CHAPTER 7
Bacterial Agents of Foodborne Illness
7.1 AEROMONAS HYDROPHILA
7.1.1 Introduction
Currently,Aeromonas(principallyA. hydrophila,butalsoA. caviaeand
A. sobria) has the status of a foodborne pathogen of emerging importance.
LikeListeria monocytogenes,Plesiomonas, andYersinia enterocolitica,it
has attracted attention primarily because of its ability to grow at chill
temperatures, prompting the concern that any threat it might pose will
increase with the increasing use of chilled foods (Table 7.1). Present
uncertainty over its significance however, is reflected in much of the
information available which does not, as yet, present a coherent picture.
It was first isolated from drinking water by Zimmerman in 1890 and the
following year from frog’s blood by Sanarelli. They called their isolates
Bacillus punctata andBacillus hydrophilusrespectively and it was not
until the 1930s that the genusAeromonaswas first described. Although
the taxonomy is still not settled, more recent studies have led to the
recognition of two major groups within the genus: the Salmonicida
group, which contains the non-motileAeromonas salmonicidaand several
Table 7.1 Reported lag times and growth rates of psychrotrophic pathogens at
chill temperatures
Lag time (days) Generation time (h^1 )
Temperature ( 1 C) 0–1 2–3 5 0–1 4–5
Aeromonas hydrophila 422 6–10 3–4 449 9–14
Listeria monocytogenes 3–33 2 –8 1–3 62 –131 13–25
Yersinia enterocolitica 3 2.4 – 25 20