Raoultella ornithinolytica: Emergence and Resistance.

Raoultella ornithinolytica is an encapsulated Gram-negative, oxidase-negative, catalase-positive, aerobic, non-motile rod that belongs to the Enterobacteriaceae family. This bacterium was initially classified in the genus Klebsiella as Klebsiella ornithinolytica, until the creation of the genus Raoultella in 2001. R. ornithinolytica is usually found in water environments and soil, and due to its ability to convert histidine to histamine, it has been associated with histamine poisoning in humans. R. ornithinolytica is an emerging entity in human infections, with several reports of virulent infections in comorbid at-risk patients. Increasing reports are potentially due to better and more precise identification tools. The objective of this article is to provide a comprehensive review of reported cases of R. ornithinolytica infections, the emergent virulence of described multiresistant strains, and an overview of currently used identification methods.

Community-acquired infection to Raoultella ornithinolytica presenting as appendicitis and shock in a healthy individual.

Raoultella ornithinolytica and Raoultella planticola are histamine-producing bacteria that are usually found in fish and water. They are associated with scombroid syndrome that presents with vomiting and flushing. A wide range of infections with these germs is reported, but mainly in fragile hospitalized patients with multiple comorbidities. We report the case of a 54-year-old healthy patient who presented with 24-hours abdominal pain, vomiting, flushing and shock. The abdominal examination showed guarding in the right lower quadrant (RLQ), and the abdominal CT scan images showed a thickened terminal ileum and a distended appendix. The patient underwent a surgical exploration revealing a normal terminal ileum but an inflamed appendicular base. Raoultella ornithinolytica was found in blood cultures and in the liquid retrieved from the RLQ. To the best of our knowledge, this is the first report of a severe life-threatening intra-abdominal presentation due to a community-acquired R. ornithinolytica infection.

Lymphopenia as a novel marker of Clostridium difficile infection recurrence.

BACKGROUND: Treatment of Clostridium difficile infection (CDI) is often limited by recurrence in 25% of cases. The objective of this study was to determine risk factors of CDI recurrence during a provincial endemic. METHODS: Data was prospectively collected for 1 year in a Montréal hospital. Inclusion criteria were: age ≥ 18 years; admission for ≥ 72 h; CDI diagnosis during current admission; no CDI diagnosis in the previous 3 months. RESULTS: A total of 121 patients were included, of which 42% were female. Mean age was 77 years, with a median Charlson comorbidity index of 5. Forty patients (33%) had recurrent disease within 2 months of initial CDI treatment. There were 20 deaths (17%) within the 2-month follow-up period. Higher risk of CDI recurrence was independently associated with older age (HR=2.26 for each decade), female gender (HR=1.56), and lymphopenia at completion of CDI treatment (HR=2.18), while a positive C. difficile antitoxin serology was protective (HR=0.17). CDI recurrence was not associated with either lymphopenia at time of diagnosis, underlying comorbidities, severity or treatment of the initial CDI episode, or re-exposure to antibiotics during the follow-up period. CONCLUSION: Lymphopenia at the end of CDI treatment appears to be a strong marker for CDI recurrence. This available and inexpensive test may identify patients who are at higher risk of CDI recurrence.

High incidence of herpes zoster in nonmyeloablative hematopoietic stem cell transplantation.

Although the use of nonmyeloablative (NMA) hematopoietic stem cell transplantation (HSCT) regimens has expanded in the past decade, little data exist to support antiviral prophylaxis to prevent herpes zoster (HZ) in recipients who are seropositive for varicella-zoster virus in this population. The present study examined the clinical features, incidence, and risk factors for HZ in a homogeneous cohort of NMA allogeneic HSCT recipients. We conducted a retrospective cohort study assessing all patients who underwent sibling NMA HSCT at Maisonneuve-Rosemont Hospital (Montreal) between July 2000 and December 2008. All patients received the same conditioning regimen, immunoprophylaxis, and graft-versus-host disease therapy. The diagnosis of HZ was defined clinically. Factors associated with HZ were identified using a Cox proportional hazards model. A total of 179 patients were followed for a median of 33 months (interquartile range, 21-59). HZ developed in 66 patients (37%) at a median of 8.3 months post-HSCT; the incidence rate was 175 cases/1000 person-years. The estimated cumulative HZ incidence was 27% at 1 year, 36% at 2 years, and 44% at 3 years. Thoracic dermatomes were most frequently involved (30%); dissemination occurred in 5 patients. No deaths resulted from HZ, but 23% of patients developed postherpetic neuralgia. In multivariate analysis, reactivation of cytomegalovirus and herpes simplex virus was associated with a reduced likelihood of HZ (hazard ratio, 0.54 and 0.33, respectively). Antiviral prophylaxis or treatment for cytomegalovirus and herpes simplex virus reactivations were protective against HZ. The incidence of HZ in our cohort of NMA HSCT recipients is similar to the incidence reported in HSCT recipients who received a myeloablative conditioning regimen. Given the observed high risk, we conclude that recommendations for antiviral prophylaxis should apply, at least for the first year, to the NMA HSCT population as well.