The expression of Toll-like receptors and development of severe sepsis in patients with acute myeloid leukemias after induction chemotherapy

Toll-like receptors play an important role in the host defense against microorganisms. Sepsis remains a common cause of mortality in patients with acute myeloid leukemia (AML) treated with intensive induction chemotherapy. The expression of TLRs and their association with the development of sepsis in patients with acute myeloid leukemia remains unclear. The aim of this study was to investigate the associations between expression of TLR2, TLR4 and TLR9 and occurrence of sepsis in patients treated with intensive induction chemotherapy for AML. A total of 103 patients with newly diagnosed AML were evaluated. Bone marrow samples were taken before induction therapy. Using quantitative reverse transcriptase PCR, the mRNA expression of genes TLR2, TLR4 and TLR9 was measured. Neutropenic fever occurred in 98 patients. We identified 20 episodes of severe sepsis (20%). In patients with neutropenic fever, the mRNA expression of TLR2 and TLR4 was significant higher in septic patients than in patients without sepsis symptoms (ΔCt TLR2 0.93 ± 0.82 vs 0.78 ± 0.85 and ΔCt TLR4 0.38 ± 0.29 vs 0.34 ± 0.25). Moreover, we observed that expression of TLR2 and TLR4 was significantly higher in patients with AML and bacterial infection in comparison with group with separate fungal infection (ΔCt TLR2 1.15 ± 1.06 vs 0.66 ± 0.51 and ΔCt TLR4 0.45 ± 0.38 vs 0.21 ± 0.19). Our results suggest that TLRs could be an independent factor for the development of sepsis in patients with acute myeloid leukemias after intensive induction chemotherapy. This observation should be validated by larger study.

Antifungal resistance does not necessarily affect Candida glabrata fitness

Although there has been an overall good coverage of Candida glabrata infections by the echinocandins, emergence of antifungal resistance during therapy has been reported. We investigated, by using an invertebrate host model, the fitness of sequential C. glabrata isolates with different echinocandins susceptibility patterns. The studied strains were isolated from a case of recurrent fungemia with a fatal outcome due to C. glabrata that developed cross-resistance to echinocandins during caspofungin therapy. The sequential strains isolated post-therapy showed a S663P mutation in the Fks2p hot spot 1. In vivo study in the invertebrate host Galleria mellonella did not suggest a fitness cost related to the acquired antifungal resistance, the three isolates displayed a similar rate of killing (P  =  0.54). We observed a clear correlation between emergence of antifungal resistance and persistence of the causal agent, probably aided by the unchanged fitness and unresponsiveness in vivo to the adopted therapy.

Rapid identification of pathogens in blood culture with fluorescent in situ hybridization (FISH)

Rapid identification of pathogens in bloodstream infections is of utmost importance to improve survival of septic patients. Fluorescent in situ hybridization (FISH) accelerates the identification of most frequent bacterial and yeast pathogens of sepsis. In this study, 210 positive blood cultures were tested with FISH method and the results were evaluated comparing to the traditional cultivation based results. Overall agreement between FISH and conventional identification was 91.4%, with better results for Gram-negative bacteria than for Gram-positives (100% and 89.5%, respectively). FISH results were obtained within 1 hour. FISH may serve as a useful tool to supplement traditional microbiological methods for rapid, provisional identification of sepsis pathogens.

Mannose-binding lectin deficiency facilitates abdominal Candida infections in patients with secondary peritonitis

Mannose-binding lectin (MBL) deficiency due to variations in the MBL gene is associated with increased susceptibility to infections. In this study, the association between MBL deficiency and the occurrence of abdominal yeast infection (AYI) in peritonitis patients was examined. Eighty-eight patients with secondary peritonitis requiring emergency laparotomy were included. MBL genotype (wild type [WT] versus patients with variant genotypes), MBL plasma concentrations, and Candida risk factors were examined in patients with and those without AYI (positive abdominal yeast cultures during [re]laparotomy). A variant MBL genotype was found in 53% of patients with AYI and 38% of those without AYI (P = 0.18). A significantly higher proportion of variant patients had an AYI during early peritonitis (during first laparotomy) than WT patients (39% versus 16%, respectively; P = 0.012). Patients with AYI had lower MBL levels than did patients without AYI (0.16 microg/ml [0.0 to 0.65 microg/ml] versus 0.65 microg/ml (0.19 to 1.95 microg/ml); P = 0.007). Intensity of colonization (odds ratio [OR], 1.1; 95% confidence interval [CI], 1.0 to 1.1), MBL plasma concentrations of <0.5 microg/ml (OR, 4.5; 95% CI, 1.2 to 16.3), and numbers of relaparotomies (OR, 1.7; 95% CI, 1.0 to 2.8) were independently associated with AYI. In summary, deficient MBL plasma levels were independently associated with the development of AYI in patients with secondary peritonitis and seemed to facilitate early infection.

Toll-like receptor 4 Asp299Gly/Thr399Ile polymorphisms are a risk factor for Candida bloodstream infection

Toll-like receptor (TLR)-4 is an important pattern recognition receptor for Candida albicans, playing a role in innate host defense. We investigated whether there is an association between the TLR4 Asp299Gly or TLR4 Thr399Ile polymorphism, and the occurrence of Candida bloodstream infection. We performed a case-control study, involving 43 patients with a Candida bloodstream infection and 166 healthy individuals. TLR4 Asp299Gly and Thr399Ile polymorphisms were assessed, as well as cytokine production after stimulation of peripheral blood mononuclear cells (PBMC) with Candida albicans. We observed that the prevalence of TLR4 Asp299Gly polymorphism was found to be higher in patients with Candida bloodstream infection than in controls (26% versus 10%; OR 3.0; 95%CI 1.3-6.9). All patients bearing the Asp299Gly polymorphism were also positive for the Thr399Ile allele, a linkage well described in literature. IL-10 production was higher in C. albicans-stimulated PBMC from volunteers bearing the TLR4 Asp299Gly polymorphism, and a similar tendency was observed in TLR4 Asp299Gly heterozygous patients who had recovered from candidemia. These findings show that the TLR4 Asp299Gly/Thr399Ile polymorphisms are associated with an increased susceptibility to Candida bloodstream infections, and an increased production of IL-10 is probably involved in this effect.

Tumor necrosis factor alpha -- 308 polymorphism associated with increased sepsis mortality in ventilated very low birth weight infants

BACKGROUND

Sepsis commonly complicates the clinical course of critically ill very low birth weight infants, with as many as 30% developing hospital-acquired bacteremia. The tumor necrosis factor alpha (TNF-alpha) -- 308 G/A single nucleotide polymorphism (SNP) is associated with adverse outcome in septic adult patients.

METHODS

One hundred seventy-three mechanically ventilated very low birth weight infants were genotyped for the TNF-alpha -- 308 G/A SNP.

RESULTS

One hundred twenty (69%) infants were homozygous GG, 45 (26%) were heterozygous AG and 8 (5%) were homozygous AA; 2 of 120 (2%) infants developed early bacteremia in the GG group, and 1 of 53 (2%) developed early bacteremia in the AA/AG group (P = 0.919). One or more episodes of late bacteremia/fungemia developed in 59 of 120 (49%) infants with the GG genotype and 23 of 53 (43%) infants with the AG/AA genotype (P = 0.484). Endotracheal tube colonization rates were 65 of 120 (54%) for infants with the GG genotypes and 28 of 53 (53%) for infants with the AG/AA genotypes (P = 0.871). Nosocomial pneumonia developed in a similar number of infants in both genotype groups (9 of 120 infants vs. 3 of 53 infants; P = 0.461). Mortality from sepsis was 3 times greater in infants with the AA/AG genotypes than in those with the GG genotype (10%vs. 3%; P = 0.038). This difference in sepsis mortality was even greater when only bacteremic/fungemic infants are considered (4 of 59 infants vs. 6 of 23 infants; P = 0.026).

CONCLUSIONS

These data suggest that the TNF-alpha -- 308 A allele does not affect the development of sepsis in ventilated premature infants but may increase mortality once sepsis develops.

Chitotriosidase deficiency in survivors of Candida sepsis

The existence of chitotriosidase, a human chitinolytic enzyme, hydrolyzes artificial chitotrioside substrates, but its specific function in humans is unknown. The homologous chitinases have an anti-fungal action in plants. In patients with Gaucher disease, chitotriosidase activity is markedly elevated and is a marker for response to specific treatment. In all populations, 6% of individuals are enzyme deficient but completely healthy. It was hypothesized that chitotriosidase deficient persons may be more vulnerable to fungal infections. Thus, the objective of the study was to ascertain the prevalence of homozygosity for the mutation of chitotriosidase among survivors of Candida sepsis. The prevalence of homozygosity among survivors was similar to that in the normal population. Although the cohort is the largest of its kind, since only survivors were tested, further studies should include all patients with Candida sepsis for comparison of survival rates among deficient versus sufficient individuals, and thereby elucidate if this enzyme has an anti-fungal function in man. Several theories are considered to explain the results.

Strain characterization of Candida parapsilosis fungemia by molecular typing methods

The present study used two molecular typing methods to investigate a cluster of eight cases of Candida parapsilosis fungemia in a hospital in Rio de Janeiro, Brazil. Candida parapsilosis is an important opportunistic pathogen that is frequently involved in outbreaks of nosocomial fungemia. Identification of a common source of infection and determination of genetic relatedness among the strains involved in outbreaks are important for infection control. Candida parapsilosis strains were isolated from the bloodstream of patients housed in an intensive-care unit (n=5) and in individual rooms (n=3). An additional strain of Candida parapsilosis was isolated from a hyperalimentation infusion flask, which was implicated by molecular typing to be the source of infection. All strains were identified using morphological and biochemical methods. The genetic relationship between patients' strains and the hyperalimentation infusion strain was assessed by electrophoretic karyotype (EK) analysis and random amplification of polymorphic DNA (RAPD). Both methods resulted in patterns that allowed differentiation of the isolates. Candida parapsilosis fungemia, in three of the eight patients, resulted from a common source of infection, as demonstrated by molecular typing methods. Image analysis of EK patterns indicated that these strains were closest to Candida parapsilosis Group II, a grouping that is a less frequent clinical isolate than the major Group I strains.