POLQ inhibition attenuates the stemness and ferroptosis resistance in gastric cancer cells via downregulation of dihydroorotate dehydrogenase

Gastric cancer (GC) contains subpopulations of cancer stem cells (CSCs), which are described as the main contributors in tumor initiation and metastasis. It is necessary to clarify the molecular mechanism underlying CSCs phenotype and develop novel biomarkers and therapeutic targets for gastric cancer. Here, we show that POLQ positively regulates stem cell-like characteristics of gastric cancer cells, knockdown of POLQ suppressed the stemness of GC cells in vitro and in vivo. Further mechanistic studies revealed that POLQ knockdown could downregulate the expression of dihydroorotate dehydrogenase (DHODH). DHODH overexpression rescued the reduced stemness resulted by POLQ knockdown. Furthermore, we found that POLQ expression correlated with resistance to ferroptosis, and POLQ inhibition renders gastric cancer cells more vulnerable to ferroptosis. Further investigation revealed that POLQ regulated DHODH expression via the transcription factors E2F4, thereby regulating ferroptosis resistance and stemness of gastric cancer cells. Given the importance of POLQ in stemness and ferroptosis resistance of GC, we further evaluated the therapeutic potential of POLQ inhibitor novobiocin, the results show that novobiocin attenuates the stemness of GC cells and increased ferroptosis sensitivity. Moreover, the combination of POLQ inhibitor and ferroptosis inducer synergistically suppressed MGC-803 xenograft tumor growth and diminished metastasis. Our results identify a POLQ-mediated stemness and ferroptosis defense mechanism and provide a new therapeutic strategy for gastric cancer.

Antimicrobial susceptibility of mastitis pathogens isolated from North American dairy cattle, 2011-2022

A total of 10,890 bacterial isolates of Streptococcus dysgalactiae, Streptococcus uberis, Staphylococcus aureus and Escherichia coli isolated as etiological agents from dairy cows with mastitis by 29 veterinary laboratories across North America between 2011 and 2022 were tested for in vitro antimicrobial susceptibility by broth microdilution to ampicillin, cefoperazone, ceftiofur, cephalothin, erythromycin, oxacillin, penicillin-novobiocin and pirlimycin according to CLSI standards. Using available clinical breakpoints, antimicrobial resistance among S. dysgalactiae (n = 2406) was low for penicillin-novobiocin (0% resistance), ceftiofur (0.1%), erythromycin (3.2%) and pirlimycin (4.6%). Among S. uberis (n = 2398), resistance was low for ampicillin (0%) and ceftiofur (0.2%) and moderate for erythromycin (11.9%) and pirlimycin (18.4%). For S. aureus (n = 3194), resistance was low for penicillin-novobiocin (0%), ceftiofur (0.1%), oxacillin (0.2%), erythromycin (0.7%), cefoperazone (1.2%) and pirlimycin (2.8%). For E. coli (n = 2892), resistance was low for ceftiofur (2.8%) and cefoperazone (3.4%) and moderate for ampicillin (9.2%). Overall, the results indicate that mastitis pathogens in the United States and Canada have not shown any substantial changes in the in vitro susceptibility to antimicrobial drugs over the 12 years of the study, or among that of the proceeding survey from 2002-2010. The data support the conclusion that resistance to common antimicrobial drugs among mastitis pathogens, even to drugs that have been used in dairies for mastitis management for many years, continues to remain low.

Antibacterial potential of Thymus linearis essential oil collected from Wasturwan mountain: A combination of experimental and theoretical studies involving in silico molecular docking simulation of the major compounds against Novobiocin-resistant mutant of DNA Gyrase-B

Antibiotic resistant bacteria are immune to most antibiotics and are therefore very difficult to treat and in most cases lead to death. As such there is a pressing need for alternative and more efficient antibacterial drugs which can target these drug-resistant strains as well. The objective of this research work was to investigate the antibacterial properties of Thymus linearis essential oil (EO) against multiple disease-causing bacterial pathogens. Additionally, the study aimed to examine the molecular docking and molecular dynamic (MD) simulations of the primary components of the EO with the essential bacterial proteins and enzymes. Gas chromatography-mass spectrometry was employed to analyse the chemical composition of Thymus linearis EO. The initial screening for antibacterial properties involved the use of disc diffusion and microdilution techniques. Molecular docking studies were conducted utilising Autodock Vina. The outcomes were subsequently visualised through BIOVIA Discovery Studio. MD simulations were conducted using iMODS, an internet-based platform designed for MD simulations. The essential oil (EO) was found to contain 26 components, with thymol, carvacrol, p-cymene, and γ-terpinene being the primary constituents. The study findings revealed that Thymus linearis EO demonstrated antibacterial effects that were dependent on both the dose and time. The results of molecular docking studies revealed that the primary constituents of the EO, namely thymol, carvacrol, and p-cymene, exhibited robust interactions with the active site of the bacterial DNA gyrase enzyme. This finding provides an explanation for the antibacterial mechanism of the EO. The results indicate that Thymus linearis EO possesses potent antibacterial properties against the MDR microorganisms. Molecular docking analyses revealed that the essential oil's primary components interact with the amino acid residues of the DNA-Gyrase B enzyme, resulting in a favourable docking score.

Whole-genome metagenomic analysis of the oral microbiota in patients with obstructive sleep apnea

PURPOSE

The oral microbiota is closely associated with systemic health, but few studies have investigated the oral microbiota in patients with obstructive sleep apnea (OSA). This study aimed to identify the variation of oral microbiota among patients with severe OSA, and the change of oral microbiota after treatment with continuous positive airway pressure (CPAP).

METHODS

Participants were enrolled in the study from November 2020 to August 2021. Sleep parameters using full nocturnal polysomnography (PSG) were collected on healthy controls, patients with severe OSA, and patients with severe OSA after CPAP treatment for 3 months. Oral samples were also collected by rubbing disposable medical sterile swabs on the buccal mucosa. Routine blood tests and biochemical indicators were measured using the fully automated biochemical analyzer. Oral microbial composition of oral samples were determined using whole-genome metagenomic analysis in all participants. Correlations were analyzed between the oral microbiota and blood lipids.

RESULTS

Study enrollment included 14 participants, 7 healthy controls and 7 patients with severe OSA. At the species level, the relative abundances of Prevotella, Alloprevotella, Bacteroides, Veillonella_tobetsuensis, Candidatus saccharimonas, and Leptotrichia in the groups with severe OSA were significantly lower than those in the healthy controls (P both < 0.05). The abundances of Capnocytophaga, Veillonella, Bacillus_anthracis, Eikenella, and Kingella were significantly higher whereas the abundances of Gordonia and Streptococcus were significantly lower in the group with severe OSA compared to the severe OSA-CPAP group (P < 0.05 for both). According to the Kyoto Encyclopedia of Genes and Genomes (KEGG), 4 pathways changed in the group with severe OSA compared with healthy controls (P both < 0.05). Pathways related to Novobiocin biosynthesis, 2-Oxocarboxylic acid metabolism, and Histidine metabolism were enriched in the patients with severe OSA. Nine pathways showed significant differences with regard to the relative abundances of phenylalanine metabolism; alanine, aspartate, and glutamate metabolism; one carbon pool by folate; monobactam biosynthesis; 2-oxocarboxylic acid metabolism; arginine biosynthesis and vitamin B6 metabolism; novobiocin biosynthesis; and arginine and proline metabolism, which were significantly higher in the group with severe OSA compared to the severe OSA-CPAP group (P both < 0.05). The Spearman correlation analysis between blood lipid parameters and oral microbiota components showed that negative correlations were observed between total cholesterol and Streptomyces (r =  - 0.893, P = 0.007), and high-density lipoprotein cholesterol (HDL-C) and Gordonia (r = - 0.821, P = 0.023); positive correlations were observed between HDL-C and Candidatus saccharimonas (r = 0.929, P = 0.003), and low-density lipoprotein cholesterol (LDL-C) and Capnocytophaga (r = 0.893, P = 0.007).

CONCLUSION

There was an apparent discrepancy of the oral microbiota and metabolic pathways between the group with severe OSA and controls, and CPAP significantly changed oral microbial abundance and metabolic pathways in patients with severe OSA. Correlation analysis showed that these oral bacteria were strongly correlated with the blood lipids level.

Methanobacterium alkalithermotolerans sp. nov., a novel alkaliphilic and hydrogen-utilizing methanogen isolated from an alkaline geothermal spring (La Crouen, New Caledonia)

An anaerobic, hydrogenotrophic methane-producing archaeon was isolated from an alkaline thermal spring (42 °C, pH 9.0) in New Caledonia. This methanogen, designated strain CAN^T, is alkaliphilic, thermotolerant, with Gram-positive staining non-motile cells. Strain CAN^T grows autotrophically using hydrogen exclusively as an energy source and carbon dioxide as the sole carbon source (without the requirement of yeast extract or other organic compounds). It grows at 20-45 °C (optimum, 45 °C) and pH 7.3-9.7 (optimum, pH 9.0). NaCl is not required for growth (optimum 0 %) but is tolerated up to 1.5 %. It resists novobiocin, streptomycin and vancomycin but is inhibited by ampicillin and penicillin, among other antibiotics. The genome consists of a circular chromosome (2.2 Mb) containing 2126 predicted protein-encoding genes with a G+C content of 36.4 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain CAN^T is a member of the genus Methanobacterium, most closely related to the alkaliphilic Methanobacterium alcaliphilum WeN4^T with 98.5 % 16S rRNA gene sequence identity. The genomes of strain CAN^T and M. alcaliphilum DSM 3459, sequenced in this study, share 71.6 % average nucleotide identity and 14.0 % digital DNA-DNA hybridization. Therefore, phylogenetic and physiological results indicate that strain CAN^T represents a novel species, for which the name Methanobacterium alkalithermotolerans sp. nov. is proposed, and strain CAN^T (=DSM 102889^T= JCM 31304^T) is assigned as the type strain.

Multiplex PCR method for the detection of human norovirus, Salmonella spp., Shigella spp., and shiga toxin producing Escherichia coli in blackberry, coriander, lettuce and strawberry

A multiplex PCR method was developed for the simultaneous detection of murine norovirus (MNV-1) as a surrogate for human norovirus (HuNoV) GI and GII, Salmonella spp., Shigella spp., and Shiga toxin producing Escherichia coli (STEC) in fresh produce. The toxicity of the glycine buffer on bacterial pathogens viability was evaluated. The growth of each of the three pathogens (previously stressed) was evaluated at 35 and 41.5 °C in modified buffered peptone water (mBPW) and trypticase soy broth (TSB), supplemented with vancomycin, novobiocin and brilliant green at two concentration levels. The selected conditions for simultaneous enrichment were: 41.5 °C/mBPW/supplemented with 8 ppm vancomycin, 0.6 ppm novobiocin and 0.2 ppm brilliant green. The pathogens and aerobic plate count (APC) growth was evaluated in the enrichment of lettuce, coriander, strawberry and blackberry under the best enrichment conditions. Starting from 1 to 10 CFU/mL, Salmonella reached from 7.63 to 8.91, Shigella 6.81 to 7.76 and STEC 7.43 to 9.27 log CFU/mL. The population reached for the APC was 5.11-6.56 log CFU/mL. Simultaneous detection by PCR was done using designed primers targeting invA, ipaH, stx1 and stx2 genes, and MNV-1. The detection sensitivity was 10-100 PFU for the MNV-1 and 1-10 CFU for each pathogenic bacteria. This protocol takes 6 h for MNV-1 and 24 h for Salmonella spp., Shigella spp., and STEC detection from the same food portion. In total, 200 samples were analyzed from retail markets from Queretaro, Mexico. Two strawberry samples were positive for HuNoV GI and one lettuce sample was positive for STEC. In conclusion, the method developed in this study is capable of detecting HuNoV GI and GII, Salmonella spp., Shigella spp and STEC from the same fresh produce sample.

In silico repurposing of a Novobiocin derivative for activity against latency associated Mycobacterium tuberculosis drug target nicotinate-nucleotide adenylyl transferase (Rv2421c)

Nicotinamide-nucleotide adenylyl transferase (Rv2421c) was selected as a potential drug target, because it has been shown, in vitro, to be essential for Mycobacterium tuberculosis growth. It is conserved between mycobacterium species, is up-regulated during dormancy, has a known 3D crystal structure and has no known human homologs. A model of Rv2421c in complex with nicotinic acid adenine dinucleotide and magnesium ion was constructed and subject tovirtual ligand screening against the Prestwick Chemical Library and the ZINC database, which yielded 155 potential hit molecules. Of the 155 compounds identified five were pursued further using an IC50 based 3D-QSAR study. The 3D-QSAR model validated the inhibition properties of the five compounds based on R2 value of 0.895 and Q2 value of 0.944 compared to known inhibitors of Rv2421c. Higher binding affinities was observed for the novel ZINC13544129 and two FDA approved compounds (Novobiocin sodium salt, Sulfasalazine). Similarly, the total interaction energy was found to be the highest for Cromolyn disodium system (-418.88 kJ/mol) followed by Novobiocin (-379.19 kJ/mol) and Sulfasalazine with (-330.13 kJ/mol) compared to substrate DND having (-185.52 kJ/mol). Subsequent in vitro testing of the five compounds identified Novobiocin sodium salt with activity against Mycobacterium tuberculosis at 50 μM, 25μM and weakly at 10μM concentrations. Novobiocin salt interacts with a MG ion and active site residues His20, Thr86, Gly107 and Leu164 similar to substrate DND of Mycobacterium tuberculosis Rv2421c. Additional in silico structural analysis of known Novobiocin sodium salt derivatives against Rv2421c suggest Coumermycin as a promising alternative for the treatment of Mycobacterium tuberculosis based on large number of hydrogen bond interactions with Rv2421c similar in comparison to Novobiocin salt and substrate DND.

A comparison of rapid bacterial methods to U.S. EPA-approved methods for biosolids

The U.S. Environmental Protection Agency (U.S. EPA) specifies methods for testing microorganisms in biosolids, including U.S. EPA Methods 1680 and 1682 for fecal coliforms and Salmonella sp., respectively. However, these methods require 3 to 5 days to complete. For research or nonregulatory process monitoring purposes, it would be desirable to have a more rapid, less labor-intensive method of enumerating these organisms. The purpose of this study was to compare a modified Colilert with Quanti-Tray/2000 method to U.S. EPA Method 1680 for enumeration of fecal coliforms and E. coli, and to compare spread plating on xylose-lysine deoxycholate (XLD) supplemented with 10 pg/L novobiocin to U.S. EPA Method 1682 for Salmonella sp. in biosolids. These alternative enumeration methods require only 1 day to complete, using fewer costly materials. This limited study indicated that the more rapid methods provide results that are statistically comparable to U.S. EPA methods under most conditions and would be acceptable for rapid, nonregulatory data collection.

In vivo DNA binding of bacteriophage GA-1 protein p6

Bacteriophage GA-1 infects Bacillus sp. strain G1R and has a linear double-stranded DNA genome with a terminal protein covalently linked to its 5' ends. GA-1 protein p6 is very abundant in infected cells and binds DNA with no sequence specificity. We show here that it binds in vivo to the whole viral genome, as detected by cross-linking, chromatin immunoprecipitation, and real-time PCR analyses, and has the characteristics of a histone-like protein. Binding to DNA of GA-1 protein p6 shows little supercoiling dependency, in contrast to the ortholog protein of the evolutionary related Bacillus subtilis phage phi29. This feature is a property of the protein rather than the DNA or the cellular background, since phi29 protein p6 shows supercoiling-dependent binding to GA-1 DNA in Bacillus sp. strain G1R. GA-1 DNA replication is impaired in the presence of the gyrase inhibitors novobiocin and nalidixic acid, which indicates that, although noncovalently closed, the viral genome is topologically constrained in vivo. GA-1 protein p6 is also able to bind phi29 DNA in B. subtilis cells; however, as expected, the binding is less supercoiling dependent than the one observed with the phi29 protein p6. In addition, the nucleoprotein complex formed is not functional, since it is not able to transcomplement the DNA replication deficiency of a phi29 sus6 mutant. Furthermore, we took advantage of phi29 protein p6 binding to GA-1 DNA to find that the viral DNA ejection mechanism seems to take place, as in the case of phi29, with a right to left polarity in a two-step, push-pull process.

Growth inhibitory factors in bovine faeces impairs detection of Salmonella Dublin by conventional culture procedure

AIMS

To analyse the relative importance of different biological and technical factors on the analytical sensitivity of conventional culture methods for detection of Salmonella Dublin in cattle faeces.

METHODS AND RESULTS

Faeces samples collected from six adult bovines from different salmonella-negative herds were split into subpools and spiked with three strains of S. Dublin at a concentration level of c. 10 CFU g(-1) faeces. Each of the 18 strain-pools was divided into two sets of triplicates of four volumes of faecal matter (1, 5, 10 and 25 g). The two sets were pre-enriched with and without novobiocin, followed by combinations of culture media (three types) and selective media (two types). The sensitivity of each combination and sources of variation in detection were determined by a generalized linear mixed model using a split-plot design.

CONCLUSIONS

Biological factors, such as faecal origin and S. Dublin strain influenced the sensitivity more than technical factors. Overall, the modified semi-solid Rappaport Vassiliadis (MSRV)-culture medium had the most reliable detection capability, whereas detection with selenite cystine broth and Mueller Kauffman tetrathionate broth combinations varied more in sensitivity and rarely reached the same level of detection as MSRV in this experiment.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study showed that for MSRV-culture medium and xylose lysine decarboxylase agar as the indicative medium, the sensitivity of the faecal culture method may be improved by focusing on the strain variations and the ecology of the faecal sample. Detailed investigation of the faecal flora (pathogens and normal flora) and the interaction with chemical factors may result in developing an improved method for detection of S. Dublin.

Occurance of Staphylococcus nepalensis strains in different sources including human clinical material

Five isolates of coagulase-negative staphylococci were obtained from human urine, the gastrointestinal tract of squirrel monkeys, pig skin and from the environment. All key biochemical characteristics of the tested strains corresponded with the description of Staphylococcus xylosus species. However, partial 16S rRNA gene sequences obtained from analysed strains corresponded with those of Staphylococcus nepalensis reference strains, except for two strains which differed in one residue. Ribotyping with EcoRI and HindIII restriction enzymes, whole cell protein profile analysis performed by SDS-PAGE and SmaI macrorestriction analysis were used for more precise characterization and identification of the analysed strains. Obtained results showed that EcoRI and HindIII ribotyping and whole cell protein fingerprinting are suitable and reliable methods for the differentiation of S. nepalensis strains from the other novobiocin resistant staphylococci, whereas macrorestriction analysis was found to be a good tool for strain typing. The isolation of S. nepalensis is sporadic, and according to our best knowledge this study is the first report of the occurrence of this species in human clinical material as well as in other sources.

Modeling and predicting the simultaneous growth of Escherichia coli O157:H7 and ground beef background microflora for various enrichment protocols

The simultaneous growth of Escherichia coli O157:H7 (O157) and the ground beef background microflora (BM) was described in order to characterize the effects of enrichment factors on the growth of these organisms. The different enrichment factors studied were basal medium (Trypticase soy broth and E. coli broth), the presence of novobiocin in the broth, and the incubation temperature (37 degrees C or 40 degrees C). BM and O157 kinetics were simultaneously fitted by using a competitive growth model. The simple competition between the two microfloras implied that O157 growth stopped as soon as the maximal bacterial density in the BM was reached. The present study shows that the enrichment protocol factors had little impact on the simultaneous growth of BM and O157. The selective factors (i.e., bile salts and novobiocin) and the higher incubation temperature (40 degrees C) did not inhibit BM growth, and incubation at 40 degrees C only slightly improved O157 growth. The results also emphasize that when the level of O157 contamination in ground beef is low, the 6-h enrichment step recommended in the immunomagnetic separation protocol (ISO EN 16654) is not sufficient to detect O157 by screening methods. In this case, prior enrichment for approximately 10 h appears to be the optimal duration for enrichment. However, more experiments must be carried out with ground beef packaged in different ways in order to confirm the results obtained in the present study for non-vacuum- and non-modified-atmosphere-packed ground beef.

A combination of direct viable count and fluorescent in situ hybridization for estimating Helicobacter pylori cell viability

The viable but non-culturable (VBNC) stage of Helicobacter pylori may represent a problem of public health concern, since these cells cannot be detected by traditional culture methods. In this study, the direct viable count method (DVC) was modified and adapted to H. pylori analysis by testing different times of incubation and concentrations of DNA-gyrase inhibitors. The DVC procedure was combined with fluorescent in situ hybridization (FISH) for the specific detection of viable cells of H. pylori (DVC-FISH). Incubation with 0.5 microg/ml of novobiocin for 24 h provided the optimal conditions for obtaining 3-5 times the original size of Helicobacter viable cells. Field work performed with various types of water (freshwater and seawater) using the DVC-FISH approach enabled us to confirm the presence of VBNC H. pylori cells in 16 of the 45 analyzed samples. The combination of the modified DVC procedure with FISH can provide a rapid and specific method to detect and identify viable cells of H. pylori in environmental samples.

A sequence variant of Staphylococcus hominis with a high prevalence of oxacillin and fluoroquinolone resistance

A newly identified subspecies of Staphylococcus hominis, S. hominis subsp. novobiosepticus, was found to be the cause of several invasive infections at a hospital in New Jersey. This subspecies differs from classical S. hominis, now S. hominis subsp. hominis, by the phenotypic characteristics of novobiocin resistance and the inability to ferment trehalose. DNA sequences of segments of 16S rRNA, DNA gyrase (gyrA), and DNA topoisomerase IV (grlA) genes were determined for the type strains of the 2 subspecies, and for 34 S. hominis clinical isolates. The 16S rRNA sequences of the type strains differed at 3 positions over 410 bp; the grlA sequences differed at 6 positions over 119 bp. These sequence differences define S. hominis subsp. novobiosepticus and S. hominis subsp. hominis "sequevars." Of 34 S. hominis clinical isolates, 31 were S. hominis subsp. novobiosepticus sequevars, 28 of which were resistant to both oxacillin and ciprofloxacin. The clinical microbiology laboratory, using a MicroScan system, identified 7 of the 31S. hominis subsp. novobiosepticus sequevars as S. hominis subsp. hominis on the basis of phenotypic characteristics. Three S. hominis subsp. hominis sequevars were all identified phenotypically as S. hominis subsp. hominis and were oxacillin- and ciprofloxacin-susceptible. Although the precise relationship between the S. hominis sequevars and their phenotypic subspecies remains to be determined, our results indicate that antibiotic-resistant clinical isolates of S. hominis belong almost exclusively to the S. hominis subsp. novobiosepticus sequevar.

Positive effects of some gyrase inhibitors on survival and development of Pimpla turionellae (Hymenoptera: Ichneumonidae) larvae reared on an artificial diet

Effects of novobiocin, nalidixic, and oxolinic acids on the survival and development of the hymenopterous endoparasitoid Pimpla turionellae L. were investigated alone and in various combinations by rearing larvae aseptically on chemically defined synthetic diets. Effects varied with the levels and kinds of the antibiotics in the tested combinations. Among the tested antibiotics alone, only the lowest level of novobiocin enhanced the postlarval survival. Most of the combinations significantly increased the number of survivors in the postlarval developmental stages. Novobiocin in combination with nalidixic acid (6.0:2.0 mg) in the artificial diet produced a yield of 80.8% pupae and 69.4% adults, respectively. This combination also shortened the developmental time to adult emergence. Similarly, on most of the diets with combinations of the antibiotics, the development of the larvae up to adult stage was noticeably faster than those on the control diets. An approximately equals 50% reduction in the percentages of pupae and adults was recorded by 6.0 mg of novobiocin in combination with 0.75 mg of oxolinic acid compared with the control diet. Although this combination prolonged the complete development of the insect according to other novobiocin and oxolinic acid combinations, developmental time was significantly shorter than that with control diet.

A novel chromogenic ester agar medium for detection of Salmonellae

A novel agar medium, chromogenic Salmonella esterase (CSE) agar, for the differentiation of salmonellae is described. The agar contains peptones and nutrient extracts together with the following (grams per liter unless otherwise specified): 4-[2-(4-octanoyloxy-3, 5-dimethoxyphenyl)-vinyl]-quinolinium-1-(propan-3-yl carboxylic acid) bromide (SLPA-octanoate; bromide form), 0.3223; lactose, 14. 65; trisodium citrate dihydrate, 0.5; Tween 20, 3.0; ethyl 4-dimethylaminobenzoate, 0.035% (wt/vol), novobiocin, 70 mg liter-1. The key component of the medium is SLPA-octanoate, a newly synthesized ester formed from a C8 fatty acid and a phenolic chromophore. In CSE agar, the ester is hydrolyzed by Salmonella spp. to yield a brightly colored phenol which remains tightly bound within colonies. After 24 h of incubation at 37 or 42 degreesC, colonies of typical Salmonella spp. were burgundy colored on a transparent yellow background, whereas non-Salmonella spp. were white, cream, yellow or transparent. CSE agar was evaluated by using a panel of strains including a high proportion of Salmonella and non-Salmonella strains giving atypical reactions on other differential agars. The sensitivity (93.1%) of CSE agar for non-typhi salmonellae compared favorably with those of Rambach (82. 8%), xylose-lysine-deoxycholate (XLD; 91.4%), Hektoen-enteric (89.7%), and SM ID (91.4%) agars. The specificity (93.9%) was also comparable to those of other Salmonella media (SM ID agar, 95.9%; Rambach agar, 91.8%; XLD agar, 91.8%; Hektoen-enteric agar, 87.8%). Strains of Citrobacter freundii and Proteus spp. giving false-positive reactions with other media gave a negative color reaction on CSE agar. CSE agar enabled the detection of >30 Salmonella serotypes, including agona, anatum, enteritidis, hadar, heidelberg, infantis, montevideo, thompson, typhimurium, and virchow, which accounted for 91.8% of the salmonella isolates recorded by the Public Health Laboratory Service (Colindale, London, England) for 1997.

Inhibition by antibiotics of the growth of bacterial and yeast protoplasts

Shockman, Gerald D. (Temple University School of Medicine, Philadelphia, Pa.) and J. Oliver Lampen. Inhibition by antibiotics of the growth of bacterial and yeast protoplasts. J. Bacteriol. 84:508-512. 1962.-The characteristics and requirements for growth of bacterial (Streptococcus faecalis) and yeast (Saccharomyces cerevisiae) protoplasts were established and the effect of a variety of antibacterial and antifungal antibiotics determined. A clear differentiation was obtained between such inhibitors of bacterial cell wall synthesis as penicillin and cycloserine, which did not prevent protoplast growth, and all others, antibacterial and antifungal, which inhibited protoplasts and intact organisms at the same range of concentration. Novobiocin, previously reported to inhibit bacterial wall synthesis, was also effective against a reaction(s) essential to the growth of S. faecalis protoplasts. The antibacterial action of streptomycin, neomycin, and kanamycin was essentially eliminated by the high salt concentration needed to maintain the protoplasts. Removal of the cell wall did not significantly increase antibiotic susceptibility of a resistant species. Protoplasts of Bacillus megaterium were insensitive to the antifungal agent, nystatin, and did not bind it to any detectable degree. Thus, the yeast or bacterial cell wall does not appear to play a major role in determining relative antibiotic susceptibility by masking internal sensitive target sites. A variety of antifungal antibiotics tested on the growth of log-phase yeast cells failed to produce osmotically fragile forms.

Coagulase-negative strains of staphylococcus possessing antigen 51 as agents of urinary infection

A group of strains of Staphylococcus albus is described which produced neither coagulase nor haemolysin, was slightly sensitive or resistant to novobiocin, and sensitive to all other antibiotics, to sulphonamides, and to nitrofurantoin. The agglutinating antigen 51 was isolated from all strains from patients with urinary infections and abundant pyuria. In more than 40 cases studied it was not possible to isolate any other bacterial agent, and the cure of clinical symptoms always coincided with the disappearance of the coagulase-negative staphylococcus strain.

Effects of magnesium ion deficiency on Escherichia coli and possible relation to the mode of action of novobiocin

Brock, Thomas D. (Indiana University, Bloomington). Effects of magnesium ion deficiency on Escherichia coli and possible relation to the mode of action of novobiocin. J. Bacteriol. 84:679-682. 1962.-Cells of Escherichia coli ML35 grew in magnesium-deficient medium at an arithmetic rate for 4 to 5 hr. In the later stages of this period, the viability of the cells decreased, ribonucleic acid was lost, and the cells became able to hydrolyze o-nitro-phenyl-beta-d-galactoside at a much increased rate. Further, the cells became filamentous and stained less intensely with methylene blue. Since magnesium ions are known to stabilize cell membranes, the changes are interpreted as due to alterations in membrane integrity. Novobiocin induced the same changes as magnesium ion deficiency, providing further support for the hypothesis that novobiocin acts by inducing a magnesium ion deficiency.

EFFECT OF ANTIBIOTICS AND INHIBITORS ON M PROTEIN SYNTHESIS

Brock, Thomas D. (Western Reserve University, Cleveland, Ohio). Effect of antibiotics and inhibitors on M protein synthesis. J. Bacteriol. 85:527-531. 1963.-This work extends the observations of Fox and Krampitz on M protein synthesis in nongrowing cells of streptococci. A survey of a large number of antibiotics and other potential inhibitors was made. Some substances bring about inhibition of fermentation and inhibit M protein synthesis because they deprive the cell of the energy needed for this process. A second group of substances inhibit growth at concentrations tenfold or more lower than they inhibit M protein synthesis. These are the antibiotics which inhibit synthesis of cell wall or other structures in growing cells, but do not affect protein synthesis. A third group of substances inhibit growth and M protein synthesis at the same concentration. These substances probably inhibit growth because they inhibit general protein synthesis, and are therefore specific inhibitors of protein synthesis. In this class are chloramphenicol, erythromycin, and the tetracyclines. Several other antibiotics of previously unknown mode of action are in this class. A fourth group of substances had no effect on M protein synthesis. No substances were found which inhibited M protein synthesis at a lower concentration than that which inhibited growth. M protein synthesis in nongrowing cells may be a useful model system for obtaining a detailed understanding of protein synthesis.

NITROUS ACID REACTIVATION OF ULTRAVIOLET-IRRADIATED TRANSFORMING DNA FROM HEMOPHILUS INFLUENZAE

Partial recovery of ultraviolet-damaged denatured or native transforming DNA from Hemophilus influenzae, has been obtained by exposing the irradiated DNA in the denatured form to nitrous acid. Some factors that affect this recovery are described. An erythromycin marker (E₂₀) was not reactivated. The UV damage reactivable by nitrous acid is different from that repaired by the photoreactivating enzyme from bakers' yeast. The pretreatment with nitrous acid affords a slight protection for denatured C₂₅ DNA and Sm₂₅₀ DNA against ultraviolet irradiation, but this pretreatment sensitized the E₂₀ DNA to this irradiation.

STAPHYLOCOCCUS AUREUS TYPE 83A AS A CAUSE OF HOSPITAL CROSS-INFECTION

1. A retrospective survey has been made to determine the amount of cross-infection caused by Staphylococcus aureus of one particular phage-type, 83 A, in four main hospitals of a provincial hospitals group, over a period of 2½ years.

2. The total number of strains considered was 1131. Of these, 776 were resistant to tetracycline and therefore the most likely to be of significance in cross-infection. Of these 776 strains, about one-third belonged to phage-type 83 A. In the hospital where 83 A strains were most prevalent, they formed about one-half of the tetra cycline-resistant strains; in that where they were least prevalent, about one- quarter.

The clinical sources of the tetracycline-resistant strains are described.

3. It was found that type 83 A strains were the most likely to show resistance to erythromycin, chloramphenicol or novobiocin.

Of a series of 214 type 83 A strains sensitivity tested against methicillin, using a disk-plate method, none was found to be resistant.

My thanks are due to Prof. R. E. O. Williams, St Mary' Hospital Medical School, for his helpful criticism of this paper and, in his previous capacity as Director of the Staphylococcus Reference Laboratory, Central Public Health Laboratory, Colindale, to him and his staff for supplying me with typing phages, and instructing me in their use. I should also like to thank Dr M. T. Parker, Director of the Cross Infection Reference Laboratory, Colindale, for a continued supply of these phages; the Hon. the Viscount Waverley, F.R.C.P., for allowing me to quote from the case history of a patient under his care; and Mr K. Allen, F.I.M.L.T., and other members of my technical staff for their assistance.

URINARY TRACT INFECTIONS DUE TO COAGULASE-NEGATIVE STAPHYLOCOCCI

A survey of Staphylococcus albus urinary infections is reported from a general hospital. The infection followed urethral instrumentation in 75% of the patients, and was usually caused by organisms already present in the urethra. Novobiocin-resistant strains caused infections in four out-patients with no predisposing lesions or instrumentation of the urinary tract.

ANTIBIOTIC SENSITIVITY OF PROTEUS SPECIES

A study has been made of the antibiotic sensitivity pattern of 96 strains of Proteus isolated from clinical material and a further 29 strains kindly supplied by Dr. Patricia Carpenter. The results have been analysed in relation to the different species. The effect of electrolytes on the penicillin sensitivity of Proteus species has also been examined.

EFFECT OF INTERSPECIFIC TRANSFORMATION ON LINKAGE RELATIONSHIPS OF MARKERS IN HAEMOPHILUS INFLUENZAE AND HAEMOPHILUS PARAINFLUENZAE

Nickel, Lois (University of Pennsylvania, Philadelphia), and Sol H. Goodgal. Effect of interspecific transformation on linkage relationships of markers in Haemophilus influenzae and Haemophilus parainfluenzae. J. Bacteriol. 88:1538-1544. 1964.-Highly competent cells of Haemophilus parainfluenzae were obtained by a modification of the aerobic-"anaerobic" method of Goodgal and Herriott. The mutant markers for streptomycin and novobiocin resistance in H. parainfluenzae were shown to be unlinked. These same markers were transferred into H. influenzae in two transformation steps, and the deoxyribonucleic acid (DNA) was extracted. Transformation of recipient H. influenzae with DNA from the latter showed the markers to be linked, and transformation of recipient H. parainfluenzae with this DNA showed that the markers were not cotransferred. The linked streptomycin- and novobiocin-resistance mutations of H. influenzae were transformed into H. parainfluenzae in two stages, and the DNA was extracted. Transformation of recipient H. parainfluenzae with this DNA demonstrated the markers to be unlinked in H. parainfluenzae. When these markers, originally from H. influenzae and present as unlinked factors in H. parainfluenzae, are transferred back into H. influenzae, the markers showed their original linkage. The novobiocin- and erythromycin-resistance markers of H. influenzae were unlinked in H. influenzae, but were linked when transferred into H. parainfluenzae. The erythromycin-resistance marker of H. influenzae, when transferred into a novobiocin-resistant mutant of H. parainfluenzae, showed linkage with it. Evidence is presented to show that H. parainfluenzae streptomycin and novobiocin markers are homologous to streptomycin and novobiocin markers in H. influenzae.

INDUCTION BY ANTIBIOTICS AND COMPARATIVE SENSITIVITY OF L-PHASE VARIANTS OF STAPHYLOCOCCUS AUREUS

Molander, C. W. (Cedars of Lebanon-Mount Sinai Hospitals, Los Angeles, Calif.), B. M. Kagan, H. J. Weinberger, E. M. Heimlich, and R. J. Busser. Induction by antibiotics and comparative sensitivity of L-phase variants of Staphylococcus aureus. J. Bacteriol. 88:591-594. 1964.-The penicillins, cephalothin, vancomycin, and bacitracin were found to be less inhibitory to the L-phase variants than to their respective parent bacteria. Those antibiotics not considered to be primarily inhibitors of cell-wall synthesis were, in general, somewhat more inhibitory to the L form than to their parent bacteria. Only the penicillins and cephalothin readily induced L-phase variation. Novobiocin induced pleomorphic growth resembling the earliest stages of L-phase transformation. Failure of observable induction by bacitracin and vancomycin suggests that these two antibiotics affect cell-wall synthesis in a manner different from the penicillins, or that L-phase transformation may require more than "penicillin-like" interference with cell-wall synthesis.

ISOLATION OF L FORMS FROM GROUP A STREPTOCOCCI EXPOSED TO BACITRACIN

Rotta, Jiri (Washington University School of Medicine, St. Louis, Mo.), Walter W. Karakawa, and Richard M. Krause. Isolation of L forms from group A streptococci exposed to bacitracin. J. Bacteriol. 89:1581-1585. 1965.-L forms were obtained from group A streptococci by exposure to bacitracin on gradient plates, although novobiocin was ineffective in this respect. Subcultures of these L forms had morphological and bacteriological properties similar to those obtained with penicillin. M protein was detected in L-form colony smears by immunofluorescent staining with type-specific conjugate. The L forms were not stained with group-specific conjugate. Parallel precipitin tests performed with extracts from a heavy growth of L forms on agar confirmed these findings. Thus, the L forms obtained with bacitracin continue to produce M protein but are devoid of the group-specific carbohydrate which is a major component of cell-wall structure.

New selective media for isolation of clostridia from faecal specimens

Two selective media, novobiocin-colistin agar (NCA) and colistin-crystal violet agar (CCA), were developed for isolating clostridia from human and animal faeces. The basal medium was modified Eggerth-Gagnon agar. The NCA medium contains novobiocin (8 micrograms ml-1) and colistin (8 micrograms ml-1) and the CCA medium contains colistin (10 micrograms ml-1) and crystal violet (10 micrograms ml-1). Nine faecal specimens were cultured. Clostridia isolated on these media were similar to those on non-selective media, and higher than those isolated after heat treatment. However, more clostridial species were isolated on the new selective media compared with the non-selective medium. These selective agars were particularly useful for enumerating and isolating clostridia from human faeces.

[Evaluation of three new culture media: brilliant-glycerol-lactose novobiocin-green agar, modified iron lysin agar and Rambach agar for the isolation of enteropathogenic E. coli, Salmonella sp. in acute gastroenteritis]

BACKGROUND

Acute gastroenteritis (AGE) is one of the most common diseases in children, particularly in those under the age of 5 years in whom a severe picture of hydroelectrolyte imbalance may be triggered accompanied, in most cases, by leukocyte response. The aim of this study was to evaluate three new culture media for the isolation of enteropathogens in infantile diarrhea.

MATERIAL AND METHODS

From April to September, 1993, 170 samples of diarrhea stools from children up to 7 years of age attending pediatric hospitals in Bogota were studied. Three new culture media were used in the isolation of the enteropathogenic bacteria: BGLN, MILA agar, Rambach agar and a conventional agar medium S.S. Biochemical tests were performed to identify the isolated bacteria.

RESULTS

A total of 98.5% of enteropathogenic E. coli was isolated in Rambach agar, which also presented excellent recovery rates of Salmonella sp. (100%) versus S.S> (64.3%) and BGLN (77.2%), respectively. The best selectivity for Shigella sp. was observed with BGLN with a 100% recovery rate. Out of the 170 samples 105 showed a leukocyte count of 70-75% and positive isolation for enteropathogenic bacteria. Six samples with the same leukocyte count did not present enteropathogenic bacteria, with the 59 remaining samples with a 20-25% PMN count being negative for enteropathogenic bacteria.

CONCLUSIONS

The results suggest that the new culture media used in this study may have better recovery rates for enteropathogenic bacteria in acute gastroenteritis. Likewise, a correlation was observed between leukocyte count and isolation enteropathogenic bacteria.

Study of Rambach and NBGL agar on 4037 stools of human origin and 584 veterinary samples submitted for isolation of Salmonellae

Rambach agar and novobiocin-brilliant green-glycerol-lactose (NBGL) agar are two recently described media designed for Salmonella isolation. Rambach and NBGL agars were compared to usual media in human and veterinary routines, by evaluation of sensitivities and predictive values of suspect colonies. In the human routine, 4037 stools, sensitivities were 79% for Hektoen agar, 51% for Rambach agar and 96% for NBGL agar at the direct plating for a total of 94 strains; and 89%, 87% and 94% respectively at the plating of Mueller-Kauffmann enrichment broth for a total of 143 strains. Predictive values of suspect colonies were respectively 58%, 93%, 91% at the direct plating; and 25%, 74%, 80% at the plating of Mueller-Kauffmann enrichment broth. In the veterinary routine, 584 samples, sensitivity was 65% on the association of Salmonella-Shigella and Hektoen agars, 70% on Rambach agar and 85% on NBGL agar, for a total of 40 strains. Predictive values of suspect colonies were 7.4%, 82.3% and 83% respectively. These results showed that Rambach and NBGL agars have distinct properties, and are both highly predictive. The highest sensitivities were achieved by the NBGL agar.

Novobiocin-brilliant green-glycerol-lactose-agar: further routine evaluation on 5554 human stools and 982 veterinary samples

In order to provide a wider evaluation of "Novobiocin-brilliant green-glycerol-lactose" (NBGL) agar, dishes of this medium were added to standard media: Hektoen (H), Salmonella-Shigella agar (SS), at all plating steps for 5554 stool cultures of human medical routine (280 isolates) and 982 samples of veterinary routine (133 isolates). NBGL expectedly missed lactose-glycerol positive strains of the serotype Senftenberg (n = 4), H2S negative strains (n = 1), and strains of the Typhi serotype (n = 7). Otherwise, three strains, of serotype Virchow, were unable to grow on NBGL (0.7% of positive samples). Nevertheless overall sensitivities were increased by approximately 10% in the human routine (H: 70%; SS: 63%; NBGL: 94%; at the direct plating step) (H: 83%; SS: 84%; NBGL: 92%; at the enrichment plating step) and by 48% in the veterinary one (NBGL: 97%; versus usual media: 68%). Positive predictive values of black centred colonies were significantly higher on NBGL in human routine (H: 38%; SS: 40%; NBGL: 89%; at the direct plating step) (H: 20%; SS: 21%; NBGL: 82%; at the enrichment plating step); and in the veterinary one as well (NBGL: 90%; versus usual media: 17%). These data suggest that NBGL agar does improve Salmonella isolation in these kinds of routines, and that growth should be made sure before experiments using given strains.

Novobiocin, brilliant green, glycerol, lactose agar: a new medium for the isolation of Salmonella strains

We describe a medium, novobiocin, brilliant green, glycerol, lactose (NBGL) agar, for the routine isolation of Salmonella strains from stool samples. The NBGL agar principle involved the use of the antisaprophytic effect of brilliant green and novobiocin. Glycerol and lactose were added in order to distinguish between Citrobacter and Salmonella. NBGL was used in parallel with salmonella-shigella (SS) and Hektoen (H) agar for culturing 2,853 stool samples, of which 184 were confirmed to be salmonellae. NBGL showed a high sensitivity: 94% in direct plating compared to 74% (p < 10(-3)) and 65% (p < 10(-5)) for H and SS, respectively, and 96% in enrichment broth plating vs. 83% (p < 10(-4)) and 86% (p < 10(-3)), respectively, for H and SS. In direct plating using NBGL, 95% of black-centred colonies were confirmed to be salmonellae (vs. 31% and 36%, H and SS). In enrichment plating using NBGL, this figure was 82% (vs. 26% and 28%). The results suggest that NBGL agar is advantageous for the isolation of non-Typhi H2S+ salmonellae.