Background: Most outbreak investigations involve short-term, geographically localized clusters. However, some organisms can form environmental reservoirs leading to more prolonged, widespread outbreaks. We describe a prolonged outbreak of Bu at our institution.
Methods: An epidemiological investigation was conducted. Bu isolates were genotyped using pulsed field gel electrophoresis (PFGE) and recA gene sequencing. Initial isolates were sent to a national reference laboratory for multilocus sequence typing (MLST).
Results: 32 patients on 12 units (see Figure) had ≥ 1 positive culture for Bu from 6/2017-2/2018. 21 had B. cenocepacia (PFGE pattern A, recA allele 365) and 11 had B. cepacia (PFGE pattern C, recA allele 53). MLST revealed that isolates with recA allele 365 were unique compared with previously identified B. cenocepacia strains. 28/32 (88%) patients had positive respiratory cultures. 3/32 (9%) patients had bacteremia. 30-day mortality was 4/29 (14%). A case control study did not reveal a common point source. All surveillance cultures from asymptomatic patients were negative (n = 53). 2/9 sink drains in rooms of cases were positive for an unrelated strain of B. cepacia. Other environmental cultures were negative for Bu (n = 49). Cases continued despite routine interventions (see Figure), with some incident cases detected long after potential exposures. Ventilator/respiratory equipment (V/RE) cleaning was investigated. Multiple V/RE interventions were implemented: 1) ensuring a sterilization process for ventilator temperature probes (used in heated humidification) was occurring; 2) using disposable manometers on contact isolation patients; 3) reinforcing ventilator cleaning, including those in radiology suites after use.
Conclusion: No definitive source of the outbreak was found. New cases continued after reinforcement of basic infection control practices, but subsided after focused attention on V/RE cleaning practices. Control of this outbreak was challenging due to the complexity of a prolonged latency period for Bu, difficulty identifying reservoirs, and multiple possible modes of transmission, especially for organisms like Bu that can persist on environmental surfaces and equipment.
M. Oberhardt, None
D. Green, None
F. Wu, None
S. Whittier, None
L. Saiman, None
E. Y. Furuya, None