Methicillin-resistant Staphylococcus aureus in the community: new battlefronts, or are the battles lost?

Antibacterial screening of plants used in Iranian folkloric medicine

Fifty methanolic plant extracts belonging to 44 plant species of 33 families finding use in Iranian folkloric medicine were screened for antibacterial activity. Thirty samples, including 28 species in 20 families, had antibacterial activity against at least on one of the bacteria. Among the active plants, 32.6% were active against G(-), 62% against G(+), and 47.3% against both G(-) and G(+) bacteria. Dianthus coryophyllus was active against all tested G(-) and G(+) bacteria except Micrococcus luteus. Most susceptible G(-) bacteria were Klebsiella pneumoniae and Bordetella bronchiseptica and least susceptible G(-) bacterium was Escherichia coli. In G(+) bacteria, most and least susceptible were Staphylococcus aureus and M. luteus, respectively. The least MIC, as 0.62 mg/ml, belonged to Myrtus communis seeds against S. aureus, Bacillus cereus and B. bronchiseptica, and to Terminalia chebula ripe seeds against S. aureus.

Community-acquired methicillin-resistant staphylococcus aureus skin infection: an emerging clinical problem

Community-acquired methicillin-resistant Staphylococcus aureus skin infections at an outpatient university health center were evaluated. In all, 41 cultures were performed in 36 of 853 patients. Of the 19 patients with S aureus infection, methicillin resistance occurred in 10 (53%) and generally manifested as abscesses or cellulitis. Therefore, methicillin resistance should be considered, even in the community setting, and appropriate cultures performed.

Methicillin-resistant Staphylococcus aureus: impact on dermatology practice

Methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) emerged in the 1960s and is now commonly seen in hospitals, clinics and, since the mid-1990s, the community. Risk factors for the acquisition of MRSA include chronic dermatoses, underlying medical illnesses, attending healthcare facilities, use of prescription antibacterials, surgery, intravenous lines, hospitalization in an intensive care unit, and proximity to patients colonized with MRSA. Recent community-associated strains often occur in patients without these risk factors. Staphylococci are readily spread from person to person and readily contaminate the environment. Infection control measures thus involve identifying the infected patients, separating them from other non-infected patients, cleaning of the environment and, most important of all, scrupulous attention to hand hygiene. Alcoholic antiseptic hand rubs offer an alternative to antiseptic hand washes and increase compliance. Treatment of MRSA skin infections is challenging. Topical agents such as mupirocin or fusidic acid can be used, but the organisms often become resistant. Systemic therapy involves non-beta-lactams. Parenteral treatment is generally with glycopeptides such as vancomycin; oral therapy is more complex. Monotherapy with quinolones, rifampin (rifampicin), and fusidic acid often results in the development of resistance and so, if any of these agents are chosen it should be in combination. There are no data on combination therapy, although rifampin-containing combinations are often chosen. Fourth-generation quinolones and linezolid are expensive but promising alternatives.

Methicillin-resistant Staphylococcus aureus (MRSA) in rehabilitation and chronic-care-facilities: what is the best strategy?

Background

The risk associated with methicillin-resistant Staphylococcus aureus (MRSA) has been decreasing for several years in intensive care departments, but is now increasing in rehabilitation and chronic-care-facilities (R-CCF). The aim of this study was to use published data and our own experience to discuss the roles of screening for MRSA carriers, the type of isolation to be implemented and the efficiency of chemical decolonization.

Discussion

Screening identifies over 90% of patients colonised with MRSA upon admission to R-CCF versus only 50% for intensive care units. Only totally dependent patients acquire MRSA. Thus, strict geographical isolation, as opposed to "social reinsertion", is clearly of no value. However, this should not lead to the abandoning of isolation, which remains essential during the administration of care. The use of chemicals to decolonize the nose and healthy skin appeared to be of some value and the application of this procedure could make technical isolation unnecessary in a non-negligible proportion of cases.

Summary

Given the increase in morbidity associated with MRSA observed in numerous hospitals, the emergence of a community-acquired disease associated with these strains and the evolution of glycopeptide-resistant strains, the voluntary application of a strategy combining screening, technical isolation and chemical decolonization in R-CCF appears to be an urgent matter of priority.

Cost analysis of switching from IV vancomycin to PO linezolid for the management of methicillin-resistant Staphylococcus species

BACKGROUND

Infections with methicillin-resistant Staphylococcus species (MRSS) are associated with higher treatment costs than infections with methicillin-sensitive Staphylococcus species in the United States--partly because of an increased length of hospital stay (LOS).

OBJECTIVE

This study used pharmacoeconomic modeling to evaluate the costs and outcomes associated with the use of i.v. vancomycin compared with p.o. linezolid in the treatment of MRSS-infected patients.

METHODS

A retrospective chart review was used to determine the number of cases with confirmed or presumed MRSS infections treated with i.v. vancomycin during calendar-year 2000 at the Veterans Affairs Greater Los Angeles Healthcare System inpatient facility. Patients who were eligible for a switch to p.o. linezolid with or without early discharge to home were identified. Cost differences associated with conversion from i.v. to p.o. therapy (compared with continued i.v. therapy) were estimated based on a mean decreased LOS and a decrease in the costs associated with catheter-related adverse events. Rates and costs of catheter-related adverse events were based on estimates from the literature. Sensitivity analyses were performed by variation of the estimated mean LOS decrease in the SD and by variation of the estimates for incidence and costs related to catheter complications. Costs were measured in year 2000 US dollars, and differences were not assessed for statistical significance.

RESULTS

Of 177 patients treated with i.v. vancomycin, 103 (58%) were eligible for conversion to p.o. linezolid and 55 (31%) were eligible for early discharge from the hospital with continuation of p.o. therapy. Early discharge was associated with a mean (SD) LOS decrease of 3.3 (2.9) days. Annual mean total cost savings in patients eligible for conversion from i.v. vancomycin to p.o. linezolid with early discharge were $294,750 (range, $35,730-$553,790). For cases eligible for inpatient conversion from i.v. vancomycin to p.o. linezolid therapy (n=48), the mean total annual cost difference was an increase of $6340 for p.o. linezolid (range, -$12,910 to $11,900).

CONCLUSION

These results--although partly based on estimates from the literature, rather than direct measurements--support the use of p.o. linezolid with or without early discharge as a potential cost-savings alternative for eligible patients treated with a full course of i.v. vancomycin for suspected or confirmed MRSS infection.

Mupirocin-based decolonization of Staphylococcus aureus carriers in residents of 2 long-term care facilities: a randomized, double-blind, placebo-controlled trial

Mupirocin has been used in nursing homes to prevent the spread of methicillin-resistant Staphylococcus aureus (MRSA), despite the lack of controlled trials. In this double-blind, randomized study, the efficacy of intranasal mupirocin ointment versus that of placebo in reducing colonization and preventing infection was assessed among persistent carriers of S. aureus. Twice-daily treatment was given for 2 weeks, with a follow-up period of 6 months. Staphylococcal colonization rates were similar between residents at the Ann Arbor Veterans Affairs (VA) Extended Care Center, Michigan (33%), and residents at a community-based long-term care facility in Ann Arbor (36%), although those at the VA Center carried MRSA more often (58% vs. 35%; P=.017). After treatment, mupirocin had eradicated colonization in 93% of residents, whereas 85% of residents who received placebo remained colonized (P<.001). At day 90 after study entry, 61% of the residents in the mupirocin group remained decolonized. Four patients did not respond to mupirocin therapy; 3 of the 4 had mupirocin-resistant S. aureus strains. Thirteen (86%) of 14 residents who became recolonized had the same pretherapy strain; no strain recovered during relapse was resistant to mupirocin. A trend toward reduction in infections was seen with mupirocin treatment.

Role of healthcare workers in outbreaks of methicillin-resistant Staphylococcus aureus: a 10-year evaluation from a Dutch university hospital

BACKGROUND AND OBJECTIVE

The benefit of screening healthcare workers (HCWs) at risk for methicillin-resistant Staphylococcus aureus (MRSA) carriage and furloughing MRSA-positive HCWs to prevent spread to patients is controversial. We evaluated our MRSA program for HCWs between 1992 and 2002.

SETTING

A university medical center in The Netherlands, where methicillin resistance has been kept below 0.5% of all nosocomial S. aureus infections using active surveillance cultures and isolation of colonized patients.

DESIGN

HCWs caring for MRSA-positive patients or patients in foreign hospitals were screened for MRSA. MRSA-positive HCWs had additional cultures, temporary exclusion from patient-related work, assessment of risk factors for persisting carriage, decolonization therapy with mupirocin intranasally and chlorhexidine baths for skin and hair, and follow-up cultures.

RESULTS

Fifty-nine HCWs were colonized with MRSA. Seven of 840 screened employees contracted MRSA in foreign hospitals; 36 acquired MRSA after contact with MRSA-positive patients despite isolation precautions (attack rate per outbreak varied from less than 1% to 15%). Our hospital experienced 17 MRSA outbreaks, including 13 episodes in which HCWs were involved. HCWs were index cases of at least 4 outbreaks. In 8 outbreaks, HCWs acquired MRSA after caring for MRSA-positive patients despite isolation precautions.

CONCLUSION

Postexposure screening of HCWs allowed early detection of MRSA carriage and prevention of subsequent transmission to patients. Where the MRSA prevalence is higher, the role of HCWs may be greater. In such settings, an adapted version of our program could help prevent dissemination.

Community-acquired methicillin-resistant Staphylococcus aureus infection in Singapore is usually "healthcare associated"

OBJECTIVE

To assess the frequency of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections.

SETTING

A teaching hospital in Singapore.

METHODS

Prospectively collected surveillance data were reviewed during a 1-year period to determine the extent and origin of community-acquired MRSA infections.

RESULTS

Whereas 32% of 383 MRSA infections were detected less than 48 hours after hospital admission and would, by convention, be classified as "community acquired," all but one of these were among patients who had been exposed to outpatient centers including dialysis or chemotherapy clinics, visiting nurses, community hospitals, or all three.

CONCLUSIONS

With health care increasingly being delivered in an outpatient setting, community-acquired MRSA infections are often acquired in hospital-related sites and most may be more accurately described as "healthcare acquired." Infection control measures need to move beyond the traditional paradigm of acute care hospitals to effectively control the spread of resistant pathogens.

Routine use of systemic antibiotics must stop

Much has been written in recent years about the gross overuse of both topical and systemic antibiotics and the problems of bacterial resistance (Weinstein, 2001; Livermore et al, 2002). This has led to the re-emergence of untreatable infectious diseases, such as tuberculosis, which we had thought consigned to medical history. The problems have not been restricted to hospitals and nosocomial infections; community methicillin-resistant Staphylococcus aureus (MRSA) and cross-infection have been described (Cookson, 2000). The situation has been termed a ‘crisis’ in the USA (Colsky et al, 1998), and this is reflected in the UK (House of Lords, 1998).

The sensitivity to honey of Gram-positive cocci of clinical significance isolated from wounds

AIMS

To determine the sensitivity to honey of Gram-positive cocci of clinical significance in wounds and demonstrate that inhibition is not exclusively due to osmotic effects.

METHODS AND RESULTS

Eighteen strains of methicillin-resistant Staphylococcus aureus and seven strains of vancomycin-sensitive enterococci were isolated from infected wounds and 20 strains of vancomycin-resistant enterococci were isolated from hospital environmental surfaces. Using an agar incorporation technique to determine the minimum inhibitory concentration (MIC), their sensitivity to two natural honeys of median levels of antibacterial activity was established and compared with an artificial honey solution. For all of the strains tested, the MIC values against manuka and pasture honey were below 10% (v/v), but concentrations of artificial honey at least three times higher were required to achieve equivalent inhibition in vitro. Comparison of the MIC values of antibiotic-sensitive strains with their respective antibiotic-resistant strains demonstrated no marked differences in their susceptibilities to honey.

CONCLUSIONS

The inhibition of bacteria by honey is not exclusively due to osmolarity. For the Gram-positive cocci tested, antibiotic-sensitive and -resistant strains showed similar sensitivity to honey.

SIGNIFICANCE AND IMPACT OF THE STUDY

A possible role for honey in the treatment of wounds colonized by antibiotic-resistant bacteria is indicated.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in nursing homes: a cross-sectional study

A cross-sectional study of methicillin-resistant Staphylococcus aureus carriage in 2,857 nursing home residents showed an overall prevalence of 4.9%. The three clones identified by genetic analysis were identical to those in the acute care facilities; only their relative prevalence differed. Clone 2 took epidemic proportions in five of these nursing homes.

[Evaluation of the efficacy of a multiresistant bacteria control programme in a teaching hospital, studying the evolution of methicillin-resistant Staphylococcus aureus incidence]

Methicillin-resistant Staphylococcus aureus (MRSA) constitute the most important multiresistant bacteria (MRB) recovered in French hospitals. Our objective was to measure these MRSA diffusion in our hospital to evaluate the MRB control programme which had been implemented in the beginning of 1999. This study was conducted in a teaching hospital containing 1800 beds, from February 1999 to January 2001. All MRSA isolated in clinical samples were included. Duplicates (same bacteria in the same patient) were excluded. The detection of methicillin-resistance was performed at 30 degrees C, by disk diffusion method. Incidence densities were determined with their 95% confidence interval (CI 95%). Their evolution by four-month period was evaluated with the chi-square test for trend. During the two-year period, 866 MRSA were isolated. The global incidence was 0,88 per 1000 patient-days (PD) (IC 95% = left open bracket 0,83-0,93 right open bracket ). For cases acquired in our hospital the incidence was 0,66 per 1000 PD, whereas it was 0,26 per 1000 PD for imported cases. Concerning the evolution of incidences, no significant trend was observed for global incidence. The incidence of acquired MRSA decreased during the first year, but increased thereafter. The incidence of imported MRSA increased with a significant trend (p < 10(-5)). The number of these imported MRSA isolated in our hospital was twice fold higher in 2000. This study emphasizes an important actual problem : the increase of patient colonization pressure at the time of admission in hospitals. This increase, which can be due in part to a community transmission, is responsible for a reduction of the efficacy of MRSA control programmes.

Surveillance of methicillin-resistant Staphylococcus aureus (MRSA) and Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBLE) in Northern France: a five-year multicentre incidence study

In order to measure the incidence of methicillin-resistant Staphylococcus aureus (MRSA) and of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBLE), and to evaluate the impact of the national guidelines for multidrug-resistant bacteria (MDRB) prevention in hospitals of Northern France, a multicentre study was conducted for three months every year starting in 1996, in volunteer hospital laboratories. All clinical specimens positive for MRSA and ESBLE were prospectively surveyed. During the five-year surveillance period, the overall proportion of MRSA was 38.4% in the 28,534 strains of S. aureus, and that of ESBLE was 11.4% in the 6121 strains of Klebsiella pneumoniae and 47.7% in the 2353 strains of Enterobacter aerogenes. The overall incidence rates of clinical specimens positive for MRSA, ESBL-K. pneumoniae and E. aerogenes were 0.84. 0.05 and 0.12/1000 hospital-days (HD), respectively. In the 23 hospitals that participated in the survey every year, the proportion and incidence of ESBLE decreased. Hence, despite recommendations as for isolation precautions, MRSA remains poorly controlled and requires more effective measures.

Molecular epidemiological studies of Staphylococcus aureus in urinary tract infection

In recent years, the increasing incidence of urinary tract infection (UTIs) caused by Staphylococcus aureus has been noted at the urology ward, Okayama University Hospital. We investigated the molecular epidemiological characteristics of 139 UTI isolates, including 45 methicillin-sensitive S. aureus (MSSA) and 94 methicillin-resistant S. aureus (MRSA), collected over a 10-year period from 1990 to 1999. The antibiotic resistance genes ( mecA, aph(3')-III, aac(6')-aph(2"), ant(4')-I) and the toxin genes (tst, sea, seb, and sec) were detected by using multiplex polymerase chain reaction (PCR). Since 1996, the prevalence of the ant(4')-I, tstand secgenes has increased markedly in coagulase type II S. aureus possessing the mecA gene (MRSA). The presence of toxin genes in MRSA was higher than that in MSSA; 66.0% and 26.7% for tst, 7.4% and 4.4% for sea, 24.5% and 8.9% for seb, and 66.0% and 28.9% for sec, respectively. In the review of medical records, it was found that febrile episodes occurred in 12 of 72 patients with monomicrobial UTI caused by S. aureus. For the febrile patients, S. aureus isolates with both the tst and sec genes were found significantly more often (11 of 12; 91.7%) than those without the tst and sec genes ( P = 0.0484). Molecular typing of MRSA isolates, by using random amplified polymorphic DNA analysis and pulsed-field gel electrophoresis analysis, revealed no apparent clonality of these isolates over the 10 years, suggesting that most of the recent MRSA infections are not due to cross-infection in the urology ward.

PEG site infections: a novel use for Actisorb Silver 220

Any breach in the integrity of the skin, such as occurs in wounds and incisions, and intravascular catheters, can act as a portal for the ingress of microorganisms and thereby predispose the patient to infection. The infection, if unchecked, can put the patient at risk of bacteraemia. We have reviewed the care of percutaneous enterostomal gastrostomy (PEG) sites in our trust hospital and in the local community and have implemented practice guidelines to reduce infection risks. These include protocols for skin care around PEG sites, and the use of an antibacterial dressing - Actisorb Silver 220 - to manage local colonization. The preliminary results of this exercise indicate that patient comfort can be improved, hypergranulation reduced, and methicillin-resistant Staphylococcus aureus colonization and infection eradicated.

Community-acquired methicillin-resistant Staphylococcus aureus, Finland

Methicillin-resistant Staphylococcus aureus (MRSA) is no longer only hospital acquired. MRSA is defined as community acquired if the MRSA-positive specimen was obtained outside hospital settings or within 2 days of hospital admission, and if it was from a person who had not been hospitalized within 2 years before the date of MRSA isolation. To estimate the proportion of community-acquired MRSA, we analyzed previous hospitalizations for all MRSA-positive persons in Finland from 1997 to 1999 by using data from the National Hospital Discharge Register. Of 526 MRSA-positive persons, 21% had community-acquired MRSA. Three MRSA strains identified by phage typing, pulsed-field gel electrophoresis, and ribotyping were associated with community acquisition. None of the strains were multiresistant, and all showed an mec hypervariable region hybridization pattern A (HVR type A). None of the epidemic multiresistant hospital strains were prevalent in nonhospitalized persons. Our population-based data suggest that community-acquired MRSA may also arise de novo, through horizontal acquisition of the mecA gene.

Low prevalence of methicillin-resistant strains among Staphylococcus aureus colonizing young and healthy members of the community in Portugal

Recent reports suggest that methicillin-resistant Staphylococcus aureus (MRSA) may be emerging as a community pathogen. In Portuguese hospitals, the incidence of MRSA among disease causing isolates is extremely high (48-50%). To determine the prevalence of MRSA in the Portuguese community, nasal samples were obtained from 823 draftees, 484 nonmedical university students, and 107 high-school students. In addition, throat samples were obtained from the 823 draftees and S. aureus isolates were also recovered from 283 (13%) nasopharyngeal samples obtained from 2,111 children attending day-care centers. The rate of nasal colonization of S. aureus was 34%, 25%, and 46% for draftees, nonmedical university students, and high-school students, respectively. The rate of pharyngeal colonization of the draftees was 33%. Of the 1,001 S. aureus isolates obtained, seven were MRSA and eight were borderline oxacillin-resistant S. aureus (BORSA). By molecular typing techniques, five of the seven MRSA were identified as belonging to one of three highly epidemic clones, the Brazilian, Iberian, and Pediatric clones of MRSA, which were identified as endemic in Portuguese hospitals. The eight BORSA were all members of clones previously identified in international samples. In spite of the extremely high prevalence of MRSA in Portuguese hospitals, the carriage rate of MRSA in healthy and young individuals remains low.

Risk factors for methicillin-resistance among patients with Staphylococcus aureus bacteremia at the time of hospital admission

BACKGROUND

Community-acquired infections caused by methicillin-resistant Staphylococcus aureus (MRSA) seem to be increasing. Characteristics permitting recognition of patients with such strains would aid infection control efforts and choice of empiric therapy pending culture and susceptibility results.

METHODS

Retrospective review of medical records for all adults seen in the Emergency Care Center at Grady Memorial Hospital, Atlanta, Georgia, whose blood cultures taken within 24 hours of entry yielded S. aureus. Risk factors for the presence of methicillin resistance in S. aureus isolates recovered from patients with staphylococcal bacteremia were assessed.

RESULTS

S. aureus isolates from 118 (40%) of 297 study patients with bacteremia at the time of admission were methicillin-resistant. Multivariate analysis identified hospitalization in the 6 months preceding admission [odds ratio (OR) = 4.4; 95% CI, 2.0-9.8], receipt of antimicrobial agents in the past 3 months (OR = 5.6; 95% CI, 2.6-11.9], presence of indwelling urinary catheter (OR = 7.3; CI, 2.5-20.9), and nursing home residence (OR = 9.9; 95% CI, 3.9-25.6) to be independently associated with the presence of methicillin resistance. All but 4 of the 118 patients with methicillin-resistant strains had at least 1 of these factors and the proportion of resistant isolates progressively increased as more of these features were present.

CONCLUSIONS

The presence of these risk factors should be considered when making decisions about isolation and other infection control procedures as well as empiric antimicrobial therapy with vancomycin for patients with suspected staphylococcal infection at the time of hospital admission. Similar studies could guide practices for dealing with such patients in other centers, because the occurrence of MRSA infections at the time of admission may vary widely by geographic area.

Antibiotic resistance patterns of bacterial isolates from blood in San Francisco County, California, 1996-1999

Countywide antibiotic resistance patterns may provide additional information from that obtained from national sampling or individual hospitals. We reviewed susceptibility patterns of selected bacterial strains isolated from blood in San Francisco County from January 1996 to March 1999. We found substantial hospital-to-hospital variability in proportional resistance to antibiotics in multiple organisms. This variability was not correlated with hospital indices such as number of intensive care unit or total beds, annual admissions, or average length of stay. We also found a significant increase in methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, and proportional resistance to multiple antipseudomonal antibiotics. We describe the utility, difficulties, and limitations of countywide surveillance.

Prevalence of methicillin-resistant Staphylococcus aureus carriage at the time of admission in two acute geriatric wards

Studies on methicillin-resistant Staphylococcus aureus (MRSA) in the elderly have been concerned with patients hospitalized in nursing homes or long-term care facilities. Our objective was to estimate the prevalence of MRSA at the time of admission in two acute geriatric wards with high endemic MRSA incidence in a French teaching hospital. A prospective screening of MRSA carriers was conducted by swabbing nares and wounds during five weeks for all patients on the day of admission. For each patient demographic, administrative, clinical and therapeutic data were recorded. Their associations with MRSA carriage were studied by logistic regression analysis. On the day of admission, 35 patients (14.6%) were MRSA carriers. Variables independently associated with carriage were hospitalization within the six last months (OR = 4.64; P < 0.001) and the existence of wounds or bedsores (OR = 2.864; P = 0.02). The high prevalence of MRSA carriage at the time of admission could explain in part the high incidence of MRSA in these wards. A systematic selective screening targeted on patients with high risk of carriage should be helpful to implement barrier precautions and reduce cross-transmission.

Staphylococcus aureus infections and antibiotic resistance in older adults

The prevalence of infection with Staphylococcus aureus among older adults is unknown, but clinical syndromes caused by this organism are common. Bacteremia, pneumonia, endocarditis, and bone and joint infections are encountered with relative frequency in this population, and the clinical presentation may be atypical. Underlying disease and functional debility, rather than age itself, predispose the older adult to staphylococcal carriage and infection. Infections with methicillin-resistant strains of S. aureus are acquired primarily in hospital, rather than in nursing homes or in the community. Lack of clinical suspicion for S. aureus infection and delays in appropriate therapy can be fatal. Staphylococcal infection should be considered for an older adult with risk factors for staphylococcal carriage, comorbid illness, debility, and history of recent hospitalization or nursing home stay. Choices regarding empirical therapy should be made on the basis of knowledge of local antibiotic susceptibility patterns.

Susceptibility testing. Phenotypic and genotypic tests for bacteria and mycobacteria

Genotypic-based methods hold promise for the rapid and accurate detection or confirmation of antimicrobial resistance; however, phenotypic methods will continue to have an advantage when resistance to the same antimicrobial agent may be caused by several different mechanisms. The diversity of genetic mechanisms may exceed the capabilities of current molecular technology. Genotypic assays have the ability to detect resistance but not susceptibility. Although resutls can be obtained rapidly, many molecular methods are labor-intensive, expensive, and lack standardization. Clinical studies will be required to validate the genotypic approach to detection of antimicrobial resistance. Molecular assays are also at risk for false-positive results because of contamination of specimens by other specimens that carry the DNA targeted for the assay, or carryover of amplified target DNA (amplicons) from a previous PCR assay during sample preparation. Detection of certain genetic resistance loci in clinical specimens must be interpreted with caution, because organisms in normal flora may also harbor the same loci. All these factors must be taken into consideration when introducing a genotypic method in the clinical laboratory. Other considerations include cost, turnaround time, and assay performance. It must be emphasized that the bedside assessment of the patient should always be considered in addition to the results of antimicrobial susceptibility tests (whether phenotypic or genotypic) so that the best outcome is assured for the patient.

Community-acquired methicillin-resistant Staphylococcus aureus infections in south Texas children

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (CAMRSA) infections have increased dramatically from 1990 to 2000.

OBJECTIVES

The objectives of this retrospective study were to report the frequency of CAMRSA isolates, to describe the spectrum of disease observed in children infected with CAMRSA and to compare the antibiotic susceptibility patterns of community-acquired and nosocomial methicillin-resistant S. aureus (MRSA) infections.

METHODS

All cases of S. aureus including MRSA infections were identified by a computer-assisted search of the Vitek system culture results from 1990 to 2000 and review of the minutes of Infection Control Committee meetings.

RESULTS

MRSA was isolated from 147 children (77 boys; 2 weeks to 17 years) from October 1, 1990, to December 31, 2000. Seven cases of CAMRSA were identified from 1990 to 1996, and 53 cases were identified from 1997 to 2000 with 35 cases occurring in 2000. Of the 128 children whose medical records were reviewed, 60 (47%) had CAMRSA infections. In 53 (88%) of these 60 children no risk factor for MRSA was identified. Soft tissue infections accounted for 48 (91%) of the 53 cases of the CAMRSA in children without known risk factors. CAMRSA isolates from children without known risk factors were more susceptible to trimethoprim-sulfamethoxazole (98% vs. 82%; P < 0.005) and clindamycin (92% vs. 57%; P < 0.001) and less susceptible to tetracycline (54% vs. 95%; P < 0.001) than were nosocomial MRSA isolates.

CONCLUSIONS

The emergence of CAMRSA as a cause of common infections may require a change in the initial selection of antibiotics to assure appropriate coverage in critically ill children.

Methicillin-resistant Staphylococcus aureus in geriatric patients: usefulness of screening in a chronic-care setting

OBJECTIVE

To evaluate the contribution of screening to the detection of cases of methicillin-resistant Staphylococcus aureus (MRSA) in a chronic-care facility.

DESIGN

Surveillance and laboratory observational study.

METHODS

During a 7-month period, we compared imported and acquired MRSA in a chronic-care center by screening patients for carriage of MRSA on admission and discharge, and by recording all cases of clinical specimens positive for MRSA.

SETTING

The study was conducted in a 120-bed chronic-care center. This center admits approximately 850 patients per year. Approximately 90% of the patients were elderly and were admitted from other hospitals.

RESULTS

Of 519 patients admitted during the study period, 129 were positive for MRSA at some point during their residence, including 60 (11.6%) with MRSA found within 48 hours of admission and 69 (13.3%; 53% of all positives) with nosocomial MRSA Of the 519 admissions, 332 (64%) were discharged, of whom 62 (19%) were positive for MRSA Of these 62, 43 (69%) acquired their MRSA during their stay in the center.

CONCLUSIONS

Our study confirms the amplification effect of chronic-care facilities on MRSA propagation. It also shows that screening for MRSA carriage in a chronic-care center facilitates the early identification of a large proportion of patients with MRSA.

Wound colonization and infection: the role of topical antimicrobials

Infection and bacterial colonization are important factors in compromised wound healing, particularly in chronic wounds. The current "best practice" for controlling these factors is still unclear. Systemic antibiotics are generally accepted as being the preferred choice for treating infection, provided that ischaemia does not interfere. However, their widespread systemic and topical use is leading to the emergence of resistant bacterial strains such as methicillin-resistant Staphylococcus aureus. Colonization of wounds presents a double problem: possible delayed healing if out of balance with the immune system; and as a source for cross-infection. Managing colonization is not yet defined in best practice. The judicious use of dressings, notably those containing certain antiseptic agents, can be valuable in infection control and in promoting healing. This review states the case for taking the antiseptic route as part of the concerted approach to local wound management and infection control.

Increasing threat of Gram-positive bacterial infections in the intensive care unit setting

The effects of resistance are being noted on an increasing scale in the intensive care unit (ICU). Around the world, new epidemiologic patterns of ICU occurrence are being observed for Gram-positive multidrug-resistant organisms. Current problems include the appearance of insusceptibility to vancomycin and other glycopeptides in Staphylococcus aureus organisms that are virulent enough to cause infection in patients with normal host defenses. In addition, multidrug-resistant organisms like methicillin-resistant S.aureus are spreading from healthcare to community settings, and community organisms like Streptococcus pneumoniae are spreading to healthcare settings. Focal persistence and subsequent worldwide spread of enterococci resistant to vancomycin and other glycopeptides and multiple-resistance mechanisms in the same organism also require attention. Strategies such as multidisciplinary management of infections, appropriate infection control measures, and surveillance of resistance patterns are necessary to address the problem of resistance. Intensivists have been prominent in research and control efforts in this field and should continue to lead future efforts.