Volume 6, Number 4—August 2000 To the Editor: Davis et al.
offered four reasons why local antimicrobial selection pressure
in cattle may not play an important role in the dissemination of
multidrug-resistant Salmonella from cattle to humans (1). Their
conclusions differ from those of other recent studies (2-6). The
authors' first two arguments relate to the high levels of
chloramphenicol resistance in the United States, despite a
relative lack of chloramphenicol use in livestock. In
industrialized countries, chloramphenicol use in humans is also
low because of medical and legal concerns about aplastic anemia.
In Australia, the total average annual human use of
chloramphenicol from 1992 to 1997 was 208 kg (6). This is lower
than the annual use for most other antibiotics (e.g.,
sulphonamide 22,331 kg in humans and 24,869 kg in animals;
tetracycline 12,677 kg in humans and 77,619 kg in animals) (6).
Despite this low use in humans, chloramphenicol resistance can
be common in many human pathogens, e.g., multidrug-