Typing of coagulase-negative staphylococci isolated from foreign body infections

The ica operon and biofilm production in coagulase-negative Staphylococci associated with carriage and disease in a neonatal intensive care unit

Coagulase-negative staphylococci (CoNS) are a major cause of sepsis in the neonatal intensive care unit (NICU). We evaluated the hypothesis that the ica operon and biofilm production are associated with CoNS disease in this setting. CoNS associated with bacteremia or blood culture contamination and from the skin of infants with CoNS bacteremia or healthy controls were obtained during a prospective case-control study on a busy NICU. A total of 180 strains were identified, of which 122 (68%) were Staphylococcus epidermidis and the remainder were S. capitis (n = 29), S. haemolyticus (n = 11), S. hominis (n = 9), S. warneri (n = 8), and S. auricularis (n = 1). The presence of the genes icaA, icaB, icaC, and icaD was determined by PCR, and biofilm production was examined using qualitative (Congo red agar [CRA]) and quantitative (microtiter plate) techniques. There were no significant differences in the presence of the ica operon or CRA positivity among the four groups of strains. However, quantitative biofilm production was significantly greater in strains isolated from either the blood or the skin of neonates with S. epidermidis bacteremia. We conclude that the quantity of biofilm produced may be associated with the ability to cause CoNS infection. This conclusion suggests that the regulation of biofilm expression may play a central role in the disease process.

Identification of Staphylococcus spp. by PCR-restriction fragment length polymorphism of gap gene

Oligonucleotide primers specific for the Staphylococcus aureus gap gene were previously designed to identify 12 Staphylococcus spp. by PCR. In the present study, AluI digestion of PCR-generated products rendered distinctive restriction fragment length polymorphism patterns that allowed 24 Staphylococcus spp. to be identified with high specificity.

The polyvalent staphylococcal phage phi 812: its host-range mutants and related phages

Ninety-five percent of 782 culture collection strains, as well as hospital strains of Staphylococcus aureus subsp. aureus of different provenance and 43% of 89 culture collection strains of different coagulase-negative species of the genus Staphylococcus, were found to be sensitive to the polyvalent phage phi 812 or to at least one of its host-range mutants or to the polyvalent phages SK311, phi 131, and U16. Thus sensitivity to the polyvalent staphylococcal phages seems to be one of the common features of S. aureus subsp. aureus strains. The adsorption kinetics and one-step growth characteristics of the phages phi 812 and SK311 were estimated. Restriction genomic maps of the phages phi 812 (146.5 kb) and SK311 (141.1 kb) were constructed by use of the restriction endonucleases AvaII, PstI, KpnI, SacI, SmaI, and XhoI. The host-range mutations of the phage phi 812 were localized on this map. Comparison of restriction patterns of the phages phi 812 and SK311 with those of the polyvalent phages U16 and phi 131 suggests that all these phages are closely related. Their genomes differ from each other mostly by some deletions, insertions (1-3 kb), or inversions. Evidence was given that the phage phi 812 together with SK311, phi 131, and U16 belongs in the phage species Twort, the description of which is substantially supplemented with the data on the phage phi 812 reported in this paper.

Outbreak of methicillin-resistant Staphylococcus aureus in a teaching hospital--epidemiological and microbiological surveillance

An outbreak of methicillin-resistant S. aureus (MRSA) in a large university teaching hospital occurred between December 1991 and May 1992, involving 7 different wards and more than 30 patients. Epidemiological typing was performed to control the epidemic and to identify the MRSA carriers. By a combination of various classical methods (antimicrobial susceptibility, phage typing) and molecular typing procedures (SDS-PAGE of extracellular proteins, plasmid DNA profile, restriction enzyme fragment pattern of chromosomal DNA), three different clones of MRSA could be discriminated. The epidemic clone A was recovered from 30 patients and from 3 staff members. By strict microbiological monitoring together with hygienic measures, the epidemic could be successfully controlled. It is concluded that a combination of phenotypic markers and DNA-based epidemiological markers is extremely useful in the microbiological surveillance of MRSA outbreaks.

Epidemiological markers of coagulase-negative staphylococci

Several different epidemiological typing methods have been used in studies of coagulase-negative staphylococci; these include biotyping, antibiotic susceptibility pattern analysis, serological typing, phage typing, slime production detection, protein profile analysis, immunoblot fingerprinting and DNA typing. The most frequently used tests are antibiotic susceptibility and extrachromosomal DNA banding patterns. Comparison of chromosomal DNA restriction patterns is facilitated when the fragments are separated by pulsed-field electrophoresis. Typing variations occur quite frequently even in isolates of demonstrated clinical significance. Caution should therefore be exercised in denying the clinical relevance of coagulase-negative staphylococci, even when successive isolates show distinct typing differences.

Phage pattern and antibiotic resistance pattern of coagulase-negative staphylococci obtained from immunocompromised patients

A total of 152 coagulase-negative staphylococcal strains were isolated from clinical samples of 14 patients hospitalized after bone-marrow transplantation in a specialized hospital ward in Hungary, during an 18-month period between 1987 and 1989. Two species, Staphylococcus epidermidis and Staphylococcus haemolyticus, predominated (each, 45%). Using Pulverer and co-workers' phage set for typing, 68% of the isolates were typable; 16 phage patterns were observed. A characteristic long pattern with phages Ph10/Ph13/Ph15/U4/U15/U16/U20/U33 /U46 appeared only in S. epidermidis, among 5 of 11 colonized patients (8.5% of all strains). Single lysis with phage Ph13 was observed in 7 of the 14 patients (49% of all strains), in species S. capitis, S. epidermidis, S. haemolyticus, S. hominis, and S. warneri. In S. haemolyticus, non-typable strains predominated (66%); this character occurred only in 2% among other species. The strains colonizing the immunocompromised patients differed from each other in phage pattern, antibiotic resistance pattern, and/or slime production. No hospital infection was suggested. On the other hand, high incidence of two well-definable phage patterns raises some relationship between phage receptors or some regulatory systems in phage multiplication and factors responsible for special colonization as common surface properties.

Analysis of the relationship between bacterial adherence and extracellular production of mannose, galactose, glucose and ribose in Staphylococcus epidermidis and Staphylococcus hominis

Gas-liquid chromatography-mass spectrometry was used to analyze the extracellular extracts of 108 coagulase-negative staphylococcal strains for the presence of mannose, galactose, glucose and ribose, in order to determine whether production of these four monosaccharides, regarded as potential staphylococcal slime components, was associated with the adherence capacity of the individuals strains. A total of 90 Staphylococcus epidermidis and 18 Staphylococcus hominis strains were studied. Using the quantitative spectrophotometric assay, 21 Staphylococcus epidermidis strains were classified as strongly adherent, 12 as moderately adherent, 11 as weakly adherent, and 46 as nonadherent. All 18 Staphylococcus hominis strains were nonadherent. Mannose, galactose, glucose and ribose were detected as the main monosaccharide components in the extracellular extracts of all strains examined. Moreover, the mean relative concentrations of these monosaccharides were essentially the same for the different adherence phenotypes within the species Staphylococcus epidermidis. These results showed that there was no causal connection between the adherence of coagulase-negative staphylococci and the extracellular production of any of the four monosaccharides analyzed.

Typing of multiple isolates of coagulase-negative staphylococci from blood cultures and cerebrospinal fluid in neonates and children: an approach to discriminate contaminants

From eight neonates and children suspicious for suffering from septicemia and/or meningitis, coagulase negative staphylococci (CNS) were isolated from multiple blood cultures and from cerebrospinal fluids originating from different punctures. S. epidermidis was the predominant species. By a further typing using plasmid-profiles and exoprotein patterns besides the resistance phenotype, contaminants could be discriminated from the isolates as the probable etiologic agent exhibiting unique reaction patterns. CNS isolated from cases of septicemia together with other bacterial pathogens or from cases of presumed but not confirmed septicemia revealed as different.

Morphology of Staphylococcus saprophyticus bacteriophages

The morphology of 6 bacteriophages isolated from Staphylococcus saprophyticus was studied by electron microscopy. Phages had isometric heads and non-contractile tails, thus belonging to the Siphoviridae family. They were subdivided into two morphological groups based on head diameter and tail length. Type I, represented by phages 1154A and 1405, and characterized by an unusually small capsid, may be a new species.

Immunochemical analysis of the extracellular slime substance of Staphylococcus epidermidis

To analyze immunochemically the extracellular slime substance of Staphylococcus epidermidis, rabbits were repeatedly immunized with the crude slime extract isolated from an adherent, slime-producing clinical Staphylococcus epidermidis strain. Immunoelectron microscopy demonstrated that the target antigens of the resulting antibodies were located in the extracellular slime-like layer of bacterial cells. When these target antigens were characterized by immunoblotting, a variety of antigens were detected, including many with molecular masses higher than 80 kilodaltons and also a predominant one with a molecular mass of 30 kilodaltons. No characteristic differences were observed between the tube adherence test positive and negative Staphylococcus epidermidis isolates. Although there was variation in the number and intensity of high molecular mass antigens, such variations did not correlate with the tube adherence test. Of the 110 Staphylococcus epidermidis isolates studied, 106 (96%) expressed the 30-kilodalton antigen. This component was found in no other Staphylococcus spp. examined in the study. The bacterial component was not only easily detached from bacterial cells but also water-soluble, characteristics implicating a slime-like nature. Further studies are needed to definitively establish the origin and nature of the 30-kilodalton Staphylococcus epidermidis-specific component, and determine its potential benefit as a diagnostic tool.

Phage-typing of coagulase-negative staphylococci. Factors influencing typability

Factors influencing the phage-typability of coagulase-negative Micrococcaceae have been studied in 2,778 clinical isolates comprising A) 209 consecutive isolates from one laboratory, B) 2,107 clinical strains submitted for phage-typing for epidemiological reasons, and C) 462 strains representing all isolates of presumed clinical significance found in two laboratories during one month. The reproducibility was acceptable at duplicate repeated typing of the same strains as well as by typing epidemiologically-related pairs of strains from the same patient. Strains of Staphylococcus haemolyticus were seldom typable, whereas strains of S. epidermidis and S. hominis had a higher typability. Methicillin-resistant strains and other multiple-resistant strains were rarely typable (11-13%). The typability was higher among susceptible strains (36%) and strains resistant to penicillin only (43-50%). The typability of strains of the same species and antibiotic-resistance pattern differed between hospitals compared and decreased markedly over the years for multiple-resistant S. epidermidis isolates.

A procedure for urease and protein extraction from staphylococci

Staphylococcal cell protein and urease can be solubilized after growth in Todd-Hewitt broth supplemented with 0.5% yeast extract by extraction for 18-24 h in phosphate buffer, pH 7.0. In general 20% (but up to 100%) of the urease present in the original cells could be solubilized. Less protein was solubilized. Species examined included coagulase-negative staphylococci, Staphylococcus intermedius and Staph. aureus. Extracts of Staph. epidermidis prepared by this procedure gave electrophoretic urease and protein patterns similar to those prepared by sonication. The procedure was simple and minimized handling of the cells.

New aspects in the pathogenesis and prevention of polymer-associated foreign-body infections caused by coagulase-negative staphylococci

The significance of polymer-associated infections caused by coagulase-negative staphylococci is discussed. The aspects of bacterial adhesion to polymeric materials as the first important pathogenetic step in the development of such infections are treated. The role of extracellular slime substance (ESS) produced by the bacteria in the pathogenesis is elucidated and newer results concerning the interference of ESS with host defense mechanisms and antibiotic therapy are presented. As an approach to the prevention of polymer-associated foreign-body infections, the modification of the polymeric materials is introduced. Results of recent studies to achieve antiadhesive materials by radiation modification of polymers as well as the development of antimicrobial surfaces by incorporating or bonding antibiotics to polymers are presented.