Biotyping coagulase-negative staphylococci

Recurrent Staphylococcus capitis Prosthetic Valve Endocarditis Presenting With ST-Segment Elevation Myocardial Infarction: A Case Report

We report a case of ST-elevation myocardial infarction (STEMI) due to septic emboli secondary to Staphylococcus capitis endocarditis in a 32-year-old male patient with a past medical history of infectious endocarditis requiring mechanical aortic, mitral and tricuspid valve replacement presented with sharp chest pain and shortness of breath. Electrocardiogram demonstrated an acute inferior STEMI.

Coronary angiography revealed occlusion of the terminal left anterior descending (LAD) artery associated with a large apical wrap-around segment exhibiting TIMI 0 flow. Primary angioplasty was not performed given the distal location of the embolus. Clinical suspicion for septic or thrombotic coronary artery embolism was high given the patient’s history of mechanical valve prosthesis and in the setting of sub-therapeutic INR. Transesophageal echocardiography revealed a new mobile echodensity on the mitral prosthesis consistent with vegetation. S. capitis was isolated from blood cultures, confirming the diagnosis of endocarditis.

S. capitis is a rare cause of prosthetic valve endocarditis and should remain in the differential of septic coronary artery embolism among patients with features of infectious endocarditis.

Infective endocarditis presenting initially with ileus complicated by dehiscence of annuloplasty ring

BACKGROUND

Infective endocarditis (IE) on an annuloplasty ring dehiscence is uncommon after mitral valve repair.

CASE PRESENTATION

A 53-year-old man underwent mitral annuloplasty with a 24-mm ring for posterior mitral valve prolapse. He underwent repeat valve repair for recurrent mitral valve regurgitation 4 years later. He was re-hospitalised complaining of vomiting, nausea, general fatigue and left abdominal pain 2 months later, and presented with low-grade fever, leukocytosis and an elevated blood concentration of C-reactive protein. An abdominal computed tomography scan showed multiple embolisms in the liver, kidney and spleen. Transoesophageal echocardiography revealed mitral annuloplasty ring dehiscence and vegetations consistent with IE. The infected annuloplasty ring and vegetations were surgically excised. Blood cultures grew coagulasenegative staphylococcus aureus, consistent with the excised mitral valve histology. The postoperative course was uneventful, without recurrence of IE.

CONCLUSIONS

Embolic ileus as initial manifestation of IE is rare and might confuse the diagnosis and delay its management. Gastrointestinal signs and symptoms may be the initial manifestations of systemic embolization from infective endocarditis. Transoesophageal echocardiography effectively identified the presence of vegetations and mitral annuloplasty ring dehiscence.

Prosthetic valve endocarditis caused by Staphylococcus capitis: report of 4 cases

Although Staphylococcus capitis is considered to be a rare causative organism for prosthetic valve endocarditis, we report 4 such cases that were encountered at our hospital over the past 2 years. Case 1 was a 79-year-old woman who underwent aortic valve replacement with a bioprosthetic valve and presented with fever 24 days later. Transesophageal echocardiography revealed an annular abscess in the aorto-mitral continuity and mild perivalvular regurgitation. We performed emergency surgery 5 days after the diagnosis of prosthetic valve endocarditis was made. Case 2 was a 79-year-old woman presenting with fever 40 days after aortic valve replacement with a bioprosthesis. Transesophageal echocardiography showed vegetation on the valve, and she underwent urgent surgery 2 days after prosthetic valve endocarditis was diagnosed. In case 3, a 76-year-old man presented with fever 53 days after aortic valve replacement with a bioprosthesis. Vegetation on the prosthetic leaflet could be seen by transesophageal echocardiography. He underwent emergency surgery 2 days after the diagnosis of prosthetic valve endocarditis was made. Case 4 was a 68-year-old woman who collapsed at her home 106 days after aortic and mitral valve replacement with bioprosthetic valves. Percutaneous cardiopulmonary support was started immediately after massive mitral regurgitation due to prosthetic valve detachment was revealed by transesophageal echocardiography. She was transferred to our hospital by helicopter and received surgery immediately on arrival. In all cases, we re-implanted another bioprosthesis after removal of the infected valve and annular debridement. All patients recovered without severe complications after 2 months of antibiotic treatment, and none experienced re-infection during 163 to 630 days of observation. Since the time interval between diagnosis of prosthetic valve endocarditis and valve re-replacement ranged from 0 to 5 days, early surgical removal of the infected prosthesis and an appropriate course of antibiotics were attributed to good clinical outcomes in our cases.

Genotypic and phenotypic properties of coagulase-negative staphylococci causing dialysis catheter-related sepsis

Sixty coagulase-negative staphylococcus (CNS) isolates were recovered from the blood cultures or peritoneal dialysate effluent of 43 patients on renal dialysis. The patients had either renal dialysis catheter-related sepsis (CRS) or continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis. Isolates were characterized by biotyping, and genotyped by pulsed-field gel electrophoresis (PFGE). Phenotypic properties of the strains were also investigated. Several genotypes were identified with no one specific strain of CNS being associated with CRS. However, closely related strains were isolated from several patients within the units studied, suggesting horizontal transfer of micro-organisms. Genotypic macro-restriction profiles did not concur with phenotypic profiles or biotypes, confirming that genotyping is required for epidemiological studies. All staphylococcal strains were investigated for the production of phenotypic characteristics. Significant differences were predominantly seen in the production of lipase, esterase and elastase in strains isolated from the renal patients with CRS and CAPD-associated peritonitis, compared with a non-septic control group. These phenotypic characteristics may therefore have a role in the maintenance of CRS in renal patients.

Molecular characterization of methicillin-resistant coagulase-negative staphylococci from a neonatal intensive care unit

OBJECTIVE

To evaluate clonal dissemination of methicillin-resistant coagulase-negative staphylococci (CNS).

SETTING

Neonatal intensive care unit of a 180-bed, university-affiliated general hospital.

PATIENTS

Neonates admitted to the neonatal intensive care unit between March 1999 and October 2000, from whom CNS were isolated as a unique pathogen. Patients from other wards from whom epidemiologically unrelated staphylococci strains were obtained served as control-patients.

METHODS

Conventional methods were used for phenotypic characterization of CNS. Methicillin resistance was determined by mecA polymerase chain reaction (PCR) amplification. Genotypic characterization was done by random amplification of DNA with degenerated primers (RAPD) and repetitive element sequence-based PCR (rep-PCR).

RESULTS

Forty methicillin-resistant CNS isolates obtained from neonates were characterized as Staphylococcus epidermidis (33), S. hominis (5), S. warneri (1), and S. auricularis (1). Both RAPD and rep-PCR indicated the presence of 4 different clones among the 33 S. epidermidis isolates. In turn, the 4 randomly selected, epidemiologically unrelated methicillin-resistant CNS strains obtained from control-patients showed 3 new profiles by RAPD and 2 by rep-PCR, which differed from the corresponding patterns mentioned earlier. Persistence of S. hominis in a neonate could be assessed by both genotypic techniques.

CONCLUSIONS

The molecular characterization of the methicillin-resistant CNS studied indicated dissemination of one particular methicillin-resistant CNS clone among the neonates in the ward studied. Although RAPD showed a superior power to discriminate among methicillin-resistant CNS isolates, both RAPD and rep-PCR detected intraspecific and interspecific genomic diversity.

Performance of phenotypic and genotypic methods to determine the clinical relevance of serial blood isolates of staphylococcus epidermidis in patients with septicemia

Five typing methods, including biotyping (API ID32; BioMérieux, Marcy l'Etoile, France), quantitative antibiogram typing based on actual zone sizes, plasmid typing, randomly amplified polymorphic DNA (RAPD) analysis (with primer M13 and primer set ERIC-2-1026), and pulsed-field gel electrophoresis (PFGE), were compared with a previously performed method of DNA fingerprinting by AFLP (amplified fragment length polymorphism analysis) for their performance in the typing of blood isolates of Staphylococcus epidermidis. Sixteen epidemiologically unrelated strains and 11 sets of four blood culture isolates from 11 patients with septicemia were used. The stabilities and reproducibilities of the patterns, the discriminatory capacities of the methods, and the ability to apply the methods to blood culture isolates were used as performance criteria. All strains tested were typeable by each method, and the patterns were stable and reproducible. The numbers of different types within the collection of 16 epidemiologically different isolates were 5 by biotyping, 14 by antibiogram typing, 4 by plasmid typing, 9 by the RAPD assay (combination of results with primer M13 and primer set ERIC-2-1026), and 16 by PFGE. Within the 11 sets of four blood culture isolates the types found by quantitative antibiogram typing, plasmid typing, and PFGE were unique for each set, whereas by biotyping and RAPD analysis some types were observed in more than one set. The results of biotyping did not correspond with the results of the other methods or the results of AFLP. For 6 of the 11 sets, the results of all methods except those of biotyping corresponded completely. Quantitative antibiogram typing, PFGE, and AFLP proved to be the most accurate of the six typing methods tested.

The genomic diversity of coagulase-negative staphylococci associated with nosocomial infections

A total of 117 isolates of coagulase-negative staphylococci (CNS) were collected from patients in three medical centres. They were genotyped by pulsed-field gel electrophoresis (PFGE) following digestion with restriction enzymes SmaI and SstII. The isolates included Staphylococcus epidermidis, S. simulans, S. hominis, S. lugdunensis, S. capitis, S. saprophyticus, S. caprae and S. sciuri. They were collected at random from 82 patients and were associated with infected central venous lines, continuous ambulatory peritoneal dialysis (CAPD) catheters, endocarditis, osteomyelitis of prosthetic hips and internally fixed fractures. The genetic heterogeneity of the strains was demonstrated by PFGE profiles and two dendrograms. Though the strains were segregated into species, there was no clustering of the strains by type of infection, associated medical unit or geographical location of the patient. Numerous genotypes were identified, suggesting that no specific strains of CNS are associated with prosthetic related infection.

Subspecies discrimination of staphylococci from revision arthroplasties by ribotyping

Sixty-six cultures of Staphylococcus spp. were obtained from bone and tissue samples collected from 37 patients during revision arthroplasties and were speciated and ribotyped to assess strain diversity in each species. There were 10 ribotypes among 51 isolates of S. epidermidis, three among three isolates of S. capitis, two among four isolates of S. aureus and two among two isolates of S. simulans. One ribotype was found among each of: two isolates of S. warneri; two isolates of S. haemolyticus and single isolates of S. cohnii and S. saprophyticus. Low molecular weight bands of ribotype patterns characterized one or two related species whereas high molecular weight bands were useful for distinguishing types within species. Specimens from 17 patients yielded more than one isolate of Staphylococcus spp. In 13 of these patients the isolates were representatives of a single species but in only eight did ribotyping show the isolates to be identical. The findings of multiple species and ribotypes from samples taken from the same patient may have implications for understanding the nature of infection in revision arthroplasty and for antibiotic therapy.

Evaluation of Staph ID 32 system and Staph-Zym system for identification of coagulase-negative staphylococci

The purpose of the investigation was to evaluate two commercially available identification systems: a new modification of the Staph-Zym system (Rosco, Tåstrup, Denmark) and the Staph ID 32 API system (API System, BioMérieux, Paris, France). A local standard method to be used in routine laboratories was also evaluated. A total of 200 staphylococcal isolates, including strains from both the American Type Culture Collection and the Czechoslovak Collection of Microorganisms as well as 89 clinical isolates, were used in tests of all three identification systems. The Staph ID 32 API system identified from 50 to 100% of the reference strains and 82.1% of the clinical isolates correctly. The Staph-Zym system identified from 90 to 100% of the reference strains and 82.1% of the clinical isolates correctly. Most misidentifications were of minor importance, but in both systems major failures appeared (Staphylococcus aureus was identified as a coagulase-negative staphylococcus). Both systems needed backup from a reference laboratory to determine if two isolates were of the same strain.

Typing of Staphylococcus epidermidis strains by random amplification of polymorphic DNA

The polymerase chain reaction was used to obtain randomly amplified polymorphic DNA profiles for typing of Staphylococcus epidermidis strains. Epidemiologically unrelated S. epidermidis isolates were screened with randomly amplified polymorphic DNA analysis. The discriminating ability of 45 randomly designed 10-mer primers was assessed. The highest discriminatory power was obtained with the 10-mer oligonucleotide OPAM-12. In typing a total of 13 unrelated S. epidermidis strains with OPAM-12, 11 different banding profiles were obtained reproducibly by agarose gel electrophoresis. The discriminatory power of the method with OPAM-12 was estimated using the D value of Hunter and Gaston (1988) to be 0.961. A reproducibility index of 1 was obtained after typing a total of 40 cultures including 12 triplicates and one quadruplicate of the 13 unrelated strains. Following the described procedure, the randomly amplified polymorphic DNA method provided a rapid, simple and reproducible alternative to other S. epidermidis typing systems.

Study of Stomatococcus mucilaginosus isolated in a hospital ward using phenotypic characterization

Thirty-one isolates of Stomatococcus mucilaginosus were cultured from the blood (n = 6), throat (n = 23) and sputum (n = 2) of 18 hospitalized patients, 13 of whom were neutropaneic and five of whom were non-neutropaneic. Antibiotic susceptibility testing, performed by means of a broth microdilution method, showed that the minimal inhibitory concentrations (MICs) of ciprofloxacin were > or = 4 mg/l for the isolates collected from neutropaenic patients. All these patients received ciprofloxacin as part of their prophylactic regimen. In contrast, the MICs for four of five isolates collected from non-neutropaenic patients, none of whom were receiving ciprofloxacin, were < or = 2 mg/l. In addition, 14 of the 31 isolates were cultured from seven neutropaenic patients, admitted to the same ward over a 12-week period. To evaluate possible cross-acquisition of strains between patients, cluster analysis of all 31 isolates was performed using phenotypic characteristics, MIC values and acid production from carbohydrates (API 50 CH). Overall, 22 isolate clusters were distinguished. In five of 18 patients, two or more isolates were cultured which belonged to different clusters. In only one patient, identical isolates were cultured from blood and from the throat. All six isolates of cluster 7 were cultured within the aforementioned 12-week period from three neutropaenic patients. These data support the possibility of cross-acquisition of strains between patients although its frequency seems to be low.

Comparison of traditional and molecular methods of typing isolates of Staphylococcus aureus

Fifty-nine Staphylococcus aureus isolates and 1 isolate of Staphylococcus intermedius were typed by investigators at eight institutions by using either antibiograms, bacteriophage typing, biotyping, immunoblotting, insertion sequence typing with IS257/431, multilocus enzyme electrophoresis, restriction analysis of plasmid DNA, pulsed-field or field inversion gel electrophoresis, restriction analysis of PCR-amplified coagulase gene sequences, restriction fragment length polymorphism typing by using four staphylococcal genes as probes, or ribotyping. Isolates from four well-characterized outbreaks (n = 29) and a collection of organisms from two nursing homes were mixed with epidemiologically unrelated stock strains from the Centers for Disease Control and Prevention. Several isolates were included multiple times either within or between the sets of isolates to analyze the reproducibilities of the typing systems. Overall, the DNA-based techniques and immunoblotting were most effective in grouping outbreak-related strains, recognizing 27 to 29 of the 29 outbreak-related strains; however, they also tended to include 3 to 8 epidemiologically unrelated isolates in the same strain type. Restriction fragment length polymorphism methods with mec gene-associated loci were less useful than other techniques for typing oxacillin-susceptible isolates. Phage typing, plasmid DNA restriction analysis, and antibiogram analysis, the techniques most readily available to clinical laboratories, identified 23 to 26 of 29 outbreak-related isolates and assigned 0 to 6 unrelated isolates to outbreak strain types. No single technique was clearly superior to the others; however, biotyping, because it produced so many subtypes, did not effectively group outbreak-related strains of S. aureus.

Update on clinical significance of coagulase-negative staphylococci

The clinical significance of coagulase-negative Staphylococcus species (CNS) continues to increase as strategies in medical practice lead to more invasive procedures. Hospitalized patients that are immunocompromised and/or suffering from chronic diseases are the most vulnerable to infection. Since CNS are widespread on the human body and are capable of producing very large populations, distinguishing the etiologic agent(s) from contaminating flora is a serious challenge. For this reason, culture identification should proceed to the species and strain levels. A much stronger case can be made for the identification of a CNS etiologic agent if the same strain is repeatedly isolated from a series of specimens as opposed to the isolation of different strains of one or more species. Strain identity initially can be based on colony morphology, and then one or more molecular approaches can be used to gain information on the genotype. Many of the CNS species are commonly resistant to antibiotics that are being indicated for staphylococcal infections, with the exception of vancomycin. The widespread use of antibiotics in hospitals has provided a reservoir of antibiotic-resistant genes. The main focus on mechanisms of pathogenesis has been with foreign body infections and the role of specific adhesins and slime produced by Staphylococcus epidermidis. Slime can reduce the immune response and opsonophagocytosis, thereby interfering with host defense mechanisms. As we become more aware of the various strategies used by CNS, we will be in a better position to compromise their defense mechanisms and improve treatment.

Rapid method for epidemiological evaluation of gram-positive cocci by field inversion gel electrophoresis

We report a rapid method for the isolation of intact chromosomal DNA from gram-positive cocci that is suitable for in situ restriction endonuclease digestion in agarose blocks. When combined with a rapid field inversion gel electrophoresis protocol, this approach allows the preparation and electrophoretic analysis of chromosomal restriction fragments produced by rare-cutting enzymes in a total time period of 2 days from start to finish. The utility of the method is demonstrated in the epidemiological evaluation of Staphylococcus epidermidis clusters from two hospitals as well as of additional representative staphylococci and enterococci.

Failure of phenotypic characteristics to distinguish between carrier and invasive isolates of Staphylococcus epidermidis

Thirty carrier and 29 invasive Staphylococcus epidermidis isolates were analysed for production of slime, extracellular enzymes and antibiotic resistance. Evaluation of slime production was by two methods which gave differing results, but both showed no difference between the two groups of isolates. Exoenzyme production by the two groups of isolates was also similar, and the only differences were shown in resistance to some antibiotics; carrier isolates were more resistant to novobiocin and cephalothin, but resistance to chloramphenicol, tunicamycin, teicoplanin, penicillin, ampicillin and tetracycline was similar in both groups. Cluster analysis based on exoenzyme production showed no consistent difference between invasive and carrier isolates, with the lowest similarity coefficient over 88% (except for one isolate). Consequently, none of the characteristics studied was useful in differentiating potentially invasive isolates.

The use of biotyping and DNA fingerprinting in typing Candida albicans from hospitalized patients

The application of typing procedures for the purpose of strain differentiation among isolates of Candida albicans obtained from hospitalized patients has been limited. We have applied biotyping and DNA restriction fragment analysis (DNA fingerprinting) by using EcoRI to the study of C. albicans isolates obtained from hospitalized patients. A total of 68 isolates from 15 patients were studied. Thirteen subtypes were identified by biotyping, 8 by DNA fingerprinting, and 21 by a combination of the biotyping and DNA fingerprinting approaches (composite subtype). Both techniques were highly reproducible. In examining the strain variation among isolates obtained from multiple anatomic sites over time, we found that similar, if not identical, strains were recovered from the oropharynx, urine, stool, and blood in a given patient, and these strains persisted. Only rarely did two patients share the same composite subtype suggesting sporadic nosocomial transmission. The combination of biotyping and DNA fingerprinting improved strain discrimination compared to either method alone. Further investigation with these and other epidemiologic typing methods will be necessary to enhance the understanding of the epidemiology and pathogenesis of candidiasis in hospitalized patients.

Hemolysins and other characteristics that help differentiate and biotype Staphylococcus lugdunensis and Staphylococcus schleiferi

Reference strains and clinical isolates representing the newly defined species Staphylococcus lugdunensis and Staphylococcus schleiferi were examined with the battery of tests previously recommended (G.A. Hébert, C.G. Crowder, G.A. Hancock, W.R. Jarvis, and C. Thornsberry, J. Clin. Microbiol. 26:1939-1949, 1988) for other species of coagulase-negative staphylococci (CNS). The Staph-Ident system (Analytab Products, Plainview, N.Y.) supplemented with tests for synergistic hemolysis, adherence to glass, pyroglutamyl-beta-naphthylamide hydrolysis, and susceptibility to a set of five antimicrobial disks differentiated each of these species from other species of CNS and separated strains within each species into several biotypes. Most strains (95%) of S. lugdunensis produced a delta hemolysin like that seen with nine other species of CNS. Most strains (91%) of S. schleiferi produced a beta hemolysin, which is a unique characteristic among CNS. Most (95%) of the S. schleiferi but very few (12%) of the S. lugdunensis were adherence positive. Both hemolysins and adherins are potential virulence factors among CNS. Some (29%) of the S. lugdunensis were beta-lactamase positive. The S. lugdunensis were resistant to polymyxin B and bacitracin (10 U), but the S. schleiferi were susceptible to both disks. Clinical isolates of S. lugdunensis were aligned in 18 biotypes because of eight biochemical profiles and eight physiologic subtypes; isolates of S. schleiferi were in 8 biotypes because of three biochemical profiles and subtypes. These tools for correctly identifying and then biotyping two more clinical species of CNS should enhance both epidemiologic and ecologic investigations.

Biotyping of coagulase-negative staphylococci. 108 isolates from nosocomial bloodstream infections

Using simple, readily available typing methods, we evaluated 108 strains of coagulase-negative staphylococci that were causally related to bloodstream infections: 95% (103 of 108) of the isolates were identified as Staphylococcus epidermidis and were divided into 18 biotypes by API Staph-Trac. A single biotype (biotype A, 6606113) accounted for greater than 50% of the isolates of S. epidermidis. Biotype A was further divided into seven subtypes by slime production and synergistic hemolysis; however, 66% of the isolates in biotype A remained in two major subtypes, 1a (strongly slime-positive and synergistic hemolysis-positive) and 2a (strongly slime-positive and synergistic hemolysis-negative). The addition of the antibiotype further separated the isolates into individual strains or into small groups of organisms. A significant correlation was noted between synergistic hemolysis and the three most resistant antibiotypes (p = 4.2 X 10(-5); OR = 5.8; CI95, 2.2-15.2). Each biotype, subtype, and antibiotype was further divided into multiple unique strains by plasmid pattern analysis. In most clinical situations the combination of API Staph-Trac, antibiotic profile, slime production, and synergistic hemolysis provides adequate strain discrimination. Plasmid pattern analysis adds important information in specific clinical situations and may be invaluable for epidemiologic investigations.

Characteristics of coagulase-negative staphylococci that help differentiate these species and other members of the family Micrococcaceae

One hundred reference strains and 1,240 clinical isolates representing 26 species of the family Micrococcaceae were used to evaluate the potential of tests for synergistic hemolysis, adherence to glass, pyroglutamyl-beta-naphthylamide hydrolysis, and susceptibility to a set of five antimicrobial agents for differentiating these species and strains within the species. Sixty-eight percent of the clinical isolates exhibited synergistic hemolysis; 69% of the clinical staphylococci but none of the micrococci or stomatococci were adherence positive, and 92% of the strong positive adherence reactions were produced by strains of Staphylococcus epidermidis. Strains from 15 of the species were pyroglutamyl-beta-naphthylamide positive, but this test separated Staphylococcus xylosus from other novobiocin-resistant staphylococci and Staphylococcus intermedius from other coagulase-positive species. A polymyxin B disk helped differentiate S. epidermidis from most other coagulase-negative staphylococci, and a bacitracin disk (10 U) helped differentiate Staphylococcus haemolyticus from most other novobiocin-susceptible staphylococci. All strains that were susceptible to furazolidone and resistant to Taxo A disks (bacitracin, 0.04 U; BBL Microbiology Systems, Cockeysville, Md.) were staphylococci. We observed a 91% correlation between species identification obtained with the Staph-Ident system (Analytab Products, Plainview, N.Y.) and conventional methods; but the micrococci and stomatococci were incorrectly identified as staphylococci with Staph-Ident, and several isolates of S. epidermidis were misidentified as Staphylococcus hominis because they were alkaline phosphatase negative. Both these problems can be prevented by adding the simple tests we describe to those already recommended when the Staph-Ident system is used to identify isolates of gram-positive, catalase-positive cocci.