Staphylococcus haemolyticus - an emerging threat in the twilight of the antibiotics age

Fetal Tissues Tested for Microbial Sterility by Culture- and PCR-Based Methods Can be Safely Used in Clinics

Cell preparations to be used in clinical practice must be free of infectious agents. Safety concerns are especially elevated upon the use of human fetal tissues, which are otherwise highly advantageous in cell therapy. We demonstrate that treating fetal samples with antibiotic, extensive washing, and homogenization prior to cryoconservation efficiently removes microbes in general. Screening a large collection by an automatic culture system showed that 89.2% fetal tissue samples were sterile, while contamination was detected in 10.8% samples. Liver and chorion were contaminated more than the brain, kidney, lung, and soft tissues. Broad-range PCR from the bacterial 16s rRNA gene was adopted as a confirmatory assay; however, the concordance between the culture-based and PCR assays was weak. Taxonomic identification was done for contaminated samples by bacteriological methods and sequencing 16s rRNA PCR products. The two approaches revealed different spectra of taxonomic groups sharing only Lactobacillus, the most frequently found genus. In addition, other representatives of vaginal microbiota were detected by culture-based identification, while PCR product sequencing has also revealed a subset of nosocomial microorganisms. Importantly, species known to cause sepsis were identified by both techniques, arguing for their indispensability and mutual complementarity. We suggest that most contaminations are taken up during collection of fetal material rather than originating from an in utero infection. In conclusion, a rigorous microbiological control by culture and PCR is a prerequisite for safe clinical use of fetal tissue suspensions.

Staphylococcus haemolyticus as a potential producer of biosurfactants with antimicrobial, anti-adhesive and synergistic properties

Staphylococcus haemolyticus is an opportunistic human pathogen that usually gains entry into the host tissue in association with medical device contamination. Biofilm formation is a key factor for the establishment of this bacterium and its arrangement and dynamics can be influenced by the synthesis of biosurfactants. Biosurfactants are structurally diverse amphiphilic molecules with versatile biotechnological applications, but information on their production by staphylococci is still scarce. In this work, two Staph. haemolyticus strains, showing high potential for biosurfactant production - as observed by four complementary methods - were investigated. Biosurfactant extracts were produced and studied for their capacity to inhibit the growth and biofilm formation by other bacterial human pathogens. The biosurfactant produced by the one of the strains inhibited the growth of most bacteria tested and subinhibitory concentrations of the biosurfactant were able to decrease biofilm formation and showed synergistic effects with tetracycline. Because these results were also positive when the biosurfactants were tested against the producing strains, it is likely that biosurfactant production by Staph. haemolyticus may be an unexplored virulence factor, important for competition and biofilm formation by the bacterium, in addition to the biotechnological potential.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work is the first to show the production of biosurfactants by Staphylococcus haemolyticus strains. Extracts showed antimicrobial, anti-adhesive and synergistic properties against a variety of relevant human pathogens, including the producing strains. In addition to the biotechnological potential, biosurfactants produced by Staph. haemolyticus are potentially undescribed virulence determinants in their producing strains.

Multidrug-resistant Staphylococcus haemolyticus isolates from infected eyes and healthy conjunctivae in India

This study aimed to determine the presence of antibiotic resistance genes (ARGs), SCCmec elements and genetic relatedness among Staphylococcus haemolyticus isolated from patients with a variety of eye infections (n=11) and from healthy conjunctiva (n=7). Minimum inhibitory concentrations were determined for 14 antimicrobials according to BSAC guidelines. PCR was used to identify the presence of mecA, mecC, SCCmec type and ARGs. Sequencing was used to determine mutations in gyrA, gyrB, topoisomerase IVA and IVB genes. Genetic relatedness was determined by PFGE. Of the 18 isolates, 17 showed resistance to at least one antibiotic, but none showed resistance to vancomycin or rifampicin. Ten isolates were oxacillin-resistant and carried the mecA gene, eight of which belonged to SCCmec type V. The presence of non-mec SCC elements in two meticillin-susceptible isolates and untypeable SCC elements in meticillin-resistant isolates suggests the involvement of S. haemolyticus in the diversification of SCC elements. Sequence analysis revealed point mutations in gyrA (Ser-84→Leu) and topoisomerase IVA genes (Ser-80→Leu) in 13 isolates, and additional variation in the QRDR (Asp-84→Asn) of two isolates, showing good correlation between mutations in gyrA and topoisomerase IV genes and the level of resistance to fluoroquinolones. PFGE analysis showed distinct pulsotypes forming two major clusters, indicating the existence of diversity among isolates, irrespective of the source of isolation. This study suggests that S. haemolyticus isolates from infected eyes and healthy conjunctivae invariably carried ARGs and SCCmec elements and showed diversity in their genomic content, irrespective of the source of isolation.

Transfer of mupirocin resistance from Staphylococcus haemolyticus clinical strains to Staphylococcus aureus through conjugative and mobilizable plasmids

Coagulase-negative staphylococci are thought to act as reservoirs of antibiotic resistance genes that can be transferred to Staphylococcus aureus, thus hindering the combat of this bacterium. In this work, we analyzed the presence of plasmids conferring resistance to the antibiotic mupirocin-widely used to treat and prevent S. aureus infections in hospital environments-in nosocomial S. haemolyticus strains. About 12% of the 75 strains tested were resistant to mupirocin, and this phenotype was correlated with the presence of plasmids. These plasmids were shown to be diverse, being either conjugative or mobilizable, and capable of transferring mupirocin resistance to S. aureus Our findings reinforce that S. haemolyticus, historically and mistakenly considered as a less important pathogen, is a reservoir of resistance genes which can be transferred to other bacteria, such as S. aureus, emphasizing the necessity of more effective strategies to detect and combat this emergent opportunistic pathogen.