Everybody is now probably aware that for some time, we have been living with strains of bacteria which are immune to many common antibiotics. This is not unexpected as it is one of the logical (and short-sighted) consequences of adding vast quantities of antibiotics into animal/poultry feeds. In fact, over 80% of the antibiotics produced worldwide are used in the food industry. Antibiotic resistance is simply a predictable outcome of the quest for profits in the meat and dairy industry.
So a recent study from Brazilian researchers was interesting as it attempted to analyse how certain bacteria acquire this resistance to antibiotics. Foodborne diseases have affected hundreds of thousands of people in Brazil in the last two decades, and many cases were linked to bacteria in the genus Salmonella. This is particularly intriguing as a friend in London had contracted salmonella poisoning around 20 years ago, and it was so severe he was hospitalised for six weeks. Fortunately, the antibiotics he was given eventually worked but it was sobering and traumatic to see him so ill for so long. Imagine what would have happened had it been a strain of salmonella immune to antibiotics.
More about salmonella
The Brazilian study investigated 90 serovars (sub-strains) of salmonella typhimurium (ST), a sub-species of salmonella enterica, which is the species of salmonella most involved in human food poisoning (normally resulting in gastroenteritis). Testing serovars of ST with common classes of antibiotics revealed that 72.2% were immune to sulphonamides, 48.9% were resistant to streptomycin, 30% are tetracycline resistant, 23.3% were unaffected by gentamicin, etc. In addition, a previous study had reported that 46 serovars of ST were also resistant to nalidixic acid (and also to flouroquinolones). It was grim reading, especially as it was also noted that streptomycin and tetracycline are still common additives in animal feeds.
Whole genome sequencing (WGS) was used to analyse how this resistance developed in the ST serovars – this is a non-trivial task as the ST genome contains 4.7 million base pairs. The results were interesting. The research detected different types of mutations in the gyrA, gyrB, parC and parE genes, and only one mutation point in one of these genes was observed. Resistant ST serovars also have additional activated genes, which may be one or more of the qnr, qepA, oqxAB and aac(6’)-Ib-cr genes. It appears that antibiotic resistance in ST serovars is conferred by single point mutations in certain genes in conjunction with the activation of other specific genes.
There are two other curious findings in this paper. One is the antibiotic/antimicrobial resistance of ST serovars have been declining since the 1990s. This may be due to the rise of a more aggressive salmonella enterica sub-species called salmonella enteritidis which caused a worldwide pandemic in the 1990s and has been prevalent ever since. Salmonella enteritidis is the very dangerous pathogen (disease-causing agent) associated with eating undercooked contaminated eggs.
The other odd finding is that resistance to certain antibiotics developed even without any exposure to such antibiotic compounds in the feed or anywhere else. It appears that mutations arising from other antibiotics may be sufficient to promote resistance to unrelated (but somewhat similar) categories of antimicrobials.
As salmonella usually breeds in the intestinal tracts of animals and poultry, I am safe from any possibility of contracting gastroenteritis, at least for a while. This is because I am in the middle of a vegan challenge with my daughter until the end of the month.
Being vegan here in France is not as easy as in Berlin where I was last month. I quickly grew tired of my own vegetable stews and curries and decided to get some different vegan meals at the small supermarket in the next village. When I could not find any chilled vegan foods after a search, I eventually asked an assistant about them. He looked incredulously at me as if I was mad before shaking his head sadly. “Désolé, nous n’avons pas de truc végétalien.” (Sorry, we do not have any vegan stuff).
I finally found some tasty vegan foods in a large supermarket in a town about 40km away. The labelling of vegan items in France is heavily influenced by the meat industry here – for example, it is not allowed to label food as burgers or sausages if they are made with non-meat products. But it seems they had forgotten to ban vegetarian “steaks” and “cordon bleu” dishes, which is what I got.
There are several reasons for my vegan challenge. One is curiosity, another is not adding on excessive weight now that the cold season has started – but the main reason is to confront my own denialism about meat production. Denialism is a mechanism used to alter how we think about things so that we can function better or, at least feel better. Sometimes we fool ourselves but very often, we are fooled by other people/things. You can read more on https://www.star2.com/food/2018/09/09/curious-cook-a-quiet-month-of-denialism/
Having access to thousands of research papers provides an in-depth insight into meat production, its consequences, health impacts and development over time. If you think about it, we should not be eating so much meat – not because meat is necessarily unhealthy, but because humans are physically not good predators. Lions are better adapted to be at the top of the food chain in the wild, not humans.
Our brains, again
However, our brains have allowed us to overcome our physical limitations, initially by crafting tools/weapons which enhanced our ability to hunt. Then around 13,000 years ago, humans began domesticating animals for food. In normal evolution, lions required hundreds of thousands of years to evolve their speed, claws and teeth, but human intelligence allowed us to short-cut our way to the top of the food chain and a practically limitless supply of meat.
The speed of change is staggering: the first chicken super-farm was devised in 1926 but before the end of the last century, Concentrated Animal Feeding Operations (CAFO) and industrial meat farms were already supplying chicken, pork and beef to billions of people, without any consumer making any more effort than picking up a pack of meat and paying for it.
The only way to achieve such prodigious productivity in meat is to invent artificial solutions and ignore the existing natural order of things. This disregard for natural circumstances has profound consequences: deforestation, desertification, antimicrobial resistance, global warming, pollution, etc, and includes the creation of animal and bird hybrids which would be considered mutants in the wild. The world now also plants more food for meat production than for humans.
There are health consequences for humans too. The ubiquity of meat means that most humans have little regard for the sources of animal proteins, practically treating animals like insentient plant crops. Ignoring the disturbingly cruel realities of industrial meat production means that many people now unknowingly ingest meats contaminated with pesticides, herbicides, antibiotics, growth hormones, chemicals such as preservatives, flavourings, etc. Crop-treatment compounds are present in meat because animal feed need not meet human safety standards but these compounds can accumulate in animal flesh and offal, sometimes to problematic levels.
In summary, people generally do not know as much as they should about animal proteins, and our denialism conspires to keep us ignorant. There is also something wrong when humans can use their intelligence to satisfy our lust for meat but cannot apply the same intelligence to more important issues like our environment. The only difference appears to be the quest for profits, as discussed earlier about the rise of antibiotics-resistant bacteria.
The irony is humans need only tiny amounts of daily protein (animal or non-animal is immaterial): only 0.8 grams per kilo of body weight. So, a quarter-pounder burger fulfills the protein requirement for someone who weighs over 141 kilos. If people cannot wean themselves off meat, then limiting consumption to only the protein amount they actually need would be both healthy and responsible.
In time, the survival of humans will inevitably require overcoming, among other things, our genetic disposition for preferring meat, just as we overcame our genetic limitation of being lousy predators. And this probably starts with overcoming our denialism.
Curious Cook appears on the second and fourth Sunday of the month.