Nocardia

Unleashing the potential: type I CRISPR-Cas systems in actinomycetes for genome editing

Covering: up to the end of 2023Type I CRISPR-Cas systems are widely distributed, found in over 40% of bacteria and 80% of archaea. Among genome-sequenced actinomycetes (particularly Streptomyces spp.), 45.54% possess type I CRISPR-Cas systems. In comparison to widely used CRISPR systems like Cas9 or Cas12a, these endogenous CRISPR-Cas systems have significant advantages, including better compatibility, wide distribution, and ease of operation (since no exogenous Cas gene delivery is needed). Furthermore, type I CRISPR-Cas systems can simultaneously edit and regulate genes by adjusting the crRNA spacer length. Meanwhile, most actinomycetes are recalcitrant to genetic manipulation, hindering the discovery and engineering of natural products (NPs). The endogenous type I CRISPR-Cas systems in actinomycetes may offer a promising alternative to overcome these barriers. This review summarizes the challenges and recent advances in CRISPR-based genome engineering technologies for actinomycetes. It also presents and discusses how to establish and develop genome editing tools based on type I CRISPR-Cas systems in actinomycetes, with the aim of their future application in gene editing and the discovery of NPs in actinomycetes.

Yersinia enterocolitica and Photorhabdus asymbiotica β-lactamases BlaA are exported by the twin-arginine translocation pathway

In general, β-lactamases of medically important Gram-negative bacteria are Sec-dependently translocated into the periplasm. In contrast, β-lactamases of Mycobacteria spp. (BlaC, BlaS) and the Gram-negative environmental bacteria Stenotrophomonas maltophilia (L2) and Xanthomonas campestris (Bla(XCC-1)) have been reported to be secreted by the twin-arginine translocation (Tat) system. Yersinia enterocolitica carries 2 distinct β-lactamase genes (blaA and blaB) encoding BlaA(Ye) and the AmpC-like β-lactamase BlaB, respectively. By using the software PRED-TAT for prediction and discrimination of Sec from Tat signal peptides, we identified a functional Tat signal sequence for Yersinia BlaA(Ye). The Tat-dependent translocation of BlaA(Ye) could be clearly demonstrated by using a Y. enterocolitica tatC-mutant and cell fractionation. Moreover, we could demonstrate a unique unusual temperature-dependent activity profile of BlaA(Ye) ranging from 15 to 60 °C and a high 'melting temperature' (T(M)=44.3°) in comparison to the related Sec-dependent β-lactamase TEM-1 (20-50°C, T(M)=34.9 °C). Strikingly, the blaA gene of Y. enterocolitica is present in diverse environmental Yersinia spp. and a blaA homolog gene could be identified in the closely related Photorhabdus asymbiotica (BlaA(Pa); 69% identity to BlaA(Ye)). For BlaA(Pa) of P. asymbiotica, we could also demonstrate Tat-dependent secretion. These results suggest that Yersinia BlaA-related β-lactamases may be the prototype of a large Tat-dependent β-lactamase family, which originated from environmental bacteria.

Infectious eccrine hidradenitis caused by nocardia

Neutrophilic eccrine hidradenitis is a nonspecific clinical reaction pattern classified as a neutrophilic dermatosis that typically occurs in the setting of chemotherapy for hematologic malignant disease. Neutrophilic eccrine hidradenitis more rarely has been reported in association with infectious agents, including Serratia, Enterobacter, Staphylococcus, and HIV. We describe the first case of infectious eccrine hidradenitis occurring in a patient with cutaneous Nocardia infection.

Activity of antimicrobial drugs evaluated by agar dilution and radiometric methods against strains of Nocardia asteroides isolated in Italy from immunocompromised patients

Benzylpenicillin, amoxicillin, amoxicillin plus clavulanic acid, cephalothin, cephaloridine, cefotaxime, imipenem, erythromycin, clarithromycin, azithromycin, amikacin, ciprofloxacin and trimethoprim-sulfamethoxazole were tested in vitro by the agar dilution method against eleven strains of Nocardia asteroides isolated both from AIDS and other immunocompromised patients. Imipenem, amikacin and trimethoprim-sulfamethoxazole were shown to be the most active drugs with minimum inhibitory concentrations (MIC) values nearly always lower than concentrations achievable in blood. Ciprofloxacin, cephaloridine and cefotaxime were moderately active, while the remaining drugs were totally ineffective. When susceptibility was assessed by the radiometric method the MIC90 values were uniformly lower than those in the agar method, possibly due to lower inactivation of drugs during incubation. The two methods showed a good correlation only for imipenem, amikacin and ciprofloxacin. The results obtained by the radiometric method seem to indicate that, as for mycobacteria, this method may also give a more accurate evaluation of the antimicrobial susceptibility of Nocardiae.

Infectious granulomatous diseases of the head and neck

Infectious granulomatous diseases of the head and neck are very important entities that can mimic or hide malignant tumors and a wide variety of diseases. The frequency of these diseases is increasing with the wider use of immunosuppressive drugs and the increasing incidence of AIDS. The diagnosis is simple, and does not require sophisticated diagnostic procedures, but a high index of suspicion is necessary. Although other studies are helpful to suggest the diagnosis or define the extent of the disease, the microbiological and histopathological analyses are the most specific studies for the diagnosis. The therapy is usually combined: medical and surgical. The medical therapy involves treatment for a long period of time, usually between 3 and 6 months. The follow-up should be kept for at least 3 years. The tendency of some of these diseases to relapse makes the therapy discouraging, and some patients will need multiple therapies throughout their life. An accurate diagnosis and specific therapy for adequate amount of time is the best way to achieve a complete cure or at least a better chance for a good prognosis.

Nocardiosis in an immunocompromised patient--an unusual presentation

A case of disseminated nocardiosis in a 39-year-old immunosuppressed patient is described. This presented clinically as a septicaemia with meningitis, and the true diagnosis was delayed following an apparent initial response to broad-spectrum antibiotics. The need for increased awareness of unusual infections in immunosuppressed patients who may have had repeated and sometimes invasive diagnostic techniques is discussed.

The radiographic appearance of pulmonary nocardiosis associated with AIDS

Pulmonary nocardiosis is a well-described infection in immunocompromised patients; however, it is less well documented in patients with AIDS. The pulmonary manifestation in 21 HIV-positive patients who developed pulmonary infection with Nocardia asteroides is described. The radiographic picture included lobar or multilobar consolidation (52 percent [11/21]), solitary masses (24 percent [5/21]), reticulonodular infiltrates (33 percent [7/21]), and pleural effusion (33 percent [7/21]). Cavitation was common (62 percent [13/21]), and upper lobes were more commonly involved (71 percent [15/21]). Although the radiographic picture is variable, nocardiosis should be suspected in an HIV-positive patient who has subacute pulmonary disease with an unexplained lung mass or cavitary lesions.