Prevalence of icaA and icaD genes in Staphylococcus aureus and Staphylococcus epidermidis strains isolated from patients and hospital staff

Staphylococci are ubiquitous microorganisms that predominate in normal skin and mucosal flora. Staphylococcus aureus and Staphylococcus epidermidis have been identified as a major cause of nosocomial infections, especially in patients with predisposing factors such as indwelling or implanted foreign bodies. The ability of both S. epidermidis and S. aureus to produce biofilm was compared between 116 clinically significant strains (46 from blood cultures of patients with bloodstream infection and 70 isolated from catheters) and 60 strains isolated from nasal swabs of healthy carriers from hospital staff. The presence of the intercellular adhesion genes (icaA and icaD) was determined by the Polymerase Chain Reaction method, and slime production was examined using qualitative Congo red agar technique. Among clinical strains, 35.2% (19/54) of S. aureus and 48.4% (30/62) of S.epidermidis were both positive icaA and icaD and they produced slime. Among carrier strains, 22.2% (8/36) of S. aureus and 33.3% (8/24) of S. epidermidis were positive for slime synthesis and exhibited ica genes. Our results suggest that the virulence factors contributing to the development of infections can be present in patient and hospital staff isolates. Thus, we consider it is important to detect healthy carriers of slime-producing staphylococci and to control the dissemination of these microorganisms especially in a hospital.     

Colonization priority among Staphylococcus aureus strains--correlation with phage-type

We have studied the distribution of phage-type patterns among strains of Staphylococcus aureus isolated from patients in a burns unit. From 51 patients the same phage-type was isolated from succeeding swabs during the observation period. In 20 patients new types were introduced, but the original strain remained. In 23 patients the first strain was replaced by one other strain, in eight patients two or more. Strains of type 95 seemed to have a high colonization priority, whereas strains of group III had a low one. In 1986 phage-typing was performed on two or more S. aureus strains from the same patient, in 4561 instances. Recurrence of strains of the same phage-type pattern was demonstrated in 70% of the patients when the first and the fourth sample were compared. The "newer epidemic" strains of phage-type 95 and of the 94,96 complex had the highest percentage of recurrence (more than 80%) when adjacent samples were compared, and 68-69% when the first and the fourth sample were compared. The good colonization capacity of these strains might be one of the explanations why they occur frequently today although they are resistant only to penicillin.     

Susceptibility patterns of Staphylococcus in a family practice population.

Nasal swabs were obtained from 408 patients seen in a family practice office in an attempt to identify Staphylococcus aureus carriers. Isolated strains were tested for sensitivity to 11 antibiotics. Study participants were interviewed to obtain the following data: age, history of recent hospitalization and/or recent antibiotic use, number of household members, and occupation, if employed in a health-care facility. S aureus was isolated from 109 nasal swabs. This represents a 26.7 percent carrier rate. Only 25.7 percent of the isolates were sensitive to penicillin G and ampicillin. No statistically significant association was found between the patient variables and either the carrier rate or the sensitivity of the S aureus isolates to penicillin. The sensitivity testing demonstrated that 94.5 percent of the isolates were sensitive to tetracycline and erythromycin. Ninety-nine to 100 percent of the isolates were sensitive to all other antibiotics tested. The authors conclude that penicillin G should not be used in the treatment of S aureus infections. Erythromycin, due to demonstrated sensitivity and reasonable cost, is recommended for mild to moderate infections.     

Predictive value and cost-effectiveness analysis of a rapid polymerase chain reaction for preoperative detection of nasal carriage of Staphylococcus aureus.

OBJECTIVE: To determine the accuracy and cost-effectiveness of a polymerase chain reaction (PCR) for detecting nasal carriage of Staphylococcus aureus directly from clinical specimens. CROSS-SECTIONAL STUDY: This occurred in a tertiary-care hospital in Cleveland, Ohio, and included 239 consecutive patients who were scheduled for a cardiothoracic surgical procedure. Conventional cultures and a PCR for S. aureus from nasal swabs were used as measurements. COST-EFFECTIVENESS ANALYSIS: Data sources were market prices and Bureau of Labor Statistics. The time horizon was the maximum period for availability of culture results (3 days). Interventions included universal mupirocin therapy without testing; initial therapy, with termination if PCR negative (treat-PCR); initial therapy, with termination if culture negative (treat-culture); treat PCR-positive carriers (PCR-guided treatment); and treat culture-positive carriers (culture-guided treatment). The perspective was institutional and costs and the length of time to treatment were outcome measures. RESULTS: Sixty-seven (28%) of the 239 swabs grew S. aureus. Rapid PCR was 97.0% sensitive and 97.1% specific for the detection of S. aureus. For populations with prevalences of nasal S. aureus carriage of up to 50%, the PCR assay had negative predictive values of greater than 97%. PCR-guided treatment had the lowest incremental cost-effectiveness ratio (1.93 dollars per additional day compared with the culture strategy). Among immediate treatment strategies, treat-PCR was most cost-effective. The universal therapy strategy cost 38.19 dollars more per additional day gained with carrier identification compared with the PCR strategy. CONCLUSION: Rapid real-time PCR is an accurate, rapid, and cost-effective method for identifying S. aureus carriers for preoperative intervention.     

Spread of Staphylococcus aureus strains of phage-type 95 in Denmark 1968-1989.

The spread of Staphylococcus aureus strains of phage-type 95 was traced retrospectively in Denmark by the review of more than 15,000 S. aureus bacteraemia isolates (1957-88) and from data collected by phage-typing of c. 260,000 isolates from all body sites (1977-89). The first two type 95 strains had been isolated from blood in 1968, and after an interval of 3 years there was a steady increase of bacteraemia strains all over Denmark. From 1977 to 1989 the incidence of type 95 strains among isolates from all body sites increased from 3.8 to 18.8%. Different patterns of increase were recorded in 13 major hospitals and in various clinical departments of two hospitals and these were further analysed. Conjunctival swabs gave the highest percentage of type 95 strains and those from abscesses gave the lowest percentage. Of the type 95 bacteraemia strains 90.4% were resistant to penicillin, but neither methicillin nor gentamicin resistance was recorded.     

Nasal carriage and antibiotic resistance of Staphylococcus aureus isolates from hospital and non-hospital personnel in Abha, Saudi Arabia

The prevalence of nasal carriage of Staphylococcus aureus, antibiograms and prevalence of methicillin-resistant S. aureus (MRSA) were studied in 1999 among healthy hospital and non-hospital personnel in Abha, Saudi Arabia. S. aureus was isolated from 26.1% of 299 adults in the community and 25.4% of 279 hospital personnel. No isolate was resistant to vancomycin. Antibiotic resistance rates, for all other antibiotics tested except cephalothin, were significantly higher for strains from hospital personnel (P values < 0.001-0.04) compared to non-hospital adults. The antibiograms were also compared with those of 140 clinical isolates. The rates of resistance of the inpatient strains to all the antibiotics tested were significantly higher than those of hospital nasal carrier strains (P < 0.001-0.05). MRSA was isolated, respectively, from 5.1% and 18.3% of non-hospital and hospital carriers; MRSA carriage rates were 1.3% and 4.7%, respectively, for non-hospital and hospital carriers, and 61% of S. aureus isolates from infected patients were MRSA. Only 8% of non-hospital but 44% of hospital carrier strains were multiply resistant (P < 0.001). Multiple resistance among inpatient strains (89%) was significantly higher than that among hospital nasal strains (44%) (P < 0.001). Such rates of multiple resistance and endemic MRSA prevalence among healthy carriers (11%) at a much higher rate than those reported in the literature should raise concern in a region with unrestricted availability of antibiotics.     

Carriage of Staphylococcus aureus and of gram-negative bacilli resistant to third-generation cephalosporins in cirrhotic patients: a prospective assessment of hospital-acquired infections.

OBJECTIVE: To study the relation between Staphylococcus aureus nasal and stool colonization, stool carriage of gram-negative bacilli resistant to third-generation cephalosporins (CephR), and subsequent infections during hospitalization. DESIGN: Prospective study. PATIENTS: 551 cirrhotic patients with 589 consecutive hospital stays. All patients were screened within 48 hours of admission; 589 nasal swabs, 417 stool specimens, and 589 urine samples were analyzed. RESULTS: Carriage rates were 18.8% for methicillin-sensitive S aureus (MSSA), 16.3% for methicillin-resistant S aureus (MRSA), and 13.7% for CephR. We observed 87 episodes of spontaneous bacterial peritonitis, 63 cases of bacteremia, and 167 urinary tract infections occurred. Only 1 case of bacteremia and 4 urinary tract infections due to CephR occurred in patients carrying the same organism in their stools. The risk of MRSA ascitic fluid infections, bacteremia, and urinary tract infections was 3.1% versus 1% (not significant), 8.3% versus 0.8% (P<.001), and 11.4% versus 0.6% (P<.001) in carriers and noncarriers, respectively. Pulsed-field gel electrophoresis (PFGE) of isolates from 16 patients infected by MSSA (3 cases) and MRSA (13 cases) demonstrated that the colonizing strains matched the invasive strains in the 3 MSSA cases and in 8 of 13 MRSA cases. CONCLUSION: Carriage of CephR strains is not associated with subsequent infection by these organisms in hospitalized cirrhotic patients. In contrast, MRSA carriage was an important risk factor for MRSA bacteremia and urinary tract infection.     

The decline of methicillin resistance among Danish Staphylococcus aureus strains

OBJECTIVE: To describe the occurrence and decline of methicillin-resistant Staphylococcus aureus in Denmark from 1966 to 1986, and to illustrate why it has been possible to retain a frequency of only 0.2% MRSA since 1984. DESIGN: A study of antibiotic susceptibility and phage-type of 522,978 S aureus strains isolated from hospitalized patients in Denmark during the years 1960 to 1988 combined with clinical information on patients with methicillin-resistant strains during the years 1986 through 1988. SETTING: All strains and information were collected at the centralized, national laboratory for S aureus phage-typing. PATIENTS: Hospitalized patients with S aureus isolates, and especially patients with methicillin-resistant strains. INTERVENTION: Antibiotic treatment. RESULTS: The frequency of MRSA rose to 15% in the years 1967 through 1971 but decreased to 0.2% in 1984, and has remained so ever since. The increase was due mainly to the spread of a single or a few clones of the phage-type complex 83A. Occurrence of strains of these phage-types declined from 18% in 1969 to 0.6% in 1989. In 1986 through 1988, at least 48% of the MRSA strains were imported by patients from abroad. Cross-infection occurred only in two cases. High awareness and special precautions were taken when MRSA was detected. CONCLUSIONS: MRSA of a single or a few clones spread in Danish hospitals in the years 1967 through 1971. Since 1984, only 0.2% of the Danish S aureus population has been MRSA, and imported MRSA strains have been prevented from spreading.     

Evidence of enterotoxins and toxic shock syndrome toxin (TSST-1) in strains of Staphylococcus aureus isolated from various biological materials

Among 413 strains of S. aureus isolated from patients with chronic staphylococcal infections, from haemocultures in bacteriaemia and septic conditions, from gynaecological materials and nasal plugs of healthy carriers the authors detected the production of one or several types of enterotoxins in 124 strains (30.0%), production of TSST-1 in 19 strains (4.6%) and the concurrent production of enterotoxins and TSST-1 in 38 strains (9.2%). The highest ratio of toxigenic strains of S. aureus was found in departments (51.4%) and from hospitalized patients in blood cultures in bacteriaemias and septic conditions (41.2%). In a group of 184 strains from patients with chronic staphylococcal infection toxin production was proved in 49 strains (26.6%). Of 74 strains of S. aureus isolated from healthy carriers there were 16 toxigenic strains (21.6%). The most frequent type of enterotoxins were enterotoxins type A (26.7%) and C (24.4%). 21 strains (24.4%) produced more than one type of enterotoxins.     

Staphylococcus aureus rectal carriage and its association with infections in patients in a surgical intensive care unit and a liver transplant unit.

BACKGROUND: The role of rectal carriage of Staphylococcus aureus as a risk factor for nosocomial S. aureus infections in critically ill patients has not been fully discerned. METHODS: Nasal and rectal swabs for S. aureus were obtained on admission and weekly thereafter until discharge or death from 204 consecutive patients admitted to the surgical intensive care unit and liver transplant unit RESULTS: Overall, 49.5% (101 of 204) of the patients never harbored S. aureus, 21.6% (44 of 204) were nasal carriers only, 3.4% (7 of 204) were rectal carriers only, and 25.5% (52 of 204) were both nasal and rectal carriers. Infections due to S. aureus developed in 15.7% (32 of 204) of the patients; these included 3% (3 of 101) of the non-carriers, 18.2% (8 of 44) of the nasal carriers only, 0% (0 of 7) of the rectal carriers only, and 40.4% (21 of 52) of the patients who were both nasal and rectal carriers (P - .001). Patients with both rectal and nasal carriage were significantly more likely to develop S. aureus infection than were those with nasal carriage only (odds ratio, 3.9; 95% confidence interval, 1.18 to 7.85; P= .025). By pulsed-field gel electrophoresis, the infecting rectal and nasal isolates were clonally identical in 82% (14 of 17) of the patients with S. aureus infections. CONCLUSIONS: Rectal carriage represents an underappreciated reservoir for S. aureus in patients in the intensive care unit and liver transplant recipients. Rectal plus nasal carriage may portend a greater risk for S. aureus infections in these patients than currently realized.     

Staphylococcus aureus in Antarctica: carriage and attempted eradication

The carriage of Staphylococcus aureus was studied in a group of 28 men living in a totally isolated environment for a year. Initially, nasal, axillary and perineal swabs were taken at weekly intervals, but from week 24 throat swabs were taken from known nasal carriers. Several attempts were made during the study to eradicate S. aureus. Eight subjects consistently carried their own phage type throughout the study, despite the application of antibacterial agents. In three subjects strains were isolated late in the study of a phage type which had either not been isolated before in this study, or had not been found for a prolonged period. Nine of the 12 nasal carriers also yielded S. aureus from the throat. It is apparent that following attempted eradication, S. aureus may seem to disappear, only to reappear some time later; 'eradication' in this case would be an erroneous appellation.     

Antimicrobial sensitivity patterns of hospital and non-hospital strains of Staphylococcus aureus isolated from nasal carriers.

The nasal carriage rate of Staphylococcus aureus was significantly higher in hospitalized persons (children, adult females and staff) - 53.8%, - than in similar persons at a local clinic - 29.8% (P less than 0.001) - in Ile-Ife, Nigeria. However, unlike studies carried out elsewhere, a higher proportion of S. aureus strains obtained from persons at the clinic were resistant to commonly used antimicrobial agents than were strains isolated in the hospital. This has been attributed to the ease at which these drugs can be obtained by the general population and used unsupervised and indiscriminately. Methicillin was the most effective antimicrobial agent against pathologic staphylococci (2.2% resistance), followed by erythromycin (16.5% resistance), co-trimaxozole (28.0% resistance), chloramphenicol (76.9% resistance), tetracycline (78.6% resistance) and penicillin and ampicillin (97.8% resistance). The widespread resistance of S. aureus to penicillin and ampicillin (and other antimicrobial agents) is of clinical significance in the treatment of post-operative infections, since carriers are reportedly more prone to such infections than are non-carriers.     

Staphylococcus aureus in Antarctica: carriage and attempted eradication.

The carriage of Staphylococcus aureus was studied in a group of 28 men living in a totally isolated environment for a year. Initially, nasal, axillary and perineal swabs were taken at weekly intervals, but from week 24 throat swabs were taken from known nasal carriers. Several attempts were made during the study to eradicate S. aureus. Eight subjects consistently carried their own phage type throughout the study, despite the application of antibacterial agents. In three subjects strains were isolated late in the study of a phage type which had either not been isolated before in this study, or had not been found for a prolonged period. Nine of the 12 nasal carriers also yielded S. aureus from the throat. It is apparent that following attempted eradication, S. aureus may seem to disappear, only to reappear some time later; ''eradication'' in this case would be an erroneous appellation.     

Simultaneous occurrence of enterotoxigenic Staphylococcus aureus on the hands, mouth and feces of asymptomatic carriers

One hundred and twelve asymptomatic individuals were analysed with regard to the simultaneous incidence of Staphylococcus aureus on their hands and in their nose, mouth and stools, in the city of S. Paulo (Brazil). A total of 40 (35.7%) individuals were detected as carriers of this microorganism. Among these carriers, 27 (67.5%) were positive in only one of the four niches studied, 8 (20.0%) in two and 5 (12.5%) in three niches. They were identified 113 Staphylococcus aureus strains, and 28 (24.8%) of these strains, isolated from 9 (22.5%) carriers, produced enterotoxin. Of these strains, 7 (25.0%) produced type A enterotoxin, 6 (21.4%) of type B, 11 (39.3%) type C and 4 (14.3%) produced both type A and C. The phage typing of the 113 Staphylococcus aureus strains revealed the predominance of the strains lysed by phages belonging to the Group I/III/NC (16.8%). The results obtained did not demonstrate the simultaneous incidence of Staphylococcus aureus strains in samples collected from mouth, hands and stools of the group studied.     

社区分离金黄色葡萄球菌在健康人群中的分布及其分子生物学特点

目的 调查医科大学学生鼻腔中金黄色葡萄球菌(金葡菌)的定植状况,解析鼻腔定植社区型甲氧两林耐药性金葡菌(MRSA)克隆的分子生物学特点.方法 以无菌棉签从调查对象鼻腔中收集定植菌,鉴定出甲氧西林敏感性金葡菌(MSSA)和MRSA;多重PCR法分型MRSA携带的SCCmec基因岛;PCR测定pvl、seh、tsst1等毒素基因在菌株中的分布;脉冲场凝胶电泳(PFGE)检测MRSA菌株的脉冲场型.结果 2009年977名学生488份样本中鉴定出葡萄球菌,其中凝固酶阴性葡萄球菌(CoNS)和金葡菌分别为364份和124份,MRSA在金葡菌中所占比例为3.4%.2010年调查显示,657名学生中有310份样本鉴定为葡萄球菌属,其中CoNS为195份,金葡菌115份,MRSA在金葡菌中所占比例为7.7%.金葡菌在所有葡萄球菌属中所占比例为29.9%,而MRSA在金葡菌中所占比例为5.1%.MRSA菌株中共鉴定出5种SCCmec基因岛型,其中Ⅳa型最多(10株),为优势SCCmec基因岛类型.PFGE共有11种图谱型,7种(A～G)脉冲场型.10株MRSA均为pvl阳性.结论 1株起源于社区,基因型为Ⅳa SCCmec-pulsotype A且携带pvl毒素基因的特定MRSA克隆在健康大学生中传播.

Abstract：

Objective To investigate the nasal colonization of Staphylococcus (S.) aureus strains among medical university students in Shenyang and to study the molecular epidemiological characteristics of methicillin resistant S. aureus (MRSA) strains. Methods Sterilized nasal swabs were used to collect nasal bacteria from both nares of the students. Nasal specimens were further identified as S. aureus strains, sensitive or resistant to methicillin through a series of tests. Molecular related methods including staphylococcal cassette chromosome mec (SCCmec) typing, pulsed- field gel electrophoresis (PFGE) , coagulase isotyping and minimum inhibitory concentration (MIC) determination etc. were used to characterize the isolates. Prevalence of the panton-valentine leukocidin (pvl) genes (lukS and F-PV) among the isolates was also assessed. Results Staphylococci were found in 488 specimens from 977 participants through the surveillance program, conducted in 2009. Of the 488 specimens being tested, 364 were identified as coagulase-negative staphylococci (CoNS) and 124 as S. aureus. MRSA strain among the S. aureus isolates was accounted for 3.4%. In the surveillance program conducted in 2010, staphylococci grew in 310 specimens fiom 657 participants. Of the 310 specimens tested, 195 were identified as CoNS and 115 as S. aureus. The percentage of MRSA strains among the S. aureus isolates was 7.7%. In total, 239 students carried S.aureus, and the percentage of MRSA carriers among the total specimens tested in this study was 5.1%.Most of the MRSA strains could be classified into one of the five types of SCCmec elements. Type Ⅳ a SCCmec strains were most frequent seen overall (10 isolates). A total of 11 pulsotypes were identified among the MRSA strains and were classified into 7 major groups (A to G) by the mutual correlations of their banding patterns. Ten MRSA strains were identified as pvl positive strains. Conclusion An MRSA clone (Ⅳ a SCCmec pulsotype A) carrying pvl toxin gene was found to be prevalent in the nares of the healthy university students.     

Enterotoxin A and B production in strains of Staphylococcus aureus isolated from human beings and foods.

The production of enterotoxin A and B by strains of Staphylococcus aureus isolated from nasal swabs of healthy carriers, from lesions of hospital patients and from foods unconnected with outbreaks of food-poisoning was investigated. Sixty-six strains of S. aureus were obtained from human beings, two produced enterotoxin A, 45 produced enterotoxin B, seven produced enterotoxins A + B. Thirty-six strains were isolated from 111 samples of food, one produced enterotoxin A, 16 produced enterotoxin B. The relative incidence of A, B and A + B enterotoxigenicity was assessed.     

新生儿分离的112株金黄色葡萄球菌药物敏感性研究

目的了解新生儿分离的金黄色葡萄球菌(金葡菌)临床分布特点及其耐药性,为临床抗感染治疗提供参考。方法回顾性分析湖南省儿童医院2008年1月-2009年12月分离自新生儿的112株金葡菌资料。结果 112株金葡菌主要分离自呼吸道感染者的痰和咽拭子标本(65.18%,73/112),其次为血液、创面分泌物、脓液标本,分别占12.50%、12.50%、7.14%。金葡菌对克林霉素、红霉素、阿莫西林、青霉素耐药率高,达41.08%～96.43%;耐甲氧西林金葡菌(MRSA)20株,占17.86%,对甲氧西林敏感的金葡菌(MSSA)耐药率明显低于MRSA(P=0.00或P0.05);所有菌株均对万古霉素和利奈唑胺敏感。结论新生儿金葡菌主要分离自呼吸道标本,耐药率较高,新生儿科应加强对金葡菌的监测,合理应用抗菌药物,以延缓耐药菌的产生。     

Antimicrobial susceptibility testing and genotypic characterization of Staphylococcus aureus from food and food animals

Staphylococcus aureus is commonly present in humans and animals. The aim of this study was to investigate antimicrobial resistance and genetic characteristics of S. aureus from food and food animals in Shaanxi Province in China. A total of 332 nasal swabs, breast skin swabs, raw milk, and pork samples were collected from local pig, dairy farms, or local grocery stores and screened for the presence of S. aureus. S. aureus isolates were characterized using antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE) analysis, and polymerase chain reaction for detecting pvl and mecA genes. Methicillin-resistant S. aureus (MRSA) strains were additionally tested for SCCmec type and exfoliative toxin genes. The prevalence of S. aureus was 30.6% in pig nasal swabs, 32.5% in pork, 25.7% in cow nasal swabs, 30.8% in cow breast skin swabs, and 29.3% in milk samples. Resistances were common among isolates tested against erythromycin (65.7%), tetracycline (65.7%), ciprofloxacin (52.7%), followed by gentamicin (36.7%), chloramphenicol (23.1%), cefoxitin (8.3%), and oxacillin (7.7%), but no isolate was resistant to vancomycin, amikacin, or cefoperazone. pvl gene was found in the isolates from all types of samples except from cow nasal swabs. Fourteen isolates from pig nasal swabs contained mecA gene and were considered as MRSA. PFGE analysis showed that nasal isolates differed from food isolates, but isolates from the same animal source appeared to cluster closely. The PFGE patterns of MRSA isolates were different from other S. aureus isolates from pig nasal cavity even though they were from the same source. All the MRSA isolates belonged to SCCmec type IV(b). No isolates contained exfoliative toxin genes. These findings indicated that S. aureus, including multidrug-resistant S. aureus, are widely spread in food animals and animal-derived foods in Shaanxi Province, China. MRSA isolates from pigs may pose potential health risks for workers in swine farms and the community at large.     

Carriage of capsulated strains of Staphylococcus aureus: a population-based study performed in Gulbarga, South India

Staphylococcus aureus is a common human pathogen in community- and hospital-acquired infections and its capsule is involved in pathogenesis. We report here the identification of type-5 and type-8 capsular antigens of S. aureus and the prevalence of such strains among volunteers in various age and population groups from different locations in India. S. aureus carriage rates varied between 18 and 50% with the highest values among university students and the lowest in schoolchildren, aged 6-20 years. There was no difference in carriage rates for males vs. females (P=0.415) or in the socioeconomic status of carriers vs. non-carriers or age dependence. Among the carriage isolates 21% were type-5, 52% were type-8 and the remaining 27% were non-typable. Among invasive isolates these percentages were 6, 64 and 30 respectively. This implies that type-5 strains may be less invasive than type-8 strains (P=0.0015).     

Low prevalence of methicillin-resistant Staphylococcus aureus (MRSA) at hospital admission in the Netherlands: the value of search and destroy and restrictive antibiotic use

In the Netherlands, less than 1% of clinical isolates of Staphylococcus aureus are methicillin-resistant (MRSA). A national search and destroy policy prevents MRSA from becoming endemic. Some MRSA outbreaks cannot be related to patients at risk for MRSA carriage. This study was designed to measure the prevalence of MRSA among patients without risk factors for MRSA carriage at the time of admission to the hospital. In four Dutch hospitals, patients admitted to non-surgical departments in the period 1999-2000 were screened for MRSA nasal carriage. Nasal swabs were streaked on 5% sheep blood agar (BA), submerged in a selective broth, and incubated for two to three days at 35 degrees C. Colonies suspected of being S. aureus were identified with an agglutination test. Susceptibility testing was performed by an automated system and additional oxacillin disk diffusion. Methicillin resistance was confirmed by a DNA hybridization test and mecA PCR. MRSA strains were genotyped by pulsed-field gel electrophoresis (PFGE). Twenty-four percent (2332/9859) of the patients were S. aureus nasal carriers. Only three (0.03%) patients were MRSA carriers. These patients were not repatriated, nor known to be MRSA carriers before screening. Genotyping revealed that the strains were not clonally related and were not related to MRSA outbreaks in the hospital where the patients were admitted. We conclude that at routine admission to a Dutch hospital (excluding high-risk foreign admissions) the MRSA prevalence is low (0.03%), due to the Dutch search and destroy policy and restrictive antibiotic prescribing.