Legionella pneumophila and SARS-COV-2 co-infection: the importance of laboratory diagnosis. Letter

Clinical Reasoning: A 47-Year-Old Man With an Upper Respiratory Infection, Acute Confusion, Dysarthria, and Ataxia

A patient presenting with acute confusion, dysarthria, and appendicular ataxia with gait instability warrants a broad differential including emergent consideration of acute ischemic or hemorrhagic stroke. Moreover, in acute to subacute presentations, a wide array of etiologies including infectious causes, toxins, or autoimmune conditions may be considered. This article features a 47-year-old man who presented acutely with confusion, severe dysarthria, left upper extremity dysmetria, and unsteady gait. In this case, these neurologic signs were preceded by symptoms of an upper respiratory infection. In addition, MRI brain without contrast demonstrated a small focus of hyperintensity on diffusion-weighted imaging in the splenium of the corpus callosum with apparent diffusion coefficient match. The article illustrates a diagnostic approach in evaluating a patient with this constellation of clinical and radiologic findings, as well as pertinent management considerations. A comprehensive overview of other potential causative factors of the imaging findings is described to augment the reader's differential diagnosis. Finally, a literature review pertaining to the revealed diagnosis highlights the epidemiologic relevance and important clinical pearls.

Use of Fourier-Transform Infrared Spectroscopy With IR Biotyper® System for Legionella pneumophila Serogroups Identification

Legionella spp. are Gram-negative bacteria that inhabit freshwater environments representing a serious risk for human health. Legionella pneumophila (Lp) is the species most frequently responsible for a severe pneumonia known as Legionnaires' disease. Lp consists of 15 serogroups (Sgs), usually identified by monoclonal or polyclonal antibodies. With regard to Lp serogrouping, it is well known that phenotyping methods do not have a sufficiently high discriminating power, while genotypic methods although very effective, are expensive and laborious. Recently, mass spectrometry and infrared spectroscopy have proved to be rapid and successful approaches for the microbial identification and typing. Different biomolecules (e.g., lipopolysaccharides) adsorb infrared radiation originating from a specific microbial fingerprint. The development of a classification system based on the intra-species identification features allows a rapid and reliable typing of strains for diagnostic and epidemiological purposes. The aim of the study was the evaluation of Fourier Transform Infrared Spectroscopy using the IR Biotyper® system (Bruker Daltonik, Germany) for the identification of Lp at the serogroup (Sg) level for diagnostic purposes as well as in outbreak events. A large dataset of Lp isolates (n = 133) and ATCC reference strains representing the 15 Lp serogroups were included. The discriminatory power of the instrument's classifier, was tested by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). All isolates were classified as follows: 12/133 (9.0%) as Lp Sg1 and 115/133 (86.5%) as Lp Sg 2-15 (including both ATCC and environmental Lp serogroup). Moreover, a mis-classification for 2/133 (1.5%) isolates of Lp Sg 2-15 that returned as Lp Sg1 was observed, and 4/133 (3.0%) isolates were not classified. An accuracy of 95.49% and an error rate of 4.51% were calculated. IR Biotyper® is able provide a quick and cost-effective reliable Lp classification with advantages compared with agglutination tests that show ambiguous and unspecific results. Further studies including a larger number of isolates could be useful to implement the classifier obtaining a robust and reliable tool for the routine Lp serogrouping. IR Biotyper® could be a powerful and easy-to-use tool to identify Lp Sgs, especially during cluster/outbreak investigations, to trace the source of the infection and promptly adopt preventive and control strategies.