Radiometric macrophage culture assay for rapid evaluation of antileprosy activity of rifampin.

The antileprosy effect of rifampin was evaluated by a newly developed rapid in vitro assay wherein 31 human-derived strains and 1 armadillo-derived strain of Mycobacterium leprae were maintained for 2 and 3 weeks, respectively, in murine and human macrophages in the presence of [3H]thymidine. Of these strains, 27 showed significant incorporation of the radiolabel in cultures of live bacilli as compared with control cultures of heat-killed bacilli of the same strain. Consistent and significant inhibition of [3H]thymidine uptake was observed in M. leprae resident cultures with 3 to 200 ng of rifampin per ml as compared with similar cultures without the drug. In general, an increase in percent inhibition was seen from 3 to 20 ng/ml, with marginal increases at 40, 50, and 100 ng/ml. M. leprae strains appear to be remarkably susceptible to this drug in the in vitro assay.     

Defective production of monocyte-activating cytokines in lepromatous leprosy

We have examined the capacity of monocytes from patients with leprosy to undergo activation and the capacity of mononuclear cells from these patients to incorporate [3H]thymidine and produce monocyte-activating cytokines. Monocytes from patients with either lepromatous or tuberculoid leprosy were activated by concanavalin A (Con A)-induced mononuclear cell supernatants generated from the leukocytes of a normal person. Monocytes activated by these supernatants strongly inhibited L. pneumophila multiplication, and the degree of inhibition was comparable in both groups of patients. Mononuclear cells from patients with either form of leprosy responded comparably to Con A with vigorous [3H]thymidine incorporation. Mononuclear cells from patients with tuberculoid leprosy also vigorously incorporated [3H]thymidine in response to M. leprae antigens. In contrast, mononuclear cells from patients with lepromatous leprosy did not exhibit significant [3H]thymidine incorporation in response to M. leprae antigens. The capacity of mononuclear cells to generate monocyte-activating cytokines generally paralleled their capacity to incorporate [3H]thymidine in response to Con A and M. leprae. Mononuclear cells from patients with either form of leprosy responded to Con A with the production of cytokines (supernatants) able to activate normal monocytes, expressed by inhibition of L. pneumophila multiplication. However Con A-induced supernatants from patients with lepromatous leprosy were less potent than Con A-induced supernatants from patients with tuberculoid leprosy. Mononuclear cells from patients with tuberculoid leprosy responded to M. leprae antigens with the production of potent monocyte-activating supernatants. In contrast, mononuclear cells from patients with lepromatous leprosy did not produce monocyte-activating cytokines in response to M. leprae antigens. These studies support the hypothesis that the immunological defect in lepromatous leprosy results from a failure to activate mononuclear phagocytes rather than from an intrinsic inability of these cells to be activated. We suggest that the failure to activate mononuclear phagocytes stems from defective production of monocyte-activating cytokines in response to M. leprae antigens.     

Susceptibility of Haemophilus influenzae Isolates from Blood and Cerebrospinal Fluid to Ampicillin, Chloramphenicol, and Trimethoprim-Sulfamethoxazole

Susceptibility to ampicillin and chloramphenicol in vitro has been determined for Haemophilus influenzae strains isolated from blood and/or cerebrospinal fluid cultures of patients admitted to two Atlanta hospitals from 1 January 1974 to 31 March 1975. Since the appearance of ampicillin-resistant strains of this organism in early 1974, chloramphenicol has been used in these hospitals as initial therapy for severe infection due to H. influenzae. Strains from five of 94 patients were resistant to ampicillin (minimum inhibitory concentration [MIC] >/= 12.5 mug/ml), but all strains were susceptible to chloramphenicol (MIC < 2 mug/ml). The first 35 strains studied, including three resistant to ampicillin, were also tested for in vitro susceptibility to trimethoprim-sulfamethoxazole; all were highly susceptible (MIC 相似文献   

Susceptibility of Mycobacterium leprae to Dapsone as a Determinant of Patient Response to Acedapsone

In the course of a clinical trial of acedapsone therapy in 17 patients with lepromatous leprosy, the rate of response to therapy was measured by inoculation of mice with Mycobacterium leprae recovered from biopsy specimens of skin lesions obtained before treatment and at intervals of 4, 12, and 24 weeks after institution of treatment. The susceptibility of each isolate of M. leprae to dapsone (4,4′-diaminodiphenylsulfone [DDS]) was measured by passaging organisms that had multiplied in mice to new groups of untreated mice and to mice treated with DDS incorporated in the mouse chow in concentrations of 10⁻⁵, 3 × 10⁻⁵, and 10⁻⁴ g/100 ml. The rate of response to acedapsone therapy and the susceptibility of patient strains of M. leprae to DDS varied widely among patients. All isolates were inhibited from multiplication by treatment of mice with 10⁻⁴ g of DDS per 100 ml; all but two isolates were susceptible to 3 × 10⁻⁵ g of DDS per 100 ml; and 17 of 36 isolates, representing nine patient strains, were susceptible to 10⁻⁵ g of DDS per 100 ml. Plasma levels of DDS measured in the mice administered these diets show that the minimal inhibitory concentration of DDS for M. leprae isolated from untreated patients is about 3 ng/ml. No relationship could be demonstrated between DDS susceptibility of pretreatment isolates of M. leprae and the rate at which patients responded to acedapsone therapy. Neither acedapsone treatment of patients nor DDS treatment of mice appeared to select genotypically more resistant M. leprae.     

Suppression of human T-cell mitogenesis by prostaglandin. Existence of a prostaglandin-producing suppressor cell

Small amounts of PGE inhibit mitogen-induced [3H]thymidine incorporation in human peripheral lymphocytes. The 50% inhibitory concentration is approximately 10(-7) M, and this is reduced to approximately 10(-8) M when endogenous PGE production is blocked. PGE inhibits PHA- and Con A-stimulated cultures much better than PWM cultures, suggesting a differential effect of PGE on T-cell vs. B-cell function. In vitro blockade of PG synthesis results in approximately 50% increase in [3H]thymidine incorporation in PHA cultures. PGE is produced endogenously in PHA cultures by glass adherent suppressor cells.     

Urinary concentrations and bactericidal activity against amoxicillin-nonsusceptible strains of Escherichia coli with single-dose, oral, sustained-release amoxicillin/clavulanic acid: a phase I, open-label, noncomparative clinical trial in healthy volunteers

BACKGROUND: Urinary tract infections (UTIs) account for 5 to 6 million medical consultations in the United States each year. Worldwide, an estimated 20% to 30% of women aged 20 to 40 years have at least 1 episode of the most common type of UTI (uncomplicated cystitis) in their lifetime, with Escherichia coli being the causative pathogen in 80% of cases. Antibacterial activity in urine has been shown to be correlated with outcomes of uncomplicated cystitis. OBJECTIVE: The objectives of this study were to determine urinary concentrations and ex vivo bactericidal activity of sustained-release (SR) amoxicillin/clavulanic acid 2000/125 mg against intermediately resistant and resistant strains of E coli over 72 hours and compare them with those of a susceptible strain. This study also investigated whether urinary concentrations obtained after dosing cover E coli strains categorized as intermediately resistant and resistant based on current Clinical and Laboratory Standards Institute (formerly NCCLS) breakpoints in uncomplicated cystitis. METHODS: This Phase I, open-label, noncomparative study in healthy male volunteers was conducted at the Pharmacology Unit, Autónoma University, Madrid, Spain. Subjects received a single oral dose of amoxicillin/clavulanic acid 2000/125 mg SR. The amoxicillin/clavulanic acid MICs were 8/4 microg/mL (susceptible), 16/8 microg/mL (intermediately resistant), and 32/16 and 64/32 microg/mL (resistant). Urine samples were collected before (baseline; time 0) and at the following intervals: 0-2, 2-4, 4-8, 8-12, 12-16, 16-24, 24-36, 36-48, 48-60, and 60-72 hours after dosing. Killing curves with urine samples were performed with initial inocula of approximately 10(7) colony-forming units (CFU)/mL, and bactericidal activity (defined as >3 log(10) CFU/mL and >99.9% reduction in bacterial counts) was calculated as the difference between log(10) initial inoculum and log(10) CFU/mL after 4 hours of incubation of each sample. RESULTS: Twelve volunteers were included (mean [SD] age, 24.83 [5.64] years; mean [SD] height, 175.75 [7.56] cm; and mean [SD] weight, 73.55 [9.19] kg). No statistically significant differences between the activities in the 12-16-hour interval compared with baseline were found in any of the strains tested. Bactericidal activity against the susceptible and intermediately resistant strains (MICs 8/4 and 16/8 g/mL, respectively) was obtained up to 8 hours after dosing. Bactericidal activity against the resistant strains (MICs 32/16 and 64/32 microg/mL) was obtained in the 2-4-hour interval. CONCLUSIONS: In this Phase I study in healthy volunteers, urinary concentrations after dosing with amoxicillin/clavulanic acid 2000/125 mg SR showed bactericidal activity against the amoxicillin-susceptible and intermediately resistant strains of E coli.     

Thymidine transport and metabolism in choroid plexus: effect of diazepam and thiopental

Choroid plexus contains an active transport (influx) and a facilitated diffusion (efflux) system for nucleosides. The ability of diazepam and thiopental to inhibit active transport or facilitated diffusion of thymidine in choroid plexus was measured in vitro under various conditions. When isolated rabbit choroid plexuses were incubated in artificial cerebrospinal fluid containing 1 microM [3H] thymidine for 10 min at 37 degrees C under 95% O2-5% CO2, diazepam (10 microM) and thiopental (500 microM) doubled the tissue-to-medium ratios of [3H] thymidine from 8 to 15 to 16. These results were not due to metabolism or intracellular binding but rather to inhibition of [3H] thymidine efflux from choroid plexus. Diazepam, unlike thiopental, inhibited [3H] thymidine efflux in a concentration-dependent manner. When isolated choroid plexuses were incubated in artificial cerebrospinal fluid containing low concentrations of [3H] thymidine (6 nM) to allow intracellular conversion of [3H] thymidine into [3H] thymidine phosphates and [3H] DNA, both diazepam (10 microM) and thiopental (500 microM) altered [3H] thymidine accumulation and metabolism consistent with inhibition of facilitated diffusion but not active transport of thymidine. These studies provide evidence that, at toxic but not therapeutic concentrations, diazepam and thiopental alter facilitated nucleoside transport in the choroid plexus.     

Liberation of a fibrogenic factor from human blood monocytes, ascites cells, cultured histiocytes and transformed mouse macrophages by treatment with SiO2

Human monocytes and ascites macrophages from cirrhotic patients were isolated in Percoll-gradient and cultured with and without silica. Similar experiments were carried out also with cultured malignant human histiocytes and transformed mouse macrophages. The fibrogenic activity of the culture media was tested by measuring the incorporation of [3H]proline and [3H]thymidine into cultured rat granuloma and human synovial cells. Media from silica-treated monocytes, ascites macrophages and certain histiocyte and mouse macrophage lines caused an increase in the incorporation of both [3H]proline and [3H]thymidine into collagen and DNA, respectively, in both cell systems. Alkaline RNase activities were decreased markedly in the media from silica-treated ascites macrophages but not in the media of the monocytes or histiocytes.     

Transferrable Resistance to Tobramycin in Klebsiella pneumoniae and Enterobacter cloacae Associated with Enzymatic Acetylation of Tobramycin

Among gram-negative bacilli isolated from burn wound cultures, some strains of Enterobacteriaceae were resistant to tobramycin (minimal inhibitory concentration [MIC]≥ 20 μg/ml) but susceptible to gentamicin (MIC ≤ 5 μg/ml). One Klebsiella pneumoniae and two Enterobacter cloacae strains were selected for studies on their mechanisms of resistance to aminoglycoside antibiotics. Resistance to high concentrations of tobramycin (MICs of 25 to 50 μg/ml) was conjugally transferred to a susceptible Escherichia coli strain at rates of 1.2 × 10⁻⁴ to 2.8 to 10⁻⁴ per donor cell, suggesting that resistance is controlled by R factors. Resistances to tobramycin, kanamycin, and neomycin were cotransferred. Enzymatic activities were present that acetylated tobramycin, gentamicin, and kanamycin in osmotic lysates from the donor and transcipient strains. Enzymatic adenylylation of these aminoglycosides was not observed. The aminoglycoside-acetylating activities from K. pneumoniae and E. cloacae resembled kanamycin acetyltransferase (KAT) in their specificity for aminoglycoside substrates. Not all isolates of bacteria that produce KAT are resistant to tobramycin, but the factors that determine susceptibility or resistance to tobramycin in KAT-producing bacteria have not yet been established.     

Bleomycin-induced pulmonary fibrosis in hamsters. An alveolar macrophage product increases fibroblast prostaglandin E2 and cyclic adenosine monophosphate and suppresses fibroblast proliferation and collagen production

Bleomycin-induced pulmonary fibrosis in hamsters is associated with collagen accumulation that results from increased lung collagen synthesis rates. However, 1-2 wk after intratracheal instillation of bleomycin, lung collagen synthesis rates decline toward control values. To evaluate the potential role of the bronchoalveolar macrophage in regulating lung collagen production, we studied the effects of macrophages from normal and bleomycin-treated hamsters upon fibroblasts in vitro. We observed: (a) Medium from macrophage cultures decreased fibroblast [3H]thymidine incorporation and nondialyzable [3H]hydroxyproline production in a dose-dependent manner. Fibroblast cell counts were decreased in exposed cultures, and fibroblast viability was unchanged. Procollagen prolyl hydroxylation and prolyl-transfer RNA-specific activity were not altered by macrophage medium; this indicates that [3H]hydroxyproline reflects collagen production rate under the experimental conditions. (b) The suppressive effect of macrophage medium was selective for collagen since collagen production decreased more than noncollagen protein production. (c) Medium from bleomycin-treated hamster macrophages suppressed fibroblast proliferation and collagen production to a greater degree than medium from normal hamster macrophages. (d) Fibroblast suppression by macrophage medium was associated with increased fibroblast endogenous prostaglandin E2 production and intracellular cyclic AMP (cAMP). (e) Incubation of fibroblasts with indomethacin before exposure completely inhibited prostaglandin E2 production and increases in cAMP, and eliminated suppression of fibroblast proliferation and collagen production. The macrophage-derived suppressive factor has an apparent molecular weight of 20,000-30,000 and is heat stable. It does not appear to be species restricted since both hamster and human lung fibroblasts are similarly suppressed. It is at least in part preformed in macrophages obtained by lavage, but its production can also be stimulated in vitro. We concluded that alveolar macrophages release a product that stimulates endogenous fibroblast prostaglandin E2 production and cAMP formation with resultant suppression of fibroblast proliferation and collagen production. Enhanced release of suppressive factor by macrophages during a time when lung collagen production is declining in bleomycin-induced pulmonary fibrosis suggests that macrophages may limit collagen accumulation in pulmonary fibrosis.     

心血管病医院院内感染革兰阴性杆菌分布及常见菌耐药性分析

[目的]了解心血管病医院革兰阴性杆菌的分布及常见菌的耐药性，为临床合理用药提供依据。[方法]对我院2001～2004年内外科所有病房分离的革兰阴性杆菌进行分类，用微量肉汤稀释法对常见菌进行耐药性分析。[结果]我院分离的革兰阴性杆菌以鲍曼不动杆菌，铜绿假单胞菌，肺炎克雷伯菌，大肠埃希菌及嗜麦芽窄食单胞菌为主，与相关报道相似。其中肺炎克雷伯菌产ESBL的菌株占49.3％，大肠埃希菌产ESBL的菌株占67.0％，总产酶率为55.4％，高于相关报道。亚胺培南仍是治疗肠杆菌科的最有效的抗生素；非发酵菌中除嗜麦芽窄食单胞菌对抗生素多重耐药外，铜绿假单胞菌及鲍曼不动杆菌对氨基糖甙类，多种头孢菌素及加酶抑制剂的抗生素呈现敏感，但出现耐亚胺培南的铜绿假单胞菌及鲍曼不动杆菌。[结论]根据药敏结果，合理选择抗生素，对预防耐药菌的产生具有极其重要的意义。     

Streptomycin Resistance in a Streptomycin-Producing Microorganism

Cell-free extracts of Streptomyces bikiniensis contain an adenosine 5'-triphosphate-dependent kinase which inactivates streptomycin (Sm) and dihydrostreptomycin by phosphorylation. The products have been identified as streptomycin 6-phosphate and dihydrostreptomycin 6-phosphate. Activity was not present in logarithmic-phase cells, which were susceptible to 25 mug of Sm per ml. In stationary-phase cells, activity appeared 12 h before detectable Sm in the medium. These cells were resistant to more than 200 mug of Sm per ml. Certain S. bikiniensis isolates selected from cultures treated with acriflavine or ethidium bromide lost the ability to produce Sm and became susceptible to 10 mug of Sm per ml throughout their growth. Cell-free extracts of the dye-treated isolates did not inactivate Sm and lacked streptomycin kinase activity at all stages in development. Ribosomes from resistant cells bound the same amount of [(3)H]dihydrostreptomycin as ribosomes from susceptible cells, and there was no correlation between the uptake of [(3)H]dihydrostreptomycin and resistance. The Sm-inactivating enzyme was identified as streptomycin-6-kinase. These results suggest that phosphorylation by streptomycin-6-kinase is a major factor in resistance in S. bikiniensis.     

小儿心脏术后下呼吸道感染革兰氏阴性菌分布及常见菌耐药性分析

[目的]了解小儿心脏术后下呼吸道感染革兰阴性杆菌分布情况及耐药性，为临床合理用药提供依据。[方法]对我院2001年1月～2004年12月小儿术后恢复室下呼吸道分离革兰阴性杆菌分类，同时用微量肉汤稀释法对主要病原菌的药敏结果进行分析。[结果]小儿术后恢复室下呼吸道分离阴性杆菌主要为肺炎克雷伯菌及大肠埃希菌，嗜麦芽窄食单胞菌。铜绿假单胞菌及鲍曼不动杆菌。其中肠杆菌产ESBL比率较高且对抗生素耐药性强，亚胺培南仍是治疗产酶的肺炎克雷伯菌及大肠埃希菌最有效的抗生素。非发酵菌中嗜麦芽窄食单胞菌呈现对抗生素多重耐药，鲍曼不动杆菌及铜绿假单胞菌均出现亚胺培南耐药株。[结论]根据药敏结果合理使用抗生素对预防耐药菌株的出现有极其重要的意义。     

Effects of a derivative of serotonin (deoxyfructoserotonin) and other antileprosy drugs on attachment and uptake of Mycobacterium leprae by Schwann cells in vitro.

The association (attachment and/or uptake) of Mycobacterium leprae with cultured Schwann cells was studied at 8 and 72 h in the presence of a new antileprosy compound, deoxyfructoserotonin (DFS), as well as conventional antileprosy drugs such as rifampin (RFP) and 4,4'-diaminodiphenyl sulfone (DDS). DFS significantly inhibited bacterial association with Schwann cells at 8 h. RFP also affected the association of M. leprae but not to the same extent as DFS. A similar inhibition at 8 h was noted when M. leprae but not Schwann cells were pretreated with DFS or RFP for 5 days before infection of cultures, implying that modulation was achieved through some form of drug action on bacteria. DDS had no effect on M. leprae association; however, the combination of DFS and DDS was neither antagonistic nor additive. At 72 h postinfection, when attached but noninternalized bacteria were removed with trypsin-EDTA from Schwann cell cultures containing DFS or RFP, a 50% reduction in the number of bacteria in the drug-treated group was obtained as compared with the numbers in drug-free cultures. This indicated a slow entry of M. leprae into Schwann cells in the presence of these drugs. Collectively, these observations point to differing requirements for late and early association of M. leprae with Schwann cells, besides suggesting a role for DFS and RFP in the prevention and minimization of M. leprae-induced nerve damage in vivo.     

泌尿系感染常见病原菌分布及耐药性分析

[目的]了解我院泌尿系感染病原菌的分布及常见病原菌的耐药性，为临床合理用药提供依据。[方法]采用API鉴定系统进行病原菌鉴定，用琼脂纸片扩散法（K—B法）进行药敏试验。[结果]分离出病原菌282株，其中革兰阴性杆菌199株，占70．57％；革兰阳性球菌67株，占23．76％。检出率最高的是大肠埃希菌，其次为肠球菌和葡萄球菌等。大肠埃希菌对亚胺培南、头孢哌酮／舒巴坦、哌拉西彬他唑巴坦的耐药率较低，分别为1．32％、7．89％、11．18％；肠球菌及葡萄球菌对万古霉素耐药率最低，分别为3．33％和0。[结论]泌尿系感染主要由革兰阴性杆菌引起。临床医生应依据药敏试验结果合理使用抗生素。     

5-Fluorocytosine Resistance in Cryptococcus neoformans

Isolates of Cryptococcus neoformans from six patients were obtained before and after unsuccessful therapy with 5-fluorocytosine (5-FC). Post-therapy isolates exhibited massive and stable 5-FC resistance. The frequency of drug-resistant mutants in susceptible isolates of C. neoformans was <0.001% (70.4 +/- 17.9 per 10(7) cryptococci), whereas mutant frequencies in resistant isolates approached 100%. Non-drug-induced, spontaneously appearing 5-FC resistant mutants were documented in four susceptible isolates of C. neoformans by use of the statistical method of fluctuation analysis. Mutation rates on these same four isolates ranged from 1.2 x 10(-7) to 4.8 x 10(-7). Total intracellular uptake and incorporation of cytosine-5-(3)H (CyH(3)) and 5-fluorocytosine-2-(14)C (5-FC(14)) into a trichloroacetic acid-insoluble fraction were markedly reduced in six isolates with in vivo-acquired resistance when compared with susceptible pretreatment strains from the same patients. Five of these six isolates also had acquired massive resistance to 5-fluorouracil (5-FU), suggesting that a mutation in the uridine-5'-monophosphate pyrophosphorylase was responsible for drug resistance. The sixth isolate, which remained susceptible to 5-FU, appeared to have a defect in a cytosine-specific permease accounting for 5-FC resistance. A single isolate with in vitro-acquired 5-FC and 5-FU resistance had no reduction in uptake or incorporation of CyH(3) or 5-FC(14). The mechanism of resistance in this isolate is discussed.     

Gentamicin uptake in Staphylococcus aureus possessing plasmid-encoded, aminoglycoside-modifying enzymes.

[3H]gentamicin uptake and killing were studied in three strains of gentamicin-resistant Staphylococcus aureus possessing plasmid-encoded, gentamicin-modifying enzymes and in three isogenic, enzyme-free, gentamicin-susceptible derivatives. At low (less than or equal to 2.0 micrograms/ml) concentrations of gentamicin, uptake by resistant organisms was impaired compared with that of susceptible strains, and no killing was noted. In contrast, at higher (2.5 to 10.0 micrograms/ml) concentrations (which were below the MIC for the resistant strains), rapid gentamicin uptake similar to that seen in susceptible isolates was observed. Although growth inhibition at these concentrations was apparent, there was no loss of viability in resistant strains. Consistently, the membrane H+-ATPase inhibitor N,N'-dicyclohexyl carbodiimide caused resistant strains to take up low concentrations (1.0 microgram/ml) of gentamicin at rates comparable to those seen in susceptible organisms without causing an associated loss of viability. These studies show differences between gentamicin uptake in S. aureus and streptomycin uptake in Escherichia coli (Dickie et al., Antimicrob. Agents Chemother. 14:569-580, 1978) regarding the kinetics of uptake in resistant strains with plasmid-encoded aminoglycoside-modifying enzymes. Specifically, they suggest that for 2-deoxystreptamine compounds such as gentamicin, ribosomal binding followed by accelerated uptake and subsequent interference with cell growth may occur without invariably being associated with lethal effect.     

Cefoxitin, a semisynthetic cephamycin antibiotic: antibacterial spectrum and resistance to hydrolysis by gram-negative beta-lactamases

The in vitro activity of cefoxitin, 3-carbamolyloxymethyl-7-alpha-methoxy-7[2-(2-thienyl)acetamido]-3-cephem-4-carboyxlic acid, was investigated. Activity against gram-positive organisms was less than that of cephalothin and cephloridine. It was highly active against gram-negative bacilli, with activity against Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae equal to that of currently available cephalosporins. In addition, it was active against certain Enterobacter strains, Serratia marcescens, indole-positive Proteae and Herellea. The strains of these latter bacteria were strains susceptible to carbenicillin and ticarcillin. Pseudomonas aeruginosa and other Pseudomonas species were resistant. Changes in pH, inoculum size, and type of growth medium had no significant effect on the activity of the antibiotic. Cefoxitin was highly resistant to hydrolysis by various types of gram-negative beta-lactamases. The precise role of resistance to beta-lactamase hydrolysis varied from strain to strain. Bacterial resistance to cefoxitin was not necessarily related to hydrolysis of the antibiotic. However, the resistance of cefoxitin to hydrolysis did contribute to its activity. Cefoxitin could function as an inducer of beta-lactamase activity and effectively bound to purified beta-lactamases.     

Wide-spectrum antibiotic activity of bovine granulocyte polypeptides

The antibiotic activity of a polypeptide fraction purified from bovine granulocyte granules was tested against Escherichia coli, Pseudomonas aeruginosa, Salmonella typhimurium, Bacillus subtilis, Bacillus stearothermophilus, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, Streptococcus pyogenes, and clinical isolates of Staphylococcus and Enterobacter spp. All of these bacterial species were susceptible to the antibiotic polypeptide(s), with MICs ranging from 3 to 100 micrograms of protein per ml. The antimicrobial activity was resistant to boiling and abolished by proteinase treatment. Saccharomyces cerevisiae and human fibroblasts grew normally in the presence of 100 and 50 micrograms of antibiotic polypeptide(s) per ml, respectively. [3H]thymidine incorporation into bacterial, but not fibroblast, DNA was efficiently and promptly inhibited by the antimicrobial polypeptide preparation. This suggests that its main target is a component of the system, which catalyzes and regulates the biosynthesis of bacterial DNA.     

4-Quinolone drugs affect cell cycle progression and function of human lymphocytes in vitro.

Most antibacterial agents do not affect human lymphocyte function, but a few are inhibitory. In contrast, a pronounced increase in the incorporation of [3H]thymidine in the presence of 4-quinolones was observed in these studies. The uptake of [3H]thymidine into DNA (trichloroacetic acid precipitable) was significantly increased in phytohemagglutinin-stimulated human lymphocytes when they were exposed to eight new 4-quinolone derivatives, ciprofloxacin, norfloxacin, ofloxacin, A-56619, A-56620, amifloxacin, enoxacin, and pefloxacin, at 1.6 to 6.25 micrograms/ml for 5 days. Four less antibacterially active 4-quinolones (nalidixic acid, cinoxacin, flumequine, and pipemidic acid) stimulated [3H]thymidine incorporation only at higher concentrations or not at all. Kinetic studies showed that incorporation of [3H]thymidine was not affected or slightly inhibited by ciprofloxacin 2 days after phytohemagglutinin stimulation but was increased on days 3 to 6. The total incorporation of [3H]thymidine from day 1 to day 6 after phytohemagglutinin stimulation was increased by 42 to 45% at 5 to 20 micrograms of ciprofloxacin per ml. Increased [3H]thymidine incorporation was also seen when human lymphocytes were stimulated with mitogens other than phytohemagglutinin. Ciprofloxacin added at the start of the culture had a more pronounced effect on [3H]thymidine incorporation than when added later. In spite of the apparent increase in DNA synthesis, lymphocyte growth was inhibited by 20 micrograms of ciprofloxacin per ml, and cell cycle analysis showed that ciprofloxacin inhibited progression through the cell cycle. In addition, immunoglobulin secretion by human lymphocytes stimulated by pokeweed mitogen for Epstein-Barr virus was inhibited by approximately 50% at 5 micrograms of ciprofloxacin per ml. These results suggest that the 4-quinolone drugs may also affect eucaryotic cell function in vitro, but additional studies are needed to establish an in vivo relevance.