E. Severina et al., ANTIBACTERIAL EFFICACY OF NISIN AGAINST MULTIDRUG-RESISTANT GRAM-POSITIVE PATHOGENS, Journal of antimicrobial chemotherapy, 41(3), 1998, pp. 341-347
The rapid spread of multidrug-resistant bacterial pathogens necessitat
es the search for alternative antibacterial agents. We examined the ef
ficacy of the antibiotic nisin against 56 multidrug-resistant isolates
of Streptococcus pneumoniae, 33 Staphylococcus aureus and 29 vancomyc
in-resistant Enterococcus faecium and Enterococcus faecalis isolates.
The test strains represented a large variety of clonal types las deter
mined by a combination of DNA fingerprints) isolated from a variety of
geographic sources, and included some of the major internationally-sp
read multiresistant epidemic clones of S. pneumoniae and methicillin-r
esistant S. aureus (MRSA), MRSA strains resistant to over 16 generical
ly distinct antibacterial agents, and enterococcal strains resistant t
o all currently available chemotherapeutic agents including glycopepti
des, In the overwhelming majority of cases, treatment of growing cultu
res with nisin at 1 mg/L (S. pneumoniae) or 10-20 mg/L (in MRSA and en
terococci) caused extensive (10(3)- to 10(4)-fold) loss of viable titr
e accompanied by various degrees of loss in the optical density of the
cultures, which was most extensive in pneumococci (>90%) and least ex
tensive (40-50%) in enterococci, Nevertheless, extensive variation in
rates of nisin-induced autolysis was observed in each bacterial specie
s. Serial exposure of a penicillin-susceptible strain of S. pneumoniae
to nisin (1 mg/L) in liquid culture resulted in the rapid appearance
of stable nisin-resistant mutants in which the MIC increased from 0.4
to 6.4 mg/L and the resistance trait was transferable by genetic trans
formation.