Source investigation of two outbreaks of skin and soft tissue infection by Mycobacterium abscessus subsp. abscessus in Venezuela

Practical Guidance for Clinical Microbiology Laboratories: Microbiologic diagnosis of implant-associated infections

SUMMARYImplant-associated infections (IAIs) pose serious threats to patients and can be associated with significant morbidity and mortality. These infections may be difficult to diagnose due, in part, to biofilm formation on device surfaces, and because even when microbes are found, their clinical significance may be unclear. Despite recent advances in laboratory testing, IAIs remain a diagnostic challenge. From a therapeutic standpoint, many IAIs currently require device removal and prolonged courses of antimicrobial therapy to effect a cure. Therefore, making an accurate diagnosis, defining both the presence of infection and the involved microorganisms, is paramount. The sensitivity of standard microbial culture for IAI diagnosis varies depending on the type of IAI, the specimen analyzed, and the culture technique(s) used. Although IAI-specific culture-based diagnostics have been described, the challenge of culture-negative IAIs remains. Given this, molecular assays, including both nucleic acid amplification tests and next-generation sequencing-based assays, have been used. In this review, an overview of these challenging infections is presented, as well as an approach to their diagnosis from a microbiologic perspective.

Complicated Surgical Site Infection with Mycobacterium Abscessus After Liposuction and Affections of Corticosteroids in the Treatment Regimen: Three Cases Report and a Systematic Review

INTRODUCTION

Mycobacterium abscessus infection after liposuction/fat grafting is a rare complication that is hard to diagnose and treat. Misdiagnosis could result in treatment failure and prolonged hospital stays. The paradoxical reaction is another complication that rarely occurs in non-HIV patients infected with nontuberculosis mycobacteria. This study reported 3 cases infected with M. abscessus complicated by the paradoxical reaction after liposuction and fat grafting. It highlighted characteristics giving clues of the paradoxical reaction and a successful strategy. Also, a systematic review was conducted to comprehensively provide varied aspects of M. abscessus infection after liposuction and/or fat grafting.

METHODS

Three cases were retrospectively included reporting data characteristics of patients, cosmetic procedures, and treatment strategy. PubMed, Scopus, Virtual Health Library (VHL), and Global Health Library (GHL) were searched to find and include cases with M. abscessus infection after liposuction and/or fat grafting based on defined selection criteria. Relevant data were extracted and summarized. The risk of bias in included studies was assessed using JBI critical appraisal checklists.

RESULTS

Twenty-four articles were included in the systematic review. Symptoms often developed approximately 1 month after the cosmetic surgery. Culture, AFB, and PCR were common methods of diagnosis of M. abscessus after liposuction and/or fat grafting. It took about 33 days on average from the presentation to isolate and detect the pathogens. Antibiotics based on susceptibility testing results along with surgical interventions were effective methods of treatment. Our three cases which were complicated by the paradox were addressed by adding methylprednisolone for 2 weeks to the macrolide-based therapy.

CONCLUSIONS

Awareness of this disease should be widely raised among physicians for early diagnosis and proper treatments. Cultures of specimens and AFB should be repeated many times before excluding the possibility of Mycobacterium spp. A paradoxical reaction should be suspected if the symptoms were worse after the antibiotic therapy based on susceptibility testing results and proper surgical interventions, especially if patients had taken corticosteroids before being admitted.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors   www.springer.com/00266 .

The Re-Identification of Previously Unidentifiable Clinical Non-Tuberculous Mycobacterial Isolates Shows Great Species Diversity and the Presence of Other Acid-Fast Genera

Non-tuberculous mycobacteria that cannot be identified at the species level represent a challenge for clinical laboratories, as proper species assignment is key to implementing successful treatments or epidemiological studies. We re-identified forty-eight isolates of Ziehl-Neelsen (ZN)-staining-positive "acid-fast bacilli" (AFB), which were isolated in a clinical laboratory and previously identified as Mycobacterium species but were unidentifiable at the species level with the hsp65 PCR restriction fragment length polymorphism analysis (PRA). As most isolates also could not be identified confidently via 16S, hsp65, or rpoB DNA sequencing and a nBLAST search analysis, we employed a phylogenetic method for their identification using the sequences of the 16S rDNA, which resulted in the identification of most AFB and a Mycobacterium species diversity not found before in our laboratory. Most were rare species with only a few clinical reports. Moreover, although selected with the ZN staining as AFB, not all isolates belonged to the genus Mycobacterium, and we report for the first time in Latin America the isolation of Nocardia puris, Tsukamurella pulmosis, and Gordonia sputi from sputum samples of symptomatic patients. We conclude that ZN staining does not differentiate between the genus Mycobacterium and other genera of AFB. Moreover, there is a need for a simple and more accurate tree-based identification method for mycobacterial species. For this purpose, and in development in our lab, is a web-based identification system using a phylogenetic analysis (including all AFB genera) based on 16S rDNA sequences (and in the future multigene datasets) and the closest relatives.

Atypical Mycobacterial Infection in Anophthalmic Sockets With Porous Orbital Implant Exposure

PURPOSE

To investigate the clinical features and risk factors of atypical mycobacterial infection in anophthalmic sockets with porous orbital implant exposure.

DESIGN

Case-control study.

METHODS

The medical records of all patients who had undergone surgical correction of porous orbital implant exposure were consecutively reviewed, and the patients were stratified as those with atypical mycobacterial infection (AM infection group) and others (non-AM group).

RESULTS

Five and 21 patients were included in the AM infection and non-AM groups, respectively. All patients of the AM infection group had a peg or motility coupling post (MCP) and showed implant exposure around it. Following up on implant exposure, 2 patients abruptly presented with severe conjunctival injection and new lesions such as erythematous nodules or eyelid masses. They underwent immediate orbital implant exchange and atypical mycobacterial infection was diagnosed. Three patients who were not suspected of having infection underwent surgery for orbital implant exposure. Results revealed erythematous eyelid nodule or recurrent exposure shortly after surgery and patients were diagnosed with atypical mycobacterial infection. In the non-AM group, 7 (33.3%) patients underwent insertion of a peg or MCP. Statistical analysis showed that the insertion of a peg or MCP was the only risk factor showing a significant difference between the 2 groups.

CONCLUSIONS

The most important underlying risk factor for atypical mycobacterial infection in the anophthalmic socket is thought to be peg- or MCP-related exposure of the porous orbital implant. Surgical removal of the infected orbital implant and long-term antibiotic medication are needed for treatment.

Deletion of a dehydratase important for intracellular growth and cording renders rough Mycobacterium abscessus avirulent

Mycobacterium abscessus (Mabs) is a rapidly growing Mycobacterium and an emerging pathogen in humans. Transitioning from a smooth (S) high-glycopeptidolipid (GPL) producer to a rough (R) low-GPL producer is associated with increased virulence in zebrafish, which involves the formation of massive serpentine cords, abscesses, and rapid larval death. Generating a cord-deficient Mabs mutant would allow us to address the contribution of cording in the physiopathological signs of the R variant. Herein, a deletion mutant of MAB_4780, encoding a dehydratase, distinct from the β-hydroxyacyl-ACP dehydratase HadABC complex, was constructed in the R morphotype. This mutant exhibited an alteration of the mycolic acid composition and a pronounced defect in cording. This correlated with an extremely attenuated phenotype not only in wild-type but also in immunocompromised zebrafish embryos lacking either macrophages or neutrophils. The abolition of granuloma formation in embryos infected with the dehydratase mutant was associated with a failure to replicate in macrophages, presumably due to limited inhibition of the phagolysosomal fusion. Overall, these results indicate that MAB_4780 is required for Mabs to successfully establish acute and lethal infections. Therefore, targeting MAB_4780 may represent an attractive antivirulence strategy to control Mabs infections, refractory to most standard chemotherapeutic interventions. The combination of a dehydratase assay with a high-resolution crystal structure of MAB_4780 opens the way to identify such specific inhibitors.