel to Mexico, but subsequent infections were transmitted domestically. Continued surveillance of Stx1-producing S. sonnei in California is necessary to characterize its features and plan for reduction of its spread in the United States.

Recurrent wound botulism among injection drug users in California.

BACKGROUND: Botulism is an acute neurologic illness characterized by cranial nerve palsies and descending flaccid paralysis. Botulism is a rare disease and recurrent botulism even more rare. We review cases of recurrent wound botulism (WB) among injection drug users (IDUs) in California from 1993 through 2006 and describe 2 case patients. METHODS: From botulism surveillance data for 1993-2006, we identified patients with >1 episode of clinical WB, defined as acute descending paralysis with a visible wound or recent history of injection drug use. For each patient, ≥1 of their WB episodes was laboratory confirmed. We extracted demographic, clinical, and laboratory information from case and laboratory reports and compared clinical characteristic frequency of initial and second WB episodes. RESULTS: During 1993-2006, 17 IDUs had recurrent WB, 14 with 1 recurrence and 3 with 2 recurrences. Of 25 laboratory-confirmed episodes, 22 were confirmed through serum testing and 3 through wound testing. Patients were 32-61 years old, and 94% were male. All patients reported heroin injections; 88% specified black tar heroin use and 76% reported subcutaneous injection. The most common presentations were having a visible wound, speech difficulty, double vision, respiratory difficulty, and trouble swallowing. There were no significant differences in clinical presentation between initial and second episodes. CONCLUSIONS: As the California epidemic of WB among IDUs continues, WB episodes are recurring. Both clinicians and IDUs should be aware of the potential for WB to recur among IDUs to enable timely diagnosis and early botulinum antitoxin administration and supportive care.

Sensitivity of mouse bioassay in clinical wound botulism.

BACKGROUND: California has an ongoing epidemic of wound botulism (WB) among injection drug users (IDUs). We retrospectively studied a cohort of patients with WB and determined the sensitivity of the mouse bioassay-the gold standard laboratory test for confirmation of botulism-in verifying WB. METHODS: We defined a clinical case of WB as an acute, bilateral, descending, flaccid paralysis starting with 1 cranial nerve palsies in an IDU with no other explainable diagnosis. We calculated the sensitivity of the mouse bioassay as the proportion of clinical WB cases that had positive serum toxin test results by mouse bioassay. We compared serum toxin-positive with serum toxin-negative patients. RESULTS: Of 73 patients with WB, 50 tested serum toxin positive, yielding a sensitivity of 68%. Serum toxin-positive patients did not differ significantly from serum toxin-negative patients with respect to demographic characteristics or injection drug use practices or in days from patient symptom onset to collection of specimens for testing. Patients did not differ significantly by clinical characteristics, except that serum toxin-positive patients were more likely than serum toxin-negative patients to have required mechanical ventilation during their hospital courses (74% vs. 43%; P = .01). CONCLUSIONS: In this study, the mouse bioassay failed to detect botulinum toxin in the serum samples of nearly one-third of IDUs with characteristic WB. Such patients should be considered to have probable WB. Physicians should be aware of the test's limitations and base their final diagnosis of suspected WB on clinical criteria when the mouse bioassay produces negative results.

Feasibility of reduction in use of the mouse bioassay: presence/absence screening for saxitoxin in frozen acidified mussel and oyster extracts from the coast of California with in vitro methods.

In the United States, the detection of paralytic shellfish poisoning (PSP) for regulatory purposes relies on the mouse bioassay (MBA). Using a saxitoxin presence/absence test could reduce animal usage significantly. Three in vitro methods, the RIDASCREEN Saxitoxin kit, MIST Alert, and a 5 h neuroblastoma assay, were evaluated in parallel with the MBA using 106 twice-frozen, acidified extracts from California-grown mussel and oyster tissues. For each assay, a cutoff point was established whereby data below or equal to that point were scored as negative and were assigned a score of zero. Data above the cutoff were considered positive and assigned a score of one. Pearson correlation coefficients were generated. The RIDASCREEN, MIST Alert, and neuroblastoma bioassay correlated to the MBA at 0.849, 0.853, and 0.832 when used for presence/absence detection. These data suggest that a reduction in MBA usage could be achieved in the surveillance of California-grown mussels and oysters for PSP-associated toxins. Correlation data between the in vitro assays, cost comparisons, and the potential for false negatives and false positives were examined. Implications of these methodologies in protecting public health are discussed.