Identification of clinically relevant Corynebacterium spp., Arcanobacterium haemolyticum, and Rhodococcus equi by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

The identification of 83 Corynebacterium, 13 Arcanobacterium haemolyticum, and 10 Rhodococcus equi strains by conventional methods (API Coryne complemented with 16S rRNA gene sequence analysis) was compared with matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry identification. The correlation between API and MALDI-TOF results was 89%. MALDI-TOF is a rapid and accurate system for identification of the above-mentioned microorganisms.

Detection of Aspergillus galactomannan by enzyme immunoabsorbent assay in recipients of allogeneic hematopoietic stem cell transplantation: a prospective study.

BACKGROUND: Invasive aspergillosis (IA) has become the leading infectious cause of death after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This is partially because of the lack of a sensitive, specific, and noninvasive diagnostic test. New diagnostic tests for IA, such as the detection of Aspergillus galactomannan antigen (AGA) by sandwich enzyme-linked immunoabsorbent assay (ELISA), have recently been described. This study validates the usefulness of this diagnostic tool in the allo-HSCT setting. METHODS: From January 1999 to January 2001, all consecutive adult patients undergoing allo-HSCT were prospectively studied with a galactomannan antigenemia assay (ELISA test) twice weekly from admission until death or discharge, and weekly afterward if the patient received immunosuppressive therapy. Proven, probable, and possible IA were defined according to the European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria. RESULTS: During the 2 years of study, 74 patients underwent an allo-HSCT. A total of 832 serum samples were collected. According to the European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria, it was ascertained that 66 patients did not fulfill any criteria of IA, 2 patients were classified with possible IA, 5 patients were classified with probable IA, and 1 patient was classified with proven IA. Fourteen samples were positive for AGA, all from patients with IA. The sensitivity and specificity of the test were 75% and 100%, respectively. The positive predictive and negative predictive values were 100% and 97%, respectively. CONCLUSIONS: In this study, AGA detection was clearly related to IA. Although the ELISA test did not have any role in the anticipation of the diagnosis, it clarifies the diagnosis of IA in allo-HSCT.

In vitro effect of three-drug combinations of antituberculous agents against multidrug-resistant Mycobacterium tuberculosis isolates.

Multidrug resistance has become a problem in the management of tuberculosis, leading to an urgent need for research related to new regimens including the currently available drugs. The objectives of this study were: (i) to study the effect of the following second-choice three-drug combinations against multidrug-resistant (MDR) and drug-susceptible clinical isolates (levofloxacin, linezolid and ethambutol; levofloxacin, amikacin and ethambutol; and levofloxacin, linezolid and amikacin); and (ii) to compare the effect of these combinations with an isoniazid, rifampicin and ethambutol combination against drug-susceptible clinical isolates. A total of 9 MDR clinical and 12 drug-susceptible isolates (11 clinical isolates and the H37Rv reference strain) were studied using an adaptation of the chequerboard assay. The fractional inhibitory concentration index (FICI) was calculated as follows: FICI=FIC(A)+FIC(B)+FIC(C)=A/MIC(A)+B/MIC(B)+C/MIC(C), where A, B and C are the minimum inhibitory concentrations (MICs) of each antibiotic in combination and MIC(A), MIC(B) and MIC(C) are the individual MICs. The FICI was interpreted as synergism when the value was <0.75. The FICI of all the combinations ranged from 1.5 to 3, showing indifferent activity. No differences were found between MDR and drug-susceptible isolates, or between the second-choice combinations and the fourth combination against drug-susceptible isolates. In conclusion, the second-choice drugs are equally effective as the combination of isoniazid, rifampicin and ethambutol.

Prevalence of dihydropteroate synthase genotypes before and after the introduction of combined antiretroviral therapy and their influence on the outcome of Pneumocystis pneumonia in HIV-1-infected patients.

The objective of this study was to determine whether the prevalence of Pneumocystis jirovecii dihydropteroate synthase (DHPS) gene mutations has changed since the introduction of combined antiretroviral therapy (cART) and whether the mutations are associated with poor outcome in Spanish HIV-1-infected patients with Pneumocystis pneumonia (PcP). We studied 167 PcP episodes in HIV-1-infected patients diagnosed during the pre-cART (1989-1995) and cART (2001-2004) periods. Molecular genotyping of DHPS was successfully performed in 98 patients (43 pre-cART and 55 cART). Seventeen patients (17/98, 17%; 95% confidence interval [CI], 10-25%) had mutations in the DHPS gene: 14 patients (14/43, 33%; 95% CI, 19-49%) from the pre-cART period and 3 patients (3/55, 5.5%; 95% CI, 1.3-16%) from the cART period (P < 0.01). In the multivariate analysis, the pre-cART period, previous PcP prophylaxis with sulfa drugs, and homosexuality as an HIV risk factor were found to be associated with a higher risk of presenting DHPS mutations. Overall, 95% of patients were treated with trimethoprim and sulfamethoxazole (TMP-SMX). In-hospital mortality was similar in patients with (out) mutations (6% versus 11%, P = 0.84). DHPS gene mutations were more common during the pre-cART period and were associated with previous sulfa exposure and homosexuality. However, their presence did not worsen prognosis of PcP. The response to TMP-SMX with therapeutic doses was successful in most cases.

Microbial airway colonization is associated with noninvasive ventilation failure in exacerbation of chronic obstructive pulmonary disease.

OBJECTIVE: Abnormal airway colonization in patients with chronic obstructive pulmonary disease (COPD) needing invasive mechanical ventilation (IMV) is considered a first step in the acquisition of nosocomial pneumonia. Noninvasive ventilation (NIV) could potentially avoid this, but airway colonization has not been studied in patients who undergo NIV. We hypothesized that patients undergoing NIV would have lower rates of colonization than patients undergoing IMV. The aim of the study was to assess the microbial airway colonization in patients with exacerbated COPD needing NIV and IMV. DESIGN: A 2-yr prospective cohort study. SETTING: Respiratory intensive and intermediate care unit. PATIENTS: Eighty-six patients with exacerbated COPD undergoing NIV on admission (64 successes and 22 failures, according to subsequent intubation), and 51 patients undergoing IMV on admission. INTERVENTIONS: Quantitative culture specimens of sputum or tracheal aspirate were collected on admission and at follow-up (day 3) during NIV or IMV, respectively. Clinical assessment, including severity scores, and arterial blood gas measurements were also determined. MEASUREMENTS AND MAIN RESULTS: Compared with the NIV-success group, colonization by potentially pathogenic microorganisms was greater in the NIV-failure group on admission (13 [59%] vs. 14 [22%]; p < .001) and at follow-up while patients still underwent NIV (14 [93%] vs. 7 [14%]; p < .001), and it was even higher than during IMV at follow-up (20 [50%]; p = .027). Colonization by nonfermenting Gram-negative bacilli, mainly Pseudomonas aeruginosa, was significantly associated with NIV failure on admission (OR, 5.6; p = .016) and at follow-up (OR, 23.5; p < .001). Moreover, colonization by these microorganisms at follow-up (OR, 8.8; p = .008) and inadequate antimicrobial treatment (OR 11.3; p = .001) were associated with increased hospital mortality. CONCLUSIONS: Airway colonization by nonfermenting Gram-negative bacilli is strongly associated with NIV failure. Because it occurs before intubation, this would be a marker rather than just a consequence of NIV failure necessitating intubation. The efficacy of decreasing airway colonization in preventing NIV failure needs to be assessed.

Bacterial and fungal bloodstream isolates from 796 hematopoietic stem cell transplant recipients between 1991 and 2000.

To examine shifts in the etiology, incidence, evolution, susceptibility, and patient mortality of bacterial and fungal bloodstream isolates (BSIs) from hematopoietic stem cell transplantation (HSCT) recipients, we reviewed the BSIs of 796 patients who underwent an HSCT in our institution during a 10-year period. Four hundred eighty-nine episodes of bacterial and fungal BSI were detected in 330 patients (41%). Three hundred ten isolates (63%) were gram-positive bacteria, 142 (29%) were gram-negative, and 18 and 19 isolates were different species of anaerobic organism and Candida spp. (both 4%). Coagulase-negative staphylococci (CoNS), with 210 isolates, were the organism most frequently isolated in each year of study and during the three phases of immune recovery after HSCT. The ratio of gram-positive to gram-negative has declined from 3.3 (1991-1992) to 1.8 (1999-2000). Crude mortality occurred in 47 cases of 489 BSI episodes (10%). Mortality according to groups was gram-negative, 7%; gram-positive, 9%; and anaerobic bacteria, 11%. Candida spp. was the group that accounted for the highest crude mortality, with 42%. Gram-positive microorganisms were isolated more often than gram-negative organisms, but the trend is reversing. CoNS were the leading pathogen during the 10 years of study and during the three phases of immune recovery after HSCT. Crude mortality of HSCT patients with BSI was low except for infections caused by Candida spp.