Synergistic action of streptomycin with other antibiotics of intracellular Brucella abortus in vitro

Streptomyces sp. AN090126 as a Biocontrol Agent against Bacterial and Fungal Plant Diseases

Bacteria and fungi are major phytopathogens which substantially affect global agricultural productivity. In the present study, Streptomyces sp. AN090126, isolated from agricultural suppressive soil in Korea, showed broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In the 96-well plate assay, the fermentation filtrate of Streptomyces sp. AN090126 exhibited antimicrobial activity, with a minimum inhibitory concentration (MIC) of 0.63–10% for bacteria and 0.63–3.3% for fungi. The MIC of the partially purified fraction was 20.82–250 µg/mL for bacteria and 15.6–83.33 µg/mL for fungi. Gas chromatography–mass spectrometry (GC-MS) analysis revealed that AN090126 produced various volatile organic compounds (VOCs), including dimethyl sulfide and trimethyl sulfide, which inhibited the growth of pathogenic bacteria and fungi in in vitro VOC assays. In pot experiments, the fermentation broth of Streptomyces sp. AN090126 reduced tomato bacterial wilt caused by Ralstonia solanacearum, red pepper leaf spot caused by Xanthomonas euvesicatoria, and creeping bentgrass dollar spot caused by Sclerotinia homoeocarpa in a dose-dependent manner. Moreover, the secondary metabolites derived from this strain showed a synergistic effect with streptomycin sulfate against streptomycin-resistant Pectobacterium carotovorum subsp. carotovorum, the causative agent of Kimchi cabbage soft rot, in both in vitro and in vivo experiments. Therefore, Streptomyces sp. AN090126 is a potential biocontrol agent in controlling plant diseases caused by pathogenic bacteria and fungi, specifically by the streptomycin-resistant strains.

Control of Citrus Huanglongbing via Trunk Injection of Plant Defense Activators and Antibiotics

Citrus huanglongbing (HLB) or greening is a devastating disease of citrus worldwide and no effective control measure is currently available. Plant defense activators environmentally friendly compounds capable of inducing resistance against many plant pathogens. Earlier studies showed that foliar spray of plant defense inducers could slow down HLB disease progress. In this study, eight plant defense activators and three antibiotics were evaluated in three field trials for their effect to control HLB by trunk injection of young and mature sweet orange trees. Results showed that four trunk injections of several activators, including salicylic acid, oxalic acid, acibenzolar-S-methyl, and potassium phosphate, provided significant control of HLB by suppressing 'Candidatus Liberibacter asiaticus' titer and disease progress. Trunk injection of penicillin, streptomycin, and oxytetracycline hydrochloride resulted in excellent control of HLB. In general, antibiotics were more effective in reduction of 'Ca. L. asiaticus' titer and HLB symptom expressions than plant defense activators. These treatments also resulted in increased yield and better fruit quality. Injection of both salicylic acid and acibenzolar-S-methyl led to significant induction of pathogenesis-related (PR) genes PR-1 and PR-2 genes. Meanwhile, injection of either potassium phosphate or oxalic acid resulted in significant induction of PR-2 or PR-15 gene expression, respectively. These results suggested that HLB diseased trees remained inducible for systemic acquired resistance under field conditions. In summary, this study presents information regarding controlling HLB via trunk injection of plant defense activators and antibiotics, which helps citrus growers in decision making regarding developing an effective HLB management program.

Intracellular Production of Brucella L Forms I. Recovery of L Forms from Tissue Culture Cells Infected with Brucella abortus

Hatten, Betty A. (The University of Texas Southwestern Medical School, Dallas), and S. Edward Sulkin. Intracellular production of Brucella L forms. I. Recovery of L forms from tissue culture cells infected with Brucella abortus. J. Bacteriol. 91:285-296. 1966.-Infectivity of virulent Brucella abortus strain 3183 was less for hamster macrophages after a 2-hr adsorption period than for an attenuated strain (S19) and its tissue culture variant (30). Both strains S19 and 30 were very toxic for the cells, but 3183 was not toxic. Two types of L forms were recovered from a large percentage of hamster kidney cell cultures when disintegration of infected cells was accelerated by tissue culture medium of high pH. One type grew in finely granular microcolonies, was isolated from cells infected for short periods of time, and often reverted to the bacterial form. The other type occurred in small irregularly shaped forms which later developed into round bodies. Both stained specifically with fluorescein-conjugated B. abortus antiserum. Semisolid media containing 0.7% agar provided optimal subsurface L-form growth. L forms also grew well in Thioglycollate Medium but grew poorly in other liquid media. Surface L-form growth was supported by several agar media, but CO(2) was required for optimal growth. Monolayers infected with strain 3183 and examined immediately after adsorption contained occasional small, round bodies. Bizarre forms increased in number with time and, after 24 to 72 hr, large pink-staining inclusions were often present which persisted for several days. Also appearing at about the same time were smaller, dark-staining forms which were first seen in clusters but later dispersed and finally occurred in chainlike configurations. Direct fluorescent-antibody stains of infected cells established that the intracellular forms were related to the infecting strain of B. abortus.

Intracellular Pasteurella pseudotuberculosis: Multiplication in Cultured Spleen and Kidney Cells

Pasteurella pseudotuberculosis multiplied within rabbit cells in primary culture. Spleen cells from rabbits were either dispersed mechanically, exposed to the organism immediately after cell preparation, and grown as a pellet or the cells were dispersed enzymatically and grown as a monolayer for 4 to 6 days before the bacteria were introduced. Intracellular multiplication proceeded at a logarithmic rate for 1 to 2 days, with a generation time of about 70 min in pelleted cells and 4 to 5 hr in monolayered cells. Under the conditions employed, the wild-type virulent strain and an avirulent mutant multiplied at similar rates. Atmosphere, constituents of the medium, and multiplicity of infection influenced intracellular proliferation. The organism also proliferated in kidney cells. Microscopic observation of stained cells indicated limited growth of the pathogen in spleen cells at 37 C. In kidney cells, the pasteurellae localized in compartments; frequently, a single compartment with masses of proliferating organisms almost filled the cytoplasm.

Successful management of Brucella mellitensis endocarditis with combined medical and surgical approach

OBJECTIVES

Brucella endocarditis is an underdiagnosed complication of human brucellosis, associated with high morbidity and mortality. We report the successful management of a number of cases of Brucella mellitensis endocarditis.

PATIENTS AND METHODS

Seven consecutive cases of Brucella mellitensis endocarditis were treated over the last 20 years, based on high suspicion of the disease at first place. The early suspicion of Brucella endocarditis relied on medical history and a standard tube agglutination titer > or =20. Blood and/or cardiac tissue cultures were positive in all patients, but available late following surgery. All patients were successfully treated with a combination of aggressive medical and early surgical therapy. All affected valves were replaced within 1 week from admission (five aortic and three mitrals). Medical treatment included co-trimoxazole, tetracyclines and streptomycin, before surgery, followed by co-trimoxazole and tetracyclines for a median of 12 months (range: 3-15 months) after surgery until the titers returned to a level < or =1:160.

RESULTS

There were neither operative deaths nor recurrence of infection. One patient died two years after the operation due to massive cerebrovascular accident. Ten-year survival was 85.7+/-13.2%.

CONCLUSION

Although Brucella mellitensis endocarditis is a rare entity, its optimum management should be a combination of aggressive medical treatment and early surgical intervention, based on high degree of suspicion in areas with high incidence of the disease.

Recognition and optimum treatment of brucellosis

Brucellosis (infection with Brucella spp.) is a common zoonosis in many parts of the world. Human brucellosis is a multisystem disease that may present with a broad spectrum of clinical manifestations. Treatment of brucellosis must effectively control acute illness and prevent complications and relapse. The choice of regimen and duration of antimicrobial therapy should be based on the presence of focal disease and underlying conditions which contraindicate certain specific antibiotics. The regimen of first choice is combination therapy with doxycycline for 45 days and streptomycin for 14 days. Gentamicin or netilmicin for the first 7 days may be substituted for streptomycin. Second-choice regimens consist of combinations of doxycycline and rifampicin (rifampin) for 45 days, or monotherapy with doxycycline for 45 days. Surgery should be considered for patients with endocarditis, cerebral or epidural abscess, spleen abscess or other abscesses which are antibiotic-resistant. Tetracyclines are generally contraindicated for pregnant patients and children < 8 years old. Rifampicin 900 mg once daily for 6 weeks is considered the drug of choice for treating brucellosis in pregnant women. In children < 8 years old the preferred regimen is rifampicin with cotrimoxazole (trimethoprim-sulfamethoxazole) for 45 days. An alternative regimen consists of a combination of rifampicin for 45 days with gentamicin 5 to 6 mg/kg/day for the first 5 days.

Dihydrostreptomycin or streptomycin in combination with penicillin G in dairy cattle therapeutics: A review and re-analysis of published data Part 1: Clinical pharmacology

Combination formulations of penicillin G salts and dihydrostreptomycin were developed during the 1960s and are currently marketed in New Zealand for parenteral and intramammary use in dairy cattle. In this paper, the clinical indications and efficacy, pharmacokinetics and potential for antimicrobial synergy of penicillin and dihydrostreptomycin or streptomycin, when combined, are discussed.

MULTIPLICATION OF BRUCELLA IN CULTURED LYMPHOID AND NONLYMPHOID CELLS

Richardson, Marvis (Michigan State University, East Lansing), and Jane N. Holt. Multiplication of Brucella in cultured lymphoid and nonlymphoid cells. J. Bacteriol. 88:1163-1168. 1964.-Growth curves were established for the multiplication of Brucella abortus in cultured bovine cells. The number of viable brucellae was determined by colony count after lysis of the parasitized tissue cells. It was found that the number of brucellae dropped during the first 3 to 6 hr. This was followed by intracellular growth. Brucellae multiplied in uterine mucosal and fetal skin cells at an exponential rate with a 4-hr generation time. In contrast, only limited multiplication occurred in spleen cell cultures, usually approaching the stationary phase by 20 to 30 hr. Preliminary results indicated an average generation time of 8 hr in calf spleen cells. Differences were apparent in the ability of spleen cells from individual calves to support intracellular growth. This suggests that a relationship may exist between the establishment of intracellular pathogens in vitro and the natural resistance of the animal. By the use of fluorescein-labeled antisera, some insight was gained into the fate of brucellae in lymphoid cells. Fluorescent antisera stained intact brucellae and also revealed soluble antigen in the cytoplasm of reticularlike cells.

Ability of mononuclear phagocytes from cattle naturally resistant or susceptible to brucellosis to control in vitro intracellular survival of Brucella abortus

The role of bovine mammary macrophages and peripheral blood monocyte-derived macrophages in natural resistance to bovine brucellosis was evaluated. A group of 11 naturally resistant and 10 chronically infected susceptible cows was studied following challenge with Brucella abortus. Macrophages from a greater proportion (P less than 0.026) of naturally resistant cows were significantly superior to macrophages from susceptible cows in their ability to inhibit the in vitro intracellular replication of B. abortus after challenge exposure. Studies of a second group of cows used mammary macrophages from 12 heifers and blood monocyte-derived macrophages from 22 bulls and heifers. These tests were completed before exposure to B. abortus, using mammary macrophages (P less than 0.039) and blood monocyte-derived macrophages (P less than 0.045), and also showed that macrophages from naturally resistant cattle were significantly superior in their ability to control the in vitro intracellular replication of B. abortus. Our data indicate that the mononuclear phagocytes from more than 80% of the resistant cattle controlled intracellular replication of B. abortus significantly better than did mononuclear phagocytes from susceptible cattle. Mononuclear phagocyte function appears to be an important factor in determining natural resistance to bovine brucellosis.

Brucellosis of the central nervous system. A case report of an infected infant

Brucellosis in early infancy is unusual and reports of congenitally acquired infection are extremely rare. The patient presented at the age of 8 months with high fever and signs of meningitis. He had a previous history of hydrocephalus undergoing shunt alleviation at 1 month of age. A diagnosis of central nervous system (CNS) brucellosis was subsequently made. Transplacental transmission is offered as a possible explanation for the acquisition of this child's brucellosis infection.

Experimental treatment of Brucella melitensis infection in sheep with oxytetracycline alone or combined with streptomycin

The efficacy of oxytetracycline (OTC) alone or combined with streptomycin in the treatment of 118 Najdi ewes believed to have been naturally infected with Brucella melitensis, was evaluated by culture of selected tissues and organs at slaughter. Groups of sheep were given 250, 500 or 1,000 mg of OTC intraperitoneally (i/p) daily for six weeks and in the respective groups at necropsy 52, 69 and 100% of sheep were found to be Brucella-free. Treatment with 250 mg OTC (daily for six weeks i/p) combined with 1,000 mg streptomycin (daily for three weeks intramuscularly) increased the percentage of Brucella-free sheep to 82%. When a group of sheep were each inoculated i/p with 1,000 mg of long-acting OTC every three days over a period of six weeks, 75% of them were Brucella-free at necropsy. B. melitensis was isolated from all (24) non-treated (control) sheep. The results showed that long-term treatment with a high dose of OTC alone had succeeded in eliminating B. melitensis from a group of 16 naturally infected sheep.

Cytological changes related to Brucella canis variants uptake in vitro

In this study, evidence for in vitro uptake, invasion, and cytopathogonomic effects of normal and variant strains of B. canis on tissue culture, is presented. B. canis L-phase were penicillin-induced and these microorganisms produced revertants on penicillin-free media. Tissue culture (LLC-MK2) cells were divided into different normal and variant-infected groups (I-IV), including controls. Bright-field and electron microscopic observations indicated uptake of all the strains and recognizable host cell damage (CPE) to varying degrees. At 72 h after infection, the extent of damage by L-phase was the least (55.5% CPE). The L-phase-derived revertants resulted in 80% damage; this approximates the adverse effect of normal B. canis (85%). In addition to these gross changes, various structural abnormalities, including pyknosis, nuclear disorganization, vacuolation, and karyorrhexis, were apparent. The implications of these findings and the indirect role of the L-phase in brucellosis due to B. canis are discussed.

Suppressive activity of streptomycin on the growth of Mycobacterium lepraemurium in macrophage cultures

The effect of streptomycin on the growth of an obligate intracellular bacterium was studied in a new host-parasite cell system. The system consisted of Mycobacterium lepraemurium grown in cultures of mouse peritoneal macrophages. Since these organisms do not grow in bacteriological media, the influence of extracellular bacterial growth can be ruled out. The suppressive activity of streptomycin was observed in a total of five experiments. At the end of 4 weeks, the average number of organisms per macrophage for the controls was 65.7; for cultures with streptomycin at concentrations of 0.5, 1, 5, 10, 50, and 100 mug/ml of medium, it was 45.4, 38.3, 28.7, 22.7, 13.4, and 8.2, respectively. A good dose-response relationship was evident. M. lepraemurium which had been treated in macrophage cultures with various concentrations of the antibiotic for 6 to 8 weeks was used to infect fresh macrophages. These cultures were in turn treated with streptomycin. Resistance of the organisms to streptomycin did not occur.

Intracellular production of Brucella L forms . II. Induction and survival of Brucella abortus L forms in tissue culture

Hatten, Betty A. (The University of Texas Southwestern Medical School, Dallas), and S. Edward Sulkin. Intracellular production of Brucella L forms. II. Induction and survival of Brucella abortus L forms in tissue culture. J. Bacteriol. 91:14-20. 1966.-Intracellular survival of altered brucellae, possibly L forms, was not greatly affected by penicillin or streptomycin in concentrations ranging from 5.0 to 40 mug/ml, but a combination of these two antibiotics (2.5 to 20 mug/ml each) reduced the number of positive L-form cultures. Tetracycline (2.0 mug/ml) decreased the number of positive L-form cultures at about the same rate as combinations of the higher concentrations of penicillin and streptomycin. Various concentrations of tetracycline (0.1 to 2.0 mug/ml) with 5.0 mug/ml of penicillin or streptomycin significantly reduced the number of positive L-form cultures. L forms were recovered for several days after elimination of bacteria from the cultures by all of the antibiotics tested. L-form production was not dependent upon the presence of antibiotics in the culture medium, but they were recovered in greater numbers when bacteria were still present in the hamster kidney cells. Addition of thallium acetate to infected cells (at varying intervals of time after infection) to control bacterial growth and conversion to the L phase during cellular disintegration decreased the number of positive L-form cultures obtained over a 10-day period. Comparison of the antibiotic sensitivity of bacteria recovered from infected tissue culture cells with the stock strain of Brucella abortus indicated that some resistance to penicillin and tetracycline had developed. A marked resistance to streptomycin was observed in those bacteria recovered from cells maintained in the presence of this antibiotic.

FACTORS INFLUENCING THE PHAGOCYTOSIS OF ESCHERICHIA COLI

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