Amira Sellami

Pathogenic free-living amoebae: Epidemiology and clinical review

Free-living amoebae are widely distributed in soil and water. Small number of them was implicated in human disease: Acanthamoeba spp., Naegleria fowleri, Balamuthia mandrillaris and Sappinia diploidea. Some of the infections were opportunistic, occurring mainly in immunocompromised hosts (Acanthamoeba and Balamuthia encephalitis) while others are non opportunistic (Acanthamoeba keratitis, Naegleria meningoencephalitis and some cases of Balamuthia encephalitis). Although, the number of infections caused by these amoebae is low, their diagnosis was still difficult to confirm and so there was a higher mortality, particularly, associated with encephalitis. In this review, we present some information about epidemiology, ecology and the types of diseases caused by these pathogens amoebae.

Evaluation of nested and real-time PCR assays in the diagnosis of candidaemia

Polymerase chain reaction (PCR) assays have a very low theoretical detection threshold and are therefore advocated for the diagnosis of fungaemia. However, their effectiveness in this respect remains to be assessed. This study compared real-time PCR (Can-G) and nested PCR assays with blood culture for the diagnosis of Candida spp. bloodstream infections. A total of 200 clinical blood samples obtained from 110 patients at risk for developing a systemic fungal infection, hospitalized in the University Hospital of Sfax (Tunisia), were submitted to testing by culture, nested PCR and real-time PCR. Blood culture was positive in 36 patients. When compared with culture, the Can-G assay (81% sensitivity, 96% specificity) performed better than the nested PCR assay (86% sensitivity, 54% specificity). The real-time PCR assay, which avoids both the contamination hazard with amplicons that may cause false-positive results and the use of time-consuming post-PCR steps, appears more suitable than the nested PCR assay for the laboratory diagnosis of Candida spp. bloodstream infections. In this study, real-time PCR did not enhance the diagnostic sensitivity for Candida spp. bloodstream infections compared with conventional blood culture; however, it may lead to earlier implementation of an adequately targeted antifungal treatment.

Epidemiology of dermatophytoses in Sfax, Tunisia.

The distribution of dermatophytes varies in different countries and geographical areas depending on several factors. To determine the frequency of aetiological agents and the clinical variants of dermatophytoses, we carried out a study between 1998 and 2007. Out of 25 432 subjects suspected to have superficial mycoses, 9960 (39.2%) were affected with dermatophytoses; 14957 positive samples were obtained. The mean age was 35.7 years (range: 21 days to 97 years). Sex ratio was 0.9. Our patients were from urban regions in 81.9% of cases. The most common type of infection was onychomycosis (30.3%), followed by tinea pedis (24.8%), intertrigo (21.7%), tinea corporis (11.4%) and tinea capitis (9.6%). Fifteen patients had generalised dermatophytosis. Hadida and Schousboe disease was diagnosed in one case with lethal evolution. The most isolated dermatophyte was Trichophyton rubrum (74.5%), followed by T. violaceum (7.9%), T. mentagrophytes (7.5%), Microsporum canis (3.8%), Epidermophyton floccosum (0.7%) and T. verrucosum (0.54%). Other species were occasionally isolated: T. schoenleinii, T. tonsurans, M. audouinii and M. ferrugineum. The prevalence of dermatophytoses remains high in our country (996 cases/year). Trichophyton rubrum is the predominant causal agent. However, zoophilic agents become more prevalent. Epidemiological surveys are an essential tool for developing strategies for infection control.

Invasive aspergillosis: epidemiology and environmental study in haematology patients (Sfax, Tunisia)

Invasive aspergillosis (IA) is a major opportunistic infection in haematology patients. Preventive measures are important to control IA because diagnosis is difficult and the outcome of treatment is poor. We prospectively examined the environmental contamination by Aspergillus and other fungal species and evaluated the prevalence of invasive aspergillosis in the protect unit of haematology. A three‐year prospective study (December 2004–September 2007) was carried out in the department of haematology of Hedi Chaker Hospital. Suspected invasive aspergillosis cases were reviewed and classified as proven, probable and possible invasive aspergillosis using the EORTC criteria. During the study period, we collected weekly environmental samples (patient’s rooms, tables and acclimatisers) and clinical samples from each patient (nasal, expectoration and auricular). Among 105 neutropenic patients, 16 had probable and 13 had possible IA. A total of 1680 clinical samples were collected and A. flavus was most frequently isolated (79.2%). Analysis of 690 environmental samples revealed that Penicillium (44%) was the most frequent followed by Cladosporium (20%), Aspergillus spp. (18%) and Alternaria (13%). The PCR‐sequencing of 30 A. flavus isolates detected from clinical and environmental samples confirmed the mycological identification. Our findings underline the importance of environmental surveillance and strict application of preventive measures.

Epidemiological survey of vulvovaginal candidosis in Sfax, Tunisia

Vulvovaginal candidosis (VVC) is a common infection of the female genital tract affecting 75% women at least once in their lifetime. The aim of this study was to determine the incidence and potential risk factors associated with VVC and recurrent vulvovaginal candidosis (RVVC). A prospective study of women with vaginitis symptoms was conducted over 2 years in the regional clinic of population and family education in Sfax. A discriminant analysis was used to evaluate the association between the incidence of Candida vaginitis and potential risk factors. Sporadic and recurrent VVC were documented respectively in 48% and 6.1%. The most frequent factors associated with positive Candida culture were employed women, uncontrolled diabetes, history of genital infection and intrauterine device contraception. Increased episode numbers of VVC and condom/spermicidal contraception were positively associated with recurrences. Candida albicans was the predominantly isolated species (76.3%) followed by Candida glabrata (19.3%). Infection with C. glabrata occurred in 34% and 17.5% of patients with RVVC and VVC respectively. The discriminant investigation had provided further insights into the basis for prevention and control of RVVC. Increased prevalence of C. glabrata in patients with RVVC and observed risk factors should be taken into consideration to achieve success in the management of this infection.

Candida dubliniensis: first identification in Sfax hospital, Tunisia

Candida dubliniensis, a newly described fungal pathogen associated mainly to immunocompromised host’s infection, is phenotypically closely related to C. albicans. In this study, we report for the first time, isolation and identification, in Tunisia, of 14 isolates of C. dubliniensis from 12 human immunodeficiency virus‐negative patients hospitalised in the intensive care unit (ICU) at Habib Bourguiba Sfax Hospital. Our study was firstly based on the failure to grow at 45 °C. This presumptive identification was completed by other tests: chlamydospore production, culture on Candiselect4 (Bio‐Rad) and the commercial test Bichro‐Dubli fumouze®, which specifically identify C. dubliniensis. The confirmation of the discrimination between both species was performed by PCR, targeting the hyphal wall protein (HWP1) gene. The recovery of C. dublinensis by routine laboratory diagnosis is recommended for elucidating the epidemiology of this novel pathogen.

Genetic diversity of Pneumocystis jirovecii strains based on sequence variation of different DNA region

Pneumocystis jirovecii is an important opportunistic pathogen that causes severe pneumonia in immunocompromised patients. The aim of the present study was to investigate the genetic diversity of P. jirovecii strains by direct sequencing and analysis of the Upstream Conserved Sequence (UCS) region, mitochondrial large-subunit (mtLSU) rRNA and dihydrofolate reductase (DHFR) genes. We identified the polymorphisms in P. jirovecii strains of 15 immunocompromised patients, as well as detecting a new tandem repeat of 5 nucleotides in UCS region. The following three different types of repeat unit were found: type a GCCCA; type b GCCCT; and type c GCCTT. In addition, we identified the repeat unit which consisted of 10 nucleotides and three different patterns of UCS repeats with 3 and 4 repeats, i.e., 1, 2, 3 (86.7%), 1, 2, 3, 3 (6.6%) and a new genotype 2, 2, 3, 3 (6.6%). The polymorphism in the mtLSUrRNA gene was seen primarily at position 85 where we detected three different genotypes. Genotype 3 and genotype 2 were the most abundant with frequencies of 53.3% and 40%, respectively. With regard to the DHFR gene, only two (20%) patients had nucleotide substitution in position 312. In conclusion, the multilocus analysis facilitated the typing of P. jirovecii strains and proved the important genetic biodiversity of this fungus.

Two new media Pinus halepensis seed agar and blackberry agar for rapid identification of Cryptococcus neoformans

Cryptococcus neoformans is an encapsulated yeast‐like fungus that causes life‐threatening infections, particularly in immunocompromised patients. The formation of brown pigment on many media described in the literature, such as that in Niger seed (Guizotia abyssinica) agar, has been used to identify C. neoformans. The present study compares melanin production by clinical and environmental isolates of C. neoformans and other medically important yeast on two new media, Pinus halepensis seed (PHS) agar and blackberry (BlaB) agar, and the classic medium Niger seed agar. Results obtained after the culture of 46 strains of C. neoformans, for 4, 24 and 48 h at 37 °C on these three media, showed that at 24 h, 100% of strains were pigmented on BlaB agar, 91.3% on PHS agar but only 34.8% on Niger seed agar. In conclusion, PHS and BlaB agar are two interesting new media for the rapid identification of C. neoformans isolates.

Childhood dermatomycoses study in Sfax hospital, Tunisia

Mycoses are frequent affections in childhood. Fungal type varies according to the age and the affected organ. The aim of this study was to determine the aetiological agents of childhood dermatomycoses and to draw attention to the diversity of their clinical manifestations. Retrospective study dealing with children’s cases with age <16‐year old and having dermatomycosis diagnosed between 1991 and 2005 at the Parasitology and Mycology Laboratory of Sfax University Hospital. A total of 4559 children suspected to have superficial mycoses were examined. Dermatomycosis diagnosis was confirmed in 49.3% of cases. Dermatophytes were the most prevalent fungal agents and accounted for 1865 cases (80.6%) dominated by Trichophyton violaceum (54.1%) and Microsporum canis (24.5%). Tinea capitis (69.4%) was the most common type of infection, followed by tinea corporis (20%). Superficial yeast infections (442 cases) were dominated by Malassezia infections (71%). Candida infections were mainly due to Candida albicans (58%). The clinical features of paediatric dermatomycoses vary with the age of the children: tinea capitis and tinea corporis were more frequent before 13 years of age. After this age, tinea versicolor and onychomycoses became more common.

A rapid and easy method for the DNA extraction from Cryptococcus neoformans

DNA isolation from C. neoformans is difficult due to a thick and resistant capsule. We have optimized a new and rapid DNA isolation method for Cryptococcus using a short urea treatment followed by a rapid method using a chelex resin suspension. This procedure is simpler than previously reported methods.