In vitro activity of ACH-702, a new isothiazoloquinolone, against Nocardia brasiliensis compared with econazole and the carbapenems imipenem and meropenem alone or in combination with clavulanic acid

Pedal Fungal Mass in the Midwest

Mycetoma cases are predominantly found in tropical regions and are a rare finding in the United States. These masses that are fungal or bacterial in origin can result in significant destruction of soft tissue and bone. We present a case of a patient who emigrated from Mexico to Indianapolis. He presented with a soft-tissue mass that was excised and ultimately found to be a eumycetoma of the hallux of his left foot. Successful treatment included surgical resection in combination with postoperative terbinafine, which was pulse dosed to decrease its impact on hepatic function.

Mycetoma medical therapy

Medical treatment of mycetoma depends on its fungal or bacterial etiology. Clinically, these entities share similar features that can confuse diagnosis, causing a lack of therapeutic response due to inappropriate treatment. This review evaluates the response to available antimicrobial agents in actinomycetoma and the current status of antifungal drugs for treatment of eumycetoma.

Complete genome sequence analysis of Nocardia brasiliensis HUJEG-1 reveals a saprobic lifestyle and the genes needed for human pathogenesis

Nocardia brasiliensis is an important etiologic agent of mycetoma. These bacteria live as a saprobe in soil or organic material and enter the tissue via minor trauma. Mycetoma is characterized by tumefaction and the production of fistula and abscesses, with no spontaneous cure. By using mass sequencing, we determined the complete genomic nucleotide sequence of the bacteria. According to our data, the genome is a circular chromosome 9,436,348-bp long with 68% G+C content that encodes 8,414 proteins. We observed orthologs for virulence factors, a higher number of genes involved in lipid biosynthesis and catabolism, and gene clusters for the synthesis of bioactive compounds, such as antibiotics, terpenes, and polyketides. An in silico analysis of the sequence supports the conclusion that the bacteria acquired diverse genes by horizontal transfer from other soil bacteria, even from eukaryotic organisms. The genome composition reflects the evolution of bacteria via the acquisition of a large amount of DNA, which allows it to survive in new ecological niches, including humans.

Complete genome sequence of Nocardia brasiliensis HUJEG-1

In Mexico, actinomycetoma is mainly caused by Nocardia brasiliensis, which is a soil inhabitant actinobacterium. Here, we report for the first time the draft genome of a strain isolated from a human case that has largely been found in in vitro and experimental models of actinomycetoma, N. brasiliensis HUJEG-1.

Carbapenems: past, present, and future

In this review, we summarize the current "state of the art" of carbapenem antibiotics and their role in our antimicrobial armamentarium. Among the β-lactams currently available, carbapenems are unique because they are relatively resistant to hydrolysis by most β-lactamases, in some cases act as "slow substrates" or inhibitors of β-lactamases, and still target penicillin binding proteins. This "value-added feature" of inhibiting β-lactamases serves as a major rationale for expansion of this class of β-lactams. We describe the initial discovery and development of the carbapenem family of β-lactams. Of the early carbapenems evaluated, thienamycin demonstrated the greatest antimicrobial activity and became the parent compound for all subsequent carbapenems. To date, more than 80 compounds with mostly improved antimicrobial properties, compared to those of thienamycin, are described in the literature. We also highlight important features of the carbapenems that are presently in clinical use: imipenem-cilastatin, meropenem, ertapenem, doripenem, panipenem-betamipron, and biapenem. In closing, we emphasize some major challenges and urge the medicinal chemist to continue development of these versatile and potent compounds, as they have served us well for more than 3 decades.

Actinomycetoma of the scalp after a car accident

BACKGROUND

Actinomycetoma is the most frequent type of mycetoma in Mexico. Localization on the scalp is very rare. Because of this topography and potential spread to the brain, the present case became a diagnostic and therapeutic challenge.

MATERIALS AND METHODS

We report the case of a 44-year-old woman with a 6 × 5 cm red, friable, granulomatous, vascular neoformation on the scalp and eye diagnosed as Nocardia brasiliensis actinomycetoma.

RESULTS

A combination of amikacin and oral trimethoprim-sulfamethoxazole (SXT) was successfully administered with an excellent outcome and no side effects.

CONCLUSIONS

This is a rare presentation of mycetoma of the scalp that was cured in 12 weeks with a combination of amikacin and SXT.

Synthesis and evaluation of 1-cyclopropyl-2-thioalkyl-8-methoxy fluoroquinolones

Novel fluoroquinolone derivatives substituted with a 2-thioalkyl moiety, with and without a concomitant 3-carboxylate group, were synthesized to evaluate the effect of C-2 thioalkyl substituents on gyrase binding and inhibition. The presence of a 2-thioalkyl group universally decreased activity as compared to parent fluoroquinolones. However, with derivatives of moxifloxacin the presence of either a 2-thioalkyl group or a 3-carboxylate moiety increased activity over the 2,3-unsubstituted derivative. Energy minimization of structures provides an explanation for relative activities of fluoroquinolones having a C-2 thio moiety.

In vitro and in vivo profiles of ACH-702, an isothiazoloquinolone, against bacterial pathogens

ACH-702, a novel isothiazoloquinolone (ITQ), was assessed for antibacterial activity against a panel of Gram-positive and Gram-negative clinical isolates and found to possess broad-spectrum activity, especially against antibiotic-resistant Gram-positive strains, including methicillin-resistant Staphylococcus aureus (MRSA). For Gram-negative bacteria, ACH-702 showed exceptional potency against Haemophilus influenzae, Moraxella catarrhalis, and a Neisseria sp. but was less active against members of the Enterobacteriaceae. Good antibacterial activity was also evident against several anaerobes as well as Legionella pneumophila and Mycoplasma pneumoniae. Excellent bactericidal activity was observed for ACH-702 against several bacterial pathogens in time-kill assays, and postantibiotic effects (PAEs) of >1 h were evident with both laboratory and clinical strains of staphylococci at 10 × MIC and similar in most cases to those observed for moxifloxacin at the same MIC multiple. In vivo efficacy was demonstrated against S. aureus with murine sepsis and thigh infection models, with decreases in the number of CFU/thigh equal to or greater than those observed after vancomycin treatment. Macromolecular synthesis assays showed specific dose-dependent inhibition of DNA replication in staphylococci, and biochemical analyses indicated potent dual inhibition of two essential DNA replication enzymes: DNA gyrase and topoisomerase IV. Additional biological data in support of an effective dual targeting mechanism of action include the following: low MIC values (≤0.25 μg/ml) against staphylococcal strains with single mutations in both gyrA and grlA (parC), retention of good antibacterial activity (MICs of ≤0.5 μg/ml) against staphylococcal strains with two mutations in both gyrA and grlA, and low frequencies for the selection of higher-level resistance (<10⁻¹⁰). These promising initial data support further study of isothiazoloquinolones as potential clinical candidates.

Susceptibility of 186 Nocardia sp. isolates to 20 antimicrobial agents

This study determined the antimicrobial susceptibilities of 186 clinical isolates of Nocardia spp. isolated in Gipuzkoa, northern Spain, between 1998 and 2009. Most isolates were recovered from respiratory samples, Nocardia nova, N. farcinica, N. cyriacigeorgica, N. abscessus, and N. carnea being the species most frequently isolated. Linezolid and amikacin were the only two antimicrobials to which all isolates were susceptible. The majority of N. flavorosea, N. carnea, and N. farcinica isolates were trimethoprim-sulfamethoxazole resistant.