About a week ago I was chatting with our contractor – we really spend too much time chatting instead of working, and Amy often intervenes – and somehow we got on about the microbiological risks of cantaloupe (or rockmelon as they call it here).
All states and territories are working together to investigate the outbreak and to date they have identified ten cases in elderly patients in NSW (six), Victoria (one) and Queensland (three) with onset of illness notification dates between 17 January and 9 February 2018. All 10 cases consumed rockmelon prior to their illness.
The outbreak has been linked to a grower in Nericon NSW. The company voluntarily ceased production on Friday 23 February 2018, shortly after being notified of a potential link to illness and is working proactively with the Authority to further investigate how any contamination could have occurred in order to get back into production as soon as possible.
Any affected product is being removed from the supply chain, so consumers can be assured rockmelons currently available on shelves are not implicated in this outbreak, but people may already have listeria-infected rockmelons in their homes purchased at an earlier time.
Contaminated water, fertiliser, contact with animals or insufficient cleaning of rockmelons prior to sale are all risk factors for melons becoming contaminated.
The discovery comes after reports of an outbreak of listeriosis in the Australian state, following an unexpected increase in cases in January and February.
While the link between the farm and the illness cases is not yet conclusive, PMA Australia-New Zealand (PMA A-NZ) said there was sufficient circumstantial evidence to warn at-risk consumers not to consume rockmelon.
“At least 10 people have become infected including three deaths,” PMA A-NZ said in a release. “All cases are people in high risk groups, which includes those who are older, pregnant or have underlying health conditions,”
The NSW Food Authority and NSW Health are currently investigating the outbreak.
Listeriosis is caused by consuming food contaminated with Listeria monocytogenes. Listeria is a bacteria that survives and grows on a number of foods including rockmelon, vegetable salads and fruit salads, cold meats, raw seafood, soft cheeses and seed sprouts.
Saturated steam (SS) treatment was performed at 100 °C and that of SHS at 150 and 200 °C. Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes-inoculated cantaloupes and watermelons were exposed for a maximum of 30 s and 10 s, respectively. Populations of the three pathogens on cantaloupes and watermelons were reduced by more than 5 log after 200 °C steam treatment for 30 s and 10 s, respectively. After SHS treatment of cantaloupes and watermelons for each maximum treatment time, color and maximum load values were not significantly different from those of untreated controls. By using a noncontact 3D surface profiler, we found that surface characteristics, especially surface roughness, is the main reason for differences in microbial inactivation between cantaloupes and watermelons. The results of this study suggest that SHS treatment can be used as an antimicrobial intervention for cantaloupes and watermelons without inducing quality deterioration.
Comparison of the effect of saturated and superheated steam on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes on cantaloupe and watermelon surfaces, Korea, April 2017 to October 2017, Food Microbiology, Volume 72
Nicola Perry of Contagion Live writes that according to new research, applying antimicrobial coatings to whole cantaloupes during storage significantly reduces contamination by pathogenic bacteria, and has the potential to improve their microbiological safety and extend their shelf life.
Qiumin Ma, PhD, from the University of Tennessee in Knoxville, and colleagues published the results of their study in the International Journal of Food Microbiology. Chitosan-based coatings “significantly inhibited the growth of E[scherichia] coli O157:H7, L[isteria] monocytogenes and S[almonella] enterica cocktails on whole cantaloupes during 14-day storage at ambient temperature (21°C),” the authors write. “Coatings also significantly reduced total mold and yeast counts on whole cantaloupes.” Cantaloupes are particularly susceptible to microbial contamination because they grow on the ground and can therefore come into contact with foodborne-pathogens associated with polluted irrigation water, uncomposted manure, or animal droppings. They can also become contaminated during harvesting, handling, and preparation. The rough cantaloupe skin also allows bacteria to easily attach to the surface of the fruit.
“These pre- and post-harvest safety factors have directly or indirectly contributed to more than 25 outbreaks of foodborne illnesses associated with the consumption of cantaloupes between 1973 and 2003 in the United States and Canada,” the authors state.
Food preservation, safety, and quality maintenance therefore represent mounting concerns for the food industry. Antimicrobial food coatings represent just one form of technology that has been investigated as a tool to help improve food safety in various food types, including fresh produce and meats.
Chitosan, derived from the polysaccharide chitin, is known to have film-forming properties as well as antimicrobial activity. Chitosan-based coatings have also been shown to improve food safety—in fresh produce, for example. With this in mind, Dr. Ma and colleagues conducted a study to investigate the efficacy of such antimicrobial coatings in reducing bacterial populations from the surface of cantaloupes. In addition to chitosan, they investigated two generally-recognized-as-safe antimicrobials—lauric arginate (LAE; which inhibits a broad spectrum of foodborne pathogens) and cinnamon oil (CO; an essential oil that has shown activity against Listeria species, gram negative bacteria, E. coli 0157:H7, and Salmonella species). They also investigated ethylenediaminetetraacetic acid (EDTA; an agent that chelates divalent calcium ions that are important to bacterial structures; it also enhances the activity of some antimicrobials).
Cantaloupes, marketed as “Rocky Ford,” were implicated in the U.S. multistate outbreak of listeriosis in 2011, which caused multiple fatalities. Listeria monocytogenes can survive on whole cantaloupes and can be transferred to the flesh of melons.
The growth of L. monocytogenes on fresh-cut “Athena” and “Rocky Ford” cantaloupe cultivars during refrigerated storage was evaluated. Fresh-cut cubes (16.4 cm3) from field-grown cantaloupes were each inoculated with 5 log10 CFU/mL of a multi-strain mixture of L. monocytogenes and stored at 4°C or 10°C. Inoculated fresh-cut cubes were also: (1) continuously stored at 4°C for 3 days; (2) temperature-abused (TA: 25°C for 4 h) on day 0; or (3) stored at 4°C for 24 h, exposed to TA on day 1, and subsequently stored at 4°C until day 3. L. monocytogenes populations on fresh-cut melons continuously stored at 4°C or 10°C were enumerated on selected days for up to 15 days and after each TA event. Brix values for each cantaloupe variety were determined. L. monocytogenes populations on fresh-cut cantaloupe cubes stored at 4°C increased by 1.0 and 3.0 log10 CFU/cube by day 7 and 15, respectively, whereas those stored at 10°C increased by 3.0 log10 CFU/cube by day 7.
Populations of L. monocytogenes on fresh-cut cantaloupes stored at 10°C were significantly (p < 0.05) greater than those stored at 4°C during the study. L. monocytogenes showed similar growth on fresh-cut “Athena” and “Rocky Ford” cubes, even though “Athena” cubes had significantly higher Brix values than the “Rocky Ford” fruit.
L. monocytogenes populations on fresh-cut cantaloupes exposed to TA on day 1 and then refrigerated were significantly greater (0.74 log10 CFU) than those stored continuously at 4°C for 3 days. Storage at 10°C or exposure to TA events promoted growth of L. monocytogenes on fresh-cut cantaloupe during refrigerated storage.
Survival and growth of Listeria monocytogenes on fresh-cut “Athena” and “Rocky Ford” cantaloupes during storage at 4°C and 10°C
Nyarko Esmond, Kniel Kalmia E., Reynnells Russell, East Cheryl, Handy Eric T., Luo Yaguang, Millner Patricia D., and Sharma Manan. Foodborne Pathogens and Disease. August 2016, ahead of print. doi:10.1089/fpd.2016.2160.
I recycled an old op-ed in response, and still wondering why the same issues haven’t gained traction after 20 years of publicity in Australia.
The Advertiser editorial thingies wrote that irony can be really ironic, given that the government department charged with upholding and maintaining food standards in SA treats the public like mushrooms.
By keeping the public in the dark by refusing to release the names of the 621 food outlets in breach of hygiene rules last year, SA Health is denying consumers the right to make an informed choice.
While it is good enough for the NSW State Government to identify offending premises, those who water their gardens with human effluent, sell out of date food and have cockroach-infested kitchens in SA apparently deserve anonymity.
There is more than a whiff of double standards surrounding the secrecy of the data held by SA Health.
On one hand (who writes this crap?), the public is not allowed to know which of their local fast food outlets is cutting food hygiene corners by selling six-day-old schnitzels, and on the other, it wasted no time last week issuing a warning about NT- grown rockmelons being the apparent source of a food poisoning outbreak in SA.
Surely the public is allowed to know the identity of a food retailer that has been found guilty of a major breach of food standards that could potentially have the same impact as eating the dodgy rockmelon.
For a food outlet to be warned several times about using effluent to water gardens simply beggars belief.
SA Health’s repeated warnings to the business owner were akin to being slapped with a wet lettuce leaf.
If such a practice can continue for such an extended period of time, the public can only wonder just what sort of heinous breach of food safety regulations a business must commit to be jumped on immediately.
My response was:
I coach little kids’ (ice) hockey in Brisbane.
For that voluntary pleasure, I had to complete 16 hours of certification training, in addition to the 40 hours of training I completed in Canada to coach a travel team.
To produce or serve food in Australia requires … nothing.
Restaurants and food service establishments are a significant source of the foodborne illness that strikes up to 20 per cent of citizens in so-called developed countries each and every year.
After helping develop and watching the mish-mash of federal, state and local approaches to restaurant inspection and disclosure in a number of western countries for the past 15 years, I can draw two broad conclusions:
Anyone who serves, prepares or handles food, in a restaurant, nursing home, day care center, supermarket or local market needs some basic food safety training; and,
the results of restaurant and other food service inspections must be made public.
There should be mandatory food handler training, for say, three hours, that could happen in school, on the job, whatever. But training is only a beginning. Just because you tell someone to wash the poop off their hands before they prepare salad for 100 people doesn’t mean it is going to happen; weekly outbreaks of hepatitis A confirm this. There are a number of additional carrots and sticks that can be used to create a culture that values microbiologically safe food and a work environment that rewards hygienic behavior. But mandating basic training is a start.
Next is to verify that training is being translated into safe food handling practices through inspection. And those inspection results should be publicly available.
A philosophy of transparency and openness underlies the efforts of many local health units across North America in seeking to make available the results of restaurant inspections. In the absence of regular media exposes, or a reality TV show where camera crews follow an inspector into a restaurant unannounced, how do consumers — diners — know which of their favorite restaurants are safe?
Cities, counties and states are using a blend of web sites, letter or numerical grades on doors, and providing disclosure upon request. In Denmark, smiley or sad faces are affixed to restaurant windows.
Publicly available grading systems rapidly communicate to diners the potential risk in dining at a particular establishment and restaurants given a lower grade may be more likely to comply with health regulations in the future to prevent lost business.
More importantly, such public displays of information help bolster overall awareness of food safety amongst staff and the public — people routinely talk about this stuff. The interested public can handle more, not less, information about food safety.
Even in New South Wales and Queensland, results are only posted voluntarily.
So if an outlet sucks at food safety, they don’t have to tell anyone.
Toronto, Los Angeles and New York have had mandatory disclosure, on the doors for years.
Adelaide can figure it out.
And instead of waiting for politicians to take the lead, the best restaurants, those with nothing to hide and everything to be proud of, will go ahead and make their inspection scores available — today.
I’ve done lots of stuff with schoolkids over the years – food is a wonderful teaching tool – but this was tough.
There were 10 of us, judging about 180 projects at one elementary school.
Being the newbie, I got the prep (kindergarten) and grade 1s (grade 2 would have been a conflict of interest).
We had score sheets that will be returned to the students, and I thought, how do I evaluate this, I don’t want to crush the investigative soul of a 6-year-old.
It’s fair game to crush the souls of PhD students and other profs through peer-review, but this felt like peer-review for little kids.
I mainly wrote encouraging things and asked questions.
The things kids think of.
We have an awards thingy later tonight, with the all-Aussie sausage sizzle (yes, I will bring my tip-sensitive digital thermometer and use it, because that is the only data that matters when involving food safety), but I wonder if they’ll serve rockmelon (cantaloupe).
Contrary to what Australians are being told, cantaloupe – er, rockmelon – is a known source of foodborne illness and many scientists have investigated the many ways nasty bacteria get on or in the melon; along with potential treatments.
In this paper, researchers from the U.S. Department of Agriculture report surface structure and biochemical characteristics of bacteria and produce play a major role in how and where bacteria attach, complicating decontamination treatments.
Whole cantaloupe rind surfaces were inoculated with Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes at 107 CFU/ml. Average population size of Salmonella, Escherichia coli O157:H7, and L. monocytogenes recovered after surface inoculation was 4.8 ± 0.12, 5.1 ± 0.14, and 3.6 ± 0.13 log CFU/cm2, respectively. Inoculated melons were stored at 5 and 22°C for 7 days before washing treatment interventions. Intervention treatments used were (i) water (H2O) at 22°C, (ii) H2O at 80°C, (iii) 3% hydrogen peroxide (H2O2) at 22°C, and (iv) a combination of 3% H2O2 and H2O at 80°C for 300 s. The strength of pathogen attachment (SR value) at days 0, 3, and 7 of storage was determined, and then the efficacy of the intervention treatments to detach, kill, and reduce transfer of bacteria to fresh-cut pieces during fresh-cut preparation was investigated. Populations of E. coliO157:H7 attached to the rind surface at significantly higher levels (P < 0.05) than Salmonella and L. monocytogenes, but Salmonella exhibited the strongest attachment (SR value) at all days tested. Washing with 3% H2O2 alone led to significant reduction (P < 0.05) of bacteria and caused some changes in bacterial cell morphology. A combination treatment with H2O and 3% H2O2 at 8°C led to an average 4-log reduction of bacterial pathogens, and no bacterial pathogens were detected in fresh-cut pieces prepared from this combination treatment, including enriched fresh-cut samples.
The results of this study indicate that the microbial safety of fresh-cut pieces from treated cantaloupes was improved at day 6 of storage at 5°C and day 3 of storage at 10°C.
Effect of hydrogen peroxide in combination with minimal thermal treatment for reducing bacterial populations on cantaloupe rind surfaces and transfer to fresh cut pieces
1: U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA;, Email: email@example.com 2: U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA
Journal of Food Protection, August 2016, Number 8, Pages 1316-1324, DOI: http://dx.doi.org/10.4315/0362-028X.JFP-16-046