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Methicillin-resistant Staphylococcus epidermidis.

Staphylococcus epidermidis is frequently associated with infection of prosthetic heart valves, prosthetic orthopedic devices, and neurosurgical shunts. Penicillinase-resistant semisynthetic penicillins, such as methicillin, have been the therapeutic and prophylactic agents of choice for S epidermidis infection. However, more S epidermidis isolates are now resistant to methicillin and other penicillins. In our laboratory 41% of S epidermidis isolates were resistant to methici-lin. All of the methicillin-susceptible isolates and 82% of the methicillin-resistant isoates were susceptible to cephalothin. Cephalothin should replace methicillin as the prophylactic and therapeutic agent of choice in institutions with a high percentage of methicillin-resistant S epidermidis.

Cephalothin

Susceptibility and synergy studies of methicillin-resistant Staphylococcus epidermidis.

Methicillin-resistant Staphylococcus epidermidis is an important cause of cerebrospinal fluid shunt infections and prosthetic valve endocarditis. Agar dilution minimum inhibitory concentrations were determined for 100 strains of methicillin-resistant S. epidermidis which were isolated from clinical specimens. Vancomycin inhibited all 100 strains at </=3.12 mug/ml, whereas clindamycin inhibited only 46 strains at </=12.5 mug/ml. Methicillin-resistant S. epidermidis strains were resistant to achievable levels of erythromycin, with 90 strains having a minimum inhibitory concentration of >/=3.12 mug/ml. Of the five cephalosporins and one cephamycin tested, cefamandole was the most active in vitro, inhibiting 97 strains at </=25 mug/ml. Antibiotic synergism was examined by a quantitative bacterial time-kill method. Synergism (>/=10(2) kill by the combination over the most effective single antibiotic at 24 h) was demonstrated with vancomycin (1.56 mug/ml) plus cefamandole (6.25 mug/ml) in 14 of 14 strains, vancomycin plus cephalothin (6.25 mug/ml) in 14 of 14 strains, vancomycin plus rifampin (0.008 to 0.012 mug/ml) in 6 of 12 strains, rifampin plus cefamandole in 9 of 12 strains, and rifampin plus cephalothin in 10 of 12 strains. The emergence of populations of bacteria resistant to 0.2 mug of rifampin per ml developed in three of five methicillin-resistant S. epidermidis strains tested. The addition of either vancomycin, cephalothin, or cefamandole to the rifampin prevented the emergence of resistance in these three strains. Clinical trials of synergistic antibiotic combination therapy for serious methicillin-resistant S. epidermidis infections are indicated.

Anti-Bacterial Agents

Lytic patterns of Staphylococcus epidermidis type 1.

In typing of Staphylococcus epidermidis higher concentrations of phages should be used in view of the danger of committing an error while typing at RTD only. Lytic patterns may be divided into long and short ones. The latter possess greater identification value. There are several phage types of Staphylococcus epidermidis type 1 which are more common. Phage type A 9c is chiefly encountered in hospital environments.

Bacteriophage Typing

Purification and properties of a fructose-1,6-diphosphate activated L-lactate dehydrogenase from Staphylococcus epidermidis.

L-(+)-lactate dehydrogenase (LDH) from Staphylococcus epidermidis ATCC 14990 was purified by affinity chromatography. The purified enzyme was specifically activated by fructose-1,6-diphosphate (FDP). The concentration of FDP required for 50% maximal activity was about 0.15 mM. The enzyme activity was inhibited by adenosine diphosphate (ADP) and oxamate. The inhibition by ADP appeared to be competitive with respect to reduced nicotinamide adenine dinucleotide (NADH). The catalytic activity of the LDH for pyruvate reduction exhibited an optimum at pH 5.6. The enzyme is composed of four, probably identical, subunits. Sephadex gel filtration and sedimentation velocity at pH 5.6 Yielded molecular weights of about 130 000 and 126 000, respectively. The molecular weight at pH 6.5 and 7.0 was found to be only about 68 000. Polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate and sedimentation velocity at pH 2.0 or 8.5 revealed monomeric subunits with an approximate molecular weight of 36000. The thermostability of the heat labile enzyme was increased in the presence of FDP, NADH and pyruvate. The purified LDH exhibited an anomalous type of kinetic behavior. Plots of initial velocity vs. different concentrations of pyruvate, NADH or FDP led to saturation curves with intermediary plateau regions. As a consequence of these plateau regions the Hill coefficient alternated between lower and higher n-values. Some distinguishing properties of the S. epidermidis LDH and other LDHs activated by FDP are discussed.

Adenine Nucleotides

Antibiotic activity in vitro against methicillin-resistant Staphylococcus epidermidis and therapy of an experimental infection.

Staphylococcus epidermidis is a major pathogen in early prosthetic valve endocarditis and cerebrospinal fluid shunt infections. Approximately 10 to 15% of hospital isolates are methicillin resistant. Ten clinically significant isolates of the latter were collected for antibiotic studies in vitro and in an experimental infection in animals. Time-kill studies of five strains showed gentamicin to be the single most effective antibiotic; however, dwarf colony variants emerged as survivors with two of these strains when challenged with gentamicin alone. The addition of a second antibiotic to gentamicin did not significantly improve the bactericidal rate but prevented the emergence of variant strains. A blood culture isolate of methicillin-resistant S. epidermidis combined with 5% hog gastric mucin was used to establish an experimental intraperitoneal infection in mice. Neither methicillin nor nafcillin treatment reduced mortality below that of untreated animals. Cephalothin treatment delayed early mortality but did not diminish overall mortality. Gentamicin was the most effective single antibiotic, and gentamicin in combination with vancomycin was the most effective regimen overall. The combination of rifampin plus vancomycin was as effective as gentamicin alone. The combinations of cephalothin or nafcillin with gentamicin and cephalothin with vancomycin demonstrated antagonism. The antagonism was not due to multiple injections or drug-drug inactivation.

Animals

Treatment of necrotizing fasciitis caused by Staphylococcus epidermidis.

Postoperative necrotizing fasciitis with septicemia caused by Staphylococcus epidermidis was documented by cultures of the blood and wound biopsy specimen. Therapy consisted of surgical debridement, topical application of mafenide acetate dressings, and parenteral administration of cefazolin sodium. The combination effectively reversed the progression of infection and necrosis.

Abdominal Muscles

Efficacy of phage typing epidemiologically related Staphylococcus epidermidis strains.

A total of 118 epidemiologically related Staphylococcus epidermidis strains from hospital patients, staff, and fomites were examined with a provisional set of 18 typing phages. Seventy (59.3%) of these strains were typed using phage concentrations of 100 times routine test dilution. The remainder were nontypable. Thirty-six (30.5%) of the strains were of related phage types, 71/108/275A/459 and 71/108/275A. These latter strains were associated with clinical S. epidermidis endocarditis in patients with prosthetic valve replacements. Ninety-eight strains were characterized by the Baird-Parket biotyping schema. Eighty-three (84.7%) were biotype 1, and the majority (68.4%) of these were resistant to penicillin, ampicillin, methicillin, cephalothin, erythromycin, and clindamycin. Type 71, 71/108/275A/459, 71/108/275A and 71/108/275/459 strains were generally resistant to penicillin, ampicillin, erythromycin, and methicillin, whereas a less consistent resistance pattern was noted among miscellaneous and nontypable strains.

Anti-Bacterial Agents

Development of a bacteriophage-typing set for Staphylococcus epidermidis.

Six phages isolated from lysogenic cultures of Staphylococcus epidermidis were used to type cultures in our collection classified previously as "untypable" with our original typing set of 13 phages, new clinical isolates from Missouri, and clinical isolates from Connecticut, Georgia, Pennsylvania, and Virginia. Typability with the new set of 6 phages and with our 13 original phages was compared. For 203 cultures, 81 (39.9%) cultures were typable with the set of 6 phages and 73 (36.0%) cultures were typable with the set of 13 phages. When the two typing sets were combined, the percentage of typability for 425 cultures increased to 49.9%. compared with 35.7% with the original set of 13 phages. For 109 cultures from outstate, the percentage of typability was 56.9%, whereas that for 316 cultures from Missouri was 47.5%. When only cultures in biotype 1 were considered, the percentage of typability for 268 cultures with the combined set increased to 58.2%, compared with 39.5% with the original set of 13 phages. Analysis of individual reactions for all 425 cultures typed in our laboratory indicated that 11 of the 19 phages in the combined set accounted for the majority of the reactions, and a provisional set containing these 11 phages is proposed.

Bacteriophage Typing

Phage typing of Staphylococcus epidermidis.

Thirteen phages were isolated from lysogenic cultures of Staphylococcus epidermidis from a clinical laboratory and used to type 223 clinical isolates of this organism. The 18 phages isolated in The Netherlands were used to type these same cultures. No correlation was observed between phage type, biotype, or clinical source of isolation. At phage concentrations of 100 times the routine test dilution, 35.0% of the cultures were typable with out phages and 21.5% were typable with the phages from The Netherlands. When only cultures in biotype 1 were considered, 43.3 and 24.1% of 141 cultures were typable with our phages and those from The Netherlands, respectively. The lytic reactions obtained with our phages were generally stronger and easier to read and the lytic patterns were, almost invariably, shorter. The typability of untypable cultures was increased 12.0% by incubation at 45 C prior to phage typing and 20% by heat shock (55 C for 5 min) prior to typing. Phage typing 5 subcultures of 20 typable cultures on 5 successive days showed that the lytic patterns were reproducible. The present status of phage typing S. epidermidis and the work needed to obtain a set of typing phages for epidemiological studies of infections by this organism are discussed.

Bacteriophage Typing

[Bacterial endocarditis due to Staphylococcus epidermidis. Two cases (author's transl)].

Bacterial endocarditis due to Staphylococcus epermidis is rare and severe. In a first patient, a 58-year-old-man, it developed 40 days after the insertion of a double prosthesis (mitral and aortic). Cure was obtained by medical treatment using a combination of vancomycin and gentamicin, followed by pristinamycin and tobramycin. The second patient, a 50-year-old-woman, suffering from cirrhogenic hepatitis and treated with corticosteroids. Staphylococcus epidermidis endocarditis developed without any portal of entry being discovered. After the failure of various antibiotic combinations (even though bactericidal in vitro), a mitral Starr valve was inserted which resulted in cure. None of the patients showed any sign of valvular mutilations or disinsertion of prosthesis.

Adrenal Cortex Hormones

Transduction of penicillinase production in Staphylococcus epidermidis and nature of the genetic determinant.

Four strains of Staphylococcus epidermidis from clinical sources were capable of serving as donors for the transduction of either penicillinase production, ethidium bromide resistance, or tetracycline resistance. Three typing phages served as transducing phages and, depending upon the combination of transducing phage, donor strain, and recipient strain, the rates of transduction ranged between 10(-5) and 10(-9). In one strain, cotransduction of penicillinase production and ethidium bromide resistance was observed. Although ultraviolet irradiation kinetics indicated that both the tetracycline resistance and the penicillin resistance determinants were located on plasmids, only resistance to tetracycline could be eliminated by growth in the presence of curing agents or at elevated temperature. However, evidence was obtained by agarose gel electrophoretic studies that both the tetracycline resistance and the penicillin resistance determinants are located on separate plasmids in this organism.

Drug Resistance, Microbial

Anaerobic transport of serine and 2-aminoisobutyric acid by Staphylococcus epidermidis.

A membrane-bound ATPase detected in extracts of anaerobically grown Staphylococcus epidermidis was inhibited by a variety of compounds which inhibit ATPases in other organisms. Serine and 2-aminoisobutyric acid (AIB) were shown to enter the organism via the same transport system. The transport of AIB, the membrane potential and the transmembrane pH gradient were partially or completely abolished by the same inhibitors and also by uncoupling agents and lipid-soluble ions. It is proposed therefore that this ATPase generates and maintains an electrochemical gradient of protons across the cytoplasmic membrane of S. epidermidis capable of driving AIB uptake. Studies of AIB-induced proton movements suggested that AIB enters via a proton symport mechanism.

Adenosine Triphosphatases

Epidemiologic features and phage types associated with nosocomial infections caused by Staphylococcus epidermidis.

An apparent problem with increased numbers of nosocomial infections caused by Staphylococcus epidermidis at a large hospital was studied in a clinical-epidemiological investigation. Thirty-six cases of S. epidermidis infection were confirmed on the thoracic surgery, general surgery, nursery and pediatric services during a 3-year period. Nine cases were fatal and six of these occurred in patients following cardiovascular surgery with implanted prothesis. The majority of cases (25/36) occurred following cardiovascular surgery. The median onset of infection was six days from the date of surgery, suggesting infection during the intraoperative period. Although the number of cases studied remains small, two phage types, 71/108/275a/459 and 407-2, did predominate among these clinical infections. Interestingly, during this same time interval these same types predominated among surgical staff members closely associated with these patients. Resistance to antimicrobials was high among isolates tested, with more than 50% of the strains resistant to six or more antimicrobial agents.

Adolescent

Transduction of penicillinase production and other antibiotic-resistance markers in Staphylococcus epidermidis.

Transduction of resistance from a multiply antibiotic-resistant strain of Staphylococcus epidermidis sub-group II was studied using the typing phage 108. The effect of increasing doses of ultraviolet radiation on the transducing phage was used to indicate the chromosomal or plasmid nature of the genes. Tetracycline and chloramphenicol resistance behaved as plasmid genes and streptomycin resistance as a chromosomal marker. It was also possible to transduce penicillin resistance (Pc) due to penicillinase production (bla+) using a low level of benzylpenicillin (0.03 microgram ml-1) for recovery. Approximately 10(-5) transductant colonies per phage input were obtained and ultraviolet kinetics indicated that Pc was plasmid carried. Pc transductants fell into two categories. In one group PC was stable as in the donor strain and transductants had the same phage sensitivity as the recipient. In the other, Pc was unstable at 37 degrees C and the instability was enhanced by growth at approximately 43.5 degrees C; these transductants also gained genes for restriction and modification of certain phages. Transductants that subsequently lost bla+ also lost the restriction and modification characters.

Anti-Bacterial Agents

Utilizing whole genome sequencing to characterize central line-associated bloodstream infections due to Staphylococcus epidermidis.

Whole genome sequencing (WGS) and clinical review were used to characterize 14 cases of central line-associated bloodstream infection (CLABSI) due to Staphylococcus epidermidis. WGS, which demonstrated disparate strains, suggested that 42.9% of S. epidermidis CLABSI cases were due to contamination, while clinical review suggested that 57.1% were contamination events.

Humans

Genome sequence of Staphylococcus epidermidis H1G7 from hilsa (Tenualosa ilisha) gut.

We report the genome of Staphylococcus epidermidis strain H1G7 from hilsa (Tenualosa Ilisha) fish gut. Nanopore sequencing produced a 2.5-Mb assembly (32% GC, two contigs). The genome encodes metal-chelate transport, short-chain fatty acid production, and biosynthetic clusters and lacks virulent factors, revealing genomic features potentially associated with beneficial host interactions.

cyclodipeptide synthase

Evaluation of a new bacteriophage set for typing of Staphylococcus epidermidis strains.

A new set of typing phages was evaluated for typing 821 Staphylococcus epidermidis strains isolated from normal human skin and from acne lesions. This method was compared with two different systems for biochemical differentiation of S. epidermidis. Distinct subgroups of cocci, which differed in phage susceptibility as well as in biochemical properties, were found. A tentative subdivision of S. epidermidis strains by use of 16 phages arranged into four groups is proposed, together with additional biochemical differentiation of non-typable strains.

Acne Vulgaris