The basic phage set for typing bovine staphylococci

Phage Activity against Planktonic and Biofilm Staphylococcus aureus Periprosthetic Joint Infection Isolates

We recently reported the successful treatment of a case of periprosthetic joint infection (PJI) with phage. Phage activity against bacteria causing PJI has not been systematically evaluated. Here, we examined the in vitro activity of seven phages against 122 clinical isolates of Staphylococcus aureus recovered between April 1999 and February 2018 from subjects with PJI. Phages were assessed against planktonic and biofilm phenotypes. Activity of individual phages was demonstrated against up to 73% of bacterial isolates in the planktonic state and up to 100% of biofilms formed by isolates that were planktonically phage susceptible. Susceptibility to phage was not correlated with small-colony-variant phenotype for planktonic or biofilm bacteria; correlation between antibiotic susceptibility and planktonic phage susceptibility and between biofilm phage susceptibility and strength of biofilm formation were noted under select conditions. These results demonstrate that phages can infect S. aureus causing PJI in both planktonic and biofilm phenotypes, and thus are worthy of investigation as an alternative or addition to antibiotics in this setting.

Characteristics of Staphylococcus aureus strains isolated from bovine mastitic milk: bacteriophage and antimicrobial agent susceptibility, and enterotoxigenicity

Staphylococcus aureus strains isolated from bovine mastitic milk in Trinidad were examined for their susceptibility to bacteriophages and antimicrobial agents and their ability to produce enterotoxins. Phage 42D was used to screen for bovine strains of S. aureus in milk. Of 250 strains tested, 224 (89.6%) were sensitive to phages in the international phage set (IPS), 85 (34.0%) were resistant to antimicrobial agents and 134 (53.6%) were enterotoxigenic. Strains lysed by phages in various groups (mixed) were prevalent, 145 (58.0%), followed by strains sensitive to groups III (17.0%) and I (8.8%) phages. A total of 72 (28.8%) strains were lysed by phage 42D either alone or with others. Resistance to penicillin was most common with 59 (23.6%) strains while 44 (17.6%) and 43 (17.2%) strains were resistant to ampicillin and triple sulphur respectively. Only 3 (1.2%) strains were resistant to methicillin. Prevalence of resistance to penicillin (12.5%) amongst phage 42D-sensitive strains was significantly (P < or = 0.01; X2) lower than for strains not lysed by phage 42D (28.1%) but strains susceptible to phage 42D were significantly (P < or = 0.05; X2) more resistant (4.2%) to methicillin than those not lysed by the phage (0.0%). Amongst 134 enterotoxigenic strains, 32 (23.9%), 77 (57.5%), 67 (50.0%) and 21 (15.7%) produced staphylococcal enterotoxins A(SEA), B(SEB), C(SEC) and D(SED) respectively either alone or mixed. SEB and SEC were significantly (P < or = 0.01; X2) more produced than either SEA or SED. Strains lysed by groups IV, i.e. 42D (62.5%), and III (56.7%) were more enterotoxigenic than those sensitive to phages in groups II (45.5%) and non-typable (46.2%) but the differences were not statistically significant (P > or = 0.05; X2). Strains lysed by group II phages (72.7%) were significantly (P < or = 0.05; X2) more resistant to antimicrobial agents than those lysed by phage 42D (18.8%). It was concluded that bovine mastitis strains of S. aureus in Trinidad were highly susceptible to bacteriophages and antimicrobial agents and enterotoxigenic and less than one-third may be considered to be bovine strains.

Molecular population genetic analysis of Staphylococcus aureus recovered from cows

Staphylococcus aureus is one of the most common causes of bovine mastitis. To estimate genetic relationships among S. aureus strains recovered from cows, 357 isolates from milk samples from worldwide localities were examined for electrophoretic variation at 13 metabolic-enzyme loci. Thirty-nine electrophoretic types which represented distinctive multilocus enzyme genotypes were identified, and nearly 90% of all isolates were assigned to one of eight clones. Genetic heterogeneity was found among organisms recovered from dairy herds from which multiple isolates were obtained, indicating that the S. aureus population in a single herd can be multiclonal. Although humans and cows shared 7 of the 39 S. aureus clones, each clone was predominantly associated with one of these host species. These results are consistent with the concept of host specialization among S. aureus clones and imply that successful transfer of bacteria between humans and cows is limited.

Genomic fingerprints of Staphylococcus aureus of bovine origin by polymerase chain reaction-based DNA fingerprinting

Staphylococcus aureus (n = 75) isolated from mammary secretions of cows with subclinical and clinical mastitis from several geographic locations in the USA were examined using polymerase chain reaction-based DNA fingerprinting. DNA fingerprints were produced using a synthetic oligonucleotide primer (5'GTAACGCC3') to produce a distinct spectrum of amplified DNA fragments facilitating a high degree of resolution for differentiating S. aureus strains. PCR-based DNA fingerprinting grouped the 75 S. aureus isolates into 19 distinct profiles. The technique differentiated closely related strains within and between geographic locations. Findings suggest that certain types are found across geographic regions suggesting a common clonal type. Within herd data suggest heterogeneity among subclinical and clinical isolates of S. aureus strains. Compared to existing typing methods, PCR-based DNA fingerprinting is easy to perform and interpret. Use of PCR-based DNA fingerprinting may allow for a more detailed investigation of the epidemiology of S. aureus mastitis in dairy cows.

Plasmid pattern analysis of Staphylococcus species isolated from bovine mammary secretions

Plasmid profiles of staphylococci isolated from bovine mammary secretions were heterogeneous as shown by the study of 94 isolates representing six species. Plasmids were identified in 19 of 94 staphylococcal isolates. Number of plasmids per isolate varied from 1 to 4. Size of plasmids ranged from 1.2 to 45 MDa; however, most were between 1.8 and 4.8 MDa. Some isolates with identical plasmid profiles were observed within and between species. Plasmid profiles observed in this study suggest that no specific plasmid pattern occurs within a species. Ability to differentiate isolates was not enhanced when antibiograms were used in conjunction with plasmid profiles. Plasmid pattern analysis does not appear to be an adequate method for discriminating between isolates of a species and would likely provide limited epidemiological information regarding staphylococci of bovine origin.

Restriction endonuclease fingerprinting of genomic DNA of Staphylococcus species of bovine origin

Fifty-one staphylococcal isolates from mammary secretions of cows with subclinical mastitis were examined by antibiograms and DNA restriction endonuclease fingerprinting (REF). DNA REF differentiated closely related strains of each species isolated from mammary secretions of different mammary glands of the same cow and from the same mammary gland at different periods of the lactation cycle. In addition, REF analysis provided evidence concerning persistence of infection in the same or different mammary gland over different periods of the lactation cycle, and occurrence of infection with similar and dissimilar strains of each Staphylococcus species. Antibiograms were of limited value in differentiating closely related strains. The ease by which REF analysis can be performed together with the reproducibility and clarity of REF patterns suggest that this technique is useful for differentiating closely related and unrelated strains of Staphylococcus species isolated from bovine mammary secretions.