In vitro selection of mutants of Streptococcus pneumoniae resistant to macrolides and linezolid: relationship with susceptibility to penicillin G or macrolides

ABSTRACT Selection of resistance to amoxicillin (with or without clavulanate), cefaclor, cefuroxime, and azithromycin among six penicillin G- and azithromycin-susceptible pneumococcal strains and among four strains with intermediate penicillin sensitivities (azithromycin MICs, 0.125 to 4 μg/ml) was studied by performing 50 sequential subcultures in medium with sub-MICs of these antimicrobial agents. For only one of the six penicillin-susceptible strains did subculturing in medium with amoxicillin (with or without clavulanate) lead to an increased MIC, with the MIC rising from 0.008 to 0.125 μg/ml. Five of the six penicillin-susceptible strains showed increased azithromycin MICs (0.5 to >256.0 μg/ml) after 17 to 45 subcultures. Subculturing in medium with cefaclor did not affect the cefaclor MICs of three strains but and led to increased cefaclor MICs (from 0.5 to 2.0 to 4.0 μg/ml) for three of the six strains, with MICs of other β-lactams rising 1 to 3 twofold dilutions. Subculturing in cefuroxime led to increased cefuroxime MICs (from 0.03 to 0.06 μg/ml to 0.125 to 0.5 μg/ml) for all six strains without significantly altering the MICs of other β-lactams, except for one strain, which developed an increased cefaclor MIC. Subculturing in azithromycin did not affect β-lactam MICs. Subculturing of the four strains with decreased penicillin susceptibility in amoxicillin (with or without clavulanate) or cefuroxime did not select for β-lactam resistance. Subculturing of one strain in cefaclor led to an increase in MIC from 0.5 to 2.0 μg/ml after 19 passages. In contrast to strains that were initially azithromycin susceptible, which required >10 subcultures for resistance selection, three of four strains with azithromycin MICs of 0.125 to 4.0 μg/ml showed increased MICs after 7 to 13 passages, with the MICs increasing to 16 to 32 μg/ml. All azithromycin-resistant strains were clarithromycin resistant. With the exception of strains that contained mefE at the onset, no strains that developed resistance to azithromycin containedermB or mefE, genes that have been found in macrolide-resistant pneumococci obtained from clinic patients.

Download Full-text

In vitro selection of resistance in Streptococcus pneumoniae at in vivo fluoroquinolone concentrations

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkp020 ◽

2009 ◽

Vol 63 (4) ◽

pp. 721-727 ◽

Cited By ~ 12

Author(s):

E. De Vecchi ◽

L. Nicola ◽

F. Ossola ◽

L. Drago

Keyword(s):

Streptococcus Pneumoniae ◽

In Vitro Selection ◽

Selection Of ◽

Selection Of Resistance

Download Full-text

Biochemical Characterization of Streptococcus pneumoniae Penicillin-Binding Protein 2b and Its Implication in β-Lactam Resistance

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.48.5.1848-1855.2004 ◽

2004 ◽

Vol 48 (5) ◽

pp. 1848-1855 ◽

Cited By ~ 26

Author(s):

Estelle Pagliero ◽

Laurent Chesnel ◽

Julie Hopkins ◽

Jacques Croizé ◽

Otto Dideberg ◽

...

Keyword(s):

Streptococcus Pneumoniae ◽

Biochemical Characterization ◽

Protein A ◽

Strain Analysis ◽

Penicillin G ◽

Penicillin Binding Protein ◽

Class B ◽

Selection Of

ABSTRACT Extensive use of β-lactam antibiotics has led to the selection of pathogenic streptococci resistant to β-lactams due to modifications of the penicillin-binding proteins (PBPs). PBP2b from Streptococcus pneumoniae is a monofunctional (class B) high-molecular-weight PBP catalyzing the transpeptidation between adjacent stem peptides of peptidoglycan. The transpeptidase domain of PBP2b isolated from seven clinical resistant (CR) strains contains 7 to 44 amino acid changes over the sequence of PBP2b from the R6 β-lactam-sensitive strain. We show that the extracellular soluble domains of recombinant PBP2b proteins (PBP2b*) originating from these CR strains have an in vitro affinity for penicillin G that is reduced by up to 99% from that of the R6 strain. The Thr446Ala mutation is always observed in CR strains and is close to the key conserved motif (S443SN). The Thr446Ala mutation in R6 PBP2b* displays a 60% reduction in penicillin G affinity in vitro compared to that for the wild-type protein. A recombinant R6 strain expressing the R6 PBP2b Thr446Ala mutation is twofold less sensitive to piperacillin than the parental S. pneumoniae strain. Analysis of the Thr446Ala mutation in the context of the PBP2b CR sequences revealed that its influence depends upon the presence of other unidentified mutations.

Download Full-text

Topoisomerase Mutations Associated with In Vitro Selection of Resistance to Moxifloxacin in Streptococcus pneumoniae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.46.8.2712-2715.2002 ◽

2002 ◽

Vol 46 (8) ◽

pp. 2712-2715 ◽

Cited By ~ 25

Author(s):

Serge Houssaye ◽

Laurent Gutmann ◽

Emmanuelle Varon

Keyword(s):

Streptococcus Pneumoniae ◽

In Vitro Selection ◽

Second Step ◽

Wild Type ◽

Topoisomerase Iv ◽

Selection Step ◽

Gyra Mutation ◽

Selection Of ◽

Selection Of Resistance

ABSTRACT We analyzed the frequencies of selection, the order of acquisition, and the mutations selected on moxifloxacin in two wild-type pneumococcal strains, R6 and 5714. The first selection step showed either a single GyrA mutation or no mutation in any of the quinolone resistance-determining regions. Second-step mutants selected had either a second mutation in ParC or in ParE. Moxifloxacin could belong to these fluoroquinolones, which preferentially target GyrA though probably acting equally through both gyrase and topoisomerase IV.

Download Full-text

Faculty Opinions recommendation of In vitro selection of a deoxyribozyme that can utilize multiple substrates.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1004319.49956 ◽

2002 ◽

Author(s):

Niles Lehman

Keyword(s):

In Vitro Selection ◽

Multiple Substrates ◽

Selection Of

Download Full-text

Faculty Opinions recommendation of CIS display: In vitro selection of peptides from libraries of protein-DNA complexes.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1017658.206556 ◽

2004 ◽

Author(s):

Sachdev Sidhu

Keyword(s):

In Vitro Selection ◽

Dna Complexes ◽

Selection Of

Download Full-text

The Effects of Shock Vancomycin Concentrations on the Formation of Heteroresistance in Staphylococcus aureus

Antibiotics and Chemotherapy ◽

10.37489/0235-2990-2020-65-9-10-3-7 ◽

2020 ◽

Vol 65 (9-10) ◽

pp. 3-7

Author(s):

V. V. Gostev ◽

Yu. V. Sopova ◽

O. S. Kalinogorskaya ◽

M. E. Velizhanina ◽

I. V. Lazareva ◽

...

Keyword(s):

Staphylococcus Aureus ◽

In Vitro Selection ◽

Methicillin Resistant Staphylococcus Aureus ◽

High Concentration ◽

Short Term ◽

High Concentrations ◽

Selection Of ◽

Selection Of Resistance ◽

Test Cultures

Glycopeptides are the basis of the treatment of infections caused by MRSA (Methicillin-Resistant Staphylococcus aureus). Previously, it was demonstrated that antibiotic tolerant phenotypes are formed during selection of resistance under the influence of high concentrations of antibiotics. The present study uses a similar in vitro selection model with vancomycin. Clinical isolates of MRSA belonging to genetic lines ST8 and ST239, as well as the MSSA (ATCC29213) strain, were included in the experiment. Test isolates were incubated for five hours in a medium with a high concentration of vancomycin (50 μg/ml). Test cultures were grown on the medium without antibiotic for 18 hours after each exposure. A total of ten exposure cycles were performed. Vancomycin was characterized by bacteriostatic action; the proportion of surviving cells after exposure was 70–100%. After selection, there was a slight increase in the MIC to vancomycin (MIC 2 μg/ml), teicoplanin (MIC 1.5–3 μg/ml) and daptomycin (MIC 0.25–2 μg/ml). According to the results of PAP analysis, all strains showed an increase in the area under curve depending on the concentration of vancomycin after selection, while a heteroresistant phenotype (with PAP/AUC 0.9) was detected in three isolates. All isolates showed walK mutations (T188S, D235N, E261V, V380I, and G223D). Exposure to short-term shock concentrations of vancomycin promotes the formation of heteroresistance in both MRSA and MSSA. Formation of VISA phenotypes is possible during therapy with vancomycin.

Download Full-text