Characterization of SCCmec Instability in Methicillin-Resistant Staphylococcus aureus Affecting Adjacent Chromosomal Regions, Including the Gene for Staphylococcal Protein A (spa).

Staphylococcal cassette chromosome mec (SCCmec) represents a sequence of clear clinical and diagnostic importance in staphylococci. At a minimum the chromosomal cassette contains the mecA gene encoding PBP2a but frequently also includes additional antibiotic resistance genes (e.g., ermA and aadC; macrolide and aminoglycoside resistance, respectively). Certain regions within SCCmec elements are hot spots for sequence instability due to cassette-specific recombinases and a variety of internal mobile elements. SCCmec changes may affect not only cassette stability but the integrity of adjacent chromosomal sequences (e.g., the staphylococcal protein A gene; spa). We investigated SCCmec stability in methicillin-resistant Staphylococcus aureus (MRSA) strains carrying one of four SCCmec types cultured in the absence of antimicrobial selection over a 3-month period. SCCmec rearrangements were first detected in cefoxitin-susceptible variants after 2 months of passage, and most commonly showed precise excision of the SCCmec element. Sequence analysis after 3 months revealed both precise SCCmec excision and a variety of SCCmec internal deletions, some including extensive adjacent chromosomal loss, including spa. No empty cassettes (i.e., loss of just mecA from SCCmec) were observed among the variants. SCCmec stability was influenced both by internal mobile elements (IS431) as well as the host cell environment. Genotypically similar clinical isolates with deletions in the spa gene were also included for purposes of comparison. The results indicate a role for host-cell influence and the IS431 element on SCCmec stability.

Molecular detection of carbapenem resistance genes in rectal swabs from patients in Gulf Cooperation Council hospitals.

BACKGROUND: Gram-negative organisms harbouring carbapenem resistance genes (CRGs) are spreading globally, including in Gulf Cooperation Council (GCC) countries. However, relatively few data are available about carriage of CRGs in hospitalized patients in this region. AIM: To determine prevalence of CRG carriage and risk factors for colonization among patients in GCC hospitals. METHODS: Rectal swabs were obtained from ∼50 intensive care unit (ICU) patients from each of 11 hospitals in five GCC countries between March and November 2019. The swabs were tested for the presence of blaKPC, blaNDM, blaVIM, blaIMP, and blaOXA-48 CRG using a commercial polymerase chain reaction test. Data on risk factors for colonization were collected and analysed. FINDINGS: Of 529 specimens screened, 138 (26.1%) were positive for one or more CRGs. The positivity rates among the hospitals ranged from 8.0% to 67.3%; ∼20% of the positive specimens harboured ≥2 CRGs. The most common CRG detected was blaOXA-48, which was present in 82 specimens (15.5%). Additional CRGs included blaNDM, blaVIM, blaKPC, and blaIMP either alone or in combination. Overall, 31.1% of patients on antibiotics on admission to the ICU were positive for CRGs compared to 16.5% not on antibiotic therapy (P < 0.001). CRG detection was also more common among patients aged >65 years (P = 0.027) and increased with hospital length of stay (P = 0.025). CONCLUSION: The rate of CRGs detected in hospitalized patients in GCC countries varied considerably. Prior antibiotic exposure, increasing age, and prolonged length of stay were associated with CRG detection.

Presence of Clostridioides difficile and multidrug-resistant healthcare-associated pathogens in stool specimens from hospitalized patients in the USA.

BACKGROUND: Healthcare-associated infections (HCAIs) continue to be a major cause of morbidity and mortality. Many HCAI pathogens, including multidrug-resistant organisms (MDROs), colonize the gastrointestinal tract. AIM: To determine the frequency of MDRO carriage in patients who do and do not harbour toxigenic Clostridioides difficile in their stools. METHODS: Stool specimens received from nine US laboratories were cultured using media selective for C. difficile, Staphylococcus aureus, vancomycin-resistant enterococci (VRE), and carbapenem-resistant Gram-negative organisms (CROs). Specimens and isolates were also tested by polymerase chain reaction (PCR). Bacterial isolates underwent susceptibility testing and genotyping. FINDINGS: Among 363 specimens, 175 yielded toxigenic C. difficile isolates spanning 27 PCR ribotypes. C. difficile (TCD+) stools harboured an additional 28 organisms, including six CROs (3.4%), of which two (1.1%) were carbapenemase-producing organisms (CPOs), 19 VRE (10.9%), and three meticillin-resistant S. aureus isolates (MRSA, 1.7 %). Stools that were culture negative for toxigenic C. difficile (TCD-) yielded 26 organisms, including four CROs (2.1%), 20 VRE (10.6), and two MRSA (1.1%). Excluding C. difficile, no significant differences were seen in the rates of the MDROs between TCD+ and TCD- specimens. CONCLUSION: Overall, 15.4% of the TCD+ stools and 11.2% of the TCD- stools carried at least one non-C. difficile MDRO pathogen, indicating that multiple MDROs may be present in the gastrointestinal tracts of patients, including those that harbour C. difficile.

Allelic variation in genes encoding Panton-Valentine leukocidin from community-associated Staphylococcus aureus.

Community-associated methicillin-resistant Staphylococcus aureus isolates characteristically contain the genes for Panton-Valentine leukocidin (PVL), which is a proposed virulence factor. To determine whether different alleles of the PVL genes lukS-PV and lukF-PV occur, and whether they are associated with specific genetic lineages of S. aureus, sequences from 28 S. aureus isolates, representing four different multilocus sequence types, and bacteriophages SLT and PVL were compared. Seven nucleotide polymorphisms were identified, which defined three groups of the lukS-PV and lukF-PV sequence. Only one polymorphism resulted in an amino-acid change. Bacteriophage SLT and isolates of bacteriophage type 80/81 contained the prototypic (founder) lukS-PV and lukF-PV sequence. The alleles were not lineage-specific.

Novel and emerging mechanisms of antimicrobial resistance in nosocomial pathogens.

Nosocomial pathogens frequently are resistant to antimicrobial agents. Although methicillin-resistant strains of Staphylococcus aureus continue to be a major problem in many hospitals, several new types of resistance determinants have been noted among organisms causing hospital-acquired infections. The mechanisms include extended spectrum beta-lactamases in gram-negative bacilli; resistance to beta-lactams, glycopeptides, and high levels of aminoglycosides among enterococci; quinolone resistance in isolates of methicillin-resistant S. aureus; and the spread of multiple resistance genes simultaneously in gram-negative organisms via Tn21-related genetic elements. These novel mechanisms of resistance complicate the treatment of nosocomial infections by limiting the number of effective antimicrobial agents available to the clinician. It is important for infection control practitioners and microbiologists to work together to detect and control the spread of resistant pathogens in the hospital setting.

Chronic fatigue in adolescents.

Nine female and 6 male adolescents (mean age 14.5 +/- 1.7 [SD] years) were evaluated for chronic fatigue associated with at least three additional symptoms present for 18.4 +/- 8.4 months. Eleven subjects experienced the onset of symptoms with an acute illness (seven Monospot-positive). Medical history, physical examination, and laboratory testing yielded little helpful information. Serologic testing for Coxsackie B viruses 1 through 6, cytomegalovirus, Epstein-Barr virus, human herpesvirus 6, and Toxoplasma gondii in subjects and healthy controls provided little evidence for an infectious cause of persistent fatigue. Children's Depression Inventory scores and psychiatric interviews with the Schedule for Affective Disorders and Schizophrenia-Children's Version (K-SADS) identified five subjects with major depression. On the K-SADS, the 10 fatigued subjects without major depression endorsed many secondary symptoms of depression but were less likely than depressed psychiatric clinic patients to endorse primary symptoms such as depressed mood, guilt, and suicidality. At telephone follow-up 13 to 32 months after intake, 4 subjects were completely well, 4 markedly improved, and 7 unimproved or worse. Further research is necessary to determine whether chronic fatigue in adolescents is prodromal depression, a discrete psychosomatic condition, or an infectious or immunologic disorder that mimics depression.

How to select and interpret molecular strain typing methods for epidemiological studies of bacterial infections: a review for healthcare epidemiologists. Molecular Typing Working Group of the Society for Healthcare Epidemiology of America.

Strain typing is an integral part of epidemiological investigations of nosocomial infections. Methods for distinguishing among bacterial strains have improved dramatically over the last 5 years, due mainly to the introduction of molecular technology. Although not all molecular techniques are equally effective for typing all organisms, pulsed-field gel electrophoresis is the technique currently favored for most nosocomial pathogens. Criteria to aid epidemiologists in interpreting results have been published. Nucleic acid amplification-based typing methods also are applicable to many organisms and can be completed within a single day, but interpretive criteria still are under debate. Strain typing cannot be used to replace a sound epidemiological investigation, but serves as a useful adjunct to such investigations.

Evidence of interhospital transmission of extended-spectrum beta-lactam-resistant Klebsiella pneumoniae in the United States, 1986 to 1993. The National Nosocomial Infections Surveillance System.

BACKGROUND: In addition to single-hospital outbreaks, interhospital transmission of extended-spectrum beta-lactam-resistant (ESBLR) Klebsiella pneumoniae has been suspected in some reports. However, these studies lacked sufficient epidemiological information to confirm such an occurrence. METHODS: We reviewed the surveillance data reported to the National Nosocomial Infections Surveillance (NNIS) System during 1986 to 1993 for K pneumoniae isolates and their susceptibility to either ceftazidime, cefotaxime, ceftriaxone, or aztreonam. Pulsed-field gel electrophoresis (PFGE) was used to study available ESBLR K pneumoniae isolates. RESULTS: Among 8,319 K pneumoniae isolates associated with nosocomial infections, 727 (8.7%) were resistant or had intermediate-level resistance to at least one of these antibiotics. One hospital (hospital A) accounted for 321 isolates (44.2%) of ESBLR K pneumoniae. During 1986 to 1993, the percentage of K pneumoniae isolates that were ESBLR increased from 0 to 57.7% in hospital A, from 0 to 35.6% in NNIS hospitals 0 to 20 miles from hospital A (area B), and from 1.6 to 7.3% in NNIS hospitals more than 20 miles from hospital A, including hospitals located throughout the United States. Analysis of PFGE restriction profiles showed a genetic relationship between a cluster of isolates from hospital A and some isolates from one hospital in area B, and consecutive admission in these two hospitals was confirmed for two patients from whom isolates were available. CONCLUSIONS: These data provide evidence of interhospital transmission of ESBLR K pneumoniae in one region of the United States and stress the interrelationship between hospitals when trying to control antimicrobial resistance.

Antimicrobial use and resistance in eight US hospitals: complexities of analysis and modeling. Intensive Care Antimicrobial Resistance Epidemiology Project and National Nosocomial Infections Surveillance System Hospitals.

OBJECTIVE: To evaluate the relation between antimicrobial use and resistance in intensive-care unit (ICU) and non-ICU inpatient areas in eight US hospitals. METHODS: We determined antimicrobial use in terms of defined daily doses, antimicrobial-use density (defined daily doses/1,000 patient days), and percentage resistance for five antimicrobial-organism combinations in the ICU and non-ICU inpatient areas of eight US hospitals participating in project Intensive Care Antimicrobial Resistance Epidemiology. RESULTS: Antimicrobial resistance and use varied tremendously among the eight hospitals. Antimicrobial resistance among these five nosocomial pathogens was significantly higher within the inpatient setting of these hospitals, compared with the outpatient setting. One hospital consistently ranked highest for use of all classes of antimicrobials examined. High antimicrobial use was not associated necessarily with high resistance for a particular antimicrobial-organism pair. CONCLUSION: Antimicrobial use varied significantly across these hospitals, but generally was higher in ICUs. These results suggest that concomitant surveillance of both antimicrobial resistance and antimicrobial use is helpful in interpreting antimicrobial resistance in a hospital or ICU and that further analysis is required to determine the role of variables other than antimicrobial use in a statistical model for predicting antimicrobial resistance.

Reporting of vancomycin-resistant enterococci in Connecticut: implementation and validation of a state-based surveillance system.

OBJECTIVE: To assess state-based surveillance for isolation from a sterile site of vancomycin-resistant enterococci (VRE) in Connecticut. DESIGN: Clinical laboratory reporting (passive surveillance) of VRE isolates to the Connecticut Department of Public Health (CDPH) was followed by state-initiated validation, laboratory proficiency testing, and review of hospital demographic characteristics. SETTINGS: All 45 clinical laboratories and all 37 (36 for 1995 and 1996) acute-care hospitals in Connecticut were included in the study. MAIN OUTCOME MEASURES: The outcome measures included determination of the statewide incidence of VRE and the accuracy of passive reporting, determination of clinical laboratory proficiency in detecting VRE, and analysis of hospital characteristics that might be associated with an increased incidence of VRE. RESULTS: During 1994 through 1996, 29 (78%) of 37 hospital-affiliated clinical laboratories and 1 (11%) of 9 commercial or other laboratories in Connecticut reported to the CDPH the isolation of VRE from sterile sites; 158 isolates were reported for these 3 years. Based on verification, we discovered that these laboratories actually detected 58 VRE isolates in 1994, 104 in 1995, and 104 in 1996 (total, 266). The age-standardized incidence rate of VRE was 14.1 cases per million population in 1994 and 26.8 cases per million population for both 1995 and 1996. Laboratory proficiency testing revealed that high-level vancomycin resistance was identified accurately and that low- and moderate-level resistance was not detected. The incidence of VRE isolates was three times greater in hospitals with over 300 beds compared with categories of hospitals with fewer beds. Increases in the number of VRE isolates were at least twice as likely in hospitals located in areas with a higher population density, or with a residency program or trauma center in the hospital. CONCLUSIONS: Passive reporting of VRE isolates from sterile sites markedly underestimated the actual number of iso lates, as determined in a statewide reporting system. Statewide passive surveillance systems for routine or emerging pathogens must be validated and laboratory proficiency ensured if results are to be accurate and substantial underreporting is to be corrected.

The emergence of decreased susceptibility to vancomycin in Staphylococcus epidermidis.

BACKGROUND: Coagulase-negative staphylococci (CNS) are the major cause of nosocomial bloodstream infection. Emergence of vancomycin resistance among CNS is a serious public health concern, because CNS usually are multidrug-resistant, and glycopeptide antibiotics, among which only vancomycin is available in the United States, are the only remaining effective therapy. In this report, we describe the first bloodstream infection in the United States associated with a Staphylococcus epidermidis strain with decreased susceptibility to vancomycin. METHODS: We reviewed the hospital's microbiology records for all CNS strains, reviewed the patient's medical and laboratory records, and obtained all available CNS isolates with decreased susceptibility to vancomycin. Blood cultures were processed and CNS isolates identified by using standard methods; antimicrobial susceptibility was determined by using minimum inhibitory concentration (MIC) and disk-diffusion methods. Nares cultures were obtained from exposed healthcare workers (HCWs) to identify possible colonization by CNS with decreased susceptibility to vancomycin. RESULTS: The bloodstream infection by an S. epidermidis strain with decreased susceptibility to vancomycin occurred in a 49-year-old woman with carcinoma. She had two blood cultures positive for CNS; both isolates were S. epidermidis. Although susceptible to vancomycin by the disk-diffusion method (16-17 mm), the isolates were intermediate by MIC (8-6 microg/mL). The patient had received an extended course of vancomycin therapy; she died of her underlying disease. No HCW was colonized by CNS with decreased susceptibility to vancomycin. CONCLUSIONS: This is the first report in the United States of bloodstream infection due to S. epidermidis with decreased susceptibility to vancomycin. Contact precautions likely played a role in preventing nosocomial transmission of this strain, and disk-diffusion methods may be inadequate to detect CNS with decreased susceptibility to vancomycin.

The prevalence of colonization with vancomycin-resistant Enterococcus at a Veterans' Affairs institution.

OBJECTIVE: To study vancomycin-resistant Enterococcus (VRE) prevalence, risk factors, and clustering among hospital inpatients. DESIGN: Rectal-swab prevalence culture survey conducted from February 5 to March 22, 1996. SETTING: The Veterans' Affairs Medical Center, Atlanta, Georgia. PATIENTS: Hospital (medical and surgical) inpatients. RESULTS: The overall VRE prevalence was 29% (42/147 patients). The VRE prevalence was 52% (38/73 patients) among patients who had received at least one of six specific antimicrobials during the preceding 120 days, compared with only 5% (4/74) among those who had not received the antimicrobials (relative risk, 9.6; P<.001). The longer the period (up to 120 days) during which antimicrobial use was studied, the more closely VRE status was predicted. Among 67 hospital patients in 28 multibed rooms, clustering of VRE among current roommates was not found. CONCLUSIONS: At this hospital with relatively high VRE prevalence, VRE colonization was related to antibiotic use but not to roommate VRE status. In hospitals with a similar VRE epidemiology, obtaining cultures from roommates of VRE-positive patients may not be as efficient a strategy for identifying VRE-colonized patients as obtaining screening cultures from patients who have received antimicrobials.

Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: guidelines for the prevention of antimicrobial resistance in hospitals.

Antimicrobial resistance results in increased morbidity, mortality, and costs of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

Increased detection of staphylococcal bacteremia using an anti-microbial removal device.

During the period of August 16, 1981, through December 16, 1982, 15-mL blood culture specimens collected at the Seattle Veterans Administration Medical Center (SVAMC) were divided into two aliquots. The first 10-mL aliquot was inoculated directly into aerobic and anaerobic BACTEC (Johnston Laboratories, Towson, MD) vials (DIR); the remaining 5 mL was processed in an resin-containing Antimicrobial Removal Device (Marion Scientific, Kansas City, MO) before transfer to a second, identical set of aerobic and anaerobic vials (ARD). The final volume of inoculated blood from the ARD specimen was half that of the DIR specimen. Both sets of vials were processed using the BACTEC radiometric detection system. One hundred fifty specimen pairs grew 161 significant pathogens; 43 isolates were recovered only from the ARD sample, 39 only from the DIR samples, and 79 from both. Of the 35 isolates recovered from patients receiving anti-microbial agents active against the isolated pathogens, 21 were recovered only from the ARD specimen and 5 only from the DIR specimen (P less than 0.005). Of the 15 S. aureus strains isolated from patients on therapy, 12 were recovered only from the ARD specimen, 2 only from the DIR sample, and 1 from both samples (P less than 0.01). Ten of the 32 isolates of S. aureus recovered from antibiotic-free patients were found only in the ARD specimen and three only in the DIR specimen (P = 0.05). The ARD specimens recovered significantly more S. aureus from all patients regardless of antibiotic status.

A transferable multiple drug resistance plasmid from Vibrio cholerae O1.

Ten multiple antimicrobial-resistant isolates of Vibrio cholerae O1 isolated from patients in Uganda were characterized, and the transferability of resistance to bacteria of diverse origins was investigated. The isolates were toxigenic and belonged to biotype E1 Tor, serotype Ogawa, and ribotype 8, and possessed a 130-MDa plasmid of incompatibility group 6-C. This plasmid, designated pRVC1, was shown to confer resistance to trimethoprim (mediated by a dhfrI gene), sulfonamides (a suII gene), tetracycline [a tet(C) gene], chloramphenicol (a catI gene), ampicillin (a beta-lactamase gene other than blaTEM or blaSHV), and streptomycin. pRVC1 proved to be transmissible at frequencies between 1 x 10(-1) and 5 x 10(-6) transconjugants per recipient to a variety of bacterial pathogens, including those of humans, animals, and fish. Most efficient transfer was observed from V. cholerae to strains of Shigella flexneri, Escherichia coli, Vibrio parahaemolyticus, and three Aeromonas species. The present in vitro study suggests that pRVC1 may spread from V. cholerae to other bacteria pathogenic to man, animals, and fish in natural environments.

DNA hybridization techniques and their application to the diagnosis of infectious diseases.

Several commercial DNA probe assays are widely used in clinical microbiology laboratories. These include culture-confirmation assays for Mycobacterium species, which are recommended by CDC because they are both rapid and accurate, and culture-confirmation assays for N. gonorrhoeae. Probe assays for direct detection of N. gonorrhoeae and C. trachomatis are also widely used in public health and large reference laboratories. In many cases, the probe assays have decreased the time to identification of positive cultures and improved detection of these pathogens because they do not depend on the presence of viable organisms to achieve a positive result. Nucleic acid amplification assays hold promise for the rapid detection and identification of many infectious agents. PCR using universal primers enables researchers to identify new agents of disease that cannot be cultured in vitro; more importantly, PCR provides a method for detecting the presence of any bacterial species, including common organisms, in normally sterile body fluids, such as blood and cerebrospinal fluids. The use of such primers may well give PCR the broad-based approach needed to identify organisms in the clinical microbiology laboratory of the future.

Control of antimicrobial resistance in the health care system.

Resistance continues to spread in nosocomial pathogens in acute care hospitals and other key settings of managed health care systems. Appropriate control measures for such resistant organisms depend, in part, on the pathways by which resistance has arisen. Unfortunately, these pathways differ greatly from organism to organism and setting to setting. Although the epidemiology of resistant organisms sometimes is similar to that of susceptible organisms of the same kind, in some situations it may be quite different. This article highlights some of the pathways leading to the development of resistance in bacteria and the relevance of these mechanisms to measures for the control of resistant bacteria in hospital and community settings.

Surveillance for the emergence and dissemination of antimicrobial resistance in bacteria.

Effective surveillance of antimicrobial-resistant bacteria is important for developing rational empiric therapy guidelines and for guiding public health efforts to control and prevent the spread of infective agents. Surveillance must include a timely and thorough review of the test results generated in clinical microbiology laboratories because this data serves as the core of surveillance activities. Besides ensuring data accuracy and optimizing detection of emerging resistance, the role of clinical microbiology also includes supporting the production of informative surveillance reports, providing laboratory resources for outbreak investigations, and monitoring the performance of commonly used susceptibility testing methods. Once the accuracy of susceptibility results has been validated, the data are used by public health agencies and professional societies to monitor resistance trends on a local, state, national, and international level. This information is also used to develop policies for prudent antimicrobial use locally and nationally.

Optimizing testing of methicillin-resistant Staphylococcus species.

Selection of the appropriate NaCl concentration for test medium for oxacillin susceptibility testing of Staphylococcus aureus and coagulase-negative staphylococci has been problematic when using different antimicrobial susceptibility testing methods. Broth microdilution, using cation-adjusted Mueller-Hinton broth + 2% NaCl, is the currently recommended reference method. There is currently no recommendation for the addition of NaCl to agar for dilution susceptibility tests when Staphylococcus species are tested with oxacillin. We examined the effects of adding 0, 2%, 4%, and 5% NaCl to Mueller-Hinton agar and broth for agar dilution, Etest, and broth microdilution tests. The results of these tests were compared with the reference broth microdilution results and with the results of a hybridization assay using a mec gene probe. We tested 223 strains of staphylococci, 128 of which were mec gene positive and had oxacillin minimum inhibitory concentrations (MICs) > or = 4 micrograms/ml. Seven strains of S. aureus were mec probe negative but were oxacillin resistant. Seven coagulase-negative strains (three S. epidermidis, one S. haemolyticus, and three S. simulans) were mec probe positive and were oxacillin susceptible. The MICs for oxacillin-resistant strains increased two- to fourfold with the addition of 2% NaCl, but the MICs for oxacillin-susceptible strains were unchanged. Major and very major interpretative rates ranged from 18.2% to 20.2% for agar dilution and Etest without NaCl added to the medium, and these rates decreased to < 1% with the addition of 2% NaCl to the medium. The addition of 4% or 5% NaCl caused major error rates of > 17% for all test methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of Vitek version 7.01 software for testing staphylococci against vancomycin.

We tested 143 isolates of staphylococci with vancomycin by the National Committee for Clinical Laboratory Standards broth microdilution (BMD) reference method and compared the results to those generated using the Vitek automated system (GPS-105 and GPS-107 cards and version 7.01 software). For ten isolates, the vancomycin MICs by BMD were 8 microg/ml. By Vitek, the vancomycin MICs ranged from 2 to 16 microg/ml. Vancomycin MICs of > or =32 microg/ml were reported for two additional isolates by Vitek; however, the MICs decreased to < or =0.5 microg/ml on retesting. By BMD, the vancomycin MICs for both isolates were 1 microg/ml. While the modal vancomycin MIC results by BMD for S. aureus and coagulase-negative staphylococci (CoNS) were both 1 microg/ml, Vitek results showed a mode of < or =0.5 microg/ml for S. aureus, and a mode of 2 microg/ml for CoNS. Vitek did not report vancomycin MICs of 1 or 4 microg/ml for any of the isolates tested. While the sensitivity of detecting staphylococci with reduced susceptibility to vancomycin appears to be improved with Vitek version 7.01 software, when compared to earlier software versions, laboratories may notice an overall shift in MIC data toward higher vancomycin MICs, although for the most part, this does not affect the categorical interpretations of the results.