Gordon D W Curtis

Quality control of culture media: perspectives and problems

The Working Party on Culture Media (WPCM) of the International Union of Microbiological Societies (IUMS) has promoted and facilitated the development of methods for quality control of culture media used for the detection and enumeration of food-borne microorganisms since the early 1980s. While progress has been made in establishing protocols to test for productivity and selectivity of media, problems associated with the influence of food constituents and background microflora, as well as the presence of sublethally injured cells in test foods, are yet to be fully addressed before optimum methods for assessing the quality of media can be defined. However, for various reasons, the development of standardised procedures which account for the influence of food constituents or state of debilitation of target microorganisms may not be practical or even desirable.

A statement from the IUMS-ICFMH working party on culture media I

A categorization system for monographs on culture media is outlined which will lead to more rapid publication and a formal division into three classifications; draft, proposed and approved. This should assist the quality assurance and accreditation processes in food microbiology laboratories.

Introduction to the second edition

In the dark cold days of February several weeks into the spring semester, a student of mine at the University of Pennsylvania, whom I’ll call Laurel, got high on a combination of LSD and beer before going to a fraternity party on campus in search of a good time. People at the party reported that during the course of the evening her behavior attracted quite a bit of attention as she danced provocatively to the beat of music only she could hear. She seemed disoriented and out of touch with her surroundings, oblivious to the various fraternity brothers who danced with her during the course of the evening. Some of the brothers spun her around until she was so dizzy she couldn’t find her way out of the room. According to various eyewitness and hearsay accounts, after the party was over five or six of the brothers had sex with Laurel. When Anna, who had observed Laurel’s behavior at the party, heard the brothers bragging about their sexual escapade the next day, she concluded that Laurel had been raped. According to Anna, Laurel was incapable of consent due to her drunken-drugged condition. At a rally held to protest the event weeks later, after word got out on campus about what had happened, Carol Tracy, then director of Penn’s Women’s Center, referred to the 1983 legal definition of rape when she said:

Prevalence of glycopeptide and aminoglycoside resistance in Enterococcus and Listeria spp. in low microbial load diets of neutropenic hospital patients.

Low microbial load diets for patients with haematological malignancy were examined for enterococci and listeria using pre-enrichment, enrichment and selective plating. Enterococci were highly prevalent and their ecology diverse; 100/211 samples yielded 132 isolates made up of 67 strains distinguishable by PFGE. Listeria monocytogenes was not found. Screening of enterococci for antibiotic resistance showed low level vancomycin resistance (6-12 microg/ml) in six isolates of E. gallinarum and high level streptomycin resistance (> or = 1000 microg/ml) in eight isolates from various foods. No strains showing high level glycopeptide or gentamicin resistance were found. The high prevalence of enterococci in food processed for safety indicates a possible route for the acquisition of antibiotic-resistant strains by vulnerable hospital patients.