Study ofPseudomonas aeruginosa serotype O12 isolates with a common antibiotic susceptibility pattern

Abstract

A multicentre European study of Pseudomonas aeruginosa serotype O12 isolates with a common antibiotic resistance pattern was conducted. Resistance to beta-lactams and aminoglycosides was observed in 24 of the 25 isolates, as often reported in Europe, and all 25 isolates were significantly more susceptible to fosfomycin than 189 isolates of other serotypes (72% vs. 13.2%). The mutational frequency of serotype O12 was similar to that of other serotypes and thus could not explain the susceptibility to fosfomycin. As a number of epidemiological studies using various methods, especially ribotyping with EcoRI, have shown that most strains are similar, it has been suggested that a single strain of this serotype is widespread. However, in this study ribotyping with EcoRI and PvuII distinguished seven clones among 24 ticarcillin resistant serotype O12 isolates, although one ribotype predominated (67%). Thus the hypothesis of spread of one clone across Europe cannot explain the common resistance phenotype observed in different clones of serotype O12. Resistance of beta-lactams and aminoglycosides might be explained by greater receptiveness for transposable resistance mechanisms, and susceptibility to fosfomycin by increased permeability of the outer membrane.

Fosfomycin for the treatment of infections caused by multidrug-resistant non-fermenting Gram-negative bacilli: a systematic review of microbiological, animal and clinical studies

“…Nineteen studies in total provided data on the susceptibility to fosfomycin of MDR P. aeruginosa isolates [8][9][10][11][12][14][15][16][18][19][20][21][23][24][25][26][28][29][30]. Seven of these nineteen studies found that ≥90% of the isolates evaluated were susceptible to fosfomycin [10][11][12]19,21,23,29] and four additional studies found that 50-90% of the isolates were susceptible to fosfomycin [8,15,24,28].…”

“…Regarding the interpretative MIC breakpoints of susceptibility to fosfomycin used, eight studies used a susceptibility breakpoint of ≤64 mg/L [8,11,12,14,16,17,21,27], four studies used a breakpoint of ≤32 mg/L [23,24,28,29], one study used a breakpoint of ≤16 mg/L [18], whereas specific data were not reported in 10 studies [9,10,13,15,19,20,22,25,26,30]. The majority of the latter (six of ten) were performed in France [9,10,15,20,25,26].…”

“…The majority of the latter (six of ten) were performed in France [9,10,15,20,25,26]. In total, 1859 MDR non-fermenting Gram-negative bacilli M a n u s c r i p t were analysed, of which 1743 (93.8%) were P. aeruginosa isolates [8][9][10][11][12][14][15][16][18][19][20][21][23][24][25][26][28][29][30], 85 (4.6%) were A. baumannii [8,13,17,27] and 31 (1.7%) were Burkholderia spp. [22].…”

“…Fifteen of the twenty-three studies reported on the site of isolation of the isolates examined [9,10,12,13,15,[17][18][19][20][21]23,25,26,29,30]. Ten studies evaluated susceptibility to fosfomycin according to the disk diffusion method [9,15,16,21,[24][25][26][28][29][30] and three studies each according to the agar dilution method [8,12,20], the broth microdilution method [17,18,27] and Etest [13,14,22], whilst three studies did not state the method of determination of fosfomycin susceptibility [10,19,23]. In one study more than one test method was used to determine susceptibility to fosfomycin [11]; in this study, the Etest method was selected to evaluate fosfomycin susceptibility, as the Clinical and Laboratory Standards Institute (CLSI) does not recommend the relevant broth dilution methods [39].…”

“…Eleven studies included non-fermenting Gram-negative isolates originating from France [9,10,12,15,20,[23][24][25][26]28,29], three studies included isolates originating from Japan [11,17,18], two from Italy [19,30] and one each from Thailand [16], Taiwan [14], Greece [8], Spain [27], the UK [22], Germany [21] and Bulgaria [13]. Fifteen of the twenty-three studies reported on the site of isolation of the isolates examined [9,10,12,13,15,[17][18][19][20][21]23,25,26,29,30].…”