Monday, January 11, 2016

Do antibacterial soaps and wipes have any effect on antibiotic resistance? Should we use them in the home?

Over the Christmas holiday, our kitchen has fed more people than normal and cleaning has therefore increased.  I have been giving a lot of thought to the possible benefits and risks of using antimicrobial cleaners and soaps.  When you get into this subject, you find it is actually quite complex.

I have written about something similar before, but there is now a lot of published work that suggests that in most cases, there is no benefit to using antibacterial soaps in the home - there is no statistically significant reduction in infectious disease if antibacterial preparations are used in preference to soap and water*.  Nevertheless, in the US alone, nearly $1 billion per year is spent on antibacterial soaps**.

Of course, many infectious diseases are caused by viruses; they are probably not affected by antibacterial compounds, which have a definite target in the bacterial cell.  Thus, an antibacterial soap or wipe will be no better at preventing transmission of cold viruses than a thorough cleaning with soap or detergent and water.

I have recently been asked to review a couple of scientific papers in which evidence is presented that suggests cleaning agents commonly used in the food industry may induce antibiotic resistance in bacteria.  Antibiotic resistance results when bacteria develop enzymes capable of breaking down the active component of the antibiotic.  One of the first instances of antibiotic resistance occurred very soon after the introduction of penicillin.  Bacteria developed the ability to break the beta-lactam ring of penicillin with an enzyme called beta-lactamase.  (Antibiotic resistance genes can often be transferred from one bacterium to another, so in time, many bacterial strains become resistant.)

We already know that many of our antibiotics are no longer effective because of resistance.  Overuse of antibiotics is blamed.  It is ironic that our cleaning agents may also be causing resistance.

But there is another potential driver for antibiotic resistance: sub-lethal exposure of bacteria to certain herbicides have been shown to change antibiotic susceptibility of Escherichia coli and Salmonella enterica serovar Typhimurium***.  This is not a straightforward relationship, but it is clear that there is the potential to select for antibiotic resistance in these bacteria, which, if transferred to humans by contact with animals and food, can potentially reduce the effectiveness of antibiotic therapy.

Well, that's fairly heavy for the first post of 2016, but it should cause us to think when purchasing home cleaning agents and soaps, or chemicals for use in agriculture and domestic gardens.

* Effect of Antibacterial Home Cleaning and Handwashing Products on Infectious Disease Symptoms.  Larson, Elaine L;Lin, Susan X;Gomez-Pichardo, Cabilia;Della-Latta, Phyllis.  Annals of Internal Medicine; Mar 2, 2004; 140, 5


*** Kurenbach B, Marjoshi D, Amábile-Cuevas CF, Ferguson GC, Godsoe W, Gibson P, Heinemann JA. 2015. Sublethal exposure to commercial formulations of the herbicides dicamba, 2,4-dichlorophenoxyacetic acid, and glyphosate cause changes in antibiotic susceptibility in Escherichia coli and Salmonella enterica serovar Typhimurium.  
mBio 6(2):e00009-15. doi:10.1128/mBio.00009-15.

Saturday, January 2, 2016

Lies, damned lies, and misinterpretation of the data.

I am constantly amazed by the apparent ignorance and credulity of the general public on matters of food safety and nutrition.  But should I be surprised?   Few people are lucky enough to have studied food technology, food science or nutrition.  Their main sources of information are then the popular press, magazines, television cooking shows and the all-pervasive Internet. 

Scientists and engineers know that the best sources of information are peer-reviewed papers published in international journals.  Experts in the field have read the paper and picked it apart, looking for poor experimental design, inconsistencies and faulty interpretation of data.  Believe me, I can say this with certainty from both sides of the fence: it is pretty difficult to get a paper published these days!

The other sources of information mentioned above are generally not peer-reviewed.  Articles can be published by people with no formal qualifications in the subject and are often either highly biased or downright wrong.  See:

Sensationalism and sycophantic following of media celebrities are what sell newspapers and magazines.  We see more food scares and wonder diet advice every month without any reference to the original research.

A few examples spring to mind:

Towards the end of October 2015, the WHO International Agency for Research on Cancer stated that processed meats, including hot dogs and sausages would be added to its list of high risk carcinogens.  Red meats were also declared a probable carcinogen.  Needless to say, this caused a furore in all the media.  A Google search, using the terms “sausages cause cancer” returned 469,000 results!  IARC classifications rank the quality of the evidence that something can cause cancer, but don’t assess the level of risk. The announcement was often quoted out of context.  For example, Discovery News baldly stated “Eating sausages, ham and other processed meats causes colon cancer”.  Other reports mentioned the increase in risk as a percentage, but did not state the base level of risk. This scare is enduring; at a barbecue recently, someone noted that I was cooking “cancer sticks”.

Coconut water appears to have been a major drink commodity this year. I have no sales figures, but the sales in 2013 were around half a billion dollars, see  Claims for coconut water include helping with weight loss, improving skin tone and aiding digestion.   Other claims, now withdrawn, stated that it could fight kidney disease, osteoporosis and viruses.  Coconut water contains potassium, calcium, magnesium and phosphorus, which are required minerals.  As a sports rehydration drink, coconut water is definitely unsuitable - when we sweat, we lose lots of sodium.  The ratio of sodium to potassium in sweat is about 10:1, but the ratio of sodium to potassium in coconut water is around 1:3.  Where are the peer reviewed scientific studies of the value of coconut water? They are never quoted.

Critics of the hypothesis that saturated fat consumption is linked with coronary heart disease use the argument that the correlation between total saturated fatty acids and risk factors is not very good.  Unfortunately, the scientific findings have been misinterpretated by the popular press media, with the result that we are told we can eat as much saturated fat as we wish. This advice is incorrect, unethical and irresponsible, see

Despite all the information on food safety available, in my opinion, a large proportion of the population is still badly educated in this regard.  At an outdoor party this week (it's summer in New Zealand) I sat with a very-soon-to-be mother.  She got stuck into the soft cheese in a big way, but said that she would eat it only during the first half hour of its being unwrapped; thereafter it was to be avoided.  In fact, the cheese had been made with pasteurised milk and she was therefore probably safe in eating it, but where had she got this idea from?  I guess she had read about Listeria in soft cheeses, and believed that the bacteria could multiply as the cheese warmed up.  For reliable information on safe foods to eat during pregnancy, see:

I believe that food scientists and food technologists have a duty to provide unbiased and easily digested (sorry!) information to the public in order to help educate them in food safety.  But how can we compete with big advertising budgets and the pronouncements of media celebrities?

I wish all my readers a happy, successful and safe 2016.