Pregnancy, protein and listeria: are mums-to-be ‘too cautious’ on risk foods?

"How long have you been pregnant,” I asked the thirty-something as we filled our plates during the catered lunch at a meeting in 2000 in Ottawa.

“About six weeks.”??

The American media had been filled with coverage of listeria after the 1998-1999 Sara Lee Bil Mar hot dog outbreak in which 80 were sickened, 15 killed and at least six pregnant women had miscarriages. Risk assessments had been conducted, people were talking about warning labels, and especially, the risks to pregnant women. ??There was no such public discussion in Canada.?? So as I watched the pregnant PhD load up on smoked salmon, cold cuts and soft cheese for lunch, I wondered, do I say something?

One of the biggest risks in pregnancy is protein deficiency. What if smoked salmon, cold cuts and soft cheeses were this woman’s biggest source of protein? (Turns out they were.)?? Another risk factor is stress. I didn’t want to freak her out. Besides, who the hell am I to say anything? ??We sat together during lunch and chatted about babies, her aspirations and how she was feeling. Eventually I introduced the subject of listeria by talking about a risk assessment that had recently been published by the U.S. Food and Drug Administration, and that maybe she would be interested in looking at the results. I felt sorta goofy.
Professor Clare Collins of the University of Newcastle studied the eating habits of 7000 Australian women to see if they were missing out on important nutrients as a result of avoiding "risky" foods that potentially carried listeria.

9News reports some pregnant women are being overly cautious about avoiding what are traditionally considered "no-no" foods, such as soft cheese, pate and sashimi, a researcher says. Oysters, smoked fish, delicatessen meats, salad bar salads and pre-cut fruit are also considered high risk for carrying the Listeria monocytogenes.

Reporting her findings in the journal Public Health Nutrition, Prof Clare said her study found that women who ate the most listeria foods reported more frequent miscarriages, but had high levels of the nutrients needed to have a healthy baby.

Conversely, those who ate moderate or low amounts of listeria foods had less miscarriages but also lower levels of nutrients like calcium, folate and Omega 3 acids.

"In those with moderate and low exposure there was no excess risk of miscarriage but the problem was their nutrient intakes were then worse," Prof Clare said.

"We’re saying pregnant women need to be given more advice on how to eat healthy. If all they hear is risky foods, and they drop out all the potential listeria foods, their micro nutrient intake is going to be really bad.”

She said the existing listeria guidelines for pregnant women were entirely legitimate but needed to be rewritten to provide more information about what could be eaten, as well as what should be avoided.

There were 65 cases of listeriosis in Australia in 2008, 12 during pregnancy and one that was fatal.

Targeted microarray analysis of stationary phase Escherichia coli O157:H7 subjected to disparate nutrient conditions

Getting graduate students to publish their research in peer-reviewed journals is often painful. As a supervisor, I sucked at it for years, but am now more draconian.

I’m pretty sure Kevin Allen (right, exactly as shown) got some award for this research at the International Association for Food Protection meeting in Baltimore in 2005, so good to see the hockey goon finally got it published in the Journal of Applied Microbiology. (And if these details are wrong, write in and correct them; it’s a blog.)

K.J. Allen, D. Lepp, R.C. McKellar, M.W. Griffiths
Aims:  To determine how stress response and virulence gene expression of stationary phase (SP) Escherichia coli O157:H7 are affected by nutrient levels.

Methods and Results:  A targeted microarray (n = 125 genes) was used to determine the impact of nutrient deprivation [15 min in 3-(N-Morpholino)propanesulfonic acid buffer] on SP E. coli O157:H7. In total, 24 genes were significantly affected (>1·5-fold; P < 0·05) with 17 induced and seven attenuated. Additionally, 11 genes belonging to significantly affected stress response regulons were significantly induced (P < 0·05), though <1·5-fold. Induced genes included global and specific stress response regulators, the mar operon, iron acquisition and virulence genes. In contrast, transcript for major porins and replicative genes were repressed. Comparison of the nutrient deprived transcriptome to that derived from nutrient replenished cells revealed a disparate transcriptome, with 44 genes expressed at significantly elevated levels in nutrient replenished cells, including all queried global and specific stress response regulators and key virulence genes. Genes expressed at elevated levels in nutrient deprived cells were related to σS. The microarray data were validated by qRT-PCR.

Conclusions:  SP E. coli O157:H7 were affected by nutrient deprivation, with both starvation-related and unrelated networks induced, thereby demonstrating how the E. coli O157:H7 stress response transcriptome is fine-tuned to environmental conditions. Further, by comparison of starved cells to cells provided with fresh nutrients, it is clear starved E. coli O157:H7 undergo massive physiological reprogramming dominated initially by stress response induction to adapt to a nutrient rich environment.

Significance and Impact of the Study: This study demonstrated how σS-induced SP E. coli O157:H7 remain highly sensitive and adaptable to environmental conditions. Further, by examining how starved cells respond to nutrient-rich conditions, we show preliminary adaptation to a nutrient rich environment is dominated by the induction of diverse stress response networks. Combined, this provides E. coli O157:H7 stress physiology-based knowledge that can be used to design more effective food safety interventions.