Desoxyribonuclease and lecithinase activity in antibiotic-resistant and -sensitive staphylococci]

Staphylococcus aureus, a laboratory strain 209-P and strain I isolated freshly from infected wounds, as well as lincomycin hydrochloride, ampicillin, oxacillin and methicillin manufactured in the USSR and cephaloridin manufactured by "PLIVA" in Yugoslavia were used. Various activity levels of desoxyribonuclease and lecitinase of the staphylococci depending on sensitivity or resistance of the test-microbe to the antibiotics were shown. The activity of the above microbial enzymes characterizing the pathogenic properties decreased with development of the antibiotic resistance, sometimes to complete inactivation of the enzymes synthesized by the staphylococci. In spite of closeness of their modes of action the semisynthetic penicillins had a differentiating effect on the above enzymes.     

Method of oblique illumination in studying the morphology of Staphylococcus aureus colonies sensitive and resistant to antibiotics]

The morphology of the colonies of Staph. aureus sensitive and resistant to antibiotics and the colonies with artificial resistance to benzylpenicillin, ampicillin, oxacillin, methicillin, cephaloridin and lincomycin was studied with the method of slanting light. Changes in the morphology of the colonies were most pronounced at the beginning of the microbial resistance development first of all in the cultures of Staph. aureus resistant to cephaloridin and lincomycin.     

Combined antibiotic therapy following heart surgery

In vitro efficacy of combinations of broad and narrow spectrum semi-synthetic penicillins, broad spectrum semi-synthetic penicillins with macrolides or aminoglycosides and tetracyclines with other biosynthetic antibiotics was studied with respect to the causative agents of surgical infections. Correlation between the sensitivity of the isolates and the antibiotics levels in the organism of the surgical patients was shown. The role of the etiological factor in the development of the post-operative complications in the patients after surgical operations on the heart was elucidated. The most rational schemes of the antibiotic use in therapy of the patients with purulent complications after operations on the open heart were developed and the maximum doses of different semi-synthetic penicillins for the treatment of patients with purulent processes after operations under conditions of artificial blood circulation were determined.     

Efficient use of gentamycin in treating suppurative puerperal mastitis]

A total of 80 patients with postnatal purulent mastitis were treated with gentamicins. The main causative agent was Staph. aureus resistant to the traditionally used antibiotic and sensitive to gentamicin, fusidin, rifampicin and semisynthetic penicillinase-stable penicillins. Gramnegative bacteria contaminated the purulent foci after opening. Gentamicin was highly effective in treatment of postnatal purulent mastitis in cases with mixed Staphylococcus-Proteus infection.     

Species differences in the interaction of serum albumin with antibiotics

Interaction of oxacillin, cloxacillin, dicloxacillin, phenoxymethylpenicillin, methicillin, nafcillin and benzylpenicillin with human serum albumin (HSA) was studied with flow microcalorimetry and differential scanning calorimetry. The measured thermodynamic parameters of complex formation between the penicillins and HSA were compared with similar characteristics of their binding to bovine serum albumin. It was shown that there were species differences between these two globular proteins in their interaction with the above antibiotics in relation to both the number of the biopolymer active sites and the nature of the molecular forces in the complex formation. The effect of the first bound molecule of oxacillin, cloxacillin, dicloxacillin, nafcillin, phenoxymethylpenicillin and benzylpenicillin on HSA conformation was observed. It was demonstrated that there was thermostabilization of HSA on its interaction with the above drugs with preserving cooperative nature of thermal denaturation of the complexes in relation to HSA melting.     

THE NEWER PENICILLINS

The newer penicillins give high promise of overcoming some of the few disadvantages of penicillin-G.They fall into three groups: The alpha-phenoxy-penicillins; the penicillinase resistant penicillins; and the penicillins with enhanced activity against gram-negative bacteria.The newer alpha-phenoxy-penicillins offer little over alpha-phenoxy methyl penicillin (penicillin-V). As the length of the side chain is increased, absorption and attainable serum concentration is also increased, but these are questionable benefits and probably not significant for therapeusis.The penicillinase-resistant penicillins have once more brought almost all severe staphylococcal infections within therapeutic range. One of them, methicillin, must be administered parenterally. It is the agent of choice for the treatment of severe, penicillin-G resistant staphylococcal infections, and this is its only clinical indication. Another, oxacillin, which may be administered orally, is partially resistant to gastric acid degradation, but must be given on an empty stomach. It is most useful as prolonged therapy following methicillin, in the treatment of mixed hemolytic streptococcal-penicillin-G resistant staphylococcal infections, and as primary therapy for moderately severe penicillin-G resistant staphylococcal infections.The third group is still mostly in the experimental stage, but some strains of Proteus, E. coli, Salmonella and Shigella are highly vulnerable to their action.Toxic and allergic reactions to the newer penicillins, and crossed allergic reactions with penicillin-G, present unsolved problems.     

Microbiological Activities of Lysostaphin and Penicillins Against Bacteriophage 80/81 Strains of Staphylococcus aureus

Using 20 clinical isolates of S. aureus (all bacteriophage 80/81 type), we found that lysostaphin inhibits the growth of all cultures at concentrations significantly lower than those observed with any of eight penicillins, a penicillin-like compound (cephalothin), or fusidic acid (a steroid antibiotic). All test cultures were shown to be resistant to penicillin G, ampicillin, and propicillin. Of the remaining penicillins (all penicillinase-insensitive), oxacillin, nafcillin, cloxacillin, and cephalothin were approximately equal in antimicrobial activity. Ancillin was slightly less active, and methicillin was even lower in potency. Cultures varied more widely in susceptibility to fusidic acid. None of the clinical isolates tested was found to be resistant to lysostaphin.     

Inhibition of the β-lactamases of Escherichia coli and Klebsiella aerogenes by semi-synthetic penicillins

1. A new automated micro-iodometric method is described for screening compounds for inhibitory action against beta-lactamase enzymes. 2. Over 1000 semi-synthetic penicillins were tested for inhibitory activity against the beta-lactamase of Escherichia coli B11 and 18 showed a fractional inhibition similar to or higher than that of methicillin. 3. The best inhibitors were alkoxy- and halogen-substituted phenyl-, naphthyl- or quinolyl-penicillins. 2-Isopropoxy-1-naphthylpenicillin (BRL 1437) was clearly the best and had a K(i) value about 1% of that of methicillin. 4. The inhibition of the beta-lactamase of E. coli B11 by BRL 1437 was shown to be reversible and competitive. The K(i) was 0.004mum and K(i)/K(m) with ampicillin and p-hydroxyampicillin (BRL 2333) was about 0.0001. The K(m) and V(max.) values were determined for the beta-lactamases of E. coli B11 and Klebsiella aerogenes A against a variety of penicillins. Cell-bound and solubilized enzymes gave similar K(i) and K(m) values. 5. BRL 1437 was superior to cloxacillin and methicillin for inhibition of the beta-lactamase of live, fully grown cultures of several strains of E. coli and K. aerogenes. Of a group of inhibitors BRL 1437 was the most stable to the beta-lactamase of E. coli B11.     

Changes in the ultrastructure of Staph. aureus cells under the action of certain antibiotics]

The ultrastructure of staphylococcal cells being in contact with oxacillin, cephaloridin, lincomycin, fusidin or gentamycin was studied with the help of electron microscopy. Differences in the changes of the submicroscopic sturcutre of the cells under the effect of the antibiotics inhibiting the synthesis of the cell walls or protein synthesis were shown. Teh level of the structure changes depended on the drug concentration.     

Antibiotic sensitivity of Staphylococci populating the breast skin of nursing women

Sensitivity to penicillins, tetracycline, erythromycin and lincomycin was tested in 1513 staphylococcal strains isolated from the skin of various anatomic areas of the breast of nursing mothers. It was shown that 82.9, 78.4 and 33.9 per cent of the isolated cultures were highly sensitive to lincomycin, erythromycin and methicillin respectively. Sensitivity to tetracycline and benzylpenicillin was detected in 33.1 and 19.8 per cent of the cultures respectively. The study of the resistance spectra of 1343 strains resistant to certain antibiotics revealed that 498 cultures (37.1 per cent) were polyresistant. None of the tested antibiotics could be used for selective decontamination of the breast skin with respect to S. aureus in prophylaxis of lactic mastitis.     

SAR-2: Identification of a novel plasmid-encoded β-lactamase from India

A novel beta-lactamase has been identified in an Escherichia coli strain isolated in South India. The beta-lactamase gene was carried on a plasmid (pUK734) along with resistance determinants to sulphonamides and tetracycline. The novel enzyme has a pI of 8.3 and an Mr of 36,000. The enzyme has a broad-spectrum of activity against both penicillins and cephalosporins. It is also active against oxacillin and methicillin.     

Drug Resistance as Influenced by Inactivated Sensitivity Discs

Reports of staphylococci resistant to the semisynthetic penicillins stimulated a study of the factors influencing the stability of the drugs in discs. The behavior of penicillin G, methicillin, oxacillin, cloxacillin, and cephalothin discs under different humidity and temperature conditions is described. Humidity was found to be the most significant factor in drug inactivation. Storage of discs in a vacuum desiccator at -20 C provides maximal antibiotic stability.     

Study of the therapeutic effectiveness of oxacillin in treating the infectious forms of syphilis]

Data on efficiency of oxacillin therapy as applied to 45 patients with contagious forms of syphilis are presented. The drug was administered orally and intramuscularly to 40 and 5 patients respectively for 20 days. The periods of clearance from Trepanoma pallidum, disappearance of the external syphilis manifestations and the rate of the decrease in the titer of the serological reaction reagins are presented. The levels of oxacillin in the blood serum of 24 patients were determined for 5--6 hours from the moment of the treatment beginning. The study showed therapeutic efficiency of oxacillin.     

Pharmacokinetics of penicillins in the blood of dogs administered the combination preparation, ampiox, internally]

The pharmacokinetics of penicillins in the blood of dogs treated with ampiox, a combination of ampicillin and oxacillin at a ratio of 1 : 1 was studied. The drug was administered orally in single or repeated doses of 25, 50 and 100 mg/kg. The maximum levels of ampicillin in the blood serum were observed 1 hour after a single administration of the drug. The therapeutic concentrations of the antibiotic were preserved for 6 hours, its value being depended on the dose used. The maximum concentration of oxacillin was detected 1 hour after the drug administration in various doses and it was preserved in the blood at the therapeutic levels for 3 hours. The dynamics of circulation of ampicillin and oxacillin administered separately did not differ from that established for the use of ampiox. The regularities of the pharmacokinetics of ampiox on its repeated use remained practically unchanged.     

Effect of chymotrypsin on the urinary excretion of antibiotics in rabbits]

The effect of cymotrypsin on excretion of penicillin, methicillin, oxacillin, streptomycin and gentamycin with urine including the kidney clearance was studied on rabbits. It was found that the enzyme introduced intramuscularly in a dose of 20 mg/kg increased excretion of penicillin, methicillin, oxacillin and gentamycin by 37, 24, 26 and 16 per cent respectively. The only exclusion was streptomycin. Chymotrypsin increased the kidney clearance of penicillin, methicillin, oxacillin, streptomycin and gentamycin by 1.7, 1.9, 2.2, 1.2 and 1.5 times respectively.     

The use of oxacillin and cefoxitin disk-diffusion method and PCR for the identification methicillin-resistant Staphylococcus epidermidis

Methicillin-resistant S. epidermidis are recognized as one of the most important nosocomial infections. Because of the different expression level of mecA gene which is under regulatory genes control, detection of methicillin resistance by phenotypic methods may leads to false negative or false positive results. The aim of this study was to estimate effectiveness of MRSE strains identification using oxacillin (1 microg) and cefoxitin (30 microg) disk-diffusion method in comparison with PCR, considered as a "gold standard". The analysis of 120 strains isolated from clinical materials of patients of the University Hospital at the L. Rydygier Collegium Medicum in Bydgoszcz, University of Nicolaus Copernicus in Toruń indicated high degree of correlation between phenotypic methods with taken disks. Results consistency of detecting methicillin resistance between oxacillin disk diffusion method and PCR concerned 95% strains. In case of cefoxitin 4,2% S. epidermidis strains detected phenotypically as MSSE were mecA-positive. Our results show that disk-diffusion method with disks mentioned above is characterized by comparable specificity and sensitivity amounted 90,8% and 100% for oxacillin and 92,3% and 100% for cefoxitin respectively.     

The effect of hydrophobicity of β-lactam antibiotics on their phospholipid bilayer permeability

Phospholipid bilayer permeability of β-lactam antibiotics was determined using liposomes enclosing β-lactamase. There was good correlation between the permeability and hydrophobicity within the analogous β-lactams. However, the effect of hydrophobic character on the permeability parameter was very different between the groups. Moderately hydrophilic penicillins such as benzylpenicillin and ampicillin showed very high permeability compared with cephalosporins. Penicillins having hindered side chains such as oxacillin and methicillin showed moderate permeability taking into account their hydrophobicity. These observations are suggestive of outer membrane permeation of these β-lactams via routes other than the porin pore, especially in porin-deficient mutants of gram-negative bacteria.     

Susceptibility of Coagulase-negative Staphylococci to Lysostaphin and Other Antibiotics

In general, coagulase-negative staphylococci were found to be relatively less susceptible to the lytic action of lysostaphin than coagulase-positive staphylococci. To achieve, arbitrarily, a lysis greater than 75%, it was necessary to use an increased concentration of enzyme or a longer incubation period than that usually required with coagulase-positive strains. For the most part, the cultures studied were sensitive to oxacillin, cloxacillin, dicloxacillin, nafcillin, ancillin, cephalothin, cephaloridine, fusidic acid, lincomycin, novobiocin, and neomycin [median minimal inhibitory concentrations (MIC) of 1.56 mug/ml or less]. Some degree of resistance (median MIC values of 12.5 mug/ml or greater) to benzylpenicillin, ampicillin, methicillin, tetracycline, chloretetracycline, erythromycin, ristocetin, and lysostaphin was found. Ten methicillin-resistant, coagulase-negative staphylococal strains were found to be cross-resistant to all nine of the penicillins tested, but much less resistant to the two cephalosporin analogues. In several instances, some of these strains seemed to be more sensitive to benzylpenicillin and to certain of the semisynthetic penicillins than to methicillin. Of the 18 antibiotics tested with the viable plate count method, the methicillin-resistant strains were found to be the most sensitive to lincomycin and novobiocin.     

A survey of the kinetic parameters of class C beta-lactamases. Penicillins.

The interaction between six class C beta-lactamases and various penicillins has been studied. All the enzymes behaved in a very uniform manner. Benzylpenicillin exhibited relatively low kcat. values (14-75 s-1) but low values of Km resulted in high catalytic efficiencies [kcat./Km = 10 X 10(6)-75 X 10(6) M-1.s-1]. The kcat. values for ampicillin were 10-100-fold lower. Carbenicillin, oxacillin cloxacillin and methicillin were very poor substrates, exhibiting kcat. values between 1 x 10(-3) and 0.1 s-1. The Km values were correspondingly small. It could safely be hypothesized that, with all the tested substrates, deacylation was rate-limiting, resulting in acyl-enzyme accumulation.     

Antibiotic Therapy of Staphylococcal Infections

The antibiotic treatment of staphylococcal infections remains a problem. Isolation of the organism and sensitivity testing are necessary in the choice of antibiotic. Penicillin G is the most effective penicillin against non-penicillinase-producing staphy-lococci; for the penicillinase producers there is very little to choose between the semisynthetic penicillins, methicillin, cloxacillin, nafcillin and oxacillin. For patients who are hypersensitive to penicillin, the bacteriostatic drugs (erythromycin, novobiocin, tetracycline, chloramphenicol, oleandomycin) are useful for mild infections, while for more severe illness the bactericidal drugs (vancomycin, ristocetin, kanamycin, bacitracin, neomycin) have been used successfully. Acute staphylococcal enterocolitis is probably best treated by a semisynthetic penicillin. Other antibiotics which have been found useful, with clinical trials, for staphylococcal infections are cephalosporin, fucidin, cephaloridine and lincomycin. The latter drug has been reported of value in the treatment of osteomyelitis. There is little justification for the prophylactic use of antibiotics to prevent staphylococcal infection. Surgical drainage is still an important adjunct in the treatment of many staphylococcal infections.