RESUMO
Cystargolides are natural products originally isolated from Kitasatospora cystarginea NRRL B16505 as inhibitors of the proteasome. They are composed of a dipeptide backbone linked to a ß-lactone warhead. Recently, we identified the cystargolide biosynthetic gene cluster, but systematic genetic analyses had not been carried out because of the lack of a heterologous expression system. Here, we report the discovery of a homologous cystargolide biosynthetic pathway in Streptomyces durhamensis NRRL-B3309 by genome mining. The gene cluster was cloned via transformation-associated recombination and heterologously expressed in Streptomyces coelicolor M512. We demonstrate that it contains all genes necessary for the production of cystargolide A and B. Single gene deletion experiments reveal that only five of the eight genes from the initially proposed gene cluster are essential for cystargolide synthesis. Additional insights into the cystargolide pathway could be obtained from in vitro assays with CysG and chemical complementation of the respective gene knockout. This could be further supported by the in vitro investigation of the CysG homolog BelI from the belactosin biosynthetic gene cluster. Thereby, we confirm that CysG and BelI catalyze a cryptic SAM-dependent transfer of a methyl group that is critical for the construction of the cystargolide and belactosin ß-lactone warheads.
Assuntos
Dipeptídeos , Metiltransferases , Streptomycetaceae , Vias Biossintéticas , Dipeptídeos/metabolismo , Lactonas/metabolismo , Metiltransferases/química , Metiltransferases/genética , Metiltransferases/metabolismo , Família Multigênica , Streptomyces coelicolor/genética , Streptomycetaceae/enzimologia , Streptomycetaceae/genéticaRESUMO
The caseinolytic protease is a highly conserved serine protease, crucial to prokaryotic and eukaryotic protein homeostasis, and a promising antibacterial and anticancer drug target. Herein, we describe the potent cystargolides as the first natural ß-lactone inhibitors of the proteolytic core ClpP. Based on the discovery of two clpP genes next to the cystargolide biosynthetic gene cluster in Kitasatospora cystarginea, we explored ClpP as a potential cystargolide target. We show the inhibition of Staphylococcus aureus ClpP by cystargolide A and B by different biochemical methods in vitro. Synthesis of semisynthetic derivatives and probes with improved cell penetration allowed us to confirm ClpP as a specific target in S. aureus cells and to demonstrate the anti-virulence activity of this natural product class. Crystal structures show cystargolide A covalently bound to all 14 active sites of ClpP from S. aureus, Aquifex aeolicus, and Photorhabdus laumondii, and reveal the molecular mechanism of ClpP inhibition by ß-lactones, the predominant class of ClpP inhibitors.
Assuntos
Dipeptídeos , Staphylococcus aureus , Staphylococcus aureus/metabolismo , Domínio Catalítico , Dipeptídeos/metabolismo , Virulência , Endopeptidase Clp/metabolismoRESUMO
The hydroxamate moiety of the natural product actinonin mediates inhibition of metalloproteinases because of its chelating properties towards divalent cations in the active site of those enzymes. Owing to its antimicrobial activity, actinonin has served as a lead compound for the development of new antibiotic drug candidates. Recently, we identified a putative gene cluster for the biosynthesis of actinonin. Here, we confirm and characterize this cluster by heterologous pathway expression and gene-deletion experiments. We assigned the biosynthetic gene cluster to actinonin production and determine the cluster boundaries. Furthermore, we establish that ActI, an AurF-like oxygenase, is responsible for the N-hydroxylation reaction that forms the hydroxamate warhead. Our findings provide the basis for more detailed investigations of actinonin biosynthesis.
RESUMO
The Pd-catalyzed Heck-type coupling (Matsuda-Heck reaction) of electron rich arene diazonium salts with electron deficient olefins has been exploited for the synthesis of phenylpropanoid natural products. Examples described herein are the naturally occurring benzofurans methyl wutaifuranate, wutaifuranol, wutaifuranal, their 7-methoxy derivatives, and the O-prenylated natural products boropinols A and C.
RESUMO
Belactosins and cystargolides are natural product proteasome inhibitors from Actinobacteria. Both feature dipeptidic backbones and a unique ß-lactone building block. Herein, we present a detailed investigation of their biosynthesis. Identification and analysis of the corresponding gene clusters indicated that both compounds are assembled by rare single-enzyme amino acid ligases. Feeding experiments with isotope-labeled precursors and inâ vitro biochemistry showed that the formation of the ß-lactone warhead is unprecedented and reminiscent of leucine biosynthesis, and that it involves the action of isopropylmalate synthase homologues.
Assuntos
Dipeptídeos/metabolismo , Lactonas/química , Peptídeos/metabolismo , Inibidores de Proteassoma/síntese química , Streptomycetaceae/metabolismo , Aminoácidos/metabolismo , Genoma Bacteriano , Peptídeos e Proteínas de Sinalização Intercelular , Ligases/genética , Ligases/metabolismo , Espectroscopia de Ressonância Magnética , Família Multigênica , Streptomycetaceae/genética , Espectrometria de Massas em TandemRESUMO
α-Methylene-γ-butyrolactone and α-methylene-δ-valerolactone undergo Pd-catalyzed Matsuda-Heck couplings with arene diazonium salts to α-benzyl butenolides or pentenolides, respectively, or to α-benzylidene lactones. The observed regioselectivity is strongly ring size dependent, with six-membered rings giving exclusively α-benzyl pentenolides, whereas the five-membered α-methylene lactone reacts to mixtures of regioisomers with a high proportion of (E)-α-benzylidene-γ-butyrolactones. DFT calculations suggest that the reasons for these differences are not thermodynamic but kinetic in nature. The relative energies of the conformers of the Pd σ-complexes resulting from insertion into the Pd-aryl bond were correlated with the dihedral angles between Pd and endo-ß-H. This correlation revealed that in the case of the six-membered lactone an energetically favorable conformer adopts a nearly synperiplanar Pd/endo-ß-H arrangement, whereas for the analogous Pd σ-complex of the five-membered lactone the smallest Pd/endo-ß-H dihedral angle is observed for a conformer with a comparatively high potential energy. The optimized conditions for Matsuda-Heck arylations of exo-methylene lactones were eventually applied to the synthesis of the natural product anemarcoumarin A.
RESUMO
The emergence of antibiotic-resistant pathogenic bacteria within the last decades is one reason for the urgent need for new antibacterial agents. A strategy to discover new anti-infective compounds is the evaluation of the genetic capacity of secondary metabolite producers and the activation of cryptic gene clusters (genome mining). One genus known for its potential to synthesize medically important products is Amycolatopsis. However, Amycolatopsis japonicum does not produce an antibiotic under standard laboratory conditions. In contrast to most Amycolatopsis strains, A. japonicum is genetically tractable with different methods. In order to activate a possible silent glycopeptide cluster, we introduced a gene encoding the transcriptional activator of balhimycin biosynthesis, the bbr gene from Amycolatopsis balhimycina (bbrAba), into A. japonicum. This resulted in the production of an antibiotically active compound. Following whole-genome sequencing of A. japonicum, 29 cryptic gene clusters were identified by genome mining. One of these gene clusters is a putative glycopeptide biosynthesis gene cluster. Using bioinformatic tools, ristomycin (syn. ristocetin), a type III glycopeptide, which has antibacterial activity and which is used for the diagnosis of von Willebrand disease and Bernard-Soulier syndrome, was deduced as a possible product of the gene cluster. Chemical analyses by high-performance liquid chromatography and mass spectrometry (HPLC-MS), tandem mass spectrometry (MS/MS), and nuclear magnetic resonance (NMR) spectroscopy confirmed the in silico prediction that the recombinant A. japonicum/pRM4-bbrAba synthesizes ristomycin A.
Assuntos
Actinomycetales/metabolismo , Família Multigênica/genética , Ristocetina/metabolismo , Actinomycetales/genética , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Vancomicina/análogos & derivados , Vancomicina/metabolismoRESUMO
[This corrects the article DOI: 10.3389/fninf.2024.1323203.].
RESUMO
Memory formation is usually associated with Hebbian learning and synaptic plasticity, which changes the synaptic strengths but omits structural changes. A recent study suggests that structural plasticity can also lead to silent memory engrams, reproducing a conditioned learning paradigm with neuron ensembles. However, this study is limited by its way of synapse formation, enabling the formation of only one memory engram. Overcoming this, our model allows the formation of many engrams simultaneously while retaining high neurophysiological accuracy, e.g., as found in cortical columns. We achieve this by substituting the random synapse formation with the Model of Structural Plasticity. As a homeostatic model, neurons regulate their activity by growing and pruning synaptic elements based on their current activity. Utilizing synapse formation based on the Euclidean distance between the neurons with a scalable algorithm allows us to easily simulate 4 million neurons with 343 memory engrams. These engrams do not interfere with one another by default, yet we can change the simulation parameters to form long-reaching associations. Our model's analysis shows that homeostatic engram formation requires a certain spatiotemporal order of events. It predicts that synaptic pruning precedes and enables synaptic engram formation and that it does not occur as a mere compensatory response to enduring synapse potentiation as in Hebbian plasticity with synaptic scaling. Our model paves the way for simulations addressing further inquiries, ranging from memory chains and hierarchies to complex memory systems comprising areas with different learning mechanisms.
RESUMO
Belactosin A, a ß-lactone proteasome inhibitor, contains a unique 3-(trans-2'-aminocyclopropyl)alanine moiety. We recently identified the biosynthetic gene cluster of the belactosin series from Streptomyces sp. UCK14. To shed light on the formation of the aminocyclopropylalanine, we established a heterologous pathway expression, constructed a set of gene deletion mutants, and performed feeding studies for a chemical complementation that include the incorporation of stable isotope-labeled precursors. We thereby show that, in the biosynthesis of this building block, a cryptic nitrocyclopropylalanine intermediate is generated from l-lysine. The subsequent reduction of the N-oxygenated precursor to the corresponding amine is mediated by the molybdopterin-dependent enzyme BelN.
Assuntos
AlaninaRESUMO
The serine/threonine protein kinase AKT1 is a downstream target of the chemokine receptor 4 (CXCR4), and both proteins play a central role in the modulation of diverse cellular processes, including proliferation and cell survival. While in chronic myeloid leukemia (CML) the CXCR4 is downregulated, thereby promoting the mobilization of progenitor cells into blood, the receptor is highly expressed in breast cancer cells, favoring the migratory capacity of these cells. Recently, the LIM and SH3 domain protein 1 (LASP1) has been described as a novel CXCR4 binding partner and as a promoter of the PI3K/AKT pathway. In this study, we uncovered a direct binding of LASP1, phosphorylated at S146, to both CXCR4 and AKT1, as shown by immunoprecipitation assays, pull-down experiments, and immunohistochemistry data. In contrast, phosphorylation of LASP1 at Y171 abrogated these interactions, suggesting that both LASP1 phospho-forms interact. Finally, findings demonstrating different phosphorylation patterns of LASP1 in breast cancer and chronic myeloid leukemia may have implications for CXCR4 function and tyrosine kinase inhibitor treatment.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Neoplasias da Mama/genética , Proteínas do Citoesqueleto/metabolismo , Proteínas com Domínio LIM/metabolismo , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Receptores CXCR4/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Feminino , Humanos , Fosforilação , TransfecçãoRESUMO
The unexpected seroconversion of sentinel mice in our facility to murine T lymphotrophic virus (MTLV) positivity led to our identification of a novel murine astrovirus that we designated murine astrovirus 2 (MuAstV-2). During our investigation, MuAstV-2 was found to be a contaminant of the T helper cell line (D10. G4.1) that was used to generate the MTLV antigen that we included in the multiplex fluorometric immunoassay (MFIA) that we used for sentinel screening. We eventually determined that cross-reactivity with the astrovirus generated a positive result in the MTLV assay. A confirmatory immunofluorometric assay (IFA) using the same MTLV-infected cell line yielded a similar result. However, the use of antigen prepared from MTLV-infected neonatal mouse thymus did not reproduce a positive result, leading us to suspect that the seroreactivity we had observed was not due to infection with MTLV. A mouse antibody production test showed that mice inoculated with naïve D10. G4.1 cells and their contact sentinels tested positive for MTLV using cell-line generated antigen, but tested negative in assays using MTLV antigen produced in mice. Metagenomic analysis was subsequently used to identify MuAstV-2 in feces from 2 sentinel mice that had recently seroconverted to MTLV. Two closely related astrovirus sequences (99.6% capsid identity) were obtained and shared 95% capsid amino acid identity with the MuAstV-2 virus sequenced from the D10. G4.1 cell line. These viruses are highly divergent from previously identified murine astroviruses, displaying <30% capsid identity, yet were closely related to murine astrovirus 2 (85% capsid identity), which had recently been isolated from feral mice in New York City. A MuAstV-2 specific PCR assay was developed and used to eradicate MuAstV-2 from the infected colony using a test and cull strategy. The newly identified MuAstV2 readily transmits to immunocompetent mouse strains by fecal-oral exposure, but fails to infect NOD-Prkdcem26Cd52Il2rgem26Cd22/NjuCrl (NCG) mice, which have significantly impaired adaptive and innate immune systems. Neither immunocompetent nor immunodeficient mice showed any astrovirus-associated pathology. MuAstV-2 may provide a valuable model for the study of specific aspects of astrovirus pathogenesis and virus-host interactions.
Assuntos
Infecções por Astroviridae/metabolismo , Animais , Astroviridae , Infecções por Astroviridae/virologia , Linhagem Celular , Fezes/virologia , Genoma Viral , Imunocompetência/genética , Camundongos/virologia , Doenças dos Roedores/virologia , Linfócitos T Auxiliares-Indutores/imunologiaRESUMO
Phosphoramidon is a potent metalloprotease inhibitor and a widespread tool in cell biology research. It contains a dipeptide backbone that is uniquely linked to a 6-deoxysugar via a phosphoramidate bridge. Herein, we report the identification of a gene cluster for the formation of phosphoramidon and its detailed characterization. In vitro reconstitution of the biosynthesis established TalE as a phosphoramidate-forming kinase and TalC as the glycosyltransferase which installs the l-rhamnose moiety by phosphoester linkage.
RESUMO
West Nile virus (WNV) surfaced as an emerging infectious disease in the northeastern United States in 1999, gradually spread across the continent, and is now endemic throughout North America. Outdoor-housed nonhuman primates at the Tulane National Primate Research Center (TNPRC) in Louisiana were documented with a relatively high prevalence (36%) of antibodies to West Nile virus. We examined the prevalence of antibodies to WNV in a nonhuman primate population housed in outdoor colonies at the Yerkes National Primate Research Center Field Station located near Atlanta, Georgia. We screened rhesus macaques (Macaca mulatta) and sooty mangabeys (Cercocebus atys) that were at least 3 y old by serum neutralization for antibodies to WNV and confirmed these results by hemagglutination-inhibition assay. None of the 45 rhesus monkeys had antibodies to WNV, but 3 of the 45 mangabeys (6.6%) were positive by both serum neutralization and hemagglutination-inhibition tests. The ratio of seroprevalences in the TNPRC and Yerkes primate populations was similar to the ratio of WNV incidences in people in Louisiana and Georgia from 2002 to 2004. The difference in the exposure of nonhuman primates (and possibly humans) to WNV between these 2 regions is consistent with the difference in the abundance of mammal-biting WNV-infectious mosquitoes, which was 23 times lower near Yerkes than around TNPRC in 2003 and 33 times lower in 2004.
Assuntos
Animais de Laboratório/virologia , Cercocebus atys , Culex , Macaca mulatta , Doenças dos Macacos/epidemiologia , Doenças dos Macacos/virologia , Febre do Nilo Ocidental/veterinária , Vírus do Nilo Ocidental/imunologia , Animais , Anticorpos Antivirais/sangue , Georgia/epidemiologia , Testes de Inibição da Hemaglutinação , Abrigo para Animais , Louisiana/epidemiologia , Testes de Neutralização , Densidade Demográfica , Estudos Soroepidemiológicos , Febre do Nilo Ocidental/epidemiologiaRESUMO
Metalloproteinase inhibitors often feature hydroxamate moieties to facilitate the chelation of metal ions in the catalytic center of target enzymes. Actinonin and matlystatins are potent metalloproteinase inhibitors that comprise rare N-hydroxy-2-pentyl-succinamic acid warheads. Here we report the identification and characterization of their biosynthetic pathways. By gene cluster comparison and a combination of precursor feeding studies, heterologous pathway expression and gene deletion experiments we are able to show that the N-hydroxy-alkyl-succinamic acid warhead is generated by an unprecedented variation of the ethylmalonyl-CoA pathway. Moreover, we present evidence that the remarkable structural diversity of matlystatin congeners originates from the activity of a decarboxylase-dehydrogenase enzyme with high similarity to enzymes that form epoxyketones. We further exploit this mechanism to direct the biosynthesis of non-natural matlystatin derivatives. Our work paves the way for follow-up studies on these fascinating pathways and allows the identification of new protease inhibitors by genome mining.
Assuntos
Inibidores de Metaloproteinases de Matriz/química , Inibidores de Metaloproteinases de Matriz/metabolismo , Metaloproteases/efeitos dos fármacos , Inibidores de Proteases/química , Inibidores de Proteases/metabolismo , Acetilcisteína/análogos & derivados , Acetilcisteína/antagonistas & inibidores , Acetilcisteína/química , Actinobacteria/genética , Actinobacteria/metabolismo , Acil Coenzima A , Vias Biossintéticas/genética , Carboxiliases , Deleção de Genes , Perfilação da Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos/genética , Ácidos Hidroxâmicos/antagonistas & inibidores , Ácidos Hidroxâmicos/química , Ácidos Hidroxâmicos/metabolismo , Inibidores de Metaloproteinases de Matriz/farmacologia , Família Multigênica , Ornitina/metabolismo , Oxirredutases , Propionatos/metabolismo , Inibidores de Proteases/farmacologia , Piridazinas/antagonistas & inibidores , Piridazinas/química , Piridazinas/metabolismo , Deleção de Sequência , Streptomyces/genética , Streptomyces/metabolismoRESUMO
Despite the extensive use of doxycycline in tetracycline-inducible rodent models, little is known regarding its stability in feed or water or the most effective route or dose. We assessed the concentrations of doxycycline in reverse-osmosis-purified (RO; pH 6.0) and acidified RO (pH 2.6) water in untinted or green-tinted bottles. Doxycycline remained stable in all groups for 7 d and in acidified water in untinted bottles for 14 d. Fungal growth occurred in nonacidified water in tinted and untinted bottles by 12 and 14 d, respectively, and in tinted bottles containing acidified water on day 14, but not in untinted bottles with acidified water. Doxycycline concentrations were also assessed before and at various points after the pelleting of feed from 2 vendors. Each batch was divided for storage at 4 °C, at room temperature, or within ventilated mouse isolator cages and then sampled monthly for 6 mo. Drying caused the greatest decline in doxycycline concentration, whereas γ-irradiation plus shipping and storage condition had minimal effect. Two mouse lines with tetracycline-inducible promoters received 25, 150, or 467 µg/mL or 2 mg/mL doxycycline in water and 200 or 625 ppm in feed before analysis of GFP expression. GFP was expressed in Rosa-rtTA2 mice at 150 µg/mL, whereas Cags-rtTA3 mice required 25 µg/mL. These studies indicate that 1) doxycycline-compounded feed can be handled in the same manner as standard rodent feed, 2) tinted water bottles are not necessary for maintaining drug concentrations, and 3) concentrations lower than those used typically may be effective in lines with tetracycline-inducible promoters.
Assuntos
Antibacterianos/administração & dosagem , Antibacterianos/química , Doxiciclina/administração & dosagem , Doxiciclina/química , Ração Animal , Animais , Doxiciclina/sangue , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Tetraciclina/farmacologia , Água/químicaRESUMO
Corynebacterium bovis is a common pathogen in athymic nude mouse colonies. Control and eradication of the organism are challenging because depopulation and restricted colony access are often not options within vivaria. We evaluated potential sources and dissemination routes of C. bovis in an enzootically infected colony. Immunocompetent mice and personnel were evaluated for their potential to carry C. bovis, and husbandry and sanitation methods were evaluated for their efficacy in preventing cross-contamination. C. bovis was detected in furred immunocompetent mice previously exposed to infected athymic nude mice and in the nasopharynx of humans. Microisolation cages were not effective in maintaining athymic nude mice C. bovis-free when they were housed in a room known to contain immunodeficient mice with C. bovis infections. A tunnel washer that provided a ≥180 °F final rinse provided effective elimination of C. bovis from cage components. Passive and active air sampling techniques showed airborne dispersal of C. bovis despite the use of individually ventilated caging systems and stringent operational standards. Bacterial growth was not observed in settle plates placed inside autoclaved individually ventilated microisolation cages on various ventilated racks for 24-h periods. C. bovis aerosolization was shown to be a means of spread of the bacterium during cage-change procedures inside a class II type A2 biosafety cabinet. Our findings indicate that C. bovis can be a pervasive environmental contaminant in infected rodent holding rooms and successful eradication strategies must include environmental decontamination and attention to air quality.
Assuntos
Microbiologia do Ar , Criação de Animais Domésticos/métodos , Infecções por Corynebacterium/veterinária , Camundongos/microbiologia , Doenças dos Roedores/prevenção & controle , Poluição do Ar em Ambientes Fechados/análise , Poluição do Ar em Ambientes Fechados/prevenção & controle , Animais , Corynebacterium/isolamento & purificação , Infecções por Corynebacterium/epidemiologia , Infecções por Corynebacterium/prevenção & controle , Infecções por Corynebacterium/transmissão , Feminino , Abrigo para Animais/normas , Masculino , Camundongos Nus/microbiologia , Doenças dos Roedores/epidemiologia , Doenças dos Roedores/transmissãoRESUMO
Athymic nude mice infected with Corynebacterium bovis typically exhibit transient hyperkeratotic dermatitis. Our vivarium experienced an increased incidence of disease characterized by persistent skin lesions and increased mortality, leading to this study. For detection of infection, skin and buccal swab methods showed comparable sensitivities in nude mice. Various prevention, treatment, and eradication strategies were evaluated through clinical assessment, microbiology, and histopathology. In experimentally naïve athymic nude mice, a 2-wk course of prophylactic amoxicillin-containing diet (1200 ppm amoxicillin; effective dose, 200 mg/kg) was ineffective at preventing infection or disease. There was also no significant difference in disease duration or severity in athymic nude mice that received amoxicillin diet or penicillin-streptomycin topical spray (penicillin, 2500 U/mL; streptomycin, 2500 µg/mL). Prolonged treatment with 4 or 8 wk of amoxicillin diet cleared only a small number of athymic nude mice that had subclinical C. bovis infections. Antibiotic sensitivity of C. bovis isolates demonstrated a small colony isolate with less susceptibility to all antibiotics compared with a large colony isolate. Resistance did not appear to develop after prolonged treatment with amoxicillin. Provocation testing by administration of cyclophosphamide (50 mg/kg i.p. every 48 to 72 h for 90 d) to subclinically infected athymic nude mice resulted in prolonged clinical disease that waxed and waned without progression to severe disease. Our findings suggest that antibiotic prophylaxis and treatment of clinical disease in experimentally naïve mice is unrewarding, eradication of bacterial infection is difficult, and severe disease associated with C. bovis is likely multifactorial.
Assuntos
Infecções por Corynebacterium/complicações , Corynebacterium , Dermatite/veterinária , Camundongos Nus/microbiologia , Doenças dos Roedores/tratamento farmacológico , Doenças dos Roedores/prevenção & controle , Dermatopatias Bacterianas/veterinária , Administração Oral , Administração Tópica , Amoxicilina/administração & dosagem , Amoxicilina/uso terapêutico , Animais , Animais de Laboratório/microbiologia , Antibacterianos/administração & dosagem , Antibacterianos/uso terapêutico , Corynebacterium/isolamento & purificação , Dermatite/microbiologia , Dermatite/prevenção & controle , Feminino , Masculino , Camundongos , Penicilinas/administração & dosagem , Penicilinas/uso terapêutico , Doenças dos Roedores/microbiologia , Pele/microbiologia , Pele/patologia , Dermatopatias Bacterianas/tratamento farmacológico , Dermatopatias Bacterianas/prevenção & controle , Resultado do TratamentoRESUMO
We determined the efficacy of ivermectin-compounded feed against fur mites in mice and describe its use to eradicate mites in vivaria holding approximately 30,000 cages. C57BL/6NCrl mice infested with Myobia musculi and Myocoptes musculinus were treated with ivermectin-compounded feed (approximate ingested dose, 1.3 mg/kg) for 1, 4, or 8 consecutive weeks. Regardless of treatment duration, all treated mice, as well as contact sentinels, remained free of fur mites for as long as 21 wk after treatment. No adverse effects were observed. Subsequently, facility-wide treatment was implemented in an attempt to eradicate fur mites from 3 vivaria housing approximately 120,000 mice. Medicated feed was provided for 8 wk to ensure that all cages and mice were treated. A single investigative group reported adverse effects in their colony 4 wk after treatment was initiated; mortality was attributed to ivermectin toxicity after an intracranial injection at 1 d of age. Naïve pups were unaffected. No other adverse effects were noted. Approximately 14,500 skin scrape samples were evaluated during the 12-mo posttreatment surveillance period. All samples were negative for mites. To our knowledge, this is the first report of successful eradication of fur mites from a mouse colony of this large size.
Assuntos
Acaricidas/uso terapêutico , Cabelo/parasitologia , Ivermectina/uso terapêutico , Camundongos/parasitologia , Infestações por Ácaros/veterinária , Doenças dos Roedores/tratamento farmacológico , Animais , Feminino , Masculino , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos , Infestações por Ácaros/tratamento farmacológico , Infestações por Ácaros/parasitologia , Doenças dos Roedores/parasitologia , Resultado do TratamentoRESUMO
Fur mites are a persistent problem in contemporary laboratory mouse colonies. We conducted several studies to evaluate fur mite diagnostic methodologies and interpretation of results. Retrospective analysis of test results from sentinel mice exposed to soiled bedding collected from colonies infested with Myobia musculi and Myocoptes musculinus revealed the skin scrape test to be more reliable than pelt examination, provided that both the head and dorsal thoracolumbar regions were sampled. To assess their diagnostic accuracy, 3 commercial laboratories were sent positive control slides containing mites, mite parts, or eggs in sets of slides containing diagnostic skin scrapings in varying ratios. Laboratory B correctly identified the positive control slide. Laboratory A identified 1 of 3 positive control slides, whereas laboratory C failed to identify both positive control slides submitted. To determine the time required for a mouse to shed its entire hair coat, fur of Crl:CD1(ICR), BALB/cAnNCrl, and Crl:CFW(SW) albino mice was dyed black and the presence of dyed fur evaluated monthly for 8 mo. Limited dyed hair was still present at 8 mo; therefore, finding eggs or egg casings many months after treatment cessation does not necessarily imply treatment failure. To evaluate the effectiveness of soiled bedding sentinels for detection of fur mites in a mite-infested colony, we exposed naïve mice to varying amounts (100%, 50%, 25%, 2.5%, and 0%) of soiled bedding in clean bedding. As little as 2.5% soiled bedding resulted in detection of a positive sentinel within a 2-mo period.