Acyl-sulfamates target the essential glycerol-phosphate acyltransferase (PlsY) in Gram-positive bacteria.

PlsY is the essential first step in membrane phospholipid synthesis of Gram-positive pathogens. PlsY catalyzes the transfer of the fatty acid from acyl-phosphate to the 1-position of glycerol-3-phosphate to form the first intermediate in membrane biogenesis. A series of non-metabolizable, acyl-sulfamate analogs of the acyl-phosphate PlsY substrate were prepared and evaluated as inhibitors of Staphylococcus aureus PlsY and for their Gram-positive antibacterial activities. From this series phenyl (8-phenyloctanoyl) sulfamate had the best overall profile, selectively inhibiting S. aureus phospholipid biosynthesis and causing the accumulation of both long-chain fatty acids and acyl-acyl carrier protein intermediates demonstrating that PlsY was the primary cellular target. Bacillus anthracis was unique in being more potently inhibited by long chain acyl-sulfamates than other bacterial species. However, it is shown that Bacillus anthracis PlsY is not more sensitive to the acyl-sulfamates than S. aureus PlsY. Metabolic profiling showed that B. anthracis growth inhibition by the acyl-sulfamates was not specific for lipid synthesis illustrating that the amphipathic acyl-sulfamates can also have off-target effects in Gram-positive bacteria. Nonetheless, this study further advances PlsY as a druggable target for the development of novel antibacterial therapeutics, through the discovery and validation of the probe compound phenyl (8-phenyloctanoyl) sulfamate as a S. aureus PlsY inhibitor.

Two-year study evaluating the potential loss of methicillin resistance in a methicillin-resistant Staphylococcus aureus culture collection.

A reported loss of mecA prompted us to monitor 360 cryostocked methicillin-resistant Staphylococcus aureus strains for stability. Concurrently, 14 well-characterized strains were stored in a Microbank preservation system and subjected to multiple freeze-thaw events. There were no significant declines in the methicillin-resistant populations with either method over a two-year period.

Fatal necrotizing pneumonia due to a Panton-Valentine leukocidin positive community-associated methicillin-sensitive Staphylococcus aureus and Influenza co-infection: a case report.

Recent studies have described a number of fatalities due to methicillin-resistant Staphylococcus aureus (MRSA) and influenza virus co-infection. MRSA isolates provide a challenge to caregivers due to inherent wide range antibiotic resistance. Many facilities have instituted screening methods, based on the presence of antibiotic resistance genes, to identify MRSA positive patients upon admission. However, the resistance profile of the pathogen does not necessarily determine the severity of disease caused by that organism. We describe a fatal case of necrotizing pneumonia in a patient co-infected with Influenza B and a community-associated, PVL-positive methicillin-susceptible Staphylococcus aureus (MSSA).

How multidrug resistance in typhoid fever affects treatment options.

Salmonella enterica serotype Typhi (S. Typhi) is an enteric pathogen that causes typhoid fever. The infection can be severe, with significant morbidity and mortality, requiring antimicrobial therapy. Cases of S. Typhi infection in the United States and other developed countries are often associated with travel to endemic regions. The empirical use of first-line drugs for therapy, including ampicillin, chloramphenicol, and trimethoprim/sulfamethoxazole, has resulted in transmissible multidrug resistance. With the global increase in multidrug-resistant S. Typhi, use of ciprofloxacin, with excellent oral absorption, few side effects, and cost-effectiveness, has become popular for treatment. However, decreased ciprofloxacin susceptibility due to point mutations in the S. Typhi genes gyrA and/or parC has caused treatment failures, necessitating alternative therapeutic options. S. Typhi is typically genetically homogenous, with phylogenetic and epidemiological studies showing that identical clones and diverse S. Typhi types often coexist in the same geographic region. Studies investigating point mutations have demonstrated that selective pressure from empirical use of first-line drugs and fluoroquinolones has led to the global emergence of haplotype H-58. Antibiotic resistance is subject to high selective pressure in S. Typhi and thus demands careful use of antimicrobials.

Bacillus Strains Most Closely Related to Bacillus nealsonii Are Not Effectively Circumscribed within the Taxonomic Species Definition.

Bacillus strains with >99.7% 16S rRNA gene sequence similarity were characterized with DNA:DNA hybridization, cellular fatty acid (CFA) analysis, and testing of 100 phenotypic traits. When paired with the most closely related type strain, percent DNA:DNA similarities (% S) for six Bacillus strains were all far below the recommended 70% threshold value for species circumscription with Bacillus nealsonii. An apparent genomic group of four Bacillus strain pairings with 94%-70% S was contradicted by the failure of the strains to cluster in CFA- and phenotype-based dendrograms as well as by their differentiation with 9-13 species level discriminators such as nitrate reduction, temperature range, and acid production from carbohydrates. The novel Bacillus strains were monophyletic and very closely related based on 16S rRNA gene sequence. Coherent genomic groups were not however supported by similarly organized phenotypic clusters. Therefore, the strains were not effectively circumscribed within the taxonomic species definition.

Improvement of a selective media for the isolation of B. anthracis from soils.

To prove linkage between an environmental sample and an anthrax case, there must be isolates obtained from both that can be compared. Although Bacillus anthracis is easily isolated from powder samples, isolating it from soil is difficult because of the high bacterial count in it. Formulations of PLET were prepared, inoculated with B. anthracis, B. cereus and B. thuringiensis and examined for growth. Two hundred eighty-three isolates including 23 B. anthracis were placed onto one formulation while MICs against trimethoprim-sulfamethoxazole were determined. The media supported B. anthracis growth at 30 degrees C and inhibited almost all other bacterial growth, including closely-related species. Sensitivity for B. anthracis and selectivity against other Bacillus and against non-Bacillus were 96.8%, 100% and 97.2% respectively. Isolates that grew had MICs >4 and >76 microg mL(-1) against trimethoprim and sulfamethoxazole, respectively. Soils spiked with 10(2)B. anthracis spores and suspended in PLET broth yielded a 6-7 log(10) increase in B. anthracis. Other growth was inhibited. PLET supplemented with sulfamethoxazole (38 microg mL(-1)), trimethoprim (2 microg mL(-1)), polymyxin B (15,000 U L(-1)), and lysozyme (150,000 U L(-1)) can successfully select for B. anthracis and will facilitate agricultural, environmental and forensic investigations of B. anthracis isolates.

Novel acyl phosphate mimics that target PlsY, an essential acyltransferase in gram-positive bacteria.

PlsY is a recently discovered acyltransferase that executes an essential step in membrane phospholipid biosynthesis in Gram- positive bacteria. By using a bioisosteric replacement approach to generate substrate-based inhibitors of PlsY as potential novel antibacterial agents, a series of stabilized acyl phosphate mimetics, including acyl phosphonates, acyl alpha,alpha-difluoromethyl phosphonates, acyl phosphoramides, reverse amide phosphonates, acyl sulfamates, and acyl sulfamides were designed and synthesized. Several acyl phosphonates, phosphoramides, and sulfamates were identified as inhibitors of PlsY from Streptococcus pneumoniae and Bacillus anthracis. As anticipated, these inhibitors were competitive inhibitors with respect to the acyl phosphate substrate. Antimicrobial testing showed the inhibitors to have generally weak activity against Gram-positive bacteria with the exception of some acyl phosphonates, reverse amide phosphonates, and acyl sulfamates, which had potent activity against multiple strains of B. anthracis.

Susceptibility of Bacillus anthracis, Bacillus cereus, Bacillus mycoides, Bacillus pseudomycoides and Bacillus thuringiensis to 24 antimicrobials using Sensititre automated microbroth dilution and Etest agar gradient diffusion methods.

OBJECTIVES: To examine susceptibilities of Bacillus anthracis and related species to 24 antimicrobials using and concurrently comparing two methods. METHODS: Twenty-four antimicrobials were tested against 95 isolates of the Bacillus cereus group including 18 B. anthracis, 42 B. cereus, 5 Bacillus mycoides, 5 Bacillus mycoides/pseudomycoides, 6 Bacillus pseudomycoides and 19 Bacillus thuringiensis to determine their MICs, MIC ranges, MIC50s and MIC90s with Etest and Sensititre at 30 and 35 degrees C for 18, 24 and 48 h. RESULTS: Both methods yielded near-identical results at both temperatures for all antimicrobials except trimethoprim/sulfamethoxazole. Resistance to trimethoprim/sulfamethoxazole in 97% (92/95) was not always evident until tests were incubated for 48 h at 30 degrees C. All B. anthracis isolates were susceptible to 22 antimicrobials and resistant to trimethoprim/sulfamethoxazole while three isolates were erythromycin-intermediate. Whereas the B. thuringiensis were resistant to the beta-lactams, two B. cereus, one B. mycoides, five B. pseudomycoides and two B. mycoides/pseudomycoides were susceptible. Three B. cereus were solely clindamycin-resistant. Of the seven erythromycin-intermediate or -resistant B. cereus, three were resistant to clindamycin and one was resistant to clarithromycin and clindamycin. One B. mycoides was intermediately resistant to quinupristin/dalfopristin and meropenem and one was clindamycin-resistant. All B. pseudomycoides were clindamycin-resistant with one quinupristin/dalfopristin-resistant. Two B. mycoides/pseudomycoides were intermediately resistant to quinupristin/dalfopristin and clindamycin and a third was intermediately resistant to clindamycin alone. All isolates were susceptible to chloramphenicol, ciprofloxacin, gatifloxacin, gentamicin, levofloxacin, linezolid, moxifloxacin, rifampicin, streptomycin, tetracycline, tigecycline and vancomycin. CONCLUSIONS: This paper expands the list of therapeutic or prophylactic antimicrobials potentially effective against B. cereus group isolates using two testing methods that produced comparable results.

Bacillus acidiceler sp. nov., isolated from a forensic specimen, containing Bacillus anthracis pX02 genes.

Research at the Center for Biological Defense identified plasmid-borne forms of Bacillus anthracis pXO2 genes in a Gram-positive, endospore-forming rod, isolated from a forensic specimen considered a credible threat of harbouring anthrax. Conventional, commercial and molecular-based methods indicated that the isolate (CBD 119(T)) was not B. anthracis and considered not to be a member of the Bacillus cereus group. Based on the 16S rRNA gene sequence similarities, strain CBD 119(T) was most closely related to Bacillus luciferensis LMG 18422(T) (99.3 %). Phenotyping and fatty acid methyl ester analysis of the isolate were conducted alongside B. luciferensis JCM 12212(T). The major cellular fatty acids (anteiso-C(15 : 0), iso-C(15 : 0), and >7 iso or anteiso forms) supported inclusion of the isolate in the genus Bacillus. Strain CBD 119(T) was inconsistent with B. luciferensis JCM 12212(T) for 18 of 96 traits evaluated including motility, degree of endospore-driven swelling and pH optimum; the two were linked by fatty acid methyl ester analysis as separate but closely related species. DNA-DNA relatedness between strain CBD 119(T) and B. luciferensis JCM 12212(T) resulted in less than 20 % hybridization. The results of biochemical and physiological characterization, chemotaxonomic analysis and DNA-DNA hybridization differentiated strain CBD 119(T) both phenotypically and genotypically from the only species with validly published name with greater than 97 % 16S rRNA gene sequence similarity. The isolate has an accelerated doubling time when grown in aerated broth at pH 5.9 relative to that at pH 7.1. Therefore, it is proposed that strain CBD 119(T) represents a novel species, Bacillus acidiceler sp. nov. The type strain is strain CBD 119(T) (=NRRL B-41736(T)=DSM 18954(T)).

Bacillus anthracis virulent plasmid pX02 genes found in large plasmids of two other Bacillus species.

In order to cause the disease anthrax, Bacillus anthracis requires two plasmids, pX01 and pX02, which carry toxin and capsule genes, respectively, that are used as genetic targets in the laboratory detection of the bacterium. Clinical, forensic, and environmental samples that test positive by PCR protocols established by the Centers for Disease Control and Prevention for B. anthracis are considered to be potentially B. anthracis until confirmed by culture and a secondary battery of tests. We report the presence of 10 genes (acpA, capA, capB, capC, capR, capD, IS1627, ORF 48, ORF 61, and repA) and the sequence for the capsule promoter normally found on pX02 in Bacillus circulans and a Bacillus species closely related to Bacillus luciferensis. Tests revealed these sequences to be present on a large plasmid in each isolate. The 11 sequences consistently matched to B. anthracis plasmid pX02, GenBank accession numbers AF188935.1, AE011191.1, and AE017335.3. The percent nucleotide identities for capD and the capsule promoter were 99.9% and 99.7%, respectively, and for the remaining nine genes, the nucleotide identity was 100% for both isolates. The presence of these genes, which are usually associated with the pX02 plasmid, in two soil Bacillus species unrelated to B. anthracis alerts us to the necessity of identifying additional sequences that will signal the presence of B. anthracis in clinical, forensic, and environmental samples.

Use of two selective media and a broth motility test can aid in identification or exclusion of Bacillus anthracis.

During the anthrax attack of 2001, the Florida Department of Health (FDOH) Bureau of Laboratories in Tampa received hundreds of isolates suspected of being Bacillus anthracis. None were confirmed to be B. anthracis since most isolates were motile and not even in the Bacillus cereus group. Although the sentinel laboratories now send fewer isolates to FDOH laboratories, should another attack occur the number of isolates submitted would likely increase dramatically, and this upsurge would seriously challenge personnel who are expected to be busy examining an increased number of environmental samples. We examined two selective and differential growth media and alternative motility methods that could be used to streamline the processing of suspicious isolates. Of 60 isolates previously sent to the FDOH laboratory, 56 were endospore-forming gram-positive rods and only 7 grew on mannitol-egg yolk-polymyxin B agar and/or the Anthracis chromogenic agar. Microscopic observation of early-log-phase growth (2 to 3 h) in a shaking broth was the best method to detect motility in 40 isolates that appeared nonmotile in the motility media investigated. One of these growth media and microscopic examination of shaken broth cultures can be used to show that an isolate is not B. anthracis before expensive molecular and antibody-based tests are performed. By doing so, costs could be reduced and analysis time shortened.

Novel sample preparation method for safe and rapid detection of Bacillus anthracis spores in environmental powders and nasal swabs.

Bacillus anthracis spores have been used as a biological weapon in the United States. We wanted to develop a safe, rapid method of sample preparation that provided safe DNA for the detection of spores in environmental and clinical specimens. Our method reproducibly detects B. anthracis in samples containing <10 spores.

Distribution of mef(A) in gram-positive bacteria from healthy Portuguese children.

We screened 615 gram-positive isolates from 150 healthy children for the presence of the erm(A), erm(B), erm(C), erm(F), and mef(A) genes. The mef(A) genes were found in 20 (9%) of the macrolide-resistant isolates, including Enterococcus spp., Staphylococcus spp., and Streptococcus spp. Sixteen of the 19 gram-positive isolates tested carried the other seven open reading frames (ORFs) described in Tn1207.1, a genetic element carrying mef(A) recently described in Streptococcus pneumoniae. The three Staphylococcus spp. did not carry orf1 to orf3. A gram-negative Acinetobacter junii isolate also carried the other seven ORFs described in Tn1207.1. A Staphylococcus aureus isolate, a Streptococcus intermedius isolate, a Streptococcus sp. isolate, and an Enterococcus sp. isolate had their mef(A) genes completely sequenced and showed 100% identity at the DNA and amino acid levels with the mef(A) gene from S. pneumoniae.