Infectious Diseases 2017

Infectious Diseases 2017

Antibiotic resistance: An unexpected chronology

The Lancet Infectious Diseases – Nov 29, 2017 1 December, 2017

A new study by French scientists suggests the rise of ampicillin resistance in a strain of Salmonella may have begun before the antibiotic was ever used in humans.
Ampicillin, the first semi-synthetic penicillin active against Enterobacteriaceae, was released onto the market in 1961. The first outbreaks of disease caused by ampicillin-resistant strains of Salmonella enterica serotype Typhimurium were identified in the UK in 1962 and 1964.
In this study, whole-genome sequencing study, we analysed 288 S enterica serotype Typhimurium isolates collected between 1911 and 1969 from 31 countries on four continents and from various sources including human beings, animals, feed, and food.
Hence, molecular analysis suggests that the ampicillin resistance gene (blaTEM-1) emerged in Salmonella, several years before the antibiotic was released onto the pharmaceutical market. The findings also indicate that a possible cause was the common practice of adding low doses of narrow-spectrum penicillin G (also known as benzylpenicillin) to animal feed in the 1950s and 60s.
These findings suggest that antibiotic residues in farming environments such as soil, waste water, and manure may have a much greater impact on the spread of resistance than previously thought. 
The researchers found various ampicillin-resistance genes in 11 isolates (3.8%) from human samples. Importantly, the blaTEM-1 gene was found on plasmids in three isolates taken from humans in France and Tunisia in 1959 and 1960.
In further analyses, the authors confirm that ampicillin resistance genes can be successfully transferred between wild type S. Typhimurium strains after exposure to relatively low levels of penicillin G, similar to those found in the livestock environment during the fifties-seventies.