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Staphylococcal ß-Lactamases
ANTIMIC’ROBICS AND INFECTIOUS DISEASES NEWSLETTER
Editor-in-Chief Charles W. Stratton, MD Vanderbilt University School of Medicine Nashville, Tennessee Full editorial board appears on back cover
Volume 15, Number 8 August 1996
Staphylococcal O-Lactamases Charles W. Stratton, MD Associate Professor of Pathology and Medicine Vanderbilt University School of Medicine Nashville, Tennessee
Introduction Staphylococcal l3-lactamase was among the first bacterial enzymes recognized as capable of destroying penicillin. Not suprisingly, this highly potent penicillin inactivator was initially designated a “penicillinase.” Later, this enzyme, like others in its class, was designated a B-lactamase due to its hydrolytic action specifically directed against the l3-lactam ring. B-lactamases produced by strains of Staphylococcus aureus were long considered a single and unique extracellular enzyme directed primarily against penicillins. Immunological variants of staphylococcal l3-lactamase were described, but were thought to be conformational changes caused by refolding of a single enzyme. Fifty years later, each of these early concepts has required modifications. First, and most importantly, Kernodle and colleagues have clearly demonstrated that there are at least four different enzymatic variants of staphylococcal B-lactamase. Some l3-lactamases produced by S. aureus isolates readily hydrolyze cephalosporins as well as penicillins. Moreover, the location of staphlococcal R-lactamases is more accurately described as pericellular than as extracellular. These concepts and other important aspects of staphylococcal8 lactamase are discussed in this review.
AIDIEX
15(8)51-58,1996
Genetic Aspects of Staphylococcal B-Lactamases The B-lactamase production of S. aureus is typically inducible and usually associated with transducible plasmids or with transposons. The nucleotide sequencing of l3-lactamase genes found on either plasmids or transposons appears identical suggesting a common origin of this gene. Of interest is that this gene seems to have been passed to the Enterococcus species. There are three regulatory genes (blal, blaR1, and blaR2) that are recognized as influencing the expression of the l3-lactamasegene (blaZ) of S. aureus. The fist, blal, produces a diffusible repressor protein, bla1, which can bind to the operator site of the l3-lactamase structural gene and prevent its transcription by RNA polymerase. The exact role of the other two genes, bluRI and blaR2, is less clear, but both appear to produce interactive proteins which mediate the induction of the B-lactamase gene. One possibility is that blaR1 protein from the cytoplasmic membrane interacts with the blaI/bZaZ complex in the cytoplasm resulting in the binding of the repressor protein blaI to blaR1 which frees the operator site of blaZ so that transcription can occur. The interactive protein, blaR2, may, in turn, antagonize the gene, bluRI. Evidence for this can be found in mutational studies where the loss of blaR1 function results in noninducible basal-level expression of R-lactamase while the loss of blaR2 function confers highlevel constitutive expression. In
Elsevier
addittion to regulating B-lactamase, these genes also appear to regulate the expression of the altered penicillinbinding protein (PBP-2a) found in methicillin-resistant S. aureus.
Enzymatic Activity of Staphylococcal ii-Lactamases Initial kinetic studies of staphylococcal B-lactamase were done for the most part with impure enzyme, making the exact interpretation of results difficult. However, these studies as well as preliminary analysis of the amino acid compositions from immunologically distinct strains suggested that only one enzyme was produced by all B-lactamase producing strains of S. aureus. Yet, Richmond in 1965 found that antiserum prepared against purified type A enzyme stimulated the activity of the A-type enzyme almost 4-fold whereas B-type enzyme was only slightly stimulated; C-type was not stimulated at all.
In This Issue Staphylococcal D-Lactamases. . . . .51 Charles W. Stratton, MD
Peritonitis in a Patient Undergoing Peritoneal Dialysis Caused by Mycobacterium abscessus . . . . . . . . 54 A case report
Endocarditis on a Native Aortic Valve Caused by Actinobacillus actinomycetemcomitans . . . . . . . . . .55 A case report
0196-417X/96/$0.00+
15.00
Although the antiserum was able to precipitate l3-lactmase, the enzymatic activity of all three types was inhibited by only a small amount. Because Llactamases, in general, are known to be “floppy” molecules, the explalnation for Richmond’s observations has been that folding of the molecule under different conditions may result in conformational changes in the enzyme which, in turn, allow the type A, B, and C B-lactamases to react differently with the antiserum. However, the four recognized serotypes of B-lactamase produced by S. aureus recently have been characterized using purified enzyme and are now recognized as having distinct kinetic properties. In addition, Voladri and Kemodle have demonstrated that the kinetic differences observed among the type A, B, C, and D varients of S. aureus are due to single amino acid differences at positions close to the active site cleft. This mechanism for altering the substrate specificities of staphylococcal l3-lactamases is remarkably similar to that observed with the TEM and SHV B-lactamases, where amino acid substitutions have a dramatic effect on the substrate profile or the enzyme’s susceptibility to l3-lactamase inhibitors.
Pericellular Location of Staphylococcal R-Lactamase In contrast to the Gram-negative bacteria, Gram-positive bacteria lack outer cell membranes. The outer membrane of Gram-negative bacteria not only limits the access of B-lactam agents to their penicillin-binding protein targets, but also tends to restrict the B-lactamase to the periplasmic space where the enzyme is ideally positioned to intercept and hydrolyze any B-lactam agent before it is able to reach its targets, the penicillinbinding proteins (PBP’s). Under conditions of hyperproduction of B-lactamase by Gram-negative bacteria, the enzyme appears to also be exported into the
biofilm matrix. Because S. aureus lacks this outer cell membrane, B-lactamases produced by staphylococci have been regarded as “exoenzymes.” In reality there is ample evidence to suggest that most of the l3lactamase produced by S. aureus is cellassociated. Novick and Richmond have reported that the proportion of B-lactamase present as exoenzyme ranges from 5 to 50% of the total amount
There are at least
four different enzymatic variants of staphylococcal &lactamase. produced by the staphylococcal strain. Coles and Gross have shown that the growth environment of S. aureus has a profound influence upon the proportion of &lactamase found as exoenzyme. In addition, purification of staphylococcal B-lactamases has revealed that these enzymes are “sticky” and adsorb strongly to agarose gels, glass, sand, and the surfaces of negatively charged particles. Accordingly, Kemodle has proposed that staphylococcal B-lactamase normally adheres to the cell wall structure. Finally, the very basic nature of staphylococcal &lactamase as evidenced by its high lysine concentration and isoelectric points of 8.9 to 9.5 suggests that much of the enzyme is ionically bound to the negatively charged peptidoglycan of the cell wall allowing it to remain close to the microorganism that produced it. Buffers of an anionic nature (e.g., NaOH) appear to solubilize the enzyme by reducing the ionic binding and thus “liberating” the B-lactamase.
This association of staphylococcal l3-lactamase with the cellular structure is teleologically attractive as it results in the functional location of enzyme similar to that seen with periplasmic l3-lactamase in Gram-negative bacilli. In addition, it is likely that even when staphylococcal Blactamase is freed from cell wall structures, it remains in close proximity to the cell because it continues to be contained within the biofilm (Figure 1) which encases the staphylococcal cells/microcolonies. Extracellular enzyme released from the cell wall/biofilm may, for the most part, be an artifact of planktonic growth.
Inhibition of Staphylococcal B-Lactamases The realization that staphylococci could produce enzymes that destroyed l3-lactams resulted in a search for novel compounds that could resist such enzymatic degradation as well as a parallel search for compounds that might inhibit the Blactamase. Initially, cephalosporin C and semisynthetic penicillins such as methicillin and cloxacillin were studied as l3-lactamase inhibitors. However, the intrinsic antistaphylococcal activity of these agents was sufficient for them to be used alone. Instead, it was the discovery of specific B-lactamase inhibitors such as clavulanic acid, sulbactam, and tazobactam that allowed sufficient protection of labile penicillins to make these combinations clinically useful.
Clinical Importance of Staphylococcal B-Lactamases Clinical experience with penicillin G quickly established the importance of staphylococcal B-lactamase because the presence of this enzyme in a staphylococcal isolate usually meant therapeutic failure. As a result, antistaphylococcal antimicrobial agents with increased stability to B-lactamase such as methocillin and cephalothin were developed. Until recently, these anti-
NOTE: No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products. instructions or ideas contained in the material herein. No suggested test or procedure should be carried out unless, in the reader’s judgment, its risk is justified. Because of rapid advances in the medical sciences, we recommend that the independent verification of diagnoses and drug doses should be made. Discussions, views, and recommendations as to medical procedures, choice of drugs, and drug dosages are the responsibility of the authors. Anrimicmbics and Infecrious Diseases Newsletrer (ISSN 1069-417X) is issued monthly in one indexed volume per year by Elsevier Science Inc.. 655 Avenue of the Americas, New York. NY 10010. For customer service, phone (212) 633-3950; TOLLFREE for customers in the U.S.A. and Canada: I-88%4ES-INFO (l-888-437-4636) or fax: (212) 633-3680. Subscription price per year: $238.00; for orders outside of the United States, Canada and Mexico: $296.00. Periodical postage paid at New York, NY and at additional mailing offices. Postmaster: Send address changes to Antimicmbics andInfectious Diseases Newsletrez Elsevier Science Inc., 655 Avenue of the Americas. New York, NY 10010.
52
0196-417X/96/$0.00
+ 15.00
0 1996 Elsevier Science Inc.
Antimicrobics
and Infectious Diseases Newsletter 15(8) 1996
staphylococcal agents were considered clinically equivalent despite in vitro evidence for IS-lactamase-mediated differences. However, the observed heterogeneity of enzyme-substrate interactions for the various types of staphylococcal g-lactamase strongly suggests that there are differences in clinical efficacy which have not been fully appreciated. The recent nature of this observation precludes conclusive clinical data as, for example, isolates of S. aureu3 from therapeutic failures have not had their B-lactamases typed.
Summary In summary, it is clear that the l3-lactamases of S. aureus are more complicated that originally thought and follow a similar evolution to the B-lactamases of Gram-negative microorganisms. These differences in B-lactamases may, as seen in Gramnegative pathogens, play a role in therapeutic efftcacy. This role remains to be determined.
Bibliography Benner EJ, Bennett JV, Brodie JL, Kirby WMM: Inactivation of cephalothin and cephaloridine by Staphylococcus aureus. J Bacterial 90:1599-1604, 1965. Bennett PM, Chopra I: Molecular basis of B-lactamaseinduction in bacteria. Antimicrob. Agents Chemother37:153158,1993. Blazquez J, Baquero M-R, Canton R, Alos I, Baquero F: Characterization of a new TEM-type B-lactamaseresistantto clavulanate, sulbactam,and tazobactamin a clinical isolate of Escherichia coli. Antimicrob. Agents Chemother. 37:2059-2063,1993. Blazquez J, Morosini M-I, Negri M-C, Gonzales-LeizaM, Baquero F: Single amino acid replacementsat positions altered in naturally occurring extended spectrumTEM l3-lactamases.Antimicrob Agents Chemother.39:145-149, 1995. Bonfiglio G, Livermore DM: Behavior of B-lactamase-positiveand -negative Staphylococcus aureus isolatesin susceptibility testswith piperacillin/tazobactam and other B-lactam/B-lactamase inhibitor combinations. J Antimicrob Chemother 32:431-444, 1993. Bonfiglio G, Livermore DM: B-Lactamase types amongStaphylococcus aureus isolates in relation to susceptibility to O-lactamaseinhibitor combinations.J
Atttimicrobics
and Infectious Diseases Newsletter 15(8) 1996
Antimicrob Chemother.33:465-481,1994. Coles NW, GrossR: Influence of organic anions on the liberation of penicillinase from Staphylococcus aureus. Biochem J 102:748-752,1967. Coles NW, GrossR: Liberation of surfacecoatedpenicillinase from Staphylococcus aureus. Biochem J 102:742-747,1967. Dyke KGH: B-Lactamasesof Staphylococcusaureus. In: Hamilton-Miller JMT, Smith JT, (eds).l3-Lactamases. New York, NY, AcademicPress,291-310,1979. EastAK, Dyke KG: Cloning and sequence determination of six Staphylococcus aureus 8lactamasesand their expression in Escherichia coli and Staphylococcus aureus. J Gen Microbial 135:lOOl1015, 1989. Fong IW, Engklking ER, Kirby WMM: Relative inactivation by Staphylococcus aureus of cephalosporinsas well as penicillins. Antimicrob Agents Chemother.9:939-944, 1976. GradelskyI, Huczo E, KesslerRE, Bonner DP, Fung-tomeJ: 8Lactamase parameters of heterogeneouslyand homogeneouslymethicillin-resistant Staphylococcus aureus. J Antimicrob Chemother.31:441-442,1993. HackbarthCJ, ChambersHF: blal and blaRI Regulate8lactamase and PBP 2a production in methicillin-resistant Staphylococcus aureus. Antimicrobial Agents Chemother37:1144-1149,1993. Imtiaz V, Billings E, Knox JR, Manavathu EK, Lemer SA, Mobashery S: Inactivation of classA D-lactamaseby clavulanic acid: the role of arginine-244 in a proposednonconcertedsequenceof events.J Am Chem Sot 11544354442, 1993. Kemodle DS, ClassenDC, Burke JP,Kaiser AB: Failure of cephalosporinsto prevent Staphylococcus aureus wound infections. J Am Med Assoc 263:961-966,1990. Kemodle DS, McGraw PA, StrattonCW, Kaiser AB: Use of extracts versuswholecell bacterial suspensionsin the identilication of Staphylococcus aureus &lactamasevariants. Antimicrob Agents Chemother34420-425, 1990. Kemodle DS, Zygmunt DJ, McGraw PA, Chipley JR: Purification of Sraphylococcus aureus B-lactamasesby using sequentialcation-exchangeand affinity chromatography.Antimicrob Agents Chemother34:2177-2183,1990. Kirby WMM: Extraction of a highy potent penicillin inactivator from penicillinresistantstaphylococci. Science99:452453.1944.
Lacey RW, StokesA: Susceptibility of the “penicillinase resistant” penicillins and
0 1996 Elsevier Science Inc.
cephalosporinsto penicillinase of Staphylococcus aureus. J Clin Path01 30:35-39, 1977. McDouglas LK, Thomsberry C: The role of 8-lactamasein Staphylococcus aureus resistanceto penicillinase-resistant penicillins and cephalosporins.J Clin Microbial 23:832-839, 1986. Musher DM, McKenzie SO: Infections due to Staphylococcus aureus. Medicine 56:383-409, 1977. Novick RP,Richmond MH: Nature and interactions of the genetic elements governing penicillinase synthesisin Staphylococcus aureus. J Bacterial 90:467-480, 1965. Richmond MH: Purification and properties of penicillinase from Staphylococcus aureus. Biochem J 94584-593, 1963. Richmond MH: Wild-type variants of exopenicillinase from Staphylococcus aureus. Biochem J 94:584-593, 1965. RobsonB, Pain RH: Suitability of a penicillinase from Staphylococcus aureus as a model for refolding studies.Biochem J 155:325-330,1976. Rosdahl VT: Naturally occurring constitutive B-lactamaseof novel serotypein Staphylococcus aureus. J Gen Microbial 77:229-231, 1973. SougakoffW, GoussardS, GerbaudG, et al.: Plasmid-mediatedresistanceto thirdgenerationcephalosporinscausedby point mutations in TEM-type penicillinasegenes.Rev Infect Dis 10:879-884, 1988. Spink WW: Staphylococcalinfections and problem of antibiotic-resistant staphylococci. Arch Intern Med 94:167-196,1954. Voladri R, Kemodle DS: Substitution of asparagenefor serine at amino acid 2 16 of kinetic type A Staphylococcus aweus B-lactamaseproducesa mutant enzyme that is kinetically indistinguishable from type C B-lactamase.abstractA95. In: Programand Abstractsof the 93rd GeneralMeeting of the American Society for Microbiology, Atlanta, GA, May, 1993. Voladri R, Tummuru M, Kemodle DS: Substitution of alanine for threonine at amino acid 128 of kinetic type A Staphylococcus aureus O-lactamaseproducesa mutant enzyme that is kinetically indistinguishable from type D 8lactamase.Abstract A94.111:Programand Abstractsof the 93rd general Meeting of the American Society for Microbiology, Atlanta, GA, May 1993.
0196-417X/96/$0.00+
15.00
53
Editor-in-Chief Charles W. Stratton, MD Vanderbilt University School of Medicine Nashville, Tennessee Full editorial board appears on back cover
Volume 15, Number 8 August 1996
Staphylococcal O-Lactamases Charles W. Stratton, MD Associate Professor of Pathology and Medicine Vanderbilt University School of Medicine Nashville, Tennessee
Introduction Staphylococcal l3-lactamase was among the first bacterial enzymes recognized as capable of destroying penicillin. Not suprisingly, this highly potent penicillin inactivator was initially designated a “penicillinase.” Later, this enzyme, like others in its class, was designated a B-lactamase due to its hydrolytic action specifically directed against the l3-lactam ring. B-lactamases produced by strains of Staphylococcus aureus were long considered a single and unique extracellular enzyme directed primarily against penicillins. Immunological variants of staphylococcal l3-lactamase were described, but were thought to be conformational changes caused by refolding of a single enzyme. Fifty years later, each of these early concepts has required modifications. First, and most importantly, Kernodle and colleagues have clearly demonstrated that there are at least four different enzymatic variants of staphylococcal B-lactamase. Some l3-lactamases produced by S. aureus isolates readily hydrolyze cephalosporins as well as penicillins. Moreover, the location of staphlococcal R-lactamases is more accurately described as pericellular than as extracellular. These concepts and other important aspects of staphylococcal8 lactamase are discussed in this review.
AIDIEX
15(8)51-58,1996
Genetic Aspects of Staphylococcal B-Lactamases The B-lactamase production of S. aureus is typically inducible and usually associated with transducible plasmids or with transposons. The nucleotide sequencing of l3-lactamase genes found on either plasmids or transposons appears identical suggesting a common origin of this gene. Of interest is that this gene seems to have been passed to the Enterococcus species. There are three regulatory genes (blal, blaR1, and blaR2) that are recognized as influencing the expression of the l3-lactamasegene (blaZ) of S. aureus. The fist, blal, produces a diffusible repressor protein, bla1, which can bind to the operator site of the l3-lactamase structural gene and prevent its transcription by RNA polymerase. The exact role of the other two genes, bluRI and blaR2, is less clear, but both appear to produce interactive proteins which mediate the induction of the B-lactamase gene. One possibility is that blaR1 protein from the cytoplasmic membrane interacts with the blaI/bZaZ complex in the cytoplasm resulting in the binding of the repressor protein blaI to blaR1 which frees the operator site of blaZ so that transcription can occur. The interactive protein, blaR2, may, in turn, antagonize the gene, bluRI. Evidence for this can be found in mutational studies where the loss of blaR1 function results in noninducible basal-level expression of R-lactamase while the loss of blaR2 function confers highlevel constitutive expression. In
Elsevier
addittion to regulating B-lactamase, these genes also appear to regulate the expression of the altered penicillinbinding protein (PBP-2a) found in methicillin-resistant S. aureus.
Enzymatic Activity of Staphylococcal ii-Lactamases Initial kinetic studies of staphylococcal B-lactamase were done for the most part with impure enzyme, making the exact interpretation of results difficult. However, these studies as well as preliminary analysis of the amino acid compositions from immunologically distinct strains suggested that only one enzyme was produced by all B-lactamase producing strains of S. aureus. Yet, Richmond in 1965 found that antiserum prepared against purified type A enzyme stimulated the activity of the A-type enzyme almost 4-fold whereas B-type enzyme was only slightly stimulated; C-type was not stimulated at all.
In This Issue Staphylococcal D-Lactamases. . . . .51 Charles W. Stratton, MD
Peritonitis in a Patient Undergoing Peritoneal Dialysis Caused by Mycobacterium abscessus . . . . . . . . 54 A case report
Endocarditis on a Native Aortic Valve Caused by Actinobacillus actinomycetemcomitans . . . . . . . . . .55 A case report
0196-417X/96/$0.00+
15.00
Although the antiserum was able to precipitate l3-lactmase, the enzymatic activity of all three types was inhibited by only a small amount. Because Llactamases, in general, are known to be “floppy” molecules, the explalnation for Richmond’s observations has been that folding of the molecule under different conditions may result in conformational changes in the enzyme which, in turn, allow the type A, B, and C B-lactamases to react differently with the antiserum. However, the four recognized serotypes of B-lactamase produced by S. aureus recently have been characterized using purified enzyme and are now recognized as having distinct kinetic properties. In addition, Voladri and Kemodle have demonstrated that the kinetic differences observed among the type A, B, C, and D varients of S. aureus are due to single amino acid differences at positions close to the active site cleft. This mechanism for altering the substrate specificities of staphylococcal l3-lactamases is remarkably similar to that observed with the TEM and SHV B-lactamases, where amino acid substitutions have a dramatic effect on the substrate profile or the enzyme’s susceptibility to l3-lactamase inhibitors.
Pericellular Location of Staphylococcal R-Lactamase In contrast to the Gram-negative bacteria, Gram-positive bacteria lack outer cell membranes. The outer membrane of Gram-negative bacteria not only limits the access of B-lactam agents to their penicillin-binding protein targets, but also tends to restrict the B-lactamase to the periplasmic space where the enzyme is ideally positioned to intercept and hydrolyze any B-lactam agent before it is able to reach its targets, the penicillinbinding proteins (PBP’s). Under conditions of hyperproduction of B-lactamase by Gram-negative bacteria, the enzyme appears to also be exported into the
biofilm matrix. Because S. aureus lacks this outer cell membrane, B-lactamases produced by staphylococci have been regarded as “exoenzymes.” In reality there is ample evidence to suggest that most of the l3lactamase produced by S. aureus is cellassociated. Novick and Richmond have reported that the proportion of B-lactamase present as exoenzyme ranges from 5 to 50% of the total amount
There are at least
four different enzymatic variants of staphylococcal &lactamase. produced by the staphylococcal strain. Coles and Gross have shown that the growth environment of S. aureus has a profound influence upon the proportion of &lactamase found as exoenzyme. In addition, purification of staphylococcal B-lactamases has revealed that these enzymes are “sticky” and adsorb strongly to agarose gels, glass, sand, and the surfaces of negatively charged particles. Accordingly, Kemodle has proposed that staphylococcal B-lactamase normally adheres to the cell wall structure. Finally, the very basic nature of staphylococcal &lactamase as evidenced by its high lysine concentration and isoelectric points of 8.9 to 9.5 suggests that much of the enzyme is ionically bound to the negatively charged peptidoglycan of the cell wall allowing it to remain close to the microorganism that produced it. Buffers of an anionic nature (e.g., NaOH) appear to solubilize the enzyme by reducing the ionic binding and thus “liberating” the B-lactamase.
This association of staphylococcal l3-lactamase with the cellular structure is teleologically attractive as it results in the functional location of enzyme similar to that seen with periplasmic l3-lactamase in Gram-negative bacilli. In addition, it is likely that even when staphylococcal Blactamase is freed from cell wall structures, it remains in close proximity to the cell because it continues to be contained within the biofilm (Figure 1) which encases the staphylococcal cells/microcolonies. Extracellular enzyme released from the cell wall/biofilm may, for the most part, be an artifact of planktonic growth.
Inhibition of Staphylococcal B-Lactamases The realization that staphylococci could produce enzymes that destroyed l3-lactams resulted in a search for novel compounds that could resist such enzymatic degradation as well as a parallel search for compounds that might inhibit the Blactamase. Initially, cephalosporin C and semisynthetic penicillins such as methicillin and cloxacillin were studied as l3-lactamase inhibitors. However, the intrinsic antistaphylococcal activity of these agents was sufficient for them to be used alone. Instead, it was the discovery of specific B-lactamase inhibitors such as clavulanic acid, sulbactam, and tazobactam that allowed sufficient protection of labile penicillins to make these combinations clinically useful.
Clinical Importance of Staphylococcal B-Lactamases Clinical experience with penicillin G quickly established the importance of staphylococcal B-lactamase because the presence of this enzyme in a staphylococcal isolate usually meant therapeutic failure. As a result, antistaphylococcal antimicrobial agents with increased stability to B-lactamase such as methocillin and cephalothin were developed. Until recently, these anti-
NOTE: No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products. instructions or ideas contained in the material herein. No suggested test or procedure should be carried out unless, in the reader’s judgment, its risk is justified. Because of rapid advances in the medical sciences, we recommend that the independent verification of diagnoses and drug doses should be made. Discussions, views, and recommendations as to medical procedures, choice of drugs, and drug dosages are the responsibility of the authors. Anrimicmbics and Infecrious Diseases Newsletrer (ISSN 1069-417X) is issued monthly in one indexed volume per year by Elsevier Science Inc.. 655 Avenue of the Americas, New York. NY 10010. For customer service, phone (212) 633-3950; TOLLFREE for customers in the U.S.A. and Canada: I-88%4ES-INFO (l-888-437-4636) or fax: (212) 633-3680. Subscription price per year: $238.00; for orders outside of the United States, Canada and Mexico: $296.00. Periodical postage paid at New York, NY and at additional mailing offices. Postmaster: Send address changes to Antimicmbics andInfectious Diseases Newsletrez Elsevier Science Inc., 655 Avenue of the Americas. New York, NY 10010.
52
0196-417X/96/$0.00
+ 15.00
0 1996 Elsevier Science Inc.
Antimicrobics
and Infectious Diseases Newsletter 15(8) 1996
staphylococcal agents were considered clinically equivalent despite in vitro evidence for IS-lactamase-mediated differences. However, the observed heterogeneity of enzyme-substrate interactions for the various types of staphylococcal g-lactamase strongly suggests that there are differences in clinical efficacy which have not been fully appreciated. The recent nature of this observation precludes conclusive clinical data as, for example, isolates of S. aureu3 from therapeutic failures have not had their B-lactamases typed.
Summary In summary, it is clear that the l3-lactamases of S. aureus are more complicated that originally thought and follow a similar evolution to the B-lactamases of Gram-negative microorganisms. These differences in B-lactamases may, as seen in Gramnegative pathogens, play a role in therapeutic efftcacy. This role remains to be determined.
Bibliography Benner EJ, Bennett JV, Brodie JL, Kirby WMM: Inactivation of cephalothin and cephaloridine by Staphylococcus aureus. J Bacterial 90:1599-1604, 1965. Bennett PM, Chopra I: Molecular basis of B-lactamaseinduction in bacteria. Antimicrob. Agents Chemother37:153158,1993. Blazquez J, Baquero M-R, Canton R, Alos I, Baquero F: Characterization of a new TEM-type B-lactamaseresistantto clavulanate, sulbactam,and tazobactamin a clinical isolate of Escherichia coli. Antimicrob. Agents Chemother. 37:2059-2063,1993. Blazquez J, Morosini M-I, Negri M-C, Gonzales-LeizaM, Baquero F: Single amino acid replacementsat positions altered in naturally occurring extended spectrumTEM l3-lactamases.Antimicrob Agents Chemother.39:145-149, 1995. Bonfiglio G, Livermore DM: Behavior of B-lactamase-positiveand -negative Staphylococcus aureus isolatesin susceptibility testswith piperacillin/tazobactam and other B-lactam/B-lactamase inhibitor combinations. J Antimicrob Chemother 32:431-444, 1993. Bonfiglio G, Livermore DM: B-Lactamase types amongStaphylococcus aureus isolates in relation to susceptibility to O-lactamaseinhibitor combinations.J
Atttimicrobics
and Infectious Diseases Newsletter 15(8) 1996
Antimicrob Chemother.33:465-481,1994. Coles NW, GrossR: Influence of organic anions on the liberation of penicillinase from Staphylococcus aureus. Biochem J 102:748-752,1967. Coles NW, GrossR: Liberation of surfacecoatedpenicillinase from Staphylococcus aureus. Biochem J 102:742-747,1967. Dyke KGH: B-Lactamasesof Staphylococcusaureus. In: Hamilton-Miller JMT, Smith JT, (eds).l3-Lactamases. New York, NY, AcademicPress,291-310,1979. EastAK, Dyke KG: Cloning and sequence determination of six Staphylococcus aureus 8lactamasesand their expression in Escherichia coli and Staphylococcus aureus. J Gen Microbial 135:lOOl1015, 1989. Fong IW, Engklking ER, Kirby WMM: Relative inactivation by Staphylococcus aureus of cephalosporinsas well as penicillins. Antimicrob Agents Chemother.9:939-944, 1976. GradelskyI, Huczo E, KesslerRE, Bonner DP, Fung-tomeJ: 8Lactamase parameters of heterogeneouslyand homogeneouslymethicillin-resistant Staphylococcus aureus. J Antimicrob Chemother.31:441-442,1993. HackbarthCJ, ChambersHF: blal and blaRI Regulate8lactamase and PBP 2a production in methicillin-resistant Staphylococcus aureus. Antimicrobial Agents Chemother37:1144-1149,1993. Imtiaz V, Billings E, Knox JR, Manavathu EK, Lemer SA, Mobashery S: Inactivation of classA D-lactamaseby clavulanic acid: the role of arginine-244 in a proposednonconcertedsequenceof events.J Am Chem Sot 11544354442, 1993. Kemodle DS, ClassenDC, Burke JP,Kaiser AB: Failure of cephalosporinsto prevent Staphylococcus aureus wound infections. J Am Med Assoc 263:961-966,1990. Kemodle DS, McGraw PA, StrattonCW, Kaiser AB: Use of extracts versuswholecell bacterial suspensionsin the identilication of Staphylococcus aureus &lactamasevariants. Antimicrob Agents Chemother34420-425, 1990. Kemodle DS, Zygmunt DJ, McGraw PA, Chipley JR: Purification of Sraphylococcus aureus B-lactamasesby using sequentialcation-exchangeand affinity chromatography.Antimicrob Agents Chemother34:2177-2183,1990. Kirby WMM: Extraction of a highy potent penicillin inactivator from penicillinresistantstaphylococci. Science99:452453.1944.
Lacey RW, StokesA: Susceptibility of the “penicillinase resistant” penicillins and
0 1996 Elsevier Science Inc.
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