Fungal and mycobacterial cultures should not be routinely obtained for diagnostic work-up of patients with suspected periprosthetic joint infections

Aims Fungal and mycobacterial periprosthetic joint infections (PJI) are rare events. Clinicians are wary of missing these diagnoses, often leading to the routine ordering of fungal and mycobacterial cultures on periprosthetic specimens. Our goal was to examine the utility of these cultures and explore a modern bacterial culture technique using bacterial blood culture bottles (BCBs) as an alternative. Methods We performed a retrospective review of patients diagnosed with hip or knee PJI between 1 January 2010 and 31 December 2019, at the Mayo Clinic in Rochester, Minnesota, USA. We included patients aged 18 years or older who had fungal, mycobacterial, or both cultures performed together with bacterial cultures. Cases with positive fungal or mycobacterial cultures were reviewed using the electronic medical record to classify the microbiological findings as representing true infection or not. Results There were 2,067 episodes of PJI diagnosed within the study period. A total of 3,629 fungal cultures and 2,923 mycobacterial cultures were performed, with at least one of these performed in 56% of episodes (n = 1,157). Test positivity rates of fungal and mycobacterial cultures were 5% (n = 179) and 1.2% (n = 34), respectively. After a comprehensive review, there were 40 true fungal and eight true mycobacterial PJIs. BCB were 90% sensitive in diagnosing true fungal PJI and 100% sensitive in detecting rapidly growing mycobacteria (RGM). Fungal stains were performed in 27 true fungal PJI but were only positive in four episodes (14.8% sensitivity). None of the mycobacterial stains was positive. Conclusion Routine fungal and mycobacterial stains and cultures should not be performed as they have little clinical utility in the diagnosis of PJI and are associated with significant costs. Candida species and RGM are readily recovered using BCB. More research is needed to predict rare non- Candida fungal and slowly growing mycobacterial PJI that warrant specialized cultures. Cite this article: Bone Joint J 2022;104-B(1):53–58.

Analysis of cutoff point estimation for determining seropositivity in the context of SARS-CoV-2 infections

In this work will apply mixture models based on distributions from the SMSN family to antibody data against four SARS-CoV-2 virus antigens. Furthermore, since the true infection status of individuals is known a priori, performance measures will be calculated for the methods proposed for cutoff point estimation such as sensitivity, specificity and accuracy. The results of a simulation study will also be presented.

277. Low Rates of Bacterial Co-infection in Hospitalized Patients with COVID-19

Background The rate of bacterial co-infection in inpatients with COVID-19 is unknown, however, patients who are hospitalized with COVID-19 often receive antibiotics for community-acquired bacterial pneumonia (CABP). Reducing unnecessary antibiotic usage in this population is important to prevent adverse effects and slow the development of antimicrobial resistance. Methods We performed a retrospective chart review on patients admitted to our health system between March and May 2020 with confirmed COVID-19 by nasopharyngeal PCR. We reviewed patients with positive cultures from urine, blood, sputum, and sterile sites. Positive cultures were reviewed to determine if they represented a true infection versus a contaminant or colonization. Patients with true infections were categorized as having a co-infection (CI) if the positive culture was collected within 48 hours of initial positive SARS-CoV-2 PCR test. Additional data was collected on patient demographics, types of infections, organisms grown, and antibiotic usage. Results 902 patients were admitted with positive SARS-CoV-2 tests during the study period. Of these, 47 patients (5.2%) had a bacterial CI. Some patients had more than one CI, with 53 total CIs identified. The median age of patients with CI was 66 years old (39 – 90). Tables 1 and 2 describe patient characteristics and infections. A subgroup analysis on types of bacteria was done on the 20 patients with a respiratory CI, who accounted for 2.2% of all COVID-positive patients admitted during the study period. In these infections, Staphylococcus aureus, Streptococcus species, and Haemophilus influenzae were the most common organisms, accounting for 60%, 15%, and 10% infections, respectively. Table 1. Patient Characteristics Table 2. Co-infections Conclusion The overall rate of CIs in patients admitted with COVID-19 was low. Some of these CIs may represent an “incidentally positive” COVID-19 test if a patient presented with one infection and had asymptomatic carriage of SARS-CoV-2 when community prevalence was high. Further analysis is needed to evaluate specific risk factors for co-infection. Disclosures Jason C. Gallagher, PharmD, FIDP, FCCP, FIDSA, BCPS, Astellas (Consultant, Speaker’s Bureau)Merck (Consultant, Grant/Research Support, Speaker’s Bureau)Qpex (Consultant)scPharmaceuticals (Consultant)Shionogi (Consultant) Jason C. Gallagher, PharmD, FIDP, FCCP, FIDSA, BCPS, Astellas (Individual(s) Involved: Self): Speakers' bureau; Merck (Individual(s) Involved: Self): Consultant, Grant/Research Support; Nabriva: Consultant; Qpex (Individual(s) Involved: Self): Consultant; Shionogi (Individual(s) Involved: Self): Consultant

296. Description of Super-infections in Hospitalized Patients with COVID-19

Background The rate of bacterial and fungal super-infections (SI) in inpatients with COVID-19 is unknown. In this study, we aimed to identify and describe patients that developed secondary infections while hospitalized with COVID-19. Methods We performed a retrospective chart review on patients admitted to our health system between March and May 2020 with confirmed COVID-19 by nasopharyngeal PCR. We reviewed patients with positive cultures from urine, blood, sputum, and sterile sites. Patients with positive cultures had cases reviewed to determine if they represented a true infection, defined by CDC criteria. SIs were defined as infections that occurred at least 48 hours or longer after the initial positive SARS-CoV-2 test. Additional data was collected on patient demographics, COVID-related therapies, types of infections, and outcomes. Results 902 patients were admitted with COVID-19 during our study period. Of these, 52 patients (5.8%) developed a total of 82 SIs. Tables 1 and 2 describe patient and infection characteristics. Patients identified as having a SI were admitted for a median of 30 days; 56% had mortality, and 39% of remaining patients were readmitted within 90 days. Table 1. Patient Characteristics Table 2. Super-infections Conclusion Overall, the rate of SIs in patients admitted with COVID-19 is low. These patients had a long length of stay, which may be either a cause of SI or an effect. Further analysis with matched COVID-positive control patients who do not develop SIs is needed to evaluate the risk of development of SIs in relation to presenting respiratory status, COVID-related therapies, and other patient-specific factors. Disclosures Jason C. Gallagher, PharmD, FIDP, FCCP, FIDSA, BCPS, Astellas (Consultant, Speaker’s Bureau)Merck (Consultant, Grant/Research Support, Speaker’s Bureau)Qpex (Consultant)scPharmaceuticals (Consultant)Shionogi (Consultant) Jason C. Gallagher, PharmD, FIDP, FCCP, FIDSA, BCPS, Astellas (Individual(s) Involved: Self): Speakers’ bureau; Merck (Individual(s) Involved: Self): Consultant, Grant/Research Support; Nabriva: Consultant; Qpex (Individual(s) Involved: Self): Consultant; Shionogi (Individual(s) Involved: Self): Consultant

Practical Approach to the Pathologic Diagnosis of Mixed Filamentous Fungal Infections in Burn Wounds: A Case Series

Introduction/Objective Opportunistic infections by fungi are a major source of morbidity and mortality in patients suffering from extensive burn wounds. Here we review a series of cases of infections by multiple fungi in burn wounds as diagnosed by histopathology and outline the key features for the pathologist to include in the report. Methods/Case Report Biopsies from patients with more than one fungal species identified in the laboratory in a concurrent culture or by PCR were included in this study. Three cases are presented with multiple fungi identified. Each case had yeast and at least one different hyaline mold species present on pathology; two cases additionally had mucormycetes present, with angioinvasion in one case. All organisms requiried microbiologic cultures and variably required molecular testing for full identification. Results (if a Case Study enter NA) N/A Conclusion Pathologists should be aware of the possibility of infection by multiple fungal species in burn wounds. Fungal morphology in tissue sections should allow for detection and distinction of mucormyctes and other hyaline molds. Histopathologic correlation with culture and/or PCR results is essential to distinguish potential contaminants from true infection.

Medicazione a base d’argento nella gestione dell’emergenza cutanea

Introduction: Exit-site (ES) and tunnel infections are the main infectious complication in peritoneal dialysis (PD); they also are risk factors for the development of peritonitis, for catheter removal and for dialysis drop-out. Up to now, besides the recommendations of the Guidelines there is no uniformity, nor on the classification, nor on the treatment strategies of the infected ES. Recent experiences are reported with alternative types of dressings that aim to reduce the incidence of ES infection and consequently of the subcutaneous tunnel. Methods: The Tuscan group conducted a retrospective observational study of 10 patients on PD who, showing signs of a suspected but not ascertained infection (negative microbiological culture), such as redness, edema, secretion, scab, had been medicated with silver-ions releasing Exit-Pad Ag. The aim was to evaluate and classify the evolution of ES lesions, in order to confirm the preventive efficacy of the silver-ions releasing dressing compared to the traditional ones. Results: After 4 weeks of treatment with Exit Pad Ag maintained in situ for 72 h, 6 patients no longer had any signs of inflammation. In 2 cases, several weeks of treatment were necessary to achieve a complete recovery, while in 2 other cases the signs of inflammation became negative in less time (2 weeks, 1 week). Conclusions: With the utilization of an alternative dressing such as Exit-Pad Ag on PD patients showing early signs of inflammation, the onset of a true infection can be prevented, with a progressive improvement of the ES.

Estimating SARS-CoV-2 infections from deaths, confirmed cases, tests, and random surveys

There are multiple sources of data giving information about the number of SARS-CoV-2 infections in the population, but all have major drawbacks, including biases and delayed reporting. For example, the number of confirmed cases largely underestimates the number of infections, and deaths lag infections substantially, while test positivity rates tend to greatly overestimate prevalence. Representative random prevalence surveys, the only putatively unbiased source, are sparse in time and space, and the results can come with big delays. Reliable estimates of population prevalence are necessary for understanding the spread of the virus and the effectiveness of mitigation strategies. We develop a simple Bayesian framework to estimate viral prevalence by combining several of the main available data sources. It is based on a discrete-time Susceptible–Infected–Removed (SIR) model with time-varying reproductive parameter. Our model includes likelihood components that incorporate data on deaths due to the virus, confirmed cases, and the number of tests administered on each day. We anchor our inference with data from random-sample testing surveys in Indiana and Ohio. We use the results from these two states to calibrate the model on positive test counts and proceed to estimate the infection fatality rate and the number of new infections on each day in each state in the United States. We estimate the extent to which reported COVID cases have underestimated true infection counts, which was large, especially in the first months of the pandemic. We explore the implications of our results for progress toward herd immunity.

Bounding Infection Prevalence by Bounding Selectivity and Accuracy of Tests: With Application to Early COVID-19

I propose novel partial identification bounds on infection prevalence from information on test rate and test yield. The approach utilizes user-specified bounds on (i) test accuracy and (ii) the extent to which tests are targeted, formalized as restriction on the effect of true infection status on the odds ratio of getting tested and thereby embeddable in logit specifications. The motivating application is to the COVID-19 pandemic but the strategy may also be useful elsewhere. Evaluated on data from the pandemic’s early stage, even the weakest of the novel bounds are reasonably informative. Notably, and in contrast to speculations that were widely reported at the time, they place the infection fatality rate for Italy well above the one of influenza by mid-April.