cidal effects of abx on slowly growing and nongrowing bx

[Guest guest]

I may have posted this before. Its a hoary classic from 1991.

http://aac.asm.org/cgi/content/abstract/35/9/1824

ABSTRACT

Antimicrobial agents are most often tested against bacteria in the

log phase of multiplication to produce the maximum bactericidal

effect. In an infection, bacteria may multiply less optimally. We

examined the effects of several classes of antimicrobial agents to

determine their actions on gram-positive and gram-negative bacteria

during nongrowing and slowly growing phases. Only ciprofloxacin and

ofloxacin exhibited bactericidal activity against nongrowing gram-

negative bacteria, and no antibiotics were bactericidal (3-order-of-

magnitude killing) against Staphylococcus aureus. For the very

slowly growing gram-negative bacteria studied, gentamicin (an

aminoglycoside), imipenem (a carbapenem), meropenem (a carbapenem),

ciprofloxacin (a fluoroquinolone), and ofloxacin (a fluoroquinolone)

exhibited up to 5.7 orders of magnitude more killing than

piperacillin or cefotaxime. This is in contrast to optimally growing

bacteria, in which a wide variety of antibiotic classes produced

99.9% killing. For the gram-positive and gram-negative bacteria we

examined, antibiotic killing was greatly dependent on the growth

rate. The clinical implications of slow killing by chemotherapeutic

agents for established bacterial infections and infections involving

foreign bodies are unknown.

[Guest guest]

Very interesting. Gawd, those buggers are crafty. They survive against all odds. penny <usenethod@...> wrote: I may have posted this before. Its a hoary classic from 1991. http://aac.asm.org/cgi/content/abstract/35/9/1824ABSTRACTAntimicrobial agents are most often tested against bacteria in the log phase of multiplication to produce the maximum bactericidal effect. In an infection, bacteria may

multiply less optimally. We examined the effects of several classes of antimicrobial agents to determine their actions on gram-positive and gram-negative bacteria during nongrowing and slowly growing phases. Only ciprofloxacin and ofloxacin exhibited bactericidal activity against nongrowing gram-negative bacteria, and no antibiotics were bactericidal (3-order-of-magnitude killing) against Staphylococcus aureus. For the very slowly growing gram-negative bacteria studied, gentamicin (an aminoglycoside), imipenem (a carbapenem), meropenem (a carbapenem), ciprofloxacin (a fluoroquinolone), and ofloxacin (a fluoroquinolone) exhibited up to 5.7 orders of magnitude more killing than piperacillin or cefotaxime. This is in contrast to optimally growing bacteria, in which a wide variety of antibiotic classes produced 99.9% killing. For the gram-positive and gram-negative bacteria we examined, antibiotic killing was

greatly dependent on the growth rate. The clinical implications of slow killing by chemotherapeutic agents for established bacterial infections and infections involving foreign bodies are unknown.