Susceptibility of Legionella spp. to mycinamicin I and II and other macrolide antibiotics: effects of media composition and origin of organisms

Abstract

Thirty-three strains of Legionella spp., 29 of which were L. pneumophila, were tested for their susceptibilities to erythromycin (EM), rosaramicin, tylosin, mycinamicin I (Sch-27897), and mycinamicin II (Sch-27896). Testing was performed using an agar dilution method with two different types of media: buffered charcoal yeast extract medium supplemented with 0.1% a-ketoglutarate (BCYEa) and filter-sterilized yeast extract medium with 0.1% a-ketoglutarate (BYEa). The minimal inhibitory concentrations (MICs) of the drugs tested relative to the MICs of erythromycin were: rosaramicin, MIC 0.2 EM MIC; tylosin, MIC 2 EM MIC; mycinamicin I, MIC 0.5 EM MIC; and mycinamicin II, MIC EM MIC. Both types of media caused equivalent partial inactivation of the macrolides which was apparently due entirely to pH effect. MICs on BCYEa were one to five times more than those observed on BYEa; this may be due to poorer growth on BYEa.The treatment of choice for Legionnaires disease and other Legionella sp. infections is erythromycin (10,12, 20). Mycinamicins are new macrolide antibiotics with antibacterial spectra similar to the spectrum of erythromycin (17). The purpose of this study was to determine whether two of the mycinamicin compounds had in vitro activity against Legionella sp. similar to other macrolide antibiotics (4,7,13,14,18). In addition, the effect of deletion of activated charcoal from the growth medium was determined, as it is known that charcoal yeast extract (CYE) medium inactivates many antimicrobial agents, including macrolides (4,7,14). This laboratory currently uses a filter-sterilized yeast extract medium without charcoal to test for pigment production of Legionella sp. (15). Since most recent clinical and environmental isolates of L. pneumophila grow readily on this medium, we felt that this medium could be used to grow Legionella sp. for susceptibility testing. Likewise, we felt that study of this charcoal-deleted medium could clarify whether charcoal was the interfering substance in CYE. Additional purposes were to study lower concentrations of rosaramicin than were previously tested (4) and to determine minimal inhibitory concentration (MIC) values on buffered CYE medium supplemented with a-ketoglutarate, since the addition of buffer and a-ketoglutarate to CYE medium dramatically improves the growth of L. pneumophila (3).MATERIALS AND METHODS Media. CYE medium buffered with N-[2-acetamido]-2-aminoethanesulfonic acid (ACES) buffer (Sigma Chemical Co.) and supplemented with 0.1% monopotassium a-ketoglutarate (BCYEa; Sigma Chemical Co.) was made as previously described (3). Buffered yeast extract medium supplemented with 0.1% monopotassium a-ketoglutarate (BYEa) was made with the same quantities of ingredients as for BCYEa except that the activated charcoal was deleted. Also, the yeast extract was filter sterilized with a 0.22-p.m filter (Millipore Corp.) rather than autoclaved; it was added to the autoclaved molten cooled buffer-agar-a-ketoglutarate base at 50°C. The filter-sterilized L-cysteine and ferric p...

WIN 57273 is bactericidal for Legionella pneumophila grown in alveolar macrophages

“…The modified media we used behaved differently from that used by Saito and colleagues and Liebers and colleagues (13,19,20). We and others have previously reported on the failure of modified BCYEo media to support adequate growth of a broad range of Legionella strains (2,8). A possible explanation for these discrepancies is strain variability; we used chiefly low-passage isolates, as opposed to the studies showing better results with modified BCYEa media.…”

“…All legionellae studied were clinical strains isolated by us with the exceptions of TEX-KL, Toronto 3, and Knoxville, which were obtained from William Bibb, Sandu Toma, and William Cherry, respectively (Table 1). All of the non-"named" strains had been passed fewer than three times previously; L. pneumophila serogroup 1 strain F889 has been described previously as Wadsworth strain 82-063A (7 (8). Controls included non-antibiotic-containing media inoculated before and after stamping of each set of antimicrobial agent-containing media and subcultures of inoculum suspensions to assure purity.…”

“…The search for alternatives to erythromycin therapy is compromised by the poor correlation of results of classical in vitro antimicrobial susceptibility testing with clinical experience (7,11,14). This discrepancy is likely due to antimicrobial antagonism by components of the media and to the protected intracellular site in which legioneilae exist.Some investigators have claimed the superiority of one medium over another for the purposes of susceptibility testing, mainly in terms of limited inhibition of antimicrobial agents, but few comparative studies have been performed (2,8,13,20).Antimicrobial treatment of an animal model of Legionnaires disease has demonstrated good correlation with clinical observations, but is too expensive for screening purposes (3, 7, 10, 18-20). To address this, several investigators have validated the use of monocyte or macrophage growth inhibition tests to predict the effectiveness of antimicrobial agents in animal models (1,9,11,(20)(21)(22).…”

“…Some investigators have claimed the superiority of one medium over another for the purposes of susceptibility testing, mainly in terms of limited inhibition of antimicrobial agents, but few comparative studies have been performed (2,8,13,20).…”

Susceptibility of Legionella pneumophila to ofloxacin in vitro and in experimental Legionella pneumonia in guinea pigs

“…Since L. pneumophila produces beta-lactamase, some of the beta-lactam antibiotics have little or no antibacterial activity (5,15,16). Beta-lactam agents of the second or third generation are stable to beta-lactamase and show high activity against L. pneumophila in vitro.…”