Analysis of acquired ciprofloxacin resistance in a clinical strain of Pseudomonas aeruginosa

A series of 11 fluoroqulnolone antibacterial agents, including 8 newly synthesized molecules and 3 reference compounds (pefloxacin, ciprofloxacin, and sparfioxacin), were forE. coi, which were 0.60, 0.64, and 0.74 (n = 11) for E. coil, P. aerugunosa, and S. awwus, respectively, rose to 0.85, 0.74, and 0.74 (n = 11) for the same microorganisms, respectively, when the accumulatin of the drug by the cell was taken into account. It WAs concluded that the inhibitory activity against DNA gyrase remains the most important parameter for quinolone potency, but that intracellular accumulation must be tahken into account, since, for a given organism, both parameters are under the control of the physicochemical properties of the qulnolones.The MIC of a quinolone against a particular organism is determined by at least two factors: its rate of penetration across the bacterial cell envelope (31, 34) and its inhibitory activity against the supercoiling reaction catalyzed by its target, the enzyme DNA gyrase (15). Although both of these activities should be at their optimum to ensure the maxmal antibacterial potency of a compound, it is evident that the second of these properties is the more important, since a qumolone devoid of activity against DNA gyrase is not active against a bacterium, despite sufficient drug accumulation. Moreover, it has been documented that most highlevel quinolone resistance arises from gyrase modifications (13,30,35,38,44). Conversely, poor penetration into bacteria may impair the effectiveness of a quinolone that is highly active against gyrase. This could explain the lack of a clear correlation between antibacterial activity and inhibition of isolated DNA gyrase observed for some quinolones (2, 15). Several studies dealing with the structure-activity relationships of fluoroquinolones have been published (3, 10-12, 15, 16, 18, 24, 36), and the investigators sometimes attempted to identify separately those factors that are necessary for gyrase inhibition from those that are needed for penetration into the cell. With regard to penetration into the bacterial cell, physical properties such as relative hydrophobicity (23, 28) or charge or molecular weight (7,8,31) are important. As a general rule, bulky size, negative charge, and increasing hydrophobicity retard the penetration of antibacterial agents into gram-negative organisms through porn channels (9,20,21), although hydrophobic molecules appear to use an alternative route, through lipopolysaccha-* Corresponding author. ride (8). For gram-positive organisms, the molecular weight of the antimicrobial agent has little influence on the agent's potency, and positively charged hydrophobic molecules have been shown to have a better rate of penetration (17,19).The structural features necessary for enzyme inhibition appear to be different from those required for penetration, and analysis of these features is more complex (10,24).We have at our disposal a series of fluoroquinolones with a wide range of hydrophobicities (logarithm of the coefficient of distri...

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confidence: 50%

Relationships among antibacterial activity, inhibition of DNA gyrase, and intracellular accumulation of 11 fluoroquinolones

Bazile

Moreau

Bouzard

et al. 1992

“…While several strains with decreased susceptibilities to several agents have been isolated, which suggests a mutation in nalB, there are biochemical differences that are commensurate with different mutations encoding multiple resistance. Some quinolone-resistant P. aeruginosa strains contain a new 54-kDa outer membrane protein (14, 18) or lack a 31.5-kDa outer membrane protein (9, 17), possibly OprF, or have decreased levels of proteins D2 and Hi or Gl (5,20,23). Several workers have also reported changes in lipopolysaccharide (LPS) (6,18,34).…”

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confidence: 98%

“…Quinolone-resistant P. aeruginosa isolated from patients may also have the nal4 or nalB phenotype (43) or a nalB-like phenotype lacking OprF. Such strains have been isolated from patients with chronic obstructive airway disease (30), burn wound sepsis (17), cystic fibrosis (6), and empyema (20). While several strains with decreased susceptibilities to several agents have been isolated, which suggests a mutation in nalB, there are biochemical differences that are commensurate with different mutations encoding multiple resistance.…”

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confidence: 99%

A pleiotropic, posttherapy, enoxacin-resistant mutant of Pseudomonas aeruginosa

Piddock

Hall

Bellido

et al. 1992

An enoxacin-resistant Pseudomonas aeruginosa mutant (G49) isolated during patient therapy was characterized in detail. The G49 mutant was cross resistant to several classes of antibiotics including quinolones, I-lactams, chloramphenicol, and tetracycline, but not imipenem or aminoglycosides. Compared with its paired pretherapy isolate G48, this mutant had several alterations in outer membrane proteins including a complete loss of the major porin protein OprF and a substantially altered lipopolysaccharide profile. Revertants were selected at a frequency of approximately 1% after enrichment for OprF+ cells on low-salt proteose peptone no. 2 medium. Ninety-seven of these OprF+ revertants were as susceptible to carbenicillin and norfloxacin as the pretherapy isolate. One of these revertants was characterized in more detail and shown to be indistinguishable in all properties from the pretherapy isolate. It is proposed that the multiple-antibiotic-resistance (Mar) phenotype of this mutant resulted from a single pleiotropic mutation.Enoxacin is a difluorinated quinolone with strong activity for gram-negative bacteria (7,41). Enoxacin is now marketed in 11 countries, including South America, the United Kingdom, and other parts of Europe, for use in the therapy of urinary tract infections and in some countries for respiratory tract infections. As in other bacteria, the primary target for quinolones in Pseudomonas aeruginosa is DNA gyrase. nalA, nfxA, norA, and cipA are alleles ofgyrA and encode A subunits that are less susceptible to inhibition by quinolones (14,16,33,34). Other mutations affecting quinolone activity, but not DNA gyrase, in P. aeruginosa have also been described. Many laboratory mutants contain alleles of nalB and require nalidixic acid MICs of >500 ,ug/ml and are cross resistant to carbenicillin, ureidopenicillins, chloramphenicol, and novobiocin (33, 34). Resistant strains have arisen during experimental P. aeruginosa infections, with several classes of mutants isolated with mutations resembling naL4 and nfxC (10,22,23). Quinolone-resistant P. aeruginosa isolated from patients may also have the nal4 or nalB phenotype (43) or a nalB-like phenotype lacking OprF. Such strains have been isolated from patients with chronic obstructive airway disease (30), burn wound sepsis (17), cystic fibrosis (6), and empyema (20). While several strains with decreased susceptibilities to several agents have been isolated, which suggests a mutation in nalB, there are biochemical differences that are commensurate with different mutations encoding multiple resistance. Some quinolone-resistant P. aeruginosa strains contain a new 54-kDa outer membrane protein (14, 18) or lack a 31.5-kDa outer membrane protein (9, 17), possibly OprF, or have decreased levels of proteins D2 and Hi or Gl (5,20,23). Several workers have also reported changes in lipopolysaccharide (LPS) (6,18,34).An open study to evaluate the efficacy of enoxacin in respiratory tract infections with particular attention to those caused by P. aeruginosa was perform...

“…For most isolates of Enterobacteriaceae, the genetic basis for this fluoroquinolone resistance remains obscure. In P. aeruginosa, which is less susceptible to fluoroquinolones, biochemical and genetic data revealed gyrase mutations or permeability mutations alone or in combination to be responsible for clinical fluoroquinolone resistance (9,31 Table 1. E. coli K-12 strains used in this study were C600S (26), which is a recA derivative of C600 (thr leu thi lacY tonA supE44 hsdR rpsL [3]) and its gyrA derivative, C600SN (48a); JM83 (47); KL16nal-31 (gyrB [24]), obtained from J. T. Smith; and JF703 (ompF [8]), obtained from B. Bachman, E. coli Genetic Stock Center.…”

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confidence: 99%

Use of a broad-host-range gyrA plasmid for genetic characterization of fluoroquinolone-resistant gram-negative bacteria

Heisig

Wiedemann

1991

Mutations in the target enzyme, gyrase, have been found in both gram-negative (12, 37, 52) and gram-positive (27,44) quinolone-resistant bacteria. Mutations in the gyrB locus were identified in two strains of Escherichia coli K-12 (50) and in one isolate of P. aeruginosa (52). All three mutants have low-level resistance to quinolones with incomplete cross-resistance between fluorinated and unfluorinated compounds.gyrA mutants typically show increased MICs of all quinolone drugs (51). However, examination of E. coli isolates with reduced quinolone susceptibilities by determination of the DNA sequences of the respective gyrA genes revealed single-step mutations to be responsible for quinolone resistance (12,37,51