Effective removal of staphylococcal biofilms by the endolysin LysH5

Staphylococcal biofilms are a major concern in both clinical and food settings because they are an important source of contamination. The efficacy of established cleaning procedures is often hindered due to the ability of some antimicrobial compounds to induce biofilm formation, and to the presence of persister cells, a small bacterial subpopulation that exhibits multidrug tolerance. Phage lytic enzymes have demonstrated antimicrobial activity against planktonic and sessile bacteria. However, their ability to lyse and/or select persister cells remains largely unexplored so far. In this work, the lytic activity of the endolysin LysH5 against Staphylococcus aureus and Staphylococcus epidermidis biofilms was confirmed. LysH5 reduced staphylococcal sessile cell counts by 1-3 log units, compared with the untreated control, and sub-inhibitory concentrations of this protein did not induce biofilm formation. LysH5-surviving cells were not resistant to the lytic activity of this protein, suggesting that no persister cells were selected. Moreover, to prove the lytic ability of LysH5 against this subpopulation, both S. aureus exponential cultures and persister cells obtained after treatment with rifampicin and ciprofloxacin were subsequently treated with LysH5. The results demonstrated that besides the notable activity of endolysin LysH5 against staphylococcal biofilms, persister cells were also inhibited, which raises new opportunities as an adjuvant for some antibiotics.

Stability of Staphylococcus aureus phage ISP after freeze-drying (lyophilization)

Staphylococcus aureus phage ISP was lyophilized, using an Amsco-Finn Aqua GT4 freeze dryer, in the presence of six different stabilizers at different concentrations. Stability of the lyophilized phage at 4°C was monitored up to 37 months and compared to stability in Luria Bertani broth and physiological saline at 4°C. Sucrose and trehalose were shown to be the best stabilizing additives, causing a decrease of only 1 log immediately after the lyophilization procedure and showing high stability during a 27 month storage period.

Ciprofloxacin and trimethoprim cause phage induction and virulence modulation in Staphylococcus aureus

In Staphylococcus aureus strains of human origin, phages which integrate into the chromosomal gene coding for beta-hemolysin (hlb) are widely distributed. Most of them encode accessory virulence determinants such as staphylokinase (sak) or enterotoxins. Here, we analyzed the effects of ciprofloxacin and trimethoprim on phage induction and expression of phage-encoded virulence factors by using isolates from patients with cystic fibrosis for which the induction of hlb-converting phages was demonstrated in vivo (C. Goerke, S. Matias y Papenberg, S. Dasbach, K. Dietz, R. Ziebach, B. C. Kahl, and C. Wolz, J. Infect. Dis. 189:724-734, 2004) as well as a phi13 lysogen of phage-cured strain 8325-4. Treatment of lysogens with subinhibitory concentrations of either antibiotic resulted in (i) delysogenization of strains resembling the isolates picked up after chronic lung infection and (ii) replication of phages in the bacterial host in a dose-dependent manner. Ciprofloxacin treatment resulted in enhanced recA transcription, indicating involvement of the SOS response in phage mobilization. Induction of phi13 was linked to elevated expression of the phage-encoded virulence gene sak, chiefly due to the activation of latent phage promoters. In summary, we could show the induction of hlb-converting phages and a subsequent virulence modulation of the host bacterium by ciprofloxacin and trimethoprim.

Antibiotic-induced SOS response promotes horizontal dissemination of pathogenicity island-encoded virulence factors in staphylococci

Although mobile genetic elements have a crucial role in spreading pathogenicity-determining genes among bacterial populations, environmental and genetic factors involved in the horizontal transfer of these genes are largely unknown. Here we show that SaPIbov1, a Staphylococcus aureus pathogenicity island that belongs to the growing family of these elements that are found in many strains, is induced to excise and replicate after SOS induction of at least three different temperate phages, 80alpha, phi11 and phi147, and is then packaged into phage-like particles and transferred at high frequency. SOS induction by commonly used fluoroquinolone antibiotics, such as ciprofloxacin, also results in replication and high-frequency transfer of this element, as well as of SaPI1, the prototypical island of S. aureus, suggesting that such antibiotics may have the unintended consequence of promoting the spread of bacterial virulence factors. Although the strains containing these prophages do not normally contain SaPIs, we have found that RF122-1, the original SaPIbov1-containing clinical isolate, contains a putative second pathogenicity island that is replicated after SOS induction, by antibiotic treatment, of the prophage(s) present in the strain. Although SaPIbov1 is not induced to replicate after SOS induction in this strain, it is transferred by the antibiotic-activated phages. We conclude that SOS induction by therapeutic agents can promote the spread of staphylococcal virulence genes.

Phenotypic and molecular characterization of community occurring, Western Samoan phage pattern methicillin-resistant Staphylococcus aureus

In New Zealand, it is estimated that greater than half of the methicillin-resistant Staphylococcus aureus (MRSA) strains recovered from patients belong to what has been termed Western Samoan phage pattern types 1 and 2 (WSPP1, WSPP2). These strains differ from classical MRSA isolates in terms of their lack of multiresistance and community occurrence, suggesting that such strains possess properties and/or characteristics different from those of other MRSA. To address this hypothesis, 10 WSPP1 and WSPP2 isolates from Western Samoa, New Zealand and Australia were compared with common hospital MRSA isolates. All WSPP isolates were identical with regard to pulsed-field gel electrophoretic pattern of SmaI-digested DNA, coagulase gene restriction fragment length polymorphism pattern and localization of mecA to a 194 kb SmaI digestion fragment. The WSPP strains were no more resistant/sensitive to various environmental stresses (e.g. skin fatty acids, UV light, desiccation) compared with hospital epidemic MRSA strains, except for their higher tolerance to salt. In terms of virulence, the WSPP MRSA were quantitatively better at attaching to the epithelial cell line HEp2, were uniformly egg-yolk opacity factor negative and produced higher levels of haemolytic toxins compared with non-WSPP MRSA isolates.

[A comparative analysis of energy process inhibitors on the efficiency of phage infection in staphylococci]

The study of the effect of KCN, DCCD and CCCP as inhibitors of the energy yielding processes showed that the efficacy of phage infection depended on respiration, proton ATPase, and proton electrochemical potential of hydrogen ions. There was a 49.5-68.0% decrease of the efficacy of phage infection after addition of the above mentioned inhibitors at the period of the contact of cells with bacteriophages at the stage of the phage nucleic acid transfer. The Embden-Meyerhof-Parnas route inhibitors NaF and CH2ICOOH less affected the efficacy of phage infection. The same effect was observed during addition of Na3AsO4 as the ATP synthesis inhibitor. This efficacy decrease was probably due the inhibition of the processes of the substrate level phosphorylation and the deplete of the intracellular ATP content.

Molecular and phage typing of Staphylococcus aureus harbouring cryptic conjugative plasmids

The spread of antibiotic resistant-bacterial pathogens in a hospital could be due to the spread of a resistant strain or the spread of a resistance plasmid among unrelated strains. In this study the relatedness of Staphylococcus aureus isolates carrying identical cryptic conjugative plasmids was determined by a combination of resistance profiles, plasmid patterns, pulsed field gel electrophoresis of SmaI digested chromosomal DNA and phage typing. Results of the different typing techniques were in agreement to one another and demonstrated that the isolates were of three different types. The results suggested that a cryptic conjugative plasmid had spread to different S. aureus isolates in the hospital. This is an example of plasmid spread as opposed to strain spread.

[Phage-mediated conjugative transfer of plasmids in Staphylococcus aureus]

It was shown possible to transfer nonconjugative plasmids during joint cultivation of the donor and recipient cells by transduction and phage-mediated conjugation. In the latter case it was necessary that the phage in the medium was free and the prophage was present in the recipient cells. Differences in the regularities of the transfer of the nonconjugative plasmids mobilized by the conjugative plasmid or phage were observed.

[Differentiation of methicillin-resistant strains of Staphylococcus aureus by prophage specificity]

By inducing with mitomycin C the following phages were isolated from all the tested 32 methicillin resistant strains of S. aureus: the serogroup B phage was isolated from 2 strains, the serogroup B and F phages were isolated from 5 strains and the serogroup F phage was isolated from 25 strains. The phages were divided into 5 groups by the antiphage immunity. In group 1 of the phages 4 additional phages were specified. By the specificity of the prophages in the cultures all the strains were divided into 5 groups. Group 1 of the cultures was divided into 5 subgroups (A, B, C, D and E).

[Effect of prophages on transfer frequency of conjugative plasmid G 873]

Transfer of the conjugative plasmid G873 on filters and mixed cultivation of the donor and recipient cells in liquid media is described. In the both systems the use of the lysogenic recipient cells (phages of serogroups B and F) in the crossings increased mor than 100-fold the frequency of plasmid transfer. The conjugative transfer of the plasmid in the mixed cultivation system was proved. The conjugative transfer required the presence (while not obligatory) of calcium chloride and was restricted by the serum factors.

Ciprofloxacin-resistant methicillin-resistant Staphylococcus aureus in New York health care facilities, 1988. The New York MRSA Study Group

The emergence in 1988 of ciprofloxacin-resistant methicillin-resistant Staphylococcus aureus (MRSA) in New York City was studied in nine hospitals and eight nursing homes. Of the 43 hospitalized patients studied, 21 were admitted from home, while nine of the 12 nursing home patients were transferred from a hospital. Twenty-four of the 55 patients had been treated previously with ciprofloxacin, and 26 had an identifiable risk factor for a nosocomial infection. MRSA was a contributing factor in at least five of the 21 deaths. MRSA resistance to ciprofloxacin was detected within three months of the drug's commercial availability, apparently emerged independently at a number of the health care facilities, and has become widespread. If such resistance is found in a health care facility, ciprofloxacin may not be useful as a first line antibiotic.

[The effect of valinomycin and nigericin on the efficacy of bacteriophage infection of staphylococcal cells]

The effect of ionophore antibiotics, valinomycin and nigericin, on the generation of the membrane potential, the pH gradient and the efficacy of phage infection in tetracycline-resistant staphylococci has been studied. Valinomycin at a concentration of 0.5 microM induces the dissipation of the membrane potential, and nigericin at a concentration of 12.0 microM decreases the value of the pH gradient on the membrane of staphylococci. The separate use of antibiotics has no essential influence on the efficacy of phage infection. The combined use of valinomycin and nigerimycin produces the maximum inhibition of phage infection (64.5%) at the stage of the introduction of DNA into the bacterial cell, which is indicative of a definite role played by the membrane potential and the pH gradient in the transport of phage DNA into staphylococcal cells.

Indomethacin sensitive suppressor-cell activity in head and neck cancer patients. The role of the adherent mononuclear cell

Head and neck cancer (H&N CA) patients have known depression of cell-mediated immunity. There is suggestive evidence that prostaglandin (PGE2)-secreting cells may be a major factor. The authors have sought to determine the role of PGE2-releasing monocytes-macrophages in this immune depression by determining the effects of adherent cell depletion and by measuring the effects of indomethacin, a PGE2 synthetase inhibitor, on selected tests of lymphocyte function. Lymphocyte stimulation with phytohemagglutinin (PHA) (T-cell stimulant) and Staph phage lysate (SPL) (B-cell stimulant) was done in the presence of varying concentrations of indomethacin; the effect of adherent cell depletion also was determined. The study population included 45 patients with localized or locoregional squamous CA of the H&N and 40 controls. Results included the following: (1) lymphocyte stimulation responses to PHA and SPL were generally depressed in the CA patients versus controls; (2) incubation with indomethacin produced bivalent effects in both controls and CA patients, depending on the concentration of indomethacin and lymphocyte stimulant; incubation with optimum concentrations of indomethacin generally produced augmented responses in both study groups whereas high concentrations of indomethacin were suppressive; (3) the immune potentiating effects were not observed in older patients with advanced disease; and (4) removal of adherent leukocytes (mainly monocytes) also restored depressed lymphocyte responses. Although other factors also are operative, our data suggest that PGE2-secreting monocytes-macrophages may have a major role in the immune depression of H&N CA patients. Age and host effects of the cancer and the malnutrition common to these patients probably are involved also, although their singular contribution has not been measured. This depression is largely reversible by a PGE2 synthesis inhibitor, indomethacin, which suggests the potential value of in vivo administration of indomethacin to H&N CA patients as an adjunct.

[Role of lysogenizing phages in the spread of drug-resistance plasmids in a staphylococcal population]

The frequency of the transduction of plasmids rms5, rms7, pT127, pC194, pS194 and pUB101 by phages belonging to serological group B (80, 52, 52A, 53, 85, phi 11, S2) in two systems was compared. In system 1 phages for transduction were obtained from plasmid-containing lysogenic donors in the process of induction with mitomycin C; in system 2 phages for transduction were obtained by their multiplication in plasmid-containing nonlysogenic donors. In system 1 the transduction of plasmids rms5, rms7, pT127, pS194 by phage 52A was found to occur with a greater (by 3-5 orders) frequency than in system 2 (the frequency of transduction was 10(-2) to 10(-4), and 10(-6) to 10(-8) respectively). A similar situation was observed with plasmids rms5 and rms7 and phage 52; plasmid pT127 and phage 53; but not observed with plasmids rms5 and rms7 and phages 80, phi 11 and S2; plasmids pC194 and pS194 and phage 53; plasmid pUB101 and phages 52A, 80 and phi 11; plasmids pC194, pS194 and pT127 and phage 85.

Differential toxicities of mercury to bacteria and bacteriophages in sea and in lake water

Mixtures of anionic HgCl3-/HgCl4(2)-complexes were less toxic to terrestrial bacteria (Erwinia herbicola, Agrobacterium tumefaciens), to marine bacteria (Acinetobacter sp., Aeromonas sp.), and to bacteriophages (phi 11 M 15 of Staphylococcus aureus and P1 of Escherichia coli) than were equivalent concentrations of Hg as cationic Hg2+. The toxicity of 1 ppm Hg to A. tumefaciens. Aeromonas sp., and phi 11 M 15 was less in seawater than in lake water. Inasmuch as the Hg-Cl species are formed in environments of high chloride concentration, it was postulated that the lower toxicity of Hg in seawater was a result of the formation of HgCl3-/HgCl4(2)-complexes.

Changing phage typing patterns of epidemic gentamicin-resistant Staphylococcus aureus. Evidence for transmission of gentamicin resistance

In a 10-week period, infection with gentamicin resistant Staphylococcus aureus appeared in 24 adults and infants in one hospital. Medical staff were affected first, and subsequently 16 infants in the neonatal intensive-care unit. The gentamicin-resistant staphyloccal isolates showed three distinct phage susceptibility patterns in two distinct phage groups during the early, middle, and late phases of the outbreak. Although not confirmed with in-vitro or in-vivo laboratory data, this outbreak suggests that gentamicin resistance may be transferred between different strains of Staph. aureus in vivo.

[Effect of surface-active antiseptics on plasmid transduction of drug resistance and the transducing bacteriophages of staphylococci]

Anionic surface active substances (SAS), such as sodium alkylsulfates, iodonate, sulfanol NP-3 used in subbacteriostatic concentrations lowered at least 100 times the intensity of the erythromycin resistance plasmid in vitro on mixed cultivation of the staphylococcal cells of the donor (strain 8325/11 de) and the recipient (strain 825-1). The cationic SAS, i. e. roc cal, chlorhexidine had no such capacity. The above anionic and cationic SAS had an antiphage effect with respect to the transducing staphylococcal bacteriophages of the serological group B (80, 85, 52A, 53). Such an effect (on the example of sodium alkylsulfates) increased with prolongation of the alkyl radical from C8 to C14. A decrease in the transduction intensity of the erythromycin resistant plasmid in staphylococci was observed in the presence of the anionic SAS either possessing (alkylsulfates, iodonate) or not (sulfonol NP-3) the antiphage activity.

[Effect of the anthracycline group antibiotics, mitomycin C and bruneomycin, on the transduction of drug resistance in staphylococci]

The effect of various concentrations of antitumor antibiotics, such as carminomycin, rubomycin, adriamycin, mitomycin C and bruneomycin on transduction of erythromycin resistance from the donor strain 8325 P II/de of Staph, aureus to the recipient strain 8325-I in different transduction systems was studied. It was shown that the above antibiotics inhibited the transduction in the systems with constant presence of the drugs. Preliminary treatment of the recipient cells with the drugs in the subbacteriostatic doses did not decrease the transfer frequency. The preliminary treatment of the donor cells resulted in an increase in the phase titer and the transfer frequency in the "preliminary-treated donor + recipient" system.

[Effectivity of murein preparations in the phage inhibition test--effect of Ca++ions and EDTA]

The inactivating efficacy for the typing phages 54, 83A, and 187 of the peptidoglycan of Staphylococcus aureus is decreased by increasing the Ca++-content of the medium; the irreversible inhibition of phage 187 becomes reversible. The percentage of its inhibition is proportional to the Ca++-content of the medium. Minute amounts of phage 187 bound irreversibly under Ca++-deprivation can be loosened by addition of Ca++-ions. Addition of EDTA up to the equivalence concentration of Ca++ present in the medium has no influence. Addition of EDTA up to the tenfold equivalence causes a significant increase of the inactivating efficacy of the peptidoglycan.

Microbial flora of atopic dermatitis

The microbial flora of dermatitic skin, uninvolved skin, and the anterior nares of subjects with atopic eczema were investigated. The carriage rate of Staphylococcus aureus was 79% for the anterior nares, 76% for the uninvolved skin (normal skin), and 93% for lesions. The counts of S aureus were 7.5 X 10(4)/sq cm in lesions and 7.1 X 10(3)/sq cm on adjacent normal skin. Staphylococcus aureus was the predominant organism in the lesions and constituted 91% of the total aerobic bacterial flora. The coagulase-negative staphylococci were the second predominant organisms (9%). On normal skin, coagulase-negative staphylococci were the predominant organisms, constituting 63% of the total flora, followed by S aureus (30% of the bacterial flora). The micrococci counts were lower in the lesions (1.6 X 10(2)/sq cm) and higher on normal skin (9.5 X 10(2)/sq cm). Lipophilic diphtheroids were fewer on normal skin (6.7 X 10/sq cm), and there were none in the lesions. Fifty-eight percent of the strains belonged to group 3, and 38% were nontypeable. Staphylococcus aureus strains belonging to phage groups 2 and 4 were not detected.

Staphylococcal polysaccharide products inhibitory to Staphylococcus aureus bacteriophage

Four products derived from Staphylococcus aureus cultures were partially purified and tested for inhibitory activity against staphylococcal phage. Phage inhibition, a specific stable phenomenon, was concentration dependent. All inhibitory products contained carbohydrate and amino acids, the most active (phage 73 lysate product) having a high carbohydrate content. Galactose, glucosamine, five or six amino acids, and possibly 3-O-methylglucose and a uronic acid were found as components in all active preparations. However, the exact nature of the active material remains undetermined.

[Factors influencing transduction of genetic determinants of penicillinase activity and pathogenicity in staphylococcus aureua. II. Antiphage activity of acridine derivatives]

Acridine dyes examined earlier (acrichine, acridine orange, proflavine and rivanol) and newly-synthesized preparations (acridines No. No. 37--40) were studied in the capacity of nonspecific agents influencing the lytic cycle in development of staphylococcus phages. Acrichine and acridine No. 37 failed to prevent lysis of the indicator staphylococcus cultures (strains 16/160 and 8325) by bacteriophages; proflavine, rivanol, acridines No. No. 39--40 produced a marked inhibitory effect; acridine orange and acridine No. 38 inhibited the staphylococcus lysis completely. Some preparations could be used to investigate the transduction phenomenon.

Phage types of Staphylococcus aureus in one hospital 1961-72

Between 1961 and 1972, 4547 independent strains of Staphylococcus aureus isolated from one hospital were examined for phage type. After 1967 there was a decline in the number of strains received, which we consider reflects a decline in the number of infections in the hospital, and which was largely accounted for by a great reduction in the number of strains in four ;epidemic' types. Overall, the number of multiple-resistant staphylococci received also declined; this was in part due to the decline in the epidemic types and in part to a reduction in the proportion of multiple-resistant strains of all types.

Effect of protein A on adsorption of bacteriophages to Staphylococcus aureus

Experiments were performed to determine if protein A influenced the association of bacteriophages with Staphylococcus aureus. Bacteriophage adsorption was compared in a S. aureus strain rich in protein A and mutants of this strain with very little protein A, in a strain with little protein A, and in mutants of this strain with increased protein A. In addition, the effect of growth in mannitol-salt broth and trypsin digestion (known to reduce protein A) on bacteriophage absorption was measured. There was an inverse relationship between protein A content of strains and the quantity of bacteriophage absorbed. However, no inhibition of staphylococcal phages was obtained with purified soluble protein A. Protein A as a surface component rendered the bacteria more resistant to adsorption of staphylococcal typing phages presumably by masking the phage receptor sites. When protein A-deficient mutants were incubated with bacteriophages, there was survival of staphylococci with increased protein A content probably due to a selective action.

Mode of action of a Staphylococcus epidermidis bacteriocin

Staphylococcin 1580, a bacteriocin produced by Staphylococcus epidermidis 1580, is bactericidal to sensitive cells of many gram-positive bacteria and stable staphylococcal L-forms. The bacteriocin inhibited simultaneously the syntheses of deoxyribonucleic acid, ribonucleic acid, and protein, and caused neither degradation of deoxyribonucleic acid nor induction of phages in lysogenic, sensitive cells. After 1 hr of treatment, extensive degradation of ribonucleic acid occurred, which was accompanied by leakage of ultraviolet-absorbing material out of the cell. The incorporation of glucose in acid-precipitable and glycogenlike material was inhibited. Furthermore, the staphylococcin inhibited the transport of glucose, glutamic acid, rubidium ions, and o-nitrophenyl-beta-galactoside. The uptake of oxygen was only gradually affected, but the intracellular adenosine triphosphate level fell rapidly to 15% of the control value. The motility of sensitive Bacillus subtilis cells was markedly reduced on treatment. Staphylococcin 1580 exhibited no phospholipase activity. The phenomena are interpreted as resulting from an altered conformation and composition of the membrane, from an inhibition of transport through the membrane, or from a combination of these effects.

6(p-Hydroxyphenylazo)-uracil: a reversible, selective inhibitor of the replication of deoxyribonucleic acid of staphylococcal bacteriophage P11-M15

6(p-Hydroxyphenylazo)-uracil (HPUra), a selective inhibitor of the semiconservative replication of deoxyribonucleic acid (DNA) of gram-positive bacteria, was found to inhibit the replication of DNA of bacteriophage P11-M15, a virulent derivative of the temperate Staphylococcus aureus bacteriophage P11. At appropriate concentration, HPUra inhibited DNA synthesis by P11-M15-infected S. aureus immediately and completely, regardless of the stage of the lytic cycle at which infected cells were exposed to drug. The effect of HPUra was reversible since the capacity of inhibited, infected cells to replicate phage DNA and produce mature phage could be restored by removal of HPUra from incubation media. Concentrations of HPUra which completely inhibited the replication of P11-M15 in its drug-sensitive host did not inhibit the replication of this phage or its DNA in several drug-resistant host mutants. HPUra also did not inhibit the replication of two other serologically distinct, virulent staphylococcal bacteriophages, P1 and 44AHJD, in drug-sensitive hosts.