Clinical and laboratory aspects of the diagnosis and management of cutaneous and subcutaneous infections caused by rapidly growing mycobacteria

Abstract

Rapidly growing mycobacteria (RGM) are known to cause pulmonary, extra-pulmonary, systemic/disseminated, and cutaneous and subcutaneous infections. The erroneous detection of RGM that is based solely on microscopy, solid and liquid cultures, Bactec systems, and species-specific polymerase chain reaction (PCR) may produce misleading results. Thus, inappropriate therapeutic measures may be used in dermatologic settings, leading to increased numbers of skin deformity cases or recurrent infections. Molecular tools such as the sequence analyses of 16S rRNA, rpoB and hsp65 or PCR restriction enzyme analyses, and the alternate gene sequencing of the superoxide dismutase (SOD) gene, dnaJ, the 16S-23S rRNA internal transcribed spacers (ITS), secA, recA1, dnaK, and the 32-kDa protein gene have shown promising results in the detection of RGM species. PCR restriction enzyme analyses (PRA) work better than conventional methods at identifying species that are closely related. Recently introduced molecular tools such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), pyrosequencing, DNA chip technology, and Beacon probes-combined PCR probes have shown comparable results in the detection of various species of RGM. Closely related RGM species (e.g., Mycobacterium fortuitum, M. chelonae, and M. abscessus) must be clearly differentiated using accurate molecular techniques because their therapeutic responses are species-specific. Hence, this paper reviews the following aspects of RGM: (i) its sources, predisposing factors, clinical manifestations, and concomitant fungal infections; (ii) the risks of misdiagnoses in the management of RGM infections in dermatological settings; (iii) the diagnoses and outcomes of treatment responses in common and uncommon infections in immunocompromised and immunocompetent patients; (iv) conventional versus current molecular methods for the detection of RGM; (v) the basic principles of a promising MALDI-TOF MS, sampling protocol for cutaneous or subcutaneous lesions and its potential for the precise differentiation of M. fortuitum, M. chelonae, and M. abscessus; and (vi) improvements in RGM infection management as described in the recent 2011 Clinical and Laboratory Standards Institute (CLSI) guidelines, including interpretation criteria of molecular methods and antimicrobial drug panels and their break points [minimum inhibitory concentrations (MICs)], which have been highlighted for the initiation of antimicrobial therapy.

Rapidly Growing Mycobacteria an often overlooked cause of Surgical Site Infections

“…Infections due to RGM are on the rise, the problem compounded by the fact that they are resistant to commonly used disinfectants (Collins et al, 1984;Duarte et al, 2009;Kothavade et al, 2013). These bacteria have predilection for causing infections of the dermis and subcutaneous area.…”

“…They are transmitted by aerosol, dust, contaminated tap water, water distribution pipes, sink faucets, medical devices and most importantly, erroneous sterilisation of laparoscopic instruments. M. fortuitum, M. chelonae and M. abscessus are responsible for majority of infections due to RGM (Lahiri et al, 2009;Kothavade et al, 2013), which may range from multiple lesions post-surgery to sternal wound infection and endocarditis following cardiac surgery (Phillips et al, 2001). Delayed wound healing, chronicity of infection and prolonged course of expensive antibiotics, makes RGM an important cause of serious nosocomial infections (Chauhan et al, 2007).…”

Cost Savings Realized by Implementation of Routine Microbiological Identification by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

“…In our laboratory, where sequencing is done weekly, this typically adds an extra week or more to the identification. Additionally, differentiation between two species of RGM, Mycobacterium abscessus and Mycobacterium chelonae, requires further molecular sequencing, in our case of the hsp65 region, which adds additional cost and time, as this methodology was also only performed once a week in our laboratory (11). Each molecular sequencing method is allotted 25 min of technologist time to complete.…”

Nontuberculous mycobacterial lung disease: ecology, microbiology, pathogenesis, and antibiotic resistance mechanisms

“…Previous studies revealed that MABC infections can be acquired in the community or in the hospital environment [75,76]. In the community environment, water supply systems are regarded as likely sources of MABC infection, and in the hospital environment, contamination of medical devices and water are considered to be potential sources of MABC infections [77]. Although MAC are the most common NTM species responsible for disease, the natural resistance of MABC to many antibiotics makes infections with the latter more difficult to treat [78][79][80][81].…”