The use of the anti-Acholeplasma activities of Streptomyces culture filtrates for the screening of new antibiotics.

A screening method for new antimicrobial agents from streptomyces culture filtrates was developed. Three different types of test organisms were used for determining the antimicrobial activities of the culture filtrates: they were (a) an antibacterial activity test against Staphylococcus aureus, (b) an antimycoplasmal activity test against Acholeplasma laidlawii, and (c) a cytotoxicity test against HeLa-S3 cells. The active filtrates showing antimicrobial spectra (anticellogram) which did not match those of known antimicrobial agents were used for further purification to obtain new antimicrobial agents. Of these screening methods, antimycoplasmal activity against Acholeplasma laidawii was the most sensitive for discriminating new compounds contained in the filtrates of known antibiotics.     

Effect of electrical current on the activities of antimicrobial agents against Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis biofilms

Bacterial biofilms are resistant to conventional antimicrobial agents. Prior in vitro studies have shown that electrical current (EC) enhances the activities of aminoglycosides, quinolones, and oxytetracycline against Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus epidermidis, Escherichia coli, and Streptococcus gordonii. This phenomenon, known as the bioelectric effect, has been only partially defined. The purpose of this work was to study the in vitro bioelectric effect on the activities of 11 antimicrobial agents representing a variety of different classes against P. aeruginosa, methicillin-resistant Staphylococcus aureus (MRSA), and S. epidermidis. An eight-channel current generator/controller and eight chambers delivering a continuous flow of fresh medium with or without antimicrobial agents and/or EC to biofilm-coated coupons were used. No significant decreases in the numbers of log(10) CFU/cm(2) were seen after exposure to antimicrobial agents alone, with the exception of a 4.57-log-unit reduction for S. epidermidis and trimethoprim-sulfamethoxazole. We detected a statistically significant bioelectric effect when vancomycin plus 2,000 microamperes EC were used against MRSA biofilms (P = 0.04) and when daptomycin and erythromycin were used in combination with 200 or 2,000 microamperes EC against S. epidermidis biofilms (P = 0.02 and 0.0004, respectively). The results of these experiments indicate that the enhancement of the activity of antimicrobial agents against biofilm organisms by EC is not a generalizable phenomenon across microorganisms and antimicrobial agents.     

In vitro activities of 14 antibiotics against 100 human isolates of Yersinia pestis from a southern African plague focus.

A limited repertoire of antimicrobial agents is currently in use for the treatment of plague. We investigated the in vitro activities of some newer antimicrobial agents against Yersinia pestis. Among the injectable agents tested, cefotaxime was the most active, and among the oral agents, both levofloxacin and ofloxacin were highly active, with MICs at which 90% of isolates are inhibited of < 0.03 microgram/ml. the susceptibilities to the ketolide RU004 and the penem faropenem warrant attention. The enhanced activities of quinolones against Y. pestis suggest that these agents should be further investigated for the treatment of human plague in the future.     

Bactericidal activity of antimicrobial agents against slowly growing Helicobacter pylori.

The doubling times of bacteria at sites of colonization or infection are considerably longer than those in laboratory culture media, and slow growth reduces the susceptibility of bacteria to antimicrobial agents. Helicobacter pylori is susceptible to a wide range of antimicrobial agents in vitro; however, tests for inhibitory activity do not adequately predict which antimicrobial agents will eradicate slowly growing H. pylori from the stomachs of patients. The chemostat can be used to compare the bactericidal activities of antimicrobial substances against slowly growing bacteria. In this study we compared the bactericidal activities of antimicrobial agents against slowly growing H. pylori. The bactericidal activities of erythromycin, minocycline, ampicillin, amoxicillin, cefixime, metronidazole, and bismuth subcitrate against slowly growing H. pylori NCTC 11,637 in a chemostat were compared. Antimicrobial agents were added to the system at four to eight times the MIC. Exposure of H. pylori to metronidazole was associated with the rapid development of metronidazole resistance, preventing assessment of the bactericidal activity of metronidazole. Resistance to the other antimicrobial agents tested did not develop. The poor bactericidal activities of the antimicrobial agents against slowly growing H. pylori may be a contributory factor in limiting their clinical efficacies. Of the agents tested, only amoxicillin and bismuth subcitrate showed bactericidal activity against slowly growing H. pylori. The chemostat allows comparison of the bactericidal activities of antimicrobial agents against slowly growing H. pylori and may therefore provide results which more accurately identify those agents or combinations of agents that will eradicate H. pylori from patients.     

Low-oxygen-recovery assay for high-throughput screening of compounds against nonreplicating Mycobacterium tuberculosis

Screening for new antimicrobial agents is routinely conducted only against actively replicating bacteria. However, it is now widely accepted that a physiological state of nonreplicating persistence (NRP) is responsible for antimicrobial tolerance in many bacterial infections. In tuberculosis, the key to shortening the 6-month regimen lies in targeting this NRP subpopulation. Therefore, a high-throughput, luminescence-based low-oxygen-recovery assay (LORA) was developed to screen antimicrobial agents against NRP Mycobacterium tuberculosis. M. tuberculosis H37Rv containing a plasmid with an acetamidase promoter driving a bacterial luciferase gene was adapted to low oxygen conditions by extended culture in a fermentor with a 0.5 headspace ratio. The MICs of 31 established antimicrobial agents were determined in microplate cultures maintained under anaerobic conditions for 10 days and, for comparative purposes, under aerobic conditions for 7 days. Cultures exposed to drugs under anaerobic conditions followed by 28 h of "recovery" under ambient oxygen produced a luminescent signal that was, for most compounds, proportional to the number of CFU determined prior to the recovery phase. No agents targeting the cell wall were active against NRP M. tuberculosis, whereas drugs hitting other cellular targets had a range of activities. The calculated Z' factor was in the range of 0.58 to 0.84, indicating the suitability of the use of LORA for high-throughput assays. This LORA is sufficiently robust for use for primary high-throughput screening of compounds against NRP M. tuberculosis.     

Comparison of the antimicrobial effects of chlorine, silver ion, and tobramycin on biofilm

The systematic understanding of how various antimicrobial agents are involved in controlling biofilms is essential in order to establish an effective strategy for biofilm control, since many antimicrobial agents are effective against planktonic cells but are ineffective when they are used against the same bacteria growing in a biofilm state. Three different antimicrobial agents (chlorine, silver, and tobramycin) and three different methods for the measurement of membrane integrity (plate counts, the measurement of respiratory activity with 5-cyano-2,3-ditolyl tetrazolium chloride [CTC] staining, and BacLight Live/Dead staining) were used along with confocal laser scanning microscopy (CLSM) and epifluorescence microscopy to examine the activities of the antimicrobials on biofilms in a comparative way. The three methods of determining the activities of the antimicrobials gave very different results for each antimicrobial agent. Among the three antimicrobials, tobramycin appeared to be the most effective in reducing the respiratory activity of biofilm cells, based upon CTC staining. In contrast, tobramycin-treated biofilm cells maintained their membrane integrity better than chlorine- or silver-treated ones, as evidenced by imaging by both CLSM and epifluorescence microscopy. Combined and sequential treatments with silver and tobramycin showed an enhanced antimicrobial efficiency of more than 200%, while the antimicrobial activity of either chlorine or tobramycin was antagonized when the agents were used in combination. This observation makes sense when the different oxidative reactivities of chlorine, silver, and tobramycin are considered.     

In vitro antimicrobial susceptibilities of strains of Yersinia pestis.

The in vitro activities of 14 antimicrobial agents were determined for 78 strains of Yersinia pestis. The most active antibiotics were ceftriaxone and ciprofloxacin, followed by ofloxacin and ampicillin. The agents traditionally used for the treatment of plague (streptomycin, tetracycline, and chloramphenicol) were considerably less active. Azithromycin showed poor activity against all strains.     

The in-vitro bactericidal activities of combinations of antimicrobial agents against clinical isolates of Mycobacterium avium-intracellulare.

The in-vitro activities of five antimicrobial agents (rifabutin, clarithromycin, ethambutol, ciprofloxacin and amikacin), alone and in combination, were evaluated against 21 strains of Mycobacterium avium-intracellulare isolated from patients with AIDS. The combined activities of these agents were studied on solid medium by a full chequerboard method. Synergy was demonstrated most frequently (28-71% of isolates) with those combinations that included ethambutol. In killing curve experiments where double and triple combinations of agents were tested against two of the strains, 99% kill was achieved in seven days at concentrations well below those that are attainable in serum. However, an additive rather than a synergic effect was seen in most instances. Although ciprofloxacin alone had the greatest bactericidal activity against these two strains, its activity was antagonized in the presence of rifabutin; this antagonism became inapparent when a third agent was added. Demonstration of bactericidal activity in broth culture may be more relevant than the results of susceptibility testing on solid medium when choosing antimicrobial therapy for patients with this infection.     

In vitro activities of antimicrobial agents against clinical isolates of Flavimonas oryzihabitans obtained from patients with cancer.

We evaluated the in vitro activities of 21 different antimicrobial agents against nine clinical isolates of Flavimonas oryzihabitans obtained from patients with cancer. The organisms were susceptible to most agents commonly used for the empiric therapy (aminoglycosides, ureidopenicillins, extended-spectrum cephalosporins, monobactams, and carbapenems) and prevention of infections (quinolones and trimethoprim-sulfamethoxazole) in this patient population.     

Comparative in vitro activities of ciprofloxacin, gemifloxacin, grepafloxacin, moxifloxacin, ofloxacin, sparfloxacin, trovafloxacin, and other antimicrobial agents against bloodstream isolates of gram-positive cocci

The in vitro activity of gemifloxacin against 316 bloodstream isolates of staphylococci, pneumococci, and enterococci was compared with the activities of six fluoroquinolones and three other antimicrobial agents. Of the antimicrobial agents tested, gemifloxacin was the most potent against penicillin-intermediate and -resistant pneumococci, methicillin-susceptible and -resistant Staphylococcus epidermidis isolates, and coagulase-negative staphylococci.     

Comparative in vitro activities of teicoplanin, vancomycin, oxacillin, and other antimicrobial agents against bacteremic isolates of gram-positive cocci.

The in vitro activities of teicoplanin and vancomycin were compared with those of six other antimicrobial agents against 460 bacteremic isolates of gram-positive cocci. Teicoplanin was as active as vancomycin but less active than ciprofloxacin against staphylococci. Teicoplanin was the most potent of all agents tested against enterococci and had excellent activity against pneumococci.     

Relationship between structure and antiplaque and antimicrobial activities for a series of bispyridines.

A series of bispyridines were examined for their bactericidal activities against in vitro, preformed, pure-culture plaques of selected oral plaque-forming bacteria. The antimicrobial activities of these agents were examined in relation to their molecular configurations. These studies demonstrated that the length of the interpyridine polymethylene group bridge and the length of the alkyl side chain were important determinants of antiplaque and antimicrobial efficacy. The most potent compounds of the bispyridine series were studied to determine the minimal conditions (concentration, duration, and frequency) of treatment required for likely clinical efficacy.     

Mutations of chronic granulomatous disease in Turkish families

BACKGROUND: Chronic granulomatous disease (CGD) is an inherited disorder of the innate immune system characterized by impairment of intracellular microbicidal activity of phagocytes. Mutations in one of four known NADPH-oxidase components preclude generation of superoxide and related antimicrobial oxidants, leading to the phenotype of CGD. Defects in gp91-phox, encoded by CYBB, lead to X-linked CGD and have been reported to be responsible for approximately 70% of all CGD cases. The aim of this study was to identify the CGD mutations in a group of Turkish CGD patients and to evaluate the predominance of CGD mutations as X-linked or autosomal recessive (AR) within the Turkish CGD families with known mutations. MATERIALS AND METHODS: Two Turkish CGD families were included in the study, and mutations were identified by sequence analysis of DNA and RNA from peripheral blood in the patients. Before mutation analysis, subgroup analysis of patients was made by flow cytometry with antibodies against NADPH oxidase components and with DHR-123 oxidase activity assay. For comparison, we included previously reported results from four other Turkish CGD families. RESULTS: Two different mutations were identified, one of them a novel mutation g.700G>T located in exon 7 of CYBB, and the other a hot-spot mutation located in exon 2 of the NCF1 gene. These mutations were detected in three patients from two Turkish families. CONCLUSIONS: Until now, we have altogether identified mutations in six Turkish CGD families. In this limited number of families our results show AR-CGD in two-thirds of the Turkish families investigated, in contrast to previous reports in the literature. This is probably due to the high rate of consanguineous marriages in Turkey. Consanguineous parents were found in 75% of the families with AR-CGD patients, which favours homozygous deficiencies.     

Comparative in vitro activities of ofloxacin, difloxacin, ciprofloxacin, and other selected antimicrobial agents against Brucella melitensis.

The in vitro activities of three quinolones (ofloxacin, difloxacin, and ciprofloxacin) were compared with those of trimethoprim-sulfamethoxazole, streptomycin, tetracycline, and rifampin against 47 Brucella melitensis strains. Ofloxacin was the most active of the test antimicrobial agents. It inhibited 90% of B. melitensis strains at a concentration of 0.02 micrograms/ml.     

In vitro susceptibility of Campylobacter fetus subsp. jejuni to N-formimidoyl thienamycin, rosaramicin, cefoperazone, and other antimicrobial agents

The activities of 11 antimicrobial agents against 36 strains of Campylobacter fetus subsp. jejuni were studied by a broth microdilution method. All strains were susceptible to 7 of the 11 antimicrobial agents. Of the newer agents tested N-formimidoyl thienamycin (MK0787) and rosaramicin had very good activity, whereas cefotaxime, moxalactam, and cefoperazone had poorer activity.     

Comparative in vitro activity of moxalactam, cefotaxime, cefoperazone, piperacillin, and aminoglycosides against gram-negative bacilli

The in vitro activities of four new beta-lactam antimicrobial agents (moxalactam, cefotaxime, cefoperazone, and piperacillin) and the aminoglycosides against 744 recent clinical isolates of facultative gram-negative bacilli were compared simultaneously by the agar dilution method. The major in vitro difference of these newer beta-lactam compounds appeared to be their antipseudomonal activity; cefoperazone was the most active, whereas cefotaxime had the least potency. The aminoglycosides, however, had the most effective in vitro activity on a weight basis against Pseudomonas aeruginosa.     

In vitro activities of iodonium salts against oral and dental anaerobes

The comparative in vitro activities of 11 iodonium salt compounds, 0.12% chlorhexidine, and four antimicrobial agents against 322 anaerobic and fastidious potential dental and periodontal bacterial pathogens were studied. Iodonium salts 3, 4, 5, 9, and 10 had in vitro activities comparable to that of chlorhexidine against most isolates. These compounds may be suitable for incorporation into an oral mouthwash.     

Comparative in vitro activities of trovafloxacin (CP-99,219) against 221 aerobic and 217 anaerobic bacteria isolated from patients with intra-abdominal infections.

Four hundred thirty-eight bacteria cultured from specimens of patients with serious intra-abdominal infections were tested by agar dilution against trovafloxacin and other quinolones and antimicrobial agents. Trovafloxacin inhibited 435 strains (99.3%) at < or =2 microg/ml. All the quinolones had similar activities against Enterobacteriaceae and Pseudomonas sp., but trovafloxacin showed superior activities against streptococci, enterococci, and anaerobic organisms. Because of its excellent in vitro activities against diverse bacteria, trovafloxacin has potential use as a single agent for polymicrobial infections.     

Activities of synthetic hybrid peptides against anaerobic bacteria: aspects of methodology and stability

The increasing problem of antibiotic resistance among pathogenic bacteria requires development of new antimicrobial agents. One line of investigation is the synthesis of antimicrobial hybrid peptides. The aim of the present investigation was to determine the in vitro activities of 16 cecropin-melittin hybrid peptides (CAMEL analogues) against 60 anaerobic bacterial strains, to compare their activities with those of seven clinically used antimicrobial agents, and to compare different methods for anaerobic susceptibility testing of these peptides. The stability of one of the peptides, temporin B, with different stereoisomeric configurations was investigated in a fecal milieu. The CAMEL analogues showed antimicrobial activity against the anaerobic bacteria, with MICs ranging from 0.125 to 32 microg/ml. The overall activities (the MICs at which 90% of isolates are inhibited) of the CAMEL analogues against anaerobic bacteria were mainly inferior to those of imipenem, clindamycin, and piperacillin but were equal to or superior to those of metronidazole, cefoxitin, ciprofloxacin, and chloramphenicol. The agarose dilution method was found to be an accurate method for the testing of large numbers of bacterial strains. The D isomer of temporin B was inactivated more slowly in feces than the L isomer. This study shows that the CAMEL analogues are potential agents for the treatment of anaerobic infections.     

Susceptibilities of genital mycoplasmas to the newer quinolones as determined by the agar dilution method.

The increasing resistance of genital mycoplasmas to tetracycline poses a problem because tetracycline is one of the few antimicrobial agents active against Mycoplasma hominis, Ureaplasma urealyticum, chlamydiae, gonococci, and other agents of genitourinary-tract disease. Since the quinolones are a promising group of antimicrobial agents, the susceptibilities of M. hominis and U. urealyticum to the newer 6-fluoroquinolones were determined by the agar dilution method. Ciprofloxacin, difloxacin, and ofloxacin had good activity against M. hominis, with the MIC for 50% of isolates tested (MIC50) being 1 microgram/ml. Fleroxacin, lomefloxacin, pefloxacin, and rosoxacin had MIC50s of 2 micrograms/ml. Enoxacin, norfloxacin, and amifloxacin had MIC50s of 8 to 16 micrograms/ml, and cinoxacin and nalidixic acid were inactive (MIC50, greater than or equal to 256 micrograms/ml). Overall, the activities of 6-fluoroquinolones for ureaplasmas were similar to those for M. hominis, with MICs being the same or twofold greater. The most active 6-fluoroquinolones against ureaplasmas were difloxacin, ofloxacin, and pefloxacin, with MIC50s of 1 to 2 micrograms/ml. Ciprofloxacin was unusual in that the MIC50 for M. hominis was 1 microgram/ml, whereas the MIC50 for ureaplasmas was 8 micrograms/ml. Since the MIC50s for the most active quinolones approximate achievable concentrations in blood and urine, quinolones have promise in treating mycoplasmal infections.