Listeria strains were highly sensitive to the preferred antibiotics
used to treat listeriosis, such as ampicillin and amoxicillin, with or
without gentamicin, or trimethoprimesulfamethoxazole (co-trimoxazole)
as a second choice. However, special mention must be
made of the reduced susceptibility of eight strains of
L. monocytogenes (3.9%) and seven strains of L. innocua (5.4%) to
penicillin G.
Regarding multi-resistance, six strains of L. monocytogenes
(2.9%) showed resistance to two antibiotics (clindamycin and
oxacillin) and intermediate susceptibility to penicillin G. However,
ten L. innocua strains (7.7%) revealed resistance to three antibiotics
(clindamycin, oxacillin, and tetracycline), and four of them showed
intermediate susceptibility to penicillin G. Another eight strains
proved resistant to clindamycin and oxacillin and five of said strains
showed intermediate susceptibility to ciprofloxacin and the rest to
penicillin G.