Potential role of salivary lactic acid bacteria in pathogenesis of oral lichen planus.

BACKGROUND: Emerging evidence emphasized the role of oral microbiome in oral lichen planus (OLP). To date, no dominant pathogenic bacteria have been identified consistently. It is noteworthy that a decreased abundance of Streptococcus, a member of lactic acid bacteria (LAB) in OLP patients has been commonly reported, indicating its possible effect on OLP. This study aims to investigate the composition of LAB genera in OLP patients by high-throughput sequencing, and to explore the possible relationship between them. METHODS: We collected saliva samples from patients with OLP (n = 21) and healthy controls (n = 22) and performed 16 S rRNA gene high-throughput sequencing. In addition, the abundance of LAB genera was comprehensively analyzed and compared between OLP and HC group. To verify the expression of Lactococcus lactis, real time PCR was conducted in buccal mucosa swab from another 14 patients with OLP and 10 HC. Furthermore, the correlation was conducted between clinical severity of OLP and LAB. RESULTS: OLP and HC groups showed similar community richness and diversity. The members of LAB, Lactococcus and Lactococcus lactis significantly decreased in saliva of OLP cases and negatively associated with OLP severity. In addition, Lactococcus and Lactococcus lactis showed negative relationship with Fusobacterium and Aggregatibacter, which were considered as potential pathogens of OLP. Similarly, compared with healthy controls, the amount of Lactococcus lactis in mucosa lesion of OLP patients was significantly decreased. CONCLUSIONS: A lower amount of Lactococcus at genus level, Lactococcus lactis at species level was observed in OLP cases and associated with disease severity. Further studies to verify the relationship between LAB and OLP, as well as to explore the precise mechanism is needed.

Helicobacter pylori infection is correlated with the incidence of erosive oral lichen planus and the alteration of the oral microbiome composition.

BACKGROUND: Oral lichen planus (OLP), a common clinical oral disease, is associated with an increased risk of malignant transformation. The mechanism underlying the pathogenesis of OLP is unknown. Oral dysbacteriosis is reported to be one of the aetiological factors of OLP. Although Helicobacter pylori infection is associated with various oral diseases, the correlation between H. pylori infection and OLP is unclear. This study aimed to investigate the effect of H. pylori infection on OLP pathogenesis and oral microbiome composition in the Chinese population, which has a high incidence of H. pylori infection. RESULT: In this study, saliva samples of 30 patients with OLP (OLP group) and 21 negative controls (NC group) were collected. H. pylori infection was detected using the carbon-13-labeled urea breath test (UBT). The saliva samples were divided into the following four groups based on the H. pylori status: H. pylori-positive OLP (OLP+), H. pylori-positive NC (NC+), H. pylori-negative OLP (OLP-), and H. pylori-negative NC (NC-). Oral microbiome compositions were significantly different between the OLP and NC groups and between the OLP- and OLP+ groups. Compared with those in the OLP- group, those in the OLP+ group had a higher incidence of erosive OLP and higher levels of salivary cytokines. In contrast, the oral microbiome composition and cytokine levels were not significantly different between the NC- and NC+ groups. CONCLUSIONS: This is the first report to demonstrate that H. pylori infection is significantly correlated with the pathogenesis of erosive OLP.

Oral lichen planus: a microbiologist point of view.

Oral lichen planus (OLP) is a chronic disease of uncertain etiology, although it is generally considered as an immune-mediated disease that affects the mucous membranes and even the skin and nails. Over the years, this disease was attributed to a variety of causes, including different types of microorganisms. This review analyzes the present state of the art of the disease, from a microbiological point of view, while considering whether or not the possibility of a microbial origin for the disease can be supported. From the evidence presented here, OLP should be considered an immunological disease, as it was initially proposed, as opposed to an illness of microbiological origin. The different microorganisms so far described as putative disease-causing agents do not fulfill Koch's postulates; they are, actually, not the cause, but a result of the disease that provides the right circumstances for microbial colonization. This means that, at this stage, and unless new data becomes available, no microorganism can be envisaged as the causative agent of lichen planus.

Hypha essential genes in Candida albicans pathogenesis of oral lichen planus: an in-vitro study.

BACKGROUND: Hypha essential genes (HEGs) of Candida Albicans have been emerging into scholar's attention, little known about their functions in oral lichen planus (OLP) with an uncovered etiology. This research aimed to observe necessary genes in biphasic C. albicans from OLP and study their relevance in pathogenesis, so as to evaluate possible roles of morphologic switching in etiology of OLP. METHODS: Samples were collected from OLP lesions of patients, mycelia were cultured and total RNA was extracted then subjected to reverse transcription-PCR and real-time PCR. RESULTS: HWP1 and HGC1 were significantly expressed in hyphae phase and weakly detected in yeast phase, while there was no significant difference of EFG1, ALS3, and ECE1 between in yeast and mycelia. CONCLUSION: HGC1 and HWP1 were confirmed to be hypha essential genes, with HGC1 for hypha morphogenesis and HWP1 for adhesion invasion in pathogenesis of C. albicans in OLP. ALS3, ECE1 and EFG1 played minor roles in hyphae maintenance and adhesion for hyphae. These might be deemed as hints for the etiology of OLP and indicate HGC1 and HWP1 to be a priority of potential drug target.

Dysbiosis of saliva microbiome in patients with oral lichen planus.

BACKGROUND: Oral microbiota is not only important for maintaining oral health but also plays a role in various oral diseases. However, studies regarding microbiome changes in oral lichen planus (OLP) are very limited. To the best of our knowledge, there has been only two studies investigating salivary microbiome changes in OLP. Therefore, the purpose of this study was to identify the characteristic microbial profile in the saliva of OLP patients, with or without erosive lesions, and compare that with recurrent aphthous ulcer (RAU), a common oral immunological disorder that also shows multiple erosive/ulcerative lesions. Whole saliva samples were collected from 20 patients with OLP (erosive E, n = 10 and non-erosive NE, n = 10), 10 patients with RAU (U) and 10 healthy controls (C). DNA was extracted from the saliva samples, and the 16S rDNA gene V4 hypervariable region was analyzed using Illumina sequencing. RESULTS: We obtained 4949 operational taxonomic units (OTUs) from the V4 region in all saliva samples. Community composition analysis showed a clear decreased relative abundance of genera Streptococcus and Sphingomonas in saliva from RAU patients when compared to the other three groups. Relative abundance of Lautropia and Gemella were higher in E group, whereas relative abundance of Haemophilus and Neisseria were higher in NE group when compared to C group. Abiotrophia and Oribacterium were higher in OLP (combining E and NE groups), while Eikenella and Aggregatibacter were lower when compared to C group. There was statistically significance in α-diversity between E and RAU groups(p < 0.05). Significant differences in ß-diversity were detected in bacteria between E and C; NE and C; as well as E and NE groups. The LDA effect size algorithm identified the g_Haemophilus might be the potential biomarker in NE group. CONCLUSIONS: We found that salivary microbiome in erosive OLP was significantly different from that found in RAU; and these changes may be related to the underlying disease process rather than presence of ulcerative/erosive lesions clinically. In addition, our findings in bacterial relative abundance in OLP were significantly different from the previously reported findings, which points to the need for further research in salivary microbiome of OLP.

Omega-3 polyunsaturated fatty acids: a promising approach for the management of oral lichen planus.

BACKGROUND: Oral lichen planus (OLP) is a T-cell-mediated inflammatory disease with a risk of malignant transformation. Although the etiology of OLP is still uncertain, growing evidence suggests that oral microbiota, antigen-specific, and non-specific mechanisms are involved in the pathogenesis of OLP. Antigen-specific mechanisms include antigen presentation, T-cell activation, nuclear factor-kappa B signaling pathway, and cytokine secretion, while non-specific mechanisms consist of matrix metalloproteinases (MMP)-9 upregulation, psychological pressure, oxidative damage, aberrant expression of microRNAs (miRNAs), and autophagy. Till now, there is no cure for OLP, and the main purpose of OLP therapy is symptomatic control. FINDING: Seafood and its derivative omega-3 polyunsaturated fatty acids (n-3 PUFAs) can suppress antigen presentation, T-cell activation, and nuclear factor-kappa B signaling pathway, modulate the overexpressed inflammatory cytokines, inhibit the expression of MMP-9, as well as regulate the expression of miRNAs and autophagy. And they are possible agents for ameliorating psychological disorder and oxidative damage. Moreover, n-3 PUFAs supplementation has a beneficial effect on preventing tumorigenesis. CONCLUSION: n-3 PUFAs consumption may provide a non-toxic, inexpensive administration for OLP.

Potential association between Fusobacterium nucleatum enrichment on oral mucosal surface and oral lichen planus.

OBJECTIVE: We determined the bacterial community structure of the buccal mucosa in patients with oral lichen planus (OLP) and evaluated the potential association of Fusobacterium nucleatum with OLP. SUBJECTS AND METHODS: We collected buccal mucosal swab samples of patients with OLP (n = 20) and healthy controls (n = 10) and performed 16S rRNA gene sequencing and real-time PCR to determine potentially different bacteria. Damaged and adjacent non-damaged mucosal swab samples of 25 OLP patients were used to detect the amount of F. nucleatum by real-time PCR. RESULTS: Compared with healthy controls, enrichment of Fusobacterium and Granulicatella was more abundant in patients with OLP (p = .0146 and 0.0034). The abundance of Fusobacterium and F. nucleatum was significantly enriched on buccal mucosa of patients with OLP compared with healthy controls (p = .0043 and 0.0235). Compared with adjacent non-damaged buccal mucosa of OLP patients, the amount of F. nucleatum in the damaged mucosa was significantly increased (p = .001). We examined third-level KEGG pathways for bacteria on mucosal surface and found that genes controlling sporulation and ether lipid metabolism were enriched in patients with OLP. CONCLUSIONS: A high amount of F. nucleatum may be associated with OLP. Further studies are required to investigate the precise association of F. nucleatum with OLP.

A pilot study: a possible implication of Candida as an etiologically endogenous pathogen for oral lichen planus.

BACKGROUND: The aim of this study was to investigate the prevalence and genotypic profiles of Candida albicans in patients with oral lichen planus (OLP). MATERIALS AND METHODS: Positive rates and genotypic profiles of Candida albicans strains from OLP patients and healthy controls were analyzed. Random amplified polymorphic DNA and internal transcribed spacer of ribosome DNA polymerase chain reactions were used to sequence the DNA of these strains, and then their genetic similarity was measured using BLAST, UIV Band, and Vector NTI Suite Sequence Analyses Software. RESULTS: The prevalence of C. albicans strains detected from erosive-OLP, non-erosive OLP, and normal individuals was 18.87, 18.75, and 7.92%, respectively. Four different genotypes were revealed by the two methods. To be specific, type I was found only in the healthy subjects; type II a and II b were found in non-erosive OLP, and type III was identified in erosive OLP. Intragroup similarity coefficients, i.e. SAB were 100%, and inter-groups similarity coefficients, i.e. SAB were less than 30%. CONCLUSIONS: The genotypic results of C. albicans in OLP revealed an endogenous rather than exogenous infection of C. albicans. In addition, a possible pathogenic role of C. albicans in OLP, with the etiologic sense contributing to a more proper recognition on the pathogenesis, development, and progression of OLP, as well as some strategies for its diagnosis and treatment were identified.

The oral microbiome in oral lichen planus during a 1-year randomized clinical trial.

BACKGROUND: Several recent studies have investigated the oral bacteriome in oral lichen planus (OLP), but longitudinal changes in microbiome have not been investigated. OBJECTIVE: To study the bacteriome and mycobiome in OLP over a 1-year period and the impact of topical treatment. MATERIAL AND METHODS: Samples from 22 symptomatic OLP patients from a double-blinded, randomized intervention study were collected over a 1-year course at five visits. Bacterial and fungal abundances were investigated through lesional cytobrush (CB) and full mouthwash (MW). Initially, all patients received conventional (antimycotic or steroid) and probiotic or placebo treatment. RESULTS: The microbial composition differed between the MW and CB samples. During the study period, the microbial composition was individual, with pronounced variability between visits. Patients grouped according to initial conventional treatment. During the study period, unidirectional change in the bacteriome was seen in the antimycotic group, whereas the mycobiome was stable. Malassezia restricta was the most abundant fungus. CONCLUSIONS: The microbial composition of MW and CB differs in OLP. CB composition is less influenced by conventional and probiotic intervention. Initial antimycotic treatment influenced the bacteriome during the 1-year period. How the oral microbiome in health and disease is influenced by individual variability of fungi and bacteria, and Malassezia needs further investigation.

Candida species in patients with oral dysesthesia: A comparison of carriage among oral disease states.

OBJECTIVES: Oral dysesthesia (burning mouth syndrome) is characterized by a burning-like sensation of the oral mucosa. The etiology of this disorder is still unknown, however, associations with oral fungal carriage have been proposed and applied clinically. The aim of the this study was to compare oral Candida carriage in patients with oral dysesthesia with Candida carriage in patients with other commonly diagnosed oral diseases to clarify the relationship between Candida and oral dysesthesia. SUBJECTS AND METHODS: In total, 441 patients in total including 79 patients diagnosed with oral dysesthesia were included in this study. A retrospective analysis of mycological investigations undertaken in patients with clinically diagnosed oral dysesthesia compared with other oral conditions was undertaken. RESULTS: Oral carriage of Candida was found in 63.3% (50 of 79) of patients with oral dysesthesia. The frequency of carriage and oral load of Candida were not significantly increased in patients with oral dysesthesia relative to the other conditions assessed. Patients with clinical signs of fungal infection or xerostomia presented with increased carriage of Candida. CONCLUSION: There is no association between oral dysesthesia and the presence or load of oral Candida.

Oral lichen-planus-associated fibroblasts acquire myofibroblast characteristics and secrete pro-inflammatory cytokines in response to Porphyromonas gingivalis lipopolysaccharide stimulation.

BACKGROUND: Oral lichen planus (OLP) is a chronic inflammatory oral mucosal disease in which comprehensive inflammation-related cytokines are involved. These cytokines are commonly produced by immune cells and specific nonimmune cells including keratinocytes, endothelial cells and fibroblasts. This raises the question of whether fibroblasts in OLP lesions contribute to the inflammatory process upon inflammatory simulation. METHODS: Primary cultured Oral lichen-planus-associated fibroblasts (OLP AFs, n = 5) and normal buccal mucosal fibroblasts (NFs, n = 5) were examined by immunohistochemistry, Western blotting and reverse transcription-polymerase chain reactions (RT-PCR). Various inflammatory mediators were evaluated with a multiplex assay. Differences among groups were assessed using a Student's test or repeated measures one-way ANOVA, as appropriate. RESULTS: OLP AFs express significantly higher levels of α-smooth muscle actin (α-SMA) than NFs, indicating the presence of myofibroblasts. Myofibroblasts secrete Interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) in response to Porphyromonas gingivalis lipopolysaccharide (pg. LPS). CONCLUSION: OLP AFs demonstrated α-SMA expression and secreted pro-inflammatory cytokines in response to pg. LPS stimulation.

Immunohistochemical detection of Mycoplasma salivarium in oral lichen planus tissue.

BACKGROUND: Oral lichen planus (OLP) is a T-cell-mediated inflammatory disease; however, its exact etiology is unknown. Hyperkeratosis is often observed in OLP lesions. Previous studies have revealed the localization of Mycoplasma salivarium in the epithelial cells of oral leukoplakia with hyperkeratosis. Herein, we investigated the presence of M. salivarium in OLP tissue by immunohistochemistry to determine the causative factor of OLP. METHODS: Forty-one formalin-fixed, paraffin-embedded samples obtained from 31 patients with OLP were examined. Ten samples of normal-appearing oral mucosa were used as controls. Immunohistochemistry (IHC) was performed using anti-M. salivarium monoclonal antibodies. RESULTS AND CONCLUSIONS: Mycoplasma salivarium was detected in the epithelium and lymphocyte infiltrate area in 24 of 41 OLP samples (58.5%). The bacteria were intracellularly localized in epithelial cells, while it was unclear whether they were also localized in lymphocyte cells or in the extracellular spaces among the lymphocytes in the subepithelial lymphocyte infiltrate area. Little or no staining was observed in the epithelium in the normal-appearing mucosa samples. Sawtooth rete ridge formation was observed in 21 OLP samples (51.2%), and a significant positive correlation between sawtooth rete ridge formation and IHC positivity was demonstrated. However, the role of M. salivarium in the epithelium and lamina propria of OLP tissue remains unknown.

Dysbiosis of oral buccal mucosa microbiota in patients with oral lichen planus.

OBJECTIVE: The bacterial community structure of buccal mucosa in patients with oral lichen planus was evaluated and compared with healthy control. SUBJECTS AND METHODS: Buccal scraping samples have been taken on 43 oral lichen planus patients (21 erosive and 22 non-erosive) and 21 mucosal healthy volunteers. The V3 hypervariable 16S rDNA region was amplified and sequenced by high-throughput 454 pyrosequencing. RESULTS: 94.26% of the total buccal bacteria were classified into 15 abundant genera. Eight of these abundant genera could be detected in all cases, namely Streptococcus, Prevotella, Haemophilu, Neisseria, Fusobacterium, Leptotrichia, Veillonella and Actinomyces. Four abundant bacteria showed significantly different prevalence at the genus level: Streptococcus was more abundant (P < 0.01) in healthy control group, while Fusobacterium (P < 0.01), Leptotrichia (P < 0.001) and Lautropia (P < 0.001) showed higher abundance in OLP group. Few differences can be found between erosive and non-erosive OLP. In general, 19 'core' OTUs at three levels were defined to be OLP specific, comparing with healthy control group. CONCLUSIONS: These results suggest that OLP is associated with dysbiosis of the oral microbiome. Further studies should be taken to elucidate the inner relationship between these observed changes and OLP development.

Analysis of oral microbial community and Th17-associated cytokines in saliva of patients with oral lichen planus.

Oral lichen planus (OLP) is a chronic inflammatory disorder of oral mucosa of unknown cause. Microbial infection and dysimmunity appear to play important roles in its pathogenesis. In this study, differences in genetic profiling of salivary microbial communities in two subtypes of OLP and healthy controls were evaluated by means of PCR-denaturing gradient gel electrophoresis (DGGE). Additionally, ELISA was used to investigate the possible role of Th17 in lesion formation by detecting two related cytokines IL-17 and IL-23 in the saliva of OLP patients. When the DGGE profiles were analyzed, the bacterial populations were found to be significantly less rich in subjects with reticular and erosive OLP than in healthy controls. There was significantly less microbial diversity, as denoted by the Shannon index, in saliva samples from subjects with erosive OLP than in those from healthy controls. Cluster analysis and principal component analysis showed that the DGGE profiles formed distinctly group-specific clusters. Salivary concentrations of IL-17 in subjects with erosive OLP group were significantly higher than in those with reticular OLP and healthy controls. What's more, significantly positive correlations were observed between salivary IL-17 concentrations and disease clinical scores. Microbial richness and diversity was negatively correlated with salivary IL-17 concentrations. These results suggest there is significantly less salivary bacterial diversity and complexity in subjects with OLP han in healthy controls and that the shifted community composition is closely related to an immune cytokine, IL-17.

No evidence for Helicobacter pylori in oral lichen planus.

OBJECTIVES: Oral lichen planus is a T-cell-mediated mucosal disease of unknown etiology. Numerous predisposing factors have been put forward in the etiology of this disease. This includes stress, drugs, genetic susceptibility, certain viruses, and bacterial infections. Recently, there have been studies published on possible role of Helicobacter pylori infection in pathogenesis of mucocutaneous diseases including oral lichen planus (OLP). The aim of this study was to detect immunohistochemically the presence of Helicobacter pylori in oral lichen planus. MATERIALS AND METHODS: Paraffin-embedded tissue blocks of 50 cases of OLP and 10 cases of normal buccal mucosal biopsies and 6 endoscopic biopsies of patients with peptic ulcer (control group) were sectioned and stained by hematoxylin and eosin. Serial sections of same were stained immunohistochemically using Anti-Helicobacter pylori antibody and observed under microscope for presence or absence of Helicobacter pylori. RESULTS: Except for the control group, none of the cases of OLP and normal buccal mucosal biopsies showed positivity for Helicobacter pylori. CONCLUSION: As we did not detect the presence of Helicobacter pylori in any of the OLP cases, we question the role of these organisms in the pathogenesis of OLP planus if any.

Prevalence of Candida spp., xerostomia, and hyposalivation in oral lichen planus--a controlled study.

OBJECTIVE: To determine the frequency of Candida spp., xerostomia, and salivary flow rate (SFR) in three different groups: patients with OLP (OLP group), patients with oral mucosal lesions other than OLP (non-OLP group), and subjects without oral mucosal lesions (control group). MATERIAL AND METHODS: Xerostomia as well as SFR was investigated in the three groups. Samples for isolation of Candida spp. were collected from OLP lesions (38 patients), non-OLP lesions (28 patients), and healthy subjects (32 subjects). RESULTS: There was no statistically significant difference regarding the frequency of xerostomia and hyposalivation among the three groups (P > 0.05). A higher prevalence for colonization by Candida spp. was found in the healthy subject as compared to that of patients with OLP (P = 0.03) and non-OLP (P = 0.02) groups. Low SFR was not a factor for colonization by Candida spp. CONCLUSIONS: Xerostomia and hyposalivation occur with similar frequency in subjects with and without oral lesions; also, the presence of oral lesions does not increase the susceptibility to colonization by Candida spp. It seems that any study implicating Candida spp. in the malignant transformation of oral lesions should be carried out mostly on a biochemical basis, that is, by testing the capability of Candida spp. to produce carcinogenic enzyme.

[T-cells immunity in oral lichen planus pathogenesis].

In this review the modern ideas of the cell-like immune pathogenesis mechanism of Lichen planus)LP) are described. The special attention is paid to molecular diagnostics methods ( immunohistochemical and others). Communication of emergence of oral LP with infectious diseases is shown.

Production of carcinogenic acetaldehyde by Candida albicans from patients with potentially malignant oral mucosal disorders.

OBJECTIVES: Production of carcinogenic acetaldehyde by Candida has been suggested to contribute to epithelial dysplasia and oral carcinogenesis. Oral lichen planus (OLP), oral lichenoid lesion (OLL) and oral leukoplakia (OL) are potentially carcinogenic oral diseases where colonisation by Candida is common, but acetaldehyde production by Candida has not been studied. STUDY DESIGN: Acetaldehyde production in ethanol (11 mM), glucose (100 mM), ethanol-glucose (11 mM and 100 mM) or red wine (1200 mM ethanol) incubation by Candida albicans from patients with OLL (n = 6), OLP (n = 16), OL (n = 6) and controls (n = 6) was measured by gas chromatography. Participants completed a questionnaire regarding their smoking habits and alcohol consumption. RESULTS: All Candida albicans isolates produced potentially carcinogenic levels of acetaldehyde (>100 µM) in all incubations containing ethanol. The control group isolates produced the highest acetaldehyde levels. Isolates from smokers produced more acetaldehyde in all incubations than those from non-smokers. The difference was significant in ethanol-glucose incubation. Isolates from patients who were both smokers and drinkers produced the highest amounts when incubated in ethanol, ethanol-glucose and wine. CONCLUSIONS: Candida albicans isolated from potentially carcinogenic oral diseases can produce mutagenic amounts of acetaldehyde. Cigarette smoking and alcohol consumption may favour adaptational changes resulting in the upregulation of candidal acetaldehyde metabolism.

Unstimulated whole salivary flow rate and anxiolytics intake are independently associated with oral Candida infection in patients with oral lichen planus.

Many factors have been proposed to influence oral infection with yeast. The aim of this study was to determine the prevalence of oral yeasts in oral lichen planus (OLP) patients and control subjects, and to perform a multiple logistic regression analysis to identify factors that influence oral Candida infection in OLP patients. In this cross-sectional study, 90 new patients with OLP and 90 sex- and age-matched control subjects with no mucosal lesions were interviewed about their health status, use of medication, and smoking and alcohol habits. Swab and unstimulated whole saliva samples were collected and salivary pH was measured. A positive Candida culture was more prevalent among OLP patients (48.9%) than among control subjects (26.7%). Candida albicans was the most frequently isolated species in both groups. By logistic regression analysis, unstimulated whole salivary flow rates of 0.11-0.24 ml min(-1) (OR = 5.90) and 0.25-0.32 ml min(-1) (OR = 3.51) and benzodiazepine anxiolytics intake (OR = 8.30) were independently associated with the presence of Candida among OLP patients. Age, denture wearing, levels of dentition, decreased salivary pH, antihypertensive drugs, and alcohol consumption were not associated with oral Candida infection in OLP patients. The results indicate that data on benzodiazepine anxiolytics intake and evaluation of unstimulated whole salivary flow rate should be considered as part of the clinical evaluation to identify OLP patients at risk for Candida infection.