A method for the detection of gelatinase production by bacteria

Osteomyelitis caused by Aspergillus terreus complex in a dog: a case report

BACKGROUND

In dogs, the most frequently reported mycosis associated with Aspergillus spp. are respiratory infections. Systemic aspergillosis is uncommon, with reported cases been associated with several Aspergillus species. Aspergillus terreus species complex are ubiquitous organisms, unfrequently associated with local or systemic disease in animals and humans, and treatment of osteomyelitis caused by this species is usually unfavorable.

CASE PRESENTATION

This case report describes the case of a 5-year-old dog, referred to the Veterinary Hospital of the Faculty of Veterinary Medicine of the University of Lisbon, Portugal, with a history of lameness of the right thoracic limb. Radiographs and CT scan revealed two different lesions on right humerus and radio, which were biopsied. The samples collected were submitted to cytological and histopathological evaluation and bacterial and mycological culture. Environmental samples, including of the surgery room and of the biopsy needle were also evaluated for the presence of fungi. Regarding biopsy samples, bacterial culture was negative, but mycological analysis originated a pure culture of a fungal species later identified as Aspergillus terreus by Sanger sequencing. Results were compatible with histopathologic examination, which revealed periosteal reaction and invasion of hyphae elements. Also, mycological analysis of both environmental samples evaluated were negative. The virulence profile of the fungal isolate was phenotypically characterized using specific media, allowing to reveal its ability to produce several enzymes involved in its pathogenicity, namely lipase, hemolysin and DNAse, corresponding to a Virulence Index (V. Index.) of 0.43. The patient was submitted to itraconazole therapy for 8 weeks. After 3 weeks, the patient showed significant clinical improvement, and after 6 weeks no radiographic signs were observed.

CONCLUSIONS

Antifungal therapy with itraconazole can contribute to the remission of canine infections promoted by Aspergillus terreus complex with a relevant V. Index.

Oak bark (Quercus sp. cortex) protects plants through the inhibition of quorum sensing mediated virulence of Pectobacterium carotovorum

Bacterial intercellular communication mediated by small diffusible molecules, known as quorum sensing (QS), is a common mechanism for regulating bacterial colonisation strategies and survival. Influence on QS by plant-derived molecules is proposed as a strategy for combating phytopathogens by modulating their virulence. This work builds upon other studies that have revealed plant-derived QS inhibitors extracted from oak bark (Quercus sp.). It was found that co-incubation of Pectobacterium carotovorum VKM-B-1247 with oak bark extract (OBE) reduced the production of acyl-HSL. This was accompanied by a dose-dependent decrease in the bacterial cellulolytic and protease activity. At the transcriptomic level, the OBE treatment suppressed the main QS-related genes expR/expI. Potato tubers pre-treated with OBE showed resistance to a manifestation of soft-rot symptoms. Analysis of the component composition of the OBE identified several biologically active molecules, such as n-hexadecanoic acid, 2,6-di-tert-butyl-4-methylphenol, butylated hydroxytoluene (BHT), gamma-sitosterol, lupeol, and others. Molecular docking of the binding energy between identified molecules and homology models of LuxR-LuxI type proteins allow to identify potential inhibitors. Collectively, obtained results figure out great potential of widely distributed oak-derived plant material for bacterial control during storage of potato.

Isolation and characterization of bacteria associated with the rhizosphere of halophytes (Salsola stocksii and Atriplex amnicola) for production of hydrolytic enzymes

Microbes from hypersaline environments are useful in biotechnology as sources of novel enzymes and proteins. The current study aimed to characterize halophilic bacteria from the rhizosphere of halophytes (Salsola stocksii and Atriplex amnicola), non-rhizospheric, and brine lake-bank soils collected from Khewra Salt Mine and screening of these bacterial strains for industrially important enzymes. A total of 45 bacterial isolates from the rhizosphere of Salsola, 38 isolates from Atriplex, 24 isolates from non-rhizospheric, and 25 isolates from lake-bank soils were identified by using 16S rRNA gene analysis. Phylogenetic analysis showed that bacterial strains belonging to Bacillus, Halobacillus, and Kocuria were dominant in the rhizosphere of halophytes (Salsola and Atriplex), and Halobacillus and Halomonas were dominating genera from non-rhizospheric and lake-bank soils. Mostly identified strains were moderately halophilic bacteria with optimum growth at 1.5-3.0 M salt concentrations. Most of the bacterial exhibited lipase, protease, cellulase, amylase, gelatinase, and catalase activities. Halophilic and halotolerant Bacilli (AT2RP4, HL1RS13, NRS4HaP9, and LK3HaP7) identified in this study showed optimum lipase, protease, cellulase, and amylase activities at 1.0-1.5 M NaCl concentration, pH 7-8, and temperature 37 °C. These results indicated that halophilic and halotolerant bacteria can be used for bioconversion of organic compounds to useful products under extreme conditions.

Prevalence of glycopeptide and aminoglycoside resistance in Enterococcus and Listeria spp. in low microbial load diets of neutropenic hospital patients

Low microbial load diets for patients with haematological malignancy were examined for enterococci and listeria using pre-enrichment, enrichment and selective plating. Enterococci were highly prevalent and their ecology diverse; 100/211 samples yielded 132 isolates made up of 67 strains distinguishable by PFGE. Listeria monocytogenes was not found. Screening of enterococci for antibiotic resistance showed low level vancomycin resistance (6-12 microg/ml) in six isolates of E. gallinarum and high level streptomycin resistance (> or = 1000 microg/ml) in eight isolates from various foods. No strains showing high level glycopeptide or gentamicin resistance were found. The high prevalence of enterococci in food processed for safety indicates a possible route for the acquisition of antibiotic-resistant strains by vulnerable hospital patients.

Identification of Arthrobacter oxydans, Arthrobacter luteolus sp. nov., and Arthrobacter albus sp. nov., isolated from human clinical specimens

Five Arthrobacter isolates from clinical specimens were studied by phenotypic, chemotaxonomic, and genetic characterization. Two strains had characteristics consistent with those of Arthrobacter oxydans. One strain was related to A. citreus; however, DNA-DNA hybridization and phenotypic characteristics indicated that this strain belongs to a new species, for which the name Arthrobacter luteolus sp. nov. is proposed. Two strains were closely related to A. cumminsii by 16S rRNA gene sequencing, but DNA-DNA hybridization, peptidoglycan type, and some phenotypic features indicated that they should be assigned to a new species, for which the name Arthrobacter albus sp. nov. is proposed. The type strain of A. luteolus is CF25 (DSM 13067). The type strain of A. albus is CF43 (DSM 13068).

Microbial communities of continuously cropped, irrigated rice fields

In continuously cropped, irrigated rice fields, soil microbial biomass as measured by total phospholipid fatty acid concentrations declined during the second half of the crop cycle. This decline was also observed in other components of the microbial community assessed by viable counts, including denitrifiers and sporeformers. Simultaneous with total biomass decline was the increase in potential indicators of nutrient stress--such as ratios of cyclopropanol ((Sigma)[cy/(omega)7c]) and trans ((Sigma)[(omega)7t/(omega)7c]) phospholipid fatty acids--in plain crop soil but not in the rhizosphere. Polyhydroxyalkanoate levels were enhanced in the root environment of mature rice. Polyunsaturated eukaryotic biomarkers accounted for only 13 to 16 mol% of the total phospholipids, including 2 mol% of 18:2(omega)6, which is considered a fungal biomarker. Single biomarkers for defined physiological groups of bacteria did not follow the declining trend of total microbial biomass. Signature compounds for gram-positive and gram-negative fermenters (plasmalogen phospholipids), methanogenic bacteria (diether lipids), and methanotrophs (18:1(omega)8c) increased as the crop approached maturity. Methanotrophs were not particularly enriched in the rhizosphere. Methanogenic biomarkers were, however, most abundant in root extracts from mature rice plants. Assuming that soil microbial biomass plays a significant role as a passive nutrient pool, its reduction during the second half of the cropping season suggests a mechanism that may ultimately contribute to declining productivity in irrigated, continuous rice cropping systems.

Tests for detecting degradation of gelatin: comparison of five methods

Five methods for detecting degradation of gelatin by bacteria were compared. These were liquefaction in nutrient broth, hydrolysis in nutrient agar, hydrolysis of charcoal gelatin strips, degradation of the gelatin on strips of photographic film, and alkalinization of gelatin agar. Degradation of photographic film is a rapid and convenient method but, like hydrolysis of gelatin in broth and in agar, may fail to detect weakly positive strains of bacteria. Alkalinization of gelatin in an agar medium is a convenient and sensitive method to detect degradation of gelatin, particularly by Pseudomonas fluorescens, but this method may not be applicable to some species.

Effect of long-term lead exposure on the seawater and sediment bacteria from heterogeneous continuous flow cultures

Lead-influenced changes of the composition of seawater and sediment bacteria were studied in two flow cultures run with lead-contaminated artificial seawater (1 mg Pb(2+)1(-1)) and one control culture. During the experiment viable counts of physiological groups of bacteria from the control culture were not significantly different from that of the lead-contaminated cultures. Lead tolerance of seawater and sediment bacteria strains was investigated. Comparisons of growth yields showed that lead tolerance of seawater and sediment bacteria was lost again if the bacteria were cultivated in a medium without lead. Lead tolerance could not be demonstrated for the sediment bacteria of one lead-contaminated culture. Heterotrophic uptake measurements with radioactive glucose indicated that seawater bacteria from the lead-contaminated cultures became adapted to lead pollution. The sediment bacteria, however, did not reveal lead tolerance by this method. Fluctuations in lead content of the sediment as well as of the overlying seawater gave indications of adsorption-desorption processes between seawater and sediment. Lead was not homogeneously distributed at the sediment surface.