ISSN:0009-3157    

DOI:10.1159/000239494

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Analysis of staphylococcal resistance to antimicrobial agents has revealed three main biochemical mechanisms of resistance that are common to other bacteria: (1) inactivation of the antimicrobial by enzymes modifying or hydrolysing the agent, (2) target receptor alteration – by acquisition of a target with reduced affinity for the antimicrobial, acquisition of enzymes converting a native target, or mutation of genes encoding the native target, (3) limiting access of the antimicrobial, mainly by active efflux of the antibiotic. Often, several mechanisms confer resistance to the same antimicrobial agent. Staphylococcal resistance has evolved by acquisition of resistance determinants and by mutation or recombination events in existing staphylococcal DNA. Effective horizontal distribution of DNA among staphylococci is possible via transformation, transduction, plasmid-mediated conjugation or phage-mediated conjugation. Plasmid-mediated DNA mobilization and the location of R determinants on transposable elements are important genetic features of Staphylococcus, allowing versatility of resistanc

ISSN:0009-3157    

DOI:10.1159/000239495

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Pan-European data on the antibiotic resistance of staphylococci are reviewed, mainly based on unpublished surveillance studies of the Paul Ehrlich Society for Chemotherapy. The prevalence of multiresistant strains of methicillin-resistant Staphylococcus aureus (MRSA) varied between European countries, but were generally lowest in northern Europe ( 30%). Antibiotic resistance was more prevalent in coagulase-negative staphylococci (CNS) than in coagulase-positive staphylococci, but the differences between countries was less pronounced. Although glyco-peptide resistance in S. aureus has not been found in vivo, glycopeptide-resistant CNS strains already exist. Despite the growing awareness and clinical significance of MRSA and multiresistant CNS strains in recent years, resistance to penicillin did not change between 1975 and 1990, whereas resistance to oxacillin increased slightly and resistance to ciprofloxacin increased markedly.

ISSN:0009-3157    

DOI:10.1159/000239497

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Methicillin resistance in staphylococci is primarily due to the methicillin resistance determinant, which produces an additional low-affinity penicillin-binding protein (PBP), PBP2′. Expression of PBP2′ is controlled by its own regulatory element and has the same induction system as the β-lactamases. Methicillin resistance levels do not, however, correlate with the amount of PBP2′ produced and are determined by chromosomal genes. Methicillin resistance in clinical isolates that do not contain the methicillin resistance determinant, and therefore do not produce PBP2′, is due to changes in the amount and/or affinity of the cells’ own PBPs, to penicillinase hyperproduction against a specific genetic background, or to synthesis of a meth

ISSN:0009-3157    

DOI:10.1159/000239498

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

To date, no strains of Staphylococcus aureus fully resistant to vancomycin or teicoplanin have been reported, though the minimal inhibitory concentrations (MIC) for teicoplanin are rising as a result of exposure to the antibiotic. This resistance is constitutive. Genes which confer inducible resistance with high MIC levels are found in the enterococci and are capable of conjugative transfer to S. aureus under conditions that mimic those encountered in nature. Enterococci and staphylococci share other resistance determinants and there seems no reason to suppose that staphylococci will not eventually acquire and express high-level vancomycin resistance.

ISSN:0009-3157    

DOI:10.1159/000239499

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Staphylococcal infections continue to be among the most common infections. Methicillin resistance is a common phenomenon, particularly among nosocomial Staphylococcus aureus and coagulase-negative staphylococci. Although wide variations are observed between countries or cities, methicillin resistance is often associated with multiresistance, which includes resistance to rifampicin and fluoroquinolones. In areas where methicillin resistance is common, glycopeptides (vancomycin or teicoplanin) represent the first-line treatment. For both drugs, attention should be paid to appropriate doses and dosing regimens and to the control of serum levels. In septicaemia and endocarditis developed on native valves, the benefit of a combination with an aminoglycoside or any other agent has not been clearly established. Animal studies suggest that combination therapy with a quinolone or rifampicin should be considered, particularly in infections involving foreign bodies. In CNS infections, combinations such as cefotaxime plus fosfomycin, or rifampicin plus a fluoroquinolone can be used. Multiple resistance, however, may limit the efficacy of such combinations. In areas where methicillin resistance is less common, initial therapy can be cefamandole with or without an aminoglycoside, or rifampicin plus a fluoroquinolone. Whatever the treatment, careful evaluation of the clinical response 48 h after initiation of therapy is required.

ISSN:0009-3157    

DOI:10.1159/000239500

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Coagulase-negative staphylococci, particularly methicillin-resistant strains of Staphylococcus epidermidis (MRSE), are common causes of hospital infections in Sweden today. In several studies, it has been shown that some strains of S. epidermidis are more widespread than others in a particular hospital. An enhanced ability to colonize human skin may possibly explain why certain strains spread epidemically. MRSE may be transmitted between patients by many possible routes, though it is difficult to determine which is most important. Direct and indirect contact transfer occur, as for other bacteria, but, unlike for most other bacteria, air dispersal on loosened skin scales is also very important. Another possible route of transmission is on the clothes of staff. To reduce spread of MRSE in hospitals, it is important that MRSE should not become a part of the resident flora of patients and staff. More investigations are needed, including studies of the effects of different systemic antibiotics on the microbial flora of the skin.

ISSN:0009-3157    

DOI:10.1159/000239501

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Staphylococcus aureus small colony variants (SCVs) have been found to cause persistent and antibiotic-resistant infections in humans. Persistence seems to relate to the ability of SCVs to reside within host cells without lysing them. The lytic activity of S. aureus arises from the production of α-toxin, and SCVs are non-α-toxin-producing. The biochemical basis for the SCV phenotype has been linked to decreased electron transport which leads to reduced α-toxin production. Electron transport is diminished due to blocks in either haemin or menadione biosynthesis, which results in the loss of the menaquinone or cytochrome components of the electron transport chain, respectively. Reduction in electron transport activity also causes reduced coagulase production, decreased pigmentation, and reduced aminoglycoside uptake. The decreased uptake of aminoglycosides comes from the weaker electrochemical gradient across the cell membrane. The SCVs are not only more resistant to the positively charged aminoglycosides, but they are also resistant to several other positively charged antistaphylococcal compounds: protamine, some L-antibiotics, and platelet microbicidal proteins. The multiple phenotypic changes, such as decreased haemolytic activity (α-toxin), decreased coagulase activity, reduced pigmentation, and slow growth, make the SCVs difficult to recognize as S. aureus. Finally, the intracellular milieu of the mammalian cell enhances the production of SCVs. Of interest, a number of other genera (both Gram-positive and Gram-negative) also produce electron transport SCVs that are resistant to aminoglycosides, hence the observations with S. aureus may apply to other types of organisms. Thus, the SCV phenotype allows S. aureus to persist within host cells and resist antimicrobial agents, and the atypical colonial morphology may lead to misidentification of these organisms. Because many of the SCVs are menadione auxotrophs, the addition of vitamin K to the medium increases the activity of antibiotics against these variants which might prove to be a valuable therapeutic adju

ISSN:0009-3157    

DOI:10.1159/000239502

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Methicillin-resistant Staphylococcus aureus 500 beds) and 15/31 smaller hospitals ( < 500 beds) answered the survey. (A second random sample survey of non-respondent hospitals (n = 5) produced very similar results to those seen in the initial survey.) All large hospitals reported outbreaks of MRSA nosocomial infections (average 8.0 ± 5.9 new cases/month) with multiply-resistant strains. Only four of the smaller hospitals reported MRSA infections (average 1.0 new cases/month). The main infection control procedures were active search for carriers (100%), special isolation wards (66%), nasal decolonization of health-care workers (88%, using mupirocin in 66% of cases), and stating of MRSA condition in the discharge report (100%). The control procedures currently recommended for MRSA infections are widely accepted and followed, but appear to be only partially successful in the long term

ISSN:0009-3157    

DOI:10.1159/000239503

出版商:S. Karger AG    

年代:1996

数据来源: Karger

ISSN:0009-3157    

DOI:10.1159/000239504

出版商:S. Karger AG    

年代:1996

数据来源: Karger