LInezolid Monitoring to MInimise Toxicity (LIMMIT1): a multicentre retrospective review of patients receiving linezolid therapy and the impact of therapeutic drug monitoring

BACKGROUND

Linezolid is a broad-spectrum antimicrobial but toxicity limits it use. This study aimed to evaluate linezolid toxicity in a large multicentre cohort. Secondary objectives were to identify factors contributing to toxicity, including the impact of therapeutic drug monitoring (TDM).

METHODS

Patients administered linezolid between January 2017 and December 2019 were reviewed retrospectively. Data was collected on patient characteristics, linezolid therapy and outcomes. Descriptive statistics were performed on all patients, and statistical comparisons were undertaken between patients who did and did not experience linezolid toxicity. A multivariable logistic regression model was constructed to identify any covariates correlated with toxicity.

RESULTS

Linezolid was administered to 1,050 patients. Of these, 381 patients did not meet the inclusion criteria, and 47 patients were excluded as therapy ceased for non-toxicity reasons. There were 105/622 (16.9%) patients assessed to have linezolid toxicity. Those who experienced toxicity displayed a higher baseline creatinine (96.5µmol/L vs 79µmol/L, p=0.025), lower baseline platelet count (225 × 10⁹/L vs 278.5 × 10⁹/L, p=0.002), and received a longer course (median 21 vs 14 days, p<0.001) than patients who did not. Linezolid TDM was performed in 144 patients (23%). The multivariable logistic regression demonstrated that TDM-guided appropriate dose adjustment significantly reduced the odds of linezolid toxicity (aOR=0.45, 95%CI 0.21-0.96, p=0.038), and that treatment duration > 28 days was no longer significantly associated with toxicity.

CONCLUSIONS

This study confirmed linezolid treatment-limiting toxicity remains a problem, and suggests that TDM-guided dose optimisation may reduce the risk of toxicity and facilitate prolonged courses beyond 28 days.

Multispecies Outbreak of Nocardia Infections in Heart Transplant Recipients and Association with Climate Conditions, Australia

Extreme weather conditions, coupled with greater susceptibility to opportunistic infection, could explain this outbreak.

A multispecies outbreak of Nocardia occurred among heart transplant recipients (HTR), but not lung transplant recipients (LTR), in Sydney, New South Wales, Australia, during 2018–2019. We performed a retrospective review of 23 HTR and LTR who had Nocardia spp. infections during June 2015–March 2021, compared risk factors for Nocardia infection, and evaluated climate conditions before, during, and after the period of the 2018–2019 outbreak. Compared with LTR, HTR had a shorter median time from transplant to Nocardia diagnosis, higher prevalence of diabetes, greater use of induction immunosuppression with basiliximab, and increased rates of cellular rejection before Nocardia diagnosis. During the outbreak, Sydney experienced the lowest monthly precipitation and driest surface levels compared with time periods directly before and after the outbreak. Increased immunosuppression of HTR compared with LTR, coupled with extreme weather conditions during 2018–2019, may explain this outbreak of Nocardia infections in HTR.

Disseminated Aspergillus lentulus infection in a heart transplant recipient: a case report

We present the first published case of successfully treated disseminated Aspergillus lentulus infection in a solid organ transplant recipient with invasive pulmonary disease, endophthalmitis, and a cerebral abscess. This case highlights important challenges associated with treating Aspergillus lentulus, particularly regarding antifungal resistance and toxicities associated with long-term antifungal therapy.

Assessment of cefepime toxicodynamics: comprehensive examination of pharmacokinetic/pharmacodynamic targets for cefepime-induced neurotoxicity and evaluation of current dosing guidelines

BACKGROUND

Cefepime-induced neurotoxicity (CIN) is an increasingly reported adverse event; however, the toxicity threshold remains unclear. This study was conducted to provide a comprehensive examination of the most appropriate threshold for CIN, and evaluate the ability of current dosing regimens to attain therapeutic targets.

METHODS

Data of the incidence of CIN and cefepime plasma concentrations were collected retrospectively from patients administered cefepime. Population pharmacokinetic modelling was used to determine daily cefepime trough concentration (C_min), maximum serum concentration and area under the concentration-time curve. The ability of each pharmacokinetic parameter to predict CIN was evaluated using receiver operating characteristic (ROC) curves, from which optimal toxicity thresholds were determined. Pharmacokinetic simulation was used to evaluate the ability of cefepime dosing guidelines to meet established efficacy targets, whilst maintaining exposure below the determined CIN threshold.

RESULTS

In total, 102 cefepime courses were evaluated, with CIN reported in 10. ROC analyses showed that all cefepime pharmacokinetic parameters were strongly predictive of CIN. C_min of 49 mg/L was identified as the optimal toxicity target, based on its predictive ability (0.88, 95% confidence interval 0.758-0.999, P<0.001) and ease of clinical use. Assessment of cefepime dosing regimens predicted that only 29% of simulated patients achieve therapeutic targets, with patients with impaired renal function more likely to exhibit subtherapeutic concentrations (89%), and patients with normal renal function likely to have potentially toxic exposure (64%).

CONCLUSIONS

The findings from this study provide evidence that cefepime exposure is highly predictive of CIN, with C_min of 49 mg/L being the most appropriate toxicity threshold. Further research is required to optimize cefepime dosing in the context of this therapeutic target.

A retrospective study to determine the cefepime-induced neurotoxicity threshold in hospitalized patients

OBJECTIVES

Cefepime-induced neurotoxicity (CIN) has been demonstrated to be associated with cefepime plasma concentrations; however, the toxicity threshold remains unclear. The primary objective of this study was to identify the cefepime plasma trough concentration at which neurotoxicity occurs. Secondary objectives were to determine the incidence of CIN at a large tertiary institution and to identify patient factors associated with the development of CIN.

METHODS

A retrospective review of all adult patients administered cefepime between October 2017 and May 2018 in a tertiary hospital was conducted to determine total incidence of CIN. A receiver operating characteristic (ROC) curve was constructed to review the sensitivity and specificity of using various cefepime trough plasma concentrations to predict the development of neurotoxicity. Cefepime plasma concentrations were measured using ultra-HPLC. A regression was conducted to identify patient factors associated with CIN.

RESULTS

In total, 206 patients were administered 259 courses of cefepime, with an overall CIN incidence of 6% (16/259 courses). A total of 64 courses had a cefepime trough concentration measured (24.7%). A cefepime trough concentration of 36 mg/L provided the best differentiation between patients who experienced neurotoxicity and those who did not. No other patient covariates were identified to be significantly associated with neurotoxicity occurring.

CONCLUSIONS

A cefepime trough plasma concentration ≥36 mg/L appears to be the most sensitive and specific cut-off to predict CIN occurring. No patient factors were associated with the development of CIN when accounting for cefepime trough plasma concentrations.

Concomitant Marked Decline in Prevalence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Other Respiratory Viruses Among Symptomatic Patients Following Public Health Interventions in Australia: Data from St Vincent's Hospital and Associated Screening Clinics, Sydney, NSW

Our Australian hospital tested almost 22,000 symptomatic people over 11 weeks for SARS-CoV-2 in a multiplex PCR assay. Following travel bans and physical distancing, SARS-CoV-2 and other respiratory viruses diagnoses fell dramatically. Increasing rhinovirus diagnoses as social control measures were relaxed may indirectly indicate an elevated risk of COVID-19 resurgence

Colonic malakoplakia in a dual stem cell and cardiac transplant recipient: A case report and literature review

We describe the first published case of malakoplakia in a dual stem cell and cardiac transplant recipient. In the 2 months following cardiac transplantation, our patient developed persistent diarrhea and recurrent E coli bacteremia. Biopsies obtained from areas of colonic thickening revealed malakoplakia. Despite improvement in symptoms with prolonged antimicrobial therapy and reduction of his immunosuppression, he eventually died from sepsis. Our case highlights not only the importance of the timely diagnosis of this rare disorder, but also the difficulty in determining optimal treatment duration, particularly where excision of involved areas is not possible, as data on this disease are lacking. Here we describe our case and review the available literature published on malakoplakia in the cardiac transplant population.

Antimicrobial therapeutic drug monitoring in critically ill adult patients: a Position Paper

Purpose

This Position Paper aims to review and discuss the available data on therapeutic drug monitoring (TDM) of antibacterials, antifungals and antivirals in critically ill adult patients in the intensive care unit (ICU). This Position Paper also provides a practical guide on how TDM can be applied in routine clinical practice to improve therapeutic outcomes in critically ill adult patients.

Methods

Literature review and analysis were performed by Panel Members nominated by the endorsing organisations, European Society of Intensive Care Medicine (ESICM), Pharmacokinetic/Pharmacodynamic and Critically Ill Patient Study Groups of European Society of Clinical Microbiology and Infectious Diseases (ESCMID), International Association for Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) and International Society of Antimicrobial Chemotherapy (ISAC). Panel members made recommendations for whether TDM should be applied clinically for different antimicrobials/classes.

Results

TDM-guided dosing has been shown to be clinically beneficial for aminoglycosides, voriconazole and ribavirin. For most common antibiotics and antifungals in the ICU, a clear therapeutic range has been established, and for these agents, routine TDM in critically ill patients appears meritorious. For the antivirals, research is needed to identify therapeutic targets and determine whether antiviral TDM is indeed meritorious in this patient population. The Panel Members recommend routine TDM to be performed for aminoglycosides, beta-lactam antibiotics, linezolid, teicoplanin, vancomycin and voriconazole in critically ill patients.

Conclusion

Although TDM should be the standard of care for most antimicrobials in every ICU, important barriers need to be addressed before routine TDM can be widely employed worldwide.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06050-1) contains supplementary material, which is available to authorized users.

How to design a study to evaluate therapeutic drug monitoring in infectious diseases?

BACKGROUND

Therapeutic drug monitoring (TDM) is a tool to personalize and optimize dosing by measuring the drug concentration and subsequently adjusting the dose to reach a target concentration or exposure. The evidence to support TDM is however often ranked as expert opinion. Limitations in study design and sample size have hampered definitive conclusions of the potential added value of TDM.

OBJECTIVES

We aim to give expert opinion and discuss the main points and limitations of available data from antibiotic TDM trials and emphasize key elements for consideration in design of future clinical studies to quantify the benefits of TDM.

SOURCES

The sources were peer-reviewed publications, guidelines and expert opinions from the field of TDM.

CONTENT

This review focuses on key aspects of antimicrobial TDM study design: describing the rationale for a TDM study, assessing the exposure of a drug, assessing susceptibility of pathogens and selecting appropriate clinical endpoints. Moreover we provide guidance on appropriate study design.

IMPLICATIONS

This is an overview of different aspects relevant for the conduct of a TDM study. We believe that this paper will help researchers and clinicians to design and conduct high-quality TDM studies.

Candidaemia and a risk predictive model for overall mortality: a prospective multicentre study

Background

Candidaemia is associated with high mortality. Variables associated with mortality have been published previously, but not developed into a risk predictive model for mortality. We sought to describe the current epidemiology of candidaemia in Australia, analyse predictors of 30-day all-cause mortality, and develop and validate a mortality risk predictive model.

Methods

Adults with candidaemia were studied prospectively over 12 months at eight institutions. Clinical and laboratory variables at time of blood culture-positivity were subject to multivariate analysis for association with 30-day all-cause mortality. A predictive score for mortality was examined by area under receiver operator characteristic curves and a historical data set was used for validation.

Results

The median age of 133 patients with candidaemia was 62 years; 76 (57%) were male and 57 (43%) were female. Co-morbidities included underlying haematologic malignancy (n = 20; 15%), and solid organ malignancy in (n = 25; 19%); 55 (41%) were in an intensive care unit (ICU). Non-albicans Candida spp. accounted for 61% of cases (81/133). All-cause 30-day mortality was 31%. A gastrointestinal or unknown source was associated with higher overall mortality than an intravascular or urologic source (p < 0.01). A risk predictive score based on age > 65 years, ICU admission, chronic organ dysfunction, preceding surgery within 30 days, haematological malignancy, source of candidaemia and antibiotic therapy for ≥10 days stratified patients into < 20% or ≥ 20% predicted mortality. The model retained accuracy when validated against a historical dataset (n = 741).

Conclusions

Mortality in patients with candidaemia remains high. A simple mortality risk predictive score stratifying patients with candidaemia into < 20% and ≥ 20% 30-day mortality is presented. This model uses information available at time of candidaemia diagnosis is easy to incorporate into decision support systems. Further validation of this model is warranted.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4065-5) contains supplementary material, which is available to authorized users.

Urinary piperacillin/tazobactam pharmacokinetics in vitro to determine the pharmacodynamic breakpoint for resistant Enterobacteriaceae

Urinary tract infections caused by multidrug-resistant Enterobacteriaceae are a growing burden worldwide. Recent studies of urinary pharmacokinetics described high piperacillin/tazobactam (TZP) concentrations in urine, but it is unknown whether this results in treatment efficacy. This study investigated the pharmacodynamics of TZP in a static in vitro model for Enterobacteriaceae to determine the concentration-effect relationship and ultimately the required free (unbound) time above the minimum inhibitory concentration (fT_>MIC) required for bacterial killing. The static simulation model investigated TZP fT_>MIC between 0% and 100%. Resistant Escherichia coli and Klebsiella pneumoniae isolates with piperacillin/tazobactam MICs of 4096/512, 1024/128 and 128/16 mg/L were investigated; two of the three organisms were carbapenemase-producers. Clinical efficacy was determined as a 3-log reduction over the dosing interval by comparing interval growth with controls. TZP was observed to exhibit time dependence for all organisms. The fT_>MIC was determined to be 37.5%, 37.5% and 50% for MICs of 4096/512, 1024/128 and 128/16 mg/L, respectively. Linear regression identified the overall target to be 49.85 ± 16.9% fT_>MIC. In conclusion, bactericidal activity against TZP-resistant Enterobacteriaceae occurred at 49.85 ± 16.9% fT_>MIC. This suggests that highly resistant urinary organisms, including carbapenemase-producers, with MICs up to 4096/512 mg/L could be treated with TZP. Further investigations are required to elucidate urinary breakpoints and to explore the impact of different resistance mechanisms.

Whole Genome Sequencing of Australian Candida glabrata Isolates Reveals Genetic Diversity and Novel Sequence Types

Candida glabrata is a pathogen with reduced susceptibility to azoles and echinocandins. Analysis by traditional multilocus sequence typing (MLST) has recognized an increasing number of sequence types (STs), which vary with geography. Little is known about STs of C. glabrata in Australia. Here, we utilized whole genome sequencing (WGS) to study the genetic diversity of 51 Australian C. glabrata isolates and sought associations between STs over two time periods (2002-2004, 2010-2017), and with susceptibility to fluconazole by principal component analysis (PCA). Antifungal susceptibility was determined using Sensititre YeastOne^TM Y010 methodology and WGS performed on the NextSeq 500 platform (Illumina) with in silico MLST STs inferred by WGS data. Single nucleotide polymorphisms (SNPs) in genes linked to echinocandin, azole and 5-fluorocytosine resistance were analyzed. Of 51 isolates, WGS identified 18 distinct STs including four novel STs (ST123, ST124, ST126, and ST127). Four STs accounted for 49% of isolates (ST3, 15.7%; ST83, 13.7%; ST7, 9.8%; ST26, 9.8%). Split-tree network analysis resolved isolates to terminal branches; many of these comprised multiple isolates from disparate geographic settings but four branches contained Australian isolates only. ST3 isolates were common in Europe, United States and now Australia, whilst ST8 and ST19, relatively frequent in the United States, were rare/absent amongst our isolates. There was no association between ST distribution (genomic similarity) and the two time periods or with fluconazole susceptibility. WGS identified mutations in the FKS1 (S629P) and FKS2 (S663P) genes in three, and one, echinocandin-resistant isolate(s), respectively. Both mutations confer phenotypic drug resistance. Twenty-five percent (13/51) of isolates were fluconazole-resistant (MIC ≥ 64 μg/ml) of which 9 (18%) had non wild-type MICs to voriconazole and posaconazole. Multiple SNPs were present in genes linked to azole resistance such as CgPDR1 and CgCDR1, as well as several in MSH2; however, SNPs occurred in both azole-susceptible and azole-resistant isolates. Although no particular SNP in these genes was definitively associated with resistance, azole-resistant/non-wild type isolates had a propensity to harbor SNPs resulting in amino acid substitutions in Pdr1 beyond the first 250 amino acid positions. The presence of SNPs may be markers of STs. Our study shows the value of WGS for high-resolution sequence typing of C. glabrata, discovery of novel STs and potential to monitor trends in genetic diversity. WGS assessment for echinocandin resistance augments phenotypic susceptibility testing.

Detection of Dientamoeba fragilis in animal faeces using species specific real time PCR assay

Dientamoeba fragilis is a potentially pathogenic, enteric, protozoan parasite with a worldwide distribution. While clinical case reports and prevalence studies appear regularly in the scientific literature, little attention has been paid to this parasite's biology, life cycle, host range, and possible transmission routes. Overall, these aspects of Dientamoeba biology remain poorly understood at best. In this study, a total of 420 animal samples, collected from Australia, were surveyed for the presence of Dientamoeba fragilis using PCR. Several PCR assays were evaluated for sensitivity and specificity. Two previously published PCR methods demonstrated cross reactivity with other trichomonads commonly found in animal samples. Only one assay exhibited excellent specificity. Using this assay D. fragilis was detected from one dog and one cat sample. This is the first report of D. fragilis from these animals and highlights the role companion animals may play in D. fragilis transmission. This study demonstrated that some published D. fragilis molecular assays cross react with other closely related trichomonads and consequently are not suitable for animal prevalence studies.

The Prevalence of Angiostrongylus cantonensis/mackerrasae Complex in Molluscs from the Sydney Region

Angiostrongylus cantonensis and Angiostrongylus mackerrasae are metastrongyloid nematodes that infect various rat species. Terrestrial and aquatic molluscs are intermediate hosts of these worms while humans and dogs are accidental hosts. Angiostrongylus cantonensis is the major cause of angiostrongyliasis, a disease characterised by eosinophilic meningitis. Although both A. cantonensis and A. mackerrasae are found in Australia, A. cantonensis appears to account for most infections in humans and animals. Due to the occurrence of several severe clinical cases in Sydney and Brisbane, the need for epidemiological studies on angiostrongyliasis in this region has become apparent. In the present study, a conventional PCR and a TaqMan assay were compared for their ability to amplify Angiostrongylus DNA from DNA extracted from molluscs. The TaqMan assay was more sensitive, capable of detecting the DNA equivalent to one hundredth of a nematode larva. Therefore, the TaqMan assay was used to screen molluscs (n=500) of 14 species collected from the Sydney region. Angiostrongylus DNA was detected in 2 of the 14 mollusc species; Cornu aspersum [14/312 (4.5%)], and Bradybaenia similaris [1/10 (10%)], which are non-native terrestrial snails commonly found in urban habitats. The prevalence of Angiostrongylus spp. was 3.0% ± 0.8% (CI 95%). Additionally, experimentally infected Austropeplea lessoni snails shed A. cantonensis larvae in their mucus, implicating mucus as a source of infection. This is the first Australian study to survey molluscs using real-time PCR and confirms that the garden snail, C. aspersum, is a common intermediate host for Angiostrongylus spp. in Sydney.

Anncaliia algerae microsporidial myositis

The insect microsporidian Anncaliia algerae was first described in 2004 as a cause of fatal myositis in an immunosuppressed person from Pennsylvania, USA. Two cases were subsequently reported, and we detail 2 additional cases, including the only nonfatal case. We reviewed all 5 case histories with respect to clinical characteristics, diagnosis, and management and summarized organism life cycle and epidemiology. Before infection, all case-patients were using immunosuppressive medications for rheumatoid arthritis or solid-organ transplantation. Four of the 5 case-patients were from Australia. All diagnoses were confirmed by skeletal muscle biopsy; however, peripheral nerves and other tissues may be infected. The surviving patient received albendazole and had a reduction of immunosuppressive medications and measures to prevent complications. Although insects are the natural hosts for A. algerae, human contact with water contaminated by spores may be a mode of transmission. A. algerae has emerged as a cause of myositis, particularly in coastal Australia.

Activity of benzimidazoles against Dientamoeba fragilis (Trichomonadida, Monocercomonadidae) in vitro and correlation of beta-tubulin sequences as an indicator of resistance

Recently, Dientamoeba fragilis has emerged as a significant and common enteropathogen. The majority of patients with dientamoebiasis present with gastrointestinal complaints and chronic symptoms are common. Numerous studies have successfully demonstrated parasite clearance, coupled with complete resolution of clinical symptoms following treatment with various antiparasitic compounds. Despite this, there is very little in vitro susceptibility data available for the organism. Benzimidazoles are a class of antiparasitic drugs that are commonly used for the treatment of protozoan and helminthic infections. Susceptibility testing was undertaken on four D. fragilis clinical isolates against the following benzimidazoles: albendazole, flubendazole, mebendazole, nocodazole, triclabendazole and thiabendazole. The activities of the antiprotozoal compounds at concentrations ranging from 2 μg/mL to 500 μg/mL were determined via cell counts of D. fragilis grown in xenic culture. All tested drugs showed no efficacy. The beta-tubulin transcript was sequenced from two of the D. fragilis isolates and amino acid sequences predicted a susceptibility to benzimidazoles. This is the first study to report susceptibility profiles for benzimidazoles against D. fragilis, all of which were not active against the organism. This study also found that beta-tubulin sequences cannot be used as a reliable marker for resistance of benzimidazoles in D. fragilis.

Miliary pulmonary cryptococcosis

A 32-year-old HIV positive male presents with fevers and a non-productive cough. Initial X-ray and subsequent computerised tomography of the chest shows a bilateral miliary pattern of pulmonary infiltration highly suggestive of disseminated tuberculosis. However subsequent results were consistent with disseminated cryptococcosis, including pulmonary involvement, with cryptococcus identified on transbronchial tissue biopsy, and on blood and cerebrospinal fluid cultures.

Imaging features of pulmonary cryptococcosis are generally of well-defined pleural-based nodules and less commonly alveolar infiltrates, lymphadenopathy, pleural effusions or cavitating lesions. Miliary pulmonary infiltrates are an exceptionally rare presentation.

Treatment failure in patients with chronic Blastocystis infection

This article reports long-term infection and treatment failure in 18 symptomatic individuals infected with Blastocystis spp. Patients were initially treated with either metronidazole, iodoquinol or triple combination therapy consisting of nitazoxanide, furazolidone and secnidazole. Following treatment, resolution of clinical symptoms did not occur and follow-up testing revealed ongoing infection with the same subtype. Patients then underwent secondary treatment with a variety of antimicrobial agents but remained symptomatic with Blastocystis spp. still present in faeces. Sequencing of the SSU rDNA was completed on all isolates and four subtypes were identified in this group: ST1, ST3, ST4 and ST5. This study highlights the lack of efficacy of several commonly used antimicrobial regimens in the treatment of Blastocystis and the chronic nature of some infections. It also demonstrates the need for further research into treatment options for Blastocystis infection.

Antifungal therapy and management of complications of cryptococcosis due to Cryptococcus gattii

BACKGROUND

We describe antifungal therapy and management of complications due to Cryptococcus gattii infection in 86 Australian patients followed for at least 12 months.

METHODS

Patient data from culture-confirmed cases (2000-2007) were recorded at diagnosis, 6 weeks, 6 months, and 12 months. Clinical, laboratory, and treatment variables associated with raised intracranial pressure (ICP) and immune reconstitution inflammatory syndrome (IRIS) were determined.

RESULTS

Seven of 10 patients with lung infection received amphotericin B (AMB) induction therapy (6 with 5-flucytosine [5-FC] for a median of 2 weeks); median duration of therapy including azole eradication therapy was 41 weeks, with a complete/partial clinical response in 78%. For neurologic disease, 88% of patients received AMB, 78% with 5-FC, for a median of 6 weeks. The median total course was 18 months. Nine patients receiving fluconazole induction therapy were reinduced with AMB plus 5-FC for clinical failure. Raised ICP (31 patients) was associated with initial abnormal neurology, and neurologic sequelae and/or death at 12 months (both P = .02); cerebrospinal fluid drains/shunts were placed in 58% of patients and in 64% of 22 patients with hydrocephalus. IRIS developed 2-12 months after starting antifungals in 8 patients, who presented with new/enlarging brain lesions. Risk factors included female sex, brain involvement at presentation, and higher median CD4 counts (all P < .05); corticosteroids reduced cryptococcoma-associated edema.

CONCLUSIONS

Induction AMB plus 5-FC is indicated for C. gattii neurologic cryptococcosis (6 weeks) and when localized to lung (2 weeks). Shunting was often required to control raised ICP. IRIS presents with cerebral manifestations.

Current treatment options for Dientamoeba fragilis infections

Dientamoeba fragilis belongs to the trichomonad group of protozoan parasites and it has been implicated as a cause of gastrointestinal disease with world-wide prevalences ranging from 0.5% to 16%. The majority of patients with dientamoebiasis present with gastrointestinal complaints. Chronic symptoms are common with up to a third of patients exhibiting persistent diarrhoea. Numerous studies have successfully demonstrated parasite clearance, coupled with complete resolution of clinical symptoms following treatment with various antiparasitic compounds. Treatments reported to be successful for dientamoebiasis include carbarsone, diphetarsone, tetracyclines, paromomycin, erythromycin, hydroxyquinolines and the 5-nitroimidazoles, including metronidazole, secnidazole, tinidazole and ornidazole. It is of note that most current treatment data is based only on small number of case reports. No large scale double blind randomised placebo controlled trials testing the efficacy of antimicrobial agents against D. fragilis has been undertaken highlighting the need for further study. In addition there is very little in vitro susceptibility data available for the organism making some current treatment options questionable. The aim of this review is to critically discuss all treatment options currently available for dientamoebiasis.

Clinical manifestations of Cryptococcus gattii infection: determinants of neurological sequelae and death

BACKGROUND

Longer-term morbidity and outcomes of Cryptococcus gattii infection are not described. We analyzed clinical, microbiological, and outcome data in Australian patients followed for 12 months, to identify prognostic determinants.

METHODS

Culture-confirmed C. gattii cases from 2000 to 2007 were retrospectively evaluated. Clinical, microbiological, radiological, and outcome data were recorded at diagnosis and at 6 weeks, 6 months, and 12 months. Clinical and laboratory variables associated with mortality and with death and/or neurological sequelae were determined.

RESULTS

Annual C. gattii infection incidence was 0.61 per 10(6) population. Sixty-two of 86 (72%) patients had no immunocompromise; 6 of 24 immunocompromised hosts had idiopathic CD4 lymphopenia, and 1 had human immunodeficiency virus/AIDS. Clinical and microbiological characteristics of infection were similar in immunocompromised and healthy hosts. Isolated lung, combined lung and central nervous system (CNS), and CNS only disease was reported in 12%, 51% and 34% of the cases, respectively. Complications in CNS disease included raised intracranial pressure (42%), hydrocephalus (30%), neurological deficits (27%; 6% developed during therapy) and immune reconstitutionlike syndrome (11%). Geometric mean serum cryptococcal antigen (CRAG) titers in CNS disease were 563.9 (vs 149.3 in isolated lung infection). Patient immunocompromise was associated with increased mortality risk. An initial cerebrospinal fluid CRAG titer of ≥256 predicted death and/or neurological sequelae (P = .05).

CONCLUSIONS

Neurological C. gattii disease predominates in the Australian endemic setting. Lumbar puncture and cerebral imaging, especially if serum CRAG titers are ≥512, are essential. Long-term follow up is required to detect late neurological complications. Immune system evaluation is important because host immunocompromise is associated with reduced survival.

Detection and transmission of Dientamoeba fragilis from environmental and household samples

Dientamoeba fragilis is a commonly occurring pathogenic protozoan often detected at higher rates in stool samples than Giardia intestinalis. However, little is known about its life cycle and mode of transmission. A total of 210 environmental and household samples were examined for the presence of D. fragilis by culture and polymerase chain reaction. Of 100 environmental samples, D. fragilis was detected only in untreated sewage. In the household samples D. fragilis was detected in 30% of household contacts tested and was not detected in any domestic pets. This study provides evidence that environmental transmission of D. fragilis is unlikely and that pets played no role in transmission of the disease in this study. Direct transmission from infected persons is the most likely mode of transmission for D. fragilis. The study also highlights the need for household contacts to be screened, given the propensity of close contacts to become infected with the organism.

Identification of novel hybrids between Cryptococcus neoformans var. grubii VNI and Cryptococcus gattii VGII

Cryptococcus neoformans and Cryptococcus gattii are pathogenic yeasts causing meningoencephalitis in immunocompromised and immunocompetent hosts. The fungus is typically haploid, and sexual reproduction occurs normally between individuals with opposite mating types, α and a. C. neoformans var. grubii (serotype A) is comprised of molecular types VNI, VNII, and VNB, and C. neoformans var. neoformans (serotype D) contains the molecular type VNIV. Additionally, diploid or aneuploid AD hybrids (VNIII) have been reported. C. gattii contains the molecular types VGI, VGII, VGIII, and VGIV, which encompass both serotypes B and C. To identify possible hybrid strains, URA5-RFLP analysis was performed on 350 globally obtained clinical, environmental, and veterinary isolates. Four clinical isolates from cerebrospinal fluid showed combination patterns of C. neoformans var. grubii and C. gattii: Brazil (n = 2), Colombia (n = 1), and India (n = 1). These strains were monokaryotic and diploid or aneuploid. M13 PCR fingerprinting showed that they contained fragments of both proposed parental groups. Luminex IGS genotyping identified these isolates as hybrids with two different molecular type combinations: three VNI/VGII and one VNI/VGI. Blue color development on CGB agar was delayed in three isolates and absent in one. C. gattii-specific PCR confirmed the presence of C. gattii in the hybrids. CAP59 allele-specific PCR revealed that all the hybrids contained both serotype A and B alleles. Determination of mating-type allelic patterns by PCR revealed that the isolates were αA aB. This is the first study discovering novel natural hybrids between C. neoformans molecular type VNI and C. gattii molecular type VGII.

A review of Dientamoeba fragilis carriage in humans: several reasons why this organism should be considered in the diagnosis of gastrointestinal illness

Dientamoeba fragilis is a protozoan that inhabits the human gut. It is approximately 100 years since Dientamoeba's discovery and first description when it was described as a rare and harmless commensal. Since then it has struggled to gain recognition as a pathogen despite the evidence supporting its pathogenicity. Dientamoeba remains neglected, probably due to the misconceptions that it is uncommon and non-pathogenic. Usually, carriage of Dientamoeba is associated with symptoms such as abdominal pain and diarrhea. Moreover, antimicrobial therapy followed by resolution of symptoms coincides with the eradication of Dientamoeba. This manuscript reviews the scientific literature relating to Dientamoeba's prevalence and pathogenicity. While much of the evidence supporting its pathogenicity is only circumstantial, it is apparent that most researchers agree that Dientamoeba is pathogenic. Therefore, in symptomatic patients who harbor Dientamoeba and no other pathogen, Dientamoeba should be considered as the etiological agent and treated as such.

Seroprevalence of Entamoeba histolytica infection among men who have sex with men in Sydney, Australia

A retrospective analysis was undertaken to determine the seroprevalence of Entamoeba histolytica infection in Sydney, Australia. Using an enzyme-linked immunosorbent assay, 429 high risk human immunodeficiency virus (HIV)-infected men who have sex with men (MSM), 446 low risk HIV-uninfected MSM, and 456 HIV-uninfected controls were assessed. Seroprevalence rates were 5.13% for the high risk HIV-infected MSM group, 0.22% for the low risk HIV-uninfected MSM group, and 0.44% for the control group. We found that high risk HIV-infected MSM have a significantly greater seroprevalence of E. histolytica with a relative risk of 22.87, when compared with low risk HIV-uninfected MSM and 11.69 when compared with controls. These findings show that in Sydney, sexually active HIV-infected MSM are at greater risk of developing amoebic disease caused by E. histolytica than HIV-uninfected MSM and the general population.

Importance of nonenteric protozoan infections in immunocompromised people

There are many neglected nonenteric protozoa able to cause serious morbidity and mortality in humans, particularly in the developing world. Diseases caused by certain protozoa are often more severe in the presence of HIV. While information regarding neglected tropical diseases caused by trypanosomatids and Plasmodium is abundant, these protozoa are often not a first consideration in Western countries where they are not endemic. As such, diagnostics may not be available in these regions. Due to global travel and immigration, this has become an increasing problem. Inversely, in certain parts of the world (particularly sub-Saharan Africa), the HIV problem is so severe that diseases like microsporidiosis and toxoplasmosis are common. In Western countries, due to the availability of highly active antiretroviral therapy (HAART), these diseases are infrequently encountered. While free-living amoebae are rarely encountered in a clinical setting, when infections do occur, they are often fatal. Rapid diagnosis and treatment are essential to the survival of patients infected with these organisms. This paper reviews information on the diagnosis and treatment of nonenteric protozoal diseases in immunocompromised people, with a focus on patients infected with HIV. The nonenteric microsporidia, some trypanosomatids, Toxoplasma spp., Neospora spp., some free-living amoebae, Plasmodium spp., and Babesia spp. are discussed.

A review of the clinical presentation of dientamoebiasis

Among 750 symptomatic and asymptomatic patients, Dientamoeba fragilis was detected at a prevalence of 5.2% and more common than Giardia intestinalis. Most infected patients presented with diarrhea and abdominal pain with symptoms greater than 2 weeks duration being common. Bacterial and viral causes of infection were excluded by routine microbiological techniques. Treatment of D. fragilis infection with either iodoquinol, paromomycin, or combination therapy resulted in the eradication of the parasite and complete resolution of symptoms. Treatment failure/relapses were associated only with the use of metronidazole. Nineteen patients were examined for pin worm, no Enterobius vermicularis, a proposed vector of transmission, were detected. Intermittent shedding of D. fragilis was found to be highly variable. These studies confirm the pathogenic nature of D. fragilis and we recommend laboratories routinely test for the organism.

Candidaemia in adult cancer patients: risks for fluconazole-resistant isolates and death

BACKGROUND

Candidaemia in cancer patients is associated with increasing fluconazole resistance. Models for predicting such isolates and their clinical impact are required.

METHODS

Clinical, treatment and outcome data from a population-based candidaemia survey (2001-2004) were collected at 5 and 30 days after diagnosis. Speciation and antifungal susceptibility testing was performed.

RESULTS

There were 138 candidaemia episodes (33% Candida albicans) in adults with haematological malignancies and 150 (51% C. albicans) in adults with solid organ malignancies. Thirty-nine isolates had fluconazole MICs of >or=64 mg/L and 40 had MICs of 16-32 mg/L (predominantly Candida glabrata and Candida krusei). By multivariate analysis, triazole therapy, gastrointestinal tract (GIT) surgery in the 30 days before candidaemia and age >65 years were predictive of fluconazole-resistant candidaemia. Thirty day crude mortality was 40% in haematology patients and 45% in oncology patients. Fluconazole-resistant isolates were associated with increased risk of mortality by univariate (P = 0.04) and Kaplan-Meier survival analyses. By Cox proportional hazards modelling, the strongest predictors of mortality at onset of candidaemia were invasive ventilation, elevated creatinine, intensive care unit (ICU) admission and receipt of systemic triazoles or corticosteroids in the previous 30 days. Removal of a central venous access device (CVAD) at or within 5 days of onset was associated with decreased mortality.

CONCLUSIONS

Risk factors for fluconazole-resistant candidaemia in adults with cancer include fluconazole/triazole exposure and GIT surgery. ICU admission, invasive ventilation, renal impairment, age >65 years and prior exposure to corticosteroids and triazoles are risk factors for death. CVAD removal reduced mortality. These findings should be integrated into surveillance and treatment algorithms.

Laryngeal cryptococcosis: Clinical presentation and treatment of a rare cause of hoarseness

Objective: Laryngeal cryptococcosis is rare, with few reported cases in the literature. We present current investigation and treatment recommendations for this disease.

Study Design: A structured literature review; additional cases and expert opinion are presented.

Results: Localized laryngeal cryptococcal infection most commonly presents with persisting hoarseness. Clinical suspicion of the disease is required for accurate diagnosis, with treatment based on the patient's immune status. Early microbiological advice and adequate follow-up is recommended to ensure disease resolution.

Conclusion: Isolated laryngeal cryptococcosis is a rare presentation of fungal infection. It is easily treated and should be considered in the differential diagnosis of patients with persisting hoarseness.

Repeated Dientamoeba fragilis infections: a case report of two families from Sydney, Australia

We report cases of two unrelated families who both presented with recurrent Dienta-moeba fragilis infections. Subsequent antimicrobial therapy resulted in the clearance of D. fragilis and total resolution of gastrointestinal symptoms in both families. This report highlights the potentially recurrent nature of D. fragilis infections and the need for laboratories to routinely test for this organism.

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

Repeated Dientamoeba fragilis infections: a case report of two families from Sydney, Australia

We report cases of two unrelated families who both presented with recurrent Dientamoeba fragilis infections. Subsequent antimicrobial therapy resulted in the clearance of D. fragilis and total resolution of gastrointestinal symptoms in both families. This report highlights the potentially recurrent nature of D. fragilis infections and the need for laboratories to routinely test for this organism.

Candidaemia with uncommon Candida species: predisposing factors, outcome, antifungal susceptibility, and implications for management

The risk factors for and clinical features of bloodstream infection with uncommon Candida spp. (species other than C. albicans, C. glabrata, C. parapsilosis, C. tropicals and C. krusei) are incompletely defined. To identify clinical variables associated with these species that might guide management, 57 cases of candidaemia resulting from uncommon Candida spp. were analysed in comparison with 517 episodes of Candida albicans candidaemia (2001-2004). Infection with uncommon Candida spp. (5.3% of candidaemia cases), as compared with C. albicans candidaemia, was significantly more likely to be outpatient-acquired than inpatient-acquired (15 of 57 vs. 65 of 517 episodes, p 0.01). Prior exposure to fluconazole was uncommon (n=1). Candida dubliniensis was the commonest species (n=22, 39%), followed by Candida guilliermondii (n=11, 19%) and Candida lusitaniae (n=7, 12%).C. dubliniensis candidaemia was independently associated with recent intravenous drug use (p 0.01) and chronic liver disease (p 0.03), and infection with species other than C. dubliniensis was independently associated with age<65 years (p 0.02), male sex (p 0.03) and human immunodeficiency virus infection (p 0.05). Presence of sepsis at diagnosis and crude 30-day mortality rates were similar for C. dubliniensis-related, non-C. dubliniensis-related and C. albicans-related candidaemia. Haematological malignancy was the commonest predisposing factor in C. guilliermondii (n=3, 27%) and C. lusitaniae (n=3, 43%) candidaemia. The 30-day mortality rate of C. lusitaniae candidaemia was higher than the overall death rate for all uncommon Candida spp. (42.9% vs. 25%, p not significant). All isolates were susceptible to amphotericin B, voriconazole, posaconazole, and caspofungin; five strains (9%) had fluconazole MIC values of 16-32 mg/L. Candidaemia due to uncommon Candida spp. is emerging among hospital outpatients; certain clinical variables may assist in recognition of this entity.

Not just little adults: candidemia epidemiology, molecular characterization, and antifungal susceptibility in neonatal and pediatric patients

OBJECTIVE

The purpose of this work was to identify differences in incidence, risk factors, microbiology, treatment, and clinical outcome of candidemia in neonates, children, and adults that might impact on management.

PATIENTS AND METHODS

Cases of candidemia in Australia were identified prospectively by blood culture surveillance over 3 years. Episodes of candidemia in neonatal, pediatric, and adult age groups were analyzed and compared.

RESULTS

Of 1005 incident cases, 33 occurred in neonates, 110 in children, and 862 in adults. The respective annual age-specific incidences were 4.4, 0.9, and 1.8 per 100,000 population. Prematurity and ICU admission were major risk factors in neonates. Hematologic malignancy and neutropenia were significantly more frequent in children than in neonates and adults. Diabetes, renal disease, hemodialysis, and recent surgery were more common in adults. Candidemia was attributed to a vascular access device in 58% of neonates, 70% of children, and 44% of adults. Candida albicans caused approximately 48% of cases in all of the age groups. Candida parapsilosis was significantly more common in neonates and children (42% and 38% vs 15%). Candida glabrata was infrequent in neonates and children (9% and 3% vs 17%). Significantly more isolates from children were susceptible to fluconazole compared with those from adults (95% vs 75%). Fluconazole-resistant candidal isolates were infrequent in all of the age groups. Neonates and children were more likely to receive amphotericin B compared with adults. Adults were more likely to receive fluconazole. Survival rates at 30 days were 78% in neonates, 90% in children, and 70% in adults.

CONCLUSIONS

This study identifies significant differences in candidemia in neonates, children, and adults. Neonatologists and pediatricians must consider age-specific differences when interpreting adult studies and developing treatment and prevention guidelines.

Limited genetic diversity among genotypes of Enterocytozoon bieneusi strains isolated from HIV-infected patients from Sydney, Australia

Microsporidia are intracellular parasites, with over 1200 species belonging to 143 genera described to date. They are opportunistic pathogens in humans and can cause chronic diarrhoea in immunosuppressed patients. Both Enterocytozoon bieneusi and Encephalitozoon intestinalis cause intestinal disease, with Enterocytozoon bieneusi more commonly identified in patients with human immunodeficiency virus (HIV) infection. In this study, intestinal microsporidial clinical isolates from patients in Sydney, Australia, were genotyped. All specimens were from HIV-infected men with low CD4(+) T-cell counts (<100 cells mm(-3)). Genotyping of the internal transcribed spacer regions of the rRNA gene showed the presence of only one genotype, the anthroponotic Enterocytozoon bieneusi genotype B strain. This study thus highlighted the limited genetic diversity among Australian Enterocytozoon bieneusi isolates, and it is hypothesized that, due to the reduced incidence of microsporidia and the subsequent reduction in the human reservoir of the anthroponotic genotype B, locally acquired intestinal microsporidiosis will rarely be seen in HIV-infected persons undergoing highly active antiretroviral therapy in the future in Australia.