Campylobacter and fluoroquinolones: a bias data set?

• Published in: Environmental microbiology 2003-04, Vol.5 (4), p.219-230
• Main Author: Silley, Peter
• Format: Article
• Language: English
• Subjects: Animals; Anti-Infective Agents - pharmacology; Bias; Campylobacter - drug effects; Campylobacter - genetics; Campylobacter - isolation & purification; Campylobacter - metabolism; Campylobacter Infections - epidemiology; Culture Media - chemistry; Drug Resistance, Bacterial; Fluoroquinolones; Humans; Microbial Sensitivity Tests
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1046/j.1462-2920.2003.00425.x

Summary There is no universally accepted standard method for the isolation of Campylobacter spp. and it is considered that currently available isolation media are not yet optimal for the recovery of Campylobacter spp. from a range of sample types. Almost all methods incorporate antibiotics into the isolation media to inhibit growth of other bacteria within the sample. It is established that the incorporation of such antibiotics into isolation media will inhibit the growth of some Campylobacter spp. as well as other bacteria. The results of the use of such suboptimal isolation methods are that the isolates which ‘survive’ the isolation procedure will be those which: (i) are able to ‘out compete’ the rest of the bacteria in the sample, i.e. they are able to grow faster; (ii) are resistant to the antibiotics used in the isolation media; and (iii) are randomly selected by the laboratory technician as being a ‘typical’Campylobacter spp. It is clear that such a procedure is intrinsically biased and will mean that species resistant to the antibiotics used in the media will be isolated. This introduces real doubt that the bacteria isolated are truly representative of those initially found on the sample. It is also becoming clear that Campylobacter spp. are rather difficult to isolate as pure cultures and many are in fact mixtures of more than one strain. Again this introduces great uncertainty as to the prevalence and distribution of respective species from the different sample types. This is especially true when considering isolation of Campylobacter spp. causing disease in man as there is no certainty that the selected isolate is that which was responsible for disease. The incorporation of antibiotics into the isolation media not only introduces the issue of species bias but perhaps more importantly exposes the Campylobacter spp. to a cocktail of antibiotics thereby providing the potential for them to ‘switch on’ antibiotic resistance mechanisms. It might be argued that this has always been the case for isolation of Campylobacter spp., however, we know that the antibiotic cocktails used in media over the last 10 years have changed and indeed there was a time when the filtration protocol which didn’t use antibiotics was more widely used. As most reports in the literature do not state what methods were used to isolate Campylobacter spp. it is not possible to quantify any relationship between antibiotics used in the isolation media and susceptibility data. An appro