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Food Safety Focus (86th Issue, September 2013) – Incident in Focus

Clostridium botulinum in Powdered Formulae for Infants and Young Children

Reported by Ms. Janny MA, Scientific Officer,
Risk Assessment Section,
Centre for Food Safety

Last month, the New Zealand Ministry for Primary Industries (MPI) announced that some batches of whey protein concentrate produced by Fonterra were potentially contaminated with Clostridium botulinum (C. botulinum). The concerned products were sold and mixed with other ingredients to form various food products including powdered formulae for infants and young children. In Hong Kong, a brand of follow up formula was recalled as a precautionary measure. This article discusses the risk of C. botulinum in powdered formulae.

C. botulinum and Botulism

C. botulinum is a bacterium that produces heat-resistant spores which are widely distributed in the environment. When the conditions become favourable, for example in the absence of oxygen, the spores germinate, grow and excrete dangerous neurotoxins that can cause a rare but potentially fatal illness called botulism.

Foodborne botulism is caused by the ingestion of pre-formed toxin in contaminated food. Common implicated foods include lightly preserved foods and inadequately processed canned or bottled low-acid foods such as home-canned low-acid vegetables and vacuum packed meat and fish products.

On the other hand, intestinal botulism (formerly infant botulism) is caused by the ingestion of C. botulinum spores which germinate in the intestine and release toxin. Intestinal botulism rarely happens in persons over one-year-old as better developed natural microbiological flora in the intestine do not favour the germination and growth of the bacteria. There are several possible sources of intestinal botulism and spore-contaminated honey has been implicated in a number of cases in infants. Hence, it is recommended not to feed honey to infants less than one-year-old.

Locally, there has been no case of botulism recorded in Hong Kong since this disease was made statutory notifiable on 14 July 2008. Prior to that, one suspected case of botulism was recorded in 2007 but no implicated food could be identified.

C. botulinum
C. botulinum survives in form of spores under adverse conditions. If the conditions become favourable, the spores germinate into bacteria, grow and produce toxin. Photo by courtesy of the US Centers for Disease Control and Prevention.

C. botulinum Risk in Powdered Formulae

Powdered formulae for infants and young children are not sterile products and may be contaminated with pathogens that can cause serious illness.

In general, using hot water no less than 70oC to make up powdered infant formula (PIF) can kill certain harmful bacteria like Cronobacter sakazakii. However, this practice can neither destroy toxin nor spores produced by C. botulinum since such toxin can only be destroyed by boiling for ten minutes or longer while inactivation of the spores requires much higher temperature.

Having said that, the Food and Agriculture Organization of the United Nations and the World Health Organization consider that the causality between the illness caused by C. botulinum and PIF consumption is less plausible or not yet demonstrated. Although C. botulinum has been identified in PIF, it has not been implicated as causing illness in infants.

The Evolvement of the Incident

According to MPI's investigation on the incident, the contamination of the concerned whey protein concentrate occurred when it was processed through a temporary connection pipe which had been contaminated.

Initially, the whey protein concentrate had produced test results suggesting the presence of spores of C. botulinum. However, subsequent validation conducted by MPI and the US Centers for Disease Control and Prevention confirmed that the bacterium was not C. botulinum but another Clostridium species which is not pathogenic. In view of the latest finding, MPI confirmed that there was never a food safety risk associated with the concerned products and the precautionary advisory of these products has been revoked.

Actions Taken by the Centre for Food Safety (CFS)

Upon receipt of the information that certain powdered formulae potentially contaminated with C. botulinum were available in Hong Kong, the CFS took prompt actions including issuing food alert and press release , setting up designated hotline, liaising with the New Zealand authority and the local trade etc.

As a precautionary measure, the CFS also took ad hoc dairy product samples for children aged under one-year-old manufactured in New Zealand to test for C. botulinium. Results were all satisfactory.

Key Points to Note:

Advice to the Public

  1. Caretakers should follow the “ Guide to Bottle-feeding ” published by the Department of Health when reconstituting PIF. Although the guide is not targeted to address C. botulinum, it provides general safety advice on preparing powdered formulae for infants.
  2. Use hot water no less than 70oC to make up PIF. Even it cannot destroy C. botulinum toxin or spores, it kills certain pathogens of concern.

Advice to the Trade

  1. Ensure foods imported and for sale are fit for human consumption.
  2. Obtain food and food ingredients from reliable sources.
  3. Manufacturers of powdered formulae should refer to relevant Codex guidance and recommendations on hygienic manufacture of powdered formulae for infants and young children.