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A Pseudo-Outbreak Associated with Contaminated Sterile Compounded Drugs

A recent research brief published in Infection Control & Hospital Epidemiology by colleagues at Johns Hopkins¹ brings to light that contaminated sterile compounded drugs can cause pseudo-outbreaks as well as outbreaks that impact on patient care. A simple definition of a pseudo-outbreak is: An episode of increased disease incidence due to enhanced surveillance or other factor not related to the disease under study. In other words, the episode does not increase the burden of disease in the population at risk, but the population at risk can still be adversely impacted due to unnecessary interventions based upon the results of the laboratory tests that are acted upon by clinicians in error.

The epidemiology team at Johns Hopkins were alerted by the microbiology laboratory to a cluster of Sphingomonas spp. growing in mycobacterial cultures of bone marrow aspirate samples from adult patients with hematological malignancies. Between May and August 2010, 4 bone marrow cultures grew Sphingomonas and 1 bone marrow culture grew Methylbacterium. An outbreak investigation was then initiated, which included observations of the bone marrow procedure and subsequent sampling of relevant environmental areas.

A bone marrow procedure cart was utilized for each case consisting of all the necessary equipment for bone marrow extraction, including heparin-saline syringes. Prior to May 2010, the laboratory staff used commercially prepared heparin-saline syringes. However, due to a shortage, the providers started to use in-house prepared heparin-saline syringes. The need for a concentration of 100 USP units/ml heparin meant that they diluted 1000 USP units/ml with normal saline. The normal saline utilized was a single-dose irrigation solution, not meant for medication preparation, and designed to be discarded after first use. This single-dose saline solution was accessed repeatedly until empty by the laboratory, and the final heparin-saline solution was used to coat the inside of the sterile syringes prior to bone marrow aspiration.

Cultures of all 4 heparin-saline syringes sampled grew Sphingomonas spp.; three of 4 syringes also grew Methylobacterium, as well as 1 bag of in-use normal saline and 5 sink/water samples. Further molecular typing confirmed an association between these bone marrow isolates and the heparin-saline solution isolates. The bone marrow laboratory suspended their heparin-saline solution compounding practices, and the pharmacy provided a commercial preparation of heparin-saline solution. Bone marrow aspirate cultures since that time have not grown either organism. As is common in outbreak investigations, the precise source of the outbreak could not be determined with certainty; however, the hospital water system and sinks may have served as a reservoir, combined with the lapses in aseptic technique and proper engineering controls as the likely cause of this pseudo-outbreak.

Pseudo-outbreaks can result in unnecessary antibiotic treatment, as was seen in one patient in this investigation. These findings highlight the importance of carefully reviewing all procedures in patient care areas related to the use of pharmaceutical agents and ensuring re-education on the best infection control practices, which includes monitoring for full compliance with USP Chapter 797 standards (as well as the new USP Chapter 800 Hazardous Drugs just released.) Following appropriate standards related to sterile compounding of pharmaceuticals is not just limited to the pharmacy, but extends to all of patient care.

When was the last time you have conducted Clinical Rounds on patient care areas with particular attention to the safety of pharmaceutical agents used for diagnostic testing protocols (e.g., bone marrow aspiration syringes), as well as the safety of drugs administered to patients?

References

¹Pseudo-outbreak of Sphingomonas and Methylobacterium sp. Associated with Contamination of Heparin-Saline Solution Syringes Used During Bone Marrow Aspiration, C. Rock, et.al, ICHE(37) 1, January 2015, pp. 116-117.

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