- Volume 5, Issue 11, 2023

Background. The rapid and accurate diagnosis of tubercular lymphadenitis remains a challenging task today. The World Health Organization (WHO) endorsed the LoopAMP MTBC kit (TB-LAMP) as a replacement for sputum smear microscopy in the diagnosis of pulmonary tuberculosis (PTB). However, no prospective diagnostic accuracy study of TB-LAMP for tubercular lymphadenitis in adults has been performed yet. The current study evaluated the diagnostic performance of TB-LAMP in tubercular lymphadenitis (LNTB).

Methods. In a prospective observational study conducted at a tertiary care hospital in India, 90 subjects (age >18 years) suspected of LNTB were recruited consecutively and followed up for 6 months between January 2019 and December 2020. Samples were processed for microscopy, culture, GeneXpert, histopathology and TB-LAMP. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of TB-LAMP against the composite reference standard (CRS) and culture were determined.

Results. TB-LAMP showed a sensitivity of 83.78 % (95 % CI, 73.76–90.47) and a specificity of 81.25 % (95 % CI, 56.99–93.41), respectively, against the CRS. The PPV and NPV were 95.38 % (95 % CI, 87.29–98.42) and 52.00 % (95 % CI, 33.50–69.97), respectively. TB-LAMP showed a sensitivity of 88.89 % (95 % CI, 71.94–96.15) and a specificity of 36.17 % (95 % CI, 23.97–50.46), respectively, against culture. The PPV and NPV were 44.44 % (95 % CI, 32–57.62) and 85 % (95 % CI, 63.96–94.76), respectively.

Conclusion. TB-LAMP can be used instead of conventional microscopy for the diagnosis of TB in lymph node specimens at primary healthcare centres. It provides rapid and cost-effective diagnosis of LNTB in resource-limited settings due to good sensitivity and NPV.

Acinetobacter baumannii poses a significant challenge in healthcare settings across the globe, with isolates exhibiting carbapenem resistance at unprecedented rates. Here, we characterized a collection of A. baumannii isolates (n=64) recovered during the period September 2020 – November 2021 at a teaching hospital in Cochin, South India. The species identity of the isolates was confirmed with bla OXA-51-like PCR. The major carbapenemase determinants identified were bla OXA-23-like (45, 70.3 %) and bla NDM-1 (31, 48.4 %); co-occurrence of these genes was also observed in 27 (42.2 %) isolates. Other resistance genes identified included bla PER (34, 53.1 %), aac(6')-Ib-cr (42, 65.6 %), qnrS (25, 39.1 %), sul1 (32, 50 %), sul2 (33, 51.6 %), strA/strB (36, 56.3 %), aphA1-Iab (35, 54.7 %) and tetB (32, 50 %). Mapping PCR revealed the insertion element, ISAbaI upstream of bla OXA-23-like in all isolates possessing this gene. Concerning disinfectant resistance, all isolates carried the quaternary ammonium compound (QAC) resistance gene, qacEΔ1. Minimal inhibitory concentration (MIC) of benzalkonium chloride was high among the isolates and ranged from 8 to 128 µg ml−1. However, low MICs were observed for chlorhexidine and triclosan, with the majority (54, 80.6 %) of isolates showing an MIC of 2 µg ml−1 for chlorhexidine and all isolates exhibiting MICs of ≤0.125 µg ml−1 for triclosan. Further, all isolates were strong biofilm-producers, as assessed by the crystal violet-based microtitre plate assay. The ApaI-pulsed-field gel electrophoresis (PFGE) revealed the multi-clonal nature of the isolates, with 16 clusters and 16 unique pulsotypes identified at a cut-off of 80 %. In short, this study provides useful data on the molecular features of A. baumannii from this region, which could be helpful to assess the local epidemiology of this pathogen and also to devise infection control strategies.

The coronavirus disease 2019 (COVID-19) pandemic, caused by the SARS-CoV-2 virus, has rapidly evolved since late 2019, due to highly transmissible Omicron variants. While most Canadian paramedics have received COVID-19 vaccination, the optimal ongoing vaccination strategy is unclear. We investigated neutralizing antibody (NtAb) response against wild-type (WT) Wuhan Hu-1 and Omicron BA.4/5 lineages based on the number of doses and past SARS-CoV-2 infection, at 18 months post-initial vaccination (with a Wuhan Hu-1 platform mRNA vaccine [BNT162b2 or mRNA-1273]). Demographic information, previous COVID-19 vaccination, infection history, and blood samples were collected from paramedics 18 months post-initial mRNA COVID-19 vaccine dose. Outcome measures were ACE2 percent inhibition against Omicron BA.4/5 and WT antigens. We compared outcomes based on number of vaccine doses (two vs. three) and previous SARS-CoV-2 infection status, using the Mann-Whitney U test. Of 657 participants, the median age was 40 years (IQR 33–50) and 251 (42 %) were females. Overall, median percent inhibition to BA.4/5 and WT was 71.61 % (IQR 39.44–92.82) and 98.60 % (IQR 83.07–99.73), respectively. Those with a past SARS-CoV-2 infection had a higher median percent inhibition to BA.4/5 and WT, when compared to uninfected individuals overall and when stratified by two or three vaccine doses. When comparing two vs. three WT vaccine doses among SARS-CoV-2 negative participants, we did not detect a difference in BA.4/5 percent inhibition, but there was a difference in WT percent inhibition. Among those with previous SARS-CoV-2 infection(s), when comparing two vs. three WT vaccine doses, there was no observed difference between groups. These findings demonstrate that additional Whttps://www.covid19immunitytaskforce.ca/citf-databank/#accessing https://www.covid19immunitytaskforce.ca/citf-databank/#accessinguhan Hu-1 platform mRNA vaccines did not improve NtAb response to BA.4/5, but prior SARS-CoV-2 infection enhances NtAb response.

Background. We examined the 11 month longitudinal antibody decay among two-dose mRNA vaccinees, and identified factors associated with faster decay.

Methods. The study included samples from the COVID-19 Occupational Risk, Seroprevalence and Immunity among Paramedics (CORSIP) longitudinal observational study of paramedics in Canada. Participants were included if they had received two mRNA vaccines without prior SARS-CoV-2 infection and provided two blood samples post-vaccination. The outcomes of interest were quantitative SARS-CoV-2 antibody concentrations. We employed spaghetti and scatter plots (with kernel-weighted local polynomial smoothing curve) to describe the trend of the antibody decay over 11 months post-vaccine and fit a mixed effect exponential decay model to examine the loss of immunogenicity and factors associated with antibody waning over time.

Results. This analysis included 652 blood samples from 326 adult paramedics. Total anti-spike antibody levels peaked on the twenty-first day (antibody level 9042 U ml−1) after the second mRNA vaccine dose. Total anti-spike antibody levels declined thereafter, with a half-life of 94 [95 % CI: 70, 143] days, with levels plateauing at 295 days (antibody level 1021 U ml−1). Older age, vaccine dosing interval <35 days, and the BNT162b2 vaccine (compared to mRNA-1273 vaccine) were associated with faster antibody decay.

Conclusion. Antibody levels declined after the initial mRNA series with a half-life of 94 days, plateauing at 295 days. These findings may inform the timing of booster vaccine doses and identifying individuals with faster antibody decay.

Introduction. Chryseobacterium species are emerging bacteria capable of causing nosocomial infections in immunocompromised patients or patients with indwelling medical devices.

Hypothesis/ Gap statement. Information about the incidence of Chryseobacterium bacteremia from worldwide literature is limited.

Aim. We aimed to recognize the clinical characteristics, frequency of distribution of different Chryseobacterium species isolates, and their antimicrobial susceptibility profile from bloodstream infections.

Methods. We performed a retrospective cohort study to identify all isolates of Chryseobacterium species from bloodstream infection from January 2018 to November 2022 at a university hospital in North India.

Results. We identified 42 non-duplicate isolates of Chryseobacterium species from bloodstream infection in the duration of our study. Mean age of the patients was 48.35±16.63 years. Men (22/42, 52.2 %) were more commonly affected in comparison to women (20/42, 47.6 %) but the difference was not significant. The most common species identified was C. indologenes (40/42, 95.24 %) followed by C. gleum (2/42, 4.76 %). The co-morbidities commonly encountered in our study were chronic kidney disease (21/42, 50.0 %) followed by diabetes mellitus (12/42, 28.6 %) and chronic obstructive pulmonary disease (8/42, 19.05 %). All patients had intravenous access to medications or fluid management via a central or peripheral line and mechanical ventilation was observed in 39 (39/42, 92.86 %) patients. All the isolates were susceptible to minocycline (100 %), followed by doxycycline (97.6 %) and trimethoprim-sulfamethoxazole (95.2 %).

Conclusion. Chryseobacterium species are capable of causing pneumonia, bacteremia and urinary tract infection in immunocompromised patients. Early diagnosis and prompt treatment with appropriate antibiotics can prevent progression to septicemia.

The microbiological diagnosis of pleural effusion is based largely on classical microbiology methods, but these methods have a high rate of false negative results. Some previous studies have shown improved diagnostic performance for pathogens such as Streptococcus pneumoniae using molecular biology methods. We present the use of a multiplex PCR platform (BIOFIRE FILMARRAY Pneumonia Panel) for the aetiological diagnosis of pleural effusion in paediatric pneumonia. We present a case series of 17 pleural fluid samples that were processed by culture-based microbiology and molecular biology methods. Microbiological isolation was successful in four cases (25 %) through traditional culture methods. In contrast, the molecular biology panels allowed for detection in 16 out of 17 cases (94 %). The results from these panels led to a change in management for nine out of the 17 cases (52 %). This study found an increase in aetiological diagnosis in complicated pneumonia in children by using molecular biology methods, which led to a significant change in patient management.

The diagnosis of infective endophthalmitis is supported by microbiological work-up. Rapid work-up is critical to confirm clinical suspicion and appropriate antimicrobial therapy. We report the novel use of an automated liquid culture processing system (FAST system, Qvella, ON, Canada) in a vitreous fluid culture. A 59-year-old patient with post-operative endophthalmitis presented with acute right eye pain and blurred vision. Vitreous fluid collected for microbiology culture was of limited quantity and only inoculated to thioglycolate broth. The broth recovered beta-haemolytic, group G Streptococcus dysgalactiae susceptible to penicillin and vancomycin. Experimental application of the FAST system to purify the organism from broth culture yielded the same identification and susceptibility test results but 1 day sooner. Despite prompt treatment with appropriate antibiotics, including vancomycin and ceftazidime, disease progressed rapidly and required enucleation to achieve a stable therapeutic outcome. Use of automated processing of monomicrobial broth cultures has thus far focused on positive blood culture broths, but could potentially include other liquid-based cultures such as for sterile body fluids of critical nature.

Diagnosis of chronic Q fever is often difficult for clinicians, particularly in the presence of a second pathology. In addition to the chronic constitutional symptoms, the most common manifestations of chronic Q fever include infective endocarditis and endovascular infection. We describe a case of prosthetic valve infective endocarditis caused by both Streptococcus sanguinis and Coxiella burnetti on a background of a previous aortic graft and bioprosthetic aortic valve replacement 2 years earlier. The diagnosis of chronic Q fever infective endocarditis was delayed because the significance of the abnormal valve histology from the patient’s previous surgery was initially overlooked. It was only after the patient had relapsed on appropriate therapy for the S. sanguinis prosthetic valve endocarditis that a subsequent review of the operative valve histology, along with the patient’s epidemiological risk factors, led to consideration of an additional culture-negative cause for infective endocarditis. Histological examination of the valve tissue had shown exophytic fibrin vegetations and acute inflammation. Further clinical assessment revealed previous exposure to Q fever and C. burnetti DNA was detected via polymerase chain reaction on the valve tissue. Q fever infective endocarditis must be considered if valves are inflamed or have vegetations with a subsequent negative culture. It should also still be considered in the presence of an alternative bacteraemia if the patient has risk factors for exposure.