Detection and Quantification of Nocardia crassostreae, an Emerging Pathogen, in Mytilus galloprovincialis in the Mediterranean Sea Using Droplet Digital PCR

Nocardia crassostreae is a novel pathogen responsible for infections in oysters (Crassostrea gigas) and mussels (Mytilus galloprovincialis). N. crassostreae is also responsible for nocardiosis both in immunocompetent and immunocompromised patients. We investigated N. crassostreae DNA in mussels grown in marine sites of the Mediterranean Sea in the Campania Region. We examined 185 mussel pooled samples by droplet digital PCR (ddPCR) and real-time quantitative PCR (qPCR), each pool composed of 10 mussels and 149 individual mussels. ddPCR detected N. crassostreae DNA in 48 mussel pooled samples and in 23 individual mussel samples. qPCR detected N. crassostreae DNA in six pooled samples and six individual mussel samples. The two molecular assays for the detection of N. crassostreae DNA showed significant differences both in the pooled and in individual samples. Our study demonstrated that ddPCR outperformed real-time qPCR for N. crassostreae DNA detection, thus confirming that ddPCR technology can identify the pathogens in many infectious diseases with high sensitivity and specificity. Furthermore, in individual mussels showing histological lesions due to N. crassostreae, the lowest copy number/microliter detected by ddPCR of this pathogen was 0.3, which suggests that this dose could be enough to cause infections of N. crassostreae in mussels.

Epidemiology of Nocardia Species at a Tertiary Hospital in Southern Taiwan, 2012 to 2020: MLSA Phylogeny and Antimicrobial Susceptibility

The identification and antimicrobial susceptibility of Nocardia spp. are essential for guiding antibiotic treatment. We investigated the species distribution and evaluated the antimicrobial susceptibility of Nocardia species collected in southern Taiwan from 2012 to 2020. A total of 77 Nocardia isolates were collected and identified to the species level using multi-locus sequence analysis (MLSA). The susceptibilities to 15 antibiotics for Nocardia isolates were determined by the broth microdilution method, and the MIC₅₀ and MIC₉₀ for each antibiotic against different species were analyzed. N. cyriacigeorgica was the leading isolate, accounting for 32.5% of all Nocardia isolates, and the prevalence of Nocardia isolates decreased in summer. All of the isolates were susceptible to trimethoprim/sulfamethoxazole, amikacin, and linezolid, whereas 90.9% were non-susceptible to cefepime and imipenem. The phylogenic tree by MLSA showed that the similarity between N. beijingensis and N. asiatica was as high as 99%, 73% between N. niigatensis and N. crassostreae, and 86% between N. cerradoensis and N. cyriacigeorgica. While trimethoprim/sulfamethoxazole, amikacin, and linezolid remained fully active against all of the Nocardia isolates tested, 90.9% of the isolates were non-susceptible to cefepime and imipenem.

Genotypic and phenotypic prevalence of Nocardia species in Iran: First systematic review and meta-analysis of data accumulated over years 1992-2021

Background

Nocardia species belong to the aerobic actinomycetes group of bacteria which are gram-positive and partially acid-fast Bacilli. These bacteria may sometimes be associated with nosocomial infections. Nocardia diseases are not required to be reported to public health authorities in Iran. Hence, the present study was designed to determine the prevalence of human Nocardia spp. in Iran by using a systematic review and meta-analysis according to the preferred reporting items for systematic reviews and meta-Analyses statement.

Methods

The data of the prevalence of Nocardia species were collected from databases such as Embase, PubMed/MEDLINE via Ovid, Web of Science, Scopus and Google Scholar as well as national Iranian databases, including SID, Magiran. Analyses were conducted by STATA 14.0.

Results

The meta-analyses showed that the proportion of Nocardia spp. in Iranian studies varied from 1.71(1.17, 2.24) to 0.46(0.09, 0.83). N. asteroides (21% [95% CI 1.17, 2.24]), N. cyriacigeorgica (17% [95% CI 0.99, 1.77]), N. facanica (10% [95% CI 0.75, 1.00]) were considered to be common causative agents.

Conclusions

Our study presents that despite the fact that Nocardia spp. are normally are saprophytic organisms, are currently accounts as emerging pathogens due to an increase in immunocompromised patients among Iranian populations. Considering our results, the establishment of advanced diagnostic facilities for the rapid detection of Nocardia infections are required for optimal therapeutic strategies of Nocardia spp. in Iran. Our findings could help the programmatic management of the disease within the context of Nocardia control programs.

Isolated Nocardiosis, an Unrecognized Primary Immunodeficiency?

Nocardiosis is an infectious disease caused by the gram-positive bacterium Nocardia spp. Although it is commonly accepted that exposure to Nocardia is almost universal, only a small fraction of exposed individuals develop the disease, while the vast majority remain healthy. Nocardiosis has been described as an "opportunistic" disease of immunocompromised patients, suggesting that exposure to the pathogen is necessary, but a host predisposition is also required. Interestingly, increasing numbers of nocardiosis cases in individuals without any detected risk factors, i.e., without overt immunodeficiency, are being reported. Furthermore, a growing body of evidence have shown that selective susceptibility to a specific pathogen can be caused by a primary immunodeficiency (PID). This raises the question of whether an undiagnosed PID may cause nocardiosis affecting otherwise healthy individuals. This review summarizes the specific clinical and microbiological characteristics of patients with isolated nocardiosis published during the past 30 years. Furthermore, it gives an overview of the known human immune mechanisms to fend off Nocardia spp. obtained from the study of PIDs and patients under immunomodulatory therapies.

An unusual case of Nocardia cyriacigeorgica presenting with spinal abscesses in a renal transplant recipient and a review of the literature

Nocardia species represent a well-recognized yet uncommon cause of opportunistic infections in humans. It most frequently presents as a pulmonary infection with or without central nervous system involvement. It is a very rare cause of spinal abscesses, with only 26 cases reported in the literature. Here we report a 49-year-old man with a history of renal transplantation who presented with low back pain and was diagnosed with epidural and paraspinal abscesses due to Nocardia cyriacigeorgica that was successfully treated with antimicrobial therapy alone. In addition to the case reported here, we also conducted a systematic review of the existing literature regarding spinal abscesses due to Nocardia species and examined the success of the various treatments utilized.

Pathogenic Nocardia cyriacigeorgica and Nocardia nova Evolve To Resist Trimethoprim-Sulfamethoxazole by both Expected and Unexpected Pathways

Nocardia spp. are Gram-positive opportunistic pathogens that affect largely immunocompromised patients, leading to serious pulmonary or systemic infections. Combination therapy using the folate biosynthesis pathway inhibitors trimethoprim (TMP) and sulfamethoxazole (SMX) is commonly used as an antimicrobial therapy. Not surprisingly, as antibiotic therapies for nocardiosis can extend for many months, resistance to TMP-SMX has emerged. Using experimental evolution, we surveyed the genetic basis of adaptation to TMP-SMX across 8 strains of Nocardia nova and 2 strains of Nocardia cyriacigeorgica By employing both continuous experimental evolution to provide longitudinal information on the order of changes and characterization of resistant endpoint isolates, we observe changes that are consistent with modifications of two enzymes of the folate biosynthesis pathway: dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) (FolP), with the mutations often being clustered near the active site of the enzymes. While changes to DHFR and DHPS might be expected, we also noted that mutations in a previously undescribed homolog of DHPS (DHPS2 or FolP2) that was annotated as being "nonfunctional" were also sufficient to generate TMP-SMX resistance, which serves as a cautionary tale for the use of automated annotation by investigators and for the future discovery of drugs against this genus. Additionally, folP2 overlapped glucosyl-3-phosphoglycerate synthase. Remarkably, an adaptive frameshift mutation within the overlapping region resulted in a new in-frame fusion to the downstream gene to produce a potentially new bifunctional enzyme. How a single potentially bifunctional DHPS2 enzyme might confer resistance is unclear. However, it highlights the unexpected ways in which adaptive evolution finds novel solutions for selection.

Aerobic Actinomycetes of Clinical Significance

The group of Gram-positive bacillary organisms broadly known as "aerobic actinomycetes" consists of heterogeneous and taxonomically divergent genera. They are found in a wide variety of natural and man-made environments but are rarely considered a part of the normal human flora, with infections normally originating from exogenous sources. An extensive number of genera have been described, but only a minority of these has been associated with human or veterinary health. The association with human disease is usually of an opportunistic nature, either through accidental means of inoculation or through involvement with immunocompromising conditions in the host. They cause a wide spectrum of diseases in humans, which may differ greatly between the genera and even between species, but which also may have a great amount of overlap. The occurrence of such infections is probably greater than appreciated, since many may go unrecognized. Etiologic prevalence of specific genera and species varies geographically within the United States and worldwide. Traditional phenotypic identification methods for separation of the many genera and species of aerobic actinomycetes have found great difficulties. Recent use of chemotaxonomic analyses and emerging technologies such as molecular analysis of nucleic acids, and more recently proteomics for identification to the genus/species level, has provided a far more robust technique to understand the organisms' relatedness, distribution, epidemiology, and pathogenicity in humans.

Nocardia mikamiia Novel Species Causing Disseminated Nocardiosis: A Literature Review of Disseminated Nocardiosis

Nocardiais an uncommon Gram-positive organism. It typically appears as delicate filamentous Gram-positive branching rods. In the United States it was estimated to be approximately 500 to 1000 new cases per year. The organism causes disease in immunocompromised individuals with pulmonary infection representing the most common site of infection.Nocardia mikamiihas been a recently isolated pathogen and not many cases of disseminated infection with this organism has been reported in the literature; we present a case of disseminated nocardiosis (mikamii sp.) in an immunocompromised patient. We also present a literature review on nocardiosis.

Infections associated with body modification

Although exact statistics are lacking, body modifications for cosmetic purposes are performed in many countries. The commonest forms include tattooing, body piercing, and breast and facial augmentation using implants or injectable fillers. Liposuction and, to a lesser extent, mesotherapy are also practiced in many countries. Infective complications of these procedures include local infections, transmission of bloodborne pathogens (viral hepatitis and human immunodeficiency virus), and distant infections such as infective endocarditis. Presence of foreign bodies, long healing time of piercing wounds, and poor compliance with infection control practices of some practitioners all predispose the recipients to infections. Apart from the endogenous microbial flora of the skin and mucosae, atypical mycobacteria, especially the rapid growers, have emerged as some of the most important pathogens in such settings. Outbreaks of infection are commonly reported. We hereby review the current knowledge of the topic with specific focus on infections associated with tattooing, body piercing, breast augmentation, mesotherapy, liposuction, and tissue filler injections. Greater awareness among consumers and health-care professionals, as well as more stringent regulations by the health authorities, is essential to minimize the health risks arising from these procedures.