P. A. M. Guinée

Decrease of Drug Resistance in Salmonella in The Netherlands

Since 1974, tetracycline resistance in salmonellae of human and porcine origin has decreased nation-wide in The Netherlands. This decrease has coincided with the ban on incorporation of tetracycline in animal feeds.

Incidence of resistance to ampicillin, chloramphenicol, kanamycin and tetracycline amongSalmonella species isolated in The Netherlands in 1972, 1973 and 1974

The resistance ofSalmonellae to drugs has been studied in the Netherlands since 1958. In 1972, 1973, and 1974 respectively, 14241, 13086, and 22927 strains were tested for resistance to ampicillin, chloramphenicol, kanamyci and tetracycline. From 1973 all strains were also tested for resistance to trimethoprim.In the period covered, the yearly incidence of resistance to at least one of the above drugs ranged from 39.2% to 45.6% of all strains obtained from various sources (humans, animals, animal products, sewage, etc.).A new finding in the period 1972 to 1974 was that many multiply resistant strains emerged inS. typhimurium and inS. dublin isolated from calves and cattle. In 1974, 64.4% of all strains ofS. typhimurium from these animals appeared to be resistant to ampicillin, tetracycline, chloramphenicol and kanamycin, and 25.5% of those ofS. dublin were found to be resistant to chloramphenicol and tetracycline.Of all strains ofSalmonellae examined in 1973 and 1974 respectively, 0.15 and 0.22% were resistant to trimethoprim, the main component of the twin-drug cotrimoxazol.Of the 142 strains ofS. typhi isolated in 1972 to 1974 two were resistant to tetracycline only, and one was resistant to all four antibiotics. The others had a normal susceptibility pattern.

Incidence of resistance to ampicillin, chloramphenicol, kanamycin, tetracycline and trimethoprim of Salmonella strains isolated in The Netherlands during 1975–1980

From 1975–1980, about 130 000 Salmonella strains isolated from various sources were tested for resistance to ampicillin, chloramphenicol, kanamycin, tetracycline and trimethoprim. Following the ban on incorporation of tetracycline in animal feeds for nutritive purposes, tetracycline resistance in S. typhimurium and S. panama strains of porcine origin dropped from about 90% in 1974 for both species, to about 34% and 1%, respectively, in 1980. The incidence of resistance in human strains concurrently decreased from about 80% in 1974 to 25% and 1%, respectively, in 1980.The build-up of multiple resistance in bovine S. dublin and S. typhimurium strains, already started in 1973–1974, has continued. Recently, phage type 193 S. typhimurium strains have become predominant and they are invariably resistant to ampicillin, chloramphenicol, tetracycline, kanamycin, neomycin, streptomycin, sulphonamide and trimethoprim. Up to now, type 193 strains were hardly encountered in human patients, but the number of human isolates is slowly increasing.A fairly large number of multiply resistant strains belonging to S. oranienburg, S. schwarzengrund, S. typhimurium and, recently, S. krefeld have been isolated from adoptive children from the Far East.

Chapter IV Phage Typing of Salmonella

Publisher Summary This chapter discusses the phage typing of Salmonella. Phage typing is primarily used as a method to establish the epidemiological relation of bacterial strains that cause outbreaks of disease. Phages occur abundantly in sewage, sewage-contaminated surface water, and in faeces. Although phages isolated from such materials are usually called “wild-type phages,” they may equally be lysogenic phages. A particular phage type can be determined by the presence of one or more plasmids with restricting properties. Introduction or segregation of such elements may alter the phage pattern of the host. The tool of phage typing may contribute to the classification of R-factors and other plasmids and to the understanding of their epidemiological behavior. The examples presented in the chapter indicate that strains with different phage types may be epidemiologically related.

Mechanized Technique for Phage Typing and Determination of Antibiograms

A device for mechanical application of either drops of phage suspensions or antibiotic-containing tablets was developed. The device consists of a Transport Apparatus which transports petri dishes from one side of the apparatus to the other in such a way that the plate and the lid of a petri dish become entirely separated at a particular stage. Either a Phage Applicating System or an Antibiotic Tablet Dispenser can be connected to the apparatus. In this way a maximum of 27 phages of 7 antibiotic tablets per plate can be applied pneumatically.