Unilateral periocular spasm.

ABSTRACT: Hemifacial spasm is an uncontrollable, recurrent facial muscular contraction that typically occurs on one side of the face, cannot be suppressed, and can last the entire day and during sleep. The most common underlying cause of facial nerve compression is an enlarged or abnormal tracking blood vessel at the brainstem level. Clinical diagnoses are frequently based on a patient's medical history and physical examination. Before deciding on a course of action, however, an electromyogram and MRI are performed to determine the underlying cause. Due to its high effectiveness (success rates of 85% to 95%) and low frequency of adverse reactions, botulinum toxin is the preferred therapy for hemifacial spasm and can provide transient symptomatic alleviation. Surgical microvascular decompression is a therapeutic approach that targets the underlying cause of this condition and has an average success rate of 85%.

The subgingival microbiome in patients with established rheumatoid arthritis.

OBJECTIVES: To profile and compare the subgingival microbiome of RA patients with OA controls. METHODS: RA (n = 260) and OA (n = 296) patients underwent full-mouth examination and subgingival samples were collected. Bacterial DNA was profiled using 16 S rRNA Illumina sequencing. Following data filtering and normalization, hierarchical clustering analysis was used to group samples. Multivariable regression was used to examine associations of patient factors with membership in the two largest clusters. Differential abundance between RA and OA was examined using voom method and linear modelling with empirical Bayes moderation (Linear Models for Microarray Analysis, limma), accounting for the effects of periodontitis, race, marital status and smoking. RESULTS: Alpha diversity indices were similar in RA and OA after accounting for periodontitis. After filtering, 286 taxa were available for analysis. Samples grouped into one of seven clusters with membership sizes of 324, 223, 3, 2, 2, 1 and 1 patients, respectively. RA-OA status was not associated with cluster membership. Factors associated with cluster 1 (vs 2) membership included periodontitis, smoking, marital status and Caucasian race. Accounting for periodontitis, 10 taxa (3.5% of those examined) were in lower abundance in RA than OA. There were no associations between lower abundance taxa or other select taxa examined with RA autoantibody concentrations. CONCLUSION: Leveraging data from a large case-control study and accounting for multiple factors known to influence oral health status, results from this study failed to identify a subgingival microbial fingerprint that could reliably discriminate RA from OA patients.

Dysbiosis and alterations in predicted functions of the subgingival microbiome in chronic periodontitis.

Chronic periodontitis is an inflammatory disease of the periodontium affecting nearly 65 million adults in the United States. Changes in subgingival microbiota have long been associated with chronic periodontitis. Recent culture-independent molecular studies have revealed the immense richness and complexity of oral microbial communities. However, data sets across studies have not been directly compared, and whether the observed microbial variations are consistent across different studies is not known. Here, we used 16S rRNA sequencing to survey the subgingival microbiota in 25 subjects with chronic periodontal disease and 25 healthy controls and compared our data sets with those of three previously reported microbiome studies. Consistent with data from previous studies, our results demonstrate a significantly altered microbial community structure with decreased heterogeneity in periodontal disease. Comparison with data from three previously reported studies revealed that subgingival microbiota clustered by study. However, differences between periodontal health and disease were larger than the technical variations across studies. Using a prediction score and applying five different distance metrics, we observed two predominant clusters. One cluster was driven by Fusobacterium and Porphyromonas and was associated with clinically apparent periodontitis, and the second cluster was dominated by Rothia and Streptococcus in the majority of healthy sites. The predicted functional capabilities of the periodontitis microbiome were significantly altered. Genes involved in bacterial motility, energy metabolism, and lipopolysaccharide biosynthesis were overrepresented in periodontal disease, whereas genes associated with transporters, the phosphotransferase system, transcription factors, amino acid biosynthesis, and glycolysis/gluconeogenesis were enriched in healthy controls. These results demonstrate significant alterations in microbial composition and function in periodontitis and suggest genes and metabolic pathways associated with periodontal disease.

Smoking-induced subgingival dysbiosis precedes clinical signs of periodontal disease.

Smoking accelerates periodontal disease and alters the subgingival microbiome. However, the relationship between smoking-associated subgingival dysbiosis and progression of periodontal disease is not well understood. Here, we sampled 233 subgingival sites longitudinally from 8 smokers and 9 non-smokers over 6-12 months, analyzing 804 subgingival plaque samples using 16 rRNA sequencing. At equal probing depths, the microbial richness and diversity of the subgingival microbiome was higher in smokers compared to non-smokers, but these differences decreased as probing depths increased. The overall subgingival microbiome of smokers differed significantly from non-smokers at equal probing depths, which was characterized by colonization of novel minority microbes and a shift in abundant members of the microbiome to resemble periodontally diseased communities enriched with pathogenic bacteria. Temporal analysis showed that microbiome in shallow sites were less stable than deeper sites, but temporal stability of the microbiome was not significantly affected by smoking status or scaling and root planing. We identified 7 taxa-Olsenella sp., Streptococcus cristatus, Streptococcus pneumoniae, Streptococcus parasanguinis, Prevotella sp., Alloprevotella sp., and a Bacteroidales sp. that were significantly associated with progression of periodontal disease. Taken together, these results suggest that subgingival dysbiosis in smokers precedes clinical signs of periodontal disease, and support the hypothesis that smoking accelerates subgingival dysbiosis to facilitate periodontal disease progression.

Comparison of the virulence of exopolysaccharide-producing Prevotella intermedia to exopolysaccharide non-producing periodontopathic organisms.

BACKGROUND: Evidence in the literature suggests that exopolysaccharides (EPS) produced by bacterial cells are essential for the expression of virulence in these organisms. Secreted EPSs form the framework in which microbial biofilms are built. METHODS: This study evaluates the role of EPS in Prevotella intermedia for the expression of virulence. This evaluation was accomplished by comparing EPS-producing P. intermedia strains 17 and OD1-16 with non-producing P. intermedia ATCC 25611 and Porphyromonas gingivalis strains ATCC 33277, 381 and W83 for their ability to induce abscess formation in mice and evade phagocytosis. RESULTS: EPS-producing P. intermedia strains 17 and OD1-16 induced highly noticeable abscess lesions in mice at 107 colony-forming units (CFU). In comparison, P. intermedia ATCC 25611 and P. gingivalis ATCC 33277, 381 and W83, which all lacked the ability to produce viscous materials, required 100-fold more bacteria (109 CFU) in order to induce detectable abscess lesions in mice. Regarding antiphagocytic activity, P. intermedia strains 17 and OD1-16 were rarely internalized by human polymorphonuclear leukocytes, but other strains were readily engulfed and detected in the phagosomes of these phagocytes. CONCLUSIONS: These results demonstrate that the production of EPS by P. intermedia strains 17 and OD1-16 could contribute to the pathogenicity of this organism by conferring their ability to evade the host's innate defence response.

Stability of healthy subgingival microbiome across space and time.

The subgingival microbiome is one of the most stable microbial ecosystems in the human body. Alterations in the subgingival microbiome have been associated with periodontal disease, but their variations over time and between different subgingival sites in periodontally healthy individuals have not been well described. We performed extensive, longitudinal sampling of the subgingival microbiome from five periodontally healthy individuals to define baseline spatial and temporal variations. A total of 251 subgingival samples from 5 subjects were collected over 6-12 months and deep sequenced. The overall microbial diversity and composition differed significantly between individuals. Within each individual, we observed considerable differences in microbiome composition between different subgingival sites. However, for a given site, the microbiome was remarkably stable over time, and this stability was associated with increased microbial diversity but was inversely correlated with the enrichment of putative periodontal pathogens. In contrast to microbiome composition, the predicted functional metagenome was similar across space and time, suggesting that periodontal health is associated with shared gene functions encoded by different microbiome consortia that are individualized. To our knowledge, this is one of the most detailed longitudinal analysis of the healthy subgingival microbiome to date that examined the longitudinal variability of different subgingival sites within individuals. These results suggest that a single measurement of the healthy subgingival microbiome at a given site can provide long term information of the microbial composition and functional potential, but sampling of each site is necessary to define the composition and community structure at individual subgingival sites.

Genetic analysis of mobile tetQ elements in oral Prevotella species.

Prevotella species are members of the bacterial oral flora and are opportunistic pathogens in polymicrobial infections of soft tissues. Antibiotic resistance to tetracyclines is common in these bacteria, and the gene encoding this resistance has been previously identified as tetQ. The tetQ gene is also found on conjugative transposons in the intestinal Bacteroides species; whether these related bacteria have transmitted tetQ to Prevotella is unknown. In this study, we describe our genetic analysis of mobile tetQ elements in oral Prevotella species. Our results indicate that the mobile elements encoding tetQ in oral species are distinct from those found in the Bacteroides. The intestinal bacteria may act as a reservoir for the tetQ gene, but Prevotella has incorporated this gene into an IS21-family transposon. This transposon is present in Prevotella species from more than one geographical location, implying that the mechanism of tetQ spread between oral Prevotella species is highly conserved.

Gene expression profile and pathogenicity of biofilm-forming Prevotella intermedia strain 17.

BACKGROUND: Prevotella intermedia (P. intermedia), a gram-negative, black-pigmented anaerobic rod, has been implicated in the development of chronic oral infection. P. intermedia strain 17 was isolated from a chronic periodontitis lesion in our laboratory and described as a viscous material producing strain. The stock cultures of this strain still maintain the ability to produce large amounts of viscous materials in the spent culture media and form biofilm-like structures. Chemical analyses of this viscous material showed that they were mainly composed of neutral sugars with mannose constituting 83% of the polysaccharides. To examine the biological effect of the extracellular viscous materials, we identified and obtained a naturally-occurring variant strain that lacked the ability to produce viscous materials in vitro from our stock culture collections of strain 17, designated as 17-2. We compared these two strains (strains 17 versus 17-2) in terms of their capacities to form biofilms and to induce abscess formation in mice as an indication of their pathogenicity. Further, gene expression profiles between these two strains in planktonic condition and gene expression patterns of strain 17 in solid and liquid cultures were also compared using microarray assays. RESULTS: Strain 17 induced greater abscess formation in mice as compared to that of the variant. Strain 17, but not 17-2 showed an ability to interfere with the phagocytic activity of human neutrophils. Expression of several genes which including those for heat shock proteins (DnaJ, DnaK, ClpB, GroEL and GroES) were up-regulated two to four-fold with statistical significance in biofilm-forming strain 17 as compared to the variant strain 17-2. Strain 17 in solid culture condition exhibited more than eight-fold up-regulated expression levels of several genes which including those for levanase, extracytoplasmic function-subfamily sigma factor (sigmaE; putative) and polysialic acid transport protein (KpsD), as compared to those of strain 17 in liquid culture media. CONCLUSION: These results demonstrate that the capacity to form biofilm in P. intermedia contribute to their resistance against host innate defence responses.

Matrix metalloproteinase levels in children with aggressive periodontitis.

BACKGROUND: Matrix metalloproteinases (MMPs) are a family of host-derived proteinases reported to mediate multiple functions associated with periodontal destruction and inflammation. Most of the existing data have been gathered from adults with chronic periodontitis. The purpose of this study was to determine the MMP levels in a cohort of African American children with and without aggressive periodontitis. METHODS: Gingival crevicular fluid (GCF) was collected in a cohort of 44 African American children, 7 to 19 years of age, with and without aggressive periodontitis (AgP) and compared to healthy unrelated children and to adults with chronic periodontitis (CP). GCF volume was determined with a calibrated gingival fluid meter. The samples were assayed for MMP-1, -2, -3, -8, -9, -12, and -13 using fluorimetric substrates. RESULTS: The MMP levels from diseased sites in the subjects with AgP were statistically higher (P <0.05) in almost all instances than those associated with the unrelated controls or with the subjects with CP. MMP-8 was significantly elevated in the diseased sites of the children with AgP relative to non-diseased sites in the same children (P = 0.002), as well as the siblings, non-diseased controls, and subjects with CP (P < or =0.0001). There was no positive correlation between probing depth and any MMP level. CONCLUSIONS: MMP levels were elevated in AgP sites relative to non-diseased sites in the same subjects, in siblings, and in unrelated controls. MMPs associated with the AgP sites in children were generally elevated compared to an adult cohort with a history of CP.

Modified-release subantimicrobial dose doxycycline enhances scaling and root planing in subjects with periodontal disease.

BACKGROUND: Previous studies showed that adjunctive subantimicrobial dose doxycycline (SDD; 20 mg, twice daily) provides significant clinical benefits to scaling and root planing (SRP). A modified-release SDD formulation containing 40 mg doxycycline (SDD-40) to be taken once daily has been developed. The aim of this study was to investigate the efficacy of SDD-40 when used as an adjunct to SRP for the treatment of periodontitis. METHODS: A 9-month, double-masked, randomized, placebo-controlled, multicenter study was conducted to test the efficacy of adjunctive SDD-40 in 266 subjects with periodontitis. Subjects were treated by SRP and randomized to receive SDD-40 or placebo for 9 months with evaluations at 3, 6, and 9 months. RESULTS: Adjunctive SDD-40 provided significantly greater clinical benefits than placebo at all time points. At month 9, at sites with baseline probing depths (PD) > or =6 mm, 72% to 76% of sites in the SDD-40 group demonstrated clinically significant PD reductions and clinical attachment level (CAL) gains > or =2 mm compared to 56% to 58% of sites in the placebo group (P <0.0001); 48% to 52% of sites in the SDD-40 group demonstrated PD reductions and CAL gains > or =3 mm compared to 32% of sites in the placebo group (P <0.0001). In moderate sites (baseline PD 4 to 6 mm), adjunctive SDD-40 provided significant clinical benefits compared to placebo for mean CAL (all time points: P <0.05), PD (3 months: P = 0.002; 6 and 9 months: P = 0.001), and bleeding on probing (BOP) (3 months: P <0.01; 6 months: P <0.02; 9 months: P <0.05). In deep sites (baseline PD > or =7 mm), SDD-40 provided significant benefits over control for mean CAL (3 months: P <0.05; 6 and 9 months: P <0.01), PD (all time points: P <0.001), and BOP (3 months: P <0.05; 6 months: not statistically significant; 9 months: P <0.05). Compliance with study medication was high (>92%) with no significant differences in adverse events between groups and no evidence of microbiologically significant changes or development of antibiotic resistance in the subgingival flora in either group. CONCLUSION: SDD-40 used as an adjunct to SRP resulted in significantly greater clinical benefits than SRP alone in the treatment of periodontitis.

Microbiologic changes following administration of locally delivered doxycycline in smokers: a 15-month follow-up.

BACKGROUND: Additional clinical benefits have been reported with the use of locally delivered antimicrobials in the treatment of smokers; however, long-term changes in the subgingival microbiota following the use of these drugs in smokers have not been documented. The aim of this study was to evaluate long-term microbiologic changes following locally delivered doxycycline in the treatment of smokers. METHODS: Sixteen smokers with chronic periodontitis presenting a minimum of four pockets (probing depth>or=5 mm) were selected. Patients were assigned randomly to receive scaling and root planing (SRP) or SRP and local doxycycline (SRP-D). Patients were treated at baseline and 12 months. Subgingival plaque samples were collected at baseline; 3, 6, and 12 months; and 45 and 90 days following retreatment. Polymerase chain reaction and DNA-DNA hybridization analyses were performed to detect the presence of selected periodontal pathogens. RESULTS: The reduction in the number of sites positive for Porphyromonas gingivalis and Tannerella forsythia (previously T. forsythensis) was statistically significant for SRP-D at 3 months (68% and 41.3%, respectively) and for SRP at 6 months (75% and 52%, respectively) following treatment. The SRP group showed a greater frequency of P. gingivalis than the SRP-D group at 3 months (58% and 25%, respectively). There also was a greater reduction in the frequency of P. gingivalis at 3 months following retreatment with SRP-D compared to SRP (47% and 8%, respectively). CONCLUSION: In smokers, adjunctive local doxycycline resulted in a greater reduction in the frequency of P. gingivalis following initial and supportive therapy compared to conventional treatment.

Subantimicrobial dose doxycycline effects on osteopenic bone loss: microbiologic results.

BACKGROUND: Based on microbiologic concerns, the safety of a 24-month regimen of subantimicrobial dose doxycycline (SDD; 20 mg twice a day) was evaluated in postmenopausal osteopenic women with periodontitis in a double-blind, placebo-controlled, randomized clinical trial. METHODS: Subgingival samples were collected from two sites (probing depth > or = 5 mm) in each of 128 subjects at baseline, with the same sites resampled at the conclusion of the 2-year period. The samples were enumerated on selective and non-selective media and on doxycycline (4 microg/ml) medium. Up to five different colonial morphologies were subcultured from the doxycycline medium, identified to species, and susceptibilities determined to doxycycline and five other antibiotics. Data were analyzed for microbial differences in total colony forming units (CFU), periodontal and opportunistic pathogens, and changes in species and in susceptibilities of isolates recovered on doxycycline medium. RESULTS: There was no significant evidence that changes in total anaerobic counts over the treatment period (P = 0.96) differed between treatment groups. Likewise, periodontal pathogens, opportunistic pathogens, or normal flora did not differ descriptively between groups. Although there was a significant increase (P <0.001) in the total CFU recovered from the 4 microg/ml doxycycline plates at 24 months for SDD versus placebo, the percentage that was clinically resistant to doxycycline (minimal inhibitory concentration [MIC] > or = 16 microg/ml) decreased over the 24-month period in both groups and did not differ between the treatment groups (SDD: 79% to 76%; placebo: 83% to 70%; P = 0.2). There were no significant differences (P >0.28 for each) in the change in cross-resistance between the groups for doxycycline and the other five antibiotics. CONCLUSIONS: No antimicrobial effect on the subgingival flora was detected following treatment with SDD for 24 months, relative to baseline or to placebo. The increase in initial resistance (at 4 microg/ml) did not translate into a significant increase in the percent resistant to doxycycline (MIC > or = 16 microg/ml) for patients in the SDD group.

Status Report from the Scientific Panel on Antibiotic Use in Dermatology of the American Acne and Rosacea Society: Part 1: Antibiotic Prescribing Patterns, Sources of Antibiotic Exposure, Antibiotic Consumption and Emergence of Antibiotic Resistance, Impact of Alterations in Antibiotic Prescribing, and Clinical Sequelae of Antibiotic Use.

Oral and topical antibiotics are commonly prescribed in dermatologie practice, often for noninfectious disorders, such as acne vulgaris and rosacea. Concerns related to antibiotic exposure from both medical and nonmedical sources require that clinicians consider in each case why and how antibiotics are being used and to make appropriate adjustments to limit antibiotic exposure whenever possible. This first article of a three-part series discusses prescribing patterns in dermatology, provides an overview of sources of antibiotic exposure, reviews the relative correlations between the magnitude of antibiotic consumption and emergence of antibiotic resistance patterns, evaluates the impact of alterations in antibiotic prescribing, and discusses the potential relevance and clinical sequelae of antibiotic use, with emphasis on how antibiotics are used in dermatology.

Status Report from the Scientific Panel on Antibiotic Use in Dermatology of the American Acne and Rosacea Society: Part 3: Current Perspectives on Skin and Soft Tissue Infections with Emphasis on Methicillin-resistant Staphylococcus aureus, Commonly Encountered Scenarios when Antibiotic Use May Not Be Needed, and Concluding Remarks on Rational Use of Antibiotics in Dermatology.

In this third article of the three-part series, management of skin and soft tissue infections is reviewed with emphasis on new information on methicillin-resistant Staphylococcus aureus. Due to changes in the evolution of methicillin-resistant Staphylococcus aureus clones, previous distinctions between healthcare-acquired methicillin-resistant Staphylococcus aureus and community-acquired methicillin-resistant Staphylococcus aureus are currently much less clinically relevant. Many nosocomial cases of methicillin-resistant Staphylococcus aureus infection are now caused by community-acquired methicillin-resistant Staphylococcus aureus, with changing patterns of antibiotic susceptibility and resistance. Also reviewed are clinical scenarios where antibiotics may not be needed and suggestions for optimal use of antibiotic therapy for dermatologie conditions, including recommendations on perioperative antibiotic use.

Non-antibacterial tetracycline formulations: host-modulators in the treatment of periodontitis and relevant systemic diseases.

Traditionally, the dental profession has primarily treated periodontitis using a mechanical/surgical, rather than a pharmaceutical, approach. However, based on experiments several decades ago which demonstrated that tetracyclines, unexpectedly, inhibit collagen- and bone-destructive mammalian-derived enzymes (e.g. the collagenases), and through non-antibiotic mechanisms, the concept of host-modulation therapy (HMT) was developed. Accordingly, two drug-development strategies evolved: (i) the development of non-antimicrobial formulations of doxycycline; and (ii) the chemical modification of tetracyclines to eliminate their antibiotic activity but retain (or even enhance) their anti-collagenase properties. Regarding the latter, these chemically modified tetracyclines (CMTs) showed efficacy in vitro, in animal models of periodontal (and relevant systemic) disease, and in preliminary clinical trials on patients with Kaposi's sarcoma (however, at the high doses used, photosensitivity was a significant side-effect). In the first strategy, subantimicrobial-dose doxycycline (SDD) demonstrated safety and efficacy in human clinical trials and was approved by the U S Food and Drug Administration (U S FDA) and in other countries for the treatment of periodontitis (20 mg, twice daily, i.e. once every 12 hours) adjunctive to scaling and root planing, and for chronic inflammatory skin diseases (40-mg sustained-release 'beads'). SDD also showed efficacy in patients with systemic diseases relevant to periodontitis, including diabetes mellitus and arthritis, and in postmenopausal women with local and systemic bone loss. Importantly, long-term administration of SDD, of up to 2 years, in clinical trials did not produce antibiotic side-effects. SDD (and in the future, new HMTs, such as low-dose CMT-3, resolvins and chemically modified curcumins) may shift the paradigm of periodontal therapy from a predominantly surgical approach to the greater use of medicinal/pharmacologic strategies, ultimately to benefit larger numbers of patients.

Detection and characterization of beta-lactamase genes in subgingival bacteria from patients with refractory periodontitis.

Fifty-three beta-lactamase-producing strains of oral bacteria isolated from patients with refractory periodontitis in Norway and USA were screened for the presence of the bla(TEM), bla(SHV), bla(OXA), bla(ampC), bla(cfxA), and bla(cepA/cblA) genes by the polymerase chain reaction (PCR). The PCR products were characterized by direct sequencing of the amplified DNA. Thirty-four of the 53 enzyme-producing strains (64%) were positive in one of the PCR assays. All beta-lactamase-producing Prevotella and Capnocytophaga spp. were CfxA positive. TEM-type beta-lactamases were identified in one strain each of Escherichia coli and Neisseria sp., and one strain of Citrobacter freundii possessed an AmpC-type beta-lactamase. Screening for gene cassettes and genes known to be associated with integrons did not reveal the presence of integrons in these oral bacteria. Sequence analyses showed that most CfxA positive Prevotella and Capnocytophaga isolates from patients with refractory periodontitis harboured variants of the CfxA2 and CfxA3 enzyme. The present study also showed that many different genetic determinants of beta-lactamase production are found in bacteria isolated from refractory periodontitis, many of which remain to be characterized.

Effects of subantimicrobial-dose doxycycline in the treatment of moderate acne.

OBJECTIVE: To determine if treatment with subantimicrobial-dose (SD) doxycycline hyclate (20-mg tablets taken twice daily) improved clinical outcome, had any detectable effect on skin flora, led to overgrowth or colonization of skin by opportunistic pathogens, or resulted in an increase in antibiotic resistance by the surface skin microflora in patients with moderate acne compared with placebo. DESIGN: Multicenter, double-blind, randomized, placebo-controlled, parallel-group trial. SETTING: Two university-based clinics. SUBJECTS: Adults (N = 51) with moderate facial acne. INTERVENTIONS: Patients were randomized to receive SD doxycycline (Periostat; CollaGenex Pharmaceuticals Inc, Newtown, Pa) or placebo twice daily for 6 months. MAIN EFFICACY OUTCOMES: Primary: changes from baseline in numbers of inflammatory, noninflammatory, and total lesions. Secondary: changes from baseline of individual counts of papules, pustules, and nodules and global assessments of clinical improvement by patient and physician. RESULTS: Forty patients completed 6 months of treatment. At 6 months, the SD doxycycline group had a significantly greater percent reduction in the number of comedones (P<.01), inflammatory and noninflammatory lesions combined (P<.01), and total inflammatory lesions (P<.05) than did the placebo group. They also had significantly greater improvement according to the clinician's global assessment (P =.03). There were no significant differences in microbial counts between groups and no evidence of change in antibiotic susceptibility or colonization by potential pathogens. The treatment was well tolerated. CONCLUSIONS: Twice-daily SD doxycycline treatment significantly reduced the number of inflammatory and noninflammatory lesions in patients with moderate facial acne, was well tolerated, had no detectable antimicrobial effect on the skin flora, and did not result in any increase in the number or severity of resistant organisms.