Diagnostic performance of isothermal strand displacement amplification of Mycobacterium tuberculosis IS 6110 in tissue samples

AbstractBackgroundVisualized histopathological findings in tissue samples are not specific for tuberculosis while mycobacterial cultures from such specimens have low yields and long turn around times. A rapid, sensitive method is therefore needed for detection of Mycobacterium tuberculosis in paucibacillary tissue samples.MethodologyIn this paper, a total of 158 tissue specimens, including 42 culture-positives, were tested for the presence of Mycobacterium tuberculosis by strand displacement amplification of DNA targeting the region of the insertion element IS 6110 and detected by a chemiluminescence based commercial platform (BDProbeTec™ ET System). The amplification results were correlated to histopathology, microscopy and microbiological culture.ResultsThe strand displacement amplification based assay showed low overall sensitivity (31.5%) but high specificity (97.5%) which varied across various tissue types. Only 35.7% of culture-positive biopsies were positive by the molecular assay. Some discrepancy were attributed to suboptimal performance of the traditional methods.ConclusionsThe assay is useful to rule in the disease in common tissue specimens (lung, pleura and lymph node); but less so in other tissue types. The poor sensitivity in tissue specimens necessitates careful interpretation of data generated by the assay in conjunction with a clinical suspicion of tuberculosis for making decision regarding empirical treatment. The complexity of the disease pathology along with the low bacillary load and clumping tendency require selection of more sensitive methods or gene targets

Eleven-Year Surveillance of Methicillin-Resistant Staphylococcus aureus Infections at an Academic Health Centre

Introduction. Methicillin-resistant Staphylococcus aureus (MRSA) is an important human pathogen associated with nosocomial and community infections. There is a continual focus on the epidemiology of this public health threat owing to the increase in its spread and rapid development of resistance. Aim. We aimed to describe the clinical presentations of MRSA infections at an academic health centre by demonstrating the time trend of antibiotic resistance. Methodology. We retrospectively reviewed cases during an 11-year period (from January 2009 to December 2019) with positive cultures for MRSA from various clinical sites in King Fahad Hospital of the University, to understand their clinical and microbiological profiles. Screening and colonisation samples were excluded. Results. A total of 1338 MRSA isolates were identified, with an increasing trend from 5.2% to 14.5% during 2009–2019. Skin and soft tissue samples were the most common source (52.4%) of MRSA infections. Vancomycin activity remained stable against MRSA, and only one isolate showed resistance to linezolid (<1%). A significant reduction in susceptibility to clindamycin (p = 0.003), trimethoprim-sulfamethoxazole (p = 0.001), and rifampin (p <0.0001) was detected over the study period. Conclusion. MRSA infections still represent a significant burden on healthcare systems. Our data support the need for constant local and regional surveillance to devise relevant protocols to manage MRSA infections. Empirical therapy needs to consider the changing antimicrobial susceptibility trends among MRSA isolates

A Protocol for Diagnosis and Management of Cerebrospinal Shunt Infections and other Infectious Conditions in Neurosurgical Practice

Infections of the cerebrospinal shunts and other neurosurgical structures are not uncommon in the clinical practice. These infections are mostly clinical emergencies carrying negative prognostic impacts on the patients as well as consuming healthcare resources. The low pathogenicity nature of some implicated pathogens results in minimal physical signs that may complicate the diagnosis and mislead the practitioner. Furthermore, little good prospective data exists in the field of neurosurgical infections and most available evidence is derived from retrospective nonrandomized studies. This protocol is meant to utilize the available evidence-based best practice to provide a guide for diagnosing and managing common neurosurgical infections including those associated with cerebrospinal shunts. The effective management of these neurosurgical infections requires a good collaboration between the clinical team, clinical pharmacist and clinical microbiologist

Antimicrobial Resistance in Ventilator-Associated Pneumonia: Predictive Microbiology and Evidence-Based Therapy

Abstract Ventilator-associated pneumonia (VAP) is a serious intensive care unit (ICU)-related infection in mechanically ventilated patients that is frequent, as more than half of antibiotics prescriptions in ICU are due to VAP. Various risk factors and diagnostic criteria for VAP have been referred to in different settings. The estimated attributable mortality of VAP can go up to 50%, which is higher in cases of antimicrobial-resistant VAP. When the diagnosis of pneumonia in a mechanically ventilated patient is made, initiation of effective antimicrobial therapy must be prompt. Microbiological diagnosis of VAP is required to optimize timely therapy since effective early treatment is fundamental for better outcomes, with controversy continuing regarding optimal sampling and testing. Understanding the role of antimicrobial resistance in the context of VAP is crucial in the era of continuously evolving antimicrobial-resistant clones that represent an urgent threat to global health. This review is focused on the risk factors for antimicrobial resistance in adult VAP and its novel microbiological tools. It aims to summarize the current evidence-based knowledge about the mechanisms of resistance in VAP caused by multidrug-resistant bacteria in clinical settings with focus on Gram-negative pathogens. It highlights the evidence-based antimicrobial management and prevention of drug-resistant VAP. It also addresses emerging concepts related to predictive microbiology in VAP and sheds lights on VAP in the context of coronavirus disease 2019 (COVID-19)

Genetic Diversity of Imipenem-Resistant Acinetobacter baumannii Infections at an Intensive Care Unit

Introduction. Imipenem-resistant Acinetobacter baumannii (IRAB) represents a major clinical threat. Dissemination in critical care areas necessitates effective action measures including genotyping tools to study the clonality of these strains and trace their origin. The main aim of this study is to assess the genetic relatedness between IRAB isolates in our institution intensive care units (ICU) which are at a particular risk of outbreaks. Methods. Nonreplicate IRAB strains were serially collected over 3 years period (January 2016–December 2018) from patients admitted to the ICU. The isolates were phenotypically identified by a matrix-assisted laser desorption/ionization time-of-flight- (MALDI-TOF-) based system (VITEK MS), and their susceptibility was tested by the phenotypic-based VITEK 2 system. Molecular fingerprinting was performed by enterobacterial repetitive intergenic consensus (ERIC-PCR) followed by hierarchal clustering. The patterns were analysed by the software of BioNumerics package version 7.6.3 (Applied Maths, Belgium). Results. A total of eighty IRAB were isolated from 31 colonization and 59 infection sites in patients admitted to the ICU. Sixty-two samples were respiratory in origin (77.5%). The generated dendrogram revealed distinct patterns for majority (95%) of the strains. Meropenem maintained activity against 43.8% of the imipenem-resistant A. baumannii. Conclusion. Meropenem can be a therapeutic option for imipenem-resistant A. baumannii. The banding patterns propose that multiple IRAB strains are circulating in the intensive care units of the institution. Drivers for this diversity need to be evaluated including antimicrobial consumption

Antifungal Effect of Henna against Candida albicans Adhered to Acrylic Resin as a Possible Method for Prevention of Denture Stomatitis

Denture stomatitis is a very common disease affecting the oral mucosa of denture wearers. The aim of this study was to measure the antifungal effect of henna against Candida albicans adhered to acrylic resin as a possible method for prevention of denture stomatitis. One-hundred-eighty acrylic plates were prepared of heat-cured acrylic denture resin. The specimens were divided into six groups of 30 samples each. The first group was only polymer and monomer following the conventional manufacturer instruction for processing complete dentures. The other five groups were processed by adding different concentration of Yamani henna powder (Harazi) to the polymer in a concentration of henna: polymer 1%, 2.5%, 5%, 7.5% and 10%, respectively. Samples were incubated in artificial saliva rich with Candida albicans at 37 °C, and the effect of henna on Candida albicans was evaluated in two different methods: semi-quantitative slide count and a culture-based quantitative assay (quantitative). Variation in the number of live Candida was observed with the increase in the concentration of Yamani henna powder. It was observed that the variation in live Candida, between control group and group B (concentration of Yamani henna powder was 1%), was statistically significant with a p-value of 0.0001. Similarly, variations in live Candida were significant, when the concentration of powder was 7.5% or 10% in contrast with control group and p-values were 0.0001 and 0.001 respectively. Adding henna to acrylic resin denture could be effective in controlling Candida albicans proliferation on the denture surface; however, its effects on the physical properties of acrylic resin denture need further studies