1
|
Van den Bossche S, De Broe E, Coenye T, Van Braeckel E, Crabbé A. The cystic fibrosis lung microenvironment alters antibiotic activity: causes and effects. Eur Respir Rev 2021; 30:30/161/210055. [PMID: 34526313 DOI: 10.1183/16000617.0055-2021] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 04/23/2021] [Indexed: 01/08/2023] Open
Abstract
Chronic airway colonisation by Pseudomonas aeruginosa, a hallmark of cystic fibrosis (CF) lung disease, is associated with increased morbidity and mortality and despite aggressive antibiotic treatment, P. aeruginosa is able to persist in CF airways. In vitro antibiotic susceptibility assays are poor predictors of antibiotic efficacy to treat respiratory tract infections in the CF patient population and the selection of the antibiotic(s) is often made on an empirical base. In the current review, we discuss the factors that are responsible for the discrepancies between antibiotic activity in vitro and clinical efficacy in vivo We describe how the CF lung microenvironment, shaped by host factors (such as iron, mucus, immune mediators and oxygen availability) and the microbiota, influences antibiotic activity and varies widely between patients. A better understanding of the CF microenvironment and population diversity may thus help improve in vitro antibiotic susceptibility testing and clinical decision making, in turn increasing the success rate of antibiotic treatment.
Collapse
Affiliation(s)
| | - Emma De Broe
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Tom Coenye
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| | - Eva Van Braeckel
- Dept of Respiratory Medicine, Cystic Fibrosis Reference Centre, Ghent University Hospital, Ghent, Belgium.,Dept of Internal Medicine and Paediatrics, Ghent University, Ghent, Belgium
| | - Aurélie Crabbé
- Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium
| |
Collapse
|
2
|
McCurtain JL, Gilbertsen AJ, Evert C, Williams BJ, Hunter RC. Agmatine accumulation by Pseudomonas aeruginosa clinical isolates confers antibiotic tolerance and dampens host inflammation. J Med Microbiol 2019; 68:446-455. [PMID: 30688634 PMCID: PMC7423162 DOI: 10.1099/jmm.0.000928] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 12/29/2018] [Indexed: 12/17/2022] Open
Abstract
PURPOSE In the cystic fibrosis (CF) airways, Pseudomonas aeruginosa undergoes diverse physiological changes in response to inflammation, antibiotic pressure, oxidative stress and a dynamic bioavailable nutrient pool. These include loss-of-function mutations that result in reduced virulence, altered metabolism and other phenotypes that are thought to confer a selective advantage for long-term persistence. Recently, clinical isolates of P. aeruginosa that hyperproduce agmatine (decarboxylated arginine) were cultured from individuals with CF. Sputum concentrations of this metabolite were also shown to correlate with disease severity. This raised the question of whether agmatine accumulation might also confer a selective advantage for P. aeruginosa during chronic colonization of the lung. METHODOLOGY AND RESULTS We screened a library of P. aeruginosa CF clinical isolates and found that ~5 % of subjects harboured isolates with an agmatine hyperproducing phenotype. Agmatine accumulation was a direct result of mutations in aguA, encoding the arginine deiminase that catalyses the conversion of agmatine into various polyamines. We also found that agmatine hyperproducing isolates (aguA-) had increased tolerance to the cationic antibiotics gentamicin, tobramycin and colistin relative to their chromosomally complemented strains (aguA+). Finally, we revealed that agmatine diminishes IL-8 production by airway epithelial cells in response to bacterial infection, with a consequent decrease in neutrophil recruitment to the murine airways in an acute pneumonia model. CONCLUSION These data highlight a potential new role for bacterial-derived agmatine that may have important consequences for the long-term persistence of P. aeruginosa in the CF airways.
Collapse
Affiliation(s)
- Jennifer L. McCurtain
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN 55455, USA
- Present address: Merck Research Laboratories, Rahway, NJ 07065, USA
| | - Adam J. Gilbertsen
- Pulmonary, Allergy, Critical Care and Sleep Division, University of Minnesota, Minneapolis, MN 55455, USA
| | - Clayton Evert
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Bryan J. Williams
- Pulmonary, Allergy, Critical Care and Sleep Division, University of Minnesota, Minneapolis, MN 55455, USA
- Present address: HealthEast, St. Joseph’s Hospital, Saint Paul, MN 55102, USA
| | - Ryan C. Hunter
- Department of Microbiology & Immunology, University of Minnesota, Minneapolis, MN 55455, USA
| |
Collapse
|
3
|
Bos AC, Passé KM, Mouton JW, Janssens HM, Tiddens HAWM. The fate of inhaled antibiotics after deposition in cystic fibrosis: How to get drug to the bug? J Cyst Fibros 2016; 16:13-23. [PMID: 28254026 DOI: 10.1016/j.jcf.2016.10.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 09/26/2016] [Accepted: 10/01/2016] [Indexed: 10/20/2022]
Abstract
BACKGROUND Chronic airway infections in patients with cystic fibrosis (CF) are most often treated with inhaled antibiotics of which deposition patterns have been extensively studied. However, the journey of aerosol particles does not end after deposition within the bronchial tree. OBJECTIVES To review how local conditions affect the clinical efficacy of antibiotic aerosol particles after deposition in the airways of patients with CF. METHODS Electronic databases were searched from inception to September 2015. Original studies describing the effect of CF sputum or bacterial factors on antibiotic efficacy and formulations to increase efficacy were included. RESULTS 35 articles were included which mostly described in vitro studies and mainly investigated aminoglycosides. After deposition, diffusion through the mucus layer was reduced for aminoglycosides, β-lactam antibiotics and fluoroquinolones. Within CF mucus, low oxygen tension adversely affected aminoglycosides, β-lactam antibiotics, and chloramphenicol; and molecules inactivated aminoglycosides but not β-lactam antibiotics. Finally, the alginate layer surrounding Pseudomonas aeruginosa was an important factor in the resistance against all antibiotics. CONCLUSIONS After deposition in the airways, the local efficacy of inhaled antibiotics can be reduced by molecules within CF mucus and the alginate layer surrounding P. aeruginosa.
Collapse
Affiliation(s)
- Aukje C Bos
- Department of Paediatric Pulmonology and Allergology, Erasmus Medical Centre (MC) - Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.
| | - Kimberly M Passé
- Department of Paediatric Pulmonology and Allergology, Erasmus Medical Centre (MC) - Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.
| | - Johan W Mouton
- Department of Medical Microbiology and Infectious Diseases, Erasmus MC, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.
| | - Hettie M Janssens
- Department of Paediatric Pulmonology and Allergology, Erasmus Medical Centre (MC) - Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.
| | - Harm A W M Tiddens
- Department of Paediatric Pulmonology and Allergology, Erasmus Medical Centre (MC) - Sophia Children's Hospital, Wytemaweg 80, 3015 CN Rotterdam, The Netherlands.
| |
Collapse
|
4
|
Cao B, Christophersen L, Kolpen M, Jensen PØ, Sneppen K, Høiby N, Moser C, Sams T. Diffusion Retardation by Binding of Tobramycin in an Alginate Biofilm Model. PLoS One 2016; 11:e0153616. [PMID: 27100887 PMCID: PMC4839563 DOI: 10.1371/journal.pone.0153616] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 03/31/2016] [Indexed: 12/25/2022] Open
Abstract
Microbial cells embedded in a self-produced extracellular biofilm matrix cause chronic infections, e. g. by Pseudomonas aeruginosa in the lungs of cystic fibrosis patients. The antibiotic killing of bacteria in biofilms is generally known to be reduced by 100–1000 times relative to planktonic bacteria. This makes such infections difficult to treat. We have therefore proposed that biofilms can be regarded as an independent compartment with distinct pharmacokinetics. To elucidate this pharmacokinetics we have measured the penetration of the tobramycin into seaweed alginate beads which serve as a model of the extracellular polysaccharide matrix in P. aeruginosa biofilm. We find that, rather than a normal first order saturation curve, the concentration of tobramycin in the alginate beads follows a power-law as a function of the external concentration. Further, the tobramycin is observed to be uniformly distributed throughout the volume of the alginate bead. The power-law appears to be a consequence of binding to a multitude of different binding sites. In a diffusion model these results are shown to produce pronounced retardation of the penetration of tobramycin into the biofilm. This filtering of the free tobramycin concentration inside biofilm beads is expected to aid in augmenting the survival probability of bacteria residing in the biofilm.
Collapse
Affiliation(s)
- Bao Cao
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, DK-2100 Copenhagen, Denmark
| | - Lars Christophersen
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, DK-2100 Copenhagen, Denmark
| | - Mette Kolpen
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, DK-2100 Copenhagen, Denmark
- Department of Immunology and Microbiology, UC-CARE, Faculty of Health Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Peter Østrup Jensen
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, DK-2100 Copenhagen, Denmark
| | - Kim Sneppen
- Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen, Denmark
| | - Niels Høiby
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, DK-2100 Copenhagen, Denmark
- Department of Immunology and Microbiology, UC-CARE, Faculty of Health Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
| | - Claus Moser
- Department of Clinical Microbiology, Copenhagen University Hospital, Rigshospitalet, DK-2100 Copenhagen, Denmark
| | - Thomas Sams
- Biomedical Engineering, Dept. of Electrical Engineering, Technical University of Denmark, DK-2800 Lyngby, Denmark
- * E-mail:
| |
Collapse
|
5
|
Differential protection from tobramycin by extracellular polymeric substances from Acinetobacter baumannii and Staphylococcus aureus biofilms. Antimicrob Agents Chemother 2014; 58:4755-61. [PMID: 24913166 DOI: 10.1128/aac.03071-14] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We investigated biofilms of two pathogens, Acinetobacter baumannii and Staphylococcus aureus, to characterize mechanisms by which the extracellular polymeric substance (EPS) found in biofilms can protect bacteria against tobramycin exposure. To do so, it is critical to study EPS-antibiotic interactions in a homogeneous environment without mass transfer limitations. Consequently, we developed a method to grow biofilms, harvest EPS, and then augment planktonic cultures with isolated EPS and tobramycin. We demonstrated that planktonic cultures respond differently to being treated with different types of EPS (A. baumannii versus S. aureus) in the presence of tobramycin. By harvesting EPS from the biofilms, we found that A. baumannii EPS acts as a "universal protector" by inhibiting tobramycin activity against bacterial cells regardless of species; S. aureus EPS did not show any protective ability in cell cultures. Adding Mg(2+) or Ca(2+) reduced the protective effect of A. baumannii EPS. Finally, when we selectively digested the proteins or DNA of the EPS, we found that the protective ability did not change, suggesting that neither has a significant role in protection. To the best of our knowledge, this is the first study that demonstrates how EPS protects pathogens against antibiotics in a homogeneous system without mass transfer limitations. Our results suggest that EPS protects biofilm communities, in part, by adsorbing antibiotics near the surface. This may limit antibiotic diffusion to the bottom of the biofilms but is not likely to be the only mechanism of protection.
Collapse
|
6
|
Agarwal G, Kapil A, Kabra SK, Das BK, Dwivedi SN. Characterization of Pseudomonas aeruginosa isolated from chronically infected children with cystic fibrosis in India. BMC Microbiol 2005; 5:43. [PMID: 16033658 PMCID: PMC1183212 DOI: 10.1186/1471-2180-5-43] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2005] [Accepted: 07/21/2005] [Indexed: 10/28/2022] Open
Abstract
BACKGROUND Pseudomonas aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis (CF). With chronicity of infection, the organism resides as a biofilm, shows multi-drug resistance, diversifies its colony morphology and becomes auxotrophic. The patients have been found to be colonized with multiple genotypes. The present work was carried out to characterize P. aeruginosa isolated from children with cystic fibrosis using phenotypic and genotypic methods. RESULTS We studied 56 patients with CF attending the Pediatric Chest clinic at All India Institute of Medical Sciences, New Delhi, India during August 1998-August 2001. These patients were regularly followed up at the clinic. Out of 56 patients, 27 were culture positive for P. aeruginosa where 8 were chronically infected (Group1) and 19 were intermittently colonized with the organism (Group2). Patients under Group1 had significantly higher rates of hospitalization, death and colonization with different colony morphotypes (p < 0.05). The isolates from Group1 patients were the positive producers of extended spectrum beta lactamase. A total of 5 auxotrophs were recovered from 2 patients where one was chronically infected with P. aeruginosa and the other was a recently enrolled patient. The auxotrophs had the specific requirement for methionine and arginine. Molecular typing revealed 33 ERIC-PCR (E1-E33) and 5 PCR-ribotyping (P1-P5) patterns. By ERIC-PCR, 4 patients were colonized with 2-4 genotypes and the remaining 23 patients were colonized with the single genotype. CONCLUSION With chronicity of infection, P. aeruginosa becomes multidrug resistant, diversifies its colony morphology, acquires mucoidity and shows auxotrophy for amino acids. The chronically infected patients can be colonized with multiple genotypes. Thus in a particular clinical set up, high index of suspicion should be there for diagnosis of CF patients so as to prevent the delay in diagnosis and management of CF patients.
Collapse
Affiliation(s)
- Gunjan Agarwal
- Department of Microbiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, INDIA
| | - Arti Kapil
- Department of Microbiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, INDIA
| | - Susheel Kumar Kabra
- Department of Pediatrics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, INDIA
| | - Bimal Kumar Das
- Department of Microbiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, INDIA
| | - Sada Nand Dwivedi
- Department of Biostatistics, All India Institute of Medical Sciences, Ansari Nagar, New Delhi-110029, INDIA
| |
Collapse
|
7
|
Allison DG, Gilbert P. Modification by surface association of antimicrobial susceptibility of bacterial populations. JOURNAL OF INDUSTRIAL MICROBIOLOGY 1995; 15:311-7. [PMID: 8605070 DOI: 10.1007/bf01569985] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In the majority of natural situations in which bacteria are found, they are associated with and attached to surfaces. In the presence of moisture and nutrients, they grow to form extensive bacterial films which are often enveloped within copius exopolymeric matrices. Biofilms are ubiquitous to many different situations in industry, the environment and medicine. Their presence can be either beneficial or more commonly detrimental to such systems. In this respect, biofilm populations possess physiological properties distinct from those of unattached, planktonic bacteria. Moreover, it is generally accepted that bacteria growing within a biofilm are more resistant to antimicrobial agents than their planktonic counterparts. However, although the consequences of attachment to antimicrobial resistance have been known for many years, the mechanistic bases for such effects have still to be fully elucidated. In this article the nature of different resistance mechanisms, including those of the exopolymeric matrix, environmental modulation, attachment-specific physiologies and quorum sensing are reviewed.
Collapse
Affiliation(s)
- D G Allison
- Department of Pharmacy, University of Manchester, UK
| | | |
Collapse
|
8
|
Kumon H, Tomochika K, Matunaga T, Ogawa M, Ohmori H. A sandwich cup method for the penetration assay of antimicrobial agents through Pseudomonas exopolysaccharides. Microbiol Immunol 1994; 38:615-9. [PMID: 7799834 DOI: 10.1111/j.1348-0421.1994.tb01831.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We developed new sandwich cup method to assay the penetration of various antimicrobial agents through Pseudomonas exopolysaccharides. Using alginate extracted from mucoid-type Pseudomonas aeruginosa and gellan gum from Pseudomonas elodea, the role of exopolysaccharides as a barrier against drug penetration was examined. The penetration of positively charged hydrophilic drugs such as aminoglycosides and polypeptides was markedly inhibited by the gels tested, but that of beta-lactams, quinolones, and macrolides was not inhibited. The penetration of gentamicin was strongly influenced by the gel concentration, the solution to be used, and the presence of Ca2+. These results suggest that the microenvironment at the infection site could greatly influence drug penetration through biofilms in vivo.
Collapse
Affiliation(s)
- H Kumon
- Department of Urology, Okayama University Medical School, Japan
| | | | | | | | | |
Collapse
|
9
|
|
10
|
Hoyle BD, Alcantara J, Costerton JW. Pseudomonas aeruginosa biofilm as a diffusion barrier to piperacillin. Antimicrob Agents Chemother 1992; 36:2054-6. [PMID: 1416900 PMCID: PMC192438 DOI: 10.1128/aac.36.9.2054] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Pseudomonas aeruginosa 579 biofilms formed on dialysis membranes retarded piperacillin diffusion. Treatment of biofilms with 5.0 mM CaCl2.2H2O prevented diffusion. Biofilms permitted equilibration of [14C]glucose. Thin-layer chromatography of fluids distal to untreated (viable and nonviable) and viable Ca(2+)-treated P. aeruginosa 579 biofilms and fluids distal to a viable P. aeruginosa mutant noninducible for the expression of beta-lactamase did not detect piperacillinoic acid.
Collapse
Affiliation(s)
- B D Hoyle
- Department of Biological Sciences, University of Calgary, Alberta, Canada
| | | | | |
Collapse
|
11
|
Savoia D, Malcangi A, Martinetto P. The effect of subinhibitory concentrations of some antibiotics on the hydrophobicity of gram-negative bacteria. J Chemother 1990; 2:20-5. [PMID: 2332780 DOI: 10.1080/1120009x.1990.11738975] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cell surface hydrophobicity is currently regarded as an important factor in promoting bacterial adherence to a wide variety of surfaces. This feature was investigated in some Gram-negative bacteria isolated from urinary tract infections and the extent to which their surface characteristics were affected by subinhibitory concentrations of some antibiotics was assayed. Surface properties were evaluated using the salting-out technique (SAT) and bacterial absorption to n-hexadecane (BATH). SAT showed that all except 3 Escherichia coli strains were autoaggregating. BATH detected more hydrophobic characteristics in the stationary phase of bacterial growth. Pretreatment with antibiotics generally reduced hydrophobicity and thus affected the initial reversible phase of attachment of bacteria to eukaryotic cells.
Collapse
Affiliation(s)
- D Savoia
- Institute of Microbiology, University of Turin, Italy
| | | | | |
Collapse
|
12
|
Kelly NM, Rawling EG, Hancock RE. Determinants of the efficacy of tobramycin therapy against isogenic nonmucoid and mucoid derivatives of Pseudomonas aeruginosa PAO1 growing in peritoneal chambers in mice. Antimicrob Agents Chemother 1989; 33:1207-11. [PMID: 2508542 PMCID: PMC172626 DOI: 10.1128/aac.33.8.1207] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Mice which were supporting the growth of Pseudomonas aeruginosa in chambers implanted in their peritoneums were given two intramuscular injections of tobramycin (15 mg/kg of body weight each) at an interval of 8 h. Three hours later, chambers were removed and their contents were assessed for viable counts. Controls revealed that tobramycin levels in the chambers were 3.8 micrograms/ml 15 min after injection of 15 mg of tobramycin per kg and remained above the in vitro MICs (0.5 to 1 microgram/ml) for the tested strains for 8 h. It was demonstrated that tobramycin therapy was less effective with higher inocula and with longer delay before administration. Thus, in vivo, the concentration of bacteria in the chambers at the time of the first tobramycin injection had a profound effect on the bactericidal efficacy of tobramycin therapy. No such concentration dependence was observed in mock in vitro therapy experiments. A phage-selected mucoid derivative of P. aeruginosa PAO1 showed only a marginal increase in in vitro aminoglycoside susceptibility and no major alteration in in vivo susceptibility compared with its isogenic nonmucoid parent strain.
Collapse
Affiliation(s)
- N M Kelly
- Department of Microbiology, University of British Columbia, Vancouver, Canada
| | | | | |
Collapse
|
13
|
Nichols WW, Dorrington SM, Slack MP, Walmsley HL. Inhibition of tobramycin diffusion by binding to alginate. Antimicrob Agents Chemother 1988; 32:518-23. [PMID: 3132093 PMCID: PMC172213 DOI: 10.1128/aac.32.4.518] [Citation(s) in RCA: 181] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
[3H]tobramycin bound to sodium alginate and to exopolysaccharide prepared from two mucoid strains of Pseudomonas aeruginosa. Binding to sodium alginate was similar to binding to exopolysaccharide, both in the dependence on tobramycin concentration and in the maximum binding observed at saturation. Incorporation of sodium alginate into agar plates reduced the zone sizes of growth inhibition caused by tobramycin. The reductions in zone sizes were quantitatively accounted for by the binding of tobramycin to sodium alginate during diffusion of the antibiotic away from the well in which it had been placed at the start of the experiment. However, the binding of tobramycin to the exopolysaccharide of P. aeruginosa, and the resulting inhibition of diffusion of the antibiotic, did not significantly increase the penetration time of a spherical microcolony with a radius of 125 micron, such as might be found in the respiratory tract of a patient with cystic fibrosis (from a 90% penetration time of 12 s in the absence of exopolysaccharide to one of 35 s with an exopolysaccharide concentration of 1.0% [wt/vol]).
Collapse
Affiliation(s)
- W W Nichols
- Regional Public Health Laboratory, John Radcliffe Hospital, Oxford, United Kingdom
| | | | | | | |
Collapse
|
14
|
Lambert PA. The bacterial cell surface and antimicrobial resistance. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 1988; 32:149-74. [PMID: 2851150 DOI: 10.1007/978-3-0348-9154-7_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
|
15
|
Abstract
Pulmonary infection in cystic fibrosis (CF) is primarily a purulent tracheobronchitis. Antibiotics are available that are active in vitro against bacteria isolated from sputum from patients with CF. Despite efficacious antibiotic concentrations in serum, however, the results of treatment are frequently suboptimal. A widely accepted explanation for this limited efficacy is poor penetration of orally or intravenously administered antibiotics into respiratory secretions. The bioactivity of antibiotics in respiratory secretions is not identical to that found in vitro. Laboratory conditions are standardized and selected to approximate serum. Deviations from these conditions can markedly influence the results. Differences in composition between sputum and laboratory culture media, as well as variation in growth and metabolism of the pathogen in respiratory secretions, must be considered when predicting in vivo activity in sputum. Thus, when defining criteria for antibiotic susceptibility or resistance in the treatment of pulmonary infection in patients with CF, the concentrations achievable in bronchial secretions as well as the bioactivity in this environment should be considered.
Collapse
|