The Formation, Persistence, and Resistance to Disinfectant of the Erysipelothrix piscisicarius Biofilm

Erysipelothrix piscisicarius is an emergent pathogen in fish aquaculture, particularly in the ornamental fish trade. Very little is known on the biology of this pathogen; however, the recurrence of infection and disease outbreaks after removing the fish from a system and disinfecting the tank suggest its environmental persistence. Moreover, biofilm lifestyle in E. piscisicarius has been suspected but not previously shown. The purpose of this study was to investigate the formation of biofilms on an abiotic surface in Erysipelothrix spp. We used hydroxyapatite-coated plastic pegs to demonstrate the attachment, growth, and persistence of E. piscisicarius on abiotic surfaces in both fresh and marine environments and to investigate the susceptibility of this pathogen to different disinfectants that are used in the aquaculture industry. E. piscisicarius formed biofilms that persisted significantly longer than planktonic cells did in both freshwater and saltwater over a period of 120 h (P = 0.004). The biofilms were also more resistant to disinfectants than the planktonic cells were. Hydrogen peroxide was the most effective disinfectant against E. piscisicarius, and it eradicated the biofilms and planktonic cells at the recommended concentrations. In contrast, Virkon and bleach were able to eradicate only the planktonic cells. This information should be taken into consideration when developing biosecurity protocols in aquaculture systems, aquariums, and private collections.

Production of bacteriophage-encoded endolysin, LysP11, in Nicotiana benthamiana and its activity as a potent antimicrobial agent against Erysipelothrix rhusiopathiae

KEY MESSAGE

We produced a biologically active phage-encoded endolysin, LysP11, in N. benthamiana. Plant-produced LysP11 exhibited robust antimicrobial activity against E. rhusiopathiae, and C-terminal domain of LysP11 bound specifically to E. rhusiopathiae. Bacterial resistance to antibiotics, a serious issue in terms of global public health, is one of the leading causes of death today. Thus, new antimicrobial agents are needed to combat pathogens. Recent research suggests that bacteriophages and endolysins derived from bacteriophages are potential alternatives to traditional antibiotics. Here, we examined the antimicrobial activity of LysP11, which is encoded by Propionibacterium phage P1.1 and comprises an N-terminal amidase-2 domain and a C-terminal domain with no homology to other bacteriophage endolysins. LysP11 was produced in Nicotiana benthamiana (N. benthamiana) using an Agrobacterium-mediated transient expression strategy. LysP11 was purified on microcrystalline cellulose-binding resin after attachment of the Clostridium thermocellum-derived family 3 cellulose-binding domain as an affinity tag. The affinity tag was removed using the small ubiquitin-related modifier (SUMO) domain and SUMO-specific protease. Plant-produced LysP11 showed strong antimicrobial activity toward Erysipelothrix rhusiopathiae (E. rhusiopathiae), mediated via lysis of the cell wall. Lytic activity was optimal at pH 8.0-9.0 (37 °C) and increased at higher concentrations of NaCl up to 400 mM. Furthermore, the C-terminal domain of LysP11 bound specifically to the E. rhusiopathiae cell wall. Based on these results, we propose that LysP11 is a potential candidate antimicrobial agent against E. rhusiopathiae.

Presence and new genetic environment of pleuromutilin-lincosamide-streptogramin A resistance gene lsa(E) in Erysipelothrix rhusiopathiae of swine origin

Erysipelothrix rhusiopathiae is a Gram-positive bacillus that causes erysipelas in swine. In recent years, erysipelas infection among swine in China has been increasing. A combined resistance phenotype to pleuromutilins, lincosamides, and streptogramin A (PLSA phenotype) was found in some E. rhusiopathiae isolates. The aim of this study was to identify the resistance genes responsible for the PLSA phenotype in E. rhusiopathiae strains and to map the genetic environment of the identified resistance gene. A total of 46 E. rhusiopathiae isolates from 31 pig farms in China were studied. Minimum inhibitory concentrations (MICs) of 11 antimicrobial agents were determined by broth microdilution method. Seven were highly resistant to tiamulin (MICs 32 μg/ml) and clindamycin (MICs 64 μg/ml). Resistance genes responsible for the PLSA phenotype were screened by PCR. The lsa(E), spw, lnu(B), aadE and aphA3 genes were detected in strains had the PLSA phenotype, whereas none was detected in susceptible strains. The genetic environment of lsa(E) gene was determined by whole-genome sequencing and overlapping PCR assays. A novel multiresistance gene cluster, orf1-aadE-apt-spw-lsa(E)-lnu(B)-rec-orf2-orf1-aadE-sat4-aphA3, was found. Horizontal gene transfer experiments and whole-genome sequencing suggested that the lsa(E)-carrying multiresistance gene cluster was located in the chromosome. This is the first molecular characterization of PLSA resistance in E. rhusiopathiae. The lsa(E), spw and lnu(B) genes were found in E. rhusiopathiae for the first time. A novel lsa(E)-carrying multiresistance gene cluster was found. The location of lsa(E) in different gene cluster facilitates its persistence and dissemination.

Comparison of bacterial diversity in wheat bran and in the gut of larvae and newly emerged adult of Musca domestica (Diptera: Muscidae) by use of ethidium monoazide reveals bacterial colonization

The objective of the current study is to investigate the bacterial colonization within the gut of the house fly, Musca domestica L. (Diptera: Muscidae), at the larval stage and the bacterial community of the gut of the house fly at the newly emerged adult stage. After using ethidium monoazide to inhibit recovery of nucleic acids from dead bacteria, three polymerase chain reaction (PCR)-amplified 16S rDNA libraries from wheat bran, larvae, and newly emerged adults was constructed, analyzed, and compared. In total, 24, 11, and four phylotypes in the 16S rDNA libraries of wheat bran and the gut of larvae and adults, respectively, were found and assigned to three phylogenetic phyla of the domain Bacteria: Firmicutes, Proteobacteria, and Bacteroidetes. In the wheat bran library, 76% of the total number of sequences were affiliated to the genera Pseudomonas, Halomonas, Providencia, and Ignatzschineria. The three genera Morganella (79.05%), Providencia (8.78%), and Ignatzschineria (9.46%) dominated the library of the larval gut. Compared with the wheat bran library, the relative abundance of Morganella morganii (Winslow) was significantly higher (79.05 versus 0.8%), whereas that of Ignatzschineria larvae and of Providencia spp. was similar. These results demonstrate that M. morganii, Providencia spp., and I. larvae colonized the gut of the house fly larvae. Live bacteria of M. morganii, Providencia spp., and Proteus spp. were found in the gut of newly emerged adults. Therefore, the bacteria M. morganii and Providencia spp. colonized the larval gut could survive in the gut from larval metamorphosis to adult eclosion of the house fly.

The evaluation of trifloxystrobin in protection of Calendula officinalis (Pot marigold) against Erysiphe cichoracearum DC

The aim of the two-years field's examinations was the evaluation of the fungicide Zato 50 WG (biologically active substances BAS--trifloxystrobin 50%) in protection of Calendula officinalis (Pot marigold) against Erysiphe cichoracearum. Mentioned fungicide was applied at three concentrations: 0.1, 0.15 and 0.2%. As the standard fungicide Amistar 250 SC (biologically active substances BAS - azoxystrobin 250 g/dm3) was used. In every year of research work the four protective treatments were carried out. The estimation of infestation degree of Calendula officinalis leafs by the Erysiphe cichoracearum was made 5 times. Before each treatment four analysis were done, whereas the last analysis--the fifth one was executed after 10 days from the last protective spraying. According to the results, it was found that investigated preparations significant reduced the mean infestation degree of Calendula officinalis leafs by the Erysiphe cichoracearum compared to the control. The results pointed, that in protection of the mentioned plant by the powdery mildew the 0.2% dose of Zato 50WG showed the best suitability.

[Fatal mitral valve endocarditis by Erysipelothrix rhusiopathiae]

A fatal case of Erysipelothrix rhusiopathiae mitral valve endocarditis is described in a 45 years old male, with a history of chronic alcohol abuse and without animals contact. He presented intermittent fever, polyarthralgia, weight loss, and low back pain. In blood cultures (2 bottles), gram-positive pleomorphic rods grew after 48 hours of incubation. The subculture on blood agar media showed a small, alpha-hemolytic colony, catalase and oxidase negative, PYR and LAP positive and the production of H2S in triple sugar iron agar, was demonstrated. The isolate was initially identified as E. rhusiopathiae, and confirmed by API Coryne (BioMérieux). On the basis of these findings and a transthoracic echocardiogram, an endocarditis was confirmed. Intravenous ampicillin and gentamicin treatment was initiated. The patient became afever, nevertheless he died on day 19 after admission as a consequence of acute pulmonary edema. Susceptibility testing by E-test showed that the microorganism was resistant to vancomycin and gentamicin, and susceptible to penicillin and cefotaxime. We emphasize the importance to consider the isolates of gram-positive pleomorphic rods, catalase and oxidase negative, and the addition of H2S production test in TSI medium. Vancomycin-resistance helps in the identification, and to establish the correct antimicrobial therapy. Although E. rhusiopathiae is usually reported as an occupational pathogen, the contact with pigs and other farm animals may be underestimated.

Identification of the tetracycline resistance gene, tet(M), in Erysipelothrix rhusiopathiae

This is the first report to demonstrate the presence of tet(M) in naturally occurring isolates of tetracycline-resistant Erysipelothrix rbusiopathiae, which causes swine erysipelas. The tet(M) gene was isolated from E. rhusiopathiae strain KY5-42. The nucleotide and the deduced amino acid sequence were 99% identical to the tet(M) gene from Enterococcus faecalis. The gene was necessary and sufficient for the expression of tetracycline resistance in Escherichia coli. The presence of the tet(M) gene in the 114 tetracycline-resistant E. rhusiopathiae isolates from diseased pigs was detected by the polymerase chain reaction assay. The specific amplified DNA fragment was obtained from all 114 tetracycline-resistant strains. It was suggested that the tet(M) gene was widely present in the field isolates of E. rhusiopathiae resistant to tetracycline.

Susceptibility of Erysipelothrix rhusiopathiae to antimicrobial agents and home disinfectants

AIM

Erysipelothrix rhusiopathiae causes the occupationally-related infection erysipeloid in humans, and may be responsible for infections in lobster fishermen in Western Australia. There are little recent data pertaining to antimicrobial susceptibility, or susceptibility to disinfectants that might be used in the environment. The aim of this study was to determine the susceptibility of E. rhusiopathiae from human, animal and environmental sources to various antimicrobial agents and disinfectants.

METHODS

The susceptibility of 60 E rhusiopathiae isolates was determined using a recommended agar dilution procedure. Susceptibility to disinfectants was achieved using a broth microdilution method.

RESULTS

Penicillin and ceftriaxone, with low minimum inhibitory concentrations (MICs) (MIC90 0.03 mg/l and 0.125 mg/l, respectively), remained active against E. rhusiopathiae and should continue to be recommended for treatment. Ciprofloxacin MICs were particularly low (MIC90 0.06 mg/l), offering an alternative agent for the penicillin allergic patient. Erysipelothrix rhusiopathiae is still resistant to vancomycin (MIC90 64 mg/l), highlighting the importance of early diagnosis of E. rhusiopathiae infection in cases of endocarditis. In addition, 31 E. rhusiopathiae isolates were tested against several commercially available home disinfectants. Most were effective in killing E. rhusiopathiae with minimum bactericidal concentrations of 0.001% for Pine O Cleen, and 0.03% for Domestos, Linely and the Wheelie Bin Phenyl Cleanser.

CONCLUSIONS

There appeared to be no new emergence of antibiotic resistance in E. rhusiopathiae. Various disinfectants could be used following mechanical cleaning of work environments, such as fishing boats, and equipment, to reduce the risk of infection with E. rhusiopathiae.

Antimicrobial susceptibilities of Erysipelothrix rhusiopathiae isolated from pigs with swine erysipelas in Japan, 1988-1998

The susceptibility to 21 antimicrobial agents of 214 strains of Erysipelothrix rhusiopathiae isolated from pigs affected with swine erysipelas in Japan between 1988 and 1998 was determined. Ampicillin, cloxacillin, benzylpenicillin, ceftiofur, tylosin, enrofloxacin and danofloxacin were the most active agents [minimum inhibitory concentrations (MICs); < or = 0.025-0.78 microgram/ml], followed by cefazolin, virginiamycin, tiamulin, chloramphenicol, florphenicol and oxolinic acid (MICs; 0.1-25 micrograms/ml). Activity was poor or absent with kanamycin and sulfadimethoxine. Strains resistant to dihydrostreptomycin, erythromycin, clindamycin, lincomycin, oxytetracycline and doxycycline were detected. The susceptibilities to dihydrostreptomycin and oxytetracycline tended to decrease. Investigation of the differences in antimicrobial susceptibility of the 214 strains according to their serotypes, sources, isolation years and regions, showed that the strains resistant to dihydrostreptomycin were most frequently found in the strains of serotype 1a and in strains from septicaemic cases. Strains resistant to oxytetracycline were detected in all serotypes and all sources, and most of the strains resistant to erythromycin were detected in the strains of serotype 2. The frequency of strains resistant to dihydrostreptomycin gradually increased from 1988 to 1996, but then decreased between 1997 and 1998. The frequency of strains resistant to oxytetracycline was remained more than 38% from 1988 to 1998. It was suggested that the strains resistant to dihydrostreptomycin and oxytetracycline were distributed over almost all districts of Japan.

In vitro susceptibility of porcine respiratory pathogens to tilmicosin

Bacterial isolates obtained from swine with various clinical diseases were tested for susceptibility to tilmicosin by minimum inhibitory concentration (MIC) and Kirby-Bauer disk diffusion tests using National Committee on Clinical Laboratory Standards methodology. The tilmicosin MIC90 was < or =0.125 microg/ml for Erysiopelothrix rhusiopathiae, < or = 1 microg/ml for Haemophilus parasuis isolates, 8 microg/ml for Actinobacillus suis and Pasteurella multocida type A, 16 microg/ml for toxigenic and nontoxigenic P. multocida type D, 64 microg/ml for Bordetella bronchiseptica, and >128 microg/ml for Staphylococcus hyicus and Streptococcus suis. The results of disk diffusion testing matched well with the MIC results for each pathogen. This in vitro survey of tilmicosin activity against various swine isolates suggests that further clinical evaluation of tilmicosin in swine may be warranted for disease associated with E. rhusiopathiae, H. parasuis, and A. suis but not B. bronchiseptica, S. suis, or S. hyicus.

Fatal outcome of Erysipelothrix rhusiopathiae bacteremia in a patient with oropharyngeal cancer

Bacteremia due to Erysipelothrix rhusiopathiae is rare; the most common presentation reported in the literature is endocarditis. We report a 32-year-old man with oropharyngeal cancer who developed aspiration pneumonia and E. rhusiopathiae bacteremia, and presented with fever, chills, dyspnea, and productive cough with purulent sputum. Despite treatment with amoxicillin/clavulanate and nutritional support for 9 days, he died of respiratory failure. He had no clinical evidence of endocarditis. He had no history of animal or occupational exposure, and might have been colonized with E. rhusiopathiae in the oral cavity, followed by aspiration pneumonia and bacteremia. A fatal outcome in a patient with bacteremia due to E. rhusiopathiae without endocarditis is rare.

Serovar, pathogenicity and antimicrobial susceptibility of erysipelothrix rhusiopathiae isolates from farmed wild boars (Sus scrofa) affected with septicemic erysipelas in Japan

Six strains of Erysipelothrix rhusiopathiae were isolated from farmed wild boars with acute septicemic erysipelas during the period from 1983 to 1998 in Japan. All isolates belonged to serovar 1a or 2 (predominant serovars in swine). The 50 per cent lethal dose values of those isolates ranged from 10(1.3)to 10(6.2)colony forming units in mice. In swine, all isolates were virulent, capable of inducing localized or generalized urticarial lesions after intradermal inoculation. All of the isolates were resistant to oxytetracycline and/or dihydrostreptomycin. These observations suggest that E. rhusiopathiae strains isolated from wild boars may have aetiological significance in swine erysipelas.

Measurement of antibacterial activities of T-2 toxin, deoxynivalenol, ochratoxin A, aflatoxin B1 and fumonisin B1 using microtitration tray-based turbidimetric techniques

Various mycotoxins were tested for their antibacterial activity by evaluating growth delays using a fully automated microturbidmetric method. Ten different strains of the genera Escherichia, Streptococcus, Staphylococcus, Yersinia, Salmonella, Erysipelothrix and Lactobacillus were used as test micro-organisms. T-2 toxin, deoxynivalenol (DON), ochratoxin A (OTA), aflatoxin B1 (AFB1) and fumonisin B1 (FB1) were used as representative mycotoxins. The inhibitory effect in vitro was defined as the difference between the growth rate without mycotoxins and the growth rate in the presence of a mycotoxin. Among the tested strains, Streptococcus agalactiae was found to be sensitive to all the toxins, with the exception of OTA. T-2 toxin and FB1 were the most effective in slowing down the growth of Staphylococcus aureus. AFB1 affected the growth of Yersinia enterocolitica. The growth rate of Escherichia coli and Salmonella infantis was decreased by FB1. Among the bacterial strains used in this study, only the growth of Erysipelothrix rhusiopathiae was inhibited by OTA. Thus, using appropriate tester strains it should be possible to set up a broad-range microtubidimetry assay for individual mycotoxin screening in vitro. We concluded that the microtitration technique provides a rapid, convenient and high-throughput capacity system to analyse bacteria-mycotoxin interactions.

Effects of tamoxifen, melatonin, coenzyme Q10, and L-carnitine supplementation on bacterial growth in the presence of mycotoxins

The involvement of toxic oxygen intermediates in the bacteriostatic effects of mycotoxins (T-2 toxin, deoxynivalenol, ochratoxin A, aflatoxin B1, and fumonisin B1) was investigated by producing bacterial growth curves using turbidimetry assays in the presence and absence of oxygen radical-scavenging substances. The strains used in this study included Escherichia coli (FT 101), Streptococcus agalactiae (FT 311, FT 313, FT 315), Staphylococcus aureus (FT 192), Yersinia enterocolitica (FT 430), Salmonella infantis (FT 431), Erysipelothrix rhusiopathiae (FT 432), Lactobacillus plantarum (FT234) and Lactobacillus casei (FT 232). Tamoxifen, melatonin, l-carnitine and coenzyme Q10 were used as radical scavengers against oxygen toxicity to the strains studied. Tamoxifen was the most effective in inhibiting bacterial growth when used at a high concentration, whereas melatonin and l-carnitine were less effective. A combination of l-carnitine and coenzyme Q10 provided better protection against oxygen toxicity caused by the mycotoxins growth than they did individually. It was concluded that oxygen radicals are involved in the killing of bacteria and that there is endogenous formation of toxic oxygen products by mycotoxins. The objective of this study was to determine whether the antioxidants were able to counteract the toxic effects of the mycotoxins. The data obtained indicate that bacterial growth can be inhibited especially by T-2 toxin, aflatoxin B1 and ochratoxin A and that this effect can be partially counteracted by antioxidants such as coenzyme Q10 plus l-carnitine.

Persistent bacteremia with Erysipelothrix rhusiopathiae in a hospitalized patient

A patient with a history of alcohol abuse and pancreatitis presented with a pleural effusion resulting from a fistula between the pancreatic duct and left pleural space. Two weeks into her hospitalization, fever and persistent bloodstream infection with Erysipelothrix rhusiopathiae and Candida albicans developed. The patient had no history of exposure to animals. To our knowledge this is the first report of an E. rhusiopathiae infection presenting during hospitalization. This case suggests the possibility of a carrier state of infection and illustrates that a high index of suspicion is necessary for identification of unusual pathogens in hospitalized patients.

Detection of plasmid DNA in Erysipelothrix rhusiopathiae isolated from pigs with chronic swine erysipelas

Forty-three strains of Erysipelothrix rhusiopathiae, isolated from pigs with chronic swine erysipelas, were examined for the presence of plasmid DNA by agarose gel electrophoresis and electron microscopy. Seven of these strains were found to contain plasmids of which number were varied from 1 to 6. The plasmids ranged from 1.4 to 86 kb in size. This is the first reported evidence for plasmid DNA in E. rhusiopathiae. The functions of the plasmids are unknown at present.

An investigation of bacterial causes of arthritis in slaughter hogs

Joints from 153 arthritic and 80 normal slaughter hogs were examined by culture for presence of bacteria. Although none of the normal joints yielded bacteria, 37% of the disease joints were positive for bacterial growth. Of 67 bacterial isolates obtained, 45% were Erysipelothrix rhusiopathiae. Occurrence of other bacteria in order of their frequency was Streptococcus suis (16%), Actinomyces pyogenes (10%), Mycoplasma spp. including 3 M. hyorhinis isolates (7%), staphylococci (7%), Streptococcus spp. (6%), and organisms of uncertain significance (7%).

Antimicrobial susceptibilities of Erysipelothrix rhusiopathiae

The in vitro susceptibilities of 10 isolates of Erysipelothrix rhusiopathiae to 16 antimicrobial agents were determined. Penicillin and imipenem were the most active agents, followed by piperacillin, cefotaxime, ciprofloxacin, pefloxacin, and clindamycin. Some resistance was observed with erythromycin, tetracycline, and chloramphenicol. Activity was poor or absent with vancomycin, teicoplanin, daptomycin, trimethoprim-sulfamethoxazole, gentamicin, and netilmicin.

Resistance to vancomycin and teicoplanin: an emerging clinical problem

Vancomycin and teicoplanin are glycopeptides active against a wide range of gram-positive bacteria. For 30 years following the discovery of vancomycin in 1956, vancomycin resistance was not detected among normally susceptible bacteria recovered from human specimens. Since 1986, however, bacteria resistant to vancomycin or teicoplanin or both have been described. Strains of the genera Leuconostoc, Lactobacillus, Pediococcus, and Erysipelothrix seem inherently resistant to glycopeptides. Species and strains of enterococci and coagulase-negative staphylococci appear to have acquired or developed resistance. There are at least two categories of glycopeptide resistance among enterococci, characterized by either high-level resistance to vancomycin (MIC, greater than or equal to 64 mg/liter) and teicoplanin (MIC, greater than or equal to 8 mg/liter) or lower-level vancomycin resistance (MIC, 32 to 64 mg/liter) and teicoplanin susceptibility (MIC, less than or equal to 1 mg/liter). The two categories appear to have similar resistance mechanisms, although genetic and biochemical studies indicate that they have arisen independently. Among coagulase-negative staphylococci, strains for which vancomycin MICs are up to 20 mg/liter or teicoplanin MICs are 16 to 32 mg/liter have been reported, but cross-resistance between these glycopeptides varies. The selective advantage accorded to glycopeptide-resistant bacteria and the observation that high-level resistance in enterococci is transferable suggest that such resistance may be expected to increase in incidence. Clinicians and microbiologists need to be aware of this emerging problem.

In vitro susceptibility of selected veterinary bacterial pathogens to ciprofloxacin, enrofloxacin and norfloxacin

The minimum inhibitory concentrations (MIC) of ciprofloxacin, enrofloxacin, and norfloxacin were tested for approximately ten clinical isolates of each of Actinobacillus pleuropneumoniae, Actinobacillus suis, Actinomyces pyogenes, Corynebacterium pseudotuberculosis, Erysipelothrix rhusiopathiae, Haemophilus parasuis, Haemophilus somnus, Pasteurella haemolytica, Pasteurella multocida, Rhodococcus equi, Streptococcus equi, Streptococcus suis and Streptococcus zooepidemicus. Ciprofloxacin and enrofloxacin had similar activity and were more active than norfloxacin. All isolates had an MIC of 1.0 microgram/mL or less for ciprofloxacin and enrofloxacin, and these drugs had particularly marked activity against the gram-negative bacteria tested.

Erysipelothrix endocarditis with previous cutaneous lesion: report of a case and review of the literature

This report describes the first documented case of Erysipelothrix rhusiopathiae endocarditis in Latin America. The patient was a 51-years-old male, moderate alcoholic, with a previous history of aortic failure. He was used to fishing and cooking as a hobby and had his left hand wounded by a fish-bone. The disease began with erysipeloid form and developed to septicemia and endocarditis. He was treated with antibiotics and surgery for aortic valve replacement. There are only 46 cases of E. rhusiopathiae endocarditis reported to date. The authors wonder if several other cases might go unreported for lack of microbiological laboratorial diagnosis.

Kill kinetics of the cephalosporin antibiotics cephalexin and cefuroxime against bacteria of veterinary importance

Kill kinetic studies for two cephalosporin antibiotics, cephalexin and cefuroxime were carried out against veterinary strains of Escherichia coli, Pasteurella multocida, Streptococcus suis, Erysipelothrix rhusiopathiae and a laboratory culture of Staphylococcus aureus. In more than 90 per cent of cases a kill of more than 99 per cent was achieved within four hours of antibiotic treatment at concentrations of 2 or 4 micrograms/ml. Although cefuroxime was effective at lower concentrations than cephalexin the rates of kill of the two antibiotics were comparable. The results are discussed in relation to in vivo dosage regimens.

Isolation of Erysipelothrix rhusiopathiae from a 55 year old man and a positive tracing of the infection to chicken-raising premise

Erysipelothrix rhusiopathiae was isolated from the swollen finger of a 55 year old man. The swelling was due to a peck by an infected chicken. Tracing the infection to the chicken-raising premises has proven that the bacterium was present in some of the chicken and manure samples.

Serotype, antimicrobial susceptibility, and pathogenicity of Erysipelothrix rhusiopathiae isolates from tonsils of apparently healthy slaughter pigs

Erysipelothrix rhusiopathiae was isolated from tonsils of 63 (10.5%) of 600 apparently healthy slaughter pigs in the Kanto area of Japan in February and July 1984. The isolation rate was significantly higher during July than in February. Of these 63 isolates, 34 isolates (54.0%) were serotype 7, 20 isolates (31.7%) were serotype 2, 6 isolates (9.5%) were serotype 6, and 1 isolate (1.6%) each was serotype 11, 12, or 16. All isolates of serotypes 2, 6, 11, 12, and 16 were highly virulent for mice, whereas most isolates of serotype 7 were weakly virulent. In swine, all isolates of serotype 2 were highly virulent, capable of inducing generalized urticarial lesions with depression and anorexia. On the other hand, 37 of 43 isolates of serotypes other than 2 induced no clinical signs, and the remaining 6 isolates induced local urticarial lesions at the site of inoculation in swine. The MIC of dihydrostreptomycin ranged from 1.56 to 100 micrograms/ml. All of the dihydrostreptomycin-resistant strains belonged to serotype 2. The high virulence of E. rhusiopathiae strains of serotype 2 harbored in the tonsils suggests a possible role of such strains in the cause of swine erysipelas. In contrast, members of the other nonvirulent or weakly virulent group, mainly serotype 7 strains, were considered to be resident in porcine tonsils.

Antibiotic resistance of Erysipelothrix rhusiopathiae isolated from pigs with chronic swine erysipelas

The susceptibility of 258 isolates of Erysipelothrix rhusiopathiae from slaughtered pigs affected with chronic erysipelas in Japan to antimicrobial agents was determined. A total of 111 (43.0%) strains showed resistance to erythromycin, oleandomycin, oxytetracycline, or dihydrostreptomycin. Plasmids were not detected. This is the first report of resistance of E. rhusiopathiae to these antibiotics.

Observations on the utilization of a selective medium for the isolation of Erysipelothrix rhusiopathiae

A medium containing 3 antibiotics: neomycin, kanamycin and vancomycin for the selective culture of Erysipelothrix rhusiopathiae was studied during various culture tests. It was found that 6 out of 35 previously identified strains of E. rhusiopathiae (17 %) showed no growth or variable growth on the medium. It appeared that the strains with the highest sensitivity for kanamycin were inhibited by the medium. A number of other laboratory strains of microorganisms did not grow on the medium, indicating a good selective effect. Several resistant microorganisms were, however, found in field material. A small number of isolation attempts using tonsils of swine and sheep revealed a very low occurrence (4 % in swine) of E. rhusiopathiae.

In vitro antibacterial activity of moxalactam, a new broad-spectrum semisynthetic antibiotic

The antibacterial activity of moxalactam was studied in vitro against 229 clinical isolates of gram-positive and gram-negative aerobic microorganisms using the agar dilution technique. Mueller-Hinton agar was used as growth medium. The results were compared to those obtained with cefamandole. All isolates of Staphylococcus aureus and Streptococcus pneumoniae were inhibited by moxalactam at a concentration of 8 microgram/ml or less. The concentrations of cefamandole with which the same effect was obtained were 0.5 microgram/ml and 2 microgram/ml respectively. Moxalactam was highly inhibitory against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis and Proteus morganii - 90% of the strains were inhibited by 0.125 microgram/ml. Moxalactam was highly superior against Proteus rettgeri and Pseudomonas aeruginosa, which are usually resistant to cefamandole: the MIC100 and MIC90 were 0.25 microgram/ml and 8 microgram/ml respectively. High sensitivity was found in strains of Salmonella species, nine of which were Salmonella typhi: the MIC90 was < 0.063 microgram/ml versus the eightfold higher concentration of cefamandole. The broad-spectrum activity and unusual MIC patterns of moxalactam - eight or manyfold higher concentrations of cefamandole were needed to inhibit 90% of most gram-negative strains studied - make moxalactam an unusual and promising antibiotic.

Light microscopic investigations on lysozyme- and penicillin-induced morphological changes in Erysipelothrix rhusiopathiae and on propagation of its protoplast type L-form

Although lysozyme and penicillin are different in their molecular action on cell wall murein they produce similar morphological changes in Erysipelothrix rhusiopathiae grown on agar media. 2,000--5,000 micrograms/ml lysozyme and 0.1--2 IU/ml penicillin induce filament formation. Filaments are able to divide in rods, which shows that only cross wall formation and separation are inhibited. Higher doses of lysozyme (10,000 micrograms/ml) and penicillin (less than 1 IU/ml) inhibit cell wall synthesis and induce L-form growth. The propagation of this protoplast type L-form was investigated by microphotographic series in phase contrast microscope during L-form induction and in the stable L-form state. In both cases L-form cells propagate by formation and growth of small granular elements of about 0.2--0.6 micrometers in diameter, which spread in different directions in the agar medium. The multiplication process may be explained by the plasticity and flexibility of the L-form cell and its cytoplasmic membrane and by the structural and functional interaction between the "folded chromosome" and the surrounding cytoplasm.

Electron microscopic studies on altered forms of Erysipelothrix rhusiopathiae obtained under the effect of novobiocin

Altered and L-forms of Erysipelothrix rhusiopathiae were obtained through in vitro and in vivo treatments with novobiocin. Electron microscopic studies were carried out on the changes taking place in the morphology and ultrastructure of strains showing a varying degree of resistance. When lower concentrations of the antibiotic were employed (15, 25, 200, 400 mcg) strongly elongated and threadlike forms were established manifesting characteristic changes in the cell wall and the inner structure. The use of high concentrations of novobiocin (1000 and 2000 mcg) incited the production of L-forms the morphology and ultrastructure of which are dealt with in detail.

In-vitro effect of edta-tris-lysozyme solutions on selected pathogenic bacteria

The in-vitro effect of EDTA-Tris-lysozyme solution on 16 pathogenic bacteria of medical or veterinary importance was determined. Marked decreases in bacterial count occurred with Pseudomonas aeruginosa, Escherichia coli, Moraxella osloensis and Campylobacter fetus, and smaller decreses with Salmonella typhimurium, Shigella boydii, Aeromonas hydrophila, proteus mirabilis, Listeria monocytogenes and Erysipelothrix insidiosa. The test solution had no effect on Klebsiella ozaenae, Brucella canis, Cornynebacterium pyogenes, Coryne, renale, Streptococcus equi and staphylococcus aureus.

L-form induction, morphology, and development in two related strains of Erysipelothrix rhusiopathiae

Two related strains of Erysipelothrix rhusiopathiae, one the parent and the other an L-form revertant, were studied for their propensity or ability to produce L-forms under the influence of penicillin. The parent strain produced L-forms in nutrient solid media in an osmolarity range between 0.85 and 5.0% NaCl concentration whereas the revertant strain did so between 0.5 and 3.0% NaCl concentration. When various hyperosmolar media were tried without penicillin, recovery of L-forms from the revertant strain was optimal at a salt concentration of 2.0%, whereas the parent strain occasionally produced a few L-forms on 3.0% salt medium only. The process of penicillin-induced transformation from bacteria to L-form followed an unusual morphological sequence, beginning with beading of the bacterial body, followed by disintegration into granules from which the L-form colony derived. No large bodies were seen during the initial process of L-form induction, but they evolved later from the original granules and had the potential to reproduce L-type growth. The spontaneous development of L-forms in hyperosmolar media had a different morphological sequence starting with elongation of the bacteria into filaments which later developed polar and central dilatations from which granules and L-type growth developed. The differences in biological behavior between these related bacterial strains suggest that the revertant strain developed new properties, probably of genetic origin. Consequently, the assumption that L-forms revert to the "parent" bacteria may not always be justified. It can be made only after the biological properties of the parent and the revertant organisms have been properly identified.