Seeking vancomycin resistant Staphylococcus aureus among patients with vancomycin-resistant enterococci

Antimicrobial peptides: new hope in the war against multidrug resistance

The discovery of antibiotics marked a golden age in the revolution of human medicine. However, decades later, bacterial infections remain a global healthcare threat, and a return to the pre-antibiotic era seems inevitable if stringent measures are not adopted to curb the rapid emergence and spread of multidrug resistance and the indiscriminate use of antibiotics. In hospital settings, multidrug resistant (MDR) pathogens, including carbapenem-resistant Pseudomonas aeruginosa, vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and extended-spectrum β-lactamases (ESBL) bearing Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae are amongst the most problematic due to the paucity of treatment options, increased hospital stay, and exorbitant medical costs. Antimicrobial peptides (AMPs) provide an excellent potential strategy for combating these threats. Compared to empirical antibiotics, they show low tendency to select for resistance, rapid killing action, broad-spectrum activity, and extraordinary clinical efficacy against several MDR strains. Therefore, this review highlights multidrug resistance among nosocomial bacterial pathogens and its implications and reiterates the importance of AMPs as next-generation antibiotics for combating MDR superbugs.

Vancomycin resistant Staphylococcus aureus infections: A review of case updating and clinical features

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MRSA infection is a global threat to public health.

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Vancomycin is one of the first-line drugs for the treatment of MRSA infections.

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MRSA with complete resistance to vancomycin have emerged in recent years.

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The total number of VRSA isolates is updated in this paper.

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Resistance mechanisms, characteristics of VRSA infections, as well as clinical treatments are reviewed.

The infection caused by methicillin-resistant Staphylococcus aureus (MRSA) is a global threat to public health. Vancomycin remains one of the first-line drugs for the treatment of MRSA infections. However, S. aureus isolates with complete resistance to vancomycin have emerged in recent years. Vancomycin-resistant S. aureus (VRSA) is mediated by a vanA gene cluster, which is transferred from vancomycin-resistant enterococcus. Since the first VRSA isolate was recovered from Michigan, USA in 2002, 52 VRSA strains have been isolated worldwide. In this paper, we review the latest progresses in VRSA, highlighting its resistance mechanism, characteristics of VRSA infections, as well as clinical treatments.

Descriptive Epidemiology and Case-Control Study of Patients Colonized With Vancomycin-Resistant Enterococcus and Methicillin-ResistantStaphylococcus aureus

Background.

Patients colonized or infected with vancomycin-resistant enterococcus and methicillin-resistantStaphylococcus aureusmay be at risk of acquiring vancomycin-resistantS. aureusif the vanA gene is transferred from vancomycin-resistant enterococcus to methicillin-resistantS. aureus..

Objective.

Our goal was to identify risk factors for cocolonization or coinfection (CC/CI) with vancomycin-resistant enterococcus and methicillin-resistantS. aureus.

Design.

We conducted a descriptive, epidemiologic study of all patients with CC/CI identified from January 1998 to May 2003 and a nested case-control study of a cohort of patients hospitalized in the burn and wound unit.

Setting.

We conducted our study in a 813-bed tertiary care university teaching hospital.

Population.

The study population consisted of patients found to have CC/CI during the study period.

Methods.

Descriptive epidemiologic data were collected from hospital records of all patients identified as having CC/CI. A subset of patients hospitalized in the burn and wound unit were included in a case-control study.

Results.

CC/CI was detected in 71% of the patients during a single hospital stay. The burn and wound unit, which does active surveillance for both organisms, and the general medicine unit, which does not do active surveillance for either organism, cared for more than one-half of these patients. Among patients being cared for in the burn and wound unit, having exposure to 2 or more invasive devices (central venous catheters, indwelling urinary catheters, and enteral feeding tubes) and renal insufficiency were independent risk factors for CC/CI.

Conclusions.

Patients with CC/CI are the population at greatest risk for vancomycin-resistantS. aureuscolonization or infection. The number of invasive devices to which patients are exposed and, thus, possibly the patients' underlying severity of illness, as well as renal insufficiency, appear to be risk factors for CC/CI.

Systematic Review and Meta-Analysis of the Epidemiology of Vancomycin-Intermediate and Heterogeneous Vancomycin-Intermediate Staphylococcus aureus Isolates

BACKGROUND

Vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) are associated with vancomycin treatment failure, and are becoming an increasing public health problem. Therefore, we undertook this study of 91 published studies and made subgroup comparisons of hVISA/VISA incidence in different study years, locations, and types of clinical samples. We also analyzed the genetic backgrounds of these strains.

METHODS

A systematic literature review of relevant articles published in PubMed and EMBASE from January 1997 to August 2014 was conducted. We selected and assessed journal articles reporting the prevalence rates of hVISA/VISA.

RESULTS

The pooled prevalence of hVISA was 6.05% in 99,042 methicillin-resistant S. aureus (MRSA) strains and that of VISA was 3.01% in 68,792 MRSA strains. The prevalence of hVISA was 4.68% before 2006, 5.38% in 2006-2009, and 7.01% in 2010-2014. VISA prevalence was 2.05%, 2.63%, and 7.93%, respectively. In a subgroup analysis of different isolation locations, the prevalence of hVISA strains was 6.81% in Asia and 5.60% in Europe/America, and that of VISA was 3.42% and 2.75%, respectively. The frequencies of hVISA isolated from blood culture samples and from all clinical samples were 9.81% and 4.68%, respectively, and those of VISA were 2.00% and 3.07%, respectively. The most prevalent genotype was staphylococcal cassette chromosome mec (SCCmec) II, which accounted for 48.16% and 37.74% of hVISA and VISA, respectively. Sequence Type (ST) 239 was most prevalent.

CONCLUSION

The prevalence of hVISA/VISA has been increasing in recent years, but has been grossly underestimated. Its incidence is higher in Asia than in Europe/America. hVISA is isolated from blood culture samples more often than from other samples. These strains are highly prevalent in epidemic MRSA strains. This study clarifies the epidemiology of hVISA/VISA and indicates that the detection of these strains and the control of nosocomial infections must be strengthened.

Occurrence of Co-colonization or Co-Infection with Vancomycin-Resistant Enterococci and Methicillin-ResistantStaphylococcus aureusin a Medical Intensive Care Unit

Objective:

To determine the occurrence of co-colonization or co-infection with VRE and MRSA among medical patients requiring intensive care.

Design:

Prospective, single-center, observational study.

Setting:

A 19-bed medical ICU in an urban teaching hospital.

Patients:

Adult patients requiring at least 48 hours of intensive care and having at least one culture performed for microbiologie evaluation.

Results:

Eight hundred seventy-eight consecutive patients were evaluated. Of these patients, 402 (45.8%) did not have microbiologie evidence of colonization or infection with either VRE or MRSA 355 (40.4%) were colonized or infected with VRE, 38 (4.3%) were colonized or infected with MRSA, and 83 (9.5%) had co-colonization or co-infection with VRE and MRSA. Multiple logistic regression analysis demonstrated that increasing age, hospitalization during the preceding 6 months, and admission to a long-term-care facility were independently associated with colonization or infection due to VRE and co-colonization or co-infection with VRE and MRSA. The distributions of positive culture sites for VRE (stool, 86.7%; blood, 6.5%; urine, 4.8%; soft tissue or wound, 2.0%) and for MRSA (respiratory secretions, 34.1%; blood, 32.6%; urine, 17.1%; soft tissue or wound, 16.2%) were statistically different (P< .001).

Conclusions:

Co-colonization or co-infection with VRE and MRSA is common among medical patients requiring intensive care. The recent emergence of vancomycin-resistantStaphylococcus aureusand the presence of a patient population co-colonized or co-infected with VRE and MRSA support the need for aggressive infection control measures in the ICU.

Colonization with vancomycin-intermediate Staphylococcus aureus strains containing the vanA resistance gene in a tertiary-care center in north India

A nasal carriage survey for methicillin-resistant Staphylococcus aureus (MRSA) in an intensive care unit detected four strains of MRSA with reduced susceptibility to vancomycin. The vanA gene was found in two of these vancomycin-intermediate Staphylococcus aureus (VISA) strains. The absence of selective vancomycin pressure might have resulted in reduced expression of the resistant gene.

Increase of patients co-colonised or co-infected with methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecium or extended-spectrum β-lactamase-producing Enterobacteriaceae

PURPOSE

To determine the incidence of patients co-colonised or co-infected with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium or extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in four German tertiary care hospitals.

METHODS

This study was conducted at four tertiary care hospitals (all with >1,000 beds) in different geographic regions in Germany (Berlin in the east, Luebeck in the north, Freiburg in the southwest and Nuernberg in the southeast). Routine surveillance data on MRSA, vancomycin-resistant enterococci (VRE) and ESBL-producing bacteria were analysed from 2007 to 2009. Co-colonisation or co-infection was defined as a patient having positive cultures for at least two of the following resistant pathogens: MRSA, VRE faecium or different species of ESBL-producing Enterobacteriaceae within one calendar year.

RESULTS

A total of 896,822 patients were analysed, of which 10,066 patients harboured MRSA, VRE faecium and/or ESBL-producing Enterobacteriaceae, and 542 patients co-harboured at least two of those resistant pathogens. In 2009, 7.6% of the MRSA patients, 13.7% of the VRE faecium patients and even 16.1% of the ESBL-producing Enterobacteriaceae patients were co-colonised or co-infected. The incidence of patients with co-infection or co-colonisation increased steadily from 5 (2007) to 7 per 10,000 patients (2009).

CONCLUSIONS

Patients harbouring ESBL-producing Enterobacteriaceae or VRE faecium had a higher risk of being co-colonised or co-infected compared to what was to be extrapolated from their overall incidence. This might be linked to their gastrointestinal reservoir and impracticality to decolonise the gut of resistant VRE and ESBL-producing Enterobacteriaceae.

Systematic review and meta-analysis of the significance of heterogeneous vancomycin-intermediate Staphylococcus aureus isolates

The prevalence of heteroresistant vancomycin-intermediate Staphylococcus aureus (hVISA) is 1.3% in published studies. Clinical associations include high-inoculum infections and glycopeptide failure, with hVISA infections associated with a 2.37-times-greater failure rate (95% confidence interval [CI], 1.53 to 3.67) compared to vancomycin-sensitive Staphylococcus aureus (VSSA) infections. Despite this, 30-day mortality rates were similar to those for VSSA infections (odds ratio [OR], 1.18; 95% CI, 0.81 to 1.74). The optimal therapy for hVISA requires further study.

Evaluation of risk factors for coinfection or cocolonization with vancomycin-resistant enterococcus and methicillin-resistant Staphylococcus aureus

We retrospectively evaluated 410 patients with coinfection or cocolonization due to vancomycin-resistant (VR) enterococcus (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). The prevalence rate was 19.8%. Risk factors included isolation of VR Enterococcus faecalis and use of linezolid or clindamycin. Inc18-like vanA plasmids were found in 7% of VR E. faecalis isolates and none of the VR E. faecium isolates.

Vancomycin-resistant enterococcus: risk factors, surveillance, infections, and treatment

BACKGROUND

The use of vancomycin has continued to expand because of the increasing number of patients infected or colonized with methicillin-resistant Staphylococcus aureus, causing an increase in the prevalence of vancomycin-resistant Enterococcus (VRE).

METHODS

Review of the pertinent English language literature.

RESULTS

Vancomycin-resistant Enterococcus spp. are being identified more often in nosocomial infections of surgical patients. The biology of resistance, modes of transmission, patient risk factors, and current treatment strategies are discussed.

CONCLUSIONS

The reservoir of resistance in enterococci looms as a major threat for genetic transfer and the emergence of increasing numbers of vancomycin-resistant S. aureus.

Vancomycin for treatment of invasive, multi-drug resistant Staphylococcus aureus infections

Staphylococcus aureus is a bacterial pathogen responsible for a variety of serious infections and is a frequent cause of nosocomial disease. During the last 60 years, S. aureus has developed increasing in vitro resistance to virtually all antimicrobials. In contrast, vancomycin has maintained a high degree of activity in vitro against this pathogen, although slight changes with in vitro activity could vastly change clinical activity. As a result, vancomycin has become the mainstay of therapy for invasive infections due to methicillin-resistant strains. However, clinical strains of S. aureus with intermediate resistance to vancomycin were reported in 1996, followed in 2002 with reports of isolates that were fully resistant. Although many authorities believe vancomycin remains the drug of choice for most staphylococcal-resistant infections, important issues surrounding its clinical application remain. These include the need for multiple daily dosing, intravenous administration, requirements for serum concentration monitoring, increasing resistance in vitro, modest efficacy rates and (less frequently) treatment-limiting adverse effects. This review addresses these important topics.

The usefulness of endoscopic retrograde cholangiopancreatography and (99m)Tc-labeled albumin macroaggregates in diagnosing hydatid disease fistulae

Hydatid disease is an important health problem in areas where it is endemic. There are several therapeutic modalities, the most important being surgery, antibiotherapy, and percutaneous treatment. In recent years percutaneous treatment has become popular, and for this method or surgery it is sometimes lifesaving to know the relation between the biliary ducts and the cyst cavity. The aim of this study was to examine the usefulness of endoscopic retrograde cholangiopancreatography and (99m)Tc-labeled albumin macroaggregates in diagnosing hydatid disease fistulae before percutaneous or surgical treatment. A total of 72 patients diagnosed with hepatic hydatid disease via ultrasound and serologic tests were enrolled in the study. Endoscopic retrograde cholangiopancreatography was successfully performed in all patients. (99m)Tc-labeled albumin macroaggregates also were injected into cysts at a dose of 1.5-2 mCi just before the treatment. All but three patients were treated percutaneously. Scintigraphy of abdominal and thoracic areas was performed with a GE Starcam 3200 XC/T gamma camera at 30 and 120 min after Tc-labeled albumin macroaggregate injections. Endoscopic retrograde cholangiopancreatography revealed communications between biliary ducts and cyst cavities in nine patients (12.5%). However, (99m)Tc-labeled albumin macroaggregates showed not only leakage into the systemic circulation in nine patients but also into the biliary ducts in two (15.4%). In one patient, mild acute pancreatitis occurred as a complication of endoscopic retrograde cholangiopancreatography. No complications of (99m)Tc-labeled albumin macroaggregates injection were seen. Three patients were surgically treated because of clinically manifested cystobiliary fistulae. We conclude that endoscopic retrograde cholangiopancreatography is a gold standard technique for the diagnosis of communication between the biliary duct and the cyst cavity, and (99m)Tc-labeled albumin macroaggregate injection is useful for revealing leakage into the systemic circulation. The diagnosis of biliary fistulae before percutaneous treatment of hydatid disease may enable planning of the optimal therapy.

High-level vancomycin-resistant Staphylococcus aureus isolates associated with a polymicrobial biofilm

Glycopeptides such as vancomycin are the treatment of choice for infections due to methicillin-resistant Staphylococcus aureus. This study describes the identification of high-level vancomycin-resistant S. aureus (VRSA) isolates in a polymicrobial biofilm within an indwelling nephrostomy tube in a patient in New York. S. aureus, Enterococcus faecalis, Enterococcus faecium, Micrococcus species, Morganella morganii, and Pseudomonas aeruginosa were isolated from the biofilm. For VRSA isolates, vancomycin MICs ranged from 32 to >128 microg/ml. VRSA isolates were also resistant to aminoglycosides, fluoroquinolones, macrolides, penicillin, and tetracycline but remained susceptible to chloramphenicol, linezolid, rifampin, and trimethoprim-sulfamethoxazole. The vanA gene was localized to a plasmid of approximately 100 kb in VRSA and E. faecium isolates from the biofilm. Plasmid analysis revealed that the VRSA isolate acquired the 100-kb E. faecium plasmid, which was then maintained without integration into the MRSA plasmid. The tetracycline resistance genes tet(U) and tet(S), not previously detected in S. aureus isolates, were identified in the VRSA isolates. Additional resistance elements in the VRSA isolate included a multiresistance gene cluster, ermB-aadE-sat4-aphA-3, msrA (macrolide efflux), and the bifunctional aminoglycoside resistance gene aac(6')-aph(2")-Ia. Multiple combinations of resistance genes among the various isolates of staphylococci and enterococci, including vanA, tet(S), and tet(U), illustrate the dynamic nature of gene acquisition and loss within and between bacterial species throughout the course of infection. The potential for interspecies transfer of antimicrobial resistance genes, including resistance to vancomycin, may be enhanced by the microenvironment of a biofilm.

Grand mal seizures: an unusual and puzzling primary presentation of ruptured hepatic hydatid cyst

We report a case of hepatic hydatidosis where the first clinical manifestations, generalized seizures after minor head and abdominal trauma, and delayed anaphylaxis, made the primary diagnosis difficult. Severe anaphylaxis has been reported as initial presentation of quiescent hepatic hydatidosis. In endemic areas, the diagnosis must be carefully ruled out in patients experiencing abrupt anaphylactic shock of uncertain etiology. The occurrence of unexplained vascular collapse after minor abdominal trauma in a patient originating from an endemic area should prompt the diagnosis and urgent treatment should be initiated; firstly emergency management of the anaphylactic shock and later, surgical treatment of the cysts.

33-jährige Libanesin mit rezidivierenden Hämoptysen und zystischer Raumforderung in der Lunge

A 33 year old woman from Lebanon presented with recurrent hemoptysis, subfebrile temperature, dyspnoe in stress, fatigue, weight loss, and pruritus. Serological tests and results from chest X-ray and computer tomography revealed cystic echinococcosis with pulmonary involvement. After refusal of surgical therapy a medical treatment with albendazole was implemented. Two months after the start of the therapy only a small fibrotic residuum in the lung was seen. A spontaneous healing success seems unlikely because of the duration of the pulmonary cyst and the progressive symptoms before treatment.

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci co-colonization

High prevalence of co-colonization increases risk for colonization or infection by vancomycin-resistant Staphylococcus aureus.

We assessed the prevalence, risk factors, and clinical outcomes of patients co-colonized with vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) upon admission to the medical and surgical intensive care units (ICUs) of a tertiary-care facility between January 1, 2002, and December 31, 2003. Co-colonization was defined as a VRE-positive perirectal surveillance culture with an MRSA-positive anterior nares surveillance culture collected concurrently. Among 2,440 patients, 65 (2.7%) were co-colonized. Independent risk factors included age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01–1.05), admission to the medical ICU (OR 4.38, 95% CI 2.46–7.81), male sex (OR 1.93, 95% CI 1.14–3.30), and receiving antimicrobial drugs on a previous admission within 1 year (OR 3.06, 95% CI 1.85–5.07). None of the co-colonized patients would have been identified with clinical cultures alone. We report a high prevalence of VRE/MRSA co-colonization upon admission to ICUs at a tertiary-care hospital.

Factors associated with morbitity in liver hydatid surgery

BACKGROUND

The purpose of the present paper was to determine the association between clinical evolutionary and laboratory variables with postoperative morbidity in patients surgically treated for liver hydatidosis (LH).

METHODS

A case-control nested cohort study was undertaken. Patients were studied and surgically treated in Hospital Regional of Temuco between 1994 and 2001. The morbidity variable registered with a minimum 12-month follow-up period was considered in a dichotomous way. The association with clinical, laboratory, evolutionary, and surgical variables was studied. Descriptive statistics, bivariate analysis using chi(2) and Fisher's exact test for categorical variables; t-test, anova, and Kruskal-Wallis for continuous variables; odds ratio calculations, and ordinal and multivariate logistic regression models were applied.

RESULTS

The cohort was composed of 202 patients surgically treated for LH, 112 women (55.5%) and 90 men (44.5%), with an average age of 45.2 years. Average morbidity of the series, with a median follow-up period of 53 months, was 16.4%. Six variables were significantly associated in the bivariate analysis (age, haematocrit, total leucocyte count, alkaline phosphatase, history of previous surgery for LH and existence of biliary communications), but only two achieved statistical significance in the multivariate model (age and history of previous surgery for LH; P = 0.017 and 0.018; and odds ratio of 1.0 and 4.1, respectively).

CONCLUSIONS

In surgical decision making for patients with LH, the history of previous surgery for LH must be considered as a risk factor for postoperative morbidity.

A New Percutaneous Approach for the Treatment of Hydatid Cyst of the Kidney: Long-term Follow-up

Renal hydatid disease is an uncommon benign parasitic infestation compared to liver hydatid disease. Although the treatment of hydatid cysts depends on surgery which is related with high morbidity and an overall local recurrence rates, the following case reports describing two patients with renal hydatid cysts were successfully treated with this new percutaneous method.

Vancomycin‐ResistantStaphylococcus aureusin the Absence of Vancomycin Exposure

We report findings from our investigation of the world's second clinical isolate of vancomycin-resistant Staphylococcus aureus (VRSA). An elderly man was hospitalized with an infected chronic heel ulcer and osteomyelitis. Before hospital admission, he received multiple courses of antibiotic therapy but, notably, no vancomycin. Numerous cultures of ulcer specimens (performed on an outpatient basis) grew methicillin-resistant, vancomycin-susceptible S. aureus and vancomycin-resistant Enterococcus species. At admission, an additional culture of a specimen from the heel ulcer grew S. aureus that was identified as VRSA (minimal inhibitory concentration for vancomycin [by broth-microdilution], 32 microg/mL). Further evaluation confirmed the presence of the vanA gene mediating vancomycin resistance. To assess VRSA transmission, we performed a carriage study of 283 identified contacts and an environmental survey of the patient's home; no VRSA isolates were recovered. This case illustrates that recent exposure by patients to vancomycin is not necessary for development of vanA-containing VRSA. For clinical and public health reasons, it is essential that microbiology laboratories adequately test for vancomycin-resistance in S. aureus.

Coexistence of vancomycin-resistant enterococci and Staphylococcus aureus in the intestinal tracts of hospitalized patients

The potential for transfer of vancomycin-resistance genes from enterococci to Staphylococcus aureus exists when these organisms share an ecologic niche. We performed an 8-month prospective study to determine the frequency at which S. aureus and vancomycin-resistant enterococci (VRE) coexist in the intestinal tracts of VRE-colonized patients and evaluated whether antianaerobic antibiotic therapy promoted increased density of S. aureus colonization. Of 37 patients colonized with vancomycin-resistant Enterococcus faecium, 23 (62%) had S. aureus recovered from stool specimens and 20 (87%) had methicillin-resistant strains. There was no significant difference in the mean density (+/- standard deviation) of S. aureus during versus > or =1 month after discontinuation of antianaerobic antibiotic therapy (5.1+/-1.5 vs. 4.7+/-1.6 log10 colony-forming units per gram of stool; P=.34). No S. aureus isolates were resistant to vancomycin. S. aureus and VRE often coexist in the intestinal tract, providing a potential reservoir for the emergence of vancomycin-resistant S. aureus isolates.

Vancomycin susceptibility of oxacillin-resistant Staphylococcus aureus isolates causing nosocomial bloodstream infections

Nosocomial oxacillin-resistant Staphylococcus aureus (ORSA) bloodstream isolates were tested to determine the prevalence of vancomycin heteroresistance. We screened 619 ORSA nosocomial bloodstream isolates from 36 hospitals between 1997 and 2000. Only one isolate exhibiting heterotypic resistance was detected. Thus, vancomycin heteroresistance in clinical bloodstream isolates remains rare in the United States.

Infection control measures to limit antimicrobial resistance

Increasing antimicrobial resistance has resulted in a rapidly decreasing array of therapeutic options for infections in the critical care setting. Reports of reduced susceptibility to vancomycin in Staphylococcus aureus raise the possibility of patients being infected with a virulent pathogen for which most antibiotics are ineffective. Infection control methods to contain resistance, exclusive of antimicrobial restrictions, focus on surveillance to identify carriers of resistant organisms, prevention of nosocomial infections, adequate hand hygiene, isolation of patients who harbor resistant organisms, and the use of barrier techniques such as gowns and gloves. Surveillance using clinical isolates alone is inadequate for the identification of the majority of patients who carry resistant organisms. However, it is unclear what intensity of surveillance is needed to control the spread of these organisms in the intensive care unit in nonoutbreak situations. Attempts at eradicating carriage are often unsuccessful when there is extranasal colonization with methicillin-resistant S. aureus. Transmission of resistant organisms is primarily the result of transient contamination of healthcare workers' hands. Adequate handwashing, isolation of carriers, and barrier techniques are all necessary for containing resistance within the intensive care unit, however, compliance with these measures can be compromised by high staff turnover and heavy workload.

Vancomycin-intermediate and -resistant Staphylococcus aureus: what the infectious disease specialist needs to know

Ever since the first strain of Staphylococcus aureus with reduced susceptibility to vancomycin and teicoplanin was reported from Japan, there has been a lot of confusion regarding the laboratory and clinical approach to patients with infections due to S. aureus with reduced susceptibility to vancomycin. To date, 6 clinical infections with vancomycin-intermediate S. aureus (VISA) have been reported in the United States. Intermediate resistance appears to develop from preexisting strains of methicillin-resistant S. aureus in the presence of vancomycin, and all but 1 infection occurred in patients with exposure to dialysis for renal insufficiency. Detection of VISA is difficult in the laboratory, and special inquiries about susceptibility testing methods may be needed. These VISA-infected patients had underlying illnesses, and their infections did not appear to respond well to conventional treatment. Prevention strategies have been outlined. Without continued vigilance in enforcing infection-control measures, improved use of antimicrobials, and coordination of efforts among public health authorities, increasing levels of vancomycin resistance in S. aureus are likely to be encountered.