Friday, July 21, 2017

Laboratory Related Salmonella Outbreak - A Reminder about Pathogen Control for Those Doing Testing

CDC is reporting that 24 people in 16 states have become ill with an outbreak strain of Salmonella Typhimurium.  A few important points for facilities that are doing their own testing:
  • Laboratories need to have and adhere to strict cleaning and sanitizing protocols.  There is a lot of emphasis on cleaning and sanitizing in the food production facilities, but unfortunately, this may not be as strictly enforced in the laboratories.  
  • Laboratories located in food production facilities need to recognize they are a high risk source for pathogens, especially if those laboratories are using methods that enrich for pathogens such as Salmonella or Listeria.  Laboratories need to verify cleaning through environmental monitoring.  Control of access for people and materials in and out of the laboratories must be in place.
  • Pathogens are highly infectious, so people working in the laboratories must adhere to proper personal hygiene protocols.  Not only can these pathogens represent a risk to food produced, but there is also a risk for laboratory workers as well as family or friends of those workers.
We have all seen laboratories where too much is taken for granted.  That is, cleaning off the bench top or keeping it under the hood is all that one needs to do.  But when working with bacteria that are, or may be pathogens, a test tube, a petri dish, or sample card can have levels in the millions of cells per gram or ml.  Considering it may take as few as 10 cells or less to make someone ill, it is easy for a small amount to make it past rudimentary cleaning procedures.  (I know, there are some of you that used to mouth-pipet this stuff).

Infection Control Today
Human Salmonella Typhimurium Infections Linked to Exposure to Microbiology Labs
July 19, 2017

The Centers for Disease Control and Prevention (CDC) and public health officials in several states have identified a multistate outbreak of Salmonella Typhimurium infections linked to various clinical, commercial and teaching microbiology laboratories. Twenty-four people infected with the outbreak strain of Salmonella Typhimurium were reported from 16 states. Six ill people were hospitalized. No deaths were reported.

This strain of Salmonella Typhimurium has previously been associated with infections linked to microbiology laboratory exposure in 2011 and 2014. Laboratory-associated salmonellosis continues to be a public health problem. This outbreak is a reminder that bacteria used in microbiology laboratories can sicken people who work in labs. Others who live in their households can also get sick, even if the household members never visited the laboratory.

Public health investigators used the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet, coordinated by CDC, is the national subtyping network of public health and food regulatory agency laboratories. PulseNet performs DNA fingerprinting on Salmonella bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks.

Twenty-four people infected with the outbreak strain of Salmonella Typhimurium have been reported from 16 states, including California, Colorado, Florida, Georgia, Iowa, Maine, Michigan, Missouri, North Carolina, New Hampshire, New Jersey, New Mexico, New York, Oklahoma, Texas, and Washington. WGS showed that the strain of Salmonella Typhimurium causing illness in this outbreak is closely related genetically to a strain from an outbreak in 2014 and an outbreak in 2011, both of which were linked to microbiology laboratories. As a result of the 2011 outbreak, several laboratory professionals across the country developed a set of guidelines for handling microorganisms safely in a teaching laboratory.

Among people for whom information was available, illnesses started on dates ranging from March 17, 2017 to June 22, 2017. Ill people ranged in age from less than one year to 57 years, with a median age of 24. Seventy-five percent of ill people were female. Among 21 people with available information, six (29%) were hospitalized. No deaths were reported.

In interviews, ill people answered questions about different exposures in the week before they became ill. Nine (69%) of 13 ill people had laboratory exposures. Ill people in this outbreak reported behaviors while working in the laboratory that could increase the risk of Salmonella infection. These included not wearing gloves or lab coats, not washing hands, and using the same writing utensils and notebooks outside of the laboratory.

This outbreak highlights the potential risk of Salmonella infection associated with working in microbiology laboratories.

All students and staff in clinical and teaching microbiology laboratories should receive laboratory safety training. Either nonpathogenic or attenuated bacterial strains should be used when possible, especially in teaching laboratories. This practice will help reduce the risk of students and their family members becoming ill.

Source: CDC

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