Injectable Phage-Loaded Microparticles Effectively Release Phages to Kill Methicillin-Resistant Staphylococcus aureus

The increasing prevalence of bacterial multidrug antibiotic resistance has led to a serious threat to public health, emphasizing the urgent need for alternative antibacterial therapeutics. Lytic phages, a class of viruses that selectively infect and kill bacteria, offer promising potential as alternatives to antibiotics. However, injectable carriers with a desired release profile remain to be developed to deliver them to infection sites. To address this challenge, phage-loaded microparticles (Phage-MPs) have been developed to deliver phages to the infection site and release phages for an optimal therapeutic effect. The Phage-MPs are synthesized by allowing phages to be electrostatically attached onto the porous polyethylenimine-modified silk fibroin microparticles (SF-MPs). The high specific surface area of SF-MPs allows them to efficiently load phages, reaching about 1.25 × 1010 pfu per mg of microparticles. The Phage-MPs could release phages in a controlled manner to achieve potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Unlike the diffuse biodistribution of free phages post-intraperitoneal injection, Phage-MPs could continuously release phages to effectively boost the local phage concentration at the bacterial infection site after they are intraperitoneally injected into an abdominal MRSA-infected mouse model. In a mouse abdominal MRSA infection model, Phage-MPs significantly reduce the bacterial load in major organs, achieving an efficient therapeutic effect. Furthermore, Phage-MPs demonstrate outstanding biocompatibility both in vitro and in vivo. Overall, our research lays the foundation for a new generation of phage-based therapies to combat antibiotic-resistant bacterial infections.

LysSYL: a broad-spectrum phage endolysin targeting Staphylococcus species and eradicating S. aureus biofilms

BACKGROUND

Staphylococcus aureus and its single or mixed biofilm infections seriously threaten global public health. Phage therapy, which uses active phage particles or phage-derived endolysins, has emerged as a promising alternative strategy to antibiotic treatment. However, high-efficient phage therapeutic regimens have yet to be established.

RESULTS

In this study, we used an enrichment procedure to isolate phages against methicillin-resistant S. aureus (MRSA) XN108. We characterized phage SYL, a new member of the Kayvirus genus, Herelleviridae family. The phage endolysin LysSYL was expressed. LysSYL demonstrated stability under various conditions and exhibited a broader range of efficacy against staphylococcal strains than its parent phage (100% vs. 41.7%). Moreover, dynamic live/dead bacterial observation demonstrated that LysSYL could completely lyse MRSA USA300 within 10 min. Scan and transmission electron microscopy revealed evident bacterial cell perforation and deformation. In addition, LysSYL displayed strong eradication activity against single- and mixed-species biofilms associated with S. aureus. It also had the ability to kill bacterial persisters, and proved highly effective in eliminating persistent S. aureus when combined with vancomycin. Furthermore, LysSYL protected BALB/c mice from lethal S. aureus infections. A single-dose treatment with 50 mg/kg of LysSYL resulted in a dramatic reduction in bacterial loads in the blood, liver, spleen, lungs, and kidneys of a peritonitis mouse model, which resulted in rescuing 100% of mice challenged with 108 colony forming units of S. aureus USA300.

CONCLUSIONS

Overall, the data provided in this study highlight the strong therapeutic potential of endolysin LysSYL in combating staphylococcal infections, including mono- and mixed-species biofilms related to S. aureus.

The stability of Staphylococcal bacteriophages with commonly used prosthetic joint infection lavage solutions

The aim of this study was to assess the viability of four Staphylococcal bacteriophages when exposed to different concentrations of commonly used lavage solutions in the surgical treatment of prosthetic joint infections (PJI). Four tailed Staphylococcal bacteriophages and six different lavage solutions (chlorhexidine 4%, hydrogen peroxide 3%, acetic acid 3%, povidone iodine 10%, sodium hypochlorite 0.5%, and Vashe solution) at 100%, 1%, and 0.01% concentrations were used in this experiment. In addition, the temporal impact of exposing bacteriophages to these lavage solutions was also evaluated at 5-min exposures and 24-h exposures. The results show that the titers of the four bacteriophages were statistically significantly decreased for all lavage solutions (100% and 1%) at 5-min exposures and 24-h exposures. However, with 0.01% concentrations of the lavage solutions, only acetic acid caused a statistically significant decrease in bacteriophage titers compared to normal saline control. Our findings suggest that tailed Staphylococcal bacteriophages do not remain stable in high concentrations of the most commonly used lavage solutions. However, at very dilute concentrations the bacteriophages do remain viable. This has important clinical ramifications in that it shows when using bacteriophage therapy for PJI it is critical to thoroughly wash out any lavage solutions before the introduction of therapeutic bacteriophages especially when acetic acid is used.

Bacteriophage therapy for drug-resistant Staphylococcus aureus infections

Drug-resistant Staphylococcus aureus stands as a prominent pathogen in nosocomial and community-acquired infections, capable of inciting various infections at different sites in patients. This includes Staphylococcus aureus bacteremia (SaB), which exhibits a severe infection frequently associated with significant mortality rate of approximately 25%. In the absence of better alternative therapies, antibiotics is still the main approach for treating infections. However, excessive use of antibiotics has, in turn, led to an increase in antimicrobial resistance. Hence, it is imperative that new strategies are developed to control drug-resistant S. aureus infections. Bacteriophages are viruses with the ability to infect bacteria. Bacteriophages, were used to treat bacterial infections before the advent of antibiotics, but were subsequently replaced by antibiotics due to limited theoretical understanding and inefficient preparation processes at the time. Recently, phages have attracted the attention of many researchers again because of the serious problem of antibiotic resistance. This article provides a comprehensive overview of phage biology, animal models, diverse clinical case treatments, and clinical trials in the context of drug-resistant S. aureus phage therapy. It also assesses the strengths and limitations of phage therapy and outlines the future prospects and research directions. This review is expected to offer valuable insights for researchers engaged in phage-based treatments for drug-resistant S. aureus infections.

The stability of Staphylococcal bacteriophage in presence of local vancomycin concentrations used in clinical practice

PURPOSE

To evaluate the stability of a clinically used Staphylococcal bacteriophage with doses of vancomycin that are encountered with local administration of vancomycin for musculoskeletal infections.

METHODS

A Staphylococcal bacteriophage was evaluated for stability in different pH ranges. Then that same bacteriophage was evaluated for stability with different concentrations of vancomycin and with vancomycin biodegradable antibiotic beads.

RESULTS

The bacteriophage had stability within a pH range of 4-10. There was a statistically significant (P < 0.05) decrease in the amount of bacteriophage over 24 h for vancomycin concentrations of 10 mg/mL and 100 mg/mL compared to lower vancomycin concentrations (1 mg/mL, 0.1 mg/mL and normal saline). However, no statistically significant decrease in the amount of bacteriophage was seen with biodegradable vancomycin beads over 24 h.

CONCLUSION

These findings have important clinical ramifications in that they show local administration of bacteriophages with concomitant local vancomycin powder therapy should be avoided. Moreover, these findings should spearhead further research into bacteriophage stability in in vivo environments.

Dual pathogenicity island transfer by piggybacking lateral transduction

Lateral transduction (LT) is the process by which temperate phages mobilize large sections of bacterial genomes. Despite its importance, LT has only been observed during prophage induction. Here, we report that superantigen-carrying staphylococcal pathogenicity islands (SaPIs) employ a related but more versatile and complex mechanism of gene transfer to drive chromosomal hypermobility while self-transferring with additional virulence genes from the host. We found that after phage infection or prophage induction, activated SaPIs form concatamers in the bacterial chromosome by switching between parallel genomic tracks in replication bubbles. This dynamic life cycle enables SaPIbov1 to piggyback its LT of staphylococcal pathogenicity island vSaα, which encodes an array of genes involved in host-pathogen interactions, allowing both islands to be mobilized intact and transferred in a single infective particle. Our findings highlight previously unknown roles of pathogenicity islands in bacterial virulence and show that their evolutionary impact extends beyond the genes they carry.

Phage and Antibiotic Combinations Reduce Staphylococcus aureus in Static and Dynamic Biofilms Grown on an Implant Material

Staphylococcus aureus causes the majority of implant-related infections. These infections present as biofilms, in which bacteria adhere to the surface of foreign materials and form robust communities that are resilient to the human immune system and antibiotic drugs. The heavy use of broad-spectrum antibiotics against these pathogens disturbs the host's microbiome and contributes to the growing problem of antibiotic-resistant infections. The use of bacteriophages as antibacterial agents is a potential alternative therapy. In this study, bioluminescent strains of S. aureus were grown to form 48-h biofilms on polyether ether ketone (PEEK), a material used to manufacture orthopaedic implants, in either static or dynamic growth conditions. Biofilms were treated with vancomycin, staphylococcal phage, or a combination of the two. We showed that vancomycin and staph phages were able to independently reduce the total bacterial load. Most phage-antibiotic combinations produced greater log reductions in surviving bacteria compared to single-agent treatments, suggesting antimicrobial synergism. In addition to demonstrating the efficacy of combining vancomycin and staph phage, our results demonstrate the importance of growth conditions in phage-antibiotic combination studies. Dynamic biofilms were found to have a substantial impact on apparent treatment efficacy, as they were more resilient to combination treatments than static biofilms.

Microcalorimetry: A Novel Application to Measure In Vitro Phage Susceptibility of Staphylococcus aureus in Human Serum

Infections involving antibiotic resistant Staphylococcus aureus (S. aureus) represent a major challenge to successful treatment. Further, although bacteriophages (phages) could be an alternative to antibiotics, there exists a lack of correlation in phage susceptibility results between conventional in vitro and in vivo assays. This discrepancy may hinder the potential implementation of bacteriophage therapy. In this study, the susceptibility of twelve S. aureus strains to three commercial phage cocktails and two single phages was assessed. These S. aureus strains (including ten clinical isolates, five of which were methicillin-resistant) were compared using four assays: the spot test, efficiency of plating (EOP), the optical density assay (all in culture media) and microcalorimetry in human serum. In the spot test, EOP and optical density assay, all cocktails and single phages lysed both methicillin susceptible and methicillin resistant S. aureus strains. However, there was an absence of phage-mediated lysis in high concentrations of human serum as measured using microcalorimetry. As this microcalorimetry-based assay more closely resembles in vivo conditions, we propose that microcalorimetry could be included as a useful addition to conventional assays, thereby facilitating more accurate predictions of the in vivo susceptibility of S. aureus to phages during phage selection for therapeutic purposes.

Structure and host specificity of Staphylococcus epidermidis bacteriophage Andhra

Staphylococcus epidermidis is an opportunistic pathogen of the human skin, often associated with infections of implanted medical devices. Staphylococcal picoviruses are a group of strictly lytic, short-tailed bacteriophages with compact genomes that are attractive candidates for therapeutic use. Here, we report the structure of the complete virion of S. epidermidis-infecting phage Andhra, determined using high-resolution cryo-electron microscopy, allowing atomic modeling of 11 capsid and tail proteins. The capsid is a T = 4 icosahedron containing a unique stabilizing capsid lining protein. The tail includes 12 trimers of a unique receptor binding protein (RBP), a lytic protein that also serves to anchor the RBPs to the tail stem, and a hexameric tail knob that acts as a gatekeeper for DNA ejection. Using structure prediction with AlphaFold, we identified the two proteins that comprise the tail tip heterooctamer. Our findings elucidate critical features for virion assembly, host recognition, and penetration.

Quick bacteriophage-mediated bioluminescence assay for detecting Staphylococcus spp. in sonicate fluid of orthopaedic artificial joints

Staphylococcus spp. accounts for up to two thirds of all microorganisms causing prosthetic joint infections, with Staphylococcus aureus and Staphylococcus epidermidis being the major cause. The present study describes a diagnostic model to detect staphylococci using a specific bacteriophage and bioluminescence detection, exploring the possibility of its use on sonicate fluid of orthopaedic artificial joints. Intracellular adenosine-5'-triphosphate release by bacteriophage mediated lysis of staphylococci was assessed to determine optimal parameters for detection. With the optimized method, a limit of detection of around 103 CFU/mL was obtained after incubation with bacteriophage for 2 h. Importantly, sonicate fluid did not prevent the ability of bacteriophage to infect bacteria and all simulated infected sonicate fluid as well as 6 clinical samples with microbiologically proven staphylococcal infection were detected as positive. The total assay took approximately 4 h. Collectively, the results indicate that the developed method promises a rapid, inexpensive and specific diagnostic detection of staphylococci in sonicate fluid of infected prosthetic joints. In addition, the unlimited pool of different existing bacteriophages, with different specificity for all kind of bacteria gives the opportunity for further investigations, improvements of the current model and implementation in other medical fields for the purpose of the establishment of a rapid diagnosis.

Romulus and Remus, two phage isolates representing a distinct clade within the Twortlikevirus genus, display suitable properties for phage therapy applications

The renewed interest in controlling Staphylococcus aureus infections using their natural enemies, bacteriophages, has led to the isolation of a limited number of virulent phages so far. These phages are all members of the Twortlikevirus, displaying little variance. We present two novel closely related (95.9% DNA homology) lytic myoviruses, Romulus and Remus, with double-stranded DNA (dsDNA) genomes of 131,333 bp and 134,643 bp, respectively. Despite their relatedness to Staphylococcus phages K, G1, ISP, and Twort and Listeria phages A511 and P100, Romulus and Remus can be proposed as isolates of a new species within the Twortlikevirus genus. A distinguishing feature for these phage genomes is the unique distribution of group I introns compared to that in other staphylococcal myoviruses. In addition, a hedgehog/intein domain was found within their DNA polymerase genes, and an insertion sequence-encoded transposase exhibits splicing behavior and produces a functional portal protein. From a phage therapy application perspective, Romulus and Remus infected approximately 70% of the tested S. aureus isolates and displayed promising lytic activity against these isolates. Furthermore, both phages showed a rapid initial adsorption and demonstrated biofilm-degrading capacity in a proof-of-concept experiment.

Bacteriophage formation without bacterial growth; formation of staphylococcus phage in the presence of bacteria inhibited by penicillin

Bacteriophage will increase 100,000 times in Staphylococcus muscae cultures whose multiplication has been completely inhibited by penicillin.

The concerted action of lactoferrin and bacteriophages in the clearance of bacteria in sublethally infected mice

BACKGROUND

Both lactoferrin (LF) and bacteriophages are potent antibacterial agents. LF is contained in the secretory fluids of mammals and bacteriophages are specific bacterial viruses.

OBJECTIVES

The aim of this investigation was to determine whether combined treatment of infected mice may allow lowering the therapeutic dose of specific bacteriophages for Escherichia coli and Staphylococcus aureus.

MATERIALS/METHODS

CBA mice were infected intravenously (i.v.) with sublethal doses of E. coli or S. aureus and the specific T4 or A5 bacteriophages, respectively, were administered intraperitoneally (i.p.) or per os one hour following infection. The numbers of colony-forming units (CFUs) were determined in the livers after 24 hours.

RESULTS/CONCLUSIONS

Comparative administration of bacteriophages i.p. or per os showed that both routes of administration were equally efficacious in the protective action of bacteriophages. The bacteriophages were still very potent in reducing CFU numbers in the liver at a dose of 10(5)/mouse. Application of bovine lactoferrin (LF), 10 mg i.v., 24 h before infection, was also very effective in reducing CFU numbers. Using suboptimal (10(3)-10(4)) doses of bacteriophages and administration of LF, a more potent protective effect in reducing the CFU numbers in the infected mice was demonstrated. The combined effect of LF and bacteriophages in reducing CFU numbers was significantly higher than the effects of either agent alone. The study demonstrated that the combined application of LF and bacteriophages can significantly lower (1000 times) the effective dose of bacteriophages in reducing CFU numbers in infected mice.

[Staphylococcus aureus prevalence among hospitalized patients]

OBJECTIVE. To determine the prevalence of Staphylococcus aureus strains among hospitalized patients at the beginning of their hospitalization and during their treatment and the resistance of strains to antibiotics, and to evaluate epidemiologic characteristics of these strains. PATIENTS AND METHODS. Sixty-one patients treated at the Department of Cardiac, Thoracic and Vascular Surgery were examined. Identification of Staphylococcus aureus strains was performed using plasmacoagulase and DNase tests. The resistance of Staphylococcus aureus to antibiotics, beta-lactamase production, phagotypes, and phagogroups were determined. The isolated Staphylococcus aureus strains were tested for resistance to methicillin by performing disc diffusion method using commercial discs (Oxoid) (methicillin 5 microg per disk and oxacillin 1 microg per disk). RESULTS. A total of 297 Staphylococcus aureus strains were isolated. On the first day of hospitalization, the prevalence rate of Staphylococcus aureus strains among patients was 67.3%, and it statistically significantly increased to 91.8% on days 7-10 of hospitalization (P<0.05). During hospitalization, patients were colonized with Staphylococcus aureus strains resistant to cephalothin (17.6% of patients, P<0.05), cefazolin (14.6%, P<0.05), tetracycline (15.0%, P<0.05), gentamicin (37.7%, P<0.001), doxycycline (30.7%, P<0.001), and tobramycin (10.6%, P>0.05). Three patients (4.9%) were colonized with methicillin-resistant Staphylococcus aureus strains, belonging to phage group II phage type 3A and phage group III phage types 83A and 77; 22.6-25.5% of Staphylococcus aureus strains were nontypable. During hospitalization, the prevalence rate of phage group II Staphylococcus aureus strains decreased from 39.6% to 5.7% (P<0.05) and the prevalence rate of phage group III Staphylococcus aureus strains increased to 29.5% (P<0.001). CONCLUSIONS. Although our understanding of Staphylococcus aureus is increasing, well-designed community-based studies with adequate risk factor analysis are required to elucidate further the epidemiology of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. Surveillance of methicillin-resistant Staphylococcus aureus provides relevant information on the extent of the methicillin-resistant Staphylococcus aureus epidemic, identifies priorities for infection control and the need for adjustments in antimicrobial drug policy, and guides intervention programs.

DnaB and DnaI temperature-sensitive mutants of Staphylococcus aureus: evidence for involvement of DnaB and DnaI in synchrony regulation of chromosome replication

DnaB and DnaI proteins conserved in low-GC content Gram-positive bacteria are apparently involved in helicase loading at the replication initiation site and during the restarting of stalled replication forks. In this study, we found five novel dnaB mutants and three novel dnaI mutants by screening 750 temperature-sensitive Gram-positive Staphylococcus aureus mutants. All of the mutants had a single amino acid substitution in either DnaB or DnaI that controlled temperature-sensitive growth, as confirmed by transduction experiments using phage 80alpha. DNA synthesis as measured by [(3)H]thymine incorporation, origin-to-terminus ratios and flow cytometric analysis revealed that the dnaB and dnaI mutants were unable to initiate DNA replication at restrictive temperatures, which is similar to previous findings in Bacillus subtilis. Furthermore, some of the mutants were found to exhibit asynchrony in the initiation of DNA replication. Also, a fraction of the dnaI mutant cells showed arrested replication, and the dnaI mutant tested was sensitive to mitomycin C, which causes DNA lesions. These results suggest that DnaB and DnaI are required not only for replication initiation and but also for regulation of its synchrony, and they provide support for the involvement of DnaI activity in the restart of arrested replication forks in vivo.

[Phage types of Staphylococcus aureus strains and their antibiotic resistance in carriers of medical students population]

The phage types of 78 S. aureus strains isolated from nose swabs obtained from a medical students in 2005 -2006 was determined and antibiotic resistance of the phage types was analysed. 680 students were tested in order to obtain the strains and 11.5% of them were carriers of S. aureus. Phage typing was performed using basic set of23 phages and 3 additional phages: 88, 89 and 187. Drug resistance was determined by the disc-diffusion method. The most frequent in studied population were the group III (21.8%) and strains lysed by phages belonging to varied groups (21.8%). Highly different phage patterns were observed among strains belonging to each of the group. Strains belonging to the group III as the strains lysed by phages from varied groups were most frequently resistant only to penicillin (52,9% respectively). Resistance to penicillin was also most often observed in the strains belonging to another groups and phage types. Usefulness of the additional phages 88,89 and 187 was in the investigations as no more than 51% of strains was lysed by this phages.

[Staphylococcus aureus prevalence among preschool- and school-aged pupils]

OBJECT

To determine the prevalence and incidence of Staphylococcus aureus strains among preschool- and school-aged pupils and susceptibility of these strains to antimicrobial materials.

MATERIAL AND METHODS

A study of 243 preschool- and 300 school-aged pupils was conducted during 2003-2004. Identification of Staphylococcus aureus was made with plasmacoagulase and DNase tests. The resistance of Staphylococcus aureus to antibiotics, beta-lactamase activity, phagotypes, and phage groups were determined. The isolated Staphylococcus aureus strains were tested for resistance to methicillin by performing disc diffusion method using commercial discs (Oxoid) (methicillin 5 microg per disk and oxacillin 1 microg per disk).

RESULTS

A total of 292 (53.8%) Staphylococcus aureus strains were isolated and identified (113 (46.5%) from preschool- and 179 (59.7%) from school-aged pupils). The prevalence of Staphylococcus aureus strains among preschool-aged pupils varied from 46.5% to 47%. It increased to 59.0% (P>0.05) among schoolchildren aged from 11 to 15 years and to 73.0% (P<0.001) among schoolchildren aged from 16 to 19 years. Six methicillin-resistant Staphylococcus aureus strains were isolated: two (1.8%) of them were from preschool-aged and four (2.2%) from school-aged pupils. The prevalence of Staphylococcus aureus strains with beta-lactamase activity increased from 70.7 to 76.6% in preschool-aged pupils, and it varied from 72.0 to 79.0% in school-aged pupils (P>0.05). Staphylococcus aureus strains of phage group II (32.2-43.4%) were prevailing; nontypable Staphylococcus aureus strains made up 19.2-33.6%.

CONCLUSIONS

The prevalence of Staphylococcus aureus among preschool-aged children is 41.7 to 48.8%, and it increases among 9th-12th-grade pupils (73.0%, P<0.001). Some Staphylococcus aureus strains (2.1%) were resistant to methicillin. Staphylococcus aureus strains of phage group II (39.0%, P<0.05) are most prevalent among preschool- and school-aged pupils. Pupils were colonized with methicillin-resistant Staphylococcus aureus strains belonging to phage group III phagotype 83A and 77.

Leukotoxin family genes in Staphylococcus aureus isolated from domestic animals and prevalence of lukM-lukF-PV genes by bacteriophages in bovine isolates

Leukotoxin family genes in Staphylococcus aureus isolated from domestic animals were examined by polymerase chain reaction. LukS and lukF genes were detected in all 48 avian and 72 porcine isolates of S. aureus. LukE and lukD genes, located in a putative staphylococcal pathogenicity island (Sapln3/Saplm3), were recognized in 44 (91.7%) of 48 avian isolates, but these genes were not detected in porcine isolates. In 297 bovine isolates collected from mastitic cow's milk and bulk milk from dairy farms in two regions, lukM and lukF-PV(P83) genes in addition to lukS-lukF and lukE-lukD genes were detected in 100 (62.5%) of the 160 isolates from Ishikawa and in118 (86.1%) of the 137 isolates from Hokkaido. When the lysogeny of S. aureus bovine isolates was examined by treatment with mitomycin C, clearing of the culture due to cell lysis was observed in 34 (91.9%) of 37 lukM-lukF-PV(P83) genes--positive isolates. In addition, we isolated a novel lukM-lukF-PV(P83)-carrying (designated phiLukM), and revealed that the lukM-lukF-PV(P83) genes were located very close to an amidase gene on the temperate phage genomes. These results suggest horizontal transmission of lukM-lukF-PV(P83) genes by temperate bacteriophages in S. aureus of bovine origin.

Staphylococcus aureus resistance to antibiotics and spread of phage types

OBJECTIVE

The aim of this study was to identify the phage groups of Staphylococcus aureus strains, their prevalence, and resistance of different phage groups to antibiotics.

MATERIALS AND METHODS

A total of 294 Staphylococcus aureus strains in Kaunas hospitals were obtained; they were phage typed and their resistance to antibiotics was determined. We used the method of routine dilution to test 17 antibiotics against the isolates. Susceptibility of Staphylococcus aureus to studied antibiotics was estimated on the basis of National Committee for Clinical Laboratory Standards according to minimal inhibition concentration of each antibiotic. Staphylococcus aureus strains were phage typed by the international diagnostic set of Staphylococci bacteriophages (Moscow, Russia).

RESULTS

After evaluating the resistance of obtained Staphylococcus aureus strains to oxacillin/methicillin, it was determined that 5.8% of Staphylococcus aureus were resistant to methicillin. Almost all strains (93.75%) of methicillin-resistant Staphylococcus aureus were susceptible to the fusidic acid, 18.75%--to ciprofloxacin; 31.25% of methicillin-resistant Staphylococcus aureus strains were susceptible to gentamicin, 37.5%--to doxycycline, and just 6.25%--to erythromycin. The strains of methicillin-susceptible Staphylococcus aureus are susceptible to many studied antibiotics. The strains of methicillin-susceptible Staphylococcus aureus are most resistant to penicillin--83.1% and to erythromycin--29.9%. Phage typing revealed that 20.9% of methicillin-susceptible Staphylococcus aureus and 56.2% of methicillin-resistant Staphylococcus aureus were nontypable.

CONCLUSIONS

Using the international set of bacteriophages, 79.1% of methicillin-susceptible Staphylococcus aureus and 43.8% of methicillin-resistant Staphylococcus aureus strains were phage typed. Among the strains of methicillin-resistant Staphylococcus aureus, phagotype 77 of phagogroup III was the most common and among the strains of methicillin-susceptible Staphylococcus aureus--phagotype 3C of phagogroup II.

A change in Belgian epidemic methicillin-resistant Staphylococcus aureus phage types in 2000: phenotypic and genotypic characterization of isolates from a general hospital

During 2000, new methicillin-resistant Staphylococcus aureus (MRSA) epidemic phage types became preponderant in Belgium. In the present study, phenotypic and genotypic characteristics of 130 MRSA isolates from a general Belgian hospital were investigated. The MRSA nature of the isolates was confirmed by coagulase test, oxacillin screen plate test and detection of the mecA gene by polymerase chain reaction. Phage typing categorized the MRSA strains into two main groups: the [O]* types and the [J]* types. SmaI macrorestriction analysis by pulsed-field gel electrophoresis gave the same pulsotype in the majority of strains. All strains of the [O]* and [J]* groups, except one, belonged to this pulsotype. Aminoglycoside-modifying-enzyme genes could only be detected in a minority of strains. Although the epidemic phage types of the mid-1990s appear to have been supplanted by the [O]* and [J]* groups, the MRSA population examined showed a remarkably uniform profile corresponding to the previous major clone B.

Experimental bacteriophage protection against Staphylococcus aureus abscesses in a rabbit model

In a rabbit model of wound infection caused by Staphylococcus aureus, 2 x 10(9) PFU of staphylococcal phage prevented abscess formation in rabbits when it was injected simultaneously with S. aureus (8 x 10(7) CFU) into the same subcutaneous site. Phage multiplied in the tissues. Phages might be a valuable prophylaxis against staphylococcal infection.

mecA Locus diversity in methicillin-resistant Staphylococcus aureus isolates in Brisbane, Australia, and the development of a novel diagnostic procedure for the Western Samoan phage pattern clone

An emerging public health phenomenon is the increasing incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections that are acquired outside of health care facilities. One lineage of community-acquired MRSA (CA-MRSA) is known as the Western Samoan phage pattern (WSPP) clone. The central aim of this study was to develop an efficient genotyping procedure for the identification of WSPP isolates. The approach taken was to make use of the highly variable region downstream of mecA in combination with a single nucleotide polymorphism (SNP) defined by the S. aureus multilocus sequence typing (MLST) database. The premise was that a combinatorial genotyping method that interrogated both a highly variable region and the genomic backbone would deliver a high degree of informative power relative to the number of genetic polymorphisms interrogated. Thirty-five MRSA isolates were used for this study, and their gene contents and order downstream of mecA were determined. The CA-MRSA isolates were found to contain a truncated mecA downstream region consisting of mecA-HVR-IS431 mec-dcs-Ins117, and a PCR-based method for identifying this structure was developed. The hospital-acquired isolates were found to contain eight different mecA downstream regions, three of which were novel. The Minimum SNPs computer software program was used to mine the S. aureus MLST database, and the arcC 272G polymorph was identified as 82% discriminatory for ST-30. A real-time PCR assay was developed to interrogate this SNP. We found that the assay for the truncated mecA downstream region in combination with the interrogation of arcC position 272 provided an unambiguous identification of WSPP isolates.

Comparison of Staphylococcus aureus isolates from bovine and human skin, milking equipment, and bovine milk by phage typing, pulsed-field gel electrophoresis, and binary typing

Staphylococcus aureus isolates (n = 225) from bovine teat skin, human skin, milking equipment, and bovine milk were fingerprinted by pulsed-field gel electrophoresis (PFGE). Strains were compared to assess the role of skin and milking equipment as sources of S. aureus mastitis. PFGE of SmaI-digested genomic DNA identified 24 main types and 17 subtypes among isolates from 43 herds and discriminated between isolates from bovine teat skin and milk. Earlier, phage typing (L. K. Fox, M. Gershmann, D. D. Hancock, and C. T. Hutton, Cornell Vet. 81:183-193, 1991) had failed to discriminate between isolates from skin and milk. Skin isolates from humans belonged to the same pulsotypes as skin isolates from cows. Milking equipment harbored strains from skin as well as strains from milk. We conclude that S. aureus strains from skin and from milk can both be transmitted via the milking machine, but that skin strains are not an important source of intramammary S. aureus infections in dairy cows. A subset of 142 isolates was characterized by binary typing with DNA probes developed for typing of human S. aureus. Typeability and overall concordance with epidemiological data were lower for binary typing than for PFGE while discriminatory powers were similar. Within several PFGE types, binary typing discriminated between main types and subtypes and between isolates from different herds or sources. Thus, binary typing is not suitable as replacement for PFGE but may be useful in combination with PFGE to refine strain differentiation.

Identification and characterization of phage variants of a strain of epidemic methicillin-resistant Staphylococcus aureus (EMRSA-15)

EMRSA-15 is one of the most important strains of epidemic methicillin-resistant Staphylococcus aureus (EMRSA) found in the United Kingdom. It was originally characterized by weak lysis with phage 75 and production of enterotoxin C but not urease. Two variant strains of EMRSA-15 which show a broader phage pattern than the progenitor strain have emerged. A total of 153 recent clinical isolates representing classical EMRSA-15 (55 isolates) or these phage variants (98 isolates) were compared by SmaI macrorestriction profiles in pulsed-field gel electrophoresis (PFGE) as well as by urease and enterotoxin C production. Eight of the 98 isolates were shown to be other unrelated strains by both PFGE and their production of urease, a misidentification rate of 8% by phage typing. Seventy-one EMRSA-15 isolates were enterotoxin C negative, and the majority of these were sensitive to phage 81. Examination of PFGE profiles and Southern blotting studies suggest that the enterotoxin C gene locus is encoded on a potentially mobile DNA segment of ca. 15 kb. After elimination of the eight non-EMRSA-15 isolates, the remaining 145 were characterized by PFGE, yielding 22 profiles. All profiles were within five band differences of at least one other profile. Classical EMRSA-15 isolates showed nine PFGE profiles, with the majority of isolates (68%) in profile B1. Six of these nine PFGE profiles were unique to the classical EMRSA-15 isolates. Among the phage variants of EMRSA-15, 16 profiles were seen, but the majority of isolates (83%) fell into 1 of 4 profiles (B2, B3, B4, and B7) which correlated well with phage patterns. The most divergent PFGE profiles among the EMRSA-15 isolates had as many as 12 band differences from one another, suggesting that in examining isolates belonging to such a temporally and geographically disseminated epidemic strain, the range of PFGE profiles must be regarded as a continuum and analyzed by relating the profiles back to the most common or progenitor profile.

Cloning and expression of cadD, a new cadmium resistance gene of Staphylococcus aureus

A cadmium resistance gene, designated cadD, has been identified in and cloned from the Staphylococcus aureus plasmid pRW001. The gene is part of a two-component operon which contains the resistance gene cadD and an inactive regulatory gene, cadX*. A high degree of sequence similarity was observed between cadD and the cadB-like gene from S. lugdunensis, but no significant similarity was found with either cadA or cadB from the S. aureus plasmids pI258 and pII147. The positive regulatory gene cadX* is identical to cadX from pLUG10 over a stretch of 78 codons beginning at the N terminus, but it is truncated at this point and inactive. Sequence analysis showed that the cadmium resistance operon resides on a 3,972-bp element that is flanked by direct repeats of IS257. The expression of cadD in S. aureus and Bacillus subtilis resulted in low-level resistance to cadmium; in contrast, cadA and cadB from S. aureus induced higher level resistance. However, when the truncated version of cadX contained in pRW001 is complemented in trans with cadX from plasmid pLUG10, resistance increased approximately 10-fold suggesting that the cadmium resistance operons from pRW001 and pLUG10 are evolutionarily related. Moreover, the truncated version of cadX contained in pRW001 is nonfunctional and may have been generated by deletion during recombination to acquire the cadmium resistance element.

Enterotoxins and phage typing of Staphylococcus aureus isolated from clinical material and food in Libya

Enterotoxin was detected in 22 (61.1%) of the 36 S. aureus strains isolated from clinical materials and in 3 (13%) of the 23 S. aureus strains from food samples (P < 0.05). On the basis of individual types of enterotoxin, staphylococcal enterotoxin A (SEA) was produced by 11.1%, SEB by 38.9% and SEC by 22.2% of SS. aureus strains from clinical material. Of the food S. aureus strains, SEC and SED produced by 8.7% and 4.3% respectively. Of the clinical and food S. aureus strains, 52.8% and 39.1%, respectively, were typeable by the 23 phages of International Phage Set. The majority of the typeable S. aureus strains from clinical and food sources belonged to group II being at 22.2% and 17.4% respectively. Furthermore, of the 14 SEB-producing S. aureus, 42.9% were of phage group II. In conclusion, the results obtained indicate that enterotoxin-producing S. aureus strains from clinical materials in Libya are not uncommon; however, certain foods appear not to be the source of such strains. Because of the low susceptibility to bacteriophages shown by S. aureus isolated in Libya, compared to reports from several countries, other methods of typing should be used in conjunction with phage typing in epidemiological investigations concerning this organism.

Studies on the interactions between components of Staphylococcus aureus and Staphylococcus bacteriophage

The cell walls of Staphylococcus aureus are capable of inactivating S. aureus bacteriophage. Furthermore, the cell walls isolated from S. aureus of a given phage type inactivate a variety of different staphylococcal bacteriophages. Under the conditions employed neither the isolated mucopeptide nor teichoic acid components of the cell walls act as bacteriophage receptor.

Lysogeny in staphylococci

Blair, John E. (Hospital for Joint Diseases, New York, N. Y.) and Miriam Carr. Lysogeny in staphylococci. J. Bacteriol. 82:984-993. 1961.-Changes in the phage typing patterns of strains of staphylococci of the 80/81-52/52A/80/81 complex and of phage group III were produced by lysogenization with temperate phages derived from selected strains of Staphylococcus aureus. The phages used were of the serological groups A, B, and F. Certain changes of phage pattern were related to serologically specific prophage immunity; others were nonspecific, or resulted from the conversion of a strain from partial resistance to full sensitivity to certain typing phages. In addition to an alteration of their phage typing pattern, the lysogenization of certain strains by appropriate phages effected a reversal of their susceptibility to penicillin. The capacity to produce toxin was conferred upon certain nontoxigenic strains by lysogenization with a phage derived from a toxigenic strain.