Peritonitis due to Ochrobactrum anthropi in a patient undergoing continuous ambulatory peritoneal dialysis

The Genus Ochrobactrum as Major Opportunistic Pathogens

Ochrobactrum species are non-enteric, Gram-negative organisms that are closely related to the genus Brucella. Since the designation of the genus in 1988, several distinct species have now been characterised and implicated as opportunistic pathogens in multiple outbreaks. Here, we examine the genus, its members, diagnostic tools used for identification, data from recent Ochrobactrum whole genome sequencing and the pathogenicity associated with reported Ochrobactrum infections. This review identified 128 instances of Ochrobactrum spp. infections that have been discussed in the literature. These findings indicate that infection review programs should consider investigation of possible Ochrobactrum spp. outbreaks if these bacteria are clinically isolated in more than one patient and that Ochrobactrum spp. are more important pathogens than previously thought.

Ochrobactrum Peritonitis: Case Report and Literature Review

End-stage kidney disease (ESKD) patients, including those on peritoneal dialysis (PD), are considered immunocompromised and at risk for opportunistic pathogens. Peritonitis is a major infectious PD complication with common causative pathogens, including gram-positive organisms such as coagulase-negative Staphylococcus species, Staphylococcus aureus more often than gram negative organisms. PD peritonitis is often secondary to suboptimal technique leading to contamination of the catheter site but can also be due to bacterial translocation from the bowel lumen or transient bacteremia after procedures; this makes identification of the causative organism crucial to optimal management of PD peritonitis. Ochrobactrum are glucose-non-fermentative, non-fastidious, motile gram-negative bacilli typically isolated in aqueous environments. Reported infections primarily occur in immunocompromised hosts with environmental exposure, including nosocomial contamination of fluids or indwelling catheters. We present only the seventh reported case of Ochrobactrum peritonitis in a 67-year-old PD patient secondary to poor technique, and review the literature for all prior cases. Although there have been no previous cases leading to bacteremia, three of the seven cases required removal of PD catheter.

Peritonitis in type 2 diabetes mellitus due to Ochrobactrum anthropi complicating automated peritoneal dialysis

Epidemiology data predict that by the year 2025, diabetes will affect about 380 million people worldwide with a significant increase in patients with chronic renal disease progressing to hemodialysis. Diabetes-related peripheral vascular disease is a major risk factor for vascular access failure in patients on extracorporeal hemodialysis. Although peritoneal dialysis is a valid option for diabetics, peritonitis is still a main complication for these patients. We report the case of a 71-year-old type 2 diabetes patient treated by subcutaneous insulin, undergoing automated peritoneal dialysis (APD) who developed peritonitis and bloodstream infection by Ochrobactrum anthropi (O. anthropi). The patient was initially shifted to continuous ambulatory peritoneal dialysis (CAPD) and treated with intraperitoneal cefotaxime and gentamicin. According to antibiogram, cefotaxime was discontinued but lasting gentamicin. Within 48 h from admission, clear peritoneal effluent was observed with reduction in white blood cells count from 580/mm³ 77.9% neutrophils to less than 10/mm³. Prompt regression of infection without catheter removal and no relapse after over 7-month follow-up allowed supposing that O. anthropi did not colonized peritoneal catheter. O. anthropi is an emerging cause of nosocomial infection in immunocompromised patients. Cases of such infection in patients undergoing CAPD and hemodialysis have been already described. However, this is the first reported case of O. anthropi in a patient undergoing APD.

Identification and antimicrobial susceptibilities of Ochrobactrum spp

Ochrobactrum (O.) anthropi is an opportunistic emerging pathogen closely related to the genus Brucella. Identification and differentiation from brucellae and other Ochrobactrum spp. using routine biochemical test systems is not reliable due to the high phenotypic similarity. In this study, antibiotic susceptibilities of 103 Ochrobactrum isolates were determined using Etest for 19 clinically relevant antimicrobial agents. Ochrobactrum strains were highly resistant to beta-lactam antibiotics, susceptible to ciprofloxacin, and 97.1% were susceptible to trimethoprim/sulfamethoxazole. It was also demonstrated that biochemical reaction profiles of the API and BD Phoenix 100 systems for identifying Ochrobactrum isolates can only be used on the genus level. Our in vitro data suggest that combinations of antimicrobial agents including ciprofloxacin and/or trimethoprim/sulfamethoxazole may be useful for empirical treatment of Ochrobactrum infections.

[Species identification and molecular epidemiology of bacteria belonging to Ochrobactrum genus]

Two species of medical interest belong to the genus Ochrobactrum, Ochrobactrum anthropi and Ochrobactrum intermedium. They are members of the microbiota of soil and an increasing number of works report the isolation of O. anthropi from clinical specimen, especially from immunocompromised patients and nosocomial infection. Involving of each species in human infection is poorly estimated due to unclear differential phenotypic characters. We performed 16S rDNA sequencing for identification of 20 clinical isolates of Ochrobactrum sp. to the species level. Then, we studied the phenotype of each isolate especially, morphology, culture onto different media and at different temperatures, biochemical characters and antibiotics resistance pattern. Colony morphology after growth onto Trypticase-Soy and McConkey agar, culture at 45 degrees C onto Trypticase-Soja agar, presence of urease, and netilmycin, tobramycin and colistin resistance allowed identification of species. Ribotyping using HindIII and EcoRI gave a supplementary criterion for species determination but did not allow typing at the infra-species level. In contrast, Pulsed-Field Gel Electrophoresis showed high degree of polymorphism between strains and proved the clonality of certain isolates. Thus, this method could be a useful tool for molecular epidemiology of Ochrobactrum infections.

Ochrobactrum anthropi bloodstream infection complicating hemodialysis

We report two cases of bacteremia with Ochrobactrum anthropi in patients on hemodialysis. Bacteremia became clinically manifest by recurrent febrile episodes during and after dialysis. In one patient, bacteremia persisted after ciprofloxacin therapy and was cleared only by removal of the dialysis catheter and a 3-week course of gentamicin. The second patient remained intermittently bacteremic for more than 3 months, although the dialysis catheter had been replaced. A MEDLINE search revealed only one previous report of O anthropi bloodstream infection in a patient on hemodialysis, but the pathogen is recognized increasingly as a causative agent of human disease, most importantly in debilitated patients. In contrast to most previously described cases, the two patients reported here had no malignancies and were not on immunosuppressive therapy. Treatment of O anthropi infection is challenging because of widespread and unpredictable resistance to antimicrobial agents and discrepancies between in vitro susceptibility and in vivo efficacy.