Intraglandular injection of antibiotics for the treatment of vesicular adenitis in bulls

Two experiments were designed to determine the efficacy of intraglandular antibiotic treatment in beef bulls. Experiment 1 was designed to evaluate the glandular tissue reaction to intraglandular antibiotic treatment. Experiment 2 was conducted to determine the efficacy intraglandular injection of antibiotics for the treatment of naturally occurring cases of vesicular adenitis. Healthy beef bulls (n=15), 2 and 3 years of age, were randomly allocated to three equal treatment groups to receive 10% of the daily recommended parenteral dose of penicillin, ceftiofur, or oxytetracycline in a volume of 6 mL injected directly into one of the vesicular glands. Ultrasonography was performed before, immediately after, and at 24, 48 and 168 h after intraglandular injection. The size and hardness of vesicular glands injected with oxytetracycline was greater (P<0.01) than those injected with ceftiofur. Ultrasonographic pixel intensity increased (P<0.01) after treatment with antibiotics, especially after treatment with oxytetracycline or penicillin. In Experiment 2, yearling beef bulls with clinical vesicular adenitis (n=14) were referred to the Western College of Veterinary Medicine for treatment. Eight bulls had unilateral and six had bilateral vesicular adenitis. The most common isolate was Arcanobacterium pyogenes. Corynebacterium pseudotuberculosis was isolated from one bull. Bulls were subjected to rectal palpation and ultrasonography of the vesicular glands, semen collection by electroejaculation, and intraglandular treatment with ceftiofur (n=13) and if necessary, a second intraglandular treatment of penicillin (n=6). One bull was treated only with an initial intraglandular injection of penicillin. Bulls were evaluated once a week over 6 weeks by palpation of the glands, and evaluation of semen. All bulls recovered from vesicular adenitis after 3-6 weeks. There was a difference in the amount of pus (P=0.042), leukocytes (P<0.001) and blood (P=0.003) present in ejaculates from before treatment to 3 weeks after treatment. Pixel intensities in ultrasonographic images of healthy or affected vesicular glands, whether treated or untreated, did not change over time. Intraglandular injection of ceftiofur in yearling bulls via the ischiorectal fossa was effective for treating vesicular adenitis.     

Early detection and treatment of vesicular adenitis in bulls

The objective of this study was to determine whether early detection and treatment with tilmicosin would reduce the number of yearling bulls culled due to vesicular gland disease at the time of their first semen test. Bulls (n=2207) of 15 breeds at 17 performance test stations were examined by transrectal palpation at 9-12 months of age and assigned to three treatment groups: (1) positive treated group, receiving subcutaneous injections of tilmicosin every second day for three treatments (2) positive untreated control group, (3) negative untreated control group. Transrectal palpation of the glands was done again at a pre-sale semen test 28-70 d (mean=42.8 d) after the first examination. Semen was evaluated for the presence of pus and/or leukocytes by light microscopy. The proportion of bulls with vesiculitis was 4.4% (97/2207). At the pre-sale semen test the number of bulls with vesiculitis had decreased to 1.3% (29/2207); however, seven of these were new cases that developed after the first examination. Therefore, there was a recovery rate of 75/97 (77.3%) in the original group of bulls positive for vesiculitis. At the pre-sale test, there was no difference in the proportion of bulls with enlarged glands in the positive treated group (15/66) versus the positive untreated group (7/31) and no difference in the proportion of bulls with leukocytes or pus in their semen samples. The results of this experiment did not indicate any advantage in detection and treatment of vesiculitis before a year on age due to a high rate of spontaneous recovery.     

Mycoplasmosis: Experimental and Spontaneous Infections of the Genital Tract of Bulls

A strain of M. bovigenitalium was isolated from semen of a bull (K) with chronic seminal vesiculitis. Using this strain a vesiculitis of the same type as found in bull K, characterized by simultaneous acute and chronic lesions, was induced experimentally in 2 bulls by direct inoculation into the vesicular glands. In the acute phase a marked infiltration of eosinophils was found in the interstitial tissues and alveoli whereas in the chronic phase fibrosis, lymphoid and epithelial hyperplasia were seen. Degeneration of vascular walls and connective tissue was common. On inoculation into the testis of 3 bulls a chronic epididymitis and ampullitis were produced. The histological changes were of the same type as found in the vesicular glands of the 3 bulls with vesiculitis. By indirect hemagglutination a specific and significant increase in serum antibody could be demonstrated. As the titers were low and the maximum titers were reached early, it will probably not often be possible to make an etiological diagnosis on the basis of serological evidence. A comparative experiment employing the type strain (PG 11) of M. bovigenitalium was performed. A rise in antibody titer was seen, but neither clinical nor histological changes could be demonstrated.     

Using a Sequential Regimen to Eliminate Bacteria at Sublethal Antibiotic Dosages

We need to find ways of enhancing the potency of existing antibiotics, and, with this in mind, we begin with an unusual question: how low can antibiotic dosages be and yet bacterial clearance still be observed? Seeking to optimise the simultaneous use of two antibiotics, we use the minimal dose at which clearance is observed in an in vitro experimental model of antibiotic treatment as a criterion to distinguish the best and worst treatments of a bacterium, Escherichia coli. Our aim is to compare a combination treatment consisting of two synergistic antibiotics to so-called sequential treatments in which the choice of antibiotic to administer can change with each round of treatment. Using mathematical predictions validated by the E. coli treatment model, we show that clearance of the bacterium can be achieved using sequential treatments at antibiotic dosages so low that the equivalent two-drug combination treatments are ineffective. Seeking to treat the bacterium in testing circumstances, we purposefully study an E. coli strain that has a multidrug pump encoded in its chromosome that effluxes both antibiotics. Genomic amplifications that increase the number of pumps expressed per cell can cause the failure of high-dose combination treatments, yet, as we show, sequentially treated populations can still collapse. However, dual resistance due to the pump means that the antibiotics must be carefully deployed and not all sublethal sequential treatments succeed. A screen of 136 96-h-long sequential treatments determined five of these that could clear the bacterium at sublethal dosages in all replicate populations, even though none had done so by 24 h. These successes can be attributed to a collateral sensitivity whereby cross-resistance due to the duplicated pump proves insufficient to stop a reduction in E. coli growth rate following drug exchanges, a reduction that proves large enough for appropriately chosen drug switches to clear the bacterium.     

Microbiological aspects of the elaboration of effective antibiotic therapy of bacterial lesions of the biliary tract

Sensitivity of staphylococci of different origin to desoxycholic, cholic and choleic bile acids was studied. On this basis a system for differentiation of the staphylococcal bilicultures from the staphylococcal cultures of the other origin was developed. It was shown that the bile and bile acids potentiated the activity of some antibiotics and inhibited the action of the others. Such a strictly individual property of synergism or antagonism of the cholates and antibiotics depended on the properties of the causative agent and the type of the antibiotics and bile acids. The results of the study provided the development of a method for determination of the biliculture antibiotic sensitivity on a medium containing the patient's bile. The antibiotic which induced the maximum inhibition of the bacterial growth in the presence of the patient's bile should be recommended for the treatment of this patient.     

Bacteriology of preserved stallion semen and antibiotics in semen extenders

Three experiments were conducted to evaluate the effects of different antibiotics in a milk-glucose semen extender on motility of equine sperm and elimination of bacteria following storage of extended semen in vitro. In Experiment 1, 7 antibiotics were compared: amikacin, gentamicin, streptomycin, potassium penicillin, sodium penicillin, ticarcillin, and polymixin B. In Experiment 2, 3 antibiotic treatments were compared: potassium penicillin G, amikacin, or a combination of potassium penicillin G and amikacin. In Experiment 3, 3 antibiotic treatments were compared: potassium penicillin G-amikacin, ceptiofur, and a combination of ticarcillin and clavulanic acid (Timentin). Control treatments (antibiotic-free extender) were included in each experiment. Six motility variables were evaluated: percentage of motile sperm; percentage of progressively-motile sperm; percentage of rapidly-motile sperm; mean curvilinear velocity; mean average path velocity; and mean straight-line velocity. In Experiment 1, mean percentages of motile, progressively motile and rapidly motile sperm were lower (P < 0.05) in semen exposed to polymixin B then in other treatments. Mean average-path velocity of sperm in extender containing polymixin B was lower (P < 0.05) than that of all other treatments, with exception of control or ticarcillin. Mean straight-line velocity of sperm in extender containing polymixin B was lower (P < 0.05) than that of all other treatments, with exception of control, streptomycin or ticarcillin. Semen samples containing gentamicin, amikacin, streptomycin, or potassium penicillin were more effective (P < 0.05) at eliminating bacterial growth than those samples containing polymixin B. Semen samples containing gentamicin were also more effective (P < 0.05) at eliminating bacterial growth than those samples containing ticarcillin or sodium penicillin. In Experiment 2, mean percentage of rapidly-motile sperm, and mean curvilinear, average-path, and straight-line velocities were greater (P < 0.05) for potassium penicillin-amikacin than values for all other treatments. In 2 of 3 stallions, an effect of treatment on percentage of motile sperm was detected (P < 0.05). For one stallion, mean motility of potassium penicillin-amikacin was greater (P < 0.05) than that of all other treatment groups. For another stallion, mean motility of the control was lower (P < 0.05) than that of the other treatments. Following storage, potassium penicillin (16/18 [89%]) or potassium penicillin-amikacin (17/19 [94%]) were more effective (P < 0.05) at controlling aerobic and anaerobic bacterial isolates in semen specimens than was amikacin (10/18 [56%]). In Experiment 3, a difference among treatment groups for motility variables was not detected (P < 0.05). No bacterial growth was recovered in antibiotic-treated semen, with exception of Micrococcus sp. (2 colonies) which were isolated from one semen specimen treated with ceptiofur.     

Novel strategies for inhibition of bacterial biofilm in chronic rhinosinusitis

An important role has been recently reported for bacterial biofilm in the pathophysiology of chronic diseases, such as chronic rhinosinusitis (CRS). CRS, affecting sinonasal mucosa, is a persistent inflammatory condition with a high prevalence around the world. Although the exact pathological mechanism of this disease has not been elicited yet, biofilm formation is known to lead to a more significant symptom burden and major objective clinical indicators. The high prevalence of multidrug-resistant bacteria has severely restricted the application of antibiotics in recent years. Furthermore, systemic antibiotic therapy, on top of its insufficient concentration to eradicate bacteria in the sinonasal biofilm, often causes toxicity, antibiotic resistance, and an effect on the natural microbiota, in patients. Thus, coming up with alternative therapeutic options instead of systemic antibiotic therapy is emphasized in the treatment of bacterial biofilm in CRS patients. The use of topical antibiotic therapy and antibiotic eluting sinus stents that induce higher antibiotic concentration, and decrease side effects could be helpful. Besides, recent research recognized that various natural products, nitric oxide, and bacteriophage therapy, in addition to the hindered biofilm formation, could degrade the established bacterial biofilm. However, despite these improvements, new antibacterial agents and CRS biofilm interactions are complicated and need extensive research. Finally, most studies were performed in vitro, and more preclinical animal models and human studies are required to confirm the collected data. The present review is specifically discussing potential therapeutic strategies for the treatment of bacterial biofilm in CRS patients.     

ppGpp介导的抗生素胁迫应答机制研究进展

抗生素是由微生物在生长发育后期产生的次级代谢产物,具有杀死或抑制细菌生长的能力,因此被广泛应用于细菌感染的临床治疗。在长期的进化过程中,细菌采取多种方式应对环境中抗生素的威胁。除了广为人知的抗生素耐药性(resistance)之外,细菌还能对抗生素产生耐受性(tolerance)和持留性(persistence),严重影响抗生素的临床疗效。鸟苷四磷酸(guanosine tetraphosphate, ppGpp)和鸟苷五磷酸(guanosine pentaphosphate, pppGpp) (本文统称ppGpp)是细菌应对营养饥饿等不利环境时产生的"报警"信号分子,其能够在全局水平调控基因的表达,使细菌适应不利的环境。越来越多的研究表明,ppGpp与细菌应对抗生素胁迫密切相关。基于此,本文综述了细菌中ppGpp的合成与水解及其作用机制,并重点阐述了ppGpp介导抗生素胁迫应答的分子机制,以期为新型抗生素的开发提供新思路。     

Sexual development in early- and late-maturing Bos indicus and Bos indicus x Bos taurus crossbred bulls in Brazil

Two experiments were conducted to evaluate sexual development in early- and late-maturing Nelore (Bos indicus) and Canchim (3/8 Bos indicus x 5/8 Bos taurus crossbred) bulls and to determine predictors of sexual precocity, and pubertal and maturity status. In Experiment 1, 12 Nelore bulls where examined from 300 to 900 days of age. Puberty was characterized by an ejaculate containing > or =50 million sperm with > or =10% motile sperm, and maturity by an ejaculate containing > or =70% morphologically normal sperm. In Experiment 2, 28 Canchim bulls where examined from 295 to 488 days of age and puberty was characterized by an ejaculate containing > or =30% motile sperm. In both experiments, bulls were classified as early- or late-maturing based on age at puberty. Early-maturing bulls were younger (P < 0.05) than late-maturing bulls at puberty (527 days versus 673 days in Experiment 1 and 360 days versus 461 days in Experiment 2) and at maturity (660 days versus 768 days in Experiment 1). In general, early-maturing bulls were heavier and had greater scrotal circumference (SC), testes, and testicular vascular cone diameter than late-maturing bulls during the experimental period. Scrotal circumference adjusted for 365 days of age was a good predictor of sexual precocity; minimum yearling SC of 19 and 24 cm for Nelore and Canchim bulls, respectively, had the best predictive values. Early-maturing bulls were lighter and had smaller SC at puberty than late-maturing bulls; therefore, sexual precocity was not related to the attainment of a threshold body weight or testicular size earlier, but to lower thresholds in early-maturing bulls. When predictors of pubertal status were evaluated, SC had the best sensitivity/specificity relationship in Nelore bulls, and high sensitivity and specificity in Canchim bulls. When predictors of sexual maturity were evaluated in Nelore bulls, age, weight, and SC had similar sensitivity, specificity, and predictive values. At puberty, approximately 60% of the sperm present in the ejaculate were morphologically defective. Changes in semen quality after puberty in Nelore bulls were characterized by increased motility and proportion of morphologically normal sperm, with a decrease in the proportion of major sperm defects. In conclusion, early-maturing bulls were more developed in the pre-pubertal period and attained puberty at earlier stages of body and testicular development than late-maturing bulls. Yearling SC could be used to select bulls for sexual precocity and SC was the best predictor of pubertal status. Age, weight, and SC were equally good predictors of sexual maturity in B. indicus bulls.     

Effects of prior exposure to antibiotics on bacterial adaptation to phages

Understanding adaptation to complex environments requires information about how exposure to one selection pressure affects adaptation to others. For bacteria, antibiotics and viral parasites (phages) are two of the most common selection pressures and are both relevant for treatment of bacterial infections: increasing antibiotic resistance is generating significant interest in using phages in addition or as an alternative to antibiotics. However, we lack knowledge of how exposure to antibiotics affects bacterial responses to phages. Specifically, it is unclear how the negative effects of antibiotics on bacterial population growth combine with any possible mutagenic effects or physiological responses to influence adaptation to other stressors such as phages, and how this net effect varies with antibiotic concentration. Here, we experimentally addressed the effect of pre‐exposure to a wide range of antibiotic concentrations on bacterial responses to phages. Across 10 antibiotics, we found a strong association between their effects on bacterial population size and subsequent population growth in the presence of phages (which in these conditions indicates phage‐resistance evolution). We detected some evidence of mutagenesis among populations treated with fluoroquinolones and β‐lactams at sublethal doses, but these effects were small and not consistent across phage treatments. These results show that, although stressors such as antibiotics can boost adaptation to other stressors at low concentrations, these effects are weak compared to the effect of reduced population growth at inhibitory concentrations, which in our experiments strongly reduced the likelihood of subsequent phage‐resistance evolution.     

A multi-type branching model with varying environment for bacterial dynamics with postantibiotic effect

A multi-type branching process with varying environment was used to construct a pharmacokinetic/pharmacodynamic (PK/PD) model that captures the postantibiotic effect (PAE) seen in bacterial populations after exposure of antibiotics. This phenomenon of continued inhibition of bacterial growth even after removal of the antibiotic from the growth medium is of high relevance in the context of optimizing dosing regimens. The clinical implication of long PAEs lies in the interesting possibility of increasing the intervals between drug administrations.The model structure is generalizable to most types of antibiotics and is useful both as a theoretical framework for understanding the time properties of PAE and to explore optimal antibiotic dosing regimens. Data from an in vitro study with Escherichia coli exposed to different dosing regimens of cefotaxime were used to evaluate the model.     

Human mesenchymal stromal cells can uptake and release ciprofloxacin,acquiring in vitro anti-bacterial activity

Background aimsTraditional antibiotic therapy is based on the oral or systemic injection of antibiotics that are often unable to stop a deep infection (eg, osteomyelitis). We studied whether or not bone marrow stromal cells (BM-MSCs) are able to uptake and release ciprofloxacin (CPX), a fluoroquinolone considered the drug of choice for the treatment of chronic osteomyelitis because of its favorable penetration into poorly vascularized sites of infection.MethodsHuman bone marrow stromal cells (BM-MSCs) were primed with CPX (BM-MSCsCPX) according to a methodology previously standardized in our laboratory for paclitaxel (PTX). The anti-microbial activity of CPX released from BM-MSCs cells (BM-MSCsCPX-CM) or supernatant from cell lysate (BM-MSCsCPX-LYS) was evaluated by agar dilution and microdilution methods on three bacterial strains (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa). To investigate whether or not primed cells (BM-MSCsCPX) were able to directly act on the bacterial growth, co-colture was performed by mixing E. coli suspension to an increasing number of BM-MSCsCPX. The anti-bacterial activity was determined as number of BM-MSCsCPX that completely inhibited bacterial growth.ResultsThe results demonstrated that BM-MSCsCPX are able to uptake and then release CPX in the conditioned medium. The loaded antibiotic maintains its active form throughout the process as tested on bacteria.ConclusionsOur findings suggest that CPX-loaded MSCs may represent an important device for carrying and delivering CPX (and perhaps other antibiotics) into infected deep microenvironments; they could be used for local application and by systemic infusion when their homing capacity into the bone is cleared.     

The role of antibiotics and antibiotic resistance in nature

Investigations of antibiotic resistance from an environmental prospective shed new light on a problem that was traditionally confined to a subset of clinically relevant antibiotic‐resistant bacterial pathogens. It is clear that the environmental microbiota, even in apparently antibiotic‐free environments, possess an enormous number and diversity of antibiotic resistance genes, some of which are very similar to the genes circulating in pathogenic microbiota. It is difficult to explain the role of antibiotics and antibiotic resistance in natural environments from an anthropocentric point of view, which is focused on clinical aspects such as the efficiency of antibiotics in clearing infections and pathogens that are resistant to antibiotic treatment. A broader overview of the role of antibiotics and antibiotic resistance in nature from the evolutionary and ecological prospective suggests that antibiotics have evolved as another way of intra‐ and inter‐domain communication in various ecosystems. This signalling by non‐clinical concentrations of antibiotics in the environment results in adaptive phenotypic and genotypic responses of microbiota and other members of the community. Understanding the complex picture of evolution and ecology of antibiotics and antibiotic resistance may help to understand the processes leading to the emergence and dissemination of antibiotic resistance and also help to control it, at least in relation to the newer antibiotics now entering clinical practice.     

细菌抗生素耐药机制研究进展

随着抗生素的广泛使用,细菌对抗生素的适应性越来越普遍。本研究对细菌获得性抗药性的形成、传递机制以及细菌耐药机制进行综述;同时阐述药物间相互作用在抗药性方面的应用,指出药物间协同作用在降低细菌抗药性方面的优势与弊端,同时提出药物拮抗作用在降低细菌抗药性方面的应用前景,旨在为寻找更加合理的用药方法提供理论依据。     

Bacteriophages for the treatment of Pseudomonas aeruginosa infections

Bacteriophages were first identified in 1915 and were used as antimicrobial agents from 1919 onwards. Despite apparent successes and widespread application, early users did not understand the nature of these agents and their efficacy remained controversial. As a result, they were replaced in the west by chemical antibiotics once these became available. However, bacteriophages remained a common therapeutic approach in parts of Eastern Europe where they are still in use. Increasing levels of antibiotic-resistant bacterial infections are now driving demand for novel therapeutic approaches. In cases where antibiotic options are limited or nonexistent, the pressure for new agents is greatest. One of the most prominent areas of concern is multidrug-resistant Gram-negative bacteria. Pseudomonas aeruginosa is a prominent member of this class and is the cause of damaging infections that can be resistant to successful treatment with conventional antibiotics. At the same time, it exhibits a number of properties that make it a suitable target for bacteriophage-based approaches, including growth in biofilms that can hydrolyse following phage infection. Pseudomonas aeruginosa provides a striking example of an infection where clinical need and the availability of a practical therapy coincide.     

A meta-analysis of prophylactic antibiotics in head and neck surgery.

Although it is generally agreed that prophylactic antibiotics are necessary for the prevention of postoperative wound infection, the choice of antibiotic regimen is controversial. In an attempt to determine the most effective antibiotic regimen, a meta-analysis of published clinical trials of prophylactic antibiotics for head and neck surgery was undertaken. The meta-analysis revealed a relative difference in infection rates of 43.7 percent in favor of the use of antibiotics versus placebo, of 8.3 percent in favor of multiple antibiotics versus a single antibiotic, of 13.7 percent in favor of multiple antibiotics versus cefazolin, and of 4.1 percent in favor of multiple-day prophylaxis versus single-day prophylaxis. This meta-analysis suggests that a 1-day course of clindamycin may be the most effective prophylactic antibiotic regimen for head and neck surgery.     

动态监测血清降钙素原水平在优化全身性感染患者抗菌治疗策略中的价值

目的:评估动态监测血清降钙素原水平(PCT)在优化全身性感染患者抗菌治疗策略中的价值。方法:选取2015年4月~2015年12月全身性感染患者85例,随机分为常规组42例和PCT组43例。常规组按照《抗菌药物临床应用指导原则(2015年版)》决定抗生素疗程;PCT组在抗生素治疗后第3、5、7、10、14 d监测血清PCT水平,若PCT0.25 ng/mL停用抗生素、PCT≥0.25 ng/mL继续使用抗生素。分别比较两组患者间一般情况、传统全身炎症性反应指标及抗生素使用的种类、时间、费用以及预后的差异。结果:两组患者间治疗前后传统全身炎症性反应指标无明显差异(P0.05);两组患者间常用的抗生素种类并无明显统计学差异(P0.05);PCT组患者抗生素使用的天数为(9.9±3.9)d,明显少于常规组的(13.9±5.2)d,差异有统计学意义(P0.05);PCT组患者抗生素日均费用为(422.39±139.9)元,明显低于常规组的(514.78±155.2)元,差异有统计学意义(P0.05);两组患者间停用抗生素后14天后全身感染复发率以及28天病死率无明显统计学差异(P0.05)。但PCT组患者总住ICU时间明显少于常规组,差异有统计学意义(P0.05)。结论:动态监测血清PCT水平在优化全身性感染患者抗菌治疗策略中具有重要价值。     

Modified antibiotics-methylated ampicillin and ethylated ampicillin-inhibit growth of ampicillin-resistant strain of bacteria

Bacterial resistance to antibiotics is a significant problem in health facilities and results in higher costs for health care and increased fatalities due to infection. The work presented here suggests that antibiotic molecular structure can be altered in a selected manner, which will revive the bacterial growth inhibiting capability. A bacterial strain PKK3535(DH1), which is resistant to the antibiotic ampicillin, was found to be highly growth inhibited by these altered forms of ampicillin when tested in tissue culture. The level of growth inhibition of bacterial strain PKK3535(DHI) was greater than 50%, for both molecular variants of ampicillin that were investigated. The bacteria strain used for testing was a clinical isolate obtained from the University Hospital of the University of Nebraska, Omaha. These two antibiotic variants were methylated ampicillin and ethylated ampicillin. The synthetic procedure for generating these variants is presented as well as the molecular structure. The methylated and ethylated ampicillin were found to be stable at 0 degrees C for many weeks, were somewhat less soluble than normal ampicillin, but dissolved in LB plate media. The resistant bacteria strain was plated onto LB media with altered ampicillin and profound inhibition of bacteria growth was seen within the first 24 hours of incubation. These molecular variants of ampicillin provide evidence of a means to combat the proliferation of resistant bacterial strains. The molecular alteration of antibiotics may provide a suitable means to study and combat the appearance of antibiotic-resistant bacteria.     

Ecological Application of Antibiotics as Respiratory Inhibitors of Bacterial Populations

Two terregenous and four marine bacterial isolates were treated with six antibiotics and antibiotic combinations. Comparisons made between responses of cells in early and late logarithmic and stationary growth phases indicated variable sensitivity to the agents. Bacteria in stationary and late log-phase cultures exhibited the greatest resistance, whereas the early log-phase cells exhibited greatest antibiotic susceptibility. We conclude that the tested antibiotics cannot be used for ecological purposes to delineate bacterial respiration in mixed microbial communities.     

In vitro antibiotic susceptibility of bacteria isolated from EUS-affected fishes in India

AIMS: Twelve antibiotics were evaluated for in vitro sensitivity against 16 bacterial strains isolated from surface lesions of fishes affected with epizootic ulcerative syndrome (EUS). METHODS AND RESULTS: Disc diffusion assay in Mueller-Hinton agar showed that the pseudomonads and aeromonads were mainly resistant to penicillin, ampicillin and erythromycin. Additionally, some were resistant to gentamycin and amoxycillin. However, resistance towards antibiotics previously recommended for EUS treatment, such as oxytetracycline and chloramphenicol, was not observed. Four aeromonads and two pseudomonads were found to induce ulcers when injected intramuscularly in healthy Anabas testudineus. CONCLUSIONS: All six pathogenic isolates were sensitive towards oxytetracycline, chloramphenicol and nalidixic acid. Oxytetracycline seems to be an effective antibiotic, and further investigations to determine the mode of treatment and dose appear to be worthwhile.