Identification Of Gram-positive Bacteria Research Articles

Isolation and Identification of Gram-Positive Bacteria from the Epidermis of Students of Nnamdi Azikiwe University, Awka

Isolation and Identification of Gram-Positive Bacteria from the Epidermis of Students of Nnamdi Azikiwe University, Awka

Rapid Detection and Identification of Vancomycin-Sensitive Bacteria Using an Electrochemical Apta-Sensor.

In order to combat the complex and diverse infections caused by bacteria, it is essential to develop efficient diagnostic tools. Current techniques for bacterial detection rely on laborious multistep procedures, with high costs and extended time of analysis. To overcome these limitations, we propose here a novel portable electrochemical biosensor for the rapid detection and identification of Gram-positive bacteria that leverages the recognition capabilities of vancomycin and aptamers. A vancomycin-modified screen-printed carbon electrode was used to selectively capture Gram-positive bacteria susceptible to this antibiotic. Electrochemical impedance spectroscopy and scanning electron microscopy demonstrated that capture was achieved in 10 min, with a limit of detection of only 2 CFU/mL. We then tested the device's potential for aptamer-based bacterial identification using Staphylococcus aureus and Bacillus cereus as the test strains. Specifically, electrodes with captured bacteria were exposed to species-specific aptamers, and the resulting changes in current intensity were analyzed using differential pulse voltammetry. When used directly in untreated milk or serum, the system was able to successfully identify a small amount of S. aureus and B. cereus (100 CFU/mL) in less than 45 min. This novel biosensor has the potential to serve as an invaluable tool that could be used, even by inexperienced staff, in a broad range of settings including clinical diagnostics, food safety analysis, environmental monitoring, and security applications.

Multi-drug and biocide-resistant Gram-positive bacteria prevalent on surfaces of veterinary clinics in Benue State, Nigeria

Objective: In this study, the common aerobic Gram-positive bacteria (GPB) contaminating veterinary clinic surfaces were isolated, and their susceptibility to antimicrobial agents (antibiotics and biocides) was determined. Materials and Methods: Standard cultural and biochemical procedures were used to process 62 swab samples collected from different surfaces in 4 veterinary clinics for the isolation and identification of GPB. The agar dilution technique was used to determine the sensitivity of the isolates to disinfectants, while the disc diffusion technique was used to determine the sensitivity to antibiotics. Results: Isolation rates in veterinary clinics I, II, III, and IV were 39.4%, 40.4%, 7.4%, and 12.8%, respectively. GPB were isolated from all the surfaces sampled. A total of 94 GPB isolates were recovered, comprising Bacillus species (51.1%), Staphylococcus species (38.3%), Corynebacterium species (6.4%), and Enterococcus species (4.3%). Only 13.8% of the GPB were resistant to at least one of the biocides tested. Multiple drug resistance to at least three classes of antimicrobial agents was exhibited by 95% of the isolates tested. Conclusion: The results of this study suggest that veterinary clinic environments and surfaces in Makurdi are reservoirs of wide varieties of antimicrobial-resistant GPB of veterinary and public health importance.

Sepsityper® Kit versus In-House Method in Rapid Identification of Bacteria from Positive Blood Cultures by MALDI-TOF Mass Spectrometry.

In order to further accelerate pathogen identification from positive blood cultures (BC), various sample preparation protocols to identify bacteria with MALDI-TOF MS directly from positive BCs have been developed. We evaluated an in-house method in comparison to the Sepsityper® Kit (Bruker Daltonics, Bremen, Germany) as well as the benefit of an on-plate formic acid extraction step following positive signal by the BACTECTM FX system. Confirmation of identification was achieved using subcultured growing biomass used for MALDI-TOF MS analysis. A total of 113 monomicrobial positive BCs were analyzed. The rates of Gram-positive bacteria correctly identified to the genus level using in-house method and Sepsityper® Kit were 63.3% (38/60) and 81.7% (49/60), respectively (p = 0.025). Identification rates at species level for Gram-positive bacteria with in-house method and Sepsityper® kit were 30.0% (18/60) and 66.7% (40/60), respectively (p < 0.001). Identification rates of Gram-negative bacteria were similar with the in-house method and Sepsityper® Kit. Additional on-plate formic acid extraction demonstrated significant improvement in the identification rate of Gram-positive bacteria at both genus and species level for both in-house (p = 0.001, p < 0.001) and Sepsityper® Kit methods (p = 0.007, p < 0.001). Our in-house method is a candidate for laboratory routines with Sepsityper® Kit as a back-up solution when identification of Gram-positive bacteria is unsuccessful.

Cationic porphyrin-based nanoparticles for photodynamic inactivation and identification of bacteria strains.

The emergence of antibiotic drug resistance has undermined the efficacy of antibiotics, and is becoming a severe threat to public health. To combat antibiotic drug resistance and to replace traditional antibiotic treatment, an alternative strategy based on antibacterial photodynamic therapy (APDT), which has broad applicability, high efficiency and less potential of developing antibiotic drug resistance, has been developed. In this work, the cationic porphyrin-based nanoparticles (NPs) were prepared by epoxy-amine chain extension polymerization of diepoxy-terminated poly(ethylene glycol) (PEG) and tetraamino-containing porphyrin, followed by quaternization with methyl iodine and butyl bromide. The as-obtained cationic porphyrin NPs preserved the photophysical properties of porphyrin derivatives, and can efficiently generate singlet oxygen (1O2) under 635 nm laser irradiation. The cationic porphyrin-based NPs displayed intrinsic antibacterial properties, and exhibited strong APDT effect on Gram-positive bacteria by destroying the bacterial cell membranes. Upon incubation with different bacterial strains, it was found that they could be utilized to identify Gram-positive bacteria by observing the sedimentation behavior of their mixtures, and visualizing their co-cultured and centrifugal bacteria cakes. In addition, the cationic porphyrin-based NPs had good hemocompatibility and low dark cytotoxicity.

Multicenter Evaluation of Rapid BACpro® II for the Accurate Identification of Microorganisms Directly from Blood Cultures Using MALDI-TOF MS.

The identification of microorganisms directly from blood cultures using MALDI-TOF MS has been shown to be the most impacting application of this methodology. In this study, a novel commercial method was evaluated in four clinical microbiology laboratories. Positive blood culture samples (n = 801) were processed using a rapid BACpro® II kit and then compared with the routine gold standard. A subset of monomicrobial BCs (n = 560) were analyzed in parallel with a Sepsityper® Kit (Bruker Daltonics, Bremen, Germany) and compared with the rapid BACpro® II kit. In addition, this kit was also compared with two different in-house methods. Overall, 80.0% of the monomicrobial isolates (609/761; 95% CI 71.5–88.5) were correctly identified by the rapid BACpro® II kit at the species level (92.3% of the Gram negative and 72.4% of the Gram positive bacteria). The comparison with the Sepsityper® Kit showed that the rapid BACpro® II kit generated higher rates of correct species-level identification for all categories (p > 0.0001), except for yeasts identified with score values > 1.7. It also proved superior to the ammonium chloride method (p > 0.0001), but the differential centrifugation method allowed for higher rates of correct identification for Gram negative bacteria (p > 0.1). The percentage of accurate species-level identification of Gram positive bacteria was particularly noteworthy in comparison with other commercial and in-house methods.

Naphthalimide-based multifunctional AIEgens: Selective, fast, and wash-free fluorescence tracking and identification of Gram-positive bacteria

Pathogenic infections, particularly caused by Gram-positive bacteria (G+), pose a serious threat to human health, and therefore the fast and accurate discrimination of G+ bacteria from Gram-negative bacteria (G–) and fungi is highly desirable. Organic molecules with facile synthesis, robust photostability, good biocompatibility, and high selectivity toward pathogens are urgently needed in the clinical diagnosis and therapy. To this end, herein we report the synthesis of two naphthalimide-based bioprobes named tetraphenylethylene-naphthalimide (TPE-NIM) and triphenylamine-naphthalimide (TPA-NIM) with aggregation-induced emission (AIE) characteristic. First, the staining capacity of the designed AIEgens toward six kinds of bacteria and two kinds of fungi was evaluated. Both TPE-NIM and TPA-NIM showed a high degree of binding/imaging selectivity for G+ bacteria over G− bacteria and fungi via a wash-free protocol. Second, the two AIEgens had the ability to visualize the biofilms formed by G+ bacteria (Staphylococcus aureus) and can quickly track the G+ bacteria (Staphylococcus aureus) in red blood cell suspensions. Third, we have revealed that electrostatic attraction and hydrophobic interaction both contribute to the selective binding of the AIEgens toward G+ bacteria. In view of the high binding/imaging specificity toward G+ bacteria, low hemolysis rates, and low toxicity toward the bacterial cells, these AIEgens can be applied for the clinical detection of pathogenic infections caused by G+ bacteria and broaden the theranostic applications of AIE materials.

Identification of Gram Positive Bacteria Involved in Yolk Sac Infection

Yolk sac infection is one of the most important diseases in broiler chicken during first week of their life. The disease is prevalent in many flocks in Iran. As bacteria penetrate into yolk sac, immune system and antibodies can't destroy them, since yolk sac does not contain blood vessels. Therefore, identification of causal agents is important in prevention and control of the disease. In this report field outbreaks have been studied to determine the prevalent gram-positive bacterial types involved in yolk sac infection. In this study, during one-year period from March 1999 till March 2000; 210 carcasses of broiler chicks with yolk sac infection from 21 broiler-breeding farms were put under investigation. These farms were in suburbs of Mashhad and Ghaen cities in Khorasan province in north east of Iran. Ten carcasses with yolk sac infection from each flock were sampled. The carcasses of the chicks were emaciated and smaller. The yolk sacs were found to be distended containing foul smelling yolk material. The color of the yolk varied from greenish yellow; dark brown to bright yellow. In some, the yolk material was almost completely solid whereas in some the consistency was watery. Yolk sac material were collected aseptically from five carcasses and together cultured on different media for isolation of causative agents. The media used for first isolation were: blood agar with and without potassium tellorite, thioglicolate broth and manitol salt agar. Inoculated media incubated in aerobic and anaerobic conditions at 37°C. Then developed colonies depended on macroscopic and microscopic appearance, subcultured on appropriate differential media for identification of genus and species of bacteria. Results showed that streptococcus species were isolated from 21 flocks (100% flocks). Staphylococcus species were recovered from 15 flocks (71.41%). Bacillus cereus was isolated from 6 flocks (28.57%), and Clostridium perfringens from 2 flocks (9.52%). Pure culture of streptococcus spp. from 4 flocks (19/04%) isolated. The prevalence of mixed infections were: staphylococcus and streptococcus spp. from 10 flocks (47/61%); staphylococcus, streptococcus and clostridium spp. from one flock (4/76%); staphylococcus, streptococcus, bacillus and clostridium spp. from one flock (4/76%); staphylococcus, streptococcus and bacillus spp. from 3 flocks (14/28%); streptococcus and bacillus spp. from 2 flocks (9/52%). Isolated streptococcus species included: avium, durans, faecium, faecalis, porcinus and isolated staphylococcus species included: aureus, hycus, gallinarus and epidermidis. However, isolated bacteria in this study contain enzymatic systems of lipase, protease and lecithinase, which are able to digest protein of yolk, so they provide opportunity for other invader bacteria to complicate infection. The present investigation throws light on the possibility of severity of yolk sac infection and chick mortality in poultry industry due to bacterial flora, if proper sanitary and strict precautionary measures were not undertaken at every step, before, during and soon after hatching of eggs. 276

The analysis of actinomycete wall amino acids by gas chromatography

1. INTRODUCTION 2. MATERIALS AND METHODS Since the early work of Cummins and Harris [1] cell wall analysis has become a widely used tech- nique in both the classification and identification of Gram-positive bacteria [2]. Methods for de- termining wall amino acids include paper chro- matography, thin-layer chromatography (TLC) and ion exchange chromatography using the amino acid analyser; the latter being the method of choice where quantitative data are required [3]. Paper chromatography and TLC have been used prim- arily to provide a rapid qualitative assessment of the wall amino acid composition and to detect diagnostic diamino acids [4,5]. An established technique, applied only rarely to bacterial amino acids [6,7], is the conversion of amino acids into volatile derivatives and their analysis by gas chro- matography (GC) [8]. This approach is of poten- tial value since it provides reliable quantitative data on wall amino acids without the use of an amino acid analyser. This paper reports on the application of GC to the analysis of wall amino acids from selected defatted actinomycetes.