SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Journal of medical microbiology

28

Aspergillosis is one of the most common causes of death in captive birds. Aspergillus fumigatus accounts for approximately 95 % of aspergillosis cases and Aspergillus flavus is the second most frequent organism associated with avian infections. In the present study, the fungi were grown from avian clinical samples (post-mortem lung material) and environmental samples (eggs, food and litter). Microsatellite markers were used to type seven clinical avian isolates and 22 environmental isolates of A. flavus. A. flavus was the only species (28 % prevalence) detected in the avian clinical isolates, whereas this species ranked third (19 %) after members of the genera Penicillium (39 %) and Cladosporium (21 %) in the environmental samples. Upon microsatellite analysis, five to eight distinct alleles were detected for each marker. The marker with the highest discriminatory power had eight alleles and a 0.852 D value. The combination of all six markers yielded a 0.991 D value with 25 distinct genotypes. One clinical avian isolate (lung biopsy) and one environmental isolate (egg) shared the same genotype. Microsatellite typing of A. flavus grown from avian and environmental samples displayed an excellent discriminatory power and 100 % reproducibility. This study showed a clustering of clinical and environmental isolates, which were clearly separated. Based upon these results, aspergillosis in birds may be induced by a great diversity of isolates.

Concepts: Gene, Genetics, Evolution, Biology, Aspergillus flavus, Aspergillus, Aspergillus fumigatus, Microsatellite

28

There is a clear clinical need for alternative types of non-antibiotic biocides due to the rising global health concern of microbial drug resistance. In this work, a novel antibacterial concept was delineated that utilized hyperosmotic stress (H) in concert with membrane-disrupting nanoemulsions (NEs). The antibacterial effects of either H or a NE, as well as in combination (H+NE), were assessed in vitro using an Escherichia coli model. It was found that exposure to H or NE alone produced dose-dependent bacteriostatic and bactericidal effects, respectively. However, the bactericidal action of NE was significantly amplified in the presence of H. Outcomes following H+NE exposure included rapid efflux of K(+) and nucleic acids, increased membrane permeability and a reduction in both intracellular ATP and cell viability. Further inspection of morphology by electron microscopy highlighted cell shrinkage, membrane dissolution and bacteriolysis. Pathogen inactivation occurred immediately upon contact with H+NE. The effects of H, NE and H+NE against Enterococcus faecalis, Staphylococcus aureus and meticillin-resistant S. aureus isolates were also examined. Similar to the Escherichia coli model, H+NE showed antibacterial synergism in these organisms when classified by the Chou-Talalay combination index for two-agent interactions. This synergistic interaction suggests that the H+NE platform may potentially serve as a new paradigm in disinfectants, antiseptics and antibacterial wound dressings. The H+NE mechanism of action was termed osmopermeation, as a descriptor for the underlying inactivation process.

Concepts: Bacteria, Microbiology, Pneumonia, Staphylococcus aureus, Antibiotic resistance, Escherichia coli, Interaction, Antibiotic

28

Zygomycosis is characterized by tissue invasion with broad, non-septate hyphae of species such as Rhizopus, Rhizomucor, Lichtheimia (Absidia) and Basidiobolus. Basidiobolus ranarum usually causes subcutaneous infection, and gastrointestinal manifestations in immunocompetent patients have rarely been reported. It is difficult to diagnose gastrointestinal basidiobolomycosis because of the non-specific clinical presentation and the absence of a definite risk factor. This study identified 14 cases of gastrointestinal basidiobolomycosis, all of which were diagnosed after surgery by characteristic histopathological findings. Diagnosis of this disease requires a high index of suspicion in patients presenting with abdominal symptoms, fever, gastrointestinal mass and eosinophilia accompanied by a high erythrocyte sedimentation rate.

Concepts: Medical terms, Diagnosis, Red blood cell, Greek loanwords, Erythrocyte sedimentation rate, Zygomycota, Basidiobolus ranarum, Basidiobolomycosis

28

Proteus mirabilis is a common cause of urinary tract infection. Wild-type P. mirabilis strains are usually susceptible to penicillins and cephalosporins, but occurrences of P. mirabilis producing extended-spectrum β-lactamases (ESBLs) have been recently reported. Here, we surveyed the prevalence of cefotaxime resistance among P. mirabilis strains at seven different hospitals in Kanagawa Prefecture, Japan, and investigated their molecular epidemiology to explain the mechanism of their spread. The prevalence of cefotaxime resistance among P. mirabilis increased annually, from 10.1 % in 1998 to 23.1 % in 2003, and increased drastically in 2004, exceeding 40 %. We collected 105 consecutive and non-duplicate cefotaxime-resistant P. mirabilis isolates (MIC 16 to >256 µg ml(-1)) from these hospitals from June 2004 to May 2005 and characterized their profile. PCR and sequence analysis revealed that all resistant strains produced exclusively CTX-M-2 β-lactamase. PFGE analysis identified 47 banding patterns with 83 % or greater similarity. These results indicated that a regional outbreak of P. mirabilis producing CTX-M-2 β-lactamase has occurred in Japan and suggest that the epidemic spread occurred within and across hospitals and communities by extended clonal strains. Plasmid analysis revealed that 44.8 % of plasmids harboured by bla(CTX-M-2) isolates had common profiles, encoding ISEcp1, IS26 and Int1, and belonged to incompatibility group T. Spread of the resistant isolates in Japan resulted from dissemination of narrow-host-range plasmids of the IncT group encoding bla(CTX-M-2). These findings indicate the rapidly developing problem of treating the species to prevent dissemination of ESBL producers.

Concepts: Epidemiology, Urinary tract infection, Plasmid, Urease, Prefectures of Japan, Proteus mirabilis, Honshū, Kanagawa Prefecture

28

Biofilm resistance mechanisms are multifactorial and vary from one organism to another. The purpose of this study was to investigate linezolid’s efficacy against indwelling device-related methicillin-resistant Staphylococcus epidermidis (MRSE) biofilm, and compared with others antimicrobials. Minimal inhibitory concentrations (MICs), minimum biofilm inhibitory concentrations (MBICs) and minimum biofilm eradication concentrations (MBECs) were determined by the microtiter plate method. Fourteen and thirteen isolates from patients with indwelling device-related bacteremia and indwelling device colonization, respectively, were assessed. High MBIC was associated with high intensity of biofilm formation (gentamicin r = 0.796; linezolid r = 0.477; rifampicin r = 0.634; tigecycline r = 0.410 and vancomycin r = 0.771), but this correlation was not observed with MBEC. Linezolid demonstrated better in vitro antimicrobial activity than other antimicrobials (MBIC: gentamicin P < 0.001, rifampicin P = 0.019, vancomycin P = 0.008; MBEC: gentamicin P < 0.001, rifampicin P = 0.002, vancomycin P < 0.001). Biofilm growth inhibition was strongly associated with biofilm formation intensity; however biofilm eradication was not cell number dependent. MRSE biofilms eradication would represent a huge advance for indwelling device-related bacteremia, although high concentrations of gentamicin, linezolid, rifampicin, tigecycline and vancomycin were required for that. In general, linezolid reached better in vitro concentrations and demonstrated to be highly active against MRSE biofilms by inhibiting their growing when forming biofilm.

Concepts: Bacteria, Microbiology, Staphylococcus aureus, Antibiotic resistance, Methicillin-resistant Staphylococcus aureus, Biofilm, Antimicrobial, Staphylococcus epidermidis

27

MRSA infections represent a major threat world-wide and there are still several concerns regarding its treatment. Although vancomycin is the drug of choice, clinical failure in patients with serious gram-positive infections have been increasingly reported with an higher risk with increasing vancomycin MICs, well within the susceptible range. We tested daptomycin and telavancin in vitro activity against MRSA strains with vancomycin MIC 2 µg/ml selection. Daptomycin and telavancin seems to represent a good alternative for the treatment of infections caused by MRSA strains with a vancomycin MIC 2 µg/ml even in the presence of cell wall thickening.

Concepts: Bacteria, Staphylococcus aureus, Antibiotic resistance, Methicillin-resistant Staphylococcus aureus, Linezolid, Vancomycin, Daptomycin, Vancomycin-resistant Staphylococcus aureus

27

Demodex mites as a cause of facial rash in immunosuppressed patients have been reported in past. We report here an interesting case of possible demodicosis associated with rhinocerebral mucormycosis. The association of mites and the fungus were detected on direct microscopic examination of the scrapings of the nasal ulcer. The mite and the fungus were identified as Demodex folliculorum and Apophysomyces elegans complex respectively.

Concepts: Species, Acari, Demodex, Demodex folliculorum, Demodex brevis

27

The prevalence of dental caries continues to increase and novel strategies to reverse this trend appear necessary. The probiotic Streptococcus salivarius strain M18 offers potential to confer oral health benefits since it produces a) bacteriocins targeting the important cariogenic species Streptococcus mutans and b) the enzymes dextranase and urease, which could help reduce dental plaque accumulation and acidification respectively. In a randomised double-blind, placebo-controlled study of 100 dental caries- active children, treatment with strain M18 was administered for three months and the participants were assessed for changes to their plaque score, gingival and soft tissue health and to their salivary levels of S. salivarius, Streptococcus mutans, lactobacilli, beta haemolytic streptococci and Candida species. At treatment end, the plaque scores were significantly (P=0.05) lower for children in the M18-treated group especially in subjects having high initial plaque scores. The absence of any significant adverse events supported the safety of the probiotic treatment. Cell culture analyses of sequential saliva samples showed no differences between the probiotic and placebo groups in the counts of the specifically-enumerated oral microorganisms, with the exception of that subgroup of the M18-treated children who appeared to have colonised most effectively with M18. This subgroup exhibited reduced S. mutans counts, indicating that the anti-caries activity of M18 probiotic treatments may be enhanced if the efficiency of colonisation is increased. It is concluded that S. salivarius M18 can provide oral health benefits when taken regularly.

Concepts: Streptococcus, Dental caries, Lactobacillus, Dental plaque, Streptococcaceae, Streptococcus mutans, Oral microbiology, Streptococcus salivarius

27

Candida species are responsible for many opportunistic fungal infections. Fluconazole is a well-tolerated antifungal drug, commonly used in the treatment of Candidiasis. However, with fluconazole resistance ever increasing, rapid detection and antifungal susceptibility testing of Candida is imperative for proper patient treatment. Presented herein is a cost-effective, simple, and rapid chromogenic agar dilution method for simultaneous Candida species identification and fluconazole susceptibility testing. The results obtained by X-Plate Technology were in absolute concordance with standard microbroth dilution assays. Analysis of 1383 clinical patient samples with suspected vulvovaginal Candidiasis revealed that this technology was able to detect and speciate the Candida isolate and determine the fluconazole susceptibility. The prevalence and susceptibility profiles of the clinical isolates using this method were highly similar to published reports using the microbroth dilution method.

Concepts: Opportunistic infection, Antifungals, Candidiasis, Antifungal drug, Athlete's foot, Fluconazole, Griseofulvin, Ketoconazole

27

Dengue fever is re-emerging as a major scourge in south-east Asian countries affecting about 50-100 million people and causing about 25,000 mortality annually. India as a whole is under the risk of infection of this disease. We genetically characterized viruses causing Dengue infections in Kerala, one of the worst affected states of the Country during the disease outbreaks 2008-2010. All the 4 serotypes of the virus: DENV-1, DENV-2, DENV-3 & DENV-4 were found to be prevalent in the state. The genotypes recognized for these were III, IV, III and I respectively. The phylogenetic analysis evidenced that the re-emergence of serotype DENV-4 reported in Maharashtra and Andhra Pradesh recently, is spreading to different regions of the Country. The circulation of all the 4 Dengue serotypes in Kerala, may lead to increase in the prevalence of more severe complications of this emerging disease, such as Dengue Hemorrhagic fever and Dengue shock syndromes.

Concepts: Disease, Virus, Infection, Ribavirin, Fever, Dengue fever, Dengue, States and territories of India