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PubMed1989

Slide culture sensitivity tests.

A new method for slide culture sensitivity tests of Mycobacterium tuberculosis is described in which smear-positive sputum spread on slides is incubated without prior decontamination in a selective lysed human blood medium. Results are available 7 days after setting up the tests and are particularly useful for guiding the treatment of smear-positive patients with a long history of unsuccessful chemotherapy. Drug concentrations and definitions of resistance are suggested for tests against isoniazid, streptomycin, PAS, rifampicin ethambutol and ethionamide. A good correlation was seen between the results of these tests and those of standard indirect sensitivity tests.

Antitubercular Agents↗
PubMedDate not supplied

[Antibiogram of bacteria of the Clostridium genus].

The disc-agar diffusion method for antibiotic sensitivity testing was adapted to Clostridium. The main feature of the method described here resided in the use of an inoculum which varied according to the physiological properties of the strain tested, so that the same critical time was obtained in all cases. This technique employs commercially available media and reduced equipment. Statistical analysis of the results indicated a strong correlation between disc-agar sensitivity testing and MIC determined by the agar dilution method.

Agar↗
PubMed1978

[Stability of MIC values from tetracyclines in different media (author's transl)].

The influence of nutrient-broth (NB), Mueller-Hinton-broth (MHB), isotonic-sensitive-broth (ISB) and tryptone-soya-broth (TSB) with respect to the determination of MIC values of three tetracyclines is shown. A difference of degradation of tetracycline derivates in the four media was found. The degradation in NB after 18 h was negligible, but in MHB after 18 h all the three tetracyclines were inactivated up to 42%. The MIC levels of staphylococcus aureus strains in NB were about twofold lower than those in MHB and TSB. The MIC levels in ISB were even three- to fourfold higher than in NB. From these results sensitivity testing of tetracycline derivates should be carried out with NB.

Culture Media↗
PubMed2005

Molecular diagnostics in tuberculosis.

Molecular diagnostics in tuberculosis has enabled rapid detection of Mycobacterium tuberculosis complex in clinical specimens, identification of mycobacterial species, detection of drug resistance, and typing for epidemiological investigation. In the laboratory diagnosis of tuberculosis, the nucleic acid amplification (NAA) test is rapid and specific but not as sensitive as culture of mycobacteria. The primary determinant of successful NAA testing for tuberculosis depends on the shedding of mycobacterial DNA in secretions from caseating granulomas and its dissemination into sterile body fluids or tissue biopsies. In multibacillary diseases with a high mycobacterial load, a positive Ziehl-Neelsen smear with a positive NAA test is diagnostic of active tuberculosis, whereas a positive Ziehl-Neelsen smear with a negative NAA test in the absence of inhibitors would indicate nontuberculous mycobacterial disease. The role of the NAA test is more important in paucibacillary diseases with low mycobacterial loads. The presence of polymerase chain reaction (PCR) inhibitors, however, especially in extrapulmonary specimens, may produce false-negative results. Although this problem can be overcome to some extent by extra extraction steps, the additional processing invariably leads to the loss of mycobacterial DNA. To circumvent this problem, a brief culture augmentation step is carried out before the NAA test is performed, which can enhance the mycobacterial load while concomitantly diluting inhibitors, thereby maintaining the sensitivity of the test without excessively increasing turnaround time.

Microbial Sensitivity Tests↗
PubMed2000

Analysis of rdxA and involvement of additional genes encoding NAD(P)H flavin oxidoreductase (FrxA) and ferredoxin-like protein (FdxB) in metronidazole resistance of Helicobacter pylori.

Metronidazole (Mtz) is a critical ingredient of modern multidrug therapies for Helicobacter pylori infection. Mtz resistance reduces the effectiveness of these combinations. Although null mutations in a rdxA gene that encodes oxygen-insensitive NAD(P)H nitroreductase was reported in Mtz-resistant H. pylori, an intact rdxA gene has also been reported in Mtz-resistant H. pylori, suggesting that additional Mtz resistance mechanisms exist in H. pylori. We explored the nature of Mtz resistance among 544 clinical H. pylori isolates to clarify the role of rdxA inactivation in Mtz resistance and to identify another gene(s) responsible for Mtz resistance in H. pylori. Mtz resistance was present in 33% (181 of 544) of the clinical isolates. There was marked heterogeneity of resistance, with Mtz MICs ranging from 8 to >/=256 microg/ml. rdxA inactivation resulted in Mtz MICs of up to 32 microg/ml for 6 Mtz-sensitive H. pylori strains and 128 microg/ml for one Mtz-sensitive strain. Single or dual (with rdxA) inactivation of genes that encode ferredoxin-like protein (designated fdxB) and NAD(P)H flavin oxidoreductase (frxA) also increased the MICs of Mtz for sensitive and resistant strains with low to moderate levels of Mtz resistance. fdxB inactivation resulted in a lower level of resistance than that from rdxA inactivation, whereas frxA inactivation resulted in MICs similar to those seen with rdxA inactivation. Further evidence for involvement of the frxA gene in Mtz resistance included the finding of a naturally inactivated frxA but an intact rdxA in an Mtz-resistant strain, complementation of Mtz sensitivity from an Mtz-sensitive strain to an Mtz-resistant strain or vice versa by use of naturally inactivated or functional frxA genes, respectively, and transformation of an Mtz-resistant Escherichia coli strain to an Mtz sensitive strain by a naturally functional frxA gene but not an inactivated frxA gene. These results are consistent with the hypothesis that null mutations in fdxB, frxA, or rdxA may be involved in Mtz resistance.

Amino Acid Sequence↗
PubMed1999

Characterization of virulence factors of Aeromonas isolated from children with and without diarrhoea in Tripoli, Libya.

During September 1992-August 1993, stool samples from 157 children with diarrhoea and 157 matched healthy controls were examined for the presence of Aeromonas and other enteropathogens. Aeromonas strains were tested for haemolytic activity, haemagglutination patterns, and antibiotic susceptibility. In total, 62 Aeromonas were isolated, of which 27 (17.2%) were from children with diarrhoea and 35 (22.3%) from healthy controls. Only 23 (14.6%) of the diarrhoeal children and 28 (17.8%) of the healthy controls were positive for Aeromonas; of which, 4 (2.5%) of the diarrhoeal children and 6 (3.8%) of the healthy controls showed multiple species. Aeromonas hydrophila was isolated from 5 (3.2%) children with diarrhoea and from 9 (6.4%) controls, A. veronii bv sobria from 8 (5.1%) and 7 (4.5%), A. caviae from 13 (8.3%) and 17 (10.8%), and A. schubertii from 1 (0.6%) and 2 (1.3%) respectively. No significant difference in the haemolytic activity of Aeromonas was found between diarrhoeal and healthy children. However, a significant difference (p < 0.002) was observed in mannose-resistant haemagglutination (MRHA) by diarrhoeal isolates of Aeromonas (7/27, 26%) compared to the healthy controls (1/35, 3%). Aeromonas strains were uniformly sensitive to ciprofloxacin, gentamicin, and nalidixic acid. The results of this study suggest that A. caviae strains may be associated with diarrhoea in children and MRHA may be used as one of the virulence markers for distinguishing between Aeromonas isolated from diarrhoeal children and healthy controls or environmental isolates.

Aeromonas↗
PubMed1985

Isolation and biological activities of limulus anticoagulant (anti-LPS factor) which interacts with lipopolysaccharide (LPS).

Exposure of limulus hemocytes to bacterial endotoxins (lipopolysaccharide, LPS) results in the activation of the intracellular clotting system, consisting of several protein components. During the separation of these components, a potent anticoagulant, named anti-LPS factor, which inhibits the endotoxin-mediated activation of the coagulation cascade, was found in hemocytes from both Tachypleus tridentatus and Limulus polyphemus (Tanaka, S., et al. (1982) Biochem. Biophys. Res. Commun. 105, 717-723). The principle isolated from the Tachypleus hemocyte lysate by column chromatographies on dextran sulfate-Sepharose CL-6B and Sephadex G-50 under sterile conditions was a simple basic protein with an apparent molecular weight of 15,000. It consisted of a single chain polypeptide containing a total of 128 amino acids. The COOH-terminal end was presumed to be histidine, but no NH2-terminal end reactive to phenylisothiocyanate was detected. The isolated anti-LPS factor specifically inhibited the endotoxin-mediated activation of factor C, which has recently been identified as an LPS-sensitive serine protease zymogen in the hemocytes. This inhibition appeared to be due to the binding of anti-LPS factor with LPS. Moreover, anti-LPS factor had an antibacterial effect on the growth of Gram-negative bacteria (Salmonella minnesota R595 and 1114W) but not on that of Gram-positive bacteria (Staphylococcus aureus 209P). These biological activities of the isolated anti-LPS factor suggest an important role in cellular defence of limulus against microbial invasion.

Amino Acids↗
PubMed1976

[Studies on the antibacterial activity of the combination sulfamoxole/trimethoprim (CN 3123) (author's transl)].

After giving a survey on the situation of antibiotic resistance in the region of Northern Bavaria during 1973/74 and comparing the activity of a sulfamethoxazole (SMZ) trimethoprim (TMP) combination to other commonly used antibiotics and chemotherapeutic agents, the results of tests with the new combination of N1-(4,5-dimethyl-2-oxazolyl)-sulfanilamide) (sulfamoxole) and 2,4-diamino-5-(3,4,5-trimethoxy-benzyl)-pyrimidine (trimethoprim) at a ratio of 5:1 (CN 3123; Nevin, Supristol) are compared to those of tests with TMP/SMZ. This was done by correlating the inhibition zone diameters and, on the other hand, by referring to a great number of sensitivity evaluations in routine diagnostic tests. According to the size of the inhibition zone, CN 3123 showed a somewhat greater activity on Enterococcus (fecal streptococci), Escherichia coli, and Klebsiella aerogenes, whereas the TPM/SMZ combination had apparently a stronger antibacterial effect in vitro against Proteus mirabilis, Staphylococcus aureus, and the Achromobacter-group. Analysis of sensitivity readings from routine diagnosis demonstrated accordance of CN 3123 with TMP/SMZ in 92.6% (first series) and 94.2% (second series), respectively. These results should be considered critically in view of the manifold factors which influence sensitivity tests in the agar diffusion method.

Anti-Bacterial Agents↗
PubMed1985

Bacterial antigen detection in cerebrospinal fluid of patients with meningitis.

This study compared the sensitivity and specificity of four test systems in detecting Haemophilus influenzae type b, Neisseria meningitidis, Streptococcus pneumoniae, and gram-negative organisms in cerebrospinal fluid (CSF), versus culture. The tests used on CSF from 155 patients with meningitis were the Phadebact coagglutination (CoA) test, the Directigen latex agglutination (LA) test, counterimmunoelectrophoresis (CIE), and the Limulus amebocyte lysate (LAL) test. The sensitivity for patients with bacterial meningitis was 78% (18/23) for LA, 78% (25/32) for CoA, and 67% (18/27) for CIE for detection of H. influenzae type b; 71% (10/14) for CoA, 100% (6/6) for LA, and 50% (6/13) for CIE in detecting S. pneumoniae; and 33% (1/3) for LA and 50% (2/4) for CIE in detecting N. meningitidis. LAL had a sensitivity of 77% (37/48) in detecting CSF gram-negative endotoxin. The specificities of those with bacterial meningitis for H. influenzae, S. pneumoniae, and N. meningitidis tested by LA were, respectively, 100% (35/35), 96% (50/52), and 100% (54/54); for H. influenzae and S. pneumoniae using CoA 97% (62/64) and 96% (80/83); for H. influenzae, S. pneumoniae, and N. meningitidis using CIE 67% (18/27), 50% (6/12), and 50% (2/4). The specificity of LAL was 86% (38/44). The detection of bacterial antigen from CSF in patients with meningitis by commercial agglutination tests is more sensitive than CIE and is highly specific.

Agglutination Tests↗
PubMed1978

Comparative in vitro activity of five nitrofurans.

Five nitrofurans- nitrofurantoin, nifuratel, nitrofurazone, furazolidone and and SQ 18,506--have been tested against 201 microbial strains. Escherichia coli, Streptococcus faecalis, micrococci and Staphylococcus epidermidis were sensitive to all five compounds; furazolidone and SQ 18,506 were the most active against these species. Klebsiella aerogenes was less sensitive, and Proteus spp., Providencia stuartii and Pseudomonas aeruginosa strains were resistant. Nifuratel was inhibitory for some Candida albicans strains, and SQ 18,506 was highly active against this species. Nifuratel was judged overall to have superior in vitro antimicrobial properties to nitrofurantoin.

Bacteria↗