Is adherence to national guidelines for parenteral empiric antibiotic therapy effective? Experience from a Sri Lankan center.

INTRODUCTION: Guidelines for the selection of empirical antibiotics have been developed to improve patient outcomes and reduce unnecessary antibiotic use. We assessed the extent of adherence to the national guidelines for the selection of parenteral empirical antibiotics for three selected infections at a tertiary care center. METHODOLOGY: A prospective cross-sectional study was conducted in medical and surgical wards of a tertiary care hospital in Sri Lanka. Adult patients with a positive culture for a lower respiratory tract infection (LRTI), skin and soft tissue infection (SSTI), or urinary tract infection (UTI) and who were prescribed parenteral empirical antibiotic therapy by the attending physician were included. Bacteria were identified and antibiotic susceptibility was determined by standard microbiological methods. Adherence to the guidelines was defined as prescribing the empiric antibiotic concordant with the national guidelines on the empirical use of antibiotics. RESULTS: A total of 160 bacterial isolates were obtained from 158 patients with positive cultures, the majority were from UTIs (n = 56). The selection of empirical antibiotics was concordant with the national guidelines in 92.4% of patients and 29.5% of the bacterial isolates obtained from these patients were resistant to the prescribed empiric antibiotic. Only 47.5% (76/160) of the bacterial isolates were sensitive to the empiric antibiotic and therefore can be considered an appropriate antibiotic prescription. CONCLUSIONS: Empirical antibiotic guidelines should be updated based on the latest surveillance data and information on prevailing bacterial spectra. Antibiotic prescribing patterns and guideline concordance should be periodically evaluated to ensure whether antimicrobial stewardship programs are moving in the right direction.

Antibiotic Sensitivity of Group B Streptococcus from Pregnant Mothers and Its Association with Resistance Genes.

OBJECTIVE: This study assessed the antibiotic susceptibility and characterized antibiotic resistance genes of group B Streptococcus (GBS) isolates from selected tertiary care hospitals in Western Province, Sri Lanka. METHODS: A descriptive cross-sectional study was carried out to determine antibiotic sensitivity of GBS among 175 pregnant women of >35 weeks of gestation attending antenatal clinics in four teaching hospitals. Low vaginal and rectal swabs were collected separately, and GBS was identified by standard microbiological methods. Antibiotic sensitivity and minimum inhibitory concentration (MIC) were performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. DNA was extracted from culture isolates, and antibiotic-resistant genes were identified by polymerase chain reaction using ermB, ermTR, mefA, and linB genes. RESULTS: GBS colonization in the study sample was 25.7% (45/175) with detection rate of 22.9% (40/175) and 2.9% (5/175) in vaginal and rectal samples, respectively. All isolates were susceptible to penicillin with an MIC range of 0.03-0.12 µg/mL. Six isolates (13.3%) were intermediate, and 11 isolates (24.4%) were resistant to erythromycin. There were 5 intermediately resistant isolates (11.1%) and 10 resistant isolates (22.2%) for clindamycin. Of them, seven had inducible clindamycin resistance (iMLSB). MIC range of erythromycin was 0.03-0.32 µg/mL and that of clindamycin was 0.06-0.32 µg/mL. ermB gene was detected in 7 (15.5%). ermTR gene was found in 16 (35.6%) and was significantly associated with iMLSB phenotype (p = 0.005). mefA gene was detected in two (4.4%) isolates, while linB gene was not detected in tested isolates. CONCLUSION: All isolates were sensitive to penicillin, and the most prevalent resistance genotype was ermTR in the study population.

Health-related quality of life in patients with substance use disorders enrolled to the residential treatment in Sri Lanka: a retrospective cross-sectional study.

PURPOSE: Substance use disorder (SUD) is a serious public health concern that requires continuum care with effective treatment modalities such as residential rehabilitation. Improvement in health-related quality of life (HRQoL) is one of the determinants of treatment and rehabilitation effectiveness. Therefore, a retrospective cross-sectional study was carried out in seven residential rehabilitation centres in Sri Lanka to determine the HRQoL of the rehabilitees with SUD. METHOD: The HRQoL of 464 individuals at their enrolment and during the rehabilitation period was assessed using EuroQol five-level five-dimensional questionnaire (EQ-5D-5L). Data were analysed using IBM SPSS version 26. RESULTS: The majority of the participants were Sinhala (n = 419, 90.3%) and Buddhist (n = 368, 79.3%) males (n = 461, 99.4%). Most were unmarried (n = 302, 65.1%), young adults (n = 385, 83.0%) who have pursued secondary or higher education (n = 276, 59.5%) and 87.3% were employed (n = 405). Most of the selected centres use biopsychosocial model (n = 4, 57.1%) as the rehabilitation approach while rest practice therapeutic community (n = 3, 42.9%). The average EQ-5D-5L index [range =( - 0.45)-1.00] of the rehabilitees at their enrolment was 0.52 ± 0.28 and the EQ-5D-5L Visual Analogue Scale (EQ-5D-5L VAS) score (range = 0-100%) was 47.17% ± 23.48%. The values were increased up to 0.83 ± 0.18 (EQ-5D-5L index) and 84.25% ± 16.79% (EQ-5D-5L VAS) during the rehabilitation period. Only 19.4% of the rehabilitees had a normal or upper normal HRQoL (≥ 0.75 EQ-5D-5L Index) at their enrolment and 72.2% of rehabilitees reported normal or upper normal HRQoL during the rehabilitation period. CONCLUSION: A significant improvement in the HRQoL of the participants was observed during the residential treatment in comparison to the enrolment, despite the differences in the rehabilitation programs.

The Pattern of Substance Use and Characteristics of the Individuals Enrolled in Residential Treatment at Selected Rehabilitation Centers in Sri Lanka: A Descriptive Cross-Sectional Study.

Introduction: Substance use becomes censorious when it leads to harmful effects on individuals, their families, and the community. The nature of substance use in Sri Lankan context is poorly understood and empirical evidences are sparse. The study aimed to describe patterns of substance use and characteristics of the individuals enrolled in residential treatment at selected rehabilitation centers in Sri Lanka. Material and methods: A descriptive cross-sectional study was conducted among 205 individuals enrolled in selected rehabilitation centers. Pretested interviewer-administered questionnaire was used to collect data. Data were analyzed using descriptive statistics. Results: Most of the individuals who enrolled in residential treatment at selected rehabilitation centers were unmarried (n = 124, 60.5%), Sinhala (n = 186, 90.7%), Buddhist (n = 166, 81.0%), males (n = 202, 98.5%) and belonged to the young adult age (18-35 years) category (n = 178, 86.8%). All the participants were poly-drug users and cannabis was the most commonly used (n = 183, 89.3%) illicit drug followed by heroin (n = 172, 83.9%), methamphetamine (n = 150, 73.2%) and cocaine (n = 78, 38%). The most (n = 152, 74.1%) problematic substance for life was heroin. Most of the participants (n = 149, 72.7%) had used drugs several times per day. The mean duration of substance use was 7 ± 5 years. Participants (n = 177, 86.3%) reported that the substances were available in their residential areas and their friends (n = 197, 96.1%) were also using the substances. Conclusions: Pattern of substance use and characteristics of the individuals were unique in Sri Lanka and need to be considered when implementing and strengthening the programs for drug prevention and rehabilitation.

The genotypes and virulence attributes of C. albicans isolates from oral leukoplakia / Los genotipos y atributos de virulencia de aislamientos de C. albicans de leucoplasia oral

Background: There is a debate as to whether some types of oral leucoplakias (OL) are caused by Candida species,and whether they contribute to the malignant transformation, associated with a minority of such lesions. As nodetailed population analysis of yeast isolates from OL is available, we evaluated the virulence attributes, and geno-types of 35 C. albicans from OL, and compared their genotypes with 18 oral isolates from healthy individuals.Material and Methods: The virulence traits evaluated were esterase, phospholipase, proteinase, haemolysin andcoagulase production, and phenotypic switching activity, and yeast adherence and biofilm formation. DNA fromOL and control yeasts were evaluated for A, B or C genotype status.Results: Phospholipase, proteinase, and coagulase activity and biofilm formation was observed in 80%, 66%, 97% and 77 % of the isolates, respectively. Phenotypic switching was detected in 8.6%, while heamolytic, and ester-ase activity and adherence were noted in all isolates.Conclusions: The genotype A was predominant amongst both the OL and control groups. Due to the small samplesize of our study a larger investigation to define the role of candidal virulent attributes in the pathogenicity of OLis warranted, and the current data should serve as a basis until then.(AU)

Appropriateness of the Empirical Antibiotics Prescribed and Their Concordance with National Guidelines for Three Selected Infections among Cancer Patients in a Tertiary Care Centre in Sri Lanka.

BACKGROUND: Prophylactic and empirical antibiotic use is essential in cancer patients due to the underlying immune deficiencies. We examined the spectrum of causative bacteria and the appropriateness of empirical antibiotic prescription for three selected infections in cancer patients. Methodology. A descriptive cross-sectional study was conducted at the National Institute of Cancer (NIC), Sri Lanka, from June 2018 to February 2019. Bacterial isolates obtained from adult cancer patients with a diagnosis of lower respiratory tract infections (LRTI), skin and soft tissue infections (SSTI), or urinary tract infections (UTI) were included. Causative bacteria were identified and the antibiotic susceptibility was determined by standard microbiological methods. Empirical therapy was defined as appropriate if the isolated pathogen was susceptible in vitro to the given antibiotic. RESULTS: A total of 155 bacterial isolates were included in the analysis. LRTI were the most prevalent infections (37.2%, 55/148) encountered during the study period. Majority (90.9%) of the isolated bacteria were ESKAPE pathogens. Klebsiella pneumoniae was the most frequent pathogen causing LRTI (42.4%, 25/59), whereas Escherichia coli (32%, 16/50) and Staphylococcus aureus (26.1%, 12/46) predominated in UTI and SSTI, respectively. Meropenem was the most prescribed empirical antibiotic for LRTI (29.1%, 16/55) and SSTI (26.6%, 11/43) while it was ceftazidime for UTI (36%, 18/50). Only 20.6% (32/155) of the isolated bacteria were susceptible to the empirical antibiotic prescribed while 48.4% (75/155) were resistant to them. The prescribed empirical antibiotic did not have the spectrum of activity for the isolated bacteria in 29% (45/155) of cases. CONCLUSION: High resistance rates were observed against the prescribed empirical antibiotics. National empirical antibiotic guidelines should be revised with updated data on causative organisms and their susceptibility patterns to ensure appropriate empirical antibiotic prescription.

Importance of KIM-1 and MCP-1 in Determining the Leptospirosis-Associated AKI: A Sri Lankan Study.

BACKGROUND: Acute kidney injury (AKI) is one of most prevalent and serious complications of leptospirosis, a prevalent zoonotic disease in tropical countries. Prompt diagnosis of the leptospirosis-associated AKI is a challenge as there are no proper diagnostic tools that can identify patients in the early stage. Kidney injury molecule-1 (KIM-1) and monocyte chemoattractant protein-1 (MCP-1) are widely used novel AKI biomarkers that are studied in various disease conditions with AKI, but not in leptospirosis. Thus, this study is aimed at seeking the importance of KIM-1 and MCP-1 in determining the leptospirosis-associated AKI. METHODS: Leptospirosis-suspected patients who were admitted to medical wards of two selected hospitals in the Western province of Sri Lanka were recruited. Leptospirosis was confirmed by three diagnostic tests: PCR, MAT, and culture, and the status of AKI was determined by Kidney Disease Improving Global Outcomes (KDIGO) criteria. RESULTS: Of 170 leptospirosis-suspected patients, 79 were leptospirosis confirmed, and among them, 24.05% of patients were diagnosed to have AKI according to KDIGO criteria. Median serum KIM-1 (p < 0.0001), urine KIM-1 (0.0053), serum MCP-1 (0.0080), and urine MCP-1 (0.0019) levels in those developing AKI were significantly higher than in patients not developing AKI. The biomarker levels associated with leptospirosis AKI had AUC-ROC of 0.8565, 0.7292, 0.7024, and 0.7282 for serum KIM-1, urine KIM-1, serum MCP-1, and urine MCP-1, respectively. CONCLUSION: This study revealed serum KIM-1 as a promising marker for leptospirosis-associated AKI among the tested biomarkers. Thus, further validation is recommended with a larger study group.

Contributing role of TNF, IL-10, sTNFR1 and TNF gene polymorphisms in disease severity of leptospirosis.

The immune response is hypothesized as an important factor in the disease outcome of leptospirosis. Exaggerated immune response may promote tissue damage that lead to severe disease outcome. In this study TNF, IL-10, sTNFR1 levels were measured among sixty-two hospitalized leptospirosis confirmed patients in Sri Lanka. Thirty-one serum samples from healthy individuals were obtained as controls. PCR-RFLP method was used to identify TNF gene polymorphisms and to determine their association with TNF expression and disease severity in leptospirosis. TNF (p = 0.0022) and IL-10 (p < 0.0001) were found to be significantly elevated in leptospirosis patients, while sTNFR1 (p < 0.0001) was significantly suppressed. TNF was not significantly elevated in patients with complications while the anti-inflammatory cytokine IL-10 was significantly elevated among patients with complications (p = 0.0011) and with mortality (p = 0.0088). The ratio of IL-10 to TNF was higher among patients with complications (p = 0.0008) and in fatal cases (p = 0.0179). No association between TNF gene polymorphisms and TNF expression was detected due to the low frequency of heterozygous and mutated genes present in this study population. Thus the findings of the study show that elevated levels of IL-10 in the acute phase of disease could lead to severe outcomes and a high IL-10/TNF ratio is observed in patients with complications due to leptospirosis.

In -vitro Biofilm Formation of Vaginal Isolates of Streptococcus agalactiae; Effect of pH and Culture Media

Abstract Background: Streptococcus agalactiae (GBS), a major cause of neonatal morbidity and mortality, is transmitted from mother to neonate via placenta or during birth. Biofilm formation is an important factor in GBS pathogenesis. This study aimed to determine effects of pH, different culture media and nutritional composition on in vitro biofilm forming ability of GBS isolated from pregnant women. Methods: A total of 30 confirmed isolates of GBS from pregnant women were tested for biofilm formation in Todd Hewitt Broth (THB) at pH 4.5,6 and 7. Ten of these isolates were tested for biofilm formation in growth media THB, brain heart infusion broth, tryptic soy broth, Mueller Hinton broth and nutrient broth. Further they were tested for influence of glucose on biofilm formation using crystal violet and MTT assay. Results: Of 30 GBS isolates strong biofilm formation (SBF) was observed at pH 7 in 56.6 %(n=17) while 36.6%(n=11) isolates showed weak biofilm formation (WBF). At pH 4.5, 43.3% (n=13) were non biofilm formers. In THB without glucose, all 10 isolates were SBF while THB with 1% glucose, 3(30%) isolates were SBF, 5(50%) isolates were moderate biofilm producers and 2(20%) isolates were WBF. Ten isolates tested in 5 types of growth media did not show statistically significant difference in biofilm forming ability. Conclusion: All tested vaginal GBS isolates were able to produce biofilms, maximum biofilm formation of GBS was at pH 7.0. and pH 4.5 is not favorable, thus in normal vaginal pH (3.5 - 4.5), GBS finds it difficult to grow biofilms.

Correction to: Evaluation of the impact of six different DNA extraction methods for the representation of the microbial community associated with human chronic wound infections using a gel­based DNA profiling method.

An amendment to this paper has been published and can be accessed via the original article.

Salmonella enterica serovar Paratyphi A isolated from a hard-to-heal diabetic ulcer: a case report.

Chronically infected diabetic wounds have a polymicrobial aetiology. However, Salmonella Paratyphi A is a very rare cause of wound infection. A 76-year-old female patient with type II diabetes presented with a wound on the left leg of two months' duration. The wound was painful, erythematous and a thick, foul-smelling discharge was present. There was a history of delayed wound healing. Salmonella Paratyphi A and Pseudomonas aeruginosa were isolated from the wound tissue. The patient was treated with cefuroxime and cloxacillin empirically and following the antibiotic susceptibility testing (ABST) report, ciprofloxacin was given for 10 days. The wound was treated with multiple debridements and topical antiseptic. On follow-up, the patient remained afebrile with subsiding discharge from the ulcer. This is the first reported case of Salmonella Paratyphi A from an infected diabetic ulcer in Sri Lanka and it serves to further define the spectrum of illnesses caused by this uncommon pathogen.

Type 2 diabetes mellitus and oral Candida colonization: Analysis of risk factors in a Sri Lankan cohort.

Aims: Oral candidiasis is a major oral manifestation of uncontrolled diabetes mellitus, and a number of cofactors are associated with the pathogenesis of this infection. Here, we describe the prevalence of oral Candida in a Sri Lankan cohort of type 2 diabetes mellitus and risk factors that predispose them to this common fungal infection. Methods: A case-control study was conducted in 250 diabetics with type 2 diabetes and 81 nondiabetic controls. Clinical and demographic data were collected using an interviewer administered questionnaire, and patient records. Oral rinse samples were collected to determine the candidal carriage, and the resultant yeast growth was quantified and speciated using multiplex-PCR and phenotypic analyses. Chi-square test (χ2 test) and Fisher exact test were used for the determination of the significant relationships between risk factors and oral candidiasis. Results: The oral prevalence of Candida species among both groups was similar (81%) although a significantly higher proportion of diabetics (32.8%) yielded >2000 CFU/mL of yeasts compared with only 12.3% of the healthy controls (p < .05). Significant associations were noted between oral candidal carriage amongst diabetics, and (i) denture wearing, (ii) female gender and (iii) cigarette smoking (all, p < .05). Amongst both groups, C.albicans was the most common Candida species isolated followed by C. parapsilosis, C. tropicalis and C. glabrata. Conclusions: The oral infestation of Candida in our Sri Lankan cohort of diabetics is significantly higher than their healthy counterparts, and co-carriage of multiple yeast species is a common finding in the study population. As there are no previous such reports of the latter phenomenon particularly from the Asian region it is noteworthy, mainly in view of the recent data on the emergence of drug-resistant yeast species the world over.

Do the Th17 Cells Play a Role in the Pathogenesis of Leptospirosis?

OBJECTIVES: The aim of this study was to determine the level of five different pro- and anti-inflammatory cytokines to study the inflammatory response of leptospirosis. MATERIALS AND METHODS: The serum cytokine levels of IL-10, IL-17A, IL-21, IL-23, and TNF-α were investigated in 57 patients with leptospirosis and 12 healthy controls using a commercially available ELISA kit (Mabtech, Sweden). Statistical analysis was done using Graphpad Prism. RESULTS: Elevation of serum IL-10 and IL-17A levels and significant elevation of serum IL-21 (p=0.002), IL-23 (p=0.002), and TNF-α (p=0.039) were observed among leptospirosis patients compared to the healthy control group. The two major complications observed among these patients were renal failure and liver involvement. Renal failure was significantly associated with elevation of IL-21 and IL-23, while patients with liver involvement had a significant elevation of IL-21, IL-23, and TNF-α. CONCLUSION: Elevation of IL-17A together with the significant elevation of IL-21 and IL-23 suggests a possible involvement of Th17 cells in the immunopathogenesis of leptospirosis.

Imprint cytology: a useful screening test for diagnosis of Helicobacter pylori in resource poor settings.

OBJECTIVE: The study aimed to compare the usefulness of two staining methods for imprint cytology for diagnosis of Helicobacter pylori infection. Gastric biopsy specimens (from dyspeptic patients attending routine upper gastrointestinal endoscopy) were placed on glass slides to obtain imprints. The imprints were stained with Toluidine blue and Giemsa stains separately and observed under ×400 magnification using a light microscope. Imprinted biopsies were sectioned and stained with H & E stain and Giemsa stain for histological analysis. Diagnosis of H. pylori infection in both imprint and histological sections were confirmed by a consultant pathologist. The sensitivity, specificity, positive predictive value and negative predictive value of each stain were calculated and benchmarked against histological diagnosis. RESULTS: Of the 55 dyspeptic patients enrolled in the study, 5 were positive for H. pylori by Toluidine blue stain and 4 by Giemsa stain. The sensitivity of Toluidine blue stain (57.1%) was higher than Giemsa stain (42.9%) while the specificity of both stains was equal (97.9%). Giemsa stain gave a better discrimination for identification of H. pylori bacteria among the mucosal background. Imprint cytology is a rapid, simple and cost effective diagnosis method that can supplement histological diagnosis.

Association of tumor necrosis factor alpha gene polymorphisms with Helicobacter pylori infection in dyspeptic patients in Sri Lanka.

Single nucleotide polymorphisms present on the promoter sequence of the TNF-α gene may affect production of TNF-α, a pro-inflammatory cytokine, during immune responses. The presence of TNF-α polymorphisms is also reportedly associated with more severe manifestations of Helicobacter pylori infection. However, the frequency of TNF-α polymorphisms and the associated disease severity vary between different patient groups. In this study, gastric biopsies and blood specimens were collected from 138 patients with dyspepsia undergoing routine upper gastrointestinal endoscopy. Our institution's Ethics Review Committee approved the study and written informed consent was obtained from all participants. The presence of H. pylori was confirmed histologically in all patients. The frequency of TNF-α polymorphisms in the study cohort was investigated using PCR-restriction fragment length polymorphism and expression of serum TNF-α quantitated using a commercial ELISA assay. The proportions of selected TNF-α polymorphisms (TNF-α -238, -308 and -863) were similar in H. pylori-positive and -negative patients. Homozygous mutations of TNF-α polymorphisms were rarely detected in the study group. There was a significant difference in TNF-α concentrations between patients with mild chronic gastritis and TNF-α -308 GG genotype and patients with moderate to severe chronic gastritis (P = 0.008). It was not possible to identify an association between these genotypes and disease severity because of the low frequency of heterozygous and homozygous mutated genes in Sri Lankan patients with dyspepsia.

The Effect of Nutritive and Non-Nutritive Sweeteners on the Growth, Adhesion, and Biofilm Formation of Candida albicans and Candida tropicalis.

OBJECTIVE: To determine the effect of glucose, sucrose, and saccharin on growth, adhesion, and biofilm formation of Candida albicans and Candida tropicalis. MATERIALS AND METHODS: The growth rates of mono-cultures of planktonic C. albicans and C. tropicalis and 1:1 mixed co-cultures were determined in yeast nitrogen broth supplemented with 5% (30 mM) and 10% (60 mM) glucose, sucrose, and saccharin, using optical density measurements at 2-h intervals over a 14-h period. Adhesion and biofilm growth were performed and the growth quantified using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The biofilm architecture was visualized using scanning electron microscopy. One- and two-way analysis of variance (ANOVA) was performed to analyse the differences among multiple means. RESULTS: The highest planktonic growth was noted in 5% glucose after 14 h (p < 0.05). No significant planktonic growth was observed in either concentration of saccharin. Both the concentrations of glucose and sucrose elicited significantly increased adhesion from MTT activity of 0.017 to >0.019 in mono- as well as co-cultures (p < 0.05), whilst the lower concentration of saccharin significantly dampened the adhesion. Maximal biofilm growth was observed in both species with the lower concentration of sucrose (5%), although a similar concentration of saccharin abrogated biofilm development: the highest MTT value (>0.35) was obtained for glucose and the lowest (>0.15) for saccharin. CONCLUSION: In this study, glucose and sucrose accelerated the growth, adhesion, and biofilm formation of Candida species. However, the non-nutritive sweetener saccharin appeared to dampen, and in some instances suppress, these virulent attributes of Candida.

Evaluation of the impact of six different DNA extraction methods for the representation of the microbial community associated with human chronic wound infections using a gel-based DNA profiling method.

Infected chronic wounds are polymicrobial in nature which include a diverse group of aerobic and anaerobic microorganisms. Majority of these communal microorganisms are difficult to grow in vitro. DNA fingerprinting methods such as polymerase chain reaction-denaturation gradient gel electrophoresis (PCR-DGGE) facilitate the microbial profiling of complex ecosystems including infected chronic wounds. Six different DNA extraction methods were compared for profiling of the microbial community associated with chronic wound infections using PCR-DGGE. Tissue debris obtained from chronic wound ulcers of ten patients were used for DNA extraction. Total nucleic acid was extracted from each specimen using six DNA extraction methods. The yield, purity and quality of DNA was measured and used for PCR amplification targeting V2-V3 region of eubacterial 16S rRNA gene. QIAGEN DNeasy Blood and Tissue Kit (K method) produced good quality genomic DNA compared to the other five DNA extraction methods and gave a broad diversity of bacterial communities in chronic wounds. Among the five conventional methods, bead beater/phenol-chloroform based DNA extraction method with STES buffer (BP1 method) gave a yield of DNA with a high purity and resulted in a higher DGGE band diversity. Although DNA extraction using heat and NaOH had the lowest purity, DGGE revealed a higher bacterial diversity. The findings suggest that the quality and the yield of genomic DNA are influenced by the DNA extraction protocol, thus a method should be carefully selected in profiling a complex microbial community.

Biosynthesized silver nanoparticles: are they effective antimicrobials?

BACKGROUND: Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required. OBJECTIVES: This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853. METHODS: Culture conditions (AgNO3 concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy. FINDINGS: The characteristic UV-visible absorbance peak was observed in the 420-430 nm range. Most of the particles were spherical in shape within a size range of 33-300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans. MAIN CONCLUSION: As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

Biosynthesized silver nanoparticles: are they effective antimicrobials?

BACKGROUND Silver nanoparticles (AgNPs) are increasingly being used in medical applications. Therefore, cost effective and green methods for generating AgNPs are required. OBJECTIVES This study aimed towards the biosynthesis, characterisation, and determination of antimicrobial activity of AgNPs produced using Pseudomonas aeruginosa ATCC 27853. METHODS Culture conditions (AgNO3 concentration, pH, and incubation temperature and time) were optimized to achieve maximum AgNP production. The characterisation of AgNPs and their stability were evaluated by UV-visible spectrophotometry and scanning electron microscopy. FINDINGS The characteristic UV-visible absorbance peak was observed in the 420-430 nm range. Most of the particles were spherical in shape within a size range of 33-300 nm. The biosynthesized AgNPs exhibited higher stability than that exhibited by chemically synthesized AgNPs in the presence of electrolytes. The biosynthesized AgNPs exhibited antimicrobial activity against Escherichia coli, P. aeruginosa, Salmonella typhimurium, Staphylococcus aureus, methicillin-resistant S. aureus, Acinetobacter baumannii, and Candida albicans. MAIN CONCLUSION As compared to the tested Gram-negative bacteria, Gram-positive bacteria required higher contact time to achieve 100% reduction of colony forming units when treated with biosynthesized AgNPs produced using P. aeruginosa.

Comparison of duplex PCR and phenotypic analysis in differentiating Candida dubliniensis from Candida albicans from oral samples.

Candida dubliniensis shares a wide range of phenotypic characteristics with Candida albicans including a common trait called germ tube positivity. Hence, laboratory differentiation of these two species is cumbersome. Duplex PCR analyses for C. albicans and C. dubliniensis was performed directly on DNA extracted from a total of 122 germ tube positive isolates derived from 100 concentrated oral rinse samples from a random cohort of diabetics attending a clinic in Sri Lanka. These results were confirmed by DNA sequencing of internal transcribed spacer (ITS) region of rDNA of the yeasts. Performance efficacy of duplex PCR was then compared with phenotypic identification using a standard battery of phenotypic tests. Of the 122 germ tube positive isolates three were identified by duplex PCR as C. dubliniensis and the remainder as C. albicans. On the contrary, when the standard phenotypic tests, sugar assimilation and chlamydospore formation, were used to differentiate the two species 13 germ tube positive isolates were erroneously identified as C. dubliniensis. Duplex PCR was found to be rapid, sensitive and more specific than phenotypic identification methods in discriminating C. dubliniensis from C. albicans. This is also the first report on the oral carriage of C. dubliniensis in a Sri Lankan population.