Leandro Reus Rodrigues Perez

Application of a feasible method for determination of biofilm antimicrobial susceptibility in staphylococci

Antunes ALS, Trentin DS, Bonfanti JW, Pinto CCF, Perez LRR, Macedo AJ, Barth AL. Application of a feasible method for determination of biofilm antimicrobial susceptibility in staphylococci. APMIS 2010; 118: 873–7.

Evaluation of urinalysis parameters to predict urinary-tract infection

We evaluated the performance of automated-flow cytometry, urinalysis dipsticks and microscopic urine sediment analysis as predictors of urinary tract infection. Urine cultures were used as a reference method for comparison. Six-hundred-seventy-five urine samples from hospitalized and not hospitalized patients attended at Hospital Mãe de Deus, Porto Alegre, in south Brazil, were included in the study. Among the individual measures analyzed, intense bacteriuria in the microscopic analysis of urinary sediment gave an accuracy of 92.9%. A combination between intense bacteriuria (microscopic analysis) and >20 leukocytes per microL of urine (flow cytometry) gave a higher accuracy (97.3%). We conclude that though it is laborious, microscopic urinalysis is a good analytical tool. Taken together with flow cytometry and dipsticks, we obtained a clinically-acceptable prediction of urinary-tract infection.

High vancomycin resistance among biofilms produced by Staphylococcus species isolated from central venous catheters

Biofilm production is an important mechanism that allows microbes to escape host defences and antimicrobial therapy. Vancomycin has been used largely for the treatment of methicillin-resistant staphylococcal infections. Here, we determined the minimal inhibitory concentration (MIC) and minimal biofilm eradication concentration (MBEC) for 82 Staphylococcus species isolated from central venous catheters (CVC). Our results showed that the 41 strong and moderate-biofilm-producing isolates presented a higher MBEC/MIC ratio for vancomycin than the 24 weak-biofilm-producing isolates, illustrating the importance of biofilm production ability and the difficulty in treating biofilm-related infections. The MBEC was significantly higher in moderate-biofilm-producing isolates than in weak-biofilm-producing isolates (p < 0.001) and in strong-biofilm-producing isolates than in weak-biofilm-producing isolates (p = 0.001). The correlation between the MIC and the MBEC was poor. Based on our results, we recommend that bacterial biofilms be suspected in all cases of CVC infection.

Evaluation of oxacillin and cefoxitin disks for detection of resistance in coagulase negative staphylococci

Coagulase-negative Staphylococcus spp. was considered nonpathogenic until the emergence of multiresistance and the demonstration of their participation as infectious agents. In Brazil, oxacillin resistance may be present in over 80% of isolates, and the Clinical and Laboratory Standards Institute standardized a disk-diffusion method to predict this resistance in Staphylococcus. The aim of this study was to evaluate the variability among commercial disks of oxacillin (1 microg) and cefoxitin (30 microg) widely used in clinical laboratories of microbiology, compared with mecA gene and minimum inhibitory concentration (MIC) of oxacillin. The use of oxacillin and cefoxitin disks simultaneously allowed the detection of important differences, particularly, in less frequent species such as S. cohnii, S. haemolyticus, S. saprophyticus, and S. sciuri. Disks of cefoxitin of the brand 2 displayed good correlation with the mecA gene (98.7%) and oxacillin MIC (97.8%), while major discrepancies were observed using disks of brand 1. One of the critical points in the diffusion disk test is the quality of the disks: the use of better quality disks associated with molecular methods lead to better results to define the best antibiotic therapy.

When the resistance gets clingy: Pseudomonas aeruginosa harboring metallo-β-lactamase gene shows high ability to produce biofilm

The ability to produce biofilm and the presence of metallo-β-lactamase (MBL) among Pseudomonas aeruginosa isolates were evaluated. A total of 91 isolates were recovered from sputa of patients with (CF, n = 44) and without (non-CF, n = 47) cystic fibrosis diagnosis. Seventy-nine (86.8%; 95% CI 78.3–92.3%) were biofilm producers. Interestingly, all isolates harboring MBL showed ability (most strong or moderate) to produce biofilm in vitro. We alert to an “overlapping of mechanisms” that together represent an even greater challenge for the treatment of pulmonary infections by P. aeruginosa.

Feasible identification of Staphylococcus epidermidis using desferrioxamine and fosfomycin disks

Coagulase‐negative Staphylococcus spp. (CoNS) have emerged as predominant pathogens in hospital‐acquired infections, as well as reservoirs of antimicrobial resistance, increasing the necessity of developing reliable methods for identification of the most frequent species. The aim of this study was to propose a simplified method for identification of Staphylococcus epidermidis. A total of 490 isolates of CoNS were identified by Bannermans method. Taking into account distinct approaches for identification of S. epidermidis, among CoNS, we proposed the use of only two disks: desferrioxamine for the initial trial, and fosfomycin to match the final identification. Of the 320 isolates susceptible to desferrioxamine, Bannermans method identified 238 S. epidermidis and 73 S. hominis, while we achieved identification of 239 S. epidermidis and 76 S. hominis. Compared to Bannermans method, the method proposed here obtained a sensitivity of 99.5%, and had a positive predictor value of 99.2%. We also used a genotypic method for identification of S. epidermidis by polymerase chain reaction (PCR) targeting the tuf gene. In conclusion, the method proposed here has proved to be useful for the identification of S. epidermidis, the most frequent species of CoNS isolated from blood cultures in clinical microbiology laboratories.

Prevalência de Cryptococcus neoformans nos pombos urbanos da cidade de Porto Alegre, Rio Grande do Sul

Cryptococcus neoformans, levedura encapsulada, e o agente etiologico da criptococose em humanos e animais. A variedade neoformans, encontrada em fontes ambientais, incluindo fezes de pombos, e importante causa de mortalidade em individuos imunodeprimidos em todo o mundo. Contudo, ainda nao ha estudos sobre sua ecologia na cidade de Porto Alegre, onde se tem registro da ocorrencia de casos humanos dessa micose. Para pesquisar fontes saprofiticas de C. neoformans na cidade de Porto Alegre, foram coletadas 88 amostras de excretas de pombos em distintas pracas da cidade. Suspensoes das amostras em salina esteril foram semeadas em placas com meio agar Sabouraud e incubadas em estufa a temperaturas entre 29 e 30,5°C. Apos cinco dias, colonias mucoides foram subcultivadas para identificacao atraves de provas morfofisiologicas. O fungo C. neoformans foi isolado em 88 (100%) das amostras avaliadas, confirmando sua ocorrencia nos pombos que habitam as pracas da cidade.

Emergence of Infections due to a Polymyxin B-Resistant KPC-2-Producing Klebsiella pneumoniae in Critically Ill Patients: What Is the Role of a Previous Colonization?

Infection Control & Hospital Epidemiology / Volume 37 / Issue 02 / February 2016, pp 240 241 DOI: 10.1017/ice.2015.294, Published online: 07 January 2016 Link to this article: http://journals.cambridge.org/abstract_S0899823X15002949 How to cite this article: Leandro Reus Rodrigues Perez and Cícero Gomes Dias (2016). Emergence of Infections due to a Polymyxin B–Resistant KPC-2-Producing Klebsiella pneumoniae in Critically Ill Patients: What Is the Role of a Previous Colonization?. Infection Control & Hospital Epidemiology, 37, pp 240-241 doi:10.1017/ice.2015.294 Request Permissions : Click here

Clonal types and antimicrobial resistance profiles of methicillin-resistant Staphylococcus aureus isolates from hospitals in south Brazil

In the present study were evaluated the DNA macrorestriction profile and SCCmec types for nine multi-resistant MRSA selected. Also antimicrobial susceptibility testing by disk diffusion method was evaluated for 68 MRSA isolates against 12 antimicrobial agents. The isolates were recovered from blood culture collected from hospitalized patients in three hospitals of Porto Alegre, Brazil. PFGE and PCR for mecA and SCCmec I, II, III, IV types genes were done on selected nine isolates with susceptibility only to vancomycin, teicoplanin and linezolid. Two clone profiles, with five subtypes, were demonstrated among multi-resistant MRSA analyzed. Eight isolates showed harbor SCCmec type III and one isolate was not typeable. The knowledge of SCCmec type, clone and antimicrobial profiles among S. aureus is essential mainly to prevention and control of dissemination of the antimicrobial resistance.

Evaluation of polymyxin susceptibility profile among KPC‐producing Klebsiella pneumoniae using Etest and MicroScan WalkAway automated system

Determination of polymyxin susceptibility profile is important to monitor resistance rates and for implementing control measures for polymyxin‐resistant carbapenem‐resistant Enterobacteriaceae. Some laboratorial methods have been used to determine the polymyxin susceptibility profile. However, the performance of MicroScan WalkAway has been poorly reported for KPC‐producing Klebsiella pneumoniae, so far. To evaluate two different methods, Etest and the MicroScan automated system, in determining minimal inhibitory concentration (MIC) of polymyxin among KPC‐producing K. pneumoniae isolated from patients in two care units (ICUs) of a tertiary hospital in Porto Alegre, Southern Brazil. A total of 101 KPC‐Kb isolates were obtained from rectal swabs and clinical specimens (urine, blood, and endotracheal aspirate). Colistin and polymyxin B MICs were determined using MicroScan WalkAway automated system and Etest, respectively. Discrepant results were resolved by broth microdilution (BMD). MicroScan showed 88.1% of sensitivity for predicting polymyxin B resistance in KPC‐producing K. pneumoniae compared to the results obtained by Etest. All discrepant results were tested by BMD and these were concordant with results obtained by Etest. The MicroScan automated system does not seem to be very efficient for the screening of polymyxin‐resistant isolates once an inappropriate sensitivity is achieved. The results presented here show the need for confirmation of the susceptibility profile by use of a dilution method (Etest or BMD).