804 infection control & hospital epidemiology july 2017, vol. 38, no. 7
table 1. Pseudomonas aeruginosa Outbreak in a Neonatal Intensive Care Unit Attributed to Hospital Tap Watera Characteristics
Case Patients, Male
Mean days of life at first positive culture or index culture Mean gestational age, weeks Mean birth weight, g Birth weight ≤1,000 g
Race/Ethnicity (N=31 cases, 30 controls) Non-Hispanic white Non-Hispanic black Hispanic Other
1,001–1,500 g 1,501–2,500 g ≥2,501 g
Small for gestational age (<10th percentile)c Cesarean birth Multiple birth
Medical history Pulmonary disease
Patent ductus arteriosis
Intraventricular hemorrhage Eye exam
Retinopathy of prematurity treatment Gastrointestinal surgery Cardiac anomalies
No. (%) or Mean (range) 16 (52)
7 (23) 6 (19)
18 (58) 0 (0)
28.1 (1–76)
28.0 (23.0–37.4) 1,183 (485–3,310)
16 (52) 7 (23) 6 (19) 2 (6) 1 (3)
24 (77) 6 (19)
27 (87) 10 (32) 6 (19) 3 (10) 1 (3) 1 (3) 1 (3)
period 7 days before positive culture or incident date. bCalculated using exact conditional logistic regression with pooled matched strata. cCalculated using Fenton 2013 criteria.19
to become contaminated. After the second cluster of cases began in June 2014, POU filters were reinstalled on NICU faucets September 23, 2014, per our recommendation. A company contracted by the hospital sampled prefiltered water monthly from November 2013 to January 2014, and during May 2014 to detect P. aeruginosa. Multiple samples grew P. aeruginosa, with high colony counts occurring in May 2014, before faucet replacement; however, no PFGE matcheswere identified among environmental and patient isolates. In conjunction with hospital engineering staff, we also evaluated the plumbing system for terminal dead ends and areas of poor water flow leading to the NICU; none were found. Pseudomonas aeruginosa was isolated from 28 of 42 (67%)
environmental samples collected by our CDC team in September 2014. Of 32 samples of tap water and biofilms associated with tap water (eg, faucet, drain, and sink basin), 27 (84%) were positive for P. aeruginosa (Table 2). PFGE analysis of CDC environmental samples and patient
isolates sent to theCDClaboratory revealed 4 unrelated groups of environmental and patient isolates with indistinguishable PFGE patterns (Figure 4). Isolates from 2 case patients were indistinguishable by PFGE from environmental isolates collected in the rooms occupied by each case patient.
Risk Factors: Case-Control Study
After adjustment for gestational age, case patients had higher odds of exposure to a peripherally inserted central catheter (PICC) (exact odds ratio [eOR], 7.20; 95% CI, 1.75–37.30) or invasive ventilation (eOR, 5.79; 95% CI, 1.39–30.62), com- pared with controls (Table 3). In addition, case patients had
higher odds of having received care in a room with no POU filter installed on the sink faucet during the 7 days before posi- tive culture (eOR, 37.55; 95% CI, 7.16–∞). All 31 case patients were in rooms without POU filters during the 7 days before positive culture, compared with 14 (45%) control patients.
discussion
Tap water was implicated as the source of a P. aeruginosa outbreak in an NICU that occurred after a new building was opened. Case clusters occurred before POU filters were installed and after they were removed. Residing in a room without a POU filter was the strongest risk factor for having a positive P. aeruginosa culture. POU filter reinstallation inter- rupted the outbreak in the short term. Patients with PICCs or invasive ventilation were also at increased risk.
Controls, No. (%) or Mean (range)
20 (65) 7 (23)
5 (17)
13 (43) 5 (17)
32.1 (1–114)
28.9 (23.3–38.6) 1,325 (610–3,550)
16 (52) 7 (23) 6 (19) 2 (6) 2 (6)
23 (74) 5 (16)
21 (68) 6 (19) 7 (23) 4 (13) 1 (3) 1 (3) 0 (0)
P Valueb .44
1.00 1.00 .38 …
.55 .04 .01 …
…
1.00 1.00
.11 .37
1.00 1.00 … … …
aCharacteristics of case patients (n=31) and controls (n=31) matched by birth weight. Clinical exposures refer to the
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