Epidemiological analysis of Staphylococcus aureus strains from nasal carriers in a teaching hospital

The present study was conducted to assess the epidemiological relation of Staphylococcus aureus isolates from nasal carriers of hospital staff. Nasal swabs were taken from each of 327 personnel. After culturing on blood agar for overnight, probable staphylococcal isolates were identified and subjected to tube coagulase test. After a two-week interval, second nasal swabs were taken from the subjects whose first cultures were positive for S. aureus. Nasal carriage was defined in 58 (17.7%) personnel with positive culture for both sampling time. Antibiogram typing and arbitrarily-primed polymerase chain reaction (AP-PCR) with M13 primer were used for typing of the strains. Antibiotyping distinguished seven types and three subtypes, and 85% of the isolates were clustered in one group. AP-PCR, in contrast, identified 12 distinct patterns with 13 variants. A specific profile was not found among the isolates obtained from the personnel in a particular clinic. These results indicate that antibiotyping has poor discrimination power and heterogeneity among the nasal S. aureus strains in the hospital personnel screened is high.     

Staphylococcus aureus at a maternity ward. II. Characterization of isolates by enterotoxigenicity and toxic shock syndrome toxin (TSST-1) production

Tests for enterotoxins A, B, C, D, E and TSST-1 production were carried out on 775 S. aureus strains isolated from various sources (50 mothers and neonates studied periodically, mothers and infants treated for various acute inflammatory conditions, members of hospital staff, environmental swabs) during the period 1981-1983 at a maternity ward chosen for a 3-year systematic study and on additional 97 isolates obtained in 1985 from another maternity ward. This had contributed to a better classification of strains within certain phage type groups. It was found that the distribution of S. aureus types in the particular sub-sets varied, depending on the source of isolates. At the maternity ward followed for 3 years there was a clear-cut trend towards the spread of phage-untypable isolates producing enterotoxin C whereas at ward examined for comparative purposes B enterotoxin producers of phage type 95 were predominant. The tests for enterotoxigenicity has also proved to be useful as the epidemiological marker characterizing the predominantly circulating S. aureus strain. It has been confirmed that the majority role in the spread of maternity-ward-staphylococci is played by the neonates and the factors of hospital environment.     

Isolation rate of enterotoxigenic staphylococci in patients with sepsis, pneumonia and burns

The occurrence of Staphylococcus aureus strains producing enterotoxins of types SEA and SEB, which isolated from patients of different profile and caused the infectious process accompanied by pronounced intoxication without vomiting and enteric disturbances, was determined by means of the indirect hemagglutination test. The collection included 28 strains isolated in sepsis, 38 strains isolated in pneumonia, 57 strains isolated from patients with burns and 23, from the hands and nasopharynx of the medical staff. Among the staphylococcal strains isolated in sepsis, 75.6% synthesized SEA and 5.4%, SEB. The occurrence of SEA- and SEB-positive strains isolated in pneumonia was, respectively, 42.1% and 2.6%. From patients with burns SEA-positive staphylococci were mainly isolated (92.9%). Only 3% of the cultures isolated in wound infections produced SEA. From the medical staff, 13.4% of SEA-positive strains and 17.3% of SEB-positive strains were isolated. The data obtained from this study indicate the expediency of the determination of the enterotoxigenic properties of S. aureus clinical isolates in medical institutions for prophylactic measures with a view to the prevention of the spread of pathogenic clones.     

A trial of the use of mupirocin in the nasal carriage of Staphylococcus aureus in medical personnel]

Many hospital-acquired purulent diseases and wound infections are due to multiresistant hospital strains of Staphylococcus aureus. The role of S. aureus nasal carriage in development of wound infections due to autoinfection is confirmed. Not only inpatients but also hospital staff can be highly colonized with coagulase positive staphylococci. The S. aureus persistence in hospital personnel results in distribution of the microorganisms in the environment. Therefore, detection of S. aureus carriers without signs of the infection among the hospital personnel and eradication of the pathogen make it possible to control outbreaks of S. aureus infection in hospitals. Clinical efficacy of nasal ointment of mupirocin in the treatment of S. aureus carriers among the intensive care personnel of the N. N.Blokhin Cancer Research Center was evaluated. S. aureus nasal carriage was diagnosed in 17 (26 per cent) out of 65 persons. All the isolates were susceptible to oxacillin. 5-7 days after discontinuation of the mupirocin nasal ointment use eradication of S. aureus was stated in 100 per cent of the cases. The effect was still observed in 94 per cent of the cases in 1 month, in 76 per cent of the cases in 5-6 months and in 60 per cent of the cases in 8-9 months. It is believed that mupirocin nasal ointment (Bactroban) is convenient to use, low toxic and highly active in the treatment of persons with S. aureus nasal carriage.     

Host-microbe interplay in persistent Staphylococcus aureus nasal carriage in HIV patients

It has been shown that persistent Staphylococcus aureus nasal carriage results in increased bacterial dispersal and a higher risk of infection compared to non-or-intermittent S. aureus carriage. Although many studies investigated S. aureus nasal carriage in HIV patients, none compared persistent carriage to non-persistent carriage nor were studies performed in the HAART era. We investigated the host-microbe interplay of persistent S. aureus nasal carriage in HIV-infected patients by studying host determinants of persistent carriage as well as the genetic structure of S. aureus strains isolated. We compared this genetic structure with the previously determined population structure of S. aureus isolates obtained from healthy individuals. Between February 2004 and June 2005 all HIV patients visiting the outpatient department of Erasmus MC (Rotterdam, The Netherlands) were asked to participate in this study. Participants were interviewed and screened for persistent S. aureus carriage using two semi-quantitative nasal swab cultures. For 443 patients two cultures were available, 131 (29.6%) were persistent carriers, which is significantly higher as compared to healthy individuals from the same geographic region (17.6%; P<0.0001). Male sex (odds ratio [OR], 2.22; 95% confidence interval [CI], 1.32-3.73), current smoking (OR, 0.58; 95% CI, 0.38-0.90), Pneumocystis jiroveci pneumonia (PCP) prophylaxis (OR, 0.39; 95% CI, 0.16-0.97) and antiretroviral therapy (OR, 0.61; 95% CI, 0.38-0.98) were independent determinants of persistent carriage. Only two strains were mecA positive (1.2%) and no PVL positive strains were detected. The population structure of S. aureus strains isolated from HIV patients appeared to be strongly overlapping with that of S. aureus isolates from healthy individuals.     

Serotyping of Dutch Staphylococcus aureus strains from carriage and infection

International epidemiological studies have shown that clinical isolates of Staphylococcus aureus are usually capsulated with either type 5 or 8 capsular polysaccharides (CPs). Because all noncapsulated strains were found to be cross-reactive with polysaccharide 336 (336PS) antibodies, the noncapsulated strains were denoted as type 336PS. The capsular types of 162 Dutch methicillin-susceptible S. aureus strains derived from individuals living in the Rotterdam area were determined. The serotype distribution was 28.4% serotype 5, 53.7% type 8, and 17.9% type 336PS. Serotyping was in agreement with genotyping by amplified fragment length polymorphism (AFLP) and multi locus sequence typing (MLST). Among 49 nasal carriage isolates from healthy children 24.5% belonged to serotype 5, 67.3% were type 8 and 8.2% were type 336PS. For 28 adult patients on chronic ambulatory peritoneal dialysis (CAPD) the serotype incidences among carriage isolates obtained from the nose, catheter exit-site, and abdominal skin were 45.1%, 41.2% and 13.7%, respectively. Among S. aureus strains deriving from blood cultures, the serotype incidences were 17.7% serotype 5, 53.2% type 8, and 29.0% type 336PS. Apparently, type 336PS strains are more prevalent (P=0.017) among bacteraemia isolates as compared with the nasal carriage isolates obtained from healthy children and CAPD patients. In conclusion, all Dutch S. aureus isolates belonged to types 5, 8, or 336PS, which is in agreement with data from other countries. Thus, addition of the 336PS conjugate to a type 5- and type 8-CP protein conjugate vaccine would significantly extend the vaccine coverage.     

Staphylococcus cohnii--resident of hospital environment: cell-surface features and resistance to antibiotics

Staphylococcus cohnii strains dominated in the environment of investigated hospitals. We isolated 420 strains of the species mainly from hospitals environments, but also from infants--Intensive Care Units patients, its medical staff and non-hospital environments. S. cohnii subspecies cohnii was seen to dominate (361 strains). Seventy seven percent of these strains expressed cell-surface hydrofobicity, most of them were slime producers (61%) and this feature was correlated with their methicillin resistance. Among S. cohnii ssp. cohnii strains isolated from ICU environment 90% were resistant to methicillin, 43% expressed high-level resistance to mupirocin and high percentages were resistant to many other antibiotics. These strains may constitute a dangerous reservoir of resistance genes in a hospital.     

Slime production by Staphylococci isolated from prosthesis-associated infections.

Clinical isolates of Staphylococcus epidermidis are frequently referred to produce a biofilm, known as slime, involved in adherence to medical devices and in resistance to host defences. A high frequency of slime producing Staphylococcus aureus strains was never reported, at least in the case of human isolates. In the present study the production of slime by clinical isolates of S. aureus and S. epidermidis from catheter associated infections and from post-surgical infections was studied by a sensitive method based on culturing the isolates on Congo red agar. The study demonstrates that in nosocomial surgical infections, considered separately from catheter-associated infections, S. aureus emerges as a more prevalent etiologic agent than S. epidermidis, with a proportion of slime producing strains markedly high.     

Incidence, antibiotic resistance and clonal relations of MRSA strains isolated from a Romanian university hospital

Our aim was to estimate the frequency and characteristics ofmethicillin-resistant Staphylococcus aureus (MRSA) strains occurring in a Romanian teaching hospital. We retrospectively studied isolates from infected or colonized patients treated at the intensive care and surgical units during January 2004-December 2005. The antibiotic susceptibility of MRSA strains and the presence of mecA gene were determined. Consecutively occurring strains isolated through a three-month period were typed using pulsed field gel electrophoresis. A total of 423 S. aureus strains were identified, methicillin-resistance was detected in 211 (49.9%) strains. Most of them were multiresistant. One of the MRSA genotypes identified by PFGE was commonly recovered from patients treated in the intensive care unit. According to our results, MRSA strains were frequently isolated pathogens in our hospital and there is an urgent need to enhance infection control efforts.     

Comparative study of apramycin-resistant microorganisms isolated from man and animals

Apramycin-modifying strains isolated from pigs with coli bacteriosis, from humans and hospital environment were studied comparatively. Production of enzymes modifying the aminoglycoside was estimated with the radioactive cofactor procedure. E. coli isolates from the animals were phenotypically resistant to apramycin and a number of other aminoglycosides. They produced acetyltransferase AAC(3)IV, phosphotransferase APH(3')(5"), APH(3") and other enzymes. Resistance of the strains to gentamicin was also conditioned by AAC(3)IV since these strains did not produce AAD(2") and AAC(6'). In the resistant strains of E. coli and their transconjugates there were detected plasmids with a relative molecular weight of 60-80 MD. Some of the belonged to the compatibility group I1, the others belonged to the compatibility group H1. Strains of S. marcescens, K. pneumoniae. K. oxytoca and S. aureus isolated from humans and hospital environment were sensitive to apramycin. Only isolates of P. aeruginosa were resistant to this antibiotic. However, all the isolates produced AAC(3)IV. Some of them additionally produced AAC(6'), an enzyme modifying amikacin, kanamycin and other antibiotics and not acetylating apramycin. Almost all the strains produced kanamycin- and streptomycin phosphotransferases. Possible coselection of strains resistant to apramycin and gentamicin using one of these aminoglycosides is discussed.     

The prevalence of the Staphylococcus aureus tst gene among community- and hospital-acquired strains and isolates from Wegener's Granulomatosis patients

To allow rapid identification of toxic shock syndrome toxin-1 (TSST-1)-producing Staphylococcus aureus strains, a real-time PCR assay for the detection of the tst gene, which encodes TSST-1, was developed. The assay was applied to S. aureus isolates from patients with Wegener's Granulomatosis (WG), as well as isolates that were classified as either community- (CA) or hospital-acquired (HA). No significant difference in the percentage of tst-positive strains was observed between isolates from WG patients and CA isolates (24% and 25%, respectively). In contrast, only 14% of the HA isolates were tst-positive (p<0.05). Investigation of the clonal relationship between tst-positive CA and HA strains could indicated the recent emergence of a virulent S. aureus clone in the community.     

Evaluation of Three Slide Agglutination Tests for Rapid Identification of Staphylococcus aureus

Three slide agglutination tests for identification of Staphylococcus aureus were compared. The agglutination tests used for evaluation were Staphaurex (Wellcome Diagnostics), Staphyslide-Test (BioMerieux), and ANI S. aureus TEST (Ani Biotech Oy). A total of 347 isolates were analyzed, including 288 strains of S. aureus, 49 of S. epidermis, 11 of S. intermedius, 12 strains of other staphylococci and 14 non-staphylococcal strains. One hundred of the S. aureus strains were isolates from cases of food poisoning, 129 from mastitis and 59 from other clinical cases. The sensitivities of the tests were also compared using diluted suspensions of S. aureus strains and with purified Protein A dilutions. The results showed that the sensitivities of the tests were 98.6 %, 97.9 % and 99.0 % for Staphaurex, Staphyslide-test and ANI S. aureus TEST, respectively. The specificities were 100 % for the Staphyslide test and 98.8 % for both the ANI S. aureus TEST and the Staphaurex test. The sensitivities measured with diluted S. aureus strain suspensions and Protein A solutions were equal with the Staphaurex and ANI S. aureus TEST. All the agglutination tests studied proved to be practical, easy to use and accurate for the rapid identification of S. aureus strains from culture isolates.     

医院工作人员鼻腔葡萄球菌带菌状况年度推移的调查报告

本文报道1989年从202名医院工作人员鼻腔分离葡萄球菌的带菌状况和药敏性检测结果。并将此结果同作者等于1985年对200名同类人员检测的结果相比较,作了年度推移的调查分析发现1989年度的总带菌率(76.6％)比1985年度(84.5％)略有下降,但其中的金黄色葡萄球菌带菌率却从1985年的7.5％上升为10.4％。从1989年和1985两个年度的调查中,均发现临床科室人员金葡菌带菌率高于其它辅助科室人员,说明医务人员带菌率与接触病人成正相关关系。分离菌株对12种抗菌药物的耐药性检测结果显示,1989年分离菌株对其中9种的敏感性下降,并且从耐药谱显示出对5种抗菌药物耐药的多重耐药菌株明显增多。另从金葡菌的耐药情况,也看出1989年的耐药率高于1985年菌株。还在1989年分离的金葡菌中出现25％的耐甲氧西林菌株。     

Phage types of Staphylococcus aureus isolated in Poland in 1999-2004

The aim of study was to determine how population of Staphylococcus aureus strains from hospital environment forms itself with respect to phage types and frequency of their occurrence recently. 1157 S. aureus isolated from various clinical materials between 1999 and 2004 have been investigated. The basic set of phages and the three additional ones were used for typing strains according to Blair and Williams method. The results proved that population of S. aureus strains isolated from hospital environment differentiates with respect to phage types, like in the past. Strains belonging to phage group II dominates among them, but a considerable increase in number of phage group III have been remarked lately. A differential value of an individual phages from basic set remains on their usual level for years.     

Sensitivity of Staphylococcus aureus strains isolated from the patients of the SP ZOZ Hospital in Nidzica to bacteriocidal agents

The aim of this study was to evaluate a frequency of isolation and antimicrobial susceptibility testing of Staphylococcus aureus strains isolated from clinical specimens obtained from patients hospitalized in different hospital wards (SP ZOZ) in Nidzica from 01. 09. 2000 to 31. 12. 2003. During over three years 716 Staphylococcus aureus strains were cultured out of 15517 clinical specimens supplied to the Bacteriological Laboratory of SP ZOZ in Nidzica. S. aureus strains were isolated from 4.6% of examined samples. Samples were collected from patients hospitalized in all wards (five wards). Analysis of susceptibility to antimicrobial agents of identified S. aureus strains was performed. Seventy strains (9.8%) were metihicillin-resistant (MRSA). One hundred twenty four strains (17.3%) revealed inducible resistance to macrolides, linkosamides and streptogramins B (MLS, mechanism). The greatest activity in vitro against clinical S. aureus strains showed glycopeptide antibiotic--vancomycin (100% of susceptible strains). Clinical S. aureus strains isolated from patients of hospital in Nidzica are in the majority susceptible to antibiotics/chemotherapeutics, except of penicillin. Percentage of methicillin-resistant strains (MRSA) is not high (<10). Nevertheless, constant monitoring of a drug susceptibility of nosocomial S. aureus strains is important, considering the necessity of control of current epidemiological and therapeutic situation.     

Rhesus macaques (Macaca mulatta) are natural hosts of specific Staphylococcus aureus lineages

Currently, there is no animal model known that mimics natural nasal colonization by Staphylococcus aureus in humans. We investigated whether rhesus macaques are natural nasal carriers of S. aureus. Nasal swabs were taken from 731 macaques. S. aureus isolates were typed by pulsed-field gel electrophoresis (PFGE), spa repeat sequencing and multi-locus sequence typing (MLST), and compared with human strains. Furthermore, the isolates were characterized by several PCRs. Thirty-nine percent of 731 macaques were positive for S. aureus. In general, the macaque S. aureus isolates differed from human strains as they formed separate PFGE clusters, 50% of the isolates were untypeable by agr genotyping, 17 new spa types were identified, which all belonged to new sequence types (STs). Furthermore, 66% of macaque isolates were negative for all superantigen genes. To determine S. aureus nasal colonization, three nasal swabs from 48 duo-housed macaques were taken during a 5 month period. In addition, sera were analyzed for immunoglobulin G and A levels directed against 40 staphylococcal proteins using a bead-based flow cytometry technique. Nineteen percent of the animals were negative for S. aureus, and 17% were three times positive. S. aureus strains were easily exchanged between macaques. The antibody response was less pronounced in macaques compared to humans, and nasal carrier status was not associated with differences in serum anti-staphylococcal antibody levels. In conclusion, rhesus macaques are natural hosts of S. aureus, carrying host-specific lineages. Our data indicate that rhesus macaques are useful as an autologous model for studying S. aureus nasal colonization and infection prevention.     

Capsular serotype of Staphylococcus aureus in the era of community-acquired MRSA

Capsular polysaccharide (CP) plays an important role in the pathogenicity and immunogenicity of Staphylococcus aureus, yet the common serotypes of S. aureus isolated from US pediatric patients have not been reported. We investigated capsular serotype as well as methicillin susceptibility, presence of Panton-Valentine leukocidin (PVL), and clonal relatedness of pediatric S. aureus isolates. Clinical isolates were tested for methicillin susceptibility, presence of mecA, lukS-PV and lukF-PV, cap5 and cap8 genes by PCR, and for capsular or surface polysaccharide expression (CP5, CP8, or 336 polysaccharide) by agglutination. Genetic relatedness was determined by pulsed-field gel electrophoresis. All S. aureus isolates encoded cap5 or cap8. Sixty-nine percent of 2004-2005 isolates were methicillin-susceptible (MSSA) and most expressed a detectable capsule. The majority of MRSA isolates (82%) were unencapsulated, exposing an expressed cell wall techoic acid antigen 336. Pulsed-field type USA300 were MRSA, PVL-positive, unencapsulated strains that were associated with deep skin infections and recurrent disease. Over half (58%) of all isolates from invasive pediatric dermatologic infections were USA300. All pediatric isolates contained either capsule type 5 or capsule type 8 genes, and roughly half of the S. aureus clinical disease isolates from our population were diverse MSSA-encapsulated strains. The majority of the remaining pediatric clinical disease isolates were unencapsulated serotype 336 strains of the PVL(+) USA300 community-associated-MRSA clone.     

Pulsed-field gel electrophoresis of genomic restriction fragments as a tool for the epidemiological analysis of Staphylococcus aureus and coagulase-negative staphylococci

Thirteen Staphylococcus aureus and S. epidermidis strains obtained from nose and hand of two employees and one patient of a medical ward as well as two S. hemolyticus strains were analysed according to their restriction fragment length patterns (RFLP) by pulsed-field gel electrophoresis (PFGE) using the restriction enzymes SmaI and SstII. Species identification of the isolates was performed by a system which includes 20 biochemical reactions. Furthermore, the antibiotic resistance patterns of the strains were determined. While several isolates exhibited identical antibiotic susceptibilities and biochemical profiles, differences in the RFLP were obtained. In three cases, S. epidermidis strains colonizing the skin showed an identical restriction profile as isolates from the mucous membranes of the same person. We concluded that the analysis of staphylococcal strains by PFGE is an important epidemiological tool with high discrimination power.     

<Emphasis Type="Italic">Staphylococcus cohnii</Emphasis> hemolysins — Isolation,purification and properties

A total 355 of Staphylococcus cohnii isolates from hospital environment, patients (newborns), medical staff and from non-hospital environment were tested for hemolytic activity. Ninety-one % of S. cohnii ssp. cohnii and 74.5 % S. cohnii ssp. urealyticus strains exhibited hemolysis synergistic to S. aureus ATCC 25923 strain. Crude preparations of hemolysins of both bacterial subspecies presented δ-hemolysin, but not α- and β-toxin activity. Highly pure hemolysins were obtained by semipreparative SDS-PAGE or by organic solvent extraction from the freeze-dried crude preparations. Native-PAGE and 2D-PAGE showed their high heterogeneity. Molar masses of single hemolysin units estimated by the Tris-Tricine-SDS-PAGE were calculated as 3.47 kDa for S. cohnii ssp. cohnii and 3.53 kDa for S. cohnii ssp. urealyticus.     

Clone of Staphylococcus aureus phage type 187 isolated from people

The aim of this study was to examine whether Staphylococcus aureus of phage type 187 are genetically homogenous with the use of digestion of chromosomal DNA with SmaI and separation of the DNA by pulsed-field gel electrophoresis (PFGE). Sixteen S. aureus phage type 187 were isolated from the hospital patients (12) and the healthy carriers (4) in twelve medical centres in Poland during 1991 and 2005. The PFGE typing proved that the phage type 187 isolates have the same PFGE type (except for one) and constitute one clone.