Evaluation of a Commercial Broth Microdilution Panel for Colistin Susceptibility Testing of Clinical Isolates of Escherichia coli and Klebsiella pneumoniae.

BACKGROUND: Colistin is among the last resort antibiotics for the treatment of infections caused by multidrug-resistant Gram-negative pathogens. Antimicrobial susceptibility testing of colistin is challenging due to its physicochemical properties. Broth microdilution (BMD) is the recommended method for colistin susceptibility testing. However BMD is not practical for clinical microbiology laboratories as manual preparation of BMD plates is time-consuming and labor intensive. Recently, some more user-friendly BMD products with commercial panels have become available. Our objective was to evaluate the performance of a commercial broth microdilution (BMD) product [Sensititre (Thermo Fisher Scientific)] for colistin MIC determination by comparison with reference BMD method using a collection of E. coli and K. pneumoniae isolates. METHODS: A total of 323 unique patient isolates (102 E. coli, 221 K. pneumoniae) were included in the study. Isolates were stored at -70°C and subcultured twice on sheep blood agar before testing. Colistin MICs of the isolates were determined using Sensititre (a premade BMD product with dried antibiotics) and an 'in-house prepared BMD panel prepared in accordance with CLSI guidelines' (reference method). MIC determination with Sensititre was performed according to manufacturer's instructions. The reference method was performed using untreated 96-well sterile polystyrene plates. Colistin MIC results were interpreted according to EUCAST breakpoints (susceptible, ≤ 2 mg/L; resistant, > 2 mg/L). RESULTS: Overall susceptibility rate of isolates to colistin by reference BMD was 75.9%. Overall categorical agreement (CA), essential agreement (EA), very major error (VME), and major error (ME) rates for Sensititre were 98.5%, 72.5%, 3.8%, and 0.8%, respectively. The CA and EA between Sensititre and reference BMD for the isolates with reference colistin MICs close to the susceptibility breakpoint (2 - 8 mg/L) was 94.2% and 48.1%, respectively. Sensititre yielded a VME rate of 15% and ME rate of 0%, respectively, for this subset of isolates. CONCLUSIONS: In conclusion, Sensititre showed high CA but low EA with reference BMD for entire collection of isolates. The VME rate was just slightly above 3% and ME rate was acceptable. The rates of CA and EA were decreased and the rate of VME was increased when a subset consisting of more challenging isolates was used.

A case of Raoultella ornithinolytica urinary tract infection in a pediatric patient.

Raoultella ornithinolytica is a Gram-negative, non-motile, encapsulated, biofilm producing, facultative aerobic bacillus and is found in natural environment. Human infections with R.ornithinolytica is rare in children with only five cases having been reported previously. The present case report describes an urinary tract infection caused by R. ornithinolytica that was identified by MALDI-TOF MS and successfully treated with antibiotic therapy in a 6.5-year-old female child.

A retrospective observational cohort study of the clinical epidemiology of bloodstream infections due to carbapenem-resistant Klebsiella pneumoniae in an OXA-48 endemic setting.

This study aimed to characterize the epidemiology and clinical outcomes of patients with bloodstream infections (BSIs) due to carbapenem-resistant Klebsiella pneumoniae (CRKP) in an OXA-48-predominant environment. This was a retrospective single-centre cohort study including all consecutive patients with CRKP BSIs treated between 1 January 2014 and 31 December 2018. Multivariate analysis, subgroup analysis and propensity-score-matched analysis were employed to analyse 30-day mortality as the primary outcome. Clinical cure at day 14 was also analysed for the whole cohort. In total, 124 patients with unique isolates met all the inclusion criteria. OXA-48 was the most common type of carbapenemase (85.5%). Inappropriate therapy was significantly associated with 30-day mortality [70.6% vs 39.7%, adjusted odds ratio (aOR) 4.65, 95% confidence interval (CI) 1.50-14.40, P=0.008] and 14-day clinical failure (78.5% vs 56.2%, aOR 3.14, 95% CI 1.09-9.02, P=0.033) in multivariate analyses. Among those treated appropriately, the 30-day mortality rates were similar in monotherapy and combination therapy arms (OR 2.85, 95% CI 0.68-11.95, P=0.15). INCREMENT CPE mortality score (aOR 1.16, 95% CI 1.01-1.33, P=0.029), sepsis at BSI onset (aOR 2.90, 95% CI 1.02-8.27, P=0.046), and inappropriate therapy (aOR 4.65, 95% CI 1.50-14.40, P=0.008) were identified as independent risk factors for 30-day mortality. Colistin resistance in CRKP had no significant impact on 30-day mortality. These results were also confirmed in all propensity-score-matched analyses and sensitivity analyses. Appropriate regimens were associated with better clinical outcomes than inappropriate therapies for BSIs with CRKP predominantly possessing OXA-48.

Comparison of Conventional Methods, Automated Systems, and DNA Sequence Analysis Methods in the Identification of Corynebacterium afermentans and Corynebacterium mucifaciens Bacteria Isolated from Blood and Catheter Culture Samples.

The aim of this study is to compare different methods due to the difficulties in identifying coryneform bacteria to species level and to determine antibiotic resistance profiles. Isolates identified as Turicella otitidis (n:45) by VITEK 2 Compact and Corynebacterium mucifaciens (n:1) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), isolated from blood and catheter cultures between 2015 and 2017 were included in the study. For identification of the isolates, conventional tests and 16S rDNA sequence analysis were performed. Antibiotic susceptibilities of the isolates were determined by Etest. The isolates identified as T. otitidis with VITEK 2 Compact could not be identified by MALDI-TOF MS and described as C. mucifaciens/Corynebacterium afermentans spp. by 16S rDNA sequence analysis. One isolate identified as C. mucifaciens by MALDI-TOF MS could not be identified with VITEK 2 Compact and described as C. mucifaciens by 16S rDNA sequence analysis and conventional methods. All isolates (n:45) described as C. mucifaciens/C. afermentans spp. by 16S rDNA sequence analysis were identified as C. afermentans subsp. afermentans with conventional methods. All 45 isolates identified as C. afermentans subsp. afermentans were resistant to penicillin, erythromycin, and clindamycin and were susceptible to vancomycin and daptomycin, whereas 31 (69%) were resistant to trimethoprim-sulfamethoxazole (TMP-SXT). The isolate identified as C. mucifaciens was susceptible to penicillin, vancomycin, daptomycin, and TMP-SXT; it was resistant to erythromycin and clindamycin. In this study, we reported 45 C. afermentans isolates misidentified as T. otitidis in routine laboratory processes. To our knowledge, this is the first study to include the highest number of C. afermentans blood isolates.

Stenotrophomonas maltophilia bacteremia in children - A 10-year analysis. / Bacteriemia por Stenotrophomonas maltophilia en niños: análisis de 10 años.

Stenotrophomonas maltophilia is a multidrug-resistant, Gramnegative, and biofilm-forming pathogen. Information is limited concerning S. maltophilia bacteremia in children. Clinical data and microbiological test results collected in a tertiary children's hospital over a ten-year period were reviewed. Children 0-18 years old who had positive clinical specimen, blood and/or catheter cultures were included. We identified 20 S. maltophilia isolates from 12 pediatric patients with confirmed infections. The median age was 28 months (range: 3.1-187.3). The rate of previous use of antimicrobial therapy was 83 %. The median antibiotic number was 3 (range: 0-7) within 30 days prior to onset of S. maltophilia bacteremia. Catheter related infection was the main infectious source (66.6 %). The mortality rate was 33.3 %. The death of two non-survivors was associated with pneumonia. S. maltophilia should be considered a breakthrough agent for bacteremia in children with underlying disease exposed to broad-spectrum antibiotics during long-term hospitalization.

Stenotrophomonas maltophilia es un microorganismo gramnegativo, multirresistente. La información sobre la bacteriemia por S. maltophilia en niños es limitada. Se revisaron los datos de 10 años de un hospital de niños de alta complejidad. Se incluyó a niños de 0 a 18 años con hemocultivos o cultivos del catéter positivos. Se identificaron 20 cepas de S. maltophilia en 12 niños con infección confirmada, cuya mediana de edad fue 28 meses (intervalo: 3,1-187,3). El índice de antibioticoterapia previa fue 83 %, con una mediana de tres antibióticos (intervalo: 0­7) en los 30 días previos a la bacteriemia por S. maltophilia. La infección relacionada con el catéter fue la principal fuente de infección (8/12). La mortalidad fue de 4/12; y en dos casos, estuvo asociada con neumonía. S. maltophilia puede considerarse un agente muy invasivo productor de bacteriemia en niños con enfermedad preexistente expuestos a antibióticos durante una hospitalización prolongada.

Streptococcus mitis/oralis Causing Blood Stream Infections in Pediatric Patients.

Viridans streptococci are still under investigation concerning epidemiology, pathogenesis and clinical presentations. We aimed to investigate the clinical presentations and outcomes of pediatric patients infected with Streptococcus mitis/oralis. Based on the accumulation of bloodstream infections (BSI) caused by S. mitis/oralis in 4 patients in our Hematology and Bone Marrow Transplantation Department at a particular time, a review of the medical and microbiological records of pediatric patients with positive blood cultures for S. mitis/oralis in the entire hospital was performed. In addition, a retrospective case-control study was conducted. Pulsed-field gel electrophoresis of S. mitis/oralis in 4 patients displayed unrelatedness of the strains. A total of 53 BSI (42 BSI and 11 catheter-related BSI) were analyzed. Thirty-four percent of patients with BSI caused by S. mitis/oralis had febrile neutropenia. Clinical and microbiological outcomes were favorable and infection-related mortality was not observed. Although not significant, previous antibiotic use and trimethoprim-sulfamethoxazole prophylaxis were more common in the case group. S. mitis/oralis seems likely an important agent in bacteremic children who are particularly neutropenic because of the underlying hematologic and oncologic diseases. Prompt management of infections with appropriate antimicrobials, regarding antibiotic susceptibilities of organisms, may facilitate favorable outcomes.

A comparison of blood stream infections with extended spectrum beta-lactamase-producing and non-producing Klebsiella pneumoniae in pediatric patients.

BACKGROUND: Rapid development and global spread of multidrug resistant Klebsiella pneumonia (K. pneumoniae) as a major cause of nosocomial infections is really remarkable. The aim of this study was to explore risk factors for health care associated blood stream infections (BSI) caused by ESBL-producing K. pneumoniae in children and analyze clinical outcomes. METHODS: A retrospective review of patients younger than 18 years-old with blood stream infection caused by K. pneumoniae was performed. Patients with ESBL-producing K. pneumoniae isolates were compared with ESBL-non-producing isolates in terms of risk factors, outcome and mortality. RESULTS: Among 111 K. pneumoniae isolates 62% (n = 69) were ESBL -producing K. pneumoniae. The median total length of hospitalization and median length of stay in hospital before infection was significantly higher in patients with ESBL-producing isolates than ESBL-non-producing. Use of combined antimicrobial treatment was significantly different between ESBL-producing and ESBL-non-producing groups, 75.4% and 24.6%, respectively (p = 0.001). Previous aminoglycoside use was higher in cases with ESBL -producing isolates (p = 0.001). Logistic regression analysis showed a significant correlation between mortality and use of combined antibiotics (OR 4.22; p = 0.01). CONCLUSION: ESBL production in K. pneumoniae isolates has a significant impact on clinical course of BSIs. Total length of hospitalization, length of hospital stay before infection, prior combined antibiotic use and use of aminoglycosides were significant risk factors for development of ESBL-producing K. pneumoniae related BSI.

Current epidemiology of resistance among Gram-negative bacilli in paediatric patients in Turkey.

OBJECTIVES: The increasing incidence of infections caused by drug-resistant Gram-negative organisms has led to a re-emergence worldwide. This study attempted to investigate the changes in resistance of Gram-negative bacteria to different classes of antibiotics and the treatment options for invasive infections. METHODS: A retrospective study was performed between January 2012 and January 2017 in a Turkish tertiary care university hospital. A total of 302 patients with Gram-negative bacteraemia (n=274; 90.7%) or meningitis (n=28; 9.3%) were identified and their demographic, clinical and microbiological features were evaluated. RESULTS: A total of 302 patients with Gram-negative bacterial infection (bacteraemia or meningitis) were investigated. Klebsiella spp. was the most frequent causative agent (n=119; 39.4%), followed by Escherichia coli (n=67; 22.2%), Acinetobacter spp. (n=42; 13.9%), Pseudomonas spp. (n=41; 13.6%) and Enterobacter spp. (n=33; 10.9%). In total, 115 isolates (38.1%) were multidrug-resistant (MDR), 63 (20.9%) were extensively drug-resistant (XDR) and 6 (2.0%) were pandrug-resistant (PDR). Over the years, peak antibiotic resistance occurred in 2013, with an increase in the following years. CONCLUSIONS: These data indicate that the resistance pattern of Gram-negative bacteria may change over the years in hospital settings. Therefore, active surveillance of the resistance patterns of micro-organisms is necessary for better management of infections caused by highly resistant bacteria.

Bacteriemia por Stenotrophomonas maltophilia en niños: análisis de 10 años / Stenotrophomonas maltophilia bacteremia in children - A 10-year analysis

Stenotrophomonas maltophilia es un microorganismo gramnegativo, multirresistente. La información sobre la bacteriemia por S. maltophilia en niños es limitada. Se revisaron los datos de 10 años de un hospital de niños de alta complejidad. Se incluyó a niños de 0 a 18 años con hemocultivos o cultivos del catéter positivos. Se identificaron 20 cepas de S. maltophilia en 12 niños con infección confirmada, cuya mediana de edad fue 28 meses (intervalo: 3,1-187,3). El índice de antibioticoterapia previa fue 83 %, con una mediana de tres antibióticos (intervalo: 0­7) en los 30 días previos a la bacteriemia por S. maltophilia. La infección relacionada con el catéter fue la principal fuente de infección (8/12). La mortalidad fue de 4/12; y en dos casos, estuvo asociada con neumonía. S. maltophilia puede considerarse un agente muy invasivo productor de bacteriemia en niños con enfermedad preexistente expuestos a antibióticos durante una hospitalización prolongada.

Stenotrophomonas maltophilia is a multidrug-resistant, Gram-negative, and biofilm-forming pathogen. Information is limited concerning S. maltophilia bacteremia in children. Clinical data and microbiological test results collected in a tertiary children's hospital over a ten-year period were reviewed. Children 0­18 years old who had positive clinical specimen, blood and/or catheter cultures were included. We identified 20 S. maltophiliaisolates from 12 pediatric patients with confirmed infections. The median age was 28 months (range: 3.1-187.3). The rate of previous use of antimicrobial therapy was 83 %. The median antibiotic number was 3 (range: 0­7) within 30 days prior to onset of S. maltophilia bacteremia. Catheter related infection was the main infectious source (66.6 %). The mortality rate was 33.3 %. The death of two non-survivors was associated with pneumonia. S. maltophilia should be considered a breakthrough agent for bacteremia in children with underlying disease exposed to broad-spectrum antibiotics during long-term hospitalization