April 22, 2014 — A bacterial infection and potential outbreak were identified in May, 2007, in the neonatal intensive care unit (NICU) of a medical facility in Toronto (Canada).[1-4]

A two-week old prematurely born infant weighing between 1 and 3 pounds was infected with Serratia and died of bacteremia, which is an infection of the blood.

Four other “palm-sized” infants receiving treatment in this NICU also tested positive for Serratia, but none has displayed symptoms of infection, suggesting colonization (or a pseudo outbreak of Serratia).[3,4]

Among other infection-control measures, the medical facility temporarily closed its NICU as part of an aggressive strategy to prevent additional infections.

Newspaper reports indicate that this infection and potential outbreak were identified at a time when the medical facility has acknowledged that its NICU is overcrowded and in need of renovation,[1,4]

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What are Serratia?

Serratia are opportunistic bacteria that have been linked to outbreaks in NICUs. They are often found in the intestinal flora of adults and sometimes infants.

Serratia are members of the Enterobacteriaceae family and include Serratia marcescens, S. liquefaciens, and S. odorifera. Those that are resistant to  carbapenem antibiotics are “superbugs” known as CRE.

Serratia are transmitted through direct and indirect contact (not via large-particle droplets or airborne droplet nuclei), and ordinarily do not cause infection in healthy patients.

As this recent infection in Toronto demonstrate, infections of Serratia can be associated with significant morbidity and mortality among premature infants (and other immuno-compromised or critically-ill patients).[1-4,7-12]

Most healthcare-acquired infections of Serratia are caused by S. marcescens, suggesting that this may be the species of Serratia responsible for this recent infection and potential outbreak in a NICU in Toronto.[6]

Proper hand hygiene is important to prevent the healthcare-associated transmission of Serratia.  The symptoms of Serratia infection include fever, shock, and respiratory distress.

In addition to Standard Precautions, Contact Precautions may be necessary to prevent the spread of Serratia and other epidemiologically important infectious agents in NICUs.

More details about the Toronto outbreak

Many aspects of this NICU’s infection and potential outbreak are unclear and have not been published, but a number of newspaper  articles that discussed this incident reported that the medical facility’s NICU is overcrowded and provides insufficient space between incubators, increasing the risk of disease transmission.[1-4]

To date, however, the cause of this infection and potential outbreak of Serratia has not been determined. It is unclear whether the strain of Serratia responsible for this incident is multidrug-resistant, or whether any of the infants in this NICU were suffering from acute diarrhea.

Read Dr. Muscarella’s related article, “Isolation Precautions for the prevention of the transmission of Ebola and other infectious agents in the healthcare setting.”

More about Serratia

Outbreaks of S. marcescens in NICUs have been associated with significant morbidity and mortality, including septicemia, pneumonia, meningitis, urinary tract infection, and conjunctivitis.[8-24]

Investigations of the causes of these and other outbreaks of Serratia often conclude that poor hand hygiene of healthcare staff members was most likely responsible for disease transmission.[16,17,19-22,24]

It would not be surprising to learn, therefore, that officials investigating this recent infection of Serratia in the NICU of a medical facility in Toronto determined that the hands of the healthcare staff members were colonized and responsible for the transmission of the Serratia among the infants.[1-4]

The newspaper articles that first reported this incident would appear to agree, having implied that:

  • the reservoir of this infection of Serratia was likely the intestines of one or more of the infants (and/or staff); and
  • the hands of healthcare staff members were likely responsible for transmission of the infectious strain of Serratia in this reportedly overcrowded NICU.[1-4]


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A “misdiagnosis”?

Whether improper hand washing or poor hand hygiene was responsible for transmission of Serratia in this NICU in Toronto remains unclear.

But, it could result in a “misdiagnosis” of the true source and mode of transmission of the Serratia in this NICU, if the investigation limited consideration of the reservoir of Serratia to the intestines of neonates (or staff) and the spread of the Serratia to the hands of healthcare staff members.

Dr. Muscarella discusses the transmission of Serratia and other multidrug-resistant bacteria in his related article, “Investigation and prevention of ‘superbug’ outbreaks following endoscopy.”

To be sure, the intestines are not Serratia’s only healthcare-associated source or reservoir, and, to be sure, transmission of Serratia is not restricted to the hands of healthcare staff members.

In addition to their intestines, Serratia may colonize the respiratory and urinary tracts of hospitalized patients, and Serratia–namely, S. marcescens–are ubiquitous in the environment and have been found in soil and water and on moist surfaces.6,7,20,24

Proper reprocessing of reusable medical devices is necessary to prevent the transmission of Serratia, as are proper hand hygiene and the routine cleaning and disinfection of environmental surfaces.

Potential sources and reservoirs of a Serratia outbreak

These findings highlight important characteristics of Serratia and raise the possibility that a source other than the hands of health staff members—namely, a reusable medical device—may have been responsible for this recent infection and potential outbreak of Serratia in a NICU.

Although infected or colonized infants are often identified as sources for horizontal transmission of Serratia via the (transiently colonized) hands of healthcare staff members,[16,17,19-21,22,24] the failure to consider potential sources other than infants’ intestines and vehicles for the transmission of Serratia other than the hands of healthcare staff members might delay — if not prevent — the identification of the source and cause of an outbreak of Serratia.

It might also prevent the timely implementation of infection-control measures crucial to interrupt the transmission of Serratia among infants in a NICU.

In addition to the hands of healthcare staff members, outbreaks of S. marcescens in NICUs have been linked to contaminated rigid laryngoscopes and incubators, as well as to contaminated sinks, water faucets, and other wet environmental surfaces.[6-12,14-16,20,23]

Moreover, the consumption of contaminated tap water during the administration of an oral medication has been linked to the infection and colonization of patients with multidrug-resistant S. marcescens.[7] Disease transmission was not controlled until a contaminated water faucet was replaced.

Outbreaks of Serratia have also been linked to the administration of contaminated intravenous (IV) fluids, solutions, and medications.[25-27]

Read Dr. Muscarella’s related peer-reviewed article, “Infection control and its application to the administration of intravenous medications during gastrointestinal endoscopy.”

If the source of the Serratia in the NICU of this medical facility in Toronto were a contaminated rigid laryngoscope or incubator, or a contaminated sink or tap water, then the implementation of special infection-control measures in addition to Standard Precautions — specifically, gloving and hand hygiene per Contact Precautions — might do little to prevent additional infections.

For example, if a faucet were colonized with Serratia and contaminating rigid laryngoscopes during washing and terminal water rinsing, then implementation of Contact Precautions would not be expected to prevent the spread of Serratia.[7]

The prompt determination of the cause of an infection or outbreak of Serratia requires consideration of all of the possible sources of Serratia.

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Rigid laryngoscopes, incubators 

Improper reprocessing of rigid laryngoscopes has been linked to outbreaks of Serratia in NICUs.

Cullen et al. reported that inadequately reprocessed laryngoscope blades (and possibly an incubator) were likely the source of an outbreak of S. marcescens in a NICU.[13] Four infants were infected, two of whom died.

Similarly, Jones et al. reported an outbreak of S. marcescens in two NICUs caused by a contaminated laryngoscope blade (and expressed breast milk).[14] Seventeen neonates were colonized, three developed septicemia, and two died.

In addition to S. marcescens, outbreaks of Pseudomonas aeruginosa in NICUs have been linked to contaminated rigid laryngoscopes. A recent public health notice provides instructions for reprocessing rigid laryngoscopes.[11]

Outbreaks linked to contaminated incubators have also been published. Jang et al. reported an outbreak of S. marcescens linked to the doors of incubators and contaminated handwashes.[20] The potential for outbreaks of P. aeruginosa as a result of contaminated incubators also has been discussed.[30]


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Recommendations

Several more recommendations are provided to control and prevent the transmission of Serratia in a NICU. These recommendations are provided in a more complete version of this article.

Many of these recommendations — which are key components of Contact Precautions — also apply to other healthcare settings (e.g., ICUs) and to other epidemiologically important infectious agents transmitted by direct or indirect contact.

The importance of properly reprocessing bronchoscopes and gastrointestinal (GI) endoscopes is underscored, because these type of flexible endoscope — like rigid laryngoscopes and incubators — have been linked to outbreaks (and pseudo-outbreaks) of Serratia.[31-37]

This article’s references are available by clicking here.


Article by: Lawrence F Muscarella PhD posted on 1/16/2013; updated 11-3-2015, Rev A.

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