Survival of biofilm-forming Salmonella on stainless steel bolt threads under dry conditions.
We examined the survival of two biofilm-forming strains and two biofilm-deficient strains of non typhoid Salmonella (NTS) on stainless steel bolt threads under dry conditions. Five µL of tryptone soya broth or egg yolke mulsion containing NTS strains at a concentration of 9 log cfu/mL was dropped onto the thread surfaces of hexagonal bolts. After inoculation, the bolts were screwed into the nuts, and then removed (Separate type) or not removed (Unit type). The two types of samples were kept in a dry environment (20.0-25.0°C, 2-15% humidity) and bacteria on the surfaces were periodically counted. Biofilm-forming strains were recovered from all samples after 336 days of incubation, but biofilm-deficient strains were isolated from only two of 8 samples after 336 days. This finding demonstrates that NTS can survive for approximately one year on bolt threads, providing direct evidence of the potential risk of constructions having crevices or uneven surfaces as possible contamination sources. The risk of cross-contamination may be higher for biofilm-forming strains than for biofilm-deficient strains.
Tokyo Kasei University, Tokyo, Japan. moritay@tokyo-kasei.ac.jp
Yukio
Y
Morita
Emiko
E
Komoda
Kazuaki
K
Ono
Susumu
S
Kumagai
D018441:Biofilms; D015169:Colony Count, Microbial; D003252:Construction Materials / Q000382:microbiology*; D004866:Equipment Contamination; D005506:Food Contamination / Q000517:prevention & control*; D005525:Food-Processing Industry / Q000295:instrumentation*; D012475:Salmonella / Q000502:physiology*; D012478:Salmonella Food Poisoning / Q000517:prevention & control; D013193:Stainless Steel; D013997:Time Factors
D013193:Stainless Steel