Acquisition of methicillin-resistant Staphylococcus aureus in a large intensive care unit.

OBJECTIVES: To determine the prevalence of MRSA colonization on admission to the ICU and the incidence of MRSA colonization in the ICU. DESIGN: Prospective cohort study. SETTING: University hospital. PARTICIPANTS: Patients admitted to the ICU in 2000-2001. METHODS: Patients were screened for MRSA with nose, throat, groin, and axilla swabs on admission and discharge. MRSA acquisition was defined as a negative admission screen and a positive discharge screen. Risk factors analyzed included previous wards/current unit, gender, age, and length of stay prior to and in the ICU. Univariate and multivariate analyses were performed using logistic regression. RESULTS: Of screened patients, 6.8% were MRSA colonized on admission to the ICU. Some patients (11.4%) became newly colonized during their stay in the ICU. Factors that remained significant in the multivariate analysis of MRSA colonization on admission were previous admission to various wards and length of stay prior to ICU admission of more than 3 days. In the multivariate analysis of MRSA acquisition in the ICU, being a trauma patient and length of stay in the ICU greater than 2 days remained significant Thirty-six percent of patients had both admission and discharge swabs taken.This percentage increased in the presence of a supervisory nurse. CONCLUSION: Significant acquisition of MRSA occurs in the ICU of our hospital, with trauma patients at increased risk. Patients who had been on the cardiothoracic ward prior to the ICU had a lower risk of MRSA colonization on admission. Presence of a supervisory nurse improved compliance with screening     

Epidemiology of methicillin-resistant Staphylococcus aureus colonization in a surgical intensive care unit.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a cause of healthcare-associated infections among surgical intensive care unit (ICU) patients, though transmission dynamics are unclear. OBJECTIVE: To determine the prevalence of MRSA nasal colonization at ICU admission, to identify associated independent risk factors, to determine the value of these factors in active surveillance, and to determine the incidence of and risk factors associated with MRSA acquisition. DESIGN: Prospective cohort study. SETTING: Surgical ICU at a teaching hospital. PATIENTS: All patients admitted to the surgical ICU. RESULTS: Active surveillance for MRSA by nasal culture was performed at ICU admission during a 15-month period. Patients who stayed in the ICU for more than 48 hours had nasal cultures performed weekly and at discharge from the ICU, and clinical data were collected prospectively. Of 1,469 patients, 122 (8%) were colonized with MRSA at admission; 75 (61%) were identified by surveillance alone. Among 775 patients who stayed in the ICU for more than 48 hours, risk factors for MRSA colonization at admission included the following: hospital admission in the past year (1-2 admissions: adjusted odds ratio [aOR], 2.60 [95% confidence interval {CI}, 1.47-4.60]; more than 2 admissions: aOR, 3.56 [95% CI, 1.72-7.40]), a hospital stay of 5 days or more prior to ICU admission (aOR, 2.54 [95% CI, 1.49-4.32]), chronic obstructive pulmonary disease (aOR, 2.16 [95% CI, 1.17-3.96]), diabetes mellitus (aOR, 1.87 [95% CI, 1.10-3.19]), and isolation of MRSA in the past 6 months (aOR, 8.18 [95% CI, 3.38-19.79]). Sixty-nine (10%) of 670 initially MRSA-negative patients acquired MRSA in the ICU (corresponding to 10.7 cases per 1,000 ICU-days at risk). Risk factors for MRSA acquisition included tracheostomy in the ICU (aOR, 2.18 [95% CI, 1.13-4.20]); decubitus ulcer (aOR, 1.72 [95% CI, 0.97-3.06]), and receipt of enteral nutrition via nasoenteric tube (aOR, 3.73 [95% CI, 1.86-7.51]), percutaneous tube (aOR, 2.35 [95% CI, 0.74-7.49]), or both (aOR, 3.33 [95% CI, 1.13-9.77]). CONCLUSIONS: Active surveillance detected a sizable proportion of MRSA-colonized patients not identified by clinical culture. MRSA colonization on admission was associated with recent healthcare contact and underlying disease. Acquisition was associated with potentially modifiable processes of care.     

An outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit.

OBJECTIVE: To describe the epidemiologic and molecular investigations that successfully contained an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) in a neonatal intensive care unit (NICU). DESIGN: Isolates of MRSA were typed by pulsed-field gel electrophoresis (PFGE) and S. aureus protein A (spa). SETTING: A level III-IV, 45-bed NICU located in a children's hospital within a medical center. PATIENTS: Incident cases had MRSA isolated from clinical cultures (eg, blood) or surveillance cultures (ie, anterior nares). INTERVENTIONS: Infected and colonized infants were placed on contact precautions, cohorted, and treated with mupirocin. Surveillance cultures were performed for healthcare workers (HCWs). Colonized HCWs were treated with topical mupirocin and hexachlorophene showers. RESULTS: From January to March 2001, the outbreak strain of MRSA, PFGE clone B, was harbored by 13 infants. Three (1.3%) of 235 HCWs were colonized with MRSA. Two HCWs, who rotated between the adult and the pediatric facility, harbored clone C. One HCW, who exclusively worked in the children's hospital, was colonized with clone B. From January 1999 to November 2000, 22 patients hospitalized in the adult facility were infected or colonized with clone B. Spa typing and PFGE yielded concordant results. PFGE clone B was identified as spa type 16, associated with outbreaks in Brazil and Hungary. CONCLUSIONS: A possible route of MRSA transmission was elucidated by molecular typing. MRSA appears to have been transferred from our adult facility to our pediatric facility by a rotating HCW. Spa typing allowed comparison of our institution's MRSA strains with previously characterized outbreak clones.     

Father-to-infant transmission of community-acquired methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit.

Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly being recognized as a cause of community-acquired infection. Its transmission in neonatal intensive care units (NICUs) has reportedly been linked to a few cases of community-acquired MRSA (CA-MRSA) infection. Here, I describe a case of CA-MRSA transmission from a father to his child in a NICU. Recognition that CA-MRSA may be transmitted in a hospital setting raises important issues for MRSA infection control and treatment options.     

Is methicillin-resistant Staphylococcus aureus more contagious than methicillin-susceptible S. aureus in a surgical intensive care unit?

BACKGROUND AND OBJECTIVE: In the Netherlands, the prevalence of methicillin resistance among Staphylococcus aureus isolates has been kept to less than 1% by using active screening programs and isolation. At the University Medical Center Utrecht (UMCU), an active screening program for methicillin-resistant S. aureus (MRSA) in the surgical intensive care unit (ICU) was implemented in 1986. Between 1992 and 2001, only 6 patients with MRSA were admitted to the surgical ICU. However, 4 of these 6 strains were able to spread to 23 other patients and 15 healthcare workers (HCWs). We were surprised by the epidemic behavior of these strains and wondered whether this was exceptional for S. aureus or whether methicillin-susceptible S. aureus (MSSA) was also spreading in the ICU. DESIGN: A 2-month, prospective, observational study to investigate the incidence and spread of MSSA in the surgical ICU of UMCU and historical data collected during a 10-year period regarding MRSA. SETTING: A 10-bed surgical ICU in a 1,042-bed teaching hospital. RESULTS: Weekly swabs revealed the presence of MSSA in 11 (24%) of 45 patients and 16 (22%) of 72 HCWs. Of all 4,105 patient-HCW contacts, there were only 21 episodes in which both the patient and the HCW were found to carry MSSA. With the use of pulsed-field gel electrophoresis, no identical strains could be identified. CONCLUSION: In our surgical ICU, MRSA seems to spread more easily than MSSA, probably because of selection under antibiotic pressure or a still unknown intrinsic factor within MRSA.     

Nursing staff workload as a determinant of methicillin-resistant Staphylococcus aureus spread in an adult intensive therapy unit.

Acquisition of methicillin resistant Staphylococcus aureus (MRSA) in the intensive care unit of a tertiary referral centre was monitored over a 19-month period. The incidence of new cases of MRSA correlated with peaks of nursing staff workload and times of reduced nurse/patient ratios within the unit. This implies that nurse understaffing contributes significantly to the spread of MRSA in an ITU setting.     

Carriage of multiple subtypes of methicillin-resistant Staphylococcus aureus by intensive care unit patients.

OBJECTIVE: To determine how consistently patients are colonized with methicillin-resistant Staphylococcus aureus (MRSA) at various sites and how many subtypes can be carried simultaneously by a single patient. SETTING: A 28-bed Intensive care unit in a tertiary-care referral hospital. METHODS: A total of 1,181 patients were screened by culture of swab specimens obtained from the nose, throat, groin, and axilla on admission to the intensive care unit (ICU), twice weekly during their ICU stay, and at discharge. RESULTS: MRSA was isolated at least once from 224 patients. Of these isolates, 359 were selected from 32 patients to be subtyped using pulsed-field gel electrophoresis. The rate of compliance with collection of swab specimens was 79.9%. The combination of sites colonized varied frequently over time for many patients. Of patients who had swab specimens obtained twice in 1 day, 8.7% had discordant results from the 2 swab sets. No patient had a clinical isolate that was not of an identical subtype to an isolate from an anatomical site that was sampled for screening. Half the patients carried multiple subtypes during their stay, with up to 4 subtypes per patient. CONCLUSIONS: The findings of this study may indicate that these patients have been colonized with MRSA on more than one occasion, possibly because of multiple breaches in infection control procedure. In MRSA-colonized patients, anatomical sites were intermittently colonized and carriage of multiple subtypes was common. These findings indicate that MRSA carriage is not a fixed state but may vary over time.     

Pulsed field gel electrophoresis typing of coagulase-negative staphylococci with decreased susceptibility to teicoplanin isolated from an intensive care unit

Increased isolation of coagulase-negative staphylococci (CoNS) with decreased susceptibility to teicoplanin prompted this epidemiological survey in the authors intensive care unit. Of 224 medical and surgical patients with hepatobiliary disease, in hospital between December 1998 and July 1999, 14 (6.3%) had at least one isolate of CoNS with decreased susceptibility to teicoplanin. A total of 27 isolates with decreased susceptibility to teicoplanin were recovered from these 14 patients. Pulsed field electrophoresis (PFGE) with Sma I endonuclease demonstrated that CoNS isolates obtained from different patients were unrelated. In addition, different isolates obtain from the same patient were also unrelated, with the exception of two patients. Eighteen out of 27 isolates (66.7%) with decreased susceptibility to teicoplanin were recovered after an earlier treatment with teicoplanin or vancomycin (median 13.1 g, range 2.4-32.7 g per patient). Only four CoNS strains with decreased susceptibility to teicoplanin induced serious infection, all of which responded well to vancomycin therapy.Emergence of CoNS strains with decreased susceptibility to teicoplanin remained limited in hospitalized patients, and was not related to a clonal spread of a particular resistant strain.     

Use of a novel selective medium to detect methicillin-resistant Staphylococcus aureus in colonized patients of an intensive care unit.

BACKGROUND: Detection of colonized patients is important for implementing control measures for methicillin-resistant Staphylococcus aureus (MRSA). Laboratory detection of MRSA carriers is increased by the use of selective screening media, helping control dissemination of such organisms. OBJECTIVE: To evaluate three different media, including selective and nonselective media, in the detection of MRSA from clinical specimens of patients of an intensive care unit (ICU). PATIENTS: Adult patients in the ICU of the Hospital M?e de Deus, Porto Alegre, Brazil. METHODS: A total of 224 specimens were obtained from the nares of patients and plated on blood agar, mannitol salt agar containing 2 microg/mL of oxacillin (MSAO), and oxacillin resistance screening agar base (ORSAB). The presence of MRSA was investigated in typical colonies growing on the three types of media. Discrepant results were resolved by detection of the mecA gene by polymerase chain reaction and the modified penicillin binding protein known as PBP2'. RESULTS: MRSA was detected in 32 (14.3%) of 224 specimens. Blood agar, MSAO, and ORSAB detected MRSA in 17, 31, and 28 specimens, respectively. After the coagulase test, no false resistance was observed. CONCLUSION: MSAO and ORSAB performed equivalently in the detection of MRSA of colonized patients and require a single supplementary test (coagulase) to confirm MRSA.     

Methicillin-resistant Staphylococcus aureus in a general intensive care unit

Methicillin-resistant Staphylococcus aureus (MRSA) has presented special problems in intensive care units (ICUs) because of the difficulties in implementing infection control measures. The prevalence and rate of acquisition of MRSA were studied over thirty months in a nine-bed ICU. Nasal and groin swabs were taken on admission and then weekly, and other cultures as clinically indicated. Of 1361 admissions 119 were MRSA-positive on arrival. 21 cases had been identified before admission and the remainder were detected by screening; in 57 the positive result was known only after discharge. Of the 1242 admissions initially negative 68 acquired MRSA while in the ICU. The ICU had no known MRSA-positive patients on 185 (20.3%) of 914 days, the longest sequence being 17 days. Positive patients occupied 1387 (16.9%) of the 8226 available bed days. Length of stay predicted the risk of acquiring MRSA. Estimated from patients who completed each weekly screening cycle, the risk was 7.5% per week in the first week and 20.3% per week thereafter. The risk was not influenced by initial APACHE II score, the use of haemofiltration, or the number of MRSA-positive patients in the unit. The data suggest that a further 38 of those discharged between weekly screenings acquired MRSA, giving an incidence of 8.5%. MRSA was grown from blood in 17 patients, and from sputum in 53 (ICU-acquired in 18% and 47%). This study suggests that nearly 10% of admissions to a general ICU will be MRSA-positive, of whom only half will be identified before discharge. With standard prevention the risk of previously negative patients acquiring MRSA approximates to 1% per day in the first week and 3% per day thereafter, with nearly one-fifth progressing to bacteraemia; one-half will have MRSA in sputum. Patients with longer stays constitute a high-risk minority for whom additional measures such as decontamination with oropharyngeal and enteral vancomycin should be considered.     

Transmission of methicillin-resistant Staphylococcus aureus in the neonatal intensive care unit from a patient with community-acquired disease.

Methicillin-resistant Staphylococcus aureus (MRSA) has traditionally been a nosocomial pathogen. However, several recent studies have noted community-acquired MRSA among young, healthy patients with no risk factors or healthcare system exposure. We report the transmission of a strain of community-acquired MRSA in our neonatal intensive care unit.     

Methicillin-resistant Staphylococcus aureus in neonatal intensive care unit

A neonatal intensive care unit outbreak was caused by a strain of methicillin-resistant Staphylococcus aureus previously found in the community (ST45-MRSA-IV). Fifteen infected neonates were identified, 2 of whom died. This outbreak illustrates how a rare community pathogen can rapidly spread through nosocomial transmission.     

Effectiveness of simple measures to control an outbreak of nosocomial methicillin-resistant Staphylococcus aureus infections in an intensive care unit

Between June 1985 and March 1986, 14 cases of severe nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection, including septicemia, were observed in the intensive care unit (ICU) of a 400-bed cancer reference center. Simple control measures including contact isolation of colonized patients and reinforcement of handwashing practices among personnel were followed by a sharp decrease in the rate of infection and colonization. An epidemiological investigation showed that a single serophage variant MRSA strain was involved; peak incidence of infection was 17 per 100 ICU patient discharges; the index case was identified as a patient admitted from another hospital and the epidemic strain was then transmitted from patient-to-patient in the ICU; risk factors for acquiring infection were length of prior hospitalization, invasive procedures and number of antibiotic treatments; dissemination of the strain to other wards was only anecdotal. These results stress the effectiveness of simple measures to control outbreaks of MRSA nosocomial infections even in immunocompromised cancer patients.     

"Colonization pressure" and risk of acquisition of methicillin-resistant Staphylococcus aureus in a medical intensive care unit.

OBJECTIVE: To determine the roles of "colonization pressure," work load or patient severity in patient acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in intensive care units (ICUs). DESIGN: Prospectively collected data from October 1996 through December 1998. SETTING: A 12-bed medical ICU in a university-affiliated general hospital. PATIENTS: Patients with risk factors for MRSA admitted to the ICU were screened within 72 hours of admission and weekly thereafter. MRSA was considered imported if detected during the first 72 hours of admission and nosocomial if detected only thereafter. Three screening strategies were used on admission during three consecutive periods. INTERVENTIONS: The unit of time chosen for measurements was the week. Weekly colonization pressure (WCP) was defined as the number of MRSA-carrier patient-days/total number of patient-days. Patient severity (number of deaths, Simplified Acute Physiologic Score [SAPS] II), work load (number of admis sions, Omega score), and colonization pressure (number of MRSA carriers at the time of admission, WCP) were compared with the number of MRSA-nosocomial cases during the following week. RESULTS: Of the 1,016 patients admitted over 116 weeks, 691 (68%) were screened. MRSA was imported in 91 (8.9%) admitted patients (13.1% of screened patients) and nosocomial in 46 (4.5%). The number of MRSA-nosocomial cases was correlated to the SAPS II (P=.007), the Omega 3 score (P=.007), the number of MRSA-imported cases (P=.01), WCP (P<.0001), and the screening period (P<.0001). In multivariate analysis, WCP was the only independent predictive factor for MRSA acquisition (P=.0002). Above 30% of WCP, the risk of acquisition of MRSA was approximately fivefold times higher (relative risk, 4.9; 95% confidence interval, 1.2-19.9; P<.0001). CONCLUSION: Acquisition of MRSA in ICU patients is strongly and independently influenced by colonization pressure.     

Management of outbreaks of methicillin-resistant Staphylococcus aureus infection in the neonatal intensive care unit: a consensus statement.

OBJECTIVE: In 2002, the Chicago Department of Public Health (CDPH; Chicago, Illinois) convened the Chicago-Area Neonatal MRSA Working Group (CANMWG) to discuss and compare approaches aimed at control of methicillin-resistant Staphylococcus aureus (MRSA) in neonatal intensive care units (NICUs). To better understand these issues on a regional level, the CDPH and the Evanston Department of Health and Human Services (EDHHS; Evanston, Illinois) began an investigation. DESIGN: Survey to collect demographic, clinical, microbiologic, and epidemiologic data on individual cases and clusters of MRSA infection; an additional survey collected data on infection control practices. SETTING: Level III NICUs at Chicago-area hospitals. PARTICIPANTS: Neonates and healthcare workers associated with the level III NICUs. METHODS: From June 2001 through September 2002, the participating hospitals reported all clusters of MRSA infection in their respective level III NICUs to the CDPH and the EDHHS. RESULTS: Thirteen clusters of MRSA infection were detected in level III NICUs, and 149 MRSA-positive infants were reported. Infection control surveys showed that hospitals took different approaches for controlling MRSA colonization and infection in NICUs. CONCLUSION: The CANMWG developed recommendations for the prevention and control of MRSA colonization and infection in the NICU and agreed that recommendations should expand to include future data generated by further studies. Continuing partnerships between hospital infection control personnel and public health professionals will be crucial in honing appropriate guidelines for effective approaches to the management and control of MRSA colonization and infection in NICUs.     

Occurrence of co-colonization or co-infection with vancomycin-resistant enterococci and methicillin-resistant Staphylococcus aureus in a medical intensive care unit.

OBJECTIVE: To determine the occurrence of co-colonization or co-infection with VRE and MRSA among medical patients requiring intensive care. DESIGN: Prospective, single-center, observational study. SETTING: A 19-bed medical ICU in an urban teaching hospital. PATIENTS: Adult patients requiring at least 48 hours of intensive care and having at least one culture performed for microbiologic evaluation. RESULTS: Eight hundred seventy-eight consecutive patients were evaluated. Of these patients, 402 (45.8%) did not have microbiologic evidence of colonization or infection with either VRE or MRSA, 355 (40.4%) were colonized or infected with VRE, 38 (4.3%) were colonized or infected with MRSA, and 83 (9.5%) had co-colonization or co-infection with VRE and MRSA. Multiple logistic regression analysis demonstrated that increasing age, hospitalization during the preceding 6 months, and admission to a long-term-care facility were independently associated with colonization or infection due to VRE and co-colonization or co-infection with VRE and MRSA. The distributions of positive culture sites for VRE (stool, 86.7%; blood, 6.5%; urine, 4.8%; soft tissue or wound, 2.0%) and for MRSA (respiratory secretions, 34.1%; blood, 32.6%; urine, 17.1%; soft tissue or wound, 16.2%) were statistically different (P < .001). CONCLUSIONS: Co-colonization or co-infection with VRE and MRSA is common among medical patients requiring intensive care. The recent emergence of vancomycin-resistant Staphylococcus aureus and the presence of a patient population co-colonized or co-infected with VRE and MRSA support the need for aggressive infection control measures in the ICU.