Antimicrobial susceptibility of non-fermenting Gram-negative pathogens isolated from cystic fibrosis patients

Abstract

Non-fermenting Gram negative bacteria are increasingly being cultured in respiratory samples from people with cystic fibrosis (CF). This study aimed to determine the susceptibility of clinical CF respiratory isolates from distinct geographical regions to a range of antimicrobials. A total of 286 isolates (106 Stenotrophomonas maltophilia, 100 Burkholderia spp., 59 Achromobacter spp., 12 Pandoraea spp. and 9 Ralstonia spp.) from The Netherlands, Northern Ireland, Spain, USA and Australia were tested. The MIC, MIC and susceptibility categorization were determined. Cotrimoxazole was the most active compound for all the microorganisms (MIC=0.12-4 mg/L, MIC=1-16 mg/L). For S. maltophilia, 47% and 62% of isolates were susceptible to cotrimoxazole according to CLSI and EUCAST breakpoints, respectively. Ceftazidime presented a lower level of susceptibility (35%, MIC=32 mg/L, MIC=256 mg/L). Tobramycin and colistin MIC were >128 mg/L and >16 mg/L, respectively. Regarding Burkholderia isolates, 72%, 56% and 44% were susceptible to cotrimoxazole, ceftazidime and meropenem, respectively. For both ceftazidime and meropenem, the MIC and MIC values were within the intermediate or resistant category. The most active antibiotics for A. xylosoxidans were cotrimoxazole (MIC=2, MIC=8 mg/L) and imipenem (MIC=2, MIC=8 mg/L). Cotrimoxazole, imipenem, and ciprofloxacin were active against the 12 Pandoraea species (MIC= 0.12-4 mg/L, MIC= 1-8 mg/L). Ciprofloxacin (MIC=4 mg/L) and cotrimoxazole (MIC=1 mg/L) were the only active antibiotics for Ralstonia spp. There were no statistically significant differences in susceptibility rates between countries. Non-fermenting Gram-negative bacteria other than P. aeruginosa are potential pathogens in CF and cotrimoxazole has demonstrated to be the most active compound against them.

In Vitro Synergism of Colistin and N-acetylcysteine against Stenotrophomonas maltophilia

“…The remaining 5 isolates showed colistin MIC <2 µg/mL (MIC range 0.125–1 µg/mL) and were therefore categorized as “colistin-susceptible” (Table 1). Overall, colistin susceptibility patterns of strains included in this study were consistent with those recently reported in other studies on S. maltophilia antibiotic susceptibility [8,23].…”

“…Despite the precise clinical relevance of S. maltophilia in CF remains undetermined [3,4], chronic pulmonary colonization by S. maltophilia has been recently associated with an increased risk of pulmonary exacerbations requiring intravenous antibiotics, lung transplantation, and death [5,6,7]. Due to intrinsic and acquired multidrug resistance mechanisms and the propensity to grow as biofilm, S. maltophilia infections are difficult-to-treat and the therapeutic options are very limited [1,5,8,9,10,11]. Clinical breakpoints for the interpretation of susceptibility testing are available only for trimethoprim-sulfamethoxazole (SXT) (i.e., the first-line treatment option) and few other compounds, namely levofloxacin, some beta-lactams (i.e., ticarcillin-clavulanate and ceftazidime), minocycline, and chloramphenicol [12,13].…”

Clonal Diversity, Biofilm Formation, and Antimicrobial Resistance among Stenotrophomonas maltophilia Strains from Cystic Fibrosis and Non-Cystic Fibrosis Patients

“…Considering available clinical breakpoints, our results confirmed SXT is the most active compound against all the strains tested. The overall resistance to SXT was 18.7%, although its activity was significantly higher in non-CF than CF strains (96.3% versus 75%, respectively), in agreement with previous findings [37,38].…”

“…Recently, a systematic review reported that fluoroquinolones show comparable effects on the mortality of S. maltophilia infection compared with trimethoprim-sulfamethoxazole, supporting the use of fluoroquinolones in clinical S. maltophilia infections [39], although high rates of resistance are also increasingly being reported. In the current study, the newer fluoroquinolone levofloxacin showed better activity against S. maltophilia than ciprofloxacin (susceptibility rates: 77.9% versus 18.8%, respectively), confirming previous studies [9,37,38].…”

Pandoraea sp infection in a lung transplant patient and the critical role of MALDI-TOF in accurate bacterial identification

“…Isolates of the Pandoraea sp genus were shown to present variable susceptibility profiles to beta-lactams, being frequently resistant to meropenem and susceptible to imipenem. Among other classes, tetracycline and TMP-SMX were shown to have efficacy on a series of clinical isolates, including multi-drug resistant strains (4, 15,16).…”