Disease relevance of beta-Lactam Resistance

• Multiple beta-lactam resistance in Enterobacter cloacae following ceftazidime monotherapy [1].
• Consumption of imipenem correlates with beta-lactam resistance in Pseudomonas aeruginosa [2].
• Beta-lactam resistance mechanisms of methicillin-resistant Staphylococcus aureus [3].
• The contribution of penicillin-binding protein 5 (PBP 5) to intrinsic and acquired beta-lactam resistance was investigated by constructing isogenic strains of Enterococcus faecium producing different PBP 5 [4].
• Tn4555 is an MTn that encodes beta-lactam resistance, and it is efficiently mobilized by the Bacteroides CTns via a tetracycline (TET)-inducible mechanism [5].

High impact information on beta-Lactam Resistance

• Pneumococcal beta-lactam resistance due to a conformational change in penicillin-binding protein 2x [6].
• For the first time all the mutations of a PBP relevant to beta-lactam resistance have been identified, providing new mechanistic insights [6].
• However, the bppA2 deletion impaired expression of intrinsic beta-lactam resistance suggesting that the low affinity penicillin-binding protein 5 did not function optimally with precursors substituted by a single alanine [7].
• When organisms became resistant to ciprofloxacin (MIC greater than 2 micrograms/ml), they showed no concomitant new aminoglycoside or beta-lactam resistance [8].
• Acquisition of beta-lactam resistance was consistently associated with transfer of a mosaic block containing the C-terminal portion of PBP 1A [9].

Chemical compound and disease context of beta-Lactam Resistance

• Mechanism of chloramphenicol and beta-lactam resistance in clinical isolates of Yersinia enterocolitica [10].
• Selection of cefoxitin-resistant bacteroides thetaiotaomicron mutants and mechanisms involved in beta-lactam resistance [11].

Biological context of beta-Lactam Resistance

• Thus, particular point mutations in PBP 5 and combinations thereof may lead to high-level beta-lactam resistance in E. faecium [12].
• The beta-lactam resistance gene mecA of Staphylococcus aureus is carried by a novel mobile genetic element, designated staphylococcal cassette chromosome mec (SCCmec), identified in the chromosome of a Japanese methicillin-resistant S. aureus (MRSA) strain [13].
• Six avian isolates with antibiotic resistance were detected: two were nalidixic acid resistant and four had a particular beta-lactam resistance pattern [14].
• The molecular size of the plasmid pBFKW1 which seemed to encode the beta-lactam resistance and beta-lactamase production was estimated ca. 40 kb by the analysis of endonuclease digest [15].
• The antimicrobial susceptibility testing depicted the emergence of high-level aminoglycoside and beta-lactam resistance among different species apart from intrinsic vancomycin resistance by some species, while all the species tested were susceptible for linezolid and teicoplanin [16].

Associations of beta-Lactam Resistance with chemical compounds

• We conclude that, with the notable exception of imipenem, the MexAB-OprM pump contributes significantly to beta-lactam resistance in both beta-lactamase-negative and beta-lactamase-inducible strains, while the contribution of the MexAB-OprM efflux system is negligible in strains with overexpressed beta-lactamase [17].
• Transformation of broad-spectrum beta-lactam resistance into ampicillin-susceptible H. influenzae RDnov was accomplished [18].
• These studies suggest that beta-lactamase is the major mechanism of beta-lactam resistance in this species and that Augmentin is the first oral beta-lactam with good potential for treating infections due to N. brasiliensis [19].
• The increases in the Ki values of both clavulanic acid and tazobactam for the enzyme with the triple mutation were consistent with the observed bacterial resistance to the reversibility of beta-lactam resistance with these inhibitors [20].
• Subculturing of the four strains with decreased penicillin susceptibility in amoxicillin (with or without clavulanate) or cefuroxime did not select for beta-lactam resistance [21].

Gene context of beta-Lactam Resistance

• Resistance to other, unrelated, antimicrobials, except notably the fluoroquinolones, was strongly associated with beta-lactam resistance. beta-lactamase production was detected in 492 isolates of H. influenzae, an overall prevalence of 18.1% [22].
• Even though mutations in another gene(s) may be involved in beta-lactam resistance, these data indicate that mutations in the ftsI gene are the most important for development of resistance to beta-lactams in BLNAR strains [23].
• Detection of an IS21 insertion sequence in the mexR gene of Pseudomonas aeruginosa increasing beta-lactam resistance [24].
• The PBP 5 variants of 15 clinical isolates (including 8 resistant to vancomycin) with different levels of beta-lactam resistance were analyzed [12].
• Overexpression of the efflux pump alone contributes to the high level of beta-lactam resistance in the absence of beta-lactamase [17].

Analytical, diagnostic and therapeutic context of beta-Lactam Resistance

• The molecular mechanisms of beta-lactam resistance mediated by AmpC hyperproduction in natural strains of Pseudomonas aeruginosa were investigated in a collection of 10 isogenic, ceftazidime-susceptible and -resistant pairs of isolates, each sequentially recovered from a different intensive care unit patient treated with beta-lactams [25].

References