Influence of several antibiotics, singly and in combination, on the growth of listeria monocytogenes

Penicillins are considered to be the drugs of choice for the treatment of listeric meningitis, and relapse of infection is rare when treatment is given in appropriate doses for at least 14 days. Despite this, in vitro studies by others have shown that penicillins are bacteriostatic against Listeria spp. We have shown that thienamycin, penicillin G, and ampicillin are the most active ,-lactam antibiotics against Listeria spp. Of 10 strains tested, 9 were killed by -s8 ,ug of P-lactam antibiotics (.99.9% killing) when subcultures were performed after 48, rather than 24, h of incubation. In contrast, chloramphenicol, erythromycin, doxycycline, and rifampin were bacteriostatic after 48 h of incubation. In time-kill curves, these last drugs antagonized the bactericidal action of penicillins. In view of the inefficiency of opsonization in the cerebrospinal fluid, these antagonistic combinations should probably be avoided in documented or suspected listeric meningitis.

mentioning

confidence: 99%

Delayed bactericidal activity of beta-lactam antibiotics against Listeria monocytogenes: antagonism of chloramphenicol and rifampin

Winslow¹,

Damme²,

Dieckman³

1983

“…Standard therapy with ampicillin or penicillin G may result in relapse (19,22,28,30) This may be related to the fact that many strains of Listeria, although inhibited by relatively low concentrations of penicillin, require much higher levels for bactericidal effect (14,20). Alternative drugs include tetracyclines, erythromycin, and chloramphenicol, which are also bacteriostatic in activity against Listeria (15,32).…”

mentioning

confidence: 99%

“…Alternative drugs include tetracyclines, erythromycin, and chloramphenicol, which are also bacteriostatic in activity against Listeria (15,32). Although the addition of aminoglycosides to a penicillin results in enhanced in vitro killing (14,20) and improved survival in some animal models of listeric infection (9,26), the clinical superiority of combination therapy has not been established. There is no bactericidal antibiotic for use in penicillin-allergic patients.…”

mentioning

confidence: 99%

In vitro activities of trimethoprim and sulfamethoxazole against Listeria monocytogenes

Winslow¹,

Ga²

1982

The in vitro activities of trimethoprim and sulfamethoxazole against clinical isolates of Listeria monocytogenes were examined separately and in combination with a microtiter broth dilution system. Sulfamethoxazole demonstrated variable activity and was generally bacteriostatic. Trimethoprim alone was bactericidal against 96% of isolates at c0.5 jig/ml. The bactericidal action of trimethoprim against L. monocytogenes was generally potentiated by sulfamethoxazole even when isolates were relatively resistant to sulfamethoxazole alone.

“…In addition, Eliopoulos and Moellering have shown a synergistic killing effect in vitro by the addition of gentamicin to imipenem (9), which similar to the effect seen with ampicillin-gentamicin combinations (11,19,26). The present study therefore was performed to evaluate and compare the in vivo efficacies of imipenem and ampicillin alone and in combination with gentamicin against L. monocytogenes.…”

Section: Discussionmentioning

confidence: 91%

“…However, in penicillin-allergic patients, a suitable alternative agent has not been clearly established. Tetracycline, chloramphenicol, and erythromycin have been suggested, but they are bacteriostatic against L. monocytogenes, and potential antagonism exists with the use of tetracycline and chloramphenicol (11,31). Trimethoprim-sulfamethoxazole has been shown to be bactericidal in vitro against L. monocytogenes (33), but its in vivo activity has not been reported.…”

Section: Discussionmentioning

confidence: 99%

In vitro and in vivo studies of imipenem-cilastatin alone and in combination with gentamicin against Listeria monocytogenes

Kim

1986

Listeria monocytogenes is an important cause of bacteremia and meningitis in neonates and immunocompromised patients (7,10,12,17,20,22). Although penicillin G and ampicillin (with or without an aminoglycoside) are considered the drugs of choice for the treatment of Listeria infection, there is a need for alternative drugs in cases of penicillin-allergic patients and in therapeutic failures (2, 30).'Imipenem (N-formimidoyl thienamycin), unlike newer cephalosporins, appears to be a promising candidate because of its excellent in vitro activity against L. monocytogenes with an MIC for 90% of strains tested of s 0.12 ,ug/ml (9,13,21,31). In addition, combinations of imipenem-gentamicin have been shown to be synergistic in vitro against L. monocytogenes (9). However, in vivo evaluation of imipenem against L. monocytogenes has not been reported. The present study therefore was performed to examine the in vitro and in vivo activities of imipenem and imipenemgentamicin in comparison with ampicillin and ampicillingentamicin against L. monocytogenes. MATERIALS AND METHODSOrganism. A clinical strain of L. monocytogenes (strain LM2) that was isolated from the blood of an infant with sepsis was used in the in vitro and in vivo experiments.In vitro studies. MICs and MBCs were measured in Todd-Hewitt broth (Difco Laboratories, Detroit, Mich.) by the standard macrobroth dilution method (29). The antimicrobial agents tested were imipenem (Merck Sharp & Dohme Research Laboratories, Rahway, N.J.), ampicillin trihydrate (Bristol Laboratories, Syracuse, N.Y.), and gentamicin sulfate (Schering Corp., Kenilworth, N.J.). Antimicrobial agents were diluted serially twofold from 16 to 0.03 ,ug/ml in Todd-Hewitt broth. An inoculum of approximately 5 x 105 CFUJ of L. monocytogenes per ml was prepared from late logarithmic phase cultures. Equal volumes (0.5 ml) of antibiotic and bacterial dilutions were mixed and incubated at 37°C for 24 h. The MIC was defined as the lowest antibiotic concentration exhibiting no visual turbidity. From each tube, 0.01 ml was transferred to a quadrant of sheep blood agar ahd incubated at 37°C for 24 h to determine the MBC, which was defined as the lowest concentration of antibiotics resulting in -99.9% killing of the original ipoculum.The MICs and MBCs of imipenem-gentamicin and ampicillin-gentamicin were measured in Todd-Hewitt broth (1). Twofold dilutions of each antibiotic were used in a checkerboard fashion. MIC and MBC endpoints were read as described above for each antibiotic alone and in various combinations. The results were expressed as the fractional bactericidal concentration index, which was calculated by the following formula (3, 23): (MBC of drug A in combination with drug B/MBC of drug A) + (MBC of drug B in combination with drug A/MBC of drug B) (for studies of imipenem-gentamicin, drug A was imipenem and drug B was gentamicin, or vice versa; for studies of ampicillingentamicin, drug A was ampicillin and drug B was gentamicin, or vice versa). When the FBC index was less than 0.5, the combinatio...