Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pyocyanine”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources
PubMed1997

Microcystin LR degradation by Pseudomonas aeruginosa alkaline protease.

We isolated several species of bacteria from the surface water of a Japanese lake. Of the isolated bacteria, Pseudomonas aeruginosa was the only species which could degrade microcystin LR in vitro. Microcystin LR decreased to 4.5% of the spiked microcystin LR quantity in the P. aeruginosa culture, and was metabolized to (2S, 3S, 8S)-3-amino-2, 6, 8-trimethyl-10-phenyldeca-4E, 6E-dienoic acid (DmADDA). It was possible that P. aeruginosa hydrolysed nucleophilically the peptide bond of microcystin LR. We examined if pyochelin, pyocyanin and alkaline protease produced by P. aeruginosa affected the reduction of microcystin LR. In the result, DmADDA was produced from microcystin LR in the presence of 100 microM H2O2 and 100 microM each of pyochelin, pyocyanin or both. However, the production of DmADDA was slight (2 to 12 mole%). After treatment with P. aeruginosa alkaline protease, DmADDA was produced 75 mole% from microcystin LR. Therefore, we concluded that microcystin was degraded mainly by the action of P. aeruginosa alkaline protease.

Amino Acids↗
PubMed1984

Characterization of pseudomonads isolated from diseased fleece.

A total of 59 Pseudomonas isolates was obtained from 11 samples of diseased fleece taken from live sheep. All but four of the isolates could be assigned to one of nine Pseudomonas species, of which P. aeruginosa, P. alcaligenes, P. mendocina , and P. putida were the most common. P. aeruginosa was found in four of the fleece samples and, when present, appeared to predominate. Although several of the isolates of P. aeruginosa lacked the ability to produce pyocyanin (and some produced neither pyocyanin nor fluorescein), nearly all produced several virulence factors. Of the other pseudomonads, many produced proteinase, esterase, and catalase, several were able to grow at 42 degrees C and reduce nitrate, and some also produced lipase and hemolysin and, like P. aeruginosa, might serve to initiate (or sustain) the dermatitis frequently associated with fleece rot in sheep.

Animals↗
PubMed1995

Synthesis of multiple exoproducts in Pseudomonas aeruginosa is under the control of RhlR-RhlI, another set of regulators in strain PAO1 with homology to the autoinducer-responsive LuxR-LuxI family.

Mutants of Pseudomonas aeruginosa PAO1 that were deficient in the ability to produce proteases that degrade casein were detected among the survivors of chemical mutagenesis. One such mutant (PDO31) showed reduced production of elastolytic activity, beta-hemolytic activity, and pyocyanin. A 4.3-kb EcoRI fragment from a gene bank of PAO1 that complemented defects in PDO31 was found. Transposon mutagenesis and deletion derivatives of the clone were used in conjunction with complementation tests to determine the physical location of the gene of interest. Nucleotide sequence analysis revealed an open reading frame (rhlR) encoding a putative 27.6-kDa protein (RhlR) with homology to autoinducer-responsive regulators of quorum sensing systems such as LuxR of Vibrio fischeri and LasR of P. aeruginosa. Further sequence analysis downstream of rhlR revealed an independently transcribed gene (rhlI) that encodes a putative 22.2-kDa protein with homology to members of the family of autoinducer synthetases, such as LuxI of V. fischeri and LasI of P. aeruginosa. The rhlRI sequences were also recently reported by others (U.A. Ochsner and J. Reiser, Proc. Natl. Acad. Sci. USA 92: 6424-6428, 1995) as an autoinducer-mediated regulation mechanism for rhamnolipid biosurfactant synthesis in P. aeruginosa PG201. Mutants with defects in rhlR or rhlI were constructed in PAO1 by gene replacement, using clones modified by Tn501 insertion. Compared with the wild type, the rhlR and rhlI mutants both showed defects in the production of elastase, LasA protease, rhamnolipid, and pyocyanin. Transcription from the gene for elastase, as measured with a lasB-cat fusion, demonstrated that production of elastase was subject to cell density-dependent gene activation in PAO1. However, transcription of lasB-cat in the rhlI mutant, which had lost the presumptive autoinducer synthetase (predicted to activate RhlR), showed low basal activity and had lost all cell density-dependent transcription of lasB. Thus, RhlR-RhlI represent the second autoinducer-responsive regulatory mechanism found in P. aeruginosa that controls expression of multiple virulence factor exoproducts, including elastase.

Bacterial Proteins↗
PubMed1999

Effect of rpoS mutation on the stress response and expression of virulence factors in Pseudomonas aeruginosa.

The sigma factor RpoS (sigmaS) has been described as a general stress response regulator that controls the expression of genes which confer increased resistance to various stresses in some gram-negative bacteria. To elucidate the role of RpoS in Pseudomonas aeruginosa physiology and pathogenesis, we constructed rpoS mutants in several strains of P. aeruginosa, including PAO1. The PAO1 rpoS mutant was subjected to various environmental stresses, and we compared the resistance phenotype of the mutant to that of the parent. The PAO1 rpoS mutant was slightly more sensitive to carbon starvation than the wild-type strain, but this phenotype was obvious only when the cells were grown in a medium supplemented with glucose as the sole carbon source. In addition, the PAO1 rpoS mutant was hypersensitive to heat shock at 50 degrees C, increased osmolarity, and prolonged exposure to high concentrations of H2O2. In accordance with the hypersensitivity to H2O2, catalase production was 60% lower in the rpoS mutant than in the parent strain. We also assessed the role of RpoS in the production of several exoproducts known to be important for virulence of P. aeruginosa. The rpoS mutant produced 50% less exotoxin A, but it produced only slightly smaller amounts of elastase and LasA protease than the parent strain. The levels of phospholipase C and casein-degrading proteases were unaffected by a mutation in rpoS in PAO1. The rpoS mutation resulted in the increased production of the phenazine antibiotic pyocyanin and the siderophore pyoverdine. This increased pyocyanin production may be responsible for the enhanced virulence of the PAO1 rpoS mutant that was observed in a rat chronic-lung-infection model. In addition, the rpoS mutant displayed an altered twitching-motility phenotype, suggesting that the colonization factors, type IV fimbriae, were affected. Finally, in an alginate-overproducing cystic fibrosis (CF) isolate, FRD1, the rpoS101::aacCI mutation almost completely abolished the production of alginate when the bacterium was grown in a liquid medium. On a solid medium, the FRD1 rpoS mutant produced approximately 70% less alginate than did the wild-type strain. Thus, our data indicate that although some of the functions of RpoS in P. aeruginosa physiology are similar to RpoS functions in other gram-negative bacteria, it also has some functions unique to this bacterium.

Alginates↗
PubMed2026

Intra-strain genomic microevolution and phage resistance in Pseudomonas aeruginosa PAO1 laboratory isolates.

Pseudomonas aeruginosa is a major opportunistic pathogen, and its laboratory reference strain, PAO1, is widely used in microbiological and genetic studies. However, PAO1 often exhibits phenotypic variability that can affect experimental reproducibility. Our PAO1 stock, obtained from a public biobank, is resistant to PP7, a pilus-dependent single-stranded RNA phage known to infect PAO1. This suggests the presence of genetic variants in the stock. To check this possibility, we isolated six phenotypically distinct variants (GU1-GU6) and performed genomic and phenotypic analyses. Notable differences were observed among the isolates in terms of motility, pyocyanin production, and susceptibility to PP7. Whole-genome sequencing revealed that four of the six variants harbored mutations in pilus-associated genes. Among these, GU3 carried a mutation in pilT, which encodes a motor protein essential for type IV pilus retraction, and the loss of retraction led to the PP7 resistance. GU2, GU4, and GU6 shared a nonsense mutation in pilJ, a gene involved in chemotaxis and pilus extension, resulting in reduced twitching motility and lower PP7 infection efficiency. Additionally, we found that a mutation in lasR, a master regulator of quorum sensing, promoted the replication of prophage Pf6, which was integrated into the PAO1 genome. Pf6 replication interferes with PP7 infection, providing an alternative mechanism of resistance. These findings offer new insights into the complexity of phage-host interactions and emphasize the importance of routine verification and careful handling of P. aeruginosa sublines used in bacteriological and phage research.IMPORTANCEPhenotypic and genotypic variability in Pseudomonas aeruginosa PAO1 has been widely reported, raising concerns regarding the reproducibility of laboratory studies that rely on this reference strain. In this study, we isolated six PAO1 variants from a single laboratory stock and demonstrated that they differed markedly in motility, pyocyanin production, and susceptibility to the ssRNA phage PP7. Whole-genome sequencing has revealed that even a single mutation in a pilus-associated gene can profoundly affect bacterial motility and phage susceptibility. Furthermore, we showed that a mutation in lasR, a key regulator of the quorum-sensing system, triggered replication of the Pf6 prophage, which in turn hindered PP7 infection. These findings underscore the dynamic nature of laboratory strains and highlight the need for caution when interpreting results from phage-host interaction studies using reference strains. Our results provide a new understanding of how subtle genetic changes in model strains influence experimental outcomes in microbiology.

Pseudomonas aeruginosa↗
PubMed1965

Use of an improved cetrimide agar medium and other culture methods for Pseudomonas aeruginosa.

In a comparison of two selective media for Ps. aeruginosa containing 0.03% cetrimide, stronger fluorescence was obtained from growth on the medium prepared with King's medium B as the base (CTA 2); although Ps. aeruginosa was not isolated more frequently from burns on this medium than from cetrimide agar made with a Lemco base (CTA 1), results were easier to assess and there were fewer cases of doubtful fluorescence on CTA 2 than on CTA 1. Pyocyanin production on CTA 1 was better than on CTA 2, but for demonstration of pyocyanin production Wahba and Darrell's medium was preferable and showed the pigment in 455/497 (92%) of fluorescent strains of Ps. aeruginosa from burns.A series of tests on 99 strains of Ps. aeruginosa or presumptive Ps. aeruginosa, on 30 strains of other species of Pseudomonas, and on 68 strains of other species of Gram-negative rods showed the value of growth on cetrimide agar and on triphenyl tetrazolium chloride medium, of slime production in gluconate broth, of gas production from nitrate, and of growth at 42 degrees C. as diagnostic aids in the recognition of Ps. aeruginosa.

Culture Media↗
PubMed2003

Phenazine-1-carboxylic acid, a secondary metabolite of Pseudomonas aeruginosa, alters expression of immunomodulatory proteins by human airway epithelial cells.

Pseudomonas aeruginosa is a gram-negative bacterium that causes both acute and chronic lung disease in susceptible patient populations. P. aeruginosa secretes numerous proteins and secondary metabolites, many of which have biological effects that likely contribute to disease pathogenesis. An unidentified small-molecular-weight factor was previously reported to increase IL-8 release both in vitro and in vivo. To identify this factor, we subjected the <3-kDa fraction from P. aeruginosa-conditioned medium to HPLC analysis. A peak fraction that stimulated IL-8 release was found by mass spectrometry to have a molecular mass (MM) of 224 Da. On the basis of this MM and other biochemical properties, we hypothesized that the factor was phenazine-1-carboxylic acid (PCA). Subsequent studies and comparison with purified PCA confirmed this hypothesis. Purified PCA exhibited a number of biological effects in human airway epithelial cells, including increasing IL-8 release and ICAM-1 expression, as well as decreasing RANTES and monocyte chemoattractant protein-1 (MCP-1) release. PCA also increased intracellular oxidant formation as measured by electron paramagnetic resonance and by an intracellular oxidant-sensitive probe. Antioxidants inhibited PCA-dependent increases in IL-8 and ICAM-1, suggesting that oxidants contributed to these effects. However, in contrast to the related phenazine compound pyocyanin, PCA did not oxidize NAD(P)H at physiologically relevant pH, providing preliminary evidence that PCA and pyocyanin may have distinct redox chemistries within the cell. Thus PCA is a biologically active factor secreted by P. aeruginosa that has several activities that could alter the host immune and inflammatory response and thereby contribute to bacterial disease pathogenesis.

Adjuvants, Immunologic↗
PubMed2002

[A case of immotile-dyskinetic cilia syndrome responding to clenbuterol hydrochloride and azithromycin].

In this case, a 30-year-old man had been treated for chronic sinusitis and bronchiectasis since 2000, and presented at our outpatient clinic in May 2001 with chief complaints of massive yellow sputum expectoration and dyspnea. After he was admitted by our hospital, Pseudomonas aeruginosa bacteria were isolated at the rate of 10(8)/ml from his sputum culture. In electron-microscopic observation, the cilia of the bronchial epithelium were found to lack dynein arms. Semen examination revealed decreased sperm motility. Thus, the following diagnosis was made: diffuse bronchiectasis associated with the immotile-dyskinetic cilia syndrome, complicated with a P. aeruginosa infection. After the airway infection was ameliorated, 40 mg/day of clenbuterol hydrochloride was administered in combination with 250 mg of azithromycin, which was given twice a week, and which led to a markedly decreased frequency of exacerbation of airway infection. Moreover, chest CT scanning and respiratory function testing also indicated improvements. It was hypothesized that the decreased cilia motility due to P. aeruginosa-produced pyocyanin would be ameliorated with a b2 stimulant, and the inhibitory effect of a macrolide on the P. aeruginosa biofilm and production of pyocyanin would also be involved in the improvement of this case.

Adult↗
PubMed1982

Properties of 5-methylphenazinium methyl sulfate. Reaction of the oxidized form with NADH and of the reduced form with oxygen.

Rapid-scan and fixed-wavelength stopped-flow spectrophotometry were used to characterize the 5-methylphenazinium methyl sulfate (PMS)/reduced nicotinamide adenine dinucleotide couple at pH 7.4. Under anaerobic conditions, NADH reduces PMS to 5,10-dihydro-5-methylphenazine with a second order rate constant of 3.8 +/- 0.4 X 10(3) M-1 s-1. Oxygen reacts with 5,10-dihydro-5-methylphenazine to form PMS with a rate constant of about 180 M-1 s-1. When NADH reacts with PMS under aerobic conditions, a situation commonly encountered in carrying out routine enzymatic assays, the NADH reduction reaction and the O2 oxidation reaction proceed simultaneously with rate constants essentially the same as those determined for the two isolated reactions. The anaerobic photoreaction of PMS at pH = 7.4, which was studied by optical absorption spectroscopy, produces the 1-hydroxy-5-methylphenazinium cation (pyocyanine) and 5,10-dihydro-5-methylphenazine in nearly equal concentrations. When oxygen is present, the only detectable product is pyocyanine. These results, particularly the relatively slow rate of reaction between PMS and NADH, are used to point out potential complications in the use of the PMS/NADH couple.

Anaerobiosis↗
PubMed1996

Ultraviolet-B lethal damage on Pseudomonas aeruginosa.

Pseudomonas aeruginosa has shown an increased sensitivity compared with that of Escherichia coli and Enterobacter cloacae, when they were exposed to 0.4 kJ/m2 of ultraviolet-B radiation. The rapid decay in cell viability observed in Pseudomonas aeruginosa after the irradiation was influenced by factors such as culture media and the presence of pyocyanine during the irradiation. The radioinduced lethal damage could be prevented by photoreactivating treatment, indicating that pyrimidine dimer formation was the mechanism causing bacterial death. The results indicate that several environmental conditions may act as protective agents against ultraviolet-B-induced damage.

Cell Death↗
PubMed1975

Light-induced turnover of chloroplast cytochrome b-559 in the presence of N-methylphenazonium methosulphate.

In the presence of 0.1-5 muM N-methylphenazonium methosulphate approx. 50-70% oxidation of cytochrome b-559 can be induced by far-red light. The oxidation is best observed with long wavelength far-red light (732 nm) of moderate intensities (approx. 10(4) ergs/cm2 per s) and is reversed by subsequent illumination with red light. Concentrations of N-methylphenazonium methosulphate above 5 muM are inhibitory probably due to cyclic electron flow. The far-red oxidation is inhibited by low concentrations of the plastoquinone antagonist 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, while 3-(3,4-dichlorophenyl)-1,1-dimethylurea inhibits red light reduction and increases the amplitude of far-red oxidation. The effect of N-methylphenazonium methosulphate is mimicked by N-methyl-phenazonium ethosulphate, but not by pyocyanine or diaminodurene. Low concentrations (2-3 muM) of N-methylphenazonium methosulphate also stimulate a 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone-inhibitable red light reduction of cytochrome f.

Chlorophyll↗
PubMed1980

Regulation of fructose-1,6-biphosphatase activity in intact chloroplasts. Studies of the mechanism of inactivation.

1. The aim of this work was to investigate the mechanism of dark inactivation of fructose-1,6-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) in isolated intact chloroplasts of Triticum aestivum. 2. Dark inactivation of the enzyme, which was rapid under aerobic conditions, was prevented under anaerobic conditions when chloroplasts were incubated in the absence of an electron acceptor. Electron acceptors such as oxaloacetate readily brought about inactivation under anaerobic conditions whether chloroplasts were illuminated or in the dark. Inactivation of the enzyme also occurred if illuminated or darkened anaerobic chloroplasts were exposed to oxygen. 3. Pyocyanine, which catalyses a cyclic electron flow around Photosystem I, also caused inactivation of the enzyme in illuminated, anaerobic chloroplasts. 4. It is proposed that the activity of fructose-1,6-bisphosphatase is regulated by the availability of electrons, and thus by electron acceptors, and that dark inactivation may occur by a direct reversal of the activation process.

Anaerobiosis↗
PubMed2005

Pathogenicity of gacA mutant of Pseudomonas aeruginosa PA01 in the silkworm, Bombyx mori.

To investigate the pathogenicity of Pseudomonas aeruginosa in insects, a gacA mutant of P. aeruginosa PA01 was constructed by site-directed mutagenesis. The mutant was designated as C1. C1 was less virulent to Bombyx mori than the parent strain. To complement the gacA gene, P. aeruginosa C1 was transformed with the broad host range plasmid pJB3Km1 carrying a 3.9-kbp gacA fragment. The expression of the gacA mRNA in C1 (pgacA) was detected. In addition, the complemented mutant restored the level and timing of pyocyanin production, indicating that functional GacA is produced in the complemented strain. However, no significant difference was observed between C1 and C1 (pgacA) with respect to the killing of B. mori larvae.

Animals↗
PubMedDate not supplied

Characterisation of the regulatory RNA RsmB from Pseudomonas aeruginosa PAO1.

In Pseudomonas aeruginosa, the molecular regulation of virulence factors and secondary metabolites is tightly controlled. This control involves several signal-mediated regulatory networks, including the GacS-GacA system and quorum sensing. Recently, the posttranscriptional repressor protein RsmA has been implicated in secondary metabolite production. RsmA is postulated to work in tandem with an as yet unidentified regulatory RNA molecule in a manner analogous to its homologues in other bacteria. Here we have identified a gene encoding an untranslated regulatory RNA (RsmB), located in the rpoS/ fdxA intergenic region of the P. aeruginosa PAO1 genome. Overexpression of rsmB in P. aeruginosa resulted in an increase in N-acyl-homoserine lactone, pyocyanin and elastase production compared with a marked decrease when rsmA was overexpressed. Mutation of rsmB resulted in a decrease in AHL production compared to wild type. We propose that RsmB is the cognate regulatory RNA of RsmA in P. aeruginosa. The global regulator GacA was not absolutely required for rsmB transcription in P. aeruginosa, as is the case in Pseudomonas fluorescens. However, GacA influenced the kinetics of rsmB transcription in that in late stationary phase the gacA mutant showed a substantial reduction in rsmB transcript levels compared to wild type. RsmA also influenced rsmB; in an rsmA mutant, the steady state level of rsmB transcript was reduced and this was due to a decrease in the transcription of rsmB. A balance in the levels of RsmA and RsmB may be an autoregulatory mechanism to ensure that RsmA is tightly controlled, as might be expected for such a potent global repressor.

4-Butyrolactone↗
PubMed2003

The alternative sigma factor RpoN regulates the quorum sensing gene rhlI in Pseudomonas aeruginosa.

The rhl quorum sensing (QS) circuit of Pseudomonas aeruginosa is known to regulate the expression of a number of virulence factors. This study investigates the regulation of rhlI, encoding the auto-inducer synthase RhlI responsible for the synthesis of N-butryl-L-homoserine lactone (BHL). A putative RpoN binding site was located upstream, in the promoter region of rhlI. Utilising a rhlI-lacZ transcriptional reporter, we demonstrate that under certain media conditions RpoN is a positive regulator of rhlI transcription. Measurements of BHL in extracted supernatant showed that the transcriptional patterns were reflected in the BHL levels, which were reduced in the rpoN mutant. Elastase and pyocyanin, known to be regulated by the rhl QS circuit, were shown to be reduced in a RpoN deficient strain. However, exogenous addition of BHL to the rpoN mutant did not restore these phenotypes suggesting that other regulatory factors apart from BHL are involved. Consistent with other rhl regulated phenotypes, we found that a rpoN mutant strain forms a biofilm that is different from that of the wild-type but similar to that displayed by a rhlI mutant.

Bacterial Proteins↗
PubMed2003

Reduced virulence of a hfq mutant of Pseudomonas aeruginosa O1.

The Sm-like protein Hfq has been implicated in the regulation of sigmaS-dependent and sigmaS-independent genes in E. coli and in the regulation of virulence factors in both, Yersinia enterocolitica and Brucella abortus. Here, we have studied the effect of Hfq on virulence and stress response of Pseudomonas aeruginosa (PAO1). We have constructed a PAO1hfq- mutant and a PAO1hfq-rpoS- double mutant to permit distinction between direct and indirect effects of Hfq. When compared to the wild-type and the rpoS- strains, the hfq knock out strain showed a reduced growth rate and was unable to utilize glucose as a sole carbon source. Elastase activity was 80% reduced in the hfq- mutant when compared to the wild-type or the rpoS- strain, whereas alginate production seemed to be solely affected by sigmaS. The production of catalase and pyocyanin was shown to be affected in an additive manner by both, Hfq and sigmaS. Moreover, twitching and swarming mediated by typeIV pili was shown to be impaired in the hfq- mutant. When compared to PAO1 wild-type and the rpoS- mutant, the hfq- mutant decreased virulence in Galleria mellonella by a factor of 1 x 10(4) and 5 x 10(3), respectively. Likewise, when compared to wild-type, the PAO1hfq- mutant was significantly attenuated in virulence when administered intraperitoneally in mice. These results strongly suggest that Hfq is a global regulator of PAO1 virulence and stress response which is not exclusively due to its role in stimulating the synthesis of sigmaS.

Alginates↗
PubMed2003

The Pseudomonas aeruginosa quinolone signal molecule overcomes the cell density-dependency of the quorum sensing hierarchy, regulates rhl-dependent genes at the onset of stationary phase and can be produced in the absence of LasR.

In Pseudomonas aeruginosa, diverse exoproduct virulence determinants are regulated via N-acylhomoserine lactone-dependent quorum sensing. Here we show that 2-heptyl-3-hydroxy-4(1H)-quinolone (PQS) is also an integral component of the quorum sensing circuitry and is required for the production of rhl-dependent exoproducts at the onset of stationary phase. Analysis of spent P. aeruginosa culture supernatants revealed that PQS is produced at the end of exponential phase in the parent strain and in the late stationary phase of a lasR mutant. Mutants defective in both PQS production (pqsR-) and response (pqsE-) produced substantially reduced levels of exoproducts but retained wild-type N-butanoyl homoserine lactone (C4-HSL) levels. In the wild type, provision of exogenous PQS at the time of inoculation significantly increased PA-IL lectin, pyocyanin and elastase production during early stationary phase and promoted biofilm formation. Exogenous PQS but not PQS derivatives lacking the 3-hydroxy group overcame the cell density but not growth phase-dependent production of exoproducts. PQS also overcame the transcriptional and post-transcriptional repression of lecA (which codes for the PA-IL lectin) mediated via the negative regulators MvaT and RsmA respectively. Increased expression of lecA in the presence of exogenous PQS can be explained partially by increases in RhlR, RpoS and C4-HSL levels. A refined model for quorum sensing in P. aeruginosa is presented.

4-Butyrolactone↗
PubMed1993

Inhibition of Pseudomonas aeruginosa virulence factors by subinhibitory concentrations of azithromycin and other macrolide antibiotics.

The ability of three macrolide antibiotics (erythromycin, clarithromycin and azithromycin) to inhibit the expression of several pathogenicity traits of Pseudomonas aeruginosa at concentrations that do not affect the rate of growth of this microorganism was investigated. Sub-MICs of azithromycin manifested the broadest spectrum of action and strongly suppressed the synthesis of elastase, proteases, lecithinase and DNase. Clarithromycin and erythromycin were far less effective. Gelatinase was reduced almost to the same level by the three antibiotics, while haemolysins and lipase were only marginally affected. Loss of motility was a strain and drug-dependent event, but all the macrolides tested shared the ability to induce this effect. However, only azithromycin totally suppressed synthesis of pyocyanin in all isolates. These results indicate that newer macrolides and especially axithromycin are endowed with a remarkable ability to inhibit in vitro the expression of a number of physiological processes that are considered more essential than replication in the pathogenesis of P. aeruginosa. Since erythromycin sub-MICs have already been shown to exert beneficial effects in clinical practice, our data, pointing to a much higher potency of azithromycin, suggest its use in future studies.

Anti-Bacterial Agents↗