scholarly journals Clavulanate inactivation of Staphylococcus aureus β-lactamase

1989 ◽  
Vol 258 (1) ◽  
pp. 205-209 ◽  
Author(s):  
I Rizwi ◽  
A K Tan ◽  
A L Fink ◽  
R Virden
Keyword(s):  
Staphylococcus Aureus ◽  
Catalytic Activity ◽  
Clavulanic Acid ◽  
Low Temperatures ◽  
Stable Form ◽  
Beta Lactamase ◽  
Trans Form ◽  
Conformational Effects ◽  
Enzyme Intermediate ◽  
Enamine Formation

The interaction of clavulanic acid with beta-lactamase from Staphylococcus aureus was investigated, particularly with a view to determining whether conformational effects are involved. The inactivation at neutral pH is essentially stoichiometric, leading to an inactive species with an enamine chromophore. Two forms of the enamine were observed, the first-formed having a positive ellipticity with a maximum near 290 nm. This species slowly converted into the stable form of the inactivated enzyme that had a negative ellipticity with a minimum at 275 nm. This change in sign of the ellipticity of the enamine is consistent with the previously proposed cis-trans isomerization of the enamine [Cartwright & Coulson (1979) Nature (London) 278, 360-361). Both the far-u.v.c.d. and the intrinsic viscosity of the inactivated enzyme indicated that negligible change in conformation of the enzyme accompanied inactivation. The rates of inactivation and enamine formation were compared at low temperatures, where the initial rates were slow enough to be monitored. The rate of loss of 95% of the catalytic activity was almost 100-fold faster than the rate of formation of the first-formed enamine species. The remaining 5% activity was lost with a rate comparable with that for formation of the initial enamine. The simplest explanation of these results is that a relatively stable acyl-enzyme intermediate builds up initially and more slowly partitions between turnover (hydrolysis) and enamine formation. The initially formed enamine is in the cis conformation but slowly isomerizes to the more stable trans form.

scholarly journals In vitro assessment of the effect of clavulanic acid at concentrations achieved in human serum on the bactericidal activity of amoxicillin at physiological concentrations against Staphylococcus aureus: implications for dosage regimens.

1997 ◽  
Vol 41 (6) ◽  
pp. 1403-1405 ◽  
Author(s):  
L Aguilar ◽  
M Martín ◽  
I P Balcabao ◽  
M L Gómez-Lus ◽  
R Dal-Ré ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Human Serum ◽  
Clavulanic Acid ◽  
Beta Lactamase ◽  
Postantibiotic Effect ◽  
Initial Inoculum ◽  
Dosage Regimens ◽  
Amoxicillin Clavulanic Acid ◽  
In Vitro Assessment

The effects on Staphylococcus aureus viability and beta-lactamase activity of concentrations that simulated those in human serum after a combined dose of 875 mg of amoxicillin and 125 mg of clavulanic acid were studied in an in vitro pharmacodynamic model. Six hours of preexposure to concentrations of the amoxicillin-clavulanic acid combination that were higher than the amoxicillin-clavulanic acid MIC led to a reduction of the initial inoculum of >90% and to a significant decrease of beta-lactamase activity versus those of the control even from 6 h, when concentrations were subinhibitory. The postantibiotic effect and post-beta-lactamase inhibitor effect contributed to these results.

scholarly journals Identification of the site of covalent attachment of nafcillin, a reversible suicide inhibitor of β-lactamase

1992 ◽  
Vol 281 (1) ◽  
pp. 191-196 ◽  
Author(s):  
A K Tan ◽  
A L Fink
Keyword(s):  
Staphylococcus Aureus ◽  
Rate Constant ◽  
Active Site ◽  
Covalent Attachment ◽  
Beta Lactamase ◽  
Peptide Fragment ◽  
Serine Residue ◽  
Complete Inactivation ◽  
Enzyme Intermediate ◽  
Inhibited Enzyme

Nafcillin was shown to reversibly inhibit beta-lactamase from Staphylococcus aureus PC1 with characteristics indicative of a type A inhibitor [Citri, Samuni & Zyk (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 1048-1052]. At nafcillin concentrations above 80 mM, complete inactivation occurred within 200 s. Upon removal of the excess nafcillin the inhibited enzyme was re-activated completely, with a rate constant of 2.0 x 10(-3) s-1 (25 degrees C). The inhibited enzyme was shown to be in the form of a covalent acyl-enzyme intermediate. Digestion by pepsin and trypsin yielded a single nafcillin-labelled peptide fragment which was isolated, sequenced and shown to be: Ala-Tyr-Ala-Ser-Thr-Ser-Lys. This sequence corresponds to the region surrounding the active-site serine residue, Ser-70, indicating that the inhibitor is covalently attached to the same residue as productive substrates.

In vivo protection of penicillin-susceptible Bacteroides melaninogenicus from penicillin by facultative bacteria which produce beta-lactamase

1984 ◽  
Vol 30 (1) ◽  
pp. 98-104 ◽  
Author(s):  
Itzhak Brook ◽  
Garry Pazzaglia ◽  
James C. Coolbaugh ◽  
Richard I. Walker
Keyword(s):  
Staphylococcus Aureus ◽  
Combination Therapy ◽  
Clavulanic Acid ◽  
Single Agent ◽  
Mixed Infections ◽  
Beta Lactamase ◽  
Penicillin Therapy ◽  
And Staphylococcus Aureus ◽  
Antimicrobial Combinations

We investigated the possibility that beta-lactamase producing strains of Klebsiella pneumoniae and Staphylococcus aureus can protect organisms of the Bacteroides melaninogenicus group from penicillin. A mixed infection was induced in mice in the form of a subcutaneous abscess involving a penicillin-susceptible encapsulated B. melaninogenicus, and a beta-lactamase producing strain of either K. pneumoniae or S. aureus. The infected animals were treated for 7 days with single or combined antimicrobial therapy. The single agents used were penicillin, clavulanic acid, metronidazole, and gentamicin. The antimicrobial combinations were penicillin and clavulanic acid, penicillin and gentamicin, and metronidazole and gentamicin. Administration of a single agent was effective in treating abscesses caused by susceptible organisms. The only effective therapy for mixed infections was by combination therapy of penicillin and clavulanic acid or metronidazole and gentamicin. This study supports the hypothesis that beta-lactamase producing facultative bacteria may shield their anaerobic counterparts from penicillin therapy, thereby contributing to the persistence of the infection.

Molecular Characterization of Methicillin Resistant and Extended Spectrum β-Lactamase Staphylococcus aureus Isolated from Burn Patients

2020 ◽  
pp. 145-151
Author(s):  
Shawnm Ahmed Aziz
Keyword(s):  
Staphylococcus Aureus ◽  
Methicillin Resistance ◽  
Vancomycin Resistance ◽  
World Health ◽  
Molecular Technique ◽  
Burn Patients ◽  
Beta Lactamase ◽  
Beta Lactam ◽  
Extended Spectrum Beta Lactamase ◽  
Extended Spectrum

Antibiotic resistance has become a major world health challenge and has limited the ability of physician's treatment. Staphylococcus aureus the most notorious pathogens causes morbidity and mortality especially in burn patients. However, Staphylococcus aureus rapidly acquired resistance to multiple antibiotics. Vancomycin, a glycopeptide antibiotic remains a drug of choice for treatment of severe Methicillin Resistance S. aureus infections. This study aimed to detect the emergence of beta-lactam and glycopeptide resistance genes. 50 clinical specimens of S. aureus collected from burn patients in burn and plastic surgery units in Sulaimani-Iraq city. All specimens were confirmed to be positive for S. aureus. All the isolates were assessed for their susceptibility to different antibiotics depending on NCCL standards, followed by Extended Spectrum Beta Lactamase detection by double disk diffusion synergy test. The production of β- lactamases was evaluated in the isolated strains by several routine methods and polymerase chain reaction. Among the isolates 94% were Methicillin resistance and 34.28% were Extended Spectrum Beta Lactamase producer. PCR based molecular technique was done for the bla genes related to β- lactamase enzymes by the specific primers, as well as genes which related to reduced sensitivity to Vancomycin were detected. The results indicated that all isolated showed the PBP1, PBP2, PBP3, PBP4, trfA and trfB, graSR, vraS except the vraR gene and the prolonged therapy of Methicillin resistance infection with teicoplanin have been associated with progress of resistance and the rise of tecoplanin resistance may be a prologue to evolving Vancomycin resistance. In conclusion, beta-lactam over taking can rise Vancomycin- Intermediate S. aureus strains leading to appearance of Vancomycin resistance although the treatment of Vancomycin resistant infections is challenging.

scholarly journals Pé diabético: análise bacteriológica de 141 casos

2004 ◽  
Vol 48 (3) ◽  
pp. 398-405 ◽  
Author(s):  
Cibele B.M. Carvalho ◽  
Renato M. Neto ◽  
Luciana P. Aragão ◽  
Margarida M. Oliveira ◽  
Marcelo B. Nogueira ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Staphylococcus Aureus ◽  
Streptococcus Pyogenes ◽  
Beta Lactamase

Diabetes mellitus (DM) é uma doença progressiva que apresenta complicações freqüentes, em especial a infecção nos pés. Realizamos um estudo prospectivo com 141 pacientes com DM e úlceras infectadas nos pés, conduzido no Centro Integrado de Diabetes e Hipertensão da UFC no período de março/2000 a novembro/2001. A maioria apresentava infecção avaliada como graus I e II da classificação de Wagner. As amostras foram cultivadas utilizando-se meios seletivos, e a identificação bacteriana e os antibiogramas foram realizados através de metodologia convencional e automatizados. Os patógenos mais freqüentemente isolados foram as enterobactérias (83,7%), Staphylococcus aureus (43,3%) e bactérias anaeróbias (17%). Cepas de Streptococcus pyogenes foram isoladas de 7,8% dos pacientes. Cepas produtoras de beta-lactamase de espectro ampliado e cepas de Staphylococcus aureus resistentes à oxacilina foram isoladas de 6% e 11,6% dos pacientes, respectivamente. A resistência aos antimicrobianos vem se tornando cada vez mais comum, mesmo em pacientes com infecção adquirida na comunidade. Investimentos em diagnóstico etiológico das infecções e estratégias racionais no uso de antimicrobianos fazem-se necessários na tentativa de evitar tratamentos inadequados e suas já conhecidas conseqüências.

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