Carbapenem-resistant and cephalosporin-susceptible: a worrisome phenotype among Pseudomonas aeruginosa clinical isolates in Brazil

Abstract

The mechanisms involved in the uncommon resistance phenotype, carbapenem resistance and broad-spectrum cephalosporin susceptibility, were investigated in 25 Pseudomonas aeruginosa clinical isolates that exhibited this phenotype, which were recovered from three different hospitals located in São Paulo, Brazil. The antimicrobial susceptibility profile was determined by CLSI broth microdilution. β-lactamase-encoding genes were investigated by PCR followed by DNA sequencing. Carbapenem hydrolysis activity was investigated by spectrophotometer and MALDI-TOF assays. The mRNA transcription level of oprD was assessed by qRT-PCR and the outer membrane proteins profile was evaluated by SDS-PAGE. Genetic relationship among P. aeruginosa isolates was assessed by PFGE. Carbapenems hydrolysis was not detected by carbapenemase assay in the carbapenem-resistant and cephalosporin-susceptible P. aueruginosa clinical isolates. OprD decreased expression was observed in all P. aeruginosa isolates by qRT-PCR. The outer membrane protein profile by SDS-PAGE suggested a change in the expression of the 46kDa porin that could correspond to OprD porin. The isolates were clustered into 17 genotypes without predominance of a specific PFGE pattern. These results emphasize the involvement of multiple chromosomal mechanisms in carbapenem-resistance among clinical isolates of P. aeruginosa, alert for adaptation of P. aeruginosa clinical isolates under antimicrobial selective pressure and make aware of the emergence of an uncommon phenotype among P. aeruginosa clinical isolates.

Carbapenem-Resistant but Cephalosporin-Susceptible Pseudomonas aeruginosa in Urinary Tract Infections: Opportunity for Colistin Sparing

“…Although colistin resistance in P. aeruginosa is still relatively rare (especially in countries limiting the use of this agent), nevertheless, a steady increase in the resistance levels for colistin may be expected in the coming years [41]. Similar to the findings of other reports [14,18,19], resistance levels to other antibiotics were also pronounced, with~60% resistance to fluoroquinolones and gentamicin.…”

“…Metallo-β-lactamase production and AmpC β-lactamase hyperproduction showed a lower prevalence (18.5% and 3.9%, respectively) [15]. A study from Brazil, spanning the years 2012 and 2013, reported n = 25 individual P. aeruginosa isolates from all clinical sample types [18]. Most of these bacteria had reduced oprD gene expression levels, while AmpC hyperproduction, carbapenem hydrolysis (detected by the MALDI-TOF MS method) and efflux pump overexpression (RT-PCR) were not shown in these isolates.…”

“…This may point to the relevance of OprD porin mutation as a substantial mechanism of resistance solely for carbapenems [15]. Although there are only a few studies available, the proportion of strains with reduced OprD expression or lack of OprD was very high (100% [19]; 100% [30]; 93.85% [15]; >90% [29]; 78.26% [14], and 41.38% [18], respectively). The role of OprD mutation in carbapenem resistance has been highlighted in repeated exposure to carbapenems [14,15,43].…”

“…However, these enzymes are very diverse with variable spectra of activity and phenotypic expression levels [16,17]. Several studies have noted the occurrence of carbapenem-resistant but cephalosporin-susceptible (Car-R/Ceph-S) P. aerugonisa [14,18,19]. In these strains, the AmpC production is thought to be moderate or low, which would allow for the use of relevant cephalosporins, instead of other, more toxic agents with a disadvantageous side effect profile [20].…”

Performance of Rapidec Carba Np Test in Detection of Carbapenemase Producing Gram-Negative Bacteria.

“…Carbapenem susceptibility pattern showed that 49(81.6%) were Imipenem resistant, 46(76.7%) were Meropenem resistant and 50 (83.3% )were ertapenem resistant. Campanaet al (12) reported that a total of 131 Enterobacteriaceae strains were tested. Of those, 62 (47.33 %) strains were resistant to at least one antibiotic.…”