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Cellular uptake and cell-associated activity of third generation cephalosporins
Abstract:
The ability of the third generation cephalosporins to penetrate human polymorphonuclear leukocytes (PMNs) and their antibacterial activity against cell-associated Staphylococcus aureus (SA) and Haemophilus influenzae, type b (Hib) were studied. Utilizing radioactive uptake experiments, the cellular to extracellular concentration ratios were determined to be less than one for all cephalosporins at 10 and 120 min: cefotaxime (0.08 +/- 0.02, 0.34 +/- 0.08), ceftizoxime (0.21 +/- 0.11, 0.52 +/- 0.18), ceftriaxone (0.12 +/- 0.04, 0.38 +/- 0.23), and N-formimidoyl thienamycin (0.18 +/- 0.09, 0.33 +/- 0.14). Third generation cephalosporins were similar to penicillin in their exclusion from PMNs. The killing of cell-associated SA and Hib were evaluated in a preopsonized cell-associated bacterial assay with radiolabelled SA/Hib (cfu/cpm) comparing activity of PMNs + antibiotics to the PMN cell control (no antibiotics) at 0.5, 2, and 4 h. PMNs alone killed less than or equal to 0.5 log SA/Hib over 4 h. Clindamycin killed significantly more SA (p less than 0.01) than all other antibiotics; nafcillin killed significantly fewer SA (p less than 0.05) than all other antibiotics. Although each third generation cephalosporin showed good activity against cell-associated Hib, chloramphenicol had a significantly greater effect (p less than 0.05). N-formimidoyl thienamycin demonstrated good activity only after the concentration was increased in vitro to 8 micrograms/ml. Although cellular penetration of antibiotics may be important in the eradication of cell-associated pathogens, the overall cellular activity would appear to be multifactorial.
Insights
Third-generation cephalosporins showed limited penetration into human polymorphonuclear leukocytes (PMNs), similar to penicillin. Antibiotic effectiveness against cell-associated Staphylococcus aureus and Haemophilus influenzae was multifactorial, not solely dependent on PMN penetration.
Area of Science:
- Pharmacology
- Microbiology
- Immunology
Background:
- Human polymorphonuclear leukocytes (PMNs) are crucial in combating bacterial infections.
- Understanding antibiotic penetration into PMNs is vital for treating intracellular pathogens.
- Third-generation cephalosporins are commonly used antibiotics with varying cellular activities.
Purpose of the Study:
- To assess the penetration of third-generation cephalosporins into human PMNs.
- To evaluate the antibacterial activity of these cephalosporins against cell-associated Staphylococcus aureus (SA) and Haemophilus influenzae type b (Hib).
Main Methods:
- Radioactive uptake experiments were used to determine cellular to extracellular concentration ratios of cephalosporins in PMNs.
- A preopsonized cell-associated bacterial assay with radiolabeled bacteria was employed to assess killing activity.
- Antibiotic efficacy was compared between PMNs with antibiotics and PMN cell controls without antibiotics over time.
Main Results:
- All studied third-generation cephalosporins exhibited low penetration into PMNs, with concentration ratios less than one.
- Third-generation cephalosporins showed similar PMN exclusion patterns to penicillin.
- Clindamycin demonstrated superior killing of SA, while nafcillin showed significantly less activity.
- Chloramphenicol was more effective against cell-associated Hib than third-generation cephalosporins.
- N-formimidoyl thienamycin required higher in vitro concentrations for good activity.
Conclusions:
- Third-generation cephalosporins have poor penetration into human PMNs.
- Antibacterial activity against cell-associated pathogens is influenced by multiple factors beyond cellular penetration.
- Further research is needed to optimize antibiotic strategies for intracellular bacterial infections.