We previously demonstrated that brief nonkilling neutrophil exposure diminishes the binding affinity of S. aureus penicillin-binding protein (PBP) 2. We sought to investigate further the role of the neutrophil in the alteration of antimicrobial activity and its interaction with PBP-2 by studying the activity of cefotaxime, which highly binds to PBP 2, and cephalexin, which minimally binds to PBP 2. Using S. aureus, cultured in vitro in sterile-filtered normal and neutrophil depleted abscess fluid, we sought to demonstrate an in vivo significance of the neutrophil effect upon the activity of antimicrobials that target PBP-2 by studying the same antimicrobials in an experimental S. aureus abscess. Rats were implanted with perforated tissue cages and infected with S. aureus; some rats were neutrophil depleted by mechlorethamine. Abscess fluids from normal and neutropenic abscesses were harvested, pooled, sterile-filtered and stored for the time-kill studies. Treatment studies were performed by administering either 300 μg/kg/d cefotaxime or cephalexin for 7 days in other rats with 24 hour-old tissue-cage S. aureus abscesses. In time-kill studies, cefotaxime was highly active against stationary phase S. aureus in MHB and in neutropenic abscess fluid, but less active in the non-neutropenic abscess fluid (p < 0.05 compared to neutropenic abscess fluid). Cephalexin was equally active in neutropenic and non-noneutropenic abscess fluids, and more active than cefotaxime in the abscess model after 7 days of therapy (2.1 ± 1.7 log10 kill, p = 0.029 vs. 0.81 ± 2.5, p = NS). These data suggest that neutrophil exposure, which diminishes S. aureus PBP-2 binding affinity [or total quantity], also adversely affects the antimicrobial activity of cefotaxime, which binds to PBP-2, as compared to cephalexin. Altered PBP targets from neutrophil exposure may be a mechanism of antimicrobial resistance within abscesses.
D. M. Bamberger. “Outcome of Medical Treatment of Bacterial Abscesses without Therapeutic Drainage: Review of Cases Reported in the Literature,” Clinical Infectious Disease, Vol. 23, No. 3, 1996, pp. 592-603.
D. M. Bamberger, B. L. Herndon, M. Dew, R. P. Chern, H. Mitchell, L. E. Summers, R. F. Marcus, S. C. Kim and P. R. Suvarna, “Efficacies of Ofloxacin, Rifampin, and Clindamycin in Treatment of S. aureus Abdominal Abscesses and Correlation with Results of an in Vitro Assay of Intracellular Bacterial Killing,” Antimicrobial Agents & Chemotherapy, Vol. 41, No. 5, 1997, pp. 1178-1181.
D. M. Bamberger and B. L. Herndon, “Bactericidal Capacity of Neutrophils in Rabbits with Experimental Acute and Chronic Abscesses,” Journal of Infectious Disease, Vol. 162, No. 1, 1990, pp. 186-192. doi:10.1093/infdis/162.1.186
D. M. Bamberger, B. L. Herndon, J. Fitch, A. Florkowski and V. Parkhurst, “The Effect of Neutrophils on Cefazolin Activity and Penicillin Binding Proteins in Staphylococcus aureus Abscesses,” Antimicrobial Agents & Chemotherapy, Vol. 46, No. 9, 2002, pp. 2878-2884.
H. D. Gresham, J. H. Lowrance, T. E. Caver, B. S. Wilson, A. L. Cheung and F. P. Lindberg, “Survival of Staphylococcus aureus inside Neutrophils Contributes to Infection,” Journal of Immunology, Vol. 164, No. 7, 2000, pp. 3713-3722.
J. M. Voyich, K. R. Braughton, D. E. Studevant, A. R. Whiney, B. Said-Salim, S. F. Porcella, et al., “Insights into Mechanisms Used by Staphylococcus aureus to Avoid Destruction by Human Neutrophils,” Journal of Immunology, Vol. 175, No. 6, 2005, pp. 3907-3919.
S. Turk, O. Verlaine, T. Gerards, M. Zivec, J. Humljan, I. Sosic, A. Amoroso, A. Zervosen, A. Luxen, B. Joris and S. Gobec, “New Noncovalent Inhibitors of Penicilin-Binding Proteins from Penicillin-Resistant Bacteria,” PLoS ONE, Vol. 6, No. 5, 2011, Article ID: e19418.
S. Bobba and W. G. Gutheil, “Multivariate Geometrical Analysis of Ctralytic Residues in the Penicillin-Binding Proteins,” The International Journal of Biochemistry & Cell Biology, Vol. 43, No. 10, 2011, pp. 1490-1499.
N. H. Georgopapadakou, S. A. Smith, and D. P. Bonner, “Penicillin-Binding Proteins in a Staphylococcus aureus Strain Resistant to Specific β-Lactam Antibiotics,” Antimicrobial Agents & Chemotherapy, Vol. 22, No. 1, 1982, pp. 172-175.
P. C. Taylor, F. D. Schoenknecht, J. C. Sherris and E. C. Linner, “Determination of Minimum Bactericidal Concentrations of Oxacillin for Staphylococcus aureus: Influence and Significance of Technical Factors,” Antimicrobial Agents & Chemotherapy, Vol. 23, No. 1, 1983, pp. 142-150.
National Committee for Clinical Laboratory Standards, “Performance Standards for Antimicrobial Disk Susceptibility Tests: Approved Standard—11th Edition,” Vol. 32, No. 1, Clinical and Laboratory Standards Institute, Wayne, USA, 2012.
A. Koomer, T. Quinn, D. Bamberger and B. L. Herndon, “Neutrophil-Antimicrobial Interaction in the Established Infection: Effect on Staphylococcus aureus,” Journal of Infection, Vol. 52, No. 5, 2006, pp. 288-320.
A. Tomasz, H. B. Drugeon, H. M. de Lencastre, D. Jabes, L. McDougall and J. Bille, “New Mechanism for Methicillin Resistance in Staphylococcus aureus: Clinical Isolates That Lack the PBP 2a Gene and Contain Normal Penicillin-Binding Proteins with Modified PenicillinBinding Capacity,” Antimicrobial Agents & Chemotherapy, Vol. 33, No. 11, 1989, pp. 1869-1874.
D. L. Stevens, S. Yan and A. E. Bryant, “PenicillinBinding Protein Expression at Different Growth Stages Determines Penicillin Efficacy in Vitro and in Vivo: An Explanation for the Inoculum Effect,” Journal of Infectious Diseases, Vol. 167, No. 6, 1993, pp. 1401-1405.