Invasive aspergillosis due to Aspergillus cryptic species: A prospective multicentre study

OBJECTIVES

Aspergillus cryptic species are increasingly recognised causes of Aspergillus diseases, including life-threatening invasive aspergillosis (IA). However, as their accurate identification remains challenging in a routine practice, few is known from a clinical and epidemiological perspective. Recently, the MSI application has emerged as a powerful tool for the detection and identification of Aspergillus cryptic species. We aimed to use to the network of users of the MSI application to conduct a multicentre prospective screening of Aspergillus cryptic species-related IA and analyse their epidemiological, clinical and mycological characteristics.

METHODS

Over a 27-month period, the clinical involvement of 369 Aspergillus cryptic isolates, from 13 French and Danish MSI application users, was prospectively analysed. Species identification was confirmed by DNA-sequencing and antifungal susceptibility testing was performed using EUCAST reference method. Fifty-one A fumigatus sensu stricto invasive cases were also analysed.

RESULTS

Fifteen cryptic isolates were responsible of IA. Eight species were involved, including 5 cases related to the species A sublatus. These species showed high rate of in vitro low susceptibility to antifungal drugs. In comparison with A fumigatus sensu stricto invasive cases, pre-exposure to azole drugs was significantly associated with cryptic IA (P = .02).

DISCUSSION

This study brings new insights in cryptic species related IA and underlines the importance to identify accurately at the species level these Aspergillus isolates. The increasing use of antifungal drugs might lead in the future to an epidemiologic shift with an emergence of resistant isolates involved in IA.

Toxoplasma gondii: taux de portage chez les ovins de la région de Marrakech (Mnabha)

Toxoplasma gondii is an ubiquitous parasite with a prevalence variable from country to country. In Morocco very few studies were devoted to this prevalence. To fill this gap we were interested to study the epidemiology of this parasite and to know the level of carriage by the different vectors which are the sources of contamination in humans. The study was done by directly detecting the cysts in the cerebral tissue of the 50 sheep killed and destined for consumption. The results of this preliminary study show that 30% of the cases carry the cysts of T. gondii. To confirm this result and verify the virulence, cerebral specimens were inoculated into mice. These findings are encouraging to complete this study with serological tests and to look for the parasite in cows and goats of this region.

Acquired resistance to voriconazole and itraconazole in a patient with pulmonary aspergilloma

We describe the development of resistance in an Aspergillus fumigatus strain, originally sensitive to itraconazole and voriconazole, recovered from a case of pulmonary aspergilloma treated with voriconazole. A G448S mutation on the cyp51A gene was detected by sequencing. Frequent culture and in vitro antifungal susceptibility testing is suggested for early detection of the development of multi-azole resistance in patients on long-term therapy for A. fumigatus infections.

[Dry sausage mould hypersensitivity pneumonitis: three cases]

INTRODUCTION

Hypersensitivity pneumonitis (HP) can occur as a consequence of inhaling a wide range of different antigens. The clinical diagnosis is based on five main criteria as proposed by the GERM'O'P.

CASE REPORTS

We present in this report three cases of occupational hypersenstitivity pneumonitis caused by inhalation of dry sausage mould. Lung infiltrates were observed in each case on CT scanning, with a lymphocytic or mixed inflammatory picture in bronchoalveolar lavage fluid, and specific antibodies (precipitins) against extract from dry sausage mould (which notably contains Penicillium). In all three cases, the condition improved after reducing exposure to the allergen and, in two cases, after the administration of corticosteroid therapy.

CONCLUSION

Exposure to dry sausage mould occurs in work places where salami is made and should be considered as a possible cause of hypersenstitivity pneumonitis.

Efficacy of environmental measures to decrease the risk of hospital-acquired aspergillosis in patients hospitalised in haematology wards

This study evaluated a multidisciplinary strategy to decrease the rate of invasive pulmonary aspergillosis (IPA) among adult patients hospitalised in two haematology wards in a single 560-bed building at the University Hospital of Saint-Etienne. Upgrading of the air filtration system and construction of an air-lock chamber at the entrance to the unit were completed during 1994. In 1995, specific hygienic measures were introduced during hospital building work, including the use of plastic barriers, watering during demolition work, reduction of pedestrian traffic in construction areas, and the wearing of high-efficiency filtration masks by immunosuppressed patients when outside the protected unit. This strategy was evaluated by a prospective survey of IPA cases between 1993 and 2001, coupled with environmental surveillance. The number and risk-level of hospital renovation projects increased between 1995 and 2001 (p < 0.01). In parallel, the rate of IPA decreased globally in the haematology unit from 0.85% (1.19/1,000 patients) in 1993 to 0.28% (0.21/1,000 patients) in 2001. The incidence of IPA decreased significantly between 1993-1996 and 1997-2001 (p 0.02, Mann-Whitney test). These results show that a multidisciplinary approach involving engineers, infection control practitioners, mycologists and clinicians enables IPA rates among patients hospitalised in haematology wards to be significantly decreased.

Seroprevalence of T. gondii in sheep from Marrakech, Morocco

Toxoplasma gondii is a ubiquitous intracellular protozoan parasite transmitted by food. Concerning this parasite, there are few studies done in Morocco. In this study, 261 sera from sheep intended for consumption in Marrakech were subjected to the Toxoplasma ELISA based serology test for the detection of anti-T. gondii specific IgG confirming a past infection. Of the total tested 72 (27.6%) sera were positive for IgG. This result shows that the seroprevalence approaches the world average and is similar to what is found in other cities of Morocco. This has prompted us to investigate other animal species in the region in order to evaluate the degree of contamination by this parasite as well as the potential risk incurred on consumption of their meat.

Efficiency of blood culture bottles for the fungal sterility testing of corneal organ culture media

BACKGROUND/AIM

The consequences of fungal contamination of an organ cultured cornea, though exceptional, are often disastrous for the recipient. Consequently, eye banks often quarantine corneas for 10 days or more before passing them for grafting. This period, though detrimental to the endothelial cell density of the delivered cornea, is necessary to detect contamination using conventional microbiological methods. The authors previously validated the use of a pair of aerobic and anaerobic blood bottles for sensitive and rapid detection of bacteria. To allow a short quarantine period, it remained only to optimise detection of fungi. The authors aimed to compare sensitivity and rapidity of fungal contamination detection by three methods: blood bottles, Sabouraud, and daily visual inspection of the organ culture medium.

METHODS

Four inocula (10(6), 10(4), 10(2), 10 colony forming unit (CFU) per ml) of 11 fungi (Candida albicans, C tropicalis, C glabrata, Saccharomyces cerevisiae, Rhodotorula rubra, Cryptococcus neoformans, Fusarium oxysporum, Aspergillus niger, A fumigatus, A flavus, Acremonium falciforme) were inoculated in a commercial organ culture medium containing a coloured pH indicator (CorneaMax, Eurobio, Les Ulis, France). The real live fungal inoculum was verified immediately after inoculation. After 48 hours at 31 degrees C, samples of the contaminated media were inoculated in three blood bottles: Bactec Aerobic/F, Bactec Mycosis IC/F, and Bactec Myco/F Lytic (Becton Dickinson, Le Pont de Claix, France), then placed in a Bactec 9240 rocking automat, and in four Sabouraud media (solid and liquid, 28 degrees C and 37 degrees C) with daily observation. Contaminated organ culture media were also checked daily for any change in turbidity and/or colour. Experiments were performed in triplicate.

RESULTS

Mycosis IC/F and Myco/F Lytic bottles were neither faster nor more sensitive than the aerobic bottle. The three methods were positive for all inocula, even the lowest (viable inoculum below 10 CFU/ml for each fungus). Contamination was detected within 24 hours by the aerobic bottles in 91% (40/44), by Sabouraud in 98% (43/44) (no significant difference) and by visual inspection in 66% of cases (29/44) (p<0.001 with the two others). Maximum times to detection were 46, 48 and 72 hours respectively.

CONCLUSION

This study further counters the preconception that fungal contamination is hard to detect in corneal organ culture media. This study is the last step in validating the use of a pair of blood bottles for the sterility testing of organ culture media, this time for fungi. Their use should make it possible to shorten microbiological quarantine and thus deliver corneas with higher endothelial cell density, without increasing the risk of recipient contamination.

In vitro susceptibility testing of Candida and Aspergillus spp. to voriconazole and other antifungal agents using Etest®: results of a French multicentre study

Minimum inhibitory concentrations (MICs) of the antifungal agent voriconazole were determined using the Etest and compared with those of amphotericin B, itraconazole and fluconazole using 1986 clinical isolates of Candida spp. Voriconazole MICs were also compared with those of amphotericin B and itraconazole using 391 clinical isolates of Aspergillus spp. Voriconazole was found to have more potent activity and lower MIC values than amphotericin B, itraconazole and fluconazole against C. albicans, C. tropicalis, C. parapsilosis and C. kefyr. Against C. glabrata and C. krusei, voriconazole was more active than either of the other two azole antifungals but had similar activity to amphotericin B. For species of Aspergillus, MIC values of voriconazole were lower than those of amphotericin B and itraconazole against A. fumigatus and A. flavus, and were similar to those of amphotericin B against A. niger. Against A. terreus, MIC values for voriconazole and itraconazole were similar. A. terreus is known to be resistant to amphotericin B, and this was reflected in higher MIC values compared with those of voriconazole and itraconazole. Voriconazole therefore compares very favourably with other antifungal agents against a large number of clinical isolates of Candida and Aspergillus spp.

Influence of the quantity of nonspecific DNA and repeated freezing and thawing of samples on the quantification of DNA by the Light Cycler®

Quantification of DNA in real-time using the Light Cycler is increasingly being used for the detection and follow-up of various infectious and other diseases. We evaluated the effect of two parameters, namely the presence of nonspecific DNA and prior repeated freezing and thawing on the accurate quantification of DNA extracts from the RH strain of Toxoplasma gondii by the SYBR Green I and the Hybridization Probe techniques. For both parameters, a high copy number sample containing 5x10(5) parasites/extract and a low copy number sample containing 100 parasites/extract were tested. Reliable quantification was possible in the presence of up to 200 ng of nonspecific DNA by the SYBR Green I technique and up to 1000 ng by the Hybridization Probe technique as compared to the company threshold of 50 and 500 ng, respectively. As tissue samples usually contain more than 200 ng of nonspecific DNA, the ideal choice is the Hybridization Probe technique. The stability of DNA extracts after repeated freeze-thaw cycles was found to be dependent on the volume in which they were stored. Samples stored in 100-microl total volumes were not stable after 3 freeze-thaw cycles, whereas those stored in 1-ml total volumes were stable after 14 freeze-thaw cycles.

Routine use of a one minute trehalase and maltase test for the identification of Candida glabrata in four laboratories

AIMS

To evaluate the rapid identification of Candida glabrata using a one minute trehalase and maltase test in four clinical laboratories.

METHOD

The test was evaluated with 944 freshly isolated yeasts comprising 572 C glabrata and 372 non-C glabrata strains. These strains were isolated on one of three differential media-Candida ID, CHROMagar Candida, or Albicans ID2 medium-and all strains were fully identified using standard methods.

RESULTS

The trehalase and maltase test allowed the overall identification of 550 of 572 C glabrata strains (sensitivity, 96.2%) and only 11 of 372 isolates of other yeast species yielded a false positive result (specificity, 96.8 %). Sensitivity and specificity were consistent from one laboratory to another. Using Candida ID medium, the rapid trehalase and maltase test showed a sensitivity of 95% and specificity of 96.2%. Using CHROMagar Candida, sensitivity and specificity were 95.6% and 98.1%, respectively. Using Albicans ID2 medium (tested by two laboratories), the sensitivity was 100% and 98.5% and specificity was 98.1% and 98.2%. In 60% of cases, the test could be performed directly from the primary isolation medium, thus reducing the time for identification.

CONCLUSION

The rapid trehalase and maltase test was highly reliable for the presumptive identification of C glabrata on primary isolation using three different chromogenic media. Direct recognition of C albicans by means of their characteristic colour on chromogenic media coupled with one minute trehalase maltase testing performed only on suspect colonies of C glabrata allowed for rapid presumptive identification of the two yeast species most commonly encountered in clinical samples.

Parasite load in guinea pig foetus with real time PCR after maternofoetal transmission of Toxoplasma gondii

Parasite loads of different tissues were assessed in guinea pig foetus after maternal infection. Twelve female guinea pigs were infected with 100 cysts of the 76 K strain of Toxoplasma gondii by the oral route. Inoculation was performed 20 +/- 5 days (G20) or 40 +/- 5 days (G40) after the beginning of gestation. Gestational age was determined by progesterone assay. Maternal and foetal organ samples were taken 60 days after the beginning of gestation. Parasite loads (from placenta, amniotic fluid (AF), cord blood (CB), foetal brain, liver, lung and spleen) were assessed by a real-time PCR quantification using fluorescence resonance energy transfer (FRET) hybridization probes on the Light Cycler. Congenital transmission was proven by the presence of parasites in blood or tissue samples of the foetus in 84.6% (11/13) and 100% (16/16) of cases after inoculation on G20 and G40, respectively. The quantitative analysis of our results after inoculation at G20 and G40 has allowed us to determinate the positive parasitic loads as a function of the origin of the sample and the period of inoculation. The parasite loads expressed as log (parasite/g) were low in AF and CB samples: 1.49 +/- 0.50 and 1.05 +/- 0.10 at G20 and 1.21 +/- 0.36 and 1.20 +/- 0.42 at G40 respectively. In contrast the placenta and the different foetal tissues had higher parasite burdens: 2.89 +/- 0.54 to 5.30 +/- 0.51 at G20 and 2.81 +/- 0.71 to 3.65 +/- 0.59 at G40. All the placentae were positive for parasites even in the two cases with no proven transmission. Real time quantitative PCR using the hybridization probe was a very sensitive and reproducible technique to study the kinetics of congenital toxoplasmosis in the guinea pig model wich is close to that of humans.

Identification of Candida glabrata by a 30-second trehalase test

Rapid (30-s) trehalase tests done with material from colonies of 482 yeasts suspended in a drop of trehalose solution on a commercially supplied glucose test strip were positive for 225 (99.1%) of 227 Candida glabrata isolates grown on either of two differential media, Candida ID medium or CandiSelect medium. The test was positive for only 3 (1.2%) and 12 (4.7%) of 255 isolates of other medically important yeast species grown on the same two media, respectively. A rapid maltase test done with a subset of 255 yeast isolates was negative for all but 1 of 64 trehalase-positive C. glabrata isolates, raising the specificity of the rapid testing for C. glabrata to 98.4 to 100%, depending on the isolation medium used. Rapid trehalase and maltase tests done independently in two laboratories with 217 yeast isolates showed sensitivities of 96.0 to 98.0% and specificities of 98.2 to 99.4% for identification of C. glabrata from colonies grown on Candida ID medium. The specificity was much lower because of frequent false-positive trehalose test results when the source of colonies was Sabouraud agar formulated with 4% glucose. We conclude that direct recognition of C. albicans as blue colonies on Candida ID isolation medium coupled with the performance of the 30-s trehalase and maltase tests for C. glabrata among the white colonies on this medium will allow the rapid presumptive identification of the two yeast species most commonly encountered in clinical samples.

Experimental model of congenital toxoplasmosis in guinea-pigs: use of quantitative and qualitative PCR for the study of maternofetal transmission

Maternofetal transmission of Toxoplasma gondii was assessed in pregnant guinea-pigs, with a gestational period of 65 +/- 5 days. A total of 56 female guinea pigs was infected by the intraperitoneal route (RH strain), by the oral or the intraperitoneal route (Prugniaud strain; PRU) or by the oral route (76K strain). Inoculation was performed 90 +/- 18 days or 30 +/- 9 days before the onset of gestation or 20 +/- 6 days or 40 +/- 6 days after. Gestational age was determined by a progesterone assay. Parasite loads (fetal brain and liver) were assessed by nested PCR and real-time PCR quantification on Light Cycler was performed with a SYBR Green I technique. The 76K strain appeared to be the most virulent in the model: the neonatal survival rate was 31%, in contrast to 53% and 68% for the PRU and RH strains, respectively. The percentage of survival of neonates for all strains taken together was lower after inoculation at 40 days' gestation (25%) than at 20 days' gestation (77%). Whatever the strain, maternofetal transmission determination was greater with nested PCR (54% for RH, 84% for PRU and 86% for 76K strains) than with real-time quantitative PCR (31% for RH, 66% for PRU and 76% for 76K strains). However, real-time quantitative PCR showed that neonatal parasite load was greater with the cystogenic strains (76K, PRU) and that high hepatic load (> 10000 parasites/g) was often associated with disease severity (11 of 12 cases). Therefore, this technique may provide an important element in understanding this congenital disease.

[Relevance of the new test Access Toxo IgM (II) in the serological interpretation of toxoplasmosis in pregnancy]

The detection of specific IgM is an important element in the diagnosis of seroconversion. In this study, we compared the new test Access Toxo IgM (II) versus the previous test Access Toxo IgM (I). This comparative study was done with 507 random sera and 89 selected sera (seroconversion, residual IgM, non specific IgM). The sensitivity and the specificity are higher with the new test (100% & 100% versus 97% & 98,6% respectively). Then, the high sensitivity of Access Toxo IgM (II) is more convenient for the earlier diagnosis of primary Toxoplasma infection. Moreover, the Access Toxo IgM (II) test was evaluated with our first results in routine laboratory (11,000 serology results between June 2000 and June 2001). With these results, we can confirm the specificity of the new test, and also determine the relevance of anti-toxoplasmic IgM. Moreover, an increase of sensitivity leads to an increase of residual IgM detection: 64% (37/58) of positive IgM is residual (> 4 months) as compared to 35% (27/78) with the previous test. In these case, the initiation of other tests such as the avidity test is necessary to validate or invalidate a seroconversion during pregnancy.

Comparison of PCR, capture ELISA and immunoblotting for detection of Toxoplasma gondii in infected mice

PCR was compared with capture ELISA and immunoblotting for the detection of Toxoplasma gondii in sera of acutely infected mice. One hundred animals were inoculated intraperitoneally with 5000 trophozoites of RH strain and five of them were killed every 3 h from 3 h to 21 h post infection (p.i.), and every day from day 1 to day 7 p.i.. No assay detected the parasite from 3 h p.i. to 15 h p.i. PCR was the most sensitive assay and detected the T. gondii from 18 h p.i., whereas the other assays detected it only from day 1.

Detection of Toxoplasma gondii by polymerase chain reaction in sera of acutely infected mice

The presence of Toxoplasma gondii DNA was detected in sera of acutely infected mice by polymerase chain reaction. Adult mice were inoculated intraperitoneally with 5 x 10(3) T. gondii RH strain tachyzoites. Five mice were killed every 3 hr from 3 to 21 hr post infection (PI) and every day from 1 to 7 days PI. Toxoplasma gondii DNA was first detected in 60% of the infected mice 18 hr PI and in 100% of the animals 21 hr PI and from 1 to 7 days PI. No mice survived longer than 7 days.

Specific antibody detection in human aspergillosis: a GEMO* multicentre evaluation of a rapid immunoelectrophoresis method (Paragon). Group d'Etude des Mycoses Opportunistes

A new immunoelectrophoresis system, the Paragon system, was evaluated in three different hospital centres with the aim of improving standardization of the serodiagnosis of human aspergillosis. To select the most efficient antigen, various commercial and home-made antigens were first tested on 19 sera from 19 patients with highly probable aspergillosis. The value measured using the Paragon anti-Aspergillus antibody detection system was then compared with the results obtained by conventional serological diagnostic methods (conventional immunoelectrophoresis, enzyme linked-immunosorbent assay, indirect immunofluorescence): this step was performed using the first 19 sera as well as 16 other sera from 13 patients with suspected aspergillosis. Concordant results were obtained in 28 cases. The discrepancies observed with seven sera were probably related to differences in the nature of the antigens. Paragon immunoelectrophoresis proved to be a practicable technique requiring only a small amount of serum and giving results within a shorter time than competitive methods (24-48 h). Its major drawbacks compared with conventional immunoelectrophoresis are some difficulties in reading, fewer precipitin lines and the relatively high cost of routine analysis.

Detection of circulating antigens of Toxoplasma gondii in human infection

Seventy-nine serum specimens from pregnant women and 29 from immunocompromised patients (12 from graft recipients and 17 from patients with acquired immunodeficiency syndrome) were classified into three groups according to their serologic status to Toxoplasma gondii as determined by immunofluorescence and an enzyme-linked immunosorbent assay (ELISA): no antibodies (group 1), acute acquired infection (group 2), and reactivation (group 3). These samples were tested for the presence of circulating antigens (CAg) of T. gondii by capture ELISA and immunoblotting. The presence of CAg was detected by at least one of the two techniques in six of 31 subjects in group 1, 51 of 68 subjects in group 2, and seven of nine subjects in group 3. Of a total of 108 serum specimens, 28 were found to be T. gondii-positive by capture ELISA, 57 by immunoblotting, and 21 by both techniques. Among the nine polypeptides detected by immunoblotting, 38 recognized p14, 17 recognized p8, and 16 recognized p8, and 16 recognized p30. These results demonstrate that the detection of CAg can aid in the diagnosis of infection by T. gondii in humans, especially in immunocompromised patients whose serologic response can be impaired.

Comparison of excretory/secretory and circulating antigens of Toxoplasma gondii by enzyme immunoassay and immunoblotting

Toxoplasma gondii trophozoites (RH strain) were cultured in embryonic fibroblasts in order to study the kinetics of production of excretory/secretory antigens, and the results were compared to the production of circulating antigens in an in vivo mouse model. By capture-ELISA, excretory/secretory antigens were first detected on the fourth day of culture whereas circulating antigens were first detected 1 day after infection. Similar concentrations of antigens were detected in both models as evidenced by comparable absorbance values. By immunoblotting, the excretory/secretory antigens were also detected later compared to circulating antigens (day 4 vs day 1). Seven major polypeptides were detected in both antigen preparations, six of them having the same molecular mass (110, 75, 48, 30, 24 and 22 kDa).

[Detection of circulating antigens of Toxoplasma gondii using immunoprecipitation reactions in murine toxoplasmosis]

Circulating antigens (AGC) of Toxoplasma gondii were detected by counter electro-immunodiffusion (CEID) from the fourth day, in mice OF1 infected with 1,000 and 5,000 Toxoplasma gondii RH strain trophozoites. The mean number of precipitant lines increased from 1.6 on the fourth day to 5.8 on the seventh day, after which no animals survived. With the "Prugniaud" cystogenic strain no AGC were detected in mice inoculated with 100 and 200 cysts. Other techniques used, such as double immunodiffusion and immunoelectrophoresis, were shown to be less sensitive than CEID, and of little use for the detection of AGC. These AGC present antigenic similarities with some cytoplasmic fractions, particularly the FC3 fraction, and some membranous fractions such as FM1, separated by Sephacryl S300 gel chromatography.

[Antigen analysis of Toxoplasma gondii using chromatography, polyacrylamide gel electrophoresis and immunoprecipitation]

Whole (EAT), cytoplasmic (EAC) and membranous (EAM) extracts were prepared from Toxoplasma gondii RH Strain trophozoites by means of osmotic lysis and/or ultra sonication. Sephacryl S 300 gel chromatography shows respectively 5, 4 and 2 protein fractions from EAT, EAC and EAM. Polyacrylamide gel electrophoresis (PAGE) allowed to detect 22 proteins (WM from 6 to 130 Kd) from cytoplasmic extract and 3 proteins (MW: 8, 30 and 65 Kd) from membranous extract. Immunoprecipitation techniques were performed with polyclonal antibodies against Toxoplasma prepared from serum and rabbits immunized with EAT. Counter electro-immunodiffusion (CEID) on cellulose acetate membrane was found to be more sensitive than double immunodiffusion and immunoelectrophoresis as it detected 8 lines with both cytoplasmic and membranous extracts. The latter seem to be composed of large numbers of proteins which are present in very low quantities difficult to detect in PAGE, but very antigenic and easily shown by CEID.