The ability of bacterial spores and vegetative cells to adhere to inert surfaces was investigated by means of the number of adherent spores (Bacillus cereus and Bacillus subtilis spores) and Escherichia coli cells and their resistance to cleaning or rinsing procedures (adhesion strength). Six materials (glass, stainless steel, polyethylene high density (PEHD), polyamide-6, polyvinyl chloride, and Teflon) were tested. Slight differences in the number of adherent spores (less than 1 log unit) were observed between materials, but a higher number of adherent E. coli cells was found on the hydrophobic materials PEHD and Teflon. Conversely, the resistance of both B. cereus and B. subtilis spores to a cleaning procedure was significantly affected by the material. Hydrophobic materials were harder to clean. The topography parameter derived from the Abbott-Firestone curve, RVK, and, to a lesser extent, the widely used roughness parameters RA (average roughness) and Rz (maximal roughness), were related to the number of adherent cells. Lastly, the soiling level as well as the adhesion strength were shown to depend largely on the microorganism. The number of adhering B. cereus hydrophobic spores and their resistance to a cleaning procedure were found to be 10 times greater than those of the B. subtilis hydrophilic spores. Escherichia coli was loosely bound to all the materials tested, even after 24 h biofilm formation.

C. FAILLE, F. FONTAINE AND T. BÉNÉZECH. 2001. Aims: The hygienic risk associated with microbial soil on surfaces of milk processing lines was evaluated, based on experimental results. Methods and Results: From a panel of Bacillus spores isolated from milk products, B. cereus CUETM 98/4, was found to be highly resistant to heat (D100=3·32 min in whole milk) and oxidant disinfectant (70% lethality of adherent spores with Ikalin 2%). From adhesion trials, up to 1·1 × 107 spores cm−2 were found to be adherent to solid surfaces when suspended in saline or in custard (105 and 107 cfu ml−1), and over 10% of these adherent spores would resist the cleaning procedure. Conclusions: A highly contaminated milk (105 cfu ml−1) subjected to a current sterilization process (8 log reduction) led to a residual contamination of less than 1 cfu in the representative processing line after a complete production run. Significance and Impact of the Study: This study highlighted the fact that under appropriate processing conditions (efficient sterilization and cleaning procedures), even disinfection would be sufficient to eliminate any contamination risk. Conversely, the disinfection procedure becomes an essential step under inappropriate processing conditions.

SUMMARYThe potential risk of bacterial dissemination due to the presence of cockroaches (Blattella germanica, Blattellidae) in low-income flats was investigated. Cockroaches can carry a great variety of bacterial species; we identified 30 different species from 52 different flats. Klebsiella oxycytoca, K. pneumoniae and Enterobacter cloacae were the most frequently found. Pathogenic and potentially pathogenic bacteria represented 54 % of all the bacterial identifications. Bacteria were carried either on the cuticle or in the gut. Contamination through external contact is sufficient to insure bacterial diffusion. There was a very low level of overlap estimated by Pianka's index (a) between the bacterial flora of neighbouring blocks of flats, and (b) between bacterial flora of different flats in the same block.

The immunological relationship between leprosy-derived corynebacteria (LDC) and reference mycobacteria was analysed by crossed immunoelectrophoresis with intermediate gel. For this purpose, three reference systems (LDC15/anti-LDC15, LDC18/anti-LDC8, and LDC8/anti-LDC8) were developed. They showed 15 to 20 distinct antigenic components in LDC cytoplasm. Extensive cross-reactivity was observed among different LDC isolates, affecting 3 to 17 components. Moreover, several components were shown to cross-react with mycobacteria when anti-bacillus Calmette-Guérin (BCG), anti-Mycobacterium leprae, other antisera and lepromatous leprosy sera were incorporated in the intermediate gel. The major cross-reactive component, antigen M, was present in all LDC isolates and cross-reacted with antigen 7 of M. leprae and antigen 60 of M. bovis BCG. The thermostability of these antigens and the specificity of the cross-reacting antigens were assessed. The data underline the degree of immunochemical homogeneity within the LDC group of micro-organisms and relatedness with M. leprae and other mycobacteria.