Identification and molecular epidemiology of a nosocomial outbreak of Ochrobactrum anthropi bacteriemia. First report in Argentina

Background: Ochrobactrum anthropi (OA) is a non-fermenting gram-negative bacillus usually found in the environment. During the past decade it has become increasingly recognized as a potentially opportunistic, and nosocomial pathogen. Infection is most commonly, although not exclusively, seen in immunocompromised patients and rarely linked to outbreaks. We observed a sudden increase in rates of OA isolation from blood cultures from adult patients hospitalized in our Institution for a 19 months period. Therefore, an investigation was undertaken to determine the occurrence of a nosocomial outbreak and to identify the probable source of infection confirm determine. OBJECTIVE: To define the extent of an outbreak of OA bacteremia, determine the source of the infection, and implement control measures. Methods & Materials: SETTING: A 350-bed, general hospital in Buenos Aires Province, Argentina. PATIENTS: Adult patients hospitalized in intensive care areas. METHODS: Isolates from blood cultures of 20 patients from March 2016 through September 2017 were identified phenotypically by NMIC/ID-92 (BD Phoenix), API 20NE (bioMérieux) and conventional biochemical tests. Identification was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with the MALDI Bruker Biotyper system (microflex LT; Bruker Daltonik). The investigation included a detailed review of all cases and direct observation of clinical practices. Facility inspection, a review of practices and an environmental sampling including antiseptic solutions and medical devices, was perfomed. Genetic relatedness was assessed by pulsed-field gel electrophoresis (PFGE). Results: All cases isolates were confirmed as OA. All environmental samples tested negative for OA except for one swab sample taken from the tap of a washbasin located in one patient's room. PFGE was performed to 11 case isolates (4 from 2016 and 7 from 2017) and the environmental sample. They showed identical genetic profile. Control measures involving education workshops for health care workers as well as aseptic practices revision were held. No other microbiologically confirmed infections occurred till this moment. Conclusion: This is the first OA outbreak documented in Argentina. A low-level outbreak involving environmental bacteria might be masked by antimicrobial drug prophylaxis and a low number of cases. Healthcare personnel should promptly report any increase in isolation of unusual pathogens to infection control units.