Clinical Isolates of Staphylococcus aureus Show Variation in β-Lactamase Production and Are More Susceptible to Antibiotics Conjugated with β-Lactamase Inhibitors
β-Lactam antibiotics are a
cornerstone in the treatment of bacterial infections on account of its high
therapeutic index and selective toxicity—they act by inhibiting the
biosynthesis of peptidoglycan, a key
component in bacterial cell wall. Ninety (90) clinical specimens obtained from
the microbiology unit Specialist Hospital Bauchi were screened for S.aureus, positive isolates were
examined for β-Lactamase expression by using two Penicillin G
concentrations (5000 IU/ml and 25,000 IU/ml) in acidometric agar technique with phenol red as indicator, and the susceptibility pattern
of the isolates to β-Lactam
antibiotics was also determined. S.aureus prevalence of 31% (28/90)
was obtained, of
which 96% (27/28) of strains were β-Lactamase
positive in the standard test, while 63% (17/27) were able to hydrolyze
penicillin G concentration of 25,000IU/ml
(5X the concentration in the standard test), and a strain was found to be β-Lactamase negative. The resistance to five β-Lactams, ampicillin, cephalexin,
amoxicillin, cloxacillin and flucloxaillin, were 100%, 96%, 89
References
[1]
Kayser, F.H., Bienz, K.A., Eckert, J. and Zinkernagel, R.M. (2005) Medical Microbiology. Thieme, Stuttggart, 198, 202.
[2]
Wieldemann, B. (1986) Gene Alterations Leading to Resistance to β-Lactam Antibitotics. In: Levy, S. and Novick, R.P., Eds., Antibiotic Resistance Genes: Ecology, Transfer and Expression, Banbury Report, 24th Edition, Cold Spring Laboratory, Colorado, 347.
[3]
Massidda, O., Mingoia, M., Fadda, D., Whalen, M.B., Pia, M.M. and Varaldo, P.E. (2006) Analysis of the β-Lactamase Plasmid of Borderline Methicillin Susceptible Staphylococcus aureus: Focus on bla Complex and Cadmium Resistance Determinants cadD and cadX. Plasmid, 55, 114-127. http://dx.doi.org/10.1016/j.plasmid.2005.08.001
[4]
Brooks, G.F., Butel, J.S. and Morse, S.A. (2004) Medical Microbiology. 23rd Edition, McGraw Hill, Boston.
[5]
Kloos, W.E., Schlafer, F.H. and Gotz, F. (1992) The Genes Staphylococcus. In: Balows, A., Truper, H.G., Dwarkin, M., Harder, W. and Scheilfer, K.H., Eds., The Prokaryotes, 2nd Edition, Vol. 2, Springer-Verlag, New York, 1369-1420.
[6]
Ayello, G., Bupp, C., Elliot, J., Facklam, R., Knapp, J.S., Popovic, T., Wells, J. and Dowell, S.F., Eds. (2003) Manual for the Laboratory Identification and Antimicrobial Susceptibility Testing of Bacterial Pathogens of Public Health Importance in the Developing World. CDC/WHO, 175
[7]
Bauer, A.W., Knieger, W.F. and Simon, J.H. (1966) Antibiotic Susceptibility Testing by a Standard Single-Disk Method. American Journal of Clinical Pathology, 45, 493-494.
[8]
Witte, W. and Hummel, R. (1986) Antibiotic Resistance in Staphylococcus aureus Isolated from Man and Animals. In: Levy, S. and Novick, R.P., Eds., Antibiotic Resistance Genes: Ecology, Transfer and Expression, Banbury Report, 24th Edition, Cold Spring Laboratory, Colorado, 95-105.
[9]
Dyke, K.G.H. (1979) β-Lactamase of Staphylococcus aureus. In: Hamilton-Miller, J.M.T. and Smith, J.T., Eds., Beta-Lactamase, Academic Press, Inc., New York, 291-310.
[10]
McDougal, L.K. and Thornsberry, C. (1986) The Role of β-Lactamase in Staphylococcus Resistance to Penicillinase-Resistant Penicillins and Cephalosporins. Journal of Clinical Microbiology, 23, 832-839.
[11]
Basker, M.J., Edmondson, H.A. and Sutherland, H. (1980) Comparative Stabilities of Penicillins and Cephalosporins to Staphylococcal β-Lactamase and Activities against Staphylococcus aureus. Journal of Antimicrobial Chemotherapy, 6, 333-341. http://dx.doi.org/10.1093/jac/6.3.333
[12]
Lacey, R.W. and Stokes, A. (1977) Susceptibility of the “Penicillinase-Resistant’’ Penicillins and Cephalosporins to Penicillinase of Staphylococcus aureus. Journal of Clinical Pathology, 30, 35-39. http://dx.doi.org/10.1136/jcp.30.1.35
