Analysis of nosocomial Staphylococcus haemolyticus by MLST and MALDI-TOF mass spectrometry

Staphylococcus borealis - A newly identified pathogen of bovine mammary glands

Twelve Staphylococcus borealis strains, isolated in Canada and Poland from milk of cows with intramammary infections, were characterized phenotypically (biochemical reactions on ID 32 STAPH and Biolog Phenotype MicroArrays™ PM1 and PM2A, ability of biofilm production) and genotypically (random amplified polymorphic DNA). In addition, a genomic comparison was done with S. borealis strains of human and porcine origin using the multilocus sequence typing (MLST) technique. The bovine isolates showed a high degree of phenotypic and genotypic diversity, however, they could be differentiated from human strains by the negative test for urease (found in all but one bovine isolate examined with ID 32 STAPH) and positive reaction for D-galactose (on Biolog phenotype microarray PM1) and D-lactose (on both commercial systems). The MLST method, utilizing six concatenated genes of the total length of ∼2930 bp, revealed that bovine strains (irrespective of the country of origin) show a distinctly greater degree of mutual relationship than to the strains of human and porcine origin, suggesting that S. borealis has evolved independently in these hosts. In conclusion, bovine-specific S. borealis can be involved in intramammary infections in cattle.

Comparison of non-aureus staphylococcal and mammaliicoccal species found in both composite milk and bulk-tank milk samples of dairy cows collected in tandem

Non-aureus staphylococci and the closely related mammaliicoccal species (NASM) are the most common causes of bovine subclinical mastitis on modern dairy farms and are highly prevalent in bulk-tank milk. The purpose of this study was to determine the distribution of NASM in both composite cow milk (CCM) and bulk-tank milk (BTM) samples collected in tandem in commercial Flemish dairy herds and to estimate the origin of the different (subgroups of) NASM species present in BTM by applying strain typing (random amplification of polymorphic DNA or random amplified DNA [RAPD]). A single cross-sectional sampling was performed over 5 herds that volunteered to participate in the study. Composite cow milk samples (n = 356) were collected from all lactating cows (except those with clinical mastitis) during a milking in tandem with 6 BTM samples per herd sequentially collected immediately post that milking (n = 30). In total, 421 and 80 NASM isolates were recovered and identified by MALDI-TOF mass spectrometry from the CCM and BTM samples, respectively and a total of 21 and 12 different NASM species were identified from CCM and BTM samples, respectively. Staphylococcus cohnii was the most prevalent NASM species found in BTM followed by Staphylococcus haemolyticus, Staphylococcus epidermidis, Mammaliicoccus lentus, and Staphylococcus equorum, whereas from CCM samples the most common species were S. hemolyticus, S. cohnii, S. equorum, S. epidermidis, and Staphylococcus chromogenes. The prevalent NASM species in both CCM and BTM samples was distinct for each herd, corroborating other studies observing a herd-specific NASM microbiota. Random amplified DNA analysis was performed on 9 NASM species (S. chromogenes, S. epidermidis, S. haemolyticus, S. equorum, Mammaliicoccus sciuri, Staphylococcus xylosus, S. cohnii, Staphylococcus debuckii, and M. lentus) because these species were isolated from both sample types in a herd. The same RAPD types were found in both sample types for all NASM species selected for strain typing in varying degrees. When assessing the distribution of NASM species, differences within NASM species should be examined meaning a closer look should be taken at the strain level rather than at the species level only.

Isolation and Characterization of the First Zobellviridae Family Bacteriophage Infecting Klebsiella pneumoniae

In order to address the upcoming crisis in the treatment of Klebsiella pneumoniae infections, caused by an increasing proportion of resistant isolates, new approaches to antimicrobial therapy must be developed. One approach would be to use (bacterio)phages and/or phage derivatives for therapy. In this study, we present a description of the first K. pneumoniae phage from the Zobellviridae family. The vB_KpnP_Klyazma podovirus, which forms translucent halos around the plaques, was isolated from river water. The phage genome is composed of 82 open reading frames, which are divided into two clusters located on opposite strands. Phylogenetic analysis revealed that the phage belongs to the Zobellviridae family, although its identity with the closest member of this family was not higher than 5%. The bacteriophage demonstrated lytic activity against all (n = 11) K. pneumoniae strains with the KL20 capsule type, but only the host strain was lysed effectively. The receptor-binding protein of the phage was identified as a polysaccharide depolymerase with a pectate lyase domain. The recombinant depolymerase protein showed concentration-dependent activity against all strains with the KL20 capsule type. The ability of a recombinant depolymerase to cleave bacterial capsular polysaccharides regardless of a phage's ability to successfully infect a particular strain holds promise for the possibility of using depolymerases in antimicrobial therapy, even though they only make bacteria sensitive to environmental factors, rather than killing them directly.

Characterization of New Staphylococcus haemolyticus ST42 Populations in Northern Taiwan

Introduction: Staphylococcus haemolyticus is an acquired opportunistic pathogen causing nosocomial infections. Our previous studies of S. haemolyticus showed a group of isolates that produced a significantly higher disease severity than the others. Further molecular typing showed that the sequence type (ST) 42 was the major clone among the isolates. The main aim of this study was to characterize ST42. Materials and Methods: Sixty-one and 36 isolates were collected from burn and nonburn patients, respectively. Molecular typing, antibiotic susceptibility assays, and phenotypic characterizations were performed. Results: Thirteen STs, including seven new STs, were established (ST42 to ST48). ST42 was prevalent in burn and nonburn patients, and all the pulsotype C isolates were ST42. Four of the novel STs originated from ST3, suggesting that these clonal lineages evolved locally. ST3 and ST42 showed a significant difference in clindamycin susceptibility; molecular typing showed only one MLST locus variation among seven loci in SH1431, which has been reportedly involved in the regulation of biofilm formation through Zn ²⁺ binding affinities. Conclusions: Seven novel S. haemolyticus STs were identified; phylogenetic analysis suggested the presence of locally evolved clonal lineages. The predominant ST42 showed weak biofilm formation abilities; other factors that cause the clonal lineage change still need further investigation.

Novel Klebsiella pneumoniae K23-Specific Bacteriophages From Different Families: Similarity of Depolymerases and Their Therapeutic Potential

Antibiotic resistance is a major public health concern in many countries worldwide. The rapid spread of multidrug-resistant (MDR) bacteria is the main driving force for the development of novel non-antibiotic antimicrobials as a therapeutic alternative. Here, we isolated and characterized three virulent bacteriophages that specifically infect and lyse MDR Klebsiella pneumoniae with K23 capsule type. The phages belonged to the Autographiviridae (vB_KpnP_Dlv622) and Myoviridae (vB_KpnM_Seu621, KpS8) families and contained highly similar receptor-binding proteins (RBPs) with polysaccharide depolymerase enzymatic activity. Based on phylogenetic analysis, a similar pattern was also noted for five other groups of depolymerases, specific against capsule types K1, K30/K69, K57, K63, and KN2. The resulting recombinant depolymerases Dep622 (phage vB_KpnP_Dlv622) and DepS8 (phage KpS8) demonstrated narrow specificity against K. pneumoniae with capsule type K23 and were able to protect Galleria mellonella larvae in a model infection with a K. pneumoniae multidrug-resistant strain. These findings expand our knowledge of the diversity of phage depolymerases and provide further evidence that bacteriophages and phage polysaccharide depolymerases represent a promising tool for antimicrobial therapy.

Contribution of Podoviridae and Myoviridae bacteriophages to the effectiveness of anti-staphylococcal therapeutic cocktails

Bacteriophage therapy is considered one of the most promising therapeutic approaches against multi-drug resistant bacterial infections. Infections caused by Staphylococcus aureus are very efficiently controlled with therapeutic bacteriophage cocktails, containing a number of individual phages infecting a majority of known pathogenic S. aureus strains. We assessed the contribution of individual bacteriophages comprising a therapeutic bacteriophage cocktail against S. aureus in order to optimize its composition. Two lytic bacteriophages vB_SauM-515A1 (Myoviridae) and vB_SauP-436A (Podoviridae) were isolated from the commercial therapeutic cocktail produced by Microgen (Russia). Host ranges of the phages were established on the panel of 75 S. aureus strains. Phage vB_SauM-515A1 lysed 85.3% and vB_SauP-436A lysed 68.0% of the strains, however, vB_SauP-436A was active against four strains resistant to vB_SauM-515A1, as well as to the therapeutic cocktail per se. Suboptimal results of the therapeutic cocktail application were due to extremely low vB_SauP-436A1 content in this composition. Optimization of the phage titers led to an increase in overall cocktail efficiency. Thus, one of the effective ways to optimize the phage cocktails design was demonstrated and realized by using bacteriophages of different families and lytic spectra.

Fecal non-aureus Staphylococci are a potential cause of bovine intramammary infection

The presence of non-aureus staphylococci (NAS) in bovine rectal feces has recently been described. Similar to other mastitis causing pathogens, shedding of NAS in the environment could result in intramammary infection. The objective of this study was to investigate whether NAS strains present in feces can cause intramammary infection, likely via teat apex colonization. During a cross-sectional study in 5 dairy herds, samples were collected from the habitats quarter milk, teat apices, and rectal feces from 25%, 10%, and 25% of the lactating cows, respectively, with a cow serving as the source of one type of sample only. Samples from clinical mastitis cases were continuously collected during the 1-year study period as well. The 6 most prevalent NAS species, Staphylococcus (S.) chromogenes, S. cohnii, S. devriesei, S. equorum, S. haemolyticus, and S. hominis, were further subtyped by random amplification of polymorphic deoxyribonucleic acid polymerase chain reaction (RAPD-PCR), when the same NAS species was present in the same herd in the three habitats. For S. chromogenes, S. cohnii, S. devriesei, and S. haemolyticus, the same RAPD type was found in rectal feces, teat apices, and quarter milk, indicating that fecal NAS can infect the mammary gland. For S. hominis and S. equorum, we were unable to confirm the presence of the same RAPD types in the three habitats.

Influence of antibiotics on biofilm formation by different clones of nosocomial Staphylococcus haemolyticus

Staphylococcus haemolyticus is the most common organism among clinical isolatesof methicillin-resistant staphylococci. Aim: This study evaluated the ability to produce biofilm with the presence of the antibiotics (1/4 minimum inhibitory concentrations) of S. haemolyticus strains isolated from blood culture. Methods: Clonal distribution was assessed in pulsed-field gel electrophoresis. PCR assays were performed to detect mecA, icaA, aap, atlE, atl, fbp genes. S. haemolyticus strains grown in the presence of the antibiotics were investigated for biofilm formation on glass, polystyrene and catheter surfaces. Results: Biofilm formation was independent of the presence of the icaA and mecA genes, pulsed-field gel electrophoresis type. Vancomycin, oxacillin, moxifloxacin, rifampicin, teicoplanin, tigecycline and linezolid did not inhibit biofilm formation on abiotic surfaces. Conclusion: This study demonstrated that the biofilm formation process is complex and may not be related to ica gene carriage. Furthermore, in this study the biofilm formation was increased in the presence of antimicrobial agents.

Genetic Relatedness of Staphylococcus haemolyticus in Gut and Skin of Preterm Neonates and Breast Milk of Their Mothers

BACKGROUND

Staphylococcus haemolyticus is a common colonizer and cause of late-onset sepsis (LOS) in preterm neonates. By describing genetic relatedness, we aimed to determine whether mother's breast milk (BM) is a source of S. haemolyticus colonizing neonatal gut and skin and/or causing LOS.

METHODS

S. haemolyticus was isolated from stool and skin swabs of 49 BM-fed preterm neonates admitted to neonatal intensive care unit, 20 healthy BM-fed term neonates and BM of mothers once a week and typed by multilocus variable number tandem repeat analysis and multilocus sequence typing. Virulence-related genes were determined by polymerase chain reaction.

RESULTS

Compared with term neonates, S. haemolyticus colonized more commonly gut (35% vs. 89.9%; P < 0.001) and skin (50% vs. 91.8%; P < 0.001) of preterm neonates and mothers' BM (15% vs. 38.8%). Isolates from preterm compared with term neonates and their mothers carried more commonly the mecA gene (83.5% vs. 5.4%; P < 0.001) and IS256 (52.4% vs. 2.7%; P < 0.001) and belonged to clonal complex 29 (89.1% vs. 63%; P = 0.014). Only 7 (14.3%) preterm and 3 (15%) term neonates were colonized in gut or on skin with multilocus variable number tandem repeat analysis types indistinguishable from those in BM. Most frequent multilocus variable number tandem repeat analysis types belonged to sequence type 3 or 42, comprised 71.1%-78.4% of isolates from preterm neonates/mothers and caused all 7 LOS episodes. LOS-causing strain colonized the gut of 4/7 and the skin of 5/7 neonates, but not BM, before onset of LOS.

CONCLUSIONS

S. haemolyticus colonizing gut and skin or causing LOS in preterm neonates rarely originate from BM but are mecA-positive strains adapted to hospital environment.

Clinical features, outcomes, and molecular characteristics of an outbreak of Staphylococcus haemolyticus infection, among a mass-burn casualty patient group, in a tertiary center in northern Taiwan

BACKGROUND/PURPOSE

We reported an outbreak of Staphylococcus haemolyticus (SH) infection in a group of young patients (mean age 21.6) simultaneously hospitalized due to a mass-burn incident. This study analyzed the clinical features of these patients and the microbiological characteristics of the outbreak.

METHODS

All 50 patients hospitalized for burns were enrolled, and their clinical differences were analyzed based on culture results. A drug sensitivity test and pulsed-field gel electrophoresis (PFGE) were conducted to analyze the microbiological difference between SH isolates from the mass-burn casualty patients (the study group) and SH isolates from other patients hospitalized during the same period (the control group) with the intention of identifying the strain of SH outbreak.

RESULTS

Patients with isolated SH (N = 36) had a significantly higher disease severity (higher revised Baux score, APACHE II score, and concurrent bacteremia rate), and a significantly poorer clinical outcome (longer ICU and hospital stay, and longer MV usage). Significant differences in the phenotype (antibiotics drug sensitivity test) and genotype (PFGE typing) were observed between the study and control groups. The dominant PFGE type C identified among the study group was related to poorer outcomes in a subgroup analysis.

CONCLUSION

A dominant PFGE type of SH infection was found in these mass-burn casualty patients. Pathogenesis or virulence factors may have contributed to our results. Further study of isolated SH should be conducted.

Coagulase-Negative Staphylococci in Human Milk From Mothers of Preterm Compared With Term Neonates

BACKGROUND

Human milk is the preferred nutrition for neonates and a source of bacteria. Research aim: The authors aimed to characterize the molecular epidemiology and genetic content of staphylococci in the human milk of mothers of preterm and term neonates.

METHODS

Staphylococci were isolated once per week in the 1st month postpartum from the human milk of mothers of 20 healthy term and 49 preterm neonates hospitalized in the neonatal intensive care unit. Multilocus variable-number tandem-repeats analysis and multilocus sequence typing were used. The presence of the mecA gene, icaA gene of the ica-operon, IS 256, and ACME genetic elements was determined by PCR.

RESULTS

The human milk of mothers of preterm compared with term neonates had higher counts of staphylococci but lower species diversity. The human milk of mothers of preterm compared with term neonates more often contained Staphylococcus epidermidis mecA (32.7% vs. 2.6%), icaA (18.8% vs. 6%), IS 256 (7.9% vs. 0.9%), and ACME (15.4% vs. 5.1%), as well as Staphylococcus haemolyticus mecA (90.5% vs. 10%) and IS 256 (61.9% vs. 10%). The overall distribution of multilocus variable-number tandem-repeats analysis (MLVA) types and sequence types was similar between the human milk of mothers of preterm and term neonates, but a few mecA-IS 256-positive MLVA types colonized only mothers of preterm neonates. Maternal hospitalization within 1 month postpartum and the use of an arterial catheter or antibacterial treatment in the neonate increased the odds of harboring mecA-positive staphylococci in human milk.

CONCLUSION

Limiting exposure of mothers of preterm neonates to the hospital could prevent human milk colonization with more pathogenic staphylococci.