Staphylococcus aureus nasal colonization and susceptibility profile to antimicrobials in hemodialysis patients using a protocol of seven collections.

BACKGROUND: Patients colonized with Staphylococcus aureus in their nasal passages have a higher risk of acquiring infection, especially if they are immunocompromised or have comorbidities such as chronic renal failure undergoing hemodialysis (HD). OBJECTIVE: This study aimed to report the prevalence of nasal carriage of S. aureus among HD patients utilizing a seven-week sampling protocol and to assess the susceptibility of these isolates to various antimicrobial agents. METHODS: Over seven consecutive weeks, nasal swab samples were collected from 47 HD patients, resulting in a total of 329 samples. The microorganisms were identified using biochemical methods and subjected to antimicrobial susceptibility testing via disk diffusion and microdilution techniques. RESULTS: Out of all the patients analyzed, 25 individuals (53.19%) were found to be colonized by S. aureus, with 21 of them displaying intermittent colonization. Additionally, 38% showed positive results for S. aureus in only the 6th or 7th week of sampling. Within the 58 isolates, 17.2% (n=10) exhibited methicillin (oxacillin)-resistance and 25.86% (n=15) displayed elevated vancomycin MIC values (2 µg/ml). Based on the results, daptomycin and gentamicin were found to be effective treatment options. However, 31% of the isolates (n=18) exhibited a MIC of 1 µg/ml for daptomycin. CONCLUSION: Over half of the patients were colonized by S. aureus, but mostly on an intermittent basis. The identification of oxacillin resistance and high vancomycin and daptomycin MICs serve as warnings for possible future complications in managing bacteremia caused by S. aureus in these patients.

Effects of Vancomycin Subtherapeutic Concentration on Staphylococcus aureus Isolated from Hemodialysis Patients with Low Serum Trough Concentrations.

Blood bactericidal activity and antimicrobial therapy are crucial against catheter-related infection in patients undergoing hemodialysis (HD). It is well-known that catheters colonized by biofilm-producing bacteria are a risk factor for bacteremia in HD-patients. Methicillin-resistant S. aureus bacteremia in HD-patients justify the use of vancomycin as empiric therapy. The recommended vancomycin target for therapeutic efficacy is a minimum serum concentration of 10 µg mL-1 to avoid resistance. However, subtherapeutic concentrations of vancomycin have frequently occurred in HD-patients. Thus, we aim to investigate the effect of subtherapeutic vancomycin concentration on S. aureus growth, susceptibility to antimicrobials, resistance to whole blood activity, and biofilm formation. Seventeen S. aureus strains isolated from bacteremia in HD-patients and two reference strains were exposed to a vancomycin-gradient (0-10 µg mL-1) for five consecutive days to mimic the dosing interval of vancomycin in HD-patients. After that, we observed the following: no effect on growth curve; decreased susceptibility to vancomycin and daptomycin; increased S. aureus survival to whole blood bactericidal action; and a strain-dependent biofilm production after drug exposure. In conclusion, our findings suggest that the subtherapeutic concentration of vancomycin decrease S. aureus susceptibility to vancomycin and daptomycin and increases its survival to whole blood bactericidal action.

Effect of antimicrobials on Stenotrophomonas maltophilia biofilm.

Aim: To evaluate the activity of five antimicrobials against young and mature Stenotrophomonas maltophilia biofilms. Materials & methods: Nineteen clinical strains from hemoculture of hemodialysis patients were tested for biofilm kinetics, MIC and minimum biofilm inhibitory concentration (MBIC) in young and mature biofilms. Results: All strains were moderate biofilm producers. MIC showed total susceptibility to levofloxacin and trimethoprim-sulfamethoxazole and partial resistance to ceftazidime (63.2%) and gentamicin (21%). Young and mature biofilms showed the lowest MBIC/MIC ratio for gentamicin, chloramphenicol and levofloxacin, respectively. The highest MBIC/MIC was for trimethoprim-sulfamethoxazole (young) and ceftazidime (mature). Conclusion: Gentamicin displayed surprising activity against S. maltophilia biofilms. Chloramphenicol was indicated as a good option against young S. maltophilia biofilms, and trimethoprim-sulfamethoxazole showed limited antibiofilm activity.

Isolation and identification of Candida species in patients with orogastric cancer: susceptibility to antifungal drugs, attributes of virulence in vitro and immune response phenotype.

BACKGROUND: Because of the inherent immunosuppression of cancer patients opportunistic infections by Candida spp, occur frequently. This study aimed to identify Candida species in the oral mucosa of 59 patients with orogastric cancer (OGC) and to analyze the immunological phenotype of these patients. METHODS: The yeasts were identified by MALDI-TOF mass spectrometry (MS). For all isolates, we performed phospholipases and proteinases assays, in vitro adherence to buccal epithelial cells (BEC), minimum inhibitory concentration of antifungal drugs and determined the cytokine profile by Cytometric Bead Array flow citometry assay. RESULTS: C. albicans was the most prevalent species in OGC patients (51.6 %) and control group (66.7 %). Candida spp. strains isolated from OGC patients exhibited better adherence to BEC (p = 0.05) than did the control group. Phospholipases production by Candida strains from OGC patients was lower (51.6 %) than in the control group (61.9 %). Proteinases were detected in 41.9 % and 4.8 % of the yeasts from OGC patients and control group, respectively. Significant differences were found in the serum of OGC patients compared to the control group for IL-2, IL-10, TNF-α, IFN-γ and IL-17. CONCLUSIONS: The results of this work suggest increased virulence of yeasts isolated from OGC patients and, that this may interfere with the immune phenotype.

Sub-Inhibitory Concentration of Piperacillin-Tazobactam May be Related to Virulence Properties of Filamentous Escherichia coli.

Sub-inhibitory concentrations of antibiotics are always generated as a consequence of antimicrobial therapy and the effects of such residual products in bacterial morphology are well documented, especially the filamentation generated by beta-lactams. The aim of this study was to investigate some morphological and pathological aspects (virulence factors) of Escherichia coli cultivated under half-minimum inhibitory concentration (1.0 µg/mL) of piperacillin-tazobactam (PTZ sub-MIC). PTZ sub-MIC promoted noticeable changes in the bacterial cells which reach the peak of morphological alterations (filamentation) and complexity at 16 h of antimicrobial exposure. Thereafter the filamentous cells and a control one, not treated with PTZ, were comparatively tested for growth curve; biochemical profile; oxidative stress tolerance; biofilm production and cell hydrophobicity; motility and pathogenicity in vivo. PTZ sub-MIC attenuated the E. coli growth rate, but without changes in carbohydrate fermentation or in traditional biochemical tests. Overall, the treatment of E. coli with sub-MIC of PTZ generated filamentous forms which were accompanied by the inhibition of virulence factors such as the oxidative stress response, biofilm formation, cell surface hydrophobicity, and motility. These results are consistent with the reduced pathogenicity observed for the filamentous E. coli in the murine model of intra-abdominal infection. In other words, the treatment of E. coli with sub-MIC of PTZ suggests a decrease in their virulence.

Proteomic changes in Bacteroides fragilis exposed to subinhibitory concentration of piperacillin/tazobactam.

Bacteroides fragilis is the anaerobe most frequently isolated from clinical specimens and piperacillin/tazobactam is among the drugs that can be used to treat polymicrobial infections in which this bacteria is often involved. During antibiotic therapy, inhibitory concentrations of antibiotics are always followed by subinhibitory concentrations which can generate phenotypic changes in bacteria. So, in this study we aimed to evaluate changes in the proteomic profile of B. fragilis grown in a sub-MIC of PTZ, using 2-D electrophoresis followed by matrix-assisted laser desorption/ionization time-of-flight/time of-flight. Analysis of the 2-DE gels showed 18 spots with significantly different volume percentages between experimental conditions and 12 were successfully identified by MS/MS. Two proteins with decreased abundance in sub-MIC condition were involved in the glycolysis (glyceraldehyde-3-phosphate dehydrogenase and triose phosphate isomerase), others two involved in amino acid metabolism (Oxoacyl-(acyl-carrier protein) synthase II and dihydrodipicolinate reductase), and finally, one protein involved in fatty acid metabolism (UDP-N-acetylglucosamine acyltransferase). Among the proteins with increased abundance, we founded three ATP synthase (alpha, beta, and alpha type V), which could be involved in antibiotic bacterial resistance by efflux pump, one protein involved in glycolysis (enolase), and one involved in protein degradation (aminoacyl-histidine dipeptidase). In conclusion, our data show overall changes in the proteome of B. fragilis conducted by sub-MIC of PTZ, whose consequences on bacterial physiology deserve further investigation.

Proteomic analysis of Escherichia coli with experimentally induced resistance to piperacillin/tazobactam.

The worldwide emergence of antibiotic-resistant bacteria poses a serious threat to human health. In addition to the difficulties in controlling infectious diseases, the phenotype of resistance can generate metabolic changes which, in turn, can interfere with host-pathogen interactions. The aim of the present study was to identify changes in the subproteome of a laboratory-derived piperacillin/tazobactam-resistant strain of Escherichia coli (minimal inhibitory concentration [MIC] = 128 mg/L) as compared with its susceptible wild-type strain E. coli ATCC 25922 (MIC = 2 mg/L) using 2-D fluorescence difference gel electrophoresis (2D-DIGE) followed by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF MS). In the resistant strain, a total of 12 protein species were increased in abundance relative to the wild-type strain, including those related to bacterial virulence, antibiotic resistance and DNA protection during stress. Fourteen proteins were increased in abundance in the wild-type strain compared to the resistant strain, including those involved in glycolysis, protein biosynthesis, pentose-phosphate shunt, amino acid transport, cell division and oxidative stress response. In conclusion, our data show overall changes in the subproteome of the piperacillin/tazobactam-resistant strain, reporting for the first time the potential role of a multidrug efflux pump system in E. coli resistance to piperacillin/tazobactam.