Microbiological, virological, bacteriological, immunological, medical, epidemiological, historical, anecdotal

Month: October, 2013

Data Update: Typhoid ice cream

To this day, the safety of the ice cream supply is a field of inquiry among microbiologists, as can be seen in recent findings from Croatia (1), Zimbabwe (2) Argentina (3), and other places (4,5). Here in the U.S. there’s not as much concern; as far as I can tell the last outbreak of food poisoning caused by mass-produced ice cream in a rich Western country was in 1994 (6), when beloved Minnesota company Schwan’s Ice Cream was transporting ingredients in unsterilized egg tankers. Since then there have been outbreaks on farms, such as two big ones in Belgium and Wales. Most are like the Belgian case (7), which was blamed on ice cream produced right there on the farm, rather than industrially. The Welsh case (8) was blamed not so much on the ice cream itself, but on ice cream’s notorious ability to make children’s hands sticky, turning them into repositories for farm filth. A comparison between desserts in Houston and Guadalajara (9) suggests that the US is fortunate not to have this problem. But back in the 1910s and 1920s it was a different story.

Looking at old tables of contents from the Journal of Bacteriology, it’s striking how many articles are about milk. Even more than other food products, there was a need for science to improve the safety of milk, cream, cheese, etc. Pasteurization was established as useful in the late 19th century, but it would not become widespread until a 1913 typhoid epidemic in New York. This convinced local authorities that the improvement in public health outweighed people’s concerns about what boiling milk did to its taste and possibly its nutritional content (for more on this see Neatorama, “The Fight for Safe Milk”). But still, outside major urban centers where access to fresh milk was limited, people figured that raw milk was fine because the farms were nearby.

And ice cream was contaminated, too. By tuberculosis, typhoid, Bacillus coli, and others. But how big a problem was it, really? The bacteria wouldn’t multiply if they were frozen. But would they actually be killed?

The results on this were basically in by 1926, when Michigan State professor Frederick Fabian collected them in a great review in the American Journal of Public Health (10). Some excerpts:

The rapid rise of the ice cream industry and the general use of ice cream as a food in the past few years has added another item to the public health official’s responsibilities. If an epidemiologist had been tracing an epidemic a few years back, he could have practically left ice cream out of consideration. However, today it has become such a common article of diet that it should be taken into account in any work of this nature.

…Although there has been a vast amount of work done to show that pathogenic bacteria are not readily killed by freezing, yet, due to the nature of the product ice cream has not always been considered a serious source of bacterial infection. This view is held especially among laymen and those not familiar with the facts.

…To test out the extreme temperature which pathogenic bacteria could withstand Macfayden and Rowland (11) subjected the same organisms to the temperature of liquid hydrogen (-252° C.) for 10 hours without any appreciable effect on them. A great deal of work has been done also to show that pathogenic bacteria live for a considerable length of time in ice and a great many epidemics have been traced to this source.

…In practically every city of any size today pasteurization of the milk supply is required by ordinance. The time and temperature are also pretty well established. There are not many such ordinances or laws pertaining to ice cream in most cities or states. …Many of the old experienced producers from their experience with milk have the good judgment to pasteurize the ice cream mix. However, the unscrupulous and the ignorant are allowed to do as they please.

In short, by 1926 public health authorities have got a handle on milk contamination, but for the very reason that ice cream seems safer (nothing can grow in it! most of the time), it has not been regulated and may now be more of a risk than milk.

Along the way, Fabian lists all known ice cream-associated outbreaks, and describes the experimental evidence for bacterial survival in frozen ice- and cream-like substances. Let’s clarify those results, now that we have the ability to make graphs.

* * *

Four experimental papers are mentioned. Mitchell 1915 (12), Bolten 1918 (13), and Prucha and Bannon 1926 (14) use Salmonella Typhi (or “Bacillus typhosus“, or “Bacterium typhosum“). Davis 1914 (15) uses hemolytic Streptococcus. I found two later papers in the Journal of Dairy Science by G. I. Wallace of the University of Illinois, but as he himself seems to think his results are unimportant, we won’t bother with them.

G. I. Wallace (1938) is not exactly making a big effort to inflate the importance of his results here, is he?

G. I. Wallace (1938) is not trying very hard to inflate the importance of his results.

O. W. H. Mitchell (1915) doesn’t even have a table in his paper. He describes six experiments which involved similar ice cream preparation and storage, but with different ingredients. For each experiment, he introduced some typhoid bacilli to the ice cream mixture, checked after 24 hours of freezing to see how much bacteria there was, and continued measuring until “the last positive examination” for typhoid bacilli. This seems like a badly-controlled series of experiments, since the amount of bacteria introduced into the cultures varies widely between experiments, and I can’t tell the difference between Experiment 1 and Experiment 2. Apparently in Experiment 2, “Ice cream made with 1 pint of thin cream, one-half cup of sugar and 1 tablespoonful of vanilla was treated similarly to the ice cream in Experiment 1.” But… all three of those ingredients are also in Experiment 1. Because of the order things are listed in, my guess is that Experiment 2 has an extra 1/2 cup of sugar.

Also the description of “Flake” powder does not enable colleagues to easily replicate the experiment.

Flake is a powder prepared by the Murray Company, 224 State Street, Boston. According to a circular accompanying the powder, the preparation “is a pure, wholesome powder, which can always be relied on, and is essential in making an exquisitely smooth ice cream.”

That doesn’t help. Anyway, the jumble of descriptive paragraphs can be entirely summed up in this table.


O. W. H. Mitchell’s 1915 data, presented in no particular order

Guess what! That tells us nothing. Pasteurization didn’t help; adding gelatin made things worse somehow; and extra sugar led to less bacteria at the late timepoint. Also, there’s no more bacteria after a couple weeks than there was at 24 hours, even though “After a few days [the samples] began to lose their sweetness of odor, and at the time of the last examinations they gave off mildly unpleasant odors.”

Yes, this was while frozen. They were only slightly below freezing (-3° to -4° Centigrade). Sample size is 1. Total waste of time, I say with 98 years of hindsight.

* * *

Let’s move on to Bolten (1918). He looks at both typhoid and diphtheria bacilli. He shows even less data than Mitchell, but at least the experiments make sense. Basically, small containers of frozen cream (not ice cream, I guess there was no sugar or vanilla) had been inoculated with a growing culture of typhoid, at a 10:1 ratio of cream to bacterial broth, and “immediately placed in a brine tank”. They were “partly melted” daily, and a sample was taken to see how many typhoid bacteria were growing. You’d think that one of the advantages of ice cream as an experimental system is that you don’t have to thaw it in order to take a sample. But that was their procedure.

According to more than one article in the Jan-June 1904 issue of Ice and Refrigeration Illustrated (mental note: look for blog topics in Ice and Refrigeration Illustrated), a “brine tank” typically froze things to between 8 and 16 degrees Fahrenheit (-13° to -9°C). So, quite a bit colder than the ice cream in Mitchell’s study. This type of freezing is pretty good at killing bacteria, given that they started with a substance that was fully 10% bacterial broth. After 2 weeks they had a 50% reduction in colonies; after 4 weeks they had a 95% reduction; and after 10 weeks two of the four containers had no detectable germs at all. Maybe it’s not so much the low temperature as the daily freeze-thaw cycle killing the bacteria.

Skipping gracefully over the diphtheria portion of the paper (which is more confusing), our last entry on ice cream typhoid is the most data-intensive, by Prucha and Brannon of the University of Illinois in the relatively rigorous Journal of Bacteriology. (The other two are in medical journals… who cares about lab experiments in those?) They standardize their experiments by mixing bacteria with ice cream mix, incubating, and freezing it when it gets to 25 million bacteria per cubic centimeter. They keep it in a “hardening room” which fluctuates between -8° and 8°F (-22° to -13°C) – the coldest freezing conditions we’ve seen so far. They take samples not every day, but at increasingly sparse intervals – and they actually show us their data in a table. Which can easily be turned into a graph.


I should use the word “germs” more often in writing about these things. I forget about the word “germs”.

A summary:


Here we see something much closer to Bolten’s “bacteria are mostly killed by freezing”, rather than Mitchell’s “bacteria keep growing in the cold”. And this wasn’t with constant refreezing and rethawing, either. Just low temperatures.

You may notice that the number increases 3-fold between day 134 and 165. Well, they explain that too.

It will be observed in table 1 that the samples taken when the ice cream had been in storage for 165 days gave higher counts than the previous samples. To check this point, another set of samples was taken five days later which again gave similar counts. An inquiry brought out the fact that one of the attendants had removed the experimental ice-cream a few days before to an adjoining room for an hour and one-half. This room had a temperature of 40°F. The ice cream did not melt. Whether there was any multiplication of the germs at this time could be determined.

The conversation that led to that passage:

Prucha: What happened here?

Brannon: I looked into that. You won’t believe it. One of the fellows in the dairy husbandry program, who we told to keep an eye on the freezer…

Prucha: Yes?

Brannon: Well, some of his fraternity brothers let him know it would be a great joke to take the experimental ice-cream into the common room and start eating it.

Prucha: Oh, goodness. Doesn’t he know we put typhoid in it?

Brannon: I think we were a little too excited when we found out freezing had reduced the germs by 99%.

Prucha: So did it melt? Is that why the numbers are high?

Brannon: Luther says he told the boob to put it back in the freezer before it got soft. It was out for maybe 90 minutes.

Prucha: Undergraduates! Damned impudent wastrels!

Brannon: Do we really need “attendants” for this experiment at all?

* * *

1. Mulić R et al (2004). Some epidemiological characteristics of foodborne intoxications in Croatia during the 1992-2001 period. Acta Med Croatica 58:421-427.

2. Igumbor EO et al (2000). Bacteriological examination of milk and milk products sold in Harare. Afr J Health Sci 7:126-131.

3. Di Pietro S et al (2004). Surveillance of foodborne diseases in the province of Rio Negro, Argentina, 1993-2001. Medicina [B Aires] 64:120-124.

4. Gücükoğlu A et al (2012). Detection of enterotoxigenic Staphylococcus aureus in raw milk and dairy products by multiplex PCR.
J Food Sci 77:M620-623.

5. el-Sherbini M et al (1999). Isolation of Yersinia enterocolitica from cases of acute appendicitis and ice-cream. East Mediterr Health J 5:130-135.

6. Hennessy TW et al (1996). A national outbreak of Salmonella enteritidis infections from ice cream. N Engl J Med 334:1281-1286.

7. De Schrijver K et al (2008). Outbreak of verocytotoxin-producing E. coli O145 and O26 infections associated with the consumption of ice cream produced at a farm, Belgium, 2007. Euro Surveill 13:8041.

8. Payne CJ et al (2003). Vero cytotoxin-producing Escherichia coli O157 gastroenteritis in farm visitors, North Wales. Emerg Infect Dis 9:526-530.

9. Virgil KJ et al (2009). Coliform and Escherichia coli contamination of desserts served in public restaurants from Guadalajara, Mexico, and Houston, Texas. Am J Trop Med Hyg 80:606-608.

10. Fabian FW (1926). Ice cream as a cause of epidemics. Am J Public Health (N Y) 16:873-879.

11. Macfayden A & Rowland S (1900). A further note on the influence of the temperature of liquid hydrogen on bacteria. Lancet 156:254-255.

12. Mitchell OWH (1915). Viability of Bacillus typhosus in ice cream. JAMA LXV:1795-1797.

13. Bolton J (1918). Effect of freezing on the organisms of typhoid fever and diphtheria. Pub Health Rep 33:163-166.

14. Prucha MJ, Brannon JM (1926). Viability of Bacterium typhosum in ice cream. J Bacteriol 11:27-29.

15. Davis DJ (1914). The growth and viability of streptococci of bovine and human origin in milk and milk products. J Inf Dis 15:378-388.


Also in the Pacific Medical and Surgical Journal, in 1864, appeared a piece entitled On the Treatment of Stricture of the Urethra by means of Subcutaneous Division (pages 285-288). There’s no listed author; though written in the third person, it seems to be a summary of one or more speeches by Dr. Henry Dick, eminent surgeon at the National Orthopaedic Hospital on Great Portland Street, London. Here is an 1878 monograph on the same topic, by the great man himself, which includes the text of his 1864 address to the Royal Medical and Chirurgical Society.

Anyway, while scrolling randomly through the pdf, as one does, something stood out.


That’s right. This surgical procedure on the male urethra involved a device called *Dr. Dick’s grooved staff with a bulbous extremity*.

What we have here is an early case of nominative determinism at its best.

This is pretty far afield from the supposed focus of this blog, but I couldn’t resist.

Those wacky women and the etiology of their silly poisoning symptoms

In 1864, epidemiology as we know it didn’t exist. For example, the word “epidemiology” barely existed. Merriam-Webster claims the word dates to circa 1860, and Random House says 1870-75. John Snow’s great work was only a decade earlier.

Whatever the terminology, the study of disease outbreaks was a long way from being a statistical discipline. The best evidence that something led to disease, whether infectious disease or some sort of poisoning, came from collections of anecdotes and case studies, like the two presented by William S. Barker, M.D. in the January/February 1864 issue of the St. Louis Medical and Surgical Journal. This piece was reprinted in the Pacific Medical and Surgical Journal, volume VII (1864): 140-142, a journal which contains a lot of excerpts or “selections” from other publications. I don’t know if the original St. Louis journal has been digitized. The Pacific editors spotlighted these selections to publicize the return of the St. Louis journal, which had apparently been on a three-year hiatus.


The first case is G. W. E——–, a blue-collar worker who responds with “no” to all the doctor’s queries about whether he’s been ingesting arsenical food prepared by incompetent strangers, or patent medicines prepared by charlatans. The doctor thinks his symptoms look like poisoning rather than infection. It turns out that in his job casting molds at a foundry, he uses a lot of oil of vitriol (sulfuric acid) to get sand out of the molds. Dr. Barker remembers that arsenic poisoning occurred in other people exposed to oil of vitriol, for example people who use it in the manufacture of hydrochloric acid. At this time H2SO4 was made from heating of iron pyrite which contained arsenic impurities. After being told to stop inhaling so much sulfuric acid, the patient recovers. Simple and straightforward.

Final paragraph:

He was quite ill for ten days, but recovered perfectly. I think the case worthy of notice, as the cause of the disease was at first obscure, yet so unequivocal when understood.

* * *

In presenting the second case, Dr. Barker decides to lighten the mood, and gets all snarky, in a kind of way. But he probably would not enjoy, because his japes and quips are at the expense of “vain women” and women with intellectual pretensions. First, the poet Cowper is quoted for the purpose of establishing the fact that women use makeup. Then it is revealed that apparently some women seek to change their appearance not entirely to look winsome and nubile, but also in risible attempts to appear intelligent. This is accomplished by enhancing the height of one’s forehead, by physical or chemical hair removal.

Unkown lady, possibly Isabella de' Medici, by Bronzino (1503-1570)

Unkown lady, possibly Isabella de’ Medici, by Bronzino (1503-1570)

I know nothing about this, but my guess is that this was a simple case of following fashion trends, as there were certainly several instances in history of an exaggerated high forehead being the goal of the fashionable women of high society. Presumably it was associated with intelligence. But it’s a bit of a stretch to say, as Barker does, that it’s an attempt to resemble men, men being synonymous with brainpower.

Such delicate carnal glories have no charm for them. They are women of self-presumed intellectual power; as nature has unquestionably given to man a preponderance of intellect, they would look like men “as far as in them lies.” But there are only a few females to whom nature has given a broad and lofty brow. “The dome of thought, the palace of the soul,” is a somewhat diminutive tenement. Broad shoulders and a stentorian voice will not avail the strong-minded female, if the hair grows low on the forehead.

Yes, of course. Women’s heads are smaller than men’s, and to compensate, they want their hairlines to recede.

So Dr. Barker had a patient who tried to elevate her forehead by hair removal. Much like Mr. G. W. E——–, he anonymizes her name in an objective way, to “Miss Ophelia McDunder”. And in her case, it was the dreaded patent-medicine man who convinced her to poison herself, with a three-part hair removal technique consisting of Spanish fly to raise blisters, a powder of arsenic, and wax to fix everything in place under a bandage. This would prevent hair from growing back post-shaving. After four days of application, she was very sick and called the doctor. After removing the plaster, “her convalescence was tedious”, which is a medical term meaning slow.

In the course of describing this, Dr. Barker goes on various flights of fancy using mock-elevated language and poetic allusions, the Simpsons references of their day.

  • “the personal attractions of one of Eve’s fair daughters”
  • “she has undergone a scientific metamorphosis”
  • “perverse nature had renewed the growth”
  • “she utters maledictions ‘not loud, but deep'”

Final paragraph:

The above case furnishes a warning to quacks who use depilatories, and silly women who would deform themselves with second-story foreheads.

* * *

Volume VII of the Pacific Medical & Surgical Journal can be found in Google Books form here (starting with a handy index). Or search the web for “Miss Ophelia McDunder”. Or search for “vanity’s unwearied fingers”, since this paper is apparently the only case of that particular work of the poet Cowper being digitized or excerpted.

The all-male world of 19th-century medicine did not lead all its practitioners to adopt a condescending attitude. For a more respectful treatment of women being poisoned by cosmetics, see Lewis A. Sayre, M.D. (1869), Three cases of lead palsy from the use of a cosmetic called “Laird’s Bloom of Youth”: Transactions of the American Medical Association XX: 561-572. And that one is available here.

So, that would be a 1-star review, then.

From George A. Denison (1936), Epidemiology and symptomatology of Staphylococcus food poisoning: A report of recent outbreaks, Am. J. Public Health 26(12): 1168-1175:


Denison, the Director of Laboratories for the Jefferson County (Alabama) Board of Health, describes an outbreak of food poisoning associated with Birmingham’s worst bakery, and explains that this is not surprising since budget cuts forced by the Depression have put a stop to most if not all food inspections. He then describes the culturing of cream puff extracts, and their uncomfortable effects on five volunteers.

This represents one of the few times the words “filthy”, “revolting”, “repugnant”, and “obnoxious” have appeared in a single paragraph of an objective piece of scientific investigation.