Outbreak Description and Setting

In October 2014, the urology team of Hôpital Édouard Herriot, a teaching hospital with ≈850 beds, located in Lyon, France, alerted the radiology department that in the previous 3 weeks, 6 patients had dysuria and UTIs involving unusual pathogens <10 days after each had a prostate biopsy. The radiology department, which performed the biopsies, asked the hospital infection control unit to investigate, and the investigation began immediately.

Of the 6 initial case-patients, 4 had Achromobacter xylosoxidans UTIs and 2 had Ochrobactrum anthropi UTIs, all occurring after a TUPB. The radiology department performs ≈450 biopsies per year, all in the same ultrasound room. According to hospital records, ≈1% of patients call back to report symptoms of infections and need to submit urine or blood cultures within 15 days after biopsy.

Biopsy Protocol

Figure 1

Figure 1. Application of biopsy needle on sponge used during transrectal ultrasound-guided prostate biopsy. A) Needle before scraping a biopsy core on sponge; B) needle after scraping to detach a biopsy core on...

All biopsies were preceded by a single dose of antimicrobial drug prophylaxis (400 mg ofloxacin), as recommended by national guidelines at the time of the procedures (11). As a preliminary step, nonsterile sponges were soaked in a 0.9% solution of sodium chloride (NaCl) and placed in small plastic cases on a table beside the patient. During the first part of the procedure, the main operator undertook transrectal ultrasonography with a probe covered by an inner layer of gel, a protective plastic sheath, and an outer layer of gel. During the second part of the procedure, a needle guide was mounted on top of the plastic sheath, and the operator worked the automatic biopsy gun with his or her main hand, while holding the ultrasound probe with the other hand. After a sample was taken, the needle was scraped against one of the sponges to remove the biopsy core (Figure 1, panels A, B); the needle was then reused until all relevant samples were obtained. At the end of the procedure, the integrity of the probe sheath was checked, and all equipment was discarded or sanitized. Patients were advised to call their radiologist or urologist if they had fever, pain, difficulty urinating, or prolonged bleeding.

Case–Control Study and Retrospective Surveillance

Administrative, clinical, and microbiologic records of all patients who underwent a TUPB at the hospital during September 1–October 31, 2014, were reviewed to find putative additional cases. The urology team was also asked to report any additional cases found as a result of systematic postbiopsy follow-up consultation. Confirmed cases were defined as patients having fever, pain, or dysuria and a positive urine or blood culture requested <15 days after biopsy that showed presence of A. xylosoxidans or O. anthropi infection. Controls were all patients who underwent a TUPB in the same ultrasound room during the same 2-month period but who were not asked to submit a blood or urine culture. Possible cases were retrospectively defined as patients for whom a clinician had requested >1 urine or blood culture <15 days after biopsy, regardless of the result, because of a clinical suspicion of prostatis (i.e., presence of fever, pain, or dysuria). Possible cases were not included in our statistical calculations.

Temporal distribution of cases involved an index case that occurred in August 2014, a month before the other cases occurred in September and October 2014 at a rate of ≈2 per week. All possible control-patients (n = 44) whose biopsies occurred between the first and last case of the September–October cluster were included. In addition, 6 temporally matched control-patients were included for the August case-patient; these patients were biopsied on the same day or <1 week before the case-patient.

Records were reviewed to assess organizational risk factors (e.g., operator identity or order in which patients had biopsies during the day) and individual features (e.g., patient age or histologic evidence of localized inflammation). Retrospective surveillance was also conducted by accessing an electronic database that contained dates and patient names for all prostate biopsies in the radiology unit and that contained dates, patient names, and results (i.e., species and antibiograms) for all blood and urine cultures in the hospital network laboratory during January 2011–November 2014. Records for November 2014–March 2015 were similarly analyzed to confirm the clinician-reported absence of new cases after implementation of corrective measures.

Microbiologic Methods and Molecular Typing

All biopsy materials were investigated microbiologically. Tap water was gathered in sterile containers (Dominique Dutscher, Brumath, France). Sterile cotton swabs (Biolys, Taluyers, France) were used for transducer probe and sink drain samples. Worktop and handwashing sink samples were plated on Count Tact Agar plates (bioMérieux, Marcy l’Etoile, France). For A. xylosoxidans and O. anthropi, trypticase soy broth (TSB) was used as preenrichment broth, supplemented with cetrimide (2 g/L) for A. xylosoxidans and amoxicillin (10 mg/L) for O. anthropi. Brain–heart infusion (BHI) enrichment broth, supplemented with aztreonam (32 mg/L) and vancomycin (32 mg/L), was also used for both bacteria, as described (15).

For each species, 200 mL of tap water and 0.9% sterile NaCl were filtered through sterile 0.45-μm membrane filters (Millipore, Darmstadt, Germany). The membrane was placed either on plate count agar enriched with cetrimide (2 g/L) or on trypticase soy agar (TSA) enriched with amoxicillin (10 mg/L). Sponges, reused soaking container, probe, gel, plastic cases, and drain swab samples were first enriched with 10 mL of TSB supplemented with either cetrimide or amoxicillin for 48 h at 30°C or with BHI supplemented with aztreonam for 72 h at 37°C. One drop of each enrichment culture (i.e., TSB and centrimide, TSB and amoxicillin, and BHI and aztreonam) was respectively plated on TSA supplemented with cetrimide; on TSA supplemented with amoxicillin and incubated for 48 h at 30°C; and on MacConkey agar and incubated for 48 h at 37°C. Count Tact Agar plates were incubated for 7 days at 30°C.

Isolates were identified phenotypically by API 20NE and API 20E strips (bioMérieux) for non-Enterobacteriacae and Enterobacteriacae, respectively. Identification was confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with the VITEK MS system (bioMérieux).

The macrorestriction profile of the total DNA of the clinical and environmental isolates was charted by pulsed-field gel electrophoresis (PFGE) (CHEF-DR III, Bio-Rad, Hercules, California), as described (16). XbaI and SpeI served as restriction enzymes for A. xylosoxidans and O. anthropi, respectively. We ensured that the gels were comparable by including Staphylococcus aureus strain NCTC 8325 (including SmaI as the restriction enzyme) for reference. We compared PFGE patterns by visual inspection.

Statistical Analysis

Descriptive statistics, including median and interquartile ranges, were computed for quantitative variables. Categorical data were compared by using the Fisher exact test and quantitative data by using the Mann-Whitney U test. Statistical analysis was conducted with R statistical software (17). All tests were 2-tailed, and p values <0.05 were considered statistically significant. Logistic regression was performed with general linear models with bias reduction as implemented in R, brglm (18,19). Multiple logistic regression that used an entry threshold of p = 0.15 and a backward elimination cutoff of p = 0.05 searched for factors that correlated independently with infection. Interactions between variables in the resulting model were also tested.

Clinical Course

We identified 8 confirmed case-patients: 1 was biopsied on August 13, 2014; the other 7 were biopsied during September 12–October 10 and were evenly distributed during that period. An additional 2 possible case-patients with no microbiologic evidence of infection were biopsied on October 6 and 7 (Table 1). On the basis of confirmed cases, the attack rate during August 13–October 10 was 9.4% (8/85 patients). At the height of the outbreak (i.e., September 12–October 10), the rate was 13.2% (7/53). These rates compare with a baseline long-term rate of 1.4% (27/1,927 patients) for endogenous postbiopsy infections, which are defined as cultures collected <15 days postbiopsy and growing no environmental bacterial strains (determined from hospital records for January 2011–August 2014).

Of the 10 confirmed and possible case-patients, 6 were hospitalized. None were in intensive care, and all recovered fully. Five patients were infected with an A. xylosoxidans strain resistant to ceftriaxone and ofloxacin; 3 of these patients reached apyrexia within 48 hours of treatment initiation with ceftriaxone (2 g/24 h), ofloxacin (400 mg/24 h), or both, as first-line regimens, despite the in vitro resistance to these agents. Three patients had O. anthropi infection; 1 received no curative antimicrobial drug treatment. The first outbreak patient (biopsied on August 13) had O. anthropi bacteremia and was a kidney-transplant recipient. The 2 possible case-patients with no identifiable culture also recovered quickly.

Onsite Investigation

Facility inspection and a review of practices identified mistakes in the sterile handling of sponges, which were sometimes accidentally touched by an aide with contaminated hands (aide 1 in Table 2). The container in which the sponges were soaked was reused from day to day, reportedly for up to several weeks. The container was commonly left overnight with sponges inside and never completely dried during the course of use. Other practices causing risk included application of nonsterile gel on the outer layer of the ultrasound probe and lack of a proper log of probe disinfection procedures.

The plastic container was identified as a likely source of environmental contamination of the biopsy needle, with bacteria being spread by the sponges. The container was immediately taken for microbiologic examination and replaced by sterile single-use cups. Biopsies continued to be performed while the investigation continued.

Samples were also collected from the sterile saline flask periodically used to refill the container and from the plastic cases; sponges (dry and soaked); ultrasound gel; transducer probe; tap water; and biopsy room environment (i.e., worktop, sink, and drain). A total of 52 samples were collected from 20 soaked sponges, 6 dry sponges, 2 plastic cases, 1 NaCl 0.9% flask, 1 ultrasound gel bottle, 4 water samples, and 18 surfaces.

Microbiologic Studies and Molecular Typing

Figure 2

Figure 2. Pulsed-field gel electrophoresis of clinical and environmental strains of Achromobacter xylosoxidans and Ochrobactrum anthropi infections in patients after undergoing prostate biopsies at Hôpital Édouard Herriot, Lyon, France. Patient numbers match those...

All samples tested negative except for sponges retrieved from the saline-filled plastic container; those samples tested positive for 5 bacterial species: A. xylosoxidans, O. anthropi, Stenotrophomonas maltophilia, Roseomonas mucosa, and Enterobacter cloacae. Neither the dry sponges nor the sterile NaCl 0.9% flask used to soak them was contaminated. Of the 5 bacterial isolates, only A. xylosoxidans was resistant to fluoroquinolones. PFGE confirmed that all 5 patients infected by A. xylosoxidans were contaminated by the same strain (Figure 2). However, the clinical and environmental O. anthropi isolates had different PFGE profiles.

Infection Control Measures and Outbreak Termination

On the day of the alert, investigators conducting facility inspection identified the plastic container as a potential hazard and removed it from use. Beginning the following morning, the sponges were soaked in sterile cups, and a new cup was used for each patient. In early 2015, all sponges were systematically sterilized before being placed for soaking in sterile single-use cups. Radiology staff were retrained in clean and sterile handling of materials. No microbiologically confirmed infections occurred during October 10, 2014–March 30, 2015.

Case–Control Study

Case–control investigation determined that among potential risk factors considered (Table 2), first procedure of the day and identity of the main operator were associated with increased infection risk (adjusted odds ratio 14.5 [95% CI 2.49–558] and 8.49 [95% CI 1.55–104], respectively). No other significant differences between case-patients and control-patients were apparent; an interaction term variable was also considered and was not statistically significant. A sensitivity analysis, whether it included possible cases or excluded August cases and controls, retained the same variables in the final model (data not shown).

Retrospective Surveillance

After being informed by radiology staff of prolonged sporadic reuse of the plastic containers, we reviewed databases for January 2011–August 2014 for TUPBs and blood or urine cultures, looking for past cases involving 1 of the 5 species isolated from the container or other rare, environmental, waterborne pathogens. For 32 (1.7%) of 1,927 patients undergoing the procedure, a blood or urine sample was taken <15 days after the biopsy. Overall, cultures for 23 of the 32 patients were negative; among the other 9 patients, 2 had positive urine cultures with >2 bacteria (suggesting contamination by digestive flora), 1 had Klebsiella pneumoniae, 1 had E. coli, 1 had O. anthropi (patient 1 from Table 1), and 4 had S. maltophilia (1 of the 5 species found in the container) (Table 3).

During 2011 and 2012, four S. maltophilia cases clustered in 2 pairs, for which TUPBs occurred 19 days and 45 days apart. The first pair of patients had identical antibiograms, indicating that they were likely infected by the same strain. Minor differences were found in the antibiograms of the second pair. All strains were resistant to fluoroquinolones and third-generation cephalosporins. No complications occurred. All 4 patients were the first to undergo a biopsy on the day of their procedure.