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SBA Answers
Published in Justin C. Konje, Complete Revision Guide for MRCOG Part 2, 2019
E 25%–35%The incidence of primary B19 infection during pregnancy has been estimated at 1%–5%, and the subsequent transplacental transmission is 24%–33%. The risk of developing hydrops following this infection is reportedly varied (0%–24%), but according to recent studies, the rate is probably quite low (1%–1.6%). However, in pregnant women with a confirmed primary infection, the overall risk of an abnormal outcome is approximately 5%–10%. Non-immune hydrops fetalis is rare (1 in 3000), and in 20%–50% of cases, the aetiology is unknown. Meta-analysis has shown that B19 accounts for 15%–20% of cases of nonimmune hydrops fetalis, with a mean interval between the onset of maternal infection and fetal symptoms of 6 weeks. The chance of an adverse fetal outcome after infection seems to be greatest between 11 and 23 weeks of gestation, which correlates with the hepatic period of haematopoietic activity. Cordocentesis allows precise assessment of fetal anaemia, which might then be corrected by intravenous transfusion of erythrocytes. Accordingly, in series of hydropic fetuses, the case fatality rate may be almost 50%, but transfusions have proven beneficial, lowering the mortality rate to 18%. (Heegaard ED and Brown KE. Clinical Microbiology Reviews. 2002; 15(3): 485–505 and Ismail KMK and Kilby MD. Human parvovirus B19 and pregnancy. The Obstetrician & Gynaecologist 2003; 5: 4–9)
Epidemiology and Assessment
Published in Keith Struthers, Clinical Microbiology, 2017
Following a patient's admission to hospital, the reason(s) for admission are coded and recorded. A summary of information for a whole year of adult patients admitted to a large hospital in the West Midlands shows the age and sex distribution (Figure 3.4). Not surprisingly, the majority are over the age of 60 years, reflecting the general effect of disease on the older population. When this information is grouped according to broad categories of disease, infection accounts for six out of the top 20. Lower respiratory tract infections (LRTI) are top in both sexes, while urinary tract infections (UTI) are second in females and fourth in males (Figure 3.5). This information is important in the appreciation of clinical microbiology, as it provides a background knowledge of local epidemiology, which should be used to consider which organism(s) is the culprit, what the diagnostic and treatment options are, and what infection control and public health alerts need to be acted upon from the outset. Some examples of signs and symptoms and more common organisms are summarized in Figure 3.6. This goes back to the theme introduced in Chapter 2.
Molecular Diagnostic Approaches in Infectious Disease
Published in Attila Lorincz, Nucleic Acid Testing for Human Disease, 2016
Leonard F. Peruski, Anne Harwood Peruski
Under normal circumstances, a clinical microbiology laboratory is faced with significant technical, clinical, and public health challenges. Not only must pathogens be identified, isolated, and characterized to permit the implementation of optimal therapies, but these tasks often must be accomplished under the multiple demands of limited time, organisms that are challenging to isolate and characterize, and the increasing need to define the functionality of a pathogen in terms of drug resistance, special virulence attributes, and epidemiological markers.
Direct inoculation method for identification and antimicrobial susceptibility testing using matrix-assisted laser desorption ionization-time of flight mass spectrometry and both the Vitek 2 and MicroScan Walkaway 96 Plus systems
Published in Baylor University Medical Center Proceedings, 2023
Maryann Brandt, Kimberly McCullor, Don Harris, Zachary Ratzlaff, Eric Thompson, Cory M. Pfeifer
Well-established methods requiring subculture prior to antimicrobial sensitivity testing (AST) take an average of 24 to 48 hours before results are available.1,2 The overall goal of clinical microbiology is to provide clinically relevant, dependably accurate results in the most cost-effective and timely manner.3 With the advent of molecular testing, clinical laboratories now have tools capable of providing rapid identification and specifying genotype-specific AST data from blood cultures more quickly. Literature has demonstrated the importance of rapid identification and susceptibility testing in patients with bacteremia.4 The aim of our study was to modify and combine the use of matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) and AST testing platforms to provide the most rapid methodology for identification and AST testing while remaining cost effective.5,6 Furthermore, we wanted to guide pharmacy interventions and provide actionable data for efficient antimicrobial stewardship.
Endophthalmitis: Microbiology and Organism Identification Using Current and Emerging Techniques
Published in Ocular Immunology and Inflammation, 2023
Christine L. Tan, Harsha Sheorey, Penelope J. Allen, Rosie C. H. Dawkins
Endophthalmitis is one of the few ophthalmological emergencies. It is an infection within the intraocular cavity that requires timely diagnosis and prompt initiation of treatment if useful vision is to be preserved. Organism identification is a crucial step, not only to demonstrate infective etiology but also to guide empiric therapy and subsequent tailoring of treatment to the nature and virulence of the organism at hand. However, rates of culture positivity by conventional microbiological techniques are ubiquitously variable,1–8 and clinicians sometimes encounter the challenges of managing patients with clinically suspected endophthalmitis and a culture-negative report.9–16 Local microbiological data should be used to guide empirical treatment in such cases. In light of this, newer molecular techniques are starting to be used for organism identification in infectious endophthalmitis.9,17–25 In this review, we outline the microbiological profile of endophthalmitis, discuss the current clinically used techniques for organism identification, and evaluate the utility of polymerase chain reaction (PCR) and next-generation sequencing (NGS) as emerging technologies for organism identification. Whilst they represent exciting future directions in clinical microbiology, we highlight the key practical challenges faced by Australian diagnostic laboratories for their use in a clinical setting.
In vitro activity of hyperthermia on swarming motility and antimicrobial susceptibility profiles of Proteus mirabilis isolates
Published in International Journal of Hyperthermia, 2021
Deniz Gazel, Hadiye Demirbakan, Mehmet Erinmez
In the field of clinical microbiology, an antimicrobial susceptibility test (antibiogram) is performed by exposing pathogen bacteria to increasing concentrations of an antibiotic, in vitro. Clinical microbiologists try to isolate and identify bacterial and fungal agents from patient samples using culturing methods. Afterwards, they perform antibiogram tests to determine the minimum inhibitory concentration (MIC) of an antimicrobial drug. If the MIC value is lower than a determined threshold, the isolate is accepted as susceptible/sensitive to that antimicrobial [2,21]. These threshold values (critical breakpoints) are determined by scientific committees for each bacterial/fungal species and antimicrobial drug according to the drug’s achievable concentrations. Nowadays, the Kirby-Bauer disk diffusion method is widely used in clinical microbiology laboratories since it has a strong correlation with reference antibiogram methods and is easy to perform [21]. Similarly, the thermobiogram method can be used to determine the minimum inhibitory temperature (MIT) of an isolate by incubating bacteria in various incubators with increasing temperature levels [2]. After one night of incubation, the lowest temperature value inhibiting the microbial growth can be determined as the MIT. The thermobiogram method can be modified and used to analyze bacterial swarming or synergistic effects of antibiotics at different temperatures.