Hospital-acquired candidemia in HIV-infected patients. Incidence, risk factors and predictors of outcome

The burden of hospital-acquired infections (HAI) in sub-Saharan Africa: a systematic review and meta-analysis

Background

Hospital-acquired infections (HAI) are a leading cause of morbidity and mortality globally. These infections are diverse, but the majority are lower respiratory tract infection (LRTI), surgical site infection (SSI), bloodstream infection (BSI), and urinary tract infection (UTI). For most sub-Saharan African countries, studies revealing the burden and impact of HAI are scarce, and few systematic reviews and meta-analysis have been attempted. We sought to fill this gap by reporting recent trends in HAI in sub-Saharan Africa (SSA) with attention to key patient populations, geographic variation, and associated mortality.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a literature search of six electronic databases (Web of Science, Pubmed, APA PsycInfo, CINAHL, Embase, and the Cochrane Library) to identify studies assessing the prevalence of HAI in SSA countries. Studies published between 01 January 2014 and 31 December 2023 were included. We applied no language or publication restrictions. Record screening and data extractions were independently conducted by teams of two or more reviewers. Using the R software (version 4.3.1) meta and metafor packages, we calculated the pooled prevalence estimates from random-effect meta-analysis, and further explored sources of heterogeneity through subgroup analyses and meta-regression. This study is registered with PROSPERO, CRD42023433271.

Findings

Forty-one relevant studies were identified for analysis, consisting of 15 from West Africa (n = 2107), 12 from Southern Africa (n = 2963), 11 from East Africa (n = 2142), and 3 from Central Africa (n = 124). A total of 59.4% of the patient population were associated with paediatric admissions. The pooled prevalence of HAI was estimated at 12.9% (95% CI: 8.9-17.4; n = 7336; number of included estimates [k] = 41, p < 0.001). By subregions, the pooled current prevalence of HAI in the West Africa, Southern Africa, East Africa and Central Africa were estimated at 15.5% (95% CI: 8.3-24.4; n = 2107; k = 15), 6.5% (95% CI: 3.3-10.7; n = 2963; k = 12), 19.7% (95% CI: 10.8-30.5; n = 2142; k = 11) and 10.3% (95% CI: 1.1-27.0; n = 124; k = 3) of the patient populations respectively. We estimated mortality resulting from HAI in SSA at 22.2% (95% CI: 14.2-31.4; n = 1118; k = 9).

Interpretation

Our estimates reveal a high burden of HAI in SSA with significant heterogeneity between regions. Variations in HAI distribution highlight the need for infection prevention and surveillance strategies specifically tailored to enhance prevention and management with special focus on West and East Africa, as part of the broader global control effort.

Funding

No funding was received for this study.

When Is It Appropriate to Take Off the Mask? Signaling Pathways That Regulate ß(1,3)-Glucan Exposure in Candida albicans

Candida spp. are an important source of systemic and mucosal infections in immune compromised populations. However, drug resistance or toxicity has put limits on the efficacy of current antifungals. The C. albicans cell wall is considered a good therapeutic target due to its roles in viability and fungal pathogenicity. One potential method for improving antifungal strategies could be to enhance the detection of fungal cell wall antigens by host immune cells. ß(1,3)-glucan, which is an important component of fungal cell walls, is a highly immunogenic epitope. Consequently, multiple host pattern recognition receptors, such as dectin-1, complement receptor 3 (CR3), and the ephrin type A receptor A (EphA2) are capable of recognizing exposed (unmasked) ß(1,3)-glucan moieties on the cell surface to initiate an anti-fungal immune response. However, ß(1,3)-glucan is normally covered (masked) by a layer of glycosylated proteins on the outer surface of the cell wall, hiding it from immune detection. In order to better understand possible mechanisms of unmasking ß(1,3)-glucan, we must develop a deeper comprehension of the pathways driving this phenotype. In this review, we describe the medical importance of ß(1,3)-glucan exposure in anti-fungal immunity, and highlight environmental stimuli and stressors encountered within the host that are capable of inducing changes in the levels of surface exposed ß(1,3)-glucan. Furthermore, particular focus is placed on how signal transduction cascades regulate changes in ß(1,3)-glucan exposure, as understanding the role that these pathways have in mediating this phenotype will be critical for future therapeutic development.

HIV Infection as Risk Factor for Death among Hospitalized Persons with Candidemia, South Africa, 2012-2017

HIV-seropositive persons demonstrated increased adjusted risk for 30-day mortality and should be evaluated for intensive care.

We determined the effect of HIV infection on deaths among persons >18 months of age with culture-confirmed candidemia at 29 sentinel hospitals in South Africa during 2012–2017. Of 1,040 case-patients with documented HIV status and in-hospital survival data, 426 (41%) were HIV-seropositive. The in-hospital case-fatality rate was 54% (228/426) for HIV-seropositive participants and 37% (230/614) for HIV-seronegative participants (crude odds ratio [OR] 1.92, 95% CI 1.50–2.47; p<0.001). After adjusting for relevant confounders (n = 907), mortality rates were 1.89 (95% CI 1.38–2.60) times higher among HIV-seropositive participants than HIV-seronegative participants (p<0.001). Compared with HIV-seronegative persons, the stratum-specific adjusted mortality OR was higher among HIV-seropositive persons not managed in intensive care units (OR 2.27, 95% CI 1.47–3.52; p<0.001) than among persons who were (OR 1.56, 95% CI 1.00–2.43; p = 0.05). Outcomes among HIV-seropositive persons with candidemia might be improved with intensive care.

A Potential Antifungal Effect of Chitosan Against Candida albicans Is Mediated via the Inhibition of SAGA Complex Component Expression and the Subsequent Alteration of Cell Surface Integrity

Due to the high incidence of nosocomial Candida albicans infection, the first-line drugs for C. albicans infection have been heavily used, and the emergence of drug-resistant strains has gradually increased. Thus, a new antifungal drug or therapeutic method is needed. Chitosan, a product of chitin deacetylation, is considered to be potentially therapeutic for fungal infections because of its excellent biocompatibility, biodegradability and low toxicity. The biocidal action of chitosan against C. albicans shows great commercial potential, but the exact mechanisms underlying its antimicrobial activity are unclear. To reveal these mechanisms, mutant library screening was performed. ADA2 gene, which encodes a histone acetylation coactivator in the SAGA complex, was identified. Transmission electronic microscopy images showed that the surface of chitosan-treated ada2Δ cells was substantially disrupted and displayed an irregular morphology. Interestingly, the cell wall of ada2Δ cells was significantly thinner than that of wild-type cells, with a thickness similar to that seen in the chitosan-treated wild-type strain. Although ADA2 is required for chitosan tolerance, expression of ADA2 and several Ada2-mediated cell wall-related genes (ALS2, PGA45, and ACE2) and efflux transporter genes (MDR1 and CDR1) were significantly inhibited by chitosan. Furthermore, GCN5 encoding a SAGA complex catalytic subunit was inhibited by chitosan, and gcn5Δ cells exhibited phenotypes comparable to those of ada2Δ cells in response to chitosan and other cell surface-disrupting agents. This study demonstrated that a potential antifungal mechanism of chitosan against C. albicans operates by inhibiting SAGA complex gene expression, which decreases the protection of the cell surface against chitosan.

Systemic hematogenous dissemination of mouse oral candidiasis is induced by oral mucositis

The causes of fungemia include immunosuppression and neutropenia stemming from diverse factors as well as the placement of central venous catheters. However, the relationship between fungemia and the oral cavity has not been substantiated. In this study, we explored the pathological conditions of Candida albicans—derived oral candidiasis in a mouse model, which always develops oral mucositis as a complication. In oral candidiasis, the hyphae of C. albicans are believed to primarily invade the stratum granulosum, but not the subepithelium, of the mucous membrane. We provide histological evidence that in concomitant oral mucositis, the hyphae infiltrate the subepithelium and blood vessels. Blood cultures and tissue samples revealed the onset of fungemia only in the mucositis-induced groups. Positive numbers of colony-forming units were found in groups A (chemotherapy), B (chemotherapy + mucositis) and C (mucositis), but were highest in group B. Some organs revealed positive CFU in groups B and C. The presence of fungal DNA in blood plasma and tissue was confirmed by PCR. The fungal DNA frequency was significantly higher in the mucositis group when compared with the non-mucositis group. The results suggest that fungi first invade the subepithelium and then the blood vessels, from which they disseminate throughout the body, and that oral mucositis is an important risk factor for fungemia. This study clearly demonstrates the relationship between oral mucositis, fungemia, and the potential systemic fungal dissemination, which has not been previously proven. Our findings highlight the importance of oral care for patients at risk of fungemia.

Bloodstream infections in HIV-infected patients

In the combined antiretroviral therapy era, HIV-infected patients remain a vulnerable population for the onset of bloodstream infections (BSI). Worldwide, nontyphoid salmonellae, Streptococcus pneumoniae, Escherichia coli, Staphylococcus aureus and coagulase negative staphylococci are the most important pathogens. Intravenous catheter associated infection, skin-soft tissue infection and endocarditis are associated with Gram-positive bacteremia. Among the Gram-negative, nontyphoidal Salmonella have been previously correlated to sepsis. Other causes of BSI in HIV-infected patients are mycobacteria and fungi. Mycobacteria constitute a major cause of BSI in limited resource countries. Fungal BSI are not frequent and among them Cryptococcus neoformans is the most common life-threatening infection. The degree of immunosuppression remains the key prognostic factor leading to the development of BSI.

Risk factors, clinical presentation and prognosis of mixed candidaemia: a population-based surveillance in Spain

The low incidence of mixed candidaemia (MC) may have precluded a better knowledge of its clinical presentation. The aim of the study was to analyse the risk factors, clinical presentation and prognosis of MC episodes. A comparison between MC and monomicrobial candidaemia within a prospective programme on candidaemia was performed in 29 hospitals between April 2010 and May 2011. In fifteen episodes of candidaemia corresponding to 15 patients, out of 752, two species of Candida (1.9%) were isolated. MC was more frequent in patients with HIV infection (12%, P = 0.038) and those admitted due to extensive burns (23%, P = 0.012). The Candida species most frequently identified in MC were C. albicans 12 patients (40%), C. glabrata seven patients (23.3%) and C. parapsilosis six patients (20%). Early mortality was higher (nine patients, 60%) in patients with MC than in patients with MMC (223 patients, 30.3%, P = 0.046). In conclusion, MC was was independently associated with increased mortality even after considering other prognostic factors. MC is an infrequent event that is more common in HIV infection and in patients suffering from burns, and is associated with increased mortality.

Clinical characteristics and outcomes in 303 HIV-infected patients with invasive fungal infections: data from the Prospective Antifungal Therapy Alliance registry, a multicenter, observational study

This analysis aimed to characterize the epidemiology, diagnosis, treatment, and outcomes of invasive fungal infections (IFIs) in patients with human immunodeficiency virus (HIV). Data were examined for HIV patients enrolled in the Prospective Antifungal Therapy (PATH) Alliance registry, a multicenter, observational study of patients with IFIs in North America from 2004 to 2008. Patient demographics, clinical characteristics, comorbidities, antifungal therapies, and survival were assessed. In total, 320 fungal isolates were identified from 303 HIV patients with IFIs in the PATH Alliance® registry. These included Cryptococcus (50.0%), Candida (33.1%), Histoplasma (9.1%), and Aspergillus (4.4%). Candida infection occurred mainly as candidemia (86.0%); Cryptococcus as central nervous system infection (76.7%); Histoplasma as disseminated infection (74.1%); and Aspergillus as pulmonary infection (81.8%). The CD4 cell count was ≤200 cells/μL in 91.2% of patients with available data. The majority of patients with Cryptococcus (77.9%), Histoplasma (100.0%), and Aspergillus (71.4%) infections had CD4 cell counts <50 cells/μL compared with 48.9% of patients with Candida infections. Patients with candidiasis were more likely to have other conditions requiring medical services compared with patients with other IFIs. Survival probability was lower in patients with Aspergillus (0.58) and Candida (0.59) infection than in patients with Histoplasma (0.84) and Cryptococcus (0.81) infection. In the highly active antiretroviral therapy era, traditional opportunistic IFIs such as cryptococcosis and histoplasmosis still mainly occur in HIV patients with CD4 counts <50 cells/μL. Fungal infections remain a clinical challenge in HIV patients with severe immunosuppression. Our data also suggest that HIV patients with CD4 cell counts >200 cells/μL and other underlying conditions may be susceptible to invasive candidiasis.

Candidacidal effects of Rev (11-20) derived from HIV-1 Rev protein

Rev is an essential regulatory protein for HIV-1 replication. Rev (11-20) is known as the significant region regarding the function of a nuclear entry inhibitory signal (NIS) of Rev. In this study, anticandidal effects and mechanism of action of Rev (11-20) were investigated. The result exhibited that Rev (11-20) contained candidacidal activities. To understand target site(s) of Rev (11-20), the intracellular localization of the peptide was investigated. The result showed that Rev (11-20) rapidly accumulated in the fungal cell surface. The cell wall regeneration test also indicated that Rev (11-20) exerted its anticandidal activity to fungal plasma membrane rather than cell wall. The fluorescent study using 1,6-diphenyl-1,3,5-hexatriene (DPH) further confirmed the membrane-disruption mechanism(s) of Rev (11-20). The present study suggests that Rev (11-20) possesses significant potential regarding therapeutic agents for treating fungal diseases caused by Candida species in humans.

Host defense mechanisms in invasive candidiasis originating in the GI tract

Candida spp. rank among the leading causative agents of nosocomial infections. The increasing number of patients at risk of invasive candidiasis makes a rise in the incidence of this fungal infection expected. Disruption of GI tract integrity and ablation of immune cell populations, such as those resulting from cancer chemotherapy, are recognized as key factors leading to fungal dissemination. However, the individual role of these immune barriers in preventing Candida host colonization and invasion are yet to be fully understood. This article evaluates recently published results on a new murine model of systemic candidiasis originating in the GI tract that might prove a valuable setting for the accurate study of host immune mechanisms, fungal virulence factors and novel therapeutic approaches.

Amino acid residues affecting drug pump function in Candida albicans--C. albicans drug pump function

Membrane-located drug transporters are important components in the multidrug resistance of microbial cells and human tissues. In fungi, clinically important resistance to antifungal drugs most often results from the over-expression of efflux pump proteins in the plasma membrane of the resistant cell. This review describes studies of the ATP binding cassette (ABC) family of membrane efflux pumps in the opportunistic human pathogen Candida albicans and, in particular, examines how changes in the polypeptide sequence can affect pump function. The identification of amino acid residues affecting pump function can provide new insights into efflux pump mechanisms and the relationship between structure and function. Such information will be important for the design of pump inhibitors which could supplement existing antifungal drugs.

Once-weekly micafungin therapy is as effective as daily therapy for disseminated candidiasis in mice with persistent neutropenia

The effect of micafungin dose scheduling on the treatment of candidemia is unknown. Neutropenic mice with disseminated Candida glabrata infection were treated with single intraperitoneal micafungin doses of 0 to 100 mg/kg of body weight and sacrificed 7 days later. The maximal decline in kidney fungal burden was 5.8 log(10) CFU/g. A 1-week pharmacokinetic-pharmacodynamic study revealed a micafungin serum half-life of 6.13 h. In mice treated with > or =50 mg/kg, there was maximal fungal decline without regrowth during the 1-week dosing interval. Next, doses associated with 34% (34% effective dose [ED(34)]) and 50% (ED(50)) of maximal kill were administered at one of three dose schedules: a single dose at t = 0, two equal doses at t = 0 and t = 3.5 days, and 7 equal doses daily. Some mice received a single dose of 100 mg/kg. Fungal burden was examined on days 1, 5, and 7. In mice treated with the ED(34), microbial kill with the daily therapy initially lagged behind the intermittent doses but exceeded it by day 7. In mice treated with the ED(50), daily and intermittent doses had equivalent day 7 effects. In mice treated with 100 mg/kg, there was no regrowth. The relative likelihoods that the area under the concentration-time curve/MIC ratio was linked to microbial kill versus peak concentration/MIC ratio or time above the MIC was 10.3 and 10,161.2, respectively. In all the experiments, no paradoxical increase in fungal burden was observed with high micafungin doses. However, only a single Candida isolate was tested. Regimens that simulated micafungin concentration-time profiles in patients treated with a single micafungin dose of 1,400 mg once a week demonstrated maximal fungal decline. Once-weekly micafungin therapy is as efficacious as daily therapy in a murine model of disseminated candidiasis.

Critical role of Bcr1-dependent adhesins in C. albicans biofilm formation in vitro and in vivo

The fungal pathogen Candida albicans is frequently associated with catheter-based infections because of its ability to form resilient biofilms. Prior studies have shown that the transcription factor Bcr1 governs biofilm formation in an in vitro catheter model. However, the mechanistic role of the Bcr1 pathway and its relationship to biofilm formation in vivo are unknown. Our studies of biofilm formation in vitro indicate that the surface protein Als3, a known adhesin, is a key target under Bcr1 control. We show that an als3/als3 mutant is biofilm-defective in vitro, and that ALS3 overexpression rescues the biofilm defect of the bcr1/bcr1 mutant. We extend these findings with an in vivo venous catheter model. The bcr1/bcr1 mutant is unable to populate the catheter surface, though its virulence suggests that it has no growth defect in vivo. ALS3 overexpression rescues the bcr1/bcr1 biofilm defect in vivo, thus arguing that Als3 is a pivotal Bcr1 target in this setting. Surprisingly, the als3/als3 mutant forms a biofilm in vivo, and we suggest that additional Bcr1 targets compensate for the Als3 defect in vivo. Indeed, overexpression of Bcr1 targets ALS1, ECE1, and HWP1 partially restores biofilm formation in a bcr1/bcr1 mutant background in vitro, though these genes are not required for biofilm formation in vitro. Our findings demonstrate that the Bcr1 pathway functions in vivo to promote biofilm formation, and that Als3-mediated adherence is a fundamental property under Bcr1 control. Known adhesins Als1 and Hwp1 also contribute to biofilm formation, as does the novel protein Ece1.

The formation of biofilms (surface-attached microbial communities) on implanted medical devices such as catheters is a major cause of fungal and bacterial infections. Prior studies of the fungal pathogen Candida albicans have shown that the regulator Bcr1 is required for biofilm formation in vitro, but the mechanism through which it promotes biofilm formation and its significance for biofilm formation in vivo was uncertain. The authors demonstrate that Bcr1 is required for biofilm formation in vivo in a rat model of catheter-based infection. Manipulation of Bcr1 target genes through mutation and gene overexpression shows that the known surface adhesin Als3 has a pivotal role in biofilm formation and that adhesins Als1 and Hwp1 also contribute to biofilm formation. The results thus indicate that adherence is the key property regulated by Bcr1 and highlight a group of adhesins as potential therapeutic targets.

Changing face of health-care associated fungal infections

PURPOSE OF REVIEW

The purpose of this review was to evaluate recent publications on the epidemiology, diagnosis and management of invasive fungal infections.

RECENT FINDINGS

Epidemiological surveys have highlighted significant differences between Europe and the United States regarding the incidence and etiology of Candida bloodstream infections. Today, invasive aspergillosis is occurring in a much broader patient population than the classical immunocompromised hosts and includes mechanically ventilated intensive care unit patients and patients receiving corticosteroids for treatment of chronic lung diseases. Diagnosis is often delayed in these patients and prognosis is dismal. Measurement of galactomannan, mannan and antimannan antibodies, and beta-(1-3)-D-glucan may help to speed up diagnosis. The epidemiology of invasive mold infections is changing. The frequency of non-fumigatus Aspergillus species is increasing, uncommon hyalo-or phaeo-hyphomycoses are emerging and breakthrough mold infections intrinsically resistant to azoles have been reported. Clinical trials have shown that new azoles and echinocandins are as efficacious as amphotericin B or fluconazole for the treatment of eosophageal or invasive candidiasis, for prophylaxis of invasive fungal infections in transplant patients, or for empirical antifungal therapy in patients with persistent fever and neutropenia.

SUMMARY

Recent data suggest that the epidemiology of invasive fungal infections may be changing with the emergence of uncommon molds and the occurrence of invasive aspergillosis in 'nonclassical' immunocompromised hosts. New diagnostic tools and improved antifungal agents are available to facilitate early diagnosis and offer new treatment options.