This is a case of a 63-year-old male admitted for 6 months in our hospital with a chronic enterocutaneous fistula, several surgeries (splenectomy, distal pancreatectomy and cholecystectomy) and carrier of a peripherally inserted central catheter (PICC) for total parenteral nutrition (TPN).
After 6 months with the PICC, he developed a high fever (38.5°C) and chills; therefore we proceeded to extract 2 sets of blood culture. 72h later, he suffered a new fever peak and another 2 sets of blood culture were obtained from both peripheral line and PICC. The blood cultures were processed by BACTEC 9240 (Becton–Dickinson).
After 24h of incubation, a growth of gram negative rods was detected in both aerobic samples from the first set, which were sub-cultivated in blood and McConkey agar and incubated at 37°C in CO2 atmosphere. Furthermore, Vitek-2 (bioMerieux) cards were inoculated directly from one positive aerobic bottle to determinate its identification and its sensibility by means of GN and AST-112 cards, respectively.
24h later, the Vitek-2 system identified the organism as Ochrobactrum anthropi with a concordance rate of 99.9%. Pale yellow colonies grew at subculture and they were processed in parallel by MicroScan WalkAway 96 plus (Siemens) automated system and Vitek-2 (bioMerieux) again. Again, both systems identified the isolated as Ochrobactrum anthropi with a concordance rate of 99.9%. Moreover, in the aerobic bottles from the second sets of blood cultures, O. anthropi was also isolated. The differential time to positivity of blood cultures from the reservoir catheter and the peripheral sites was at least 2h; therefore the bacteremia was diagnosed as catheter-associated.
The confirmation of the isolate was made with BIOLOG GP2 panel (BIOLOG, Inc., Hayward, U.S.A.) with 95 carbon sources by the Taxonomy Laboratory of the National Institute of Health Carlos III. It found a similarity of 99% (T=0.808 with, and by 16s rRNA sequencing fragment of 1255bp) by using a previously reported method.1 The sequence obtained showed a homology of 99.8% with Ochrobactrum anthropi from the GenBank (accession nos.: NR074243, JQ435696, and others).
Susceptibility testing was performed according to the manufacturer's recommendations using the 54 broth microdilution panel from MicroScan WalkAway 96 plus and the AST-112 and 114 cards from Vitek-2. The isolated was susceptible to all aminoglycosides (CIM Tobramycin ≤2mg/ml; CIM Gentamicin=2mg/ml; CIM Amikacin=16mg/ml), fluoroquinolones (CIM ciprofloxacin≤0.5mg/ml; CIM levofloxacin≤1mg/ml), trimethoprim-sulfamethoxazole (CIM≤2/38mg/ml) and Minocycline (CIM≤4mg/ml). But it was resistant to all betalactamics except for carbapenems (CIM Meropenem≤1mg/ml; CIM Imipenem≤1mg/ml).
Initially, it was decided not to start a treatment due to the fact that the patient's condition was healthy; but when the isolation was confirmed in subsequent extractions, it was decided to begin a treatment with intravenous ciprofloxacin. During the next days, the patient's condition improved and the subsequent blood cultures were negative.
The Ochrobactrum genus is formed by nonfermentative gram, strictly aerobic negative rods, positive oxidase, positive trypsine, positive urease and negative indole. Taxonomically, this genus belongs to the α-2 subgroup of the domain Proteobacteria and it is very close to the highly pathogenic Brucellae.2Ochrobactrum spp. was created by Holmes et al.3 in 1980 to assign the organisms that formerly were known as CDC group Vd. At first, O. anthropi was the only one species from the genus, but subsequent studies showed genetic and phylogenetic differences among the strains. Currently, 13 strains have been described, but only 2 species, O. anthropi and O. intermedium, have been reported as opportunistic pathogens in human beings.4
Ochrobactrum anthropi is ubiquitous in nature and it can be found in hospital environments. Therefore, the exposure to this pathogen is common. In fact, nosocomial infections due to this pathogen are increasing since the first case in human beings in 1980.5 Like Staphlylococcus genus,6O. anthropi has surface proteins which play an important role as a mediator of adherence. Thus, most of the cases reported are catheter-related infections in immunocompromised patients.6 However, it has been also reported in immunocompetent patients.7 Other reported cases have been pelvic abscess,7 endophthalmitis, meningitis8 and peritonitis.9
O. anthropi is resistant to all betalactamics except for carbapenems. This resistance is due to an AmpC betalactamase described as chromosomal, inducible and resistant to inhibition by clavulanic acid. It is considered susceptible to quinolones, aminoglycosides and colistin.
In conclusion, O. anthropi is an opportunistic pathogen which mainly causes catheter-related infections in immunocompromised patients. Even nowadays, this genus is of low virulence; its ubiquity in hospital environments, the increase of reported cases and the organism's intrinsic multiresistance to the most frequently used antibiotics put us on alert, as this microorganism can become a potentially problematic nosocomial pathogen similar to the current case of Acinetobacter spp.10
