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PubMed1993

Surface action of gentamicin on Pseudomonas aeruginosa.

The mode of action of gentamicin has traditionally been considered to be at the 30S ribosomal level. However, the inhibition of bacterial protein synthesis alone appears to be insufficient to entirely explain the bactericidal effects. Bacteriolysis is also mediated through perturbation of the cell surface by gentamicin (J.L. Kadurugamuwa, J.S. Lam, and T.J. Beveridge, Antimicrob. Agents Chemother. 37:715-721, 1993). In order to separate the surface effect from protein synthesis in Pseudomonas aeruginosa PAO1, we chemically conjugated bovine serum albumin (BSA) to gentamicin, making the antibiotic too large to penetrate through the cell envelope to interact with the ribosomes of the cytoplasm. Furthermore, this BSA-gentamicin conjugate was also used to coat colloidal gold particles as a probe for electron microscopy to study the surface effect during antibiotic exposure. High-performance liquid chromatography confirmed the conjugation of the protein to the antibiotic. The conjugated gentamicin and BSA retained bactericidal activity and inhibited protein synthesis on isolated ribosomes in vitro but not on intact cells in vivo because of its exclusion from the cytoplasm. When reacted against the bacteria, numerous gentamicin-BSA-gold particles were clearly seen on the cell surfaces of whole mounts and thin sections of cells, while the cytoplasm was devoid of such particles. Disruption of the cell envelope was also observed since gentamicin-BSA and gentamicin-BSA-gold destabilized the outer membrane, evolved outer membrane blebs and vesicles, and formed holes in the cell surface. The morphological evidence suggests that the initial binding of the antibiotic disrupts the packing order of lipopolysaccharide of the outer membrane, which ultimately forms holes in the cell envelope and can lead to cell lysis. It is apparent that gentamicin has two potentially lethal effects on gram-negative cells, that resulting from inhibition of protein synthesis and that resulting from surface perturbation; the two effects in concert make aminoglycoside drugs particularly effective antibiotics.

Bacterial Proteins↗

PubMed1998

Membrane-bound lytic endotransglycosylase in Escherichia coli.

The gene for a novel endotype membrane-bound lytic transglycosylase, emtA, was mapped at 26.7 min of the E. coli chromosome. EmtA is a lipoprotein with an apparent molecular mass of 22kDa. Overexpression of the emtA gene did not result in bacteriolysis in vivo, but the enzyme was shown to hydrolyze glycan strands isolated from murein by amidase treatment. The formation of tetra- and hexasaccharides, but no disaccharides, reflects the endospecificity of the enzyme. The products are characterized by the presence of 1,6-anhydromuramic acid, indicating a lytic transglycosylase reaction mechanism. EmtA may function as a formatting enzyme that trims the nascent murein strands produced by the murein synthesis machinery into proper sizes, or it may be involved in the formation of tightly controlled minor holes in the murein sacculus to facilitate the export of bulky compounds across the murein barrier.

Amino Acid Sequence↗

PubMed1990

Specificity of bovine serum antibody to capsular carbohydrate antigens from Pasteurella haemolytica.

A more complete understanding of the bovine immune response to antigens of Pasteurella haemolytica biotype A, serotype 1, will improve control of bovine respiratory disease (BRD). Sera were obtained from blood samples of calves as they transited the market system of eastern Tennessee and were transported to a feedlot in Texas. The clinical histories and performance data were recorded and compared with serologic findings. The calves underwent a natural challenge of BRD. Serologic and bacteriologic evaluation indicated that P. haemolytica A1 was a significant component of the challenge. Serum antibody titers against P. haemolytica A1 capsular antigens (in enzyme-linked immunosorbent assay and hemolysin-in-gel test) increased by day 15 and continued at high levels through day 56. The animals that remained free of BRD had higher initial serum antibody concentrations than those that succumbed to BRD. The specificity of the immunoglobulin G subclass 1 (IgG1) anticapsular antibody to P. haemolytica A1 increased from day 8 to day 29 as evidenced by a decrease in P. haemolytica A2 absorption inhibition from 60% (day 8) to 15% (day 29). However, IgA, IgG2, and IgM were more serotype specific on both days 8 and 29. There were no significant changes in anti-P. haemolytica A2 antibody titers. Both in vitro complement-dependent bacteriolysis and C3 deposition on the surface of the bacteria increased significantly (P less than 0.01) in a serotype-specific fashion from day 8 to day 29. These calves showed a humoral immune response to capsular polysaccharide antigens of P. haemolytica A1. Such a response may be an important component of immunity to BRD.

Animals↗

PubMed1998

Growth of the stress-bearing and shape-maintaining murein sacculus of Escherichia coli.

To withstand the high intracellular pressure, the cell wall of most bacteria is stabilized by a unique cross-linked biopolymer called murein or peptidoglycan. It is made of glycan strands [poly-(GlcNAc-MurNAc)], which are linked by short peptides to form a covalently closed net. Completely surrounding the cell, the murein represents a kind of bacterial exoskeleton known as the murein sacculus. Not only does the sacculus endow bacteria with mechanical stability, but in addition it maintains the specific shape of the cell. Enlargement and division of the murein sacculus is a prerequisite for growth of the bacterium. Two groups of enzymes, hydrolases and synthases, have to cooperate to allow the insertion of new subunits into the murein net. The action of these enzymes must be well coordinated to guarantee growth of the stress-bearing sacculus without risking bacteriolysis. Protein-protein interaction studies suggest that this is accomplished by the formation of a multienzyme complex, a murein-synthesizing machinery combining murein hydrolases and synthases. Enlargement of both the multilayered murein of gram-positive and the thin, single-layered murein of gram-negative bacteria seems to follow an inside-to-outside growth strategy. New material is hooked in a relaxed state underneath the stress-bearing sacculus before it becomes inserted upon cleavage of covalent bonds in the layer(s) under tension. A model is presented that postulates that maintenance of bacterial shape is achieved by the enzyme complex copying the preexisting murein sacculus that plays the role of a template.

Carbohydrate Sequence↗

PubMed1984

A turbidimetric and electron microscopic study of the effects of several parameters on the lysis of Streptococcus faecalis by lysozyme.

The lytic effect of lysozyme on Streptococcus faecalis ATCC 9790 was studied by spectrophotometry and electron microscopy and it was found to be highly dependent on the ionic strength of the suspending media and on the ratio lysozyme to bacterial cell mass. When 7.2 X 10(8) bacteria/mL are exposed to 0.4 mg/mL of lysozyme in media with low ionic strength, the enzyme is bound in great amounts, as deduced from protein determinations and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS--PAGE); the binding prevents bacteriolysis in spite of the removal of the cell wall. Extensive lysis of S. faecalis could be obtained by reducing the ratio of lysozyme to bacterial cell mass. Stabilization of S. faecalis by lysozyme was also observed when exponential phase cells incubated under conditions that promote spontaneous autolysis (incubation in 0.05 M tris(hydroxymethyl)aminomethane buffer, pH 8.0, ionic strength = 0.01675) do not lyse and do not leak material which absorbs at 260 nm when lysozyme was present at the highest concentration.

Enterococcus faecalis↗

PubMedDate not supplied

In vitro and in vivo antibacterial activities of FK037, a new parenteral cephalosporin.

In vitro and in vivo antibacterial activities of FK037, a new parenteral cephalosporin, were compared with those of cefpirome, ceftazidime and flomoxef. The advantages of in vitro activity of FK037 were as follows: (1) a broad-spectrum antibacterial activity, (2) the most potent activity (MIC90: 25 micrograms/ml) of the cephalosporins tested against highly methicillin-resistant Staphylococcus aureus (H-MRSA), (3) a strong activity against Enterobacter spp. and Citrobacter freundii resistant to the third-generation cephalosporins tested. The MICs of FK037 for 90% of the clinical isolates tested (MIC90s) were 0.012 microgram/ml for Streptococcus pyogenes, 0.05 microgram/ml for Escherichia coli, 0.1 microgram/ml for Streptococcus pneumoniae, 0.2 microgram/ml for Haemophilus influenzae and Proteus mirabilis, 0.39 microgram/ml for Klebsiella pneumoniae, 1.56 micrograms/ml for methicillin-sensitive S. aureus, Proteus vulgaris and Enterobacter aerogenes, 3.13 micrograms/ml for Staphylococcus epidermidis and Moraxella catarrhalis, 6.25 micrograms/ml for C. freundii, 12.5 micrograms/ml for low-level methicillin-resistant S. aureus (L-MRSA), Enterobacter cloacae and Pseudomonas aeruginosa, and 25 micrograms/ml for H-MRSA and Serratia marcescens. FK037 was similar in potency to cefpirome against strains except MRSA, and was superior to ceftazidime and flomoxef against strains except P. vulgaris and/or M. catarrhalis. The increase in MICs of FK037 against 2 L-MRSA strains (2- or 4-fold) was smaller than that of cefpirome and flomoxef (16- to 64-fold) after the third serial culture in the presence of each drug. FK037 was highly bactericidal against S. aureus, E. coli, K. pneumoniae and P. aeruginosa at the MIC or higher. FK037 had a potent protective activity against murine experimental systemic infections due to a wide variety of bacteria. Its protective activity was the strongest among the cephalosporins tested against H-MRSA and Acinetobacter calcoaceticus. Against the other strains, FK037 was as effective as cefpirome and similar or superior to flomoxef and ceftazidime though it was inferior to ceftazidime against P. aeruginosa. Transmission electron microscopic studies revealed that FK037 inhibited septum formation and induced thick cross walls and bacteriolysis at the division sites in MRSA after 4 h incubation.

Animals↗

PubMed1978

Excretion of lipoteichoic acid by group A streptococci. Influence of penicillin on excretion and loss of ability to adhere to human oral mucosal cells.

Group A streptococci were grown in the presence of [2-(3)H]glycerol. Concentrated suspensions of the labeled organisms were incubated with and without penicillin. [(3)H]Glycerol-labeled material accumulated in the supernates in increasing amounts with increasing concentrations of penicillin, ranging from 0 to 50 U/ml. The excretion of labeled material occurred in the absence of nucleic acid synthesis or bacteriolysis indicating that the phenomenon is independent of cell multiplication or decay. The accumulation of label was paralleled by an accumulation of erythrocyte-sensitizing material measured by passive hemagglutination tests for lipoteichoic acid antigen, indicating that a portion of the labeled material possessed the properties of lipoteichoic acid. Culture supernates were fractionated by column chromatography, and the materials obtained were analyzed by electrophoresis on sodium dodecyl sulfate polyacrylamide, thin-layer chromatography, and paper chromatography. The ability of the same materials to bind to human erythrocytes and epithelial cells was tested. The culture supernate contained lipoteichoic acid, deacylated lipoteichoic acid, glycerol phosphate, and free glycerol. Penicillin caused an increase in the amounts of each of the excreted materials. Streptococci that were stimulated with penicillin to lose their lipoteichoic acid (previously shown to mediate adherence of group A streptococci) lost their ability to adhere to buccal mucosal cells, suggesting that penicillin may influence bacterial ecology by mechanisms other than killing sensitive organisms.

Adhesiveness↗

PubMed1983

Detection and partial characterization of antibacterial factor(s) in alveolar lining material of rats.

Intracellular killing of Staphylococcus aureus by alveolar macrophages is known to be enhanced by exposure to alveolar lining material. Because this material may have a role in pulmonary host defenses, we have studied its effect on pneumococci and other nonstaphylococcal organisms. Alveolar lining material from rats caused rapid killing and lysis of pneumococci. The antipneumococcal activity was localized to the surfactant-containing fraction of the fluid and was not affected by trypsin. Phospholipid extracts of the surfactant fraction or purified lamellar bodies killed pneumococci. Lysis of pneumococci by the surfactant fraction appeared to be mediated by a detergent-like activation of pneumococcal autolysin, in that bacteriolysis was prevented by substitution of ethanolamine for choline in pneumococcal cell walls, and a pneumococcal transformant that lacked autolysin was not lysed. The surfactant fraction readily killed pneumococci containing ethanolamine or the autolysin-defective transformant, and studies with tritiated methyl-D-glucose loading and release showed that killing was associated with increased bacterial cell membrane permeability. Bactericidal activity (without lysis) was observed with several nonpneumococcal gram-positive bacteria, including Streptococcus viridans, unspeciated respiratory streptococci, Streptococcus pyogenes, Streptococcus bovis, and Bacillus species. Purified diacylphospholipids had no antibacterial activity, however, a lysophospholipid, palmitoyl lysophosphatidylcholine, had many properties resembling the surfactant-containing fraction of lavage, including autolysin-mediated pneumococcal lysis, altered cell membrane permeability, and antibacterial activity against several gram-positive bacteria.

Animals↗

PubMed1991

Penicillin-binding protein inactivation by human neutrophil myeloperoxidase.

Myeloperoxidase (MPO), H2O2, and chloride comprise a potent antimicrobial system believed to contribute to the antimicrobial functions of neutrophils and monocytes. The mechanisms of microbicidal action are complex and not fully defined. This report describes the MPO-mediated inactivation, in Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, of a class of cytoplasmic membrane enzymes (penicillin-binding proteins, PBPs) found in all eubacteria, that covalently bind beta-lactam antibiotics to their active sites with loss of enzymatic activity. Inactivation of "essential" PBPs, including PBP1-PBP3 of E. coli, leads to unbalanced bacterial growth and cell death. MPO treatment of bacteria was associated with loss of penicillin binding by PBPs, strongly suggesting PBP inactivation. In E. coli, PBP inactivation was most rapid with PBP3, where the rate of decline in binding activity approximated but did not equal loss of viability. Changes in E. coli morphology (elongation), observed just before bacteriolysis, were consistent with early predominant inactivation of PBP3. We conclude that inactivation of essential PBPs is sufficient to account for an important fraction of MPO-mediated bacterial action. This feature of MPO action interestingly recapitulates an antibacterial strategy evolved by beta-lactam-producing molds that must compete with bacteria for limited ecologic niches.

Anti-Bacterial Agents↗

PubMed2006

Bacteriophage endolysins as a novel class of antibacterial agents.

Endolysins are double-stranded DNA bacteriophage-encoded peptidoglycan hydrolases produced in phage-infected bacterial cells toward the end of the lytic cycle. They reach the peptidoglycan through membrane lesions formed by holins and cleave it, thus, inducing lysis of the bacterial cell and enabling progeny virions to be released. Endolysins are also capable of degrading peptidoglycan when applied externally (as purified recombinant proteins) to the bacterial cell wall, which also results in a rapid lysis of the bacterial cell. The unique ability of endolysins to rapidly cleave peptidoglycan in a generally species-specific manner renders them promising potential antibacterial agents. Originally developed with a view to killing bacteria colonizing mucous membranes (with the first report published in 2001), endolysins also hold promise for the treatment of systemic infections. As potential antibacterials, endolysins possess several important features, for instance, a novel mode of action, a narrow antibacterial spectrum, activity against bacteria regardless of their antibiotic sensitivity, and a low probability of developing resistance. However, there is only one report directly comparing the activity of an endolysin with that of an antibiotic, and no general conclusions can be drawn regarding whether lysins are more effective than traditional antibiotics. The results of the first preclinical studies indicate that the most apparent potential problems associated with endolysin therapy (e.g., their immunogenicity, the release of proinflammatory components during bacteriolysis, or the development of resistance), in fact, may not seriously hinder their use. However, all data regarding the safety and therapeutic effectiveness of endolysins obtained from preclinical studies must be ultimately verified by clinical trials. This review discusses the prophylactic and therapeutic applications of endolysins, especially with respect to their potential use in human medicine. Additionally, we outline current knowledge regarding the structure and natural function of the enzymes in phage biology, including the most recent findings.

Animals↗

PubMed2000

Electron-microscopic study of the bactericidal effect of OPB-2045, a new disinfectant produced from biguanide group compounds, against methicillin-resistant Staphylococcus aureus.

The bactericidal effect of OPB-2045, a new disinfectant produced from biguanide group compounds, against methicillin-resistant Staphylococcus aureus (MRSA), MRSA IID 1677, was investigated by transmission electron microscopy. OPB-2045 showed strong bactericidal activity against MRSA. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of OPB-2045 against the test strain were 0.78 and 1.56 microg mL(-1), respectively. The test bacteria were incubated in the presence of OPB-2045 at 1/2 MIC (0.39 microg mL(-1)), 1 MIC (0.78 microg mL(-1)), 2 MIC (1 MBC, 1.56 microg mL(-1)), 4 MIC (2 MBC, 3.13 microg mL(-1)) or 10 MIC (5 MBC, 7.8 microg mL(-1)) at 37 degrees C for 30 s, 3 min, 30 min or 6h. The morphology of the cells was examined by transmission electron microscopy. The cell damage observed after 30-min or 6-h incubation in the presence of OPB-2045 at 1/2 or 1 MIC was the same as that at 2, 4 or 10 MIC. The numbers of damaged MRSA cells increased according to the increase in concentration of added disinfectant, and the image of bacteriolysis was observed, too. After treatment at 1/2 or 1 MIC, a few leaking cells were recognized, but no destroyed cells were found. No morphological changes were observed after treatment at 1 or 2 MIC for 30 s, 3 min or 30 min. When the incubation time was extended to 6 h, morphological changes in the MRSA cells treated at 1 or 2 MIC were observed. When examining the relationship between the numbers of surviving bacteria and the MIC (MBC) values in soybean casein digest broth, no decrease in MRSA cell numbers was recognized in the untreated control or at 1/2 MIC, but a marked decrease in MRSA cell numbers was recognized as the OPB-2045 concentration was increased. The new disinfectant OPB-2045 would make a useful contribution to the medical field for the prevention of infections caused by pathogenic bacteria such as MRSA.

Anti-Infective Agents, Local↗

PubMed2005

Moxifloxacin in experimental Streptococcus pneumoniae cerebritis and meningitis.

Rifampin, a protein synthesis inhibitor, reduced mortality in a mouse model of meningitis compared to bacteriolytic cephalosporin standard therapy. To assess whether moxifloxacin (known to cause a less rapid bacteriolysis than cephalosporins) can similarly reduce mortality, mice infected with Streptococcus pneumoniae by deep intracerebral injection were treated subcutaneously with either 200 mg/kg of moxifloxacin or ceftriaxone every 8 hours for 5 days (n = 49 each). They were then observed for an additional 8 days. Overall mortalities were 35 and 29 in moxifloxacin- and ceftriaxone-treated mice, respectively (p = 0.29). Kaplan-Meier survival analysis also revealed no statistically significant differences (p = 0.32). Moxifloxacin failed to reduce mortality compared to cephalosporin standard therapy.

Animals↗

PubMed1987

Microbiological investigation of cephalosporins.

The most important role of the clinical microbiology laboratory is to advise clinicians in their choice of antimicrobial therapy. While the application of modern laboratory techniques is enabling sensitivity testing to cephalosporins to be performed with increasing precision, the ability to predict accurately clinical efficacy has not improved in parallel. For the cephem group in particular, the present confusion as to the numerical value of breakpoints and their interpretation, and the overuse of 'class testing' are making the task of the clinical microbiologist more difficult. For most purposes, simple disc sensitivity testing of cephems gives sufficient information, and it is simple to carry out, as no special media or growth conditions are required. Further studies are required to answer an outstanding question of great importance, namely, what the clinical prognostic significance is of results of sensitivity testing of 'methicillin-resistant' Staphylococcus aureus and coagulase-negative staphylococci, as these organisms often appear sensitive to cephems in vitro. For the research worker, the cephems provide tools of almost unrivalled power in the investigation of such microbiologically important topics as cell wall synthesis, bacteriolysis, membrane function and various aspects of enzyme regulation and inhibition. Relatively minor changes in the structure of cephem molecules can markedly affect their binding to bacteria, thus allowing probing of the functions of the individual penicillin-binding proteins. In Gram-negative bacteria, membrane function can be selectively changed by the action of subinhibitory concentrations of cephems, as it is intimately connected to the integrity of the peptidoglycan moiety. Induction and derepression of beta-lactamases may be responsible for a new type of bacterial resistance.

Bacteria↗

PubMed1991

Secretory IgA- and IgG-coated bacteria in the nasopharynx of children. An immunofluorescence study.

Bacterial samples were obtained from the posterior wall of the nasopharynx (NPH) of 18 healthy children (age range 1 to 14 years, 10 males, 8 females) and subjected for immunofluorescence studies using fluorescein-labelled goat anti-human IgG and goat anti-human SIgA antibodies. Quantitative and qualitative bacteriological analyses were performed simultaneously. IgG-coated bacteria in the NPH were observed in 1-year-old subjects and opsonized bacteria seemed to increase in numbers and fluorescence intensity with increasing age. SIgA-coated bacteria appeared later, and intensely fluorescing bacteria were not seen until the age of 3 to 6 years. Thirteen out of the 18 children harboured middle ear pathogens in the NPH, but generally speaking non-pathogens dominated the bacterial flora. Immunoglobulins are of the utmost importance for the mucosal defence system, including protection against bacterial attachment to the epithelial cells (SIgA), and bacteriolysis and opsonization of the bacteria (IgG).

Child↗

PubMed1982

Lactate acid inhibition of Salmonella typhimurium in yogurt.

We determined how lactic acid inhibits growth of Salmonella typhimurium in yogurt. This inhibition was demonstrated by microscopic examination not to be due to bacteriolysis. Neither growth nor metabolic activity could be initiated after cells were washed in phosphate buffer and exposed to 1.5% lactic acid for 1 h at 37 degrees C, indicating that lactic acid inhibition is irreversible. The growth rate of S. typhimurium at 37 degrees C, was computed at various combinations of pH and lactic acid concentrations, and the intracellular conditions (pH and lactic acid concentration) at bacteriostasis subsequently were extrapolated. Cellular death resulted when these intracellular bacteriostatic conditions were surpassed. Thus, growing cells could be used indirectly to determine intracellular conditions at the time of death. Intracellular pH (pHi) and inhibition of the growth rate were unrelated. Also, bacteriostasis was observed when hydrochloric acid was used to lower the pHi of Salmonella to 5.5 whereas a bactericidal effect was observed when the pHi was lowered to 5.5 with lactic acid. The lactate anion, rather than the hydrogen ion, exerted the inhibitory effect against S. typhimurium. When the pHi became less than 5.3, inhibition was from the hydrogen ion concentration. Thus, lactic acid inhibition was a complex and variable mechanism in relationship with pHi Lactic acid entered the cell in the undissociated state. Once inside the cell, it dissociated because the pHi was higher than the external pH. The dissociated moiety accumulated because it could not leave the cell in this form consequently lowering the pHi. Thus, inhibition of S. typhimurium in yogurt is from the intracellular dissociated moiety of lactic acid.

Culture Media↗

PubMed2004

Protective activity of monoclonal antibodies to genome-derived neisserial antigen 1870, a Neisseria meningitidis candidate vaccine.

Genome-derived neisserial Ag (GNA) 1870 is a meningococcal vaccine candidate that can be subdivided into three variants based on amino acid sequence variability. Variant group 1 accounts for approximately 60% of disease-producing group B isolates. The Ag went unrecognized until its discovery by genome mining because it is expressed in low copy number by most strains. To investigate the relationship between Ab binding to GNA1870 and complement-mediated protective functions, we prepared a panel of four murine IgG mAbs against rGNA1870 (variant 1) and evaluated their activity against nine genetically diverse encapsulated Neisseria meningitidis strains expressing subvariants of variant 1 GNA1870. Based on flow cytometry with live encapsulated bacteria, surface accessibility of the epitopes recognized by the mAbs appeared to be low in most strains. Yet mAb concentrations <1 to 5 micro g/ml were sufficient to elicit bactericidal activity with human complement and/or activate C3b deposition on the bacterial surface. Certain combinations of mAbs were highly bactericidal against strains that were resistant to bactericidal activity of the respective individual mAbs. The mAbs conferred passive protection against bacteremia in infant rats challenged by strains resistant to bacteriolysis, and the protective activity paralleled the ability of the mAb to activate C3b deposition. Thus, despite low GNA1870 surface exposure, anti-GNA1870 variant 1 Abs are bactericidal and/or elicit C3b deposition and confer protection against bacteremia caused by encapsulated N. meningitidis strains expressing GNA1870 subvariant 1 proteins. The data support GNA1870 as a promising vaccine candidate for prevention of meningococcal group B disease caused by GNA1870 variant 1 strains.

Amino Acid Sequence↗

PubMed1981

Relevance of in vitro antibacterial activities of cefotiam and cefazolin to their therapeutic effects on experimental pneumonia caused by Klebsiella pneumoniae DT-S in mice.

The MICs of cefotiam and cefazolin against K. pneumoniae DT-S were unaffected by the inoculum size and were 0.1 and 1.56 micrograms/ml, respectively. Bactericidal and bacteriolytic activities of the cephalosporins were more potent in bacterial concentrations of 10(7) colony-forming units (CFU)/ml than in concentrations of 10(8) CFU/ml. Both activities of cefotiam were more markedly influenced by bacterial concentrations than those of cefazolin. Therapeutic activity of cefotiam was about 9 approximately 15 times as potent as that of cefazolin in experimental pneumonia caused by K. pneumoniae DT-S in mice, and this finding was in accordance with the ratio of in vitro antibacterial activities of the two cephalosporins as judged by the MICs or the bactericidal and bacteriolytic activities in bacterial suspension of 10(7) CFU/ml. The range of concentrations of cefotiam which induced cell filamentation in vitro, was wider than that of cefazolin. This difference, however, was not reflected on the therapeutic activities of the two cephalosporins in the model infection. In the pneumonic lungs, definite therapeutic doses of both cephalosporins (80 mg of cefotiam per kg and 640 mg of cefazolin per kg) produced mainly bacteriolysis of the challenge organisms.

Animals↗

PubMed1984

Cefodizime, an aminothiazolylcephalosporin. I. In vitro activity.

Cefodizime possesses a broad antibacterial spectrum including staphylococci, streptococci and Enterobacteriaceae. Neisseria gonorrhoeae and Haemophilus influenzae are also highly susceptible to cefodizime. Because of its beta-lactamase stability cefodizime is active against bacterial strains producing especially plasmid-coded enzymes. The MICs of cefodizime are slightly higher than those of cefotaxime, but with most Gram-negative bacteria they are lower than those of cefazolin, cefotiam and piperacillin. The in vitro activity of cefodizime is not dependent on inoculum size, or on the pH and composition of the test medium. Cefodizime did not induce in vitro resistance of Staphylococcus aureus or Escherichia coli. Because of its binding properties to PBPs 1A/B and 3, cefodizime leads to filamentation of Gram-negative rods and, at only slightly higher concentrations, to bacteriolysis.

Bacterial Proteins↗