Increasing occurrence of methicillin-resistant Staphylococcus aureus in the United States

Inhibition of α-hemolysin activity of Staphylococcus aureus by theaflavin 3,3'-digallate

The ongoing rise in antibiotic resistance, and a waning of the introduction of new antibiotics, has resulted in limited treatment options for bacterial infections, including these caused by methicillin-resistant Staphylococcus aureus, leaving the world in a post-antibiotic era. Here, we set out to examine mechanisms by which theaflavin 3,3'-digallate (TF3) might act as an anti-hemolytic compound. In the presented study, we found that TF3 has weak bacteriostatic and bactericidal effects on Staphylococcus aureus, and strong inhibitory effect towards the hemolytic activity of its α-hemolysin (Hla) including its production and secretion. A supportive SPR assay reinforced these results and further revealed binding of TF3 to Hla with KD = 4.57×10-5 M. Interestingly, TF3 was also able to protect human primary keratinocytes from Hla-induced cell death, being at the same time non-toxic for them. Further analysis of TF3 properties revealed that TF3 blocked Hla-prompting immune reaction by inhibiting production and secretion of IL1β, IL6, and TNFα in vitro and in vivo, through affecting NFκB activity. Additionally, we observed that TF3 also markedly attenuated S. aureus-induced barrier disruption, by inhibiting Hla-triggered E-cadherin and ZO-1 impairment. Overall, by blocking activity of Hla, TF3 subsequently subdued the inflammation and protected the epithelial barrier, which is considered as beneficial to relieving skin injury.

Antibacterial photodynamic peptides for staphylococcal skin infection

A multicomponent system centered on antibacterial photodynamic peptides and supported by a regenerative gelatin–collagen (Gel–Col) hydrogel.

Staphylococcus aureus Toxins and Their Molecular Activity in Infectious Diseases

Staphylococcus aureus is a microorganism resident in the skin and nasal membranes with a dreadful pathogenic potential to cause a variety of community and hospital-acquired infections. The frequency of these infections is increasing and their treatment is becoming more difficult. The ability of S. aureus to form biofilms and the emergence of multidrug-resistant strains are the main reasons determining the challenge in dealing with these infections. S. aureus' infectious capacity and its success as a pathogen is related to the expression of virulence factors, among which the production of a wide variety of toxins is highlighted. For this reason, a better understanding of S. aureus toxins is needed to enable the development of new strategies to reduce their production and consequently improve therapeutic approaches. This review focuses on understanding the toxin-based pathogenesis of S. aureus and their role on infectious diseases.

Should We Vigorously Try to Contain and Control Methicillin-Resistant Staphylococcus aureus?

Objective:

To review practices currently used to control transmission of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals, determine the frequency of their use, and discuss the indications for implementing such measures.

Design:

A questionnaire survey to determine how commonly selected control practices are used, and a literature review of the efficacy of control practices.

Participants:

Two hundred fifty-six of 360 hospital-based members fo the Society for Hospital Epidemiology of America, Inc. (SHEA) completed the survey questionnaire.

Result:

Many different combinations of surveillance and control measures are used by hospitals with MRSA. Nine percent of hospitals stated that no special measures were used to control MRSA. The efficacy of commonly used control measures has not been established by controlled trials.

Conclusions:

Implementing control measures is warranted when MRSA causes a high incidence of serious nosocomial infections, and is desirable when MRSA has been newly introduced into a hospital or into an intensive care unit, or when MRSA accounts for more than 10% of nosocomial staphylococcal isolates. While the value of some practices is well established, measures such as routinely attempting to eradicate carriage of MRSA by colonized patients and personnel require further evaluation.

Prevention of Recurrent Staphylococcal Skin Infections

Staphylococcus aureus infections pose a significant health burden. The emergence of community-associated methicillin-resistant S aureus has resulted in an epidemic of skin and soft tissue infections (SSTI), and many patients experience recurrent SSTI. As S aureus colonization is associated with subsequent infection, decolonization is recommended for patients with recurrent SSTI or in settings of ongoing transmission. S aureus infections often cluster within households, and asymptomatic carriers serve as reservoirs for transmission; therefore, a household approach to decolonization is more effective than measures performed by individuals alone. Novel strategies for the prevention of recurrent SSTI are needed.

The world's microbiology laboratories can be a global microbial sensor network

The microbes that infect us spread in global and local epidemics, and the resistance genes that block their treatment spread within and between them. All we can know about where they are to track and contain them comes from the only places that can see them, the world's microbiology laboratories, but most report each patient's microbe only to that patient's caregiver. Sensors, ranging from instruments to birdwatchers, are now being linked in electronic networks to monitor and interpret algorithmically in real-time ocean currents, atmospheric carbon, supply-chain inventory, bird migration, etc. To so link the world's microbiology laboratories as exquisite sensors in a truly lifesaving real-time network their data must be accessed and fully subtyped. Microbiology laboratories put individual reports into inaccessible paper or mutually incompatible electronic reporting systems, but those from more than 2,200 laboratories in more than 108 countries worldwide are now accessed and translated into compatible WHONET files. These increasingly web-based files could initiate a global microbial sensor network. Unused microbiology laboratory byproduct data, now from drug susceptibility and biochemical testing but increasingly from new technologies (genotyping, MALDI-TOF, etc.), can be reused to subtype microbes of each genus/species into sub-groupings that are discriminated and traced with greater sensitivity. Ongoing statistical delineation of subtypes from global sensor network data will improve detection of movement into any patient of a microbe or resistance gene from another patient, medical center or country. Growing data on clinical manifestations and global distributions of subtypes can automate comments for patient's reports, select microbes to genotype and alert responders.

Rationale for eliminating Staphylococcus breakpoints for β-lactam agents other than penicillin, oxacillin or cefoxitin, and ceftaroline

Due to the ongoing concern about the reliability of Staphylococcus breakpoints (interpretive criteria) for other β-lactam agents, the Clinical and Laboratory Standards Institute recently approved the elimination of all breakpoints for antistaphylococcal β-lactams except for penicillin, oxacillin or cefoxitin, and ceftaroline. Routine testing of penicillin and oxacillin or cefoxitin should be used to infer susceptibility for all β-lactams with approved clinical indications for staphylococcal infections. It is critical for laboratories to reject requests for susceptibility testing of other β-lactams against staphylococci and to indicate that susceptibility to these agents can be predicted from the penicillin and oxacillin or cefoxitin results. This article reviews β-lactam resistance mechanisms in staphylococci, current antimicrobial susceptibility testing and reporting recommendations for β-lactams and staphylococci, and microbiologic data and clinical data supporting the elimination of staphylococcal breakpoints for other β-lactam agents.

Hospital and provider patient volumes, cesarean section rates, and early postpartum invasive methicillin-resistant Staphylococcus aureus infection

OBJECTIVE

We sought to examine whether hospital and provider volumes and cesarean section rates influenced early postpartum invasive methicillin-resistant Staphylococcus aureus (MRSA) infection.

METHODS

We used data from the Nationwide Inpatient Sample, a representative sample of US community hospitals. Multivariate hierarchical regression models were used to estimate odds ratios adjusted for hospital total discharges, nurse:patient ratio, urbanicity, teaching status, bed size, ownership, and geographic region and patient age, race, expected payer, and comorbidities.

RESULTS

The total sample size for the hospital analysis was 3,487,350 deliveries, which included 555 cases of MRSA infection. The total sample size for the provider analysis was 1,186,703 deliveries, with 221 cases of MRSA infection. Hospital and provider patient (deliveries) volumes and cesarean section rates were not associated with early postpartum invasive MRSA infection.

CONCLUSIONS

Barring major bias in our estimates, our results suggest that transmission from providers may not be a predominant route of postpartum MRSA infection in US hospitals.

Antimicrobial resistance in the intensive care unit: mechanisms, epidemiology, and management of specific resistant pathogens

Infections caused by drug-resistant and multidrug-resistant microbial pathogens pose tremendous challenges to health care systems, including challenges related to the diagnosis, treatment, and containment of these infections. These challenges are amplified in the intensive care unit (ICU), where pressures for selection and emergence of resistance and risks of transmission of resistant pathogens are highest, and where the threat of resistance drives selection of empiric antimicrobial regimens. This article reviews basic concepts of resistance to antibacterial agents including mechanisms and modes of transmission, and discusses management issues for the important drug-resistant pathogens found in the ICU.

Universal MRSA nasal surveillance: characterization of outcomes at a tertiary care center and implications for infection control

BACKGROUND

Recognition of methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage by active surveillance cultures has been widely debated. Our institution implemented universal nasal screening by polymerase chain reaction (PCR) for MRSA and isolation of screen positive patients in December 2007. Here we present data about the correlation between screen positivity and subsequent development of infection and the impact of isolation on surgical site infection rates.

METHODS

This was a retrospective, observational study from January 1, 2008, through June 30, 2008, on all inpatient admissions with a nasal MRSA PCR screen. Genotype of 15 MRSA blood isolates was determined utilizing the Diversilab® (bioMérieux, Hazelwood, MO) system. A phenotypic rule was deduced and utilized for analyzing all MRSA clinical isolates.

RESULTS

5375 patients were screened at ≤48 hours following admission. 581 MRSA positive nasal carriers (10.80%) were identified. 496 (85.3%) were asymptomatic MRSA nasal carriers. There were a total of 158 MRSA clinical infections. 85 (14.6%) MRSA nasal carriers had clinical infection. Of the 4794 (89.1%) non-nasally colonized patients, 73 (1.5%) had MRSA clinical infection. MRSA surgical site infection rate remained unchanged during the intervention period. Phenotypic predictive rule inferred 59.8% community-acquired MRSA (CA-MRSA) infections and 40% hospital-acquired MRSA (HA-MRSA) infections.

CONCLUSIONS

Our study showed a positive correlation between having a nasal screen positivity and subsequent development of infection. Isolation of MRSA screen positive patients alone as an intervention did not reduce the surgical site infection rates. Since most of our isolates are CA-MRSA, our institution is implementing several new interventions to further reduce the incidence of HA-MRSA conditions.

Radiological findings of community-acquired methicillin-resistant and methicillin-susceptible Staphylococcus aureus pediatric pneumonia in Hawaii

BACKGROUND

Community-acquired Staphylococcus aureus (CA-SA) infections are common among pediatric patients in Hawaii.

OBJECTIVE

We wanted to characterize the radiological features of methicillin-susceptible (CA-MSSA) and methicillin-resistant (CA-MRSA) staphylococcal pneumonia in Hawaiian children.

MATERIALS AND METHODS

We retrospectively reviewed medical records and imaging studies of children with SA pneumonia identified from 1996 through 2007.

RESULTS

Of 40 children, 26 (65%) had CA-MRSA pneumonia and 14 patients (35%) had CA-MSSA pneumonia. CA-MRSA patients were significantly younger than CA-MSSA patients (65% younger than 1 year vs. 36% older). In a majority (62%) of CA-MRSA patients, the consolidation was unilateral; in most of the CA-MSSA cases (79%), the consolidation was bilateral. Fifty percent of the patients with CA-MRSA and 21% of those with CA-MSSA had pneumatoceles (P = 0.1). CA-MRSA patients more commonly had pleural effusions (85% vs. 64% for CA-MSSA) and pleural thickening (50% vs. 36% for CA-MSSA).

CONCLUSION

This case series describes the radiologic characteristics of CA-MRSA and CA-MSSA pneumonia in children in a highly endemic area. We found that CA-MRSA pneumonias are unilateral in a majority of pediatric pneumonia cases, are more common in children 1 year or younger, and have higher rates of complications in comparison to CA-MSSA patients.

Community-acquired Staphylococcus aureus pneumonia among hospitalized children in Hawaii

SUMMARY BACKGROUND

Invasive community acquired (CA) Staphylococcus aureus (SA) disease has been endemically observed in Hawaiian children. We wanted to evaluate the clinical, laboratory findings, and outcomes of methicillin-resistant SA (MRSA) and methicillin-susceptible SA (MSSA) associated pneumonia admissions.

METHODS

We performed retrospective chart reviews of 38 culture proven SA pneumonia patients admitted to a pediatric tertiary medical center in Hawaii between January 1996 to December 2007.

RESULTS

Twenty-six patients (68%) had MRSA and 12 patients (32%) had MSSA infection. The mean age of MRSA patients was 2.8 and 6.7 years for MSSA patients (P < 0.05). Pacific Islander and Native Hawaiian patients were affected disproportionately compared to non-Pacific Islander and Hawaiian groups (P < 0.0001). Demographic data, days of fever, tachypnea, hypoxia, and length of stay (LOS) were not significantly different between MRSA and MSSA infected patients. The mean LOS was 26.2 days (range 6-138 days); mean length of fever was 12.4 days. Seventy five percent (15 of 20) of patients who required intubation had MRSA. Twenty-one of the 29 (72%) total patients with pleural effusions had MRSA infection and all required chest tube placements. Two (5%) patients died; both had MRSA infection.

CONCLUSIONS

Younger Pacific Islander/Native Hawaiian children were affected disproportionately and had MRSA infection more frequently. MRSA infected patients appeared to have severe disease with frequent chest tube placement, intubation, and fatality. Overall, both MRSA and MSSA pneumonia resulted in prolonged hospitalization, multiple complications, and significant healthcare costs.

Staphylococcal colonization of caretakers of children who have community-acquired skin and soft tissue infections

PURPOSE

Colonization with Staphylococcus aureus is considered a risk factor for the rising incidence of pediatric community-acquired skin and soft tissue infections (CA-SSTIs), and intrafamily spread is thought to be the source of colonization.

METHODS

A prospective study was conducted to determine skin and nasal staphylococcal colonization rates among the caretakers of CA-SSTI patients and those of nonabscess controls. A questionnaire regarding risk factors was administered to all participants. Fisher's Exact test and the chi(2) test were used for statistical analysis.

RESULTS

Forty-six patients and their caretakers were enrolled in both the study and control groups. Of the caretakers in the study group, 19.6% (n = 9) had staphylococcal colonization of nares; and 2.2% (n = 1), skin. In the control group, 17.4% (n = 8) had nasal colonization; and none had skin colonization. Of the children in the study group, 58.7% (n = 27) had a family history of CA-SSTI compared with only 17.4% (n = 8) of controls (P = .0001). Of CA-SSTI patients, 45.7% (n = 21) had prior abscesses compared with 6.5% (n = 3) of controls (P = .0001). No other risk factor was identified.

CONCLUSION

There was no increase in nasal or skin staphylococcal colonization among caretakers of children with CA-SSTI. Family and personal histories of CA-SSTI were the only identified risk factors for CA-SSTI.

Staphylococcus aureus osteomyelitis in Hawaii

BACKGROUND

The clinical and laboratory findings and outcomes of methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) Staphylococcus aureus osteomyelitis have not been studied in Hawaii.

METHODS

Retrospective inpatient chart reviews of 62 culture-proven osteomyelitis patients between 1996 and 2007 were performed.

RESULTS

Fifteen patients (24%) had MRSA infection, and 47 patients (76%) had MSSA infection. Length of stay, chronic health problems, total duration of fever, and length of treatment were not significantly different between MRSA- and MSSA-infected patients. The peak erythrocyte sedimentation rate and C-reactive protein values were higher among MRSA infected patients (P values: .009 and .003, respectively).The systemic complication rate was higher in MRSA-infected patients (P value: .018).

CONCLUSIONS

Differing from other pediatric staphylococcal infections in Hawaii, the majority of the patients had MSSA infection. Pacific Islander and Native Hawaiian ethnicities were affected disproportionately and had MRSA infection more frequently. MRSA-infected patients had frequent surgical procedures and systemic complications.

National prevalence of methicillin-resistant Staphylococcus aureus in inpatients at US health care facilities, 2006

BACKGROUND

Despite methicillin-resistant Staphylococcus aureus (MRSA) being endemic in virtually all US health care facilities, there are no data on the prevalence of MRSA in US health care facilities.

METHODS

We conducted a national prevalence survey of MRSA in inpatients at US health care facilities. The survey was developed, received institutional review board approval, and then distributed to all members of the Association for Professionals in Infection Control and Epidemiology, Inc. (APIC). Members were asked to complete the survey on one day during the period October 1 to November 16, 2006, reporting the number of inpatients with MRSA infection or colonization and facility-specific information.

RESULTS

Personnel at 1237 hospitals completed the survey. Complete facility data were provided for 1187 (96%) of these health care facilities. All states were represented (mean, 23 facilities per state; range, 1-99). Respondents reported 8654 MRSA-colonized/infected patients in 187,058 inpatients; the overall MRSA prevalence rate was 46.3 per 1000 inpatients (34 infections and 12 colonizations per 1000 inpatients). Active MRSA surveillance testing was conducted by 29% of respondents: 54% used routine media, 38% used selective media, and 8% used polymerase chain reaction. Detailed data were provided on 7994 (92.4%) MRSA-colonized/infected patients. Our data suggest that approximately 70% of isolates were more consistent with health care-associated MRSA (HA-MRSA) than community-associated MRSA.

CONCLUSION

Our survey documents a much higher MRSA prevalence rate than previous studies using different methodologies. The majority of MRSA in inpatients appears to be HA-MRSA. Given that most facilities did not perform active surveillance testing, these are minimum estimates of the national burden of MRSA in US health care facilities.

Epidemiology of methicillin-resistant Staphylococcus aureus at a pediatric healthcare system, 1991-2003

BACKGROUND

The emergence and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at a Minneapolis pediatric healthcare facility was investigated.

METHODS

Children with MRSA infections from January 1991 to December 2003 were classified as community-associated (CA) or healthcare-associated (HA) using established criteria. Isolates were subtyped using pulsed-field gel electrophoresis and grouped into pulsed-field types (PFTs). Case and isolate characteristics were compared and temporal trends were assessed.

RESULTS

The first isolate classified as CA-MRSA in this healthcare facility was identified in 1991. CA-MRSA cases (n = 188) were more likely than HA-MRSA cases (n = 83) to have a skin or soft tissue infection (80% versus 59%) and to belong to a racial or ethnic minority group (82% versus 55%), whereas HA-MRSA cases were younger (median age, 3.4 years versus 4.9 years). The proportion of both CA- and HA-MRSA isolates susceptible to clindamycin and erythromycin declined during the study period. Isolates classified as CA-MRSA were more likely than HA-MRSA isolates to be USA300 (21% versus 11%, P = 0.05) and USA400 (62% versus 31%, P < 0.001) PFTs. Associations between case race/ethnicity and isolate PFT were observed independent of case classification.

CONCLUSIONS

CA-MRSA is well established in this pediatric population. Although no discernable changes in CA- or HA-MRSA case characteristics were documented during the study period, significant changes were observed in CA-MRSA isolate characteristics, indicating that this pathogen continues to evolve.

An evaluation of different methods for the recovery of meticillin-resistant Staphylococcus aureus from environmental surfaces

Although the association between environmental surfaces contaminated with meticillin-resistant Staphylococcus aureus (MRSA) and hospital infection rates is not fully understood, monitoring programmes can provide an objective starting point for the development and assessment of infection control strategies incorporating improved cleaning. There is, however, no universally accepted method for the recovery of MRSA from environmental surfaces, and the aim of this study was to evaluate a selection of currently available methods. Using five clinical isolates of MRSA and seven protocols, known numbers of bacteria were inoculated on to a stainless steel surface and either recovered immediately (without drying or adsorption) or recovered after 30min (with drying at room temperature and adsorption of cells to the surface). Surfaces were either swabbed or sampled directly by contact methods, and four nutritive media (blood, tryptone soya, oxacillin and meticillin-resistant agars) were tested. Relative sampling efficiencies were determined and the sensitivity of each method per 100cm(2) was calculated. Wide variation in the ability to recover MRSA was found between the different protocols. In the recovery of dried (adsorbed) cells, direct contact methods demonstrated higher sampling efficiency than swabs. The sensitivity of all methods was lower in recovering adsorbed cells from surfaces than unadsorbed cells. Sampling methods consistently proved to be more important than the choice of medium. Dipslides coated with selective agar are recommended for recovering MRSA from flat environmental surfaces.

Community-associated strains of methicillin-resistant Staphylococccus aureus as the cause of healthcare-associated infection

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) isolates from patients with community-associated infection have been described as strains genetically distinct from the strains isolated from patients with healthcare-associated infection. This study examines the hypothesis that community-associated MRSA (CA-MRSA) strains now cause serious infections in hospitalized patients.

METHODS

Thirty-seven clinical MRSA isolates were randomly selected from blood isolates obtained from July 2003 through June 2004. Strains were tested for staphylococcal chromosomal cassette mec (SCCmec) type, pulsed-field gel electrophoresis (PFGE) type, and presence of Panton-Valentine leukocidin (PVL) genes. Medical records review and epidemiologic classification was performed by an investigator blinded to the results of the bacterial strain analysis. Episodes of bloodstream infection were independently classified as either community-associated or healthcare-associated infections, and bacterial isolates were independently classified as either CA-MRSA strains or healthcare-associated MRSA (HA-MRSA) strains, according to established definitions.

SETTING

A tertiary care Veterans Affairs Medical Center.

RESULTS

Twenty-four (65%) of 37 MRSA isolates were SCCmec type IV, a genetic type characteristic of CA-MRSA strains; 22 of these 24 isolates belonged to the CA-MRSA clone USA300 and carried PVL genes. Thirteen (35%) of the 37 strains were SCCmec type II, of which 12 were USA100-ST5 and 12 lacked PVL genes. Thirty patients (81%) had healthcare-associated infections; 18 (60%) of these 30 were infected with isolates carrying markers of CA-MRSA strains. Of 7 patients with CA-MRSA infections, 6 were infected with isolates belonging to the USA300 clone. Patients with healthcare-associated bloodstream infections were as likely to be infected with a CA-MRSA strain as patients with a community-associated infection (P = .38).

CONCLUSIONS

MRSA strains with molecular characteristics of CA-MRSA strains have emerged as an important cause of serious healthcare-associated infection in our hospital.

Methicillin-resistant Staphylococcus aureus in community-acquired pyoderma

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial pathogen. It can also cause community-acquired infections. Indian reports about MRSA in community-acquired infections are rare.

AIM

To evaluate the rate of MRSA in community-acquired pyoderma and the nasal colonisation with S. aureus in such patients.

METHODS

Two hundred and fifty patients with community-acquired pyoderma, who attended outreach camps around Mangalore, south India between January 2000 and July 2001, were studied. Swabs collected from the skin lesions and anterior nares were inoculated onto blood agar and MacConkey's agar. Antimicrobial sensitivity testing was performed using Kirby-Bauer disk diffusion, agar dilution, and agar screen.

RESULTS

Of 250 pyoderma cases, S. aureus was isolated from 202 (80.8%) patients. Twenty-two (10.9%) S. aureus isolates were methicillin resistant, 179 (88.6%) were resistant to penicillin, and 114 (56.4%) were resistant to erythromycin. S. aureus colonization in the anterior nares was observed in 136 (54.4%) cases, 11.8% of which were MRSA. Antibiograms of clinical isolates of S. aureus matched with nasal isolates in 99 (49%) cases.

CONCLUSION

The emergence of MRSA in the community is a warning. A high nasal carriage rate may contribute to recurrent pyoderma. A correct antimicrobial policy and the avoidance of inappropriate antimicrobial usage are mandatory to reduce the spread of MRSA in the community.

Community-acquired methicillin-resistant Staphylococcus aureus in southern New England children

OBJECTIVE

This study was performed to understand the epidemiology of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in southern New England children.

METHODS

A retrospective review was conducted of the medical records of children 0 to 18 years old with MRSA isolated by the Rhode Island Hospital microbiology laboratory (Providence, RI) between 1997 and 2001. A case was classified as either health care-associated MRSA (HCA-MRSA) or CA-MRSA based on time of culture and other strict criteria. The spectrum of illness of the HCA-MRSA and CA-MRSA cases was compared, as were the antibiotic-susceptibility patterns of their isolates. Risk factors for CA-MRSA acquisition were identified, and molecular subtyping of selected isolates was performed.

RESULTS

Between 1997 and 2001, S aureus was isolated from 1063 children. Of these children, 57 had MRSA. During this period, both the absolute number of MRSA cases and the proportion of S aureus cases due to MRSA rose more than threefold due to increases in both CA-MRSA and HCA-MRSA infections. Of the 57 MRSA cases, 23 (40%) were CA-MRSA. CA-MRSA patients were more likely to have skin/soft-tissue infections than HCA-MRSA patients (83% vs 38%). Risk factors for acquisition of MRSA including intrafamilial spread, frequent antibiotic exposure, and child-care attendance were identified in 8 of the 23 (35%) CA-MRSA patients. CA-MRSA isolates were more likely to be susceptible to non-beta-lactam antibiotics than HCA-MRSA isolates. All isolates were vancomycin susceptible.

CONCLUSIONS

MRSA accounts for an increasing proportion of all pediatric S aureus infections in southern New England. A significant percentage of these cases are due to CA-MRSA. Pediatricians should have heightened suspicion for CA-MRSA in children with presumed S aureus infections, especially if they have skin/soft-tissue infections or risk factors for MRSA acquisition.

Molecular epidemiology of clinical isolates of methicillin-resistant Staphylococcus aureus in Taiwan

During July 2000 and October 2001, a total of 595 clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were collected from six medical centers distributed in northern, central, and southern Taiwan. Specimen sources included blood (n = 279), pus (n = 173), sputum (n = 94), body fluids (n = 21), catheter tips (n = 20), and urine (n = 8). Pulsed-field gel electrophoresis (PFGE) with SmaI digestion was used to fingerprint these isolates. A total of 31 genotypes with 97 type-subtypes were identified. Subtypes could be identified in 7 genotypes. While there were 6 to 15 genotypes in each hospital, 433 isolates (73%) were shown to belong to a major type (genotype A, with 29 subtypes). This genotype was not only the type prevailing in all six hospitals but also the predominant clone in each hospital, accounting for 46 to 89% of all isolates in each hospital. Genotype C (16 subtypes) was the second dominant genotype, accounting for 9% of all isolates, and was distributed in five hospitals. Genotypes D (11 subtypes), E (5 subtypes), and B (6 subtypes) were distributed in five, four, and three hospitals, respectively. The other 26 types (30 type-subtypes) were minor. We conclude that the majority of MRSA clinical isolates shared a common PFGE pattern, indicating the presence of a single, epidemic MRSA clone prevailing in major hospitals in Taiwan.

National surveillance of methicillin-sensitive and methicillin-resistant Staphylococcus aureus in Austrian hospitals: 1994-1998

In 1994, the Austrian Federal Ministry for Labour, Health and Social Affairs initiated a nationwide survey of the prevalence of methicillin-sensitive (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) in Austrian hospitals. A questionnaire had to be filled out by the medical directors of participating hospitals. During the five years of surveillance (1994-1998), a total of 9385 MRSA and 71510 MSSA episodes of infection/colonization were reported. The rate of MRSA decreased from 15.8% in 1994 to 8.2% in 1998. However, the frequency per 1000 hospital admissions increased from 0.85 to 1.29 with a maximum of 2.42 MRSA episodes per 1000 admissions in 1997. Overall, in 53.6% of 5020 S. aureus episodes, signs and symptoms of an infection were reported, of these 9.3% (251/2692) were due to MRSA. For large hospitals with more than 1000 beds, 20.9% of reported MRSA episodes were associated with infection, 54.9% of MRSA episodes from hospitals with 301-1000 beds, 60.1% from hospitals with 101-300 beds, and 80.0% from small hospitals with less than 100 beds. Our data do not support the hypothesis of higher virulence of MRSA compared with MSSA. Indeed, in this survey, MSSA episodes were more frequently associated with signs and symptoms of infection (OR=1.35, 95% CI: 1.12-1.62, P<0.001).

Significance of methicillin-resistant Staphylococcus aureus (MRSA) survey in a university teaching hospital

We experienced a methicillin-resistant Staphylococcus aureus (MRSA) outbreak in two wards at our medical school teaching hospital during the period of July-September 1997. To determine whether these MRSA clinical isolates were associated with environmental factors, we conducted two sequential MRSA surveys of the hospital staff and surroundings in wards with outbreaks (wards 1 and 2) and in one ward without an outbreak (ward 3) in April 1998 (ward 1 only) and in March 1999 (wards 1, 2, and 3). In the two sequential surveys, MRSA strains were detected mainly from white coats. MRSA strains isolated from fingers in the first survey were decreased in the second survey. The pulsed-field gel electrophoresis (PFGE) patterns of the strains isolated in the two surveys were classified into five types (A-E). Type D, including the outbreak pattern of the MRSA in ward 1 in 1997, was reduced between the first and second surveys by managing microbiological hygiene, suggesting that the outbreak was controlled in ward 1. On the other hand, the strains isolated in the second survey in ward 2 were mainly type E, which was also common among clinical isolates from ward 2 during the latter half of 1998 to 1999. This suggested a high probability of cross-infection between the patients and the hospital staff in the ward. Our observations suggest that doctors and nurses should be cautious that their coats might be contaminated with the prevailing strains of MRSA. We also concluded that the surveys were very useful for the successful management of MRSA infections.

The changing epidemiology of vancomycin-resistant enterococci

OBJECTIVE

To determine the distribution of vancomycin-resistant enterococci (VRE) cases in our hospital and those from outside of our hospital from 1993 through 1998.

METHODS

Weekly rectal surveillance was instituted whenever there were two or more cases present in the units. Cases were divided into acquired in our hospital, acquired outside of our hospital (VRE positive after and within 72 hours of admission, respectively), and indeterminate. Hospital cases were attributed to the originating ward or intensive care unit (ICU) if patients were noted to be positive within 72 hours of transfer.

RESULTS

From 1993 to 1998, the rate of VRE per 1,000 admissions increased threefold, from 3.2 to 9.8, for the hospital. VRE cases acquired outside of the hospital increased by approximately 5% per year (r = 0.87; P = .03). The rate of VRE per 1,000 admissions increased 1.7-fold in the ICUs and 3.6-fold in the wards. The ICUs had an average of 75.3 cases per year, with the number of new cases per year increasing by approximately 9 (r = 0.80; P = .028). In the wards, there were an average of 22.0 new cases per year, with a slight upward trend of 3 additional new cases per year (r = 0.69; P = .64). There was a highly significant increasing linear trend (P = .0007) for VRE colonization and infection.

CONCLUSION

Although VRE still predominate in the ICUs, cases originating from outside of our hospital and the wards are becoming more common. VRE colonization remained more frequent than infection.

Community-acquired methicillin-resistant Staphylococcus aureus colonization in healthy children attending an outpatient pediatric clinic

BACKGROUND

We previously showed that children attending an inner city pediatric emergency department were sometimes asymptomatically colonized with clindamycin-susceptible community-acquired methicillin-resistant Staphylococcus aureus (MRSA) and borderline methicillin-resistant S. aureus (BRSA) as well. We wished to ascertain whether healthy children attending an outpatient clinic were colonized with these organisms. Therefore to estimate the prevalence of community-acquired MRSA and BRSA nasal colonization in a well child population, we cultured children attending an inner city pediatric outpatient clinic.

STUDY DESIGN

This was a prospective cross-sectional study conducted from January to August, 1999, at a primary care outpatient facility at the University of Chicago. The target population was 500 healthy children < or = 16 years of age who attended this facility to receive well child care.

RESULTS

One hundred twenty-two (24.4%) children were colonized with S. aureus. Three of the 122 (2.5%) S. aureus isolates were MRSA; they came from children who lacked predisposing risk factors and were susceptible to clindamycin, gentamicin, trimethoprim-sulfamethoxazole, rifampin and ciprofloxacin. Two (1.6%) additional S. aureus isolates were BRSA; both children had predisposing risk factors for MRSA colonization. The mecA gene was present in the 3 MRSA isolates and absent in both BRSA isolates.

CONCLUSIONS

These data document that a reservoir of asymptomatic MRSA colonization exists among healthy children who lack traditional risk factors for MRSA infections.

Current trends in community-acquired methicillin-resistant Staphylococcus aureus at a tertiary care pediatric facility

BACKGROUND

The prevalence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections increased at the University of Chicago Children's Hospital (UCCH) from 10 per 100,000 admissions from 1988 to 1990 to 259 per 100,000 admissions from 1993 to 1995. Because this increase may have represented a one time occurrence or a limited disease outbreak, we updated our previous observations at UCCH in 1998 and 1999 to see whether this trend had continued.

DESIGN

Prospective observational study.

RESULTS

Twenty-three hospitalized children had an MRSA isolate during the 1-year study period. Ten were community-acquired, equally distributed between children with predisposing risk factors and those without. The overall prevalence of community-acquired MRSA was 208 per 100,000 admissions. Seven of the 10 community-acquired MRSA isolates were susceptible to clindamycin. Skin and soft tissue infections predominated among the children with a community-acquired MRSA isolate. Pulsed field gel electrophoresis of the 10 community-acquired MRSA isolates revealed 8 distinct patterns; these data suggest that multiple clones were circulating at UCCH.

CONCLUSION

MRSA are no longer confined to children with established risk factors. The prevalence of community-acquired MRSA among children without identified risk factors is high in our institution.

Antimicrobial susceptibility patterns of bacteria at the Makassed General Hospital in Lebanon

Bacterial resistance to various antimicrobial agents is most common in areas with high usage of antibiotics such as in countries where over-the-counter availability promotes usage. In Lebanon, information about bacterial resistance to antimicrobial agents is limited. In this study, data on the antimicrobial susceptibility patterns have been collected for the last 7 years in addition to the first 6 months of 1996 at the Makassed General Hospital in Lebanon. Enterobacteriaceae and Pseudomonas species proved to have high but variable rates of multidrug resistance. Among Staphylococcus aureus isolates, 17% were resistant to methicillin. A high percentage of resistance to penicillin (76-88%) was noted among Streptococcus pneumoniae. These resistance patterns were generally comparable with those of other medical centres.

Epidemiological and biological characteristics of methicillin-resistant staphylococcal infections in a Mexican hospital

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has spread worldwide since 1960. However, there is little information concerning methicillin-resistant coagulase-negative staphylococci (MRCNS) infections.

METHODS

In order to study the clinical and epidemiological characteristics of methicillin-resistant staphylococci (MRS) infections and to determine the relationship between MRS and both synergistic hemolysis (SH) and slime production (SP), a laboratory-based survey and non-matched case-control study were carried out at a tertiary-care center in Mexico City. In regard to patients, from May 1991 to October 1992, 46 cases of MRS infection and 86 patients (controls) infected by methicillin-susceptible staphylococci (MSS) were included. Clinical and epidemiologic variables were analyzed. The isolates were identified and tested for antimicrobial susceptibility by standard methods. An MIC of oxacillin > or = 8 micrograms/mL was defined as an MRS.

RESULTS

During the study, 94 nosocomial staphylococcal infections were diagnosed: S. aureus, 35 and CNS, 59; 43 (45.7%) by MRS (rate of MRS infections was 1.12 per 100 in-patients); 2 MRSA; 41 MRCNS, and only 19 were symptomatic. Three infections were community-acquired, including one MRSA and two MRCNS. After multivariate analysis, the significant risk factors were previous antimicrobial therapy (p = 0.013) and catheter-related (p = 0.009) and urinary-tract source (p = 0.0001). Forty-nine percent of MRS showed SH while only 15% of MSS (p < 0.001) showed SH, especially in 10/10 MR-S. hemolyticus. Additionally, 48% of MRCNS showed SP, as did 18% of MSCNS (p = 0.019), particularly in 15/20 MR-S. epidermidis. Of all MRS isolates, 38% showed a homogeneous phenotype, a trait associated with multi-drug resistance (p < 0.01) and SH (p < 0.001).

CONCLUSIONS

CNS predominated as the cause of MRS infections in our setting. The homogenous phenotype was associated with SH and multi-drug resistance.

In vitro susceptibility of Staphylococcus aureus isolated from blood to currently used antistaphylococcal drugs

Changes in antibiotic susceptibility was evaluated in 77 consecutive nosocomial clinical isolates of Staphylococcus aureus collected from 1986 to 1994 at the Umberto I Polyclinic of the University of Rome (63 isolates) and from 7 other Roman hospitals (14 isolates). Oxacillin resistance in these isolates increased from 39% during the 1980s to 69% during the 1990s. Significant increases in resistance to ciprofloxacin, clindamycin and rifampicin were observed among oxacillin-resistant strains. No resistance to glycopeptides was observed although both teicoplanin and vancomycin had slightly reduced antistaphylococcal activity.

Methicillin-resistant Staphylococcus aureus: a questionnaire and microbiological survey of nursing and residential homes in Barking, Havering and Brentwood

The study determined the policies and procedures for the control and prevention of methicillin-resistant Staphylococcus aureus (MRSA) and its prevalence among nursing and residential homes, and evaluated whether certain home characteristics such as bed size, staffing level, and type of home are related to the prevalence of MRSA. A 21-questionnaire survey, with primarily categorical responses, was mailed to the home managers of all the 121 nursing and residential homes in the district, following which a simple, stratified random sample of 28 (23.14%) homes was taken and all agreeing residents screened from multiple sites for MRSA. Seventy-seven (63.6%) homes returned a completed questionnaire, 13 (46.4%) of whom agreed to participate in the microbiological study. The response rates for returning questionnaires and agreeing to participate in the microbiological study were similar for nursing and residential homes (65% vs. 60%; 67% vs. 40%; P = 0.12; P = 0.62), respectively. Nursing homes had a mean bed size of 30 (95% Confidence Interval (CI) 17-43), not significantly different from residential homes of 23 (95% CI 18-27; P = 0.26). The nursing homes employed a mean of 8.6 (95% CI 4.7-12.5) staff nurses per home; significantly higher than residential homes with a mean of 1.6 (95% CI 0.3-2.8; P = 0.006). No significant differences in mean number of home care assistants employed per home (22.8; 95% CI 12.4-33.13; and 14.4; 95% CI 11.83-16.90; P = 0.098, for nursing and residential homes, respectively) were observed. None of the homes had employed infection control practitioners. Only four (6.8%) of the responding homes stated that MRSA was a problem. Nursing homes were not significantly more likely to have admission policies for colonized person than residential homes (10/13 vs. 40/55, P = 1.00). Of the fifty-five (71.4%) homes who had admission policies, 40 (72.7%) stated that persons colonized/infected with MRSA would not be accepted, while 12 (21.8%) would accept such persons in single-room isolation and/or barrier nursing. Greater proportions of residential homes than nursing homes would not accept admission of persons with documented MRSA colonization (30/35 vs. 4/10, P = 0.007). Four (9.1%) homes (three nursing) had identified a total of five residents colonized/infected with MRSA in 5 years prior to the survey. Two hundred and forty-six residents were screened (552 sites), two (0.81%) of whom were found to be colonized in the nose (one resident) and in the groin (two residents) with MRSA, giving a 2-month weighted point prevalence rate of 0.14% (95% CI 0.01-0.26%). We conclude that in our district the nursing staffing levels and control measures vary widely within these homes, while the prevalence of residents who are colonized/infected with MRSA is lower than in other areas. We suggest that the exclusion admission policy for MRSA positive patients should be abandoned and targeted infection control programmes be instituted.

Combined use of ribotyping, PFGE typing and IS431 typing in the discrimination of nosocomial strains of methicillin-resistant Staphylococcus aureus

We have previously reported the phenotypic characterization of methicillin-resistant Staphylococcus aureus (MRSA) clinical strains isolated in Malaya University Hospital in the period 1987 to 1989 using antibiogram, coagulase typing, plasmid profiles, and phage typing. Here, we report the analysis of the same strains with three genotyping methods; ribotyping, pulsed-field gel electrophoresis (PFGE) typing, and IS431 typing (a restriction enzyme fragment length polymorphism analysis using an IS431 probe). Ribotyping could discriminate 46 clinical MRSA strains into 5 ribotypes, PFGE typing into 22 types, and IS431 typing into 15 types. Since the differences of the three genotyping patterns from strain to strain were quite independent from one another, the combined use of the three genotyping methods could discriminate 46 strains into 39 genotypes. Thus, the powerful discriminatory ability of the combination was demonstrated.

Effective control of methicillin-resistant Staphylococcus aureus in a burn unit

Methicillin-resistant Staph, aureus (MRSA) colonization and infection was studied in 231 patients who were admitted to our burn unit and remained for 3 days or more between 1986 and 1994 (patients with inhalation injury only and no burn wound were excluded). The study was divided into two periods: from 1988 to 1989 and from 1990 to 1994. MRSA was found in 80 patients. They increased from 1986 to 1988, slightly decreasing thereafter. In 1994 the incidence of MRSA was 4.3 per cent. The number of strains of MRSA isolated from burn wounds was significantly reduced in the later period. Comparing the two periods, isolation of patients from MRSA, prevention of contamination during care, and reduction in the number of patients initially given second- or third-generation cephem antibiotics were performed more strictly in the later period. The effectiveness of these measures was confirmed. Moreover, the first operation was carried out significantly earlier in the later period. Early excision and early closure of the wound was more effective in preventing and controlling MRSA colonization and infection.

Unusual development of granulomas on the healing surface of burn wounds associated with MRSA infections

Ten patients with a mean age of 14.5 years and partial skin thickness burns involving 3-5 per cent body surface areas developed rapidly proliferating tumour-like growths on the surface of their healing wounds within 10-21 days of sustaining the injuries. The number of tumours on every patient was either single or multiple and each increased in size daily. The growths were unique in their fulminating-type fleshy mass, with a consistency varying from soft to firm, absence of purulent material or head, and extension up to the fibrous layer covering the musculatuve. Histopathology was suggestive of granulomatous rather than a suppurative nature of the lesions. Isolation of MRSA from the burn wounds of four cases on the first day of dressing and then from the surface of the tumours of all of them and the excised tissues, as well as from the environment of the dressing room, indicated its involvement in the causation of the growths through contaminations of wounds with a hospital endemic strain while handling or dressing. The organisms were resistant to most antibiotics except vancomycin and teicoplanin. The growths in four cases subsided within 72 h with daily dressing, using an injectable solution of either vancomycin or teicoplanin, while the rest required radical excision and immediate cover with split skin grafts and systemic administration of either of the antibiotics. The wounds healed over a period of 8-10 days.

Use of 0.3% triclosan (Bacti-Stat) to eradicate an outbreak of methicillin-resistant Staphylococcus aureus in a neonatal nursery

BACKGROUND

Once established in an institution, methicillin-resistant Staphylococcus aureus (MRSA) outbreaks have proved difficult to eradicate, despite intensive infection control measures. This report describes the nosocomial infection with MRSA of 22 male infants in a neonatal nursery during a 7-month period and the infection control procedures that effectively brought this outbreak under control and eliminated recurrence for more than 3 1/2 years.

METHODS

After a single index case of bullous impetigo caused by MRSA in a neonate discharged from the nursery 2 weeks previously, an additional 18 cases of MRSA skin infections were clustered in a 7-week period. Aggressive infection control measures were instituted, including changes in umbilical cord care, circumcision procedures, diapers, handwashing, gloves, gowns, linens, disinfection, placement in cohorts of neonates and staff, surveillance, and monitoring.

RESULTS

These measures were not effective in slowing the outbreak. The single additional measure of changing handwashing and bathing soap to a preparation containing 0.3% triclosan (Bacti-Stat) was associated with the immediate termination of the acute phase of the MRSA outbreak.

CONCLUSION

The nursery has remained free of MRSA for more than 3 1/2 years, attesting to the success of our program.

Nasal carriage of Staphylococcus aureus and cross-contamination in a surgical intensive care unit: efficacy of mupirocin ointment

A six month prospective study was carried out in a surgical intensive care unit (SICU) of a university hospital to assess the incidence and routes of exogenous colonization by Staphylococcus aureus. A total of 157 patients were included in the study. One thousand one hundred and eleven specimens (nasal, surgical wound swabs, tracheal secretions obtained on admission and once a week thereafter, and all clinical specimens) were collected over a four month period from patients without nasal decontamination (A). They were compared with 729 specimens collected over a two month period from patients treated with nasal mupirocin ointment (B). All S. aureus strains were typed by restriction fragment length polymorphism (RFLP) pulsed-field gel electrophoresis after SmaI macrorestriction. The nasal colonization rates on admission were 25.5 and 32.7% in groups A and B, respectively. Thirty-one untreated patients (31.3%) and three patients (5.1%) treated with nasal ointment, acquired the nasal S. aureus in the SICU (P = 0.00027). Nasal carriers were more frequently colonized in the bronchopulmonary tract (Bp) and surgical wound (Sw) (62%) than patients who were not nasal carriers (14%) (P < 0.00001). The patterns were identical for nasal, Bp and Sw strains from the same patient. RFLP analysis characterized seven epidemic strains of methicillin-resistant S. aureus (MRSA) which colonized 60% of group A and 9% of group B patients (P < 0.00001). The bronchopulmonary tract infection rate was reduced in group B (P = 0.032). In conclusion, in an SICU, nasal carriage of S. aureus appeared to be the source of endogenous and cross-colonization. The use of nasal mupirocin ointment reduced the incidence of Bp and Sw colonization, as well as the MRSA infection rate.

Synthesis and biological properties of a series of optically active 2-oxaisocephems

A novel series of (6S, 7S)-3,7-disubstituted-8-oxo-1-aza-4-oxabicyclo[4.2.0]oct-2-ene-2- carboxylic acids 9a-o, parenteral optically active 2-oxaisocephems, was synthesized, and in vitro and in vivo activities were determined against Gram-positive and Gram-negative bacteria. The 7-[2-(2-aminothiazol-4-yl)-2-(Z)-cyclopentyloxyimino]acet arnido derivatives, 9g, 9m and 9o, had enhanced antibacterial activity against Gram-positive organisms including methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecalis while maintaining Gram-negative activity. It is also significant that these compounds showed more potent activity against MRSA and E. faecalis isolates than cefuzonam (10) and flomoxef (12), which are the most popular third-generation antibiotics. The combination of the 7-[2-(aminothiazol-4-yl)-2-(Z)-cyclopentyloxyimino]acetamido group and 2-oxaisocephem nucleus contributes to the increased antibacterial activity against these clinical isolates. The 7-[2-(2-aminothiazol-4-yl)-2-(Z)-cyclopentyloxyimino]acet ami do derivative 9g provided good subcutaneous efficacy and exhibited more potent activity than cefmenoxime (11) against the systemic infection with S. aureus Smith in mice. The compound 9a with a [2-(2-aminothiazol-4-yl)-2-(Z)-methoxyimino]acetamido group at the 7-position showed high in vivo efficacy on the experimental infection caused by Escherichia coli No. 29 in mice.

Methicillin-resistant Staphylococcus aureus in tertiary care institutions on the Canadian prairies 1990-1992

OBJECTIVE

To review experience with methicillin-resistant Staphylococcus aureus (MRSA) in tertiary acute-care teaching hospitals on the Canadian prairies.

DESIGN

Retrospective review for a 36-month period, 1990 through 1992.

SETTING

Five tertiary acute-care teaching hospitals in three Canadian prairie provinces.

METHODS

MRSA isolates and susceptibility were identified through the clinical microbiology laboratory at each institution. For each patient, data collected included duration of institutional residence prior to isolation, patient ethnic background, age, sex, and antimicrobial susceptibility. Epidemiologic typing of strains used restriction fragment length polymorphism analysis by pulsed-field gel electrophoresis.

RESULTS

Two hundred fifty-nine MRSA isolates were identified in 135 patients during the 36 months, with substantial institutional variation in number of isolates. No consistent increase in yearly numbers of isolates was apparent. Patients usually had MRSA identified at admission (62%); only one of five centers had the majority of isolates acquired nosocomially. Patients with MRSA present at admission were more frequently of aboriginal (First Nations) ethnicity (62% compared with 14% of nosocomial; P < 0.001). Pulsed-field gel electrophoresis of 167 isolates from 135 patients revealed 46 different strains with little interprovincial or interinstitutional identity of strains.

CONCLUSIONS

MRSA isolated in patients in tertiary care institutions in these three Canadian provinces usually is acquired prior to admission. A disproportionate number of isolates are identified in aboriginal Canadians. Epidemiologic typing was consistent with a polyclonal origin of MRSA in this geographic area.

Molecular epidemiology for local outbreaks of methicillin resistant Staphylococcus aureus (MRSA). The need for several methods

Subtyping isolates may be useful for epidemiological studies of methicillin-resistant-Staphylococcus aureus (MRSA) outbreaks. Among subtyping methods, DNA-based techniques have been applied very effectively for this purpose. An outbreak of MRSA infections took place in one hospital in Barcelona early during 1991. From the beginning of the outbreak to December 92, 70 MRSA isolates from different patients and sources were collected. All strains were evaluated by restriction endonuclease analysis of plasmid DNA (REAP) and macrorestriction endonuclease analysis of genomic DNA using Sma I and pulsed-field-gel-electrophoresis (PFGE). Plasmid screening and REAP using Hind III demonstrated two plasmid subtypes: subtype A showing a large plasmid, and subtype B showing the same large plasmid plus a smaller one. Subtypes A and B corresponded to the more recent and older isolates, respectively, suggesting the loss of the small plasmid during the epidemic. PFGE using Sma I displayed two closely related profiles (PFGE subtype A and A'; CS = 0.90). These subtypes were different from those subtypes exhibited from 4 methicillin-susceptible-Staphylococcus aureus (MSSA) isolates from the same hospital and from 2 epidemiologically unrelated MRSA isolates. Almost all isolates showing PFGE subtype A preceded those isolates showing PFGE subtype A'. This fact and the similarity between both subtypes suggested minor chromosomal DNA rearrangement during the outbreak from a unique strain. While PFGE using Sma I is a useful tool in evaluation of clonal dissemination, our data suggest epidemic or local outbreaks may need several methods to best delineate the source and spread of MRSA strains. The reproducibility and discriminatory power of REAP makes it a useful adjunct in this context.

Rapid and sensitive high-performance liquid chromatographic assay for novobiocin in human serum

In this paper we present a new HPLC method for the determination of novobiocin in human serum. The assay uses mitomycin C as an internal standard, protein precipitation with acetonitrile, an ODS reversed-phase column with an isocratic mobile phase of acetonitrile-0.01 M phosphoric acid (80:20, v/v), and UV detection at 340 nm. The assay has a lower limit of quantitation of 1 microgram/ml and is linear over the range of 1-1000 micrograms/ml. The assay is ideally suited for use in clinical trials as it requires minimal amounts of serum, is highly sensitive and reproducible, is performed with minimal sample preparation, and involves a short run time. It should prove important in evaluating the potential of novobiocin as a means to modulate resistance to antineoplastic chemotherapy and in therapeutic drug monitoring of the growing number of patients receiving novobiocin to control methicillin-resistant Staphylococcus aureus infections.

High rate of oxacillin-resistant Staphylococcus aureus isolates in an Italian University Hospital

We reviewed our routine clinical laboratory records from January 1990 to March 1993 to evaluate the rate of oxacillin-resistance among nosocomial isolates of Staphylococcus aureus. Of 265 clinically significant isolates, 174 (65%) were oxacillin-resistant S. aureus (ORSA). Most of these strains were obtained from surgery patients and/or were isolated from surgical wounds. The isolations of S. aureus increased during the study period: 45 in 1990, 50 in 1991, 130 in 1992 and 40 in the first trimester of 1993. The annual rates of ORSA among S. aureus isolated varied from 62 to 68% through these years. Most ORSA isolates proved resistant to ciprofloxacin, gentamicin and rifampicin, and susceptible to vancomycin, netilmicin and cotrimoxazole. Based on these results, the need for a stringent application of infection control measures is outlined.

Prospective study of infection, colonization and carriage of methicillin-resistant Staphylococcus aureus in an outbreak affecting 990 patients

In the three years between November 1989 and October 1992, an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) affected 990 patients at a university hospital. The distribution of patients with carriage, colonization or infection was investigated prospectively. Nosocomial acquisition was confirmed in at least 928 patients, 525 of whom were identified from clinical specimens as being infected (n = 418) or colonized (n = 107) by MRSA. An additional 403 patients were identified from screening specimens, of whom 58 subsequently became infected and 18 colonized. Screening of the nose, throat and perineum detected 98% of all carriers. Of the 580 infections in 476 patients, surgical wound, urinary tract and skin infections accounted for 58% of the infections. Of the 476 infected patients, death was attributable to MRSA infection in 13%. Colonization with MRSA was found in 127 patients and 42% of 165 colonized sites were the skin. Auto-infection from nasal carriage or cross-infection, probably via staff hands, seemed to be the most common mode of acquisition of MRSA infections.