Μg Streptomycin Research Articles

Lysophosphatidic Acid (LPA) Protects Primary Chronic Lymphocytic Leukemia Cells from Apoptosis through LPA Receptor Activation of the Anti-apoptotic Protein AKT/PKB

Lysophosphatidic acid (LPA) protects epithelial and fibroblast cell lines from apoptosis. In B-cells, LPA acts as a growth factor promoting cell proliferation. Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of CD19+/CD5+ B-lymphocytes primarily through a block in apoptosis. The mechanisms underlying this defect are not fully understood. We investigated whether LPA could be a survival factor in CLL cells. Herein, we demonstrate that LPA protects B-cell lines BJAB and I-83 and primary CLL cells but not normal B-cells from fludarabine- and etoposide-induced apoptosis. Furthermore, LPA prevented spontaneous apoptosis in primary CLL cells. The LPA1 expression was found to be increased in primary CLL cells compared with normal B-cells correlating with LPA prevention of apoptosis. Treatment of primary CLL cells with the LPA receptor antagonist, diacylglycerol pyrophosphate, reverses the protective effect of LPA against apoptosis, and down-regulation of the LPA1 by siRNA blocked LPA-mediated protection against spontaneous apoptosis in primary CLL cells. The protective effect of LPA was inhibited by blocking activation of the phosphatidylinositol 3-kinase/AKT signaling pathway. These results indicate that LPA is a survival factor in B-cell lines and primary CLL cells but not normal B-cells. Thus, drugs targeting the LPA receptors might be an effective therapy against B-cell-derived malignancies such as CLL.

Gene expression of fibroblasts following light irradiation

Gene expression of fibroblasts following light irradiation

Endophytic fungi from Musa acuminata leaves and roots in South China

One hundred and sixty-three endophytic fungal cultures were isolated from 200 leaf samples of Musa acuminata trees, which were soaked in 36% formaldehyde solution for surface sterilization. They belonged to the genera of Gloeosporium musae (45%), Myxosporium spp. (11%), Deightoniella torulosa (8.5%), Alternaria tenuis (7.9%), Sphaceloma spp. (7.4%), Aureobasidium spp. (4.3%), Melida spp. (1.8%), Uncinula spp. (1.8%), Penicillium spp. (1.8%), Aspergillus spp. (1.2%), Sarcinella spp. (1.2%), Cladosporium sp. (0.6%), Cephalosporium sp. (0.6%) and sterile mycelium (6.7%). Sixty-eight endophytic fungal cultures were isolated from 100 root samples. They respectively belonged to the genera of Aspergillus spp. (31%), Paecilomyces spp. (16%), Penicillium spp. (15%), Fusarium spp. (10%), Gloeosporium musae (6%), yeast (3%), Deightoniella torulosa (3%), Spicaria sp. (1.4%), Cephalosporrium sp. (1.4%), Meliola sp. (1.4%) and sterile mycelium (10%). Water agar (containing 50 μg chloramphenicol ml−1 and 50 μg streptomycin ml−1) seemed to be a better medium for isolation of endophytic fungi than potato-dextrose agar (PDA, containing 50 μg chloramphenicol ml−1 and 50 μg streptomycin ml−1).

Effectiveness of once-weekly rifapentine and moxifloxacin regimens against Mycobacterium tuberculosis in mice.

Mice infected with 1.6 x 10(7) CFU of Mycobacterium tuberculosis were treated 14 days later for 6 months with a regimen of once-weekly 10 mg of rifapentine and 75 mg of isoniazid per kg of body weight supplemented with either 150 mg of streptomycin per kg or 100 mg of moxifloxacin per kg during either both the 2-week daily initial and once-weekly continuation phases or only in the daily 2-week initial phase. On completion of treatment, all lung cultures were negative, except for three mice, each with a single colony: two whose rifapentine-isoniazid regimen was supplemented with streptomycin during the whole course of therapy and one whose rifapentine-isoniazid regimen had no initial daily phase, but was supplemented with streptomycin and moxifloxacin during the whole course of therapy. After 3 months of follow-up, positive lung cultures were obtained from 61 and 56% of mice supplemented with streptomycin during either the full course of therapy or only the daily 2-week initial phase, respectively, and 15 and 50% of mice supplemented with moxifloxacin during either the full course of therapy or only the daily 2-week initial phase, respectively. These results suggest that moxifloxacin has sterilizing activity against M. tuberculosis.

Inhibition of Dendritic Cell Differentiation by Fumaric Acid Esters

Fumaric acid esters have proved to be effective for the systemic treatment of severe psoriasis vulgaris. These compounds have been shown to induce a Th2-like cytokine secretion pattern in T cells and to reduce keratinocyte proliferation in vitro. Dendritic cells seem to be of major importance as regulatory cells driving the psoriatic tissue reaction. Monocytes or CD34-positive myeloid progenitor cells are precursors of dendritic cells that can be generated in vitro by culture with granulocyte-macrophage colony-stimulating factor and interleukin-4. Using this model the effect of fumaric acid esters on granulocyte-macrophage colony-stimulating factor/interleukin-4-induced differentiation of monocyte-derived dendritic cells was investigated. The results of this study show that dimethylfumarate as well as methylhydrogenfumarate-calcium-salt (0.01-100 microg per ml) concentration-dependently inhibit monocyte-derived dendritic cell differentiation. This was reflected by an inhibition of CD1a, CD40, CD80, CD86, and HLA-DR expression as well as by a reduced capacity of dimethylfumarate-treated monocyte-derived dendritic cells to stimulate lymphocytes in the allogeneic mixed lymphocyte reaction. Other fumaric acid esters showed no effect on monocyte-derived dendritic cell-differentiation. At higher concentrations (30-100 microg per ml) dimethylfumarate, but not methylhydrogenfumarate calcium-salt induced apoptosis in monocyte-derived dendritic cells as measured by expression of Apo 2.7 and DNA fragmentation (TUNEL assay). These data point to a high susceptibility of the monocyte/dendritic cell system to dimethylfumarate and its main metabolite methylhydrogenfumarate. Other fumaric acid esters investigated were without effect. As the effects of fumarates on monocyte-derived dendritic cells observed occur at concentrations 20-fold lower compared with lymphocytes, our data seem to be of relevance in explaining the possible mode of action of these compounds in psoriasis.

Differential growth characteristics and streptomycin susceptibility of virulent and avirulent Mycobacterium tuberculosis strains in a novel fibroblast-mycobacterium microcolony assay.

The ability to spread from cell to cell may be an important virulence determinant of Mycobacterium tuberculosis. An in vitro assay was developed to characterize this ability among four strains of M. tuberculosis: the attenuated strain H37Ra, the virulent strains H37Rv and Erdman, and a virulent clinical isolate (Stew). Confluent monolayers of human skin fibroblasts were infected with these strains and overlaid with agar-medium. M. tuberculosis infection developed over 21 days as microcolonies originating within the plane of the fibroblasts. Microcolonies of the virulent strains had an elongated appearance and exhibited extensive cording. The cords appeared to invade adjacent cells within the plane of the monolayer. Microcolony diameter of the Erdman strain was significantly larger than that of the other virulent strains, indicating that virulent strains can have distinguishing phenotypes in this assay. In contrast, avirulent H37Ra microcolonies were rounded and noncorded. H37Ra microcolonies were significantly smaller than those of the virulent strains. Microcolony diameter of the virulent strains was not reduced by the extracellularly acting antibiotic streptomycin at concentrations of up to 5.0 microgram/ml. In contrast, H37Ra microcolony size was reduced at concentrations as low as 0.5 microgram/ml. Growth of all strains was similarly inhibited by 1.0 microgram of streptomycin per ml in fibroblast-conditioned tissue culture medium alone. When fibroblasts were infected with the M. tuberculosis strains without an agar overlay, with and without streptomycin, numbers of CFU mirrored the changes observed in the microcolony assay. There was a statistically significant decrease in H37Ra CFU compared to virulent strains after treatment with streptomycin. These differences between H37Ra and virulent strains in human fibroblasts suggest that H37Ra may be lacking a virulence determinant involved in cell-to-cell spread of M. tuberculosis.

Antimicrobial and antiinflammatory activities of extracts and constituents of Oroxylum indicum (L.) Vent

Dichloromethane extracts of the stembark and root of Oroxylum indicum were found to have antimicrobial activities against Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gramnegative bacteria (Escherichia coli and Pseudomonas aeruginosa) and a yeast (Candida albicans). Bioassay-guided chromatographic fractionation led to the isolation of flavonoids (bacailein and chrysin) and a naphthoquinone, lapachol. Lapachol was found active against the Gram-positive bacteria, 5 μg giving a zone of inhibition equivalent to that shown by 5 μg streptomycin, whereas 5 μg chrysin gave inhibition zones of equal size to 5 μg streptomycin against Candida albicans and Pseudomonas aeruginosa. The inhibitory activity of lapachol from O. indicum root against soya 5-lipoxygenase (IC(50) 0.79 μg/ml) was equivalent to that of the positive control fisetin (IC(50) 0.97 μg/ml) and 50 μg/ml of the dichloromethane extract of the rootbark gave 100% inhibition of leukocyte lipoxygenase. These activities might indicate an antiinflammatory effect for the dichloromethane extract, mainly due to the lapachol content.

Use of antibiotics to inhibit non-starter lactic acid bacteria in Cheddar cheese

The efficacy of Nisin, Penicillin G and Streptomycin at inhibiting the growth of the non-starter lactic acid bacteria (NSLAB) in Cheddar cheese was studied in cheeses treated with an antibiotic-salt mixture after milling. Nisin (500 U g −1 curd) and particularly Streptomycin (12 μg g −1 curd) did not effectively inhibit NSLAB. Penicillin G (12 U g −1 curd) reduced NSLAB numbers but mixtures of antibiotics (250 U Nisin, 6 U Penicillin G, 6 μg Streptomycin g −1 curd or 500 U Nisin, 12 U Penicillin G, 12 βg Streptomycin g −1 curd) were more effective than any individual antibiotic. The higher level antibiotic mixture reduced NSLAB populations by 4–5 log cycles compared with the control after 100–160 days. Viable starter numbers (after 35 days) were not affected by the antibiotic treatments. Antibiotic-treated cheeses contained higher levels of free amino acids but no differences between the cheeses were indicated by urea—polyacrylamide gel electrophoresis or reverse-phase HPLC.

Evaluation of Culture Techniques for Isolation of Pseudomonas pseudomallei from Soil

Three selective enrichment broths and four selective agar media were evaluated for their ability to support the growth of Pseudomonas pseudomallei both at 35 degrees C and at ambient temperature (range, 20 to 32 degrees C; mean, 25 degrees C). Colony counts of 50 strains of P. pseudomallei and recovery studies with 1 soil strain in 60 simulated soil samples demonstrated that enrichment with Trypticase soy broth incorporating 5 mg of crystal violet per liter and 20 mg of colistin per liter (CVCB) and subculture to Ashdown medium supported the growth of all 50 strains and produced the highest recovery rates with the greatest suppression of other soil flora. An enrichment broth of MacConkey broth (purple) incorporating 10 mg of crystal violet per liter, 5 mg of bromcresol purple per liter, 25 mg of gentamicin per liter, and 650 mg of streptomycin per liter showed greater suppression of soil bacteria than CVCB, but it failed to support the growth of three strains of P. pseudomallei. Recovery rates were essentially the same irrespective of whether the soil samples were incubated at 35 degrees C or at ambient temperature, provided cultures were incubated in protected shade for an extended period. This is an important feature for field work in large-scale epidemiological surveys in which resources are limited.

A murine model of chronic mucosal colonization by Pseudomonas aeruginosa.

Chronic mucosal colonization by Pseudomonas aeruginosa is an integral part of the pathologic process associated with disease due to infection with this organism. We have adapted the streptomycin-treated murine model of chronic mucosal colonization by enteric pathogens to study colonization by P. aeruginosa. Mice first received 1 mg of streptomycin per ml of drinking water for 2 to 5 days and then ingested 10(7) CFU of P. aeruginosa per ml of drinking water for a minimum of 5 days. The result of this regimen was chronic mucosal colonization with P. aeruginosa for up to 10 weeks, which was determined by fecal cultures and confirmed by culture of the intestines after killing of the experimental animals. Bacterial counts were highest in the cecum and colon, with some evidence for extraintestinal bacterial translocation as well. Use of P. aeruginosa mutants deficient in the production of colonization factors such as pili and those dependent on the rpoN gene product resulted in a lower level of chronic colonization. Immune responses to type-specific lipopolysaccharide, pili, and flagellar antigens were measured, and increases in both serum and intestinal antibodies were usually elicited when a strain elaborated a given antigen. This model represents an easy method of routinely achieving chronic mucosal colonization by P. aeruginosa and should prove useful for the study of both bacterial virulence factors and host responses associated with this infectious process.

Growth, competitiveness and effectiveness of spontaneous antibiotic resistant strains of Bradyrhizobium for Desmodium intortum CV greenleaf

Spontaneous antibiotic-resistant strains of Bradyrhizobium, from six parent strains isolated from Desmodium intortum, were compared with their parents for changes in ecologically-important characteristics. Strains resistant to 30 μ g rifampicin ml −1 and 500 μg streptomycin ml −1 were serologically homologous with their parents in gel-immunodiffusion tests against antisera for the parent strains. They had similar growth and rhizosphere colonizing abilities, but were not equally effective in N 2 fixation or equally competitive for nodule formation on D. intortum. Such variation suggests, firstly that a single colony isolate should not be used to represent a parent strain. Secondly, if single colony isolates are used they should be considered as strains for their individual characteristics.

Chronic Mastitis Caused by Candida maltosa in a Cow

In general, bovine mastitis due to candidial infection is acute or transitory, and recovery is spon taneo~s .~ .~ Various species of Candida have been isolated from cases of bovine mastitis; however, the relationship between lesions and Candida is unknown. Although Sutka6 isolated Candida guilliermondii from clinically chronic mastitis of cows, the lesions associated with the fungus were acute. This study describes the pathologic findings of chronic mastitis caused by Candida maltosa in a 5Ih-year-old Holstein-Friesian cow. After parturition, the cow retained the placenta, which could not be removed. She had a fever (40.0-40.5 C) from 6 days after parturition and was affected with mastitis within 1 week. The cow was treated with an intramuscular injection of 19,100,000 units of penicillin and 100 international units (IU) of oxytocin and intramammary infusion of 1,500 mg of streptomycin and 800,000 units of nystatin. The mastitis was characterized by swelling and induration but involved only one quarter of the udder. This mastitis was progressive. Because the treatment had no apparent effect, she was euthanatized 24 days after parturition. Samples of the affected quarter of the mammary gland and the supramammary lymph node were removed, fixed in 10% neutral buffered formalin, and forwarded to our department. The cut surface of the gland had multiple, small (0.8 mm in diameter) to large (1 .O cm in diameter), irregular necrotic foci surrounded with granulation tissue. The supramammary lymph node was markedly enlarged (approximately three times normal). Only C. maltosa was isolated on the microbiologic examination of the milk collected 4 days after the onset of fever (1 4 days before necropsy). The species was identified on the basis of the following morphologic and growth characteristics:' 1) the absence of true hyphae chlamydoconidia, arthroconidia, and ascospores, the presence of pseudohyphae, and the fermentation of D-glucose and sucrose; 2) grew when the following were added to the media: D-galactose, succinate, 50% sucrose, maltose, aptrehalose, L-sorbose, D-mannitol, glycerol, citrate, melezitose, D-xylose, ribitol, DL-lactate, and 2-keto-D-gluconate; 3) did not grow when the following were added to the media: cellobiose, melibiose, L-rhamnose, galactitol, erythritol, D-arabinose, raffinose, D-ribose, 60% sucrose, lactose, myo-inositol, and L-arabinose; 4) grew in vitamin-free media and did not grow at 42 C or when 0.1% cycloheximide was added to the media; and 5 ) did not hydrolyze urea, assimilate potassium, or grow in dextrose-yeast peptone water. Histologically, mammary lesions were divided into two types: extensive suppurative inflammation with necrosis, and giant cell formation. In the former lesions, numerous fungal elements in the central areas of necrotic foci were surrounded by numerous neutrophils and granulation tissue (Fig. I). In the latter lesions, many giant cells were observed within involved alveoli and intralobular ducts. The giant cells had engulfed fungal elements (Fig. 2) that occasionally were degenerative. The basement membrane of the involved alveoli and ducts was intact in the initial lesions, while it was destroyed in the advanced ones. These findings suggest that the fungi invaded intraductally.

The use of streptomycin to induce unilateral ablation of vestibular function in the rat: A preliminary report

The goal of our research is to develop a method of applying streptomycin to the middle ear so as to destroy vestibular function unilaterally while avoiding damage to auditory function. In this preliminary experiment, a total of 42 mg of streptomycin was infused continuously over a seven-day period into one middle ear cavity of seven rats, with the opposite ear serving as a control. Histologic study revealed a moderate to severe degree of vestibular neuroepithelial damage in all of the infused ears. However, significant damage also occurred in the basal turn of the cochlea in a majority of cases.

Effectivity of indigenous rhizobia for nodulation and early nitrogen fixation with Leucaena leucocephala grown in nigerian soils

Rhizobium strains isolated from Leucaena leucocephala. Sesbania rostrata, S. grandiflora, S. punctata, Tephrosia vogelii. Acacia albida and Vigna unguiculata growing in Nigerian soils were characterized and tested for their ability to nodulate and fix atmospheric nitrogen with L. leucocephala. Isolates from L. leucocephala, S. rostrata. S. grandiflora and S. punctata were fast-growing and acid producers whereas those from A. albida, T. vogelii and V. unguiculata were slow-growing and alkali producers. Some of these isolates grew in the presence of 500 μg streptomycin ml −1. The effectivity of the rhizobia isolates on L. leucocephala was tested in Leonard jars. Isolates from all plant species except those from S. grandiflora and V. unguiculata nodulated L. leucocephala but a wide range of effectiveness was observed. Based on this experiment the ten most promising rhizobia were screened for effectiveness in potted soils collected at IITA, Ibadan (transition forest savanna), and at Fashola (savanna, 70 km north of IITA). Establishment of L. leucocephala was poor in soils without previous history of L. leucocephala cultivation due to the presence of only few native leucaena rhizobia (< 1000 g −1 soil). Rhizobium isolates IRc 1045 and IRc 1050 obtained from L. leucocephala grown at Fashola and IITA were found to be the most effective rhizobia on this host. In addition to their effectiveness and competitiveness they survived well in the field 1 year after their establishment.

Treatment of experimental salmonellosis in mice with streptomycin entrapped in liposomes.

Liposome-entrapped streptomycin (SM) was compared with free SM for therapeutic efficacy against experimental salmonellosis in mice. All of the mice infected with the virulent strain of Salmonella enteritidis 116-54 died between days 5 and 7, and a dose of 20 mg of free SM per kg administered 24 h after the bacterial inoculation did not prolong the survival. In contrast, the same dose of SM entrapped in liposomes prolonged paralleled the dose in the liposomes, and a dose as low as 1.2 mg of SM per kg in liposomes prolonged the survival. The advantage of using liposomes was more pronounced when a larger dose of SM was employed. The liposome-entrapped drug was less toxic than the free drug. A dose of 80 mg of free SM per kg caused convulsions, but the same dose entrapped in liposomes caused no side effects. Furthermore, two doses of liposome-entrapped SM further enhanced the therapeutic effect. The efficacy of the liposome-entrapped drug was still observed in mice infected with a large inoculum of S. enteritidis. A tissue distribution study on SM in various organs demonstrated that liposomal SM was selectively delivered to the spleen and liver with concentrations in these those in mice receiving the free drug. The prolongation of survival was due to suppression of the multiplication of S. enteritidis as demonstrated by viable cell counts in the spleens.

Survival of Pseudomonas solanacearum biovars 2 and 3 in soil: Effect of moisture and soil type

The survival of Pseudomonas solanacearum biovars 2 and 3 in three soils, a Nambour clay loam, a Beerwah sandy loam and a Redland Bay clay, was compared at pressure potentials of −0.003, −0.05 and −0.15 kPa. The soils were inoculated with mutants of P. solanacearum biovars 2 and 3, resistant to 2000 μg streptomycin sulphate ml −1 and their survival measured every 6 weeks for 86 weeks in the clay loam and clay and for 52 weeks in the sandy loam. Soil populations declined with the initial drying necessary to bring the soil moisture to the specific pressure potentials; the initial counts for biovar 2 varied between 0.20 and 2.00 × 10 9 cfu g −1 soil and for biovar 3 between 0.17 and 1.29 × 10 9 cfu g −1 soil. The population decline in soil maintained at a constant pressure potential was expressed as the rate of population decline. Biovar 2 declined more rapidly than biovar 3. The rate of population decline of each biovar at −0.003 and −0.05 kPa was greater in clay loam than in sandy loam and at all pressure potentials it was greater in clay loam and sandy loam than in clay. There was also a tendency for the rate of population decline of both biovars to decrease in the drier soil treatments.

Short-term storage and cryopreservation of milt from Atlantic salmon and sea trout

Experiments on short-term preservation of sperm were performed with Atlantic salmon ( Salmo salar). Fertility was maintained for up to 10 days when 2 mm thick samples were stored at 0° C under an oxygen atmosphere in the presence of antibiotics (125 IU penicillin and 125 μg streptomycin per ml sperm). Fertility was completely lost after 24 days. Sperm stored without antibiotics fertilized 100% of eggs after 6 days. Cryopreservation was carried out with milt from Atlantic salmon and sea trout ( Salmo trutta). Semen mixed with extender was frozen on dry ice (pellets) with subsequent storage in liquid nitrogen. Sperm pellets were thawed in a 0.12-M NaHCO 3-solution (10° C) before insemination. The suitability of an extender as previously described by Stoss and Holtz and of a 0.3-M glucose solution with the addition of 10% DMSO, was tested on two different batches of sperm and eggs in Atlantic salmon and sea trout. In addition, the extender earlier reported by Mounib and an aqueous solution of 10% DMSO were only used in Atlantic salmon with one batch of gametes. Insemination with cryopreserved Atlantic salmon sperm resulted in 36 to 91.3% eyed eggs (control = 100). The differences were caused by the type of extender and the batch of gametes employed. The very simple extender consisting of 0.3 M glucose and 10% DMSO only was the most successful. Results with cryopreserved sea trout sperm ranged between 38.6–54.8% eyed eggs, showing no difference between treatments.

Effects of Streptomycin on the Growth and Sporulation of Saprolegnia spp.

Summary: Streptomycin inhibited growth and sporulation of Saprolegnia species, although variations in sensitivity were recorded. In sporulating colonies, streptomycin increased both the length of the post-induction lag phase and the proportion of gemmae. Antibiotic concentrations (> 100 μg ml−1) which resulted in the leakage of potassium ions from sporulating colonies also correlated with the condensation of hyphal cytoplasm into lysed segments. In vegetative colonies grown in > 500 μg streptomycin ml−1, changes were seen in the organization of endoplasmic reticulum, mitochondria and nuclei. These inhibitory effects could be counteracted by the addition of calcium ions. Some observed effects were consistent with an impairment of normal mitochondrial function, but others, particularly in sporulating colonies, were possibly the result of interference with cellular functions regulated by calcium or other divalent cations.

Analysis of a new mutant from Euglena gracilis resistant to streptomycin

We analysed a new mutant resistant to streptomycin, Sm 2 rBNgL (Sm 2). This mutant was resistant to 5 mg of streptomycin (STR) per ml when grown on solid organotrophic medium. Chlorophyll synthesis, photosynthetic carbon dioxide fixation and oxygen evolution were normal when dark-grown resting mutant cultures, containing 0.3 mg of streptomycin per ml, were transferred to t he light. The 32S small chloroplast ribosomal suunits extracted from this mutant lost their affinity for dihydrostreptomycin. Finally, comparison between electrophoretograms obtained with chloroplast ribosomal proteins extracted from wild-type and mutant suggested that one acidic protein of the 32S small ribosomal subunit might be modified. Results presented here and those obtained with another Euglena mutant resistant to streptomycin, Sm 1 rBNgL (Sm 1), (Freyssinet, Plant Sci. Lett. 5 (1875) 305) suggest that the streptomycin binding site is located in the unstable region of the 32S small chloroplast ribosomal subunits of Euglena.

Antibiotic Susceptibility of Haemophilus vaginalis (Corynebacterium vaginale) to 21 Antibiotics

A total of 56 strains of Haemophilus vaginalis were tested for their in vitro susceptibility to 21 antimicrobial agents by an agar dilution method. All strains were inhibited by 1 mug or less of penicillin, ampicillin, carbenicillin, and vancomycin per ml. The cephalosporins were less active; 4 mug of cefazolin per ml, 16 mug of cephalothin per ml, or 128 mug of cephalexin per ml was required to inhibit all strains. Kanamycin, gentamicin, tobramycin, and neomycin were relatively inactive against H. vaginalis. All strains were inhibited by 4 mug of streptomycin per ml and 2 mug of chloramphenicol per ml. Only 57% of the strains were inhibited by 4 mug of tetracycline per ml, whereas 43% were inhibited by 16 to 64 mug/ml. The combination sulfamethoxazole/trimethoprim was relatively inactive against H. vaginalis. All strains tested exhibited minimal inhibitory concentrations of >/=128 mug when tested against colistin, nalidixic acid, and sulfadiazine. Erythromycin and clindamycin were the most active of the antibiotics tested; for all strains the minimal inhibitory concentrations were </=0.06 mug/ml.