Vancomycin-resistant enterococci

Chloramphenicol treatment for vancomycin-resistant Enterococcus faecium bacteremia

OBJECTIVE

To evaluate the results of treating vancomycin-resistant Enterococcus faecium (VREF) bacteremia with chloramphenicol.

METHODS

We retrospectively reviewed the charts of all adult patients with VREF bacteremia treated with chloramphenicol during the calendar year 1998 at a 522-bed tertiary referral center in New York City. Patients were identified by reviewing microbiology laboratory records. Patients with clinically significant VREF bacteremia who received chloramphenicol for at least 48 h were included in the study. Clinical and microbiological outcomes were determined. Microbiological and molecular tests were performed on a small representative sample of isolates to identify the presence of resistance mechanisms and to look for similarity among the isolates.

RESULTS

Seven episodes of significant VREF bacteremia occurred in six patients. Mean age was 54 years. All patients had cancer and three had severe neutropenia. Five of seven episodes were associated with chronic indwelling devices, but in only one of these cases was the device removed. All isolates were susceptible to chloramphenicol in vitro. All six microbiologically evaluable episodes had a favorable response to chloramphenicol treatment, and four of seven (57%) clinically evaluable episodes had favorable outcomes. Only one death may have been due to VREF bacteremia, so the maximal attributable mortality was 14%. The three representative samples that were tested further were indistinguishable from one another and they displayed no evidence of resistance mechanisms.

CONCLUSIONS

In a cohort of severely ill cancer patients, chloramphenicol was effective in treating VREF bacteremia. The use of chloramphenicol should be considered in treating infections with this highly resistant organism, where therapeutic options are limited.

The Internet: a practical example of the use of new technology in the assessment of vancomycin use in pediatrics. The Pediatric Prevention Network

BACKGROUND

The rapid emergence of both new infections and new technologies has revolutionized health care during the past 50 years. Increased use of the Internet has enabled health care professionals to educate, interact, and collaborate throughout the world in ways never before possible. Increased use of vancomycin has been associated with the emergence of organisms with decreased susceptibility to vancomycin, such as Enterococcus and staphylococcal species. The purpose of this article is to describe our experience using Internet technology to assess vancomycin use at children's hospitals in the United States.

METHODS

A Web-based evaluation was developed and distributed on the Internet to 57 Pediatric Prevention Network hospitals. The evaluation was structured to collect summary statistics on vancomycin use and admissions data by service for 1997 and 1998.

RESULTS

Twenty-four hospitals were able to provide archived vancomycin use and patient admissions data; completed evaluations were returned from 15 hospitals (62.5% response rate). Personnel at 6 (40%) hospitals completed the evaluation directly on the Internet.

CONCLUSIONS

In our study, Internet technology facilitated a more efficient evaluation of vancomycin use, but fewer than half of the personnel at Pediatric Prevention Network hospitals completed the evaluation directly on the Internet. It is unclear whether personnel at these hospitals were limited in Internet access, support, or understanding. Efforts should be directed to educate health care personnel on the advantages of the Internet. Furthermore, many of the pharmacy databases used in our assessment were not standardized across hospitals nor systematically validated. Understanding that limitations still remain-within the source of the data studied, the health care system sampled, and the Internet tools available-is essential because the Internet offers health care professionals today a tool both to protect patients and to improve quality throughout the world.

Comparison of three methods to recover vancomycin-resistant enterococci (VRE) from perianal and environmental samples collected during a hospital outbreak of VRE

OBJECTIVE

To establish an efficient and sensitive technique for recovering vancomycin-resistant enterococci (VRE) from perianal and environmental samples collected during implementation of control measures for an outbreak of VRE.

DESIGN

Perianal and environmental samples were collected in triplicate on sterile swabs. One swab was used to inoculate a selective broth medium containing 6 pg of vancomycin and 8 pg of ciprofloxacin per mL, one to inoculate Campylobacter agar containing 10 microg/mL of vancomycin, and one to inoculate Enterococcosel agar containing 8 microg/mL of vancomycin.

SETTING

Samples were collected in the intensive care units of a 600-bed university hospital over a period of 2 months. SAMPLE SELECTION: Patients and their immediate environment were sampled if they resided in a ward with a patient known to be colonized or infected with VRE.

RESULTS

Of the 88 perianal samples obtained from 63 patients, 37 were positive for VRE by broth culture, with 36 also recovered on both types of solid media (sensitivity, 97.3%; negative predictive value, 98.1%). Of the initial samples collected from each of the 63 patients, 20 were positive for VRE by all methods. Of the 500 environmental samples cultured, 139 were positive for VRE in broth, with only 33 recovered on Campylobacter agar (sensitivity, 23.7%; negative predictive value, 77.2%) and 22 on Enterococcosel agar (sensitivity, 15.8%; negative predictive value, 75.2%).

CONCLUSIONS

Our data indicate that, when performing surveillance cultures during an outbreak of VRE, use of an enrichment broth medium is required to recover VRE contaminating environmental surfaces; however, direct inoculation to selective solid medium is adequate to recover VRE in patient perianal specimens.

Relationships between enterococcal virulence and antimicrobial resistance

Enterococci have become a vexing problem in clinical medicine because of their ability to infect patients who are typically receiving antibiotic therapy for unrelated underlying illness. Moreover, the infections have become extremely difficult to manage because of the accumulation of antibiotic resistances among enterococci. The ability of enterococci to cause disease is an intrinsic property of the organism or possibly subpopulations within enterococcal species. The probability of an infection's becoming established, however, is almost certainly in part a function of the enterococcal burden. By altering endogenous bacterial flora, antibiotic therapy promotes increased colonization by antibiotic-resistant organisms. Therefore, antibiotic resistance and intrinsic virulence both contribute to disease, but in separate and complementary ways. We review the virulence of enterococci, as distinct from the acquisition of antimicrobial resistance genes, and identify current gaps in our understanding of enterococcal virulence and the basis for disease.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Acquired and intrinsic glycopeptide resistance in enterococci

Enterococci are Gram-positive cocci responsible for severe human infections, such as endocarditis, meningitis, and septicemia and constitute an increasingly frequent cause of nosocomial infections. Enterococci are resistant to nearly all classes of drugs including, since 1986, glycopeptides. Vancomycin and teicoplanin act by blocking cell wall formation and resistance is due to synthesis of modified late peptidoglycan precursors. Glycopeptide resistance can be intrinsic or acquired and strains may be resistant to vancomycin and teicoplanin, or to vancomycin only. Five types of glycopeptide resistance and their biochemical mechanisms have been described in enterococci. Clinical isolates that are dependent on vancomycin for growth have been isolated. Data suggest a dual origin for resistance: glycopeptide-producing organisms or enterococcal species intrinsically resistant to these drugs.

Typeability of Tn1546-like elements in vancomycin-resistant enterococci using long-range PCRs and specific analysis of polymorphic regions

Molecular subtyping of the VanA-type resistance element Tn1546 in an international collection of 81 genomically diverse vancomycin-resistant enterococci (VRE) from human, animal, and environmental reservoirs was evaluated by restriction analysis of long-range PCR amplicons (PCR-RFLP), single gene PCRs, Southern blot analysis of genomic digests, and partial DNA sequencing. A dominant Tn1546-RFLP in accordance with Enterococcus faecium BM4147 was detected in 43 of the 49 long-range PCR positive strains from ecologically diverse sources in several European countries and the US. Tn1546-like elements from the 32 (40%) long-range PCR negative strains were typed into 17 different groups by single-gene PCRs and Southern blot analysis of the ORF1, ORF2, vanS-vanH, vanX-vanY, and vanZ regions. All these isolates showed deletions in the ORF1 and/or vanZ primer binding regions explaining the failure of long-range PCR amplification. Enlarged vanS-vanH or vanX-vanY fragments were detected in 7 (22%) and 16 (50%) of the long-range PCR negative strains, respectively. The enlarged vanS-vanH regions of five clinical isolates from the US (n = 2), Ireland (n = 2), and Norway (n = 1) contained identical IS1251-like insertions indicating intercontinental spread of the vanA gene cluster. Intergenic vanS-vanH IS1251 insertions have so far not been reported in European studies. Structural rearrangements of Tn1546-like elements may represent single recombination events that can serve as fingerprints in the molecular examination of vanA gene cluster evolution and transmission. The optimal strategy for such analysis has yet to be determined. Two alternative long-range PCRs with subsequent RFLP analysis were successfully used to type the majority of vanA gene clusters in an ecologically and geographically heterogeneous VRE strain collection, but failed to detect and type a group of variant Tn1546-like elements truncated in the left-end ORF1/ORF2 region. Further subtyping of such variants should specifically target the polymorphic vanS-vanH and vanX-vanY regions.

Vancomycin-resistant enterococci

After they were first identified in the mid-1980s, vancomycin-resistant enterococci (VRE) spread rapidly and became a major problem in many institutions both in Europe and the United States. Since VRE have intrinsic resistance to most of the commonly used antibiotics and the ability to acquire resistance to most of the current available antibiotics, either by mutation or by receipt of foreign genetic material, they have a selective advantage over other microorganisms in the intestinal flora and pose a major therapeutic challenge. The possibility of transfer of vancomycin resistance genes to other gram-positive organisms raises significant concerns about the emergence of vancomycin-resistant Staphylococcus aureus. We review VRE, including their history, mechanisms of resistance, epidemiology, control measures, and treatment.

Relationships between enterococcal virulence and antimicrobial resistance

Enterococci have become a vexing problem in clinical medicine because of their ability to infect patients who are typically receiving antibiotic therapy for unrelated underlying illness. Moreover, the infections have become extremely difficult to manage because of the accumulation of antibiotic resistances among enterococci. The ability of enterococci to cause disease is an intrinsic property of the organism or possibly subpopulations within enterococcal species. The probability of an infection's becoming established, however, is almost certainly in part a function of the enterococcal burden. By altering endogenous bacterial flora, antibiotic therapy promotes increased colonization by antibiotic-resistant organisms. Therefore, antibiotic resistance and intrinsic virulence both contribute to disease, but in separate and complementary ways. We review the virulence of enterococci, as distinct from the acquisition of antimicrobial resistance genes, and identify current gaps in our understanding of enterococcal virulence and the basis for disease.

Preventing the spread of vancomycin-resistant enterococci in a long-term care facility

OBJECTIVES

To test the hypothesis that infection control practices can prevent the spread of vancomycin-resistant enterococci (VRE) to residents of a long-term care facility (LCF) from an affiliated acute care facility with a high endemic rate of colonization.

DESIGN

Point prevalence study of the rate of rectal colonization.

SETTING

A state-supported veterans nursing home and an acute care veterans hospital.

PARTICIPANTS

Residents in a state veterans home.

INTERVENTIONS

Identification of patients with rectal colonization by VRE before transfer to the state veterans home, contact isolation for colonized veterans, use of oral bacitracin to eliminate colonization.

MEASUREMENTS

Rectal swab and culture for VRE, review of clinical records and recording of presumptive risk factors for VRE colonization. The risk factors were age, gender, length of stay at nursing home, treatment with vancomycin or oral antibiotics, prior hospitalization at the acute care facility during the prior year, use of indwelling urethral catheters, presence of diarrhea, and fecal or urinary incontinence.

RESULTS

Sixty-nine of 200 residents were cultured in the first study (1996) and 130 of 230 residents were cultured in the second study (1998). Residents who consented to culture differed from those who did not only with regards to gender (2 vs 7, P = .012). In neither study were any residents found to be colonized with VRE who had not already been identified as positive on admission.

CONCLUSIONS

Adherence to infection control practices by the patient care staff of the LTCF was associated with the absence of transmission of VRE colonization among its residents. The presence of rectal colonization with VRE in an acute care patient should not be a barrier to acceptance in a nursing home.

Nosocomial outbreak of vancomycin-resistant Enterococcus faecium at a German university pediatric hospital

Nosocomial Infections caused by vancomycin-resistant enterococci (VRE) are an emerging threat to critically ill patients. At the University Hospital Eppendorf, VRE were isolated from 38 patients between August 1993 and April 1997, of whom 32 were hospitalized at the Department of Pediatrics. Pulsed-field gel electrophoresis revealed that 26 Enterococcus faecium isolates from patients of the Department of Pediatrics were identical or closely related, and that isolates from three additional patients of the same department were possibly related. All of these isolates were of vanA genotype. They were resistant to glycopeptides, ampicillin, ciprofloxacin, clindamycin, and erythromycin. Most isolates displayed high-level resistance to gentamicin, but all remained susceptible to quinupristin/dalfopristin. Implementation of stringent hand disinfection and environmental disinfection policies, as well as measures for patient isolation contained this first outbreak of VRE at a German Children's hospital, which emphasizes the importance of hygienic measures for the control of nosocomial spread of these organisms.

Outbreak of vancomycin-resistant enterococci in a burn unit

OBJECTIVE

To investigate and control an outbreak of colonization and infection caused by vancomycin-resistant enterococci (VRE) in a burn intensive care unit (BICU).

DESIGN

Epidemiological investigation, including multiple point-prevalence culture surveys of patients and environment, cultures from hands of healthcare workers (HCWs), pulsed-field gel electrophoresis (PFGE) typing of patient and environmental isolates, case-control study, and institution and monitoring of control measures.

SETTING

BICU in an 800-bed university medical center in Galveston, Texas.

RESULTS

Between June 6, 1996, and July 14, 1997, 21 patients were colonized by VRE, and 4 of these patients developed bacteremia. Of 2,844 environmental cultures, 338 (11.9%) were positive, but all hand cultures from HCWs were negative. PFGE typing indicated that the outbreak was clonal, with VRE isolates from patients differing by < or =4 bands from the index case. Thirteen of 14 environmental isolates varied by < or =4 bands from the pattern of the index case. A case-control study analyzed by exact logistic regression identified diarrhea (odds ratio [OR], 43.9; 95% confidence interval [CI95], 5.5-infinity; P=.0001) and administration of an antacid (OR, 24.2; CI95, 2.9-infinity; P=.002) as independent risk factors for acquisition of VRE. During a 5-week period in October and November 1996, all patient and 317 environmental cultures were negative for VRE. The outbreak recurred from a contaminated electrocardiogram lead that had not been identified during the prior 5 weeks. VRE were finally eradicated from the BICU in July 1997, using barrier isolation and a very aggressive environmental decontamination program.

CONCLUSIONS

A VRE outbreak in a BICU over 13 months was caused by a single clone. After apparent eradication of VRE from a BICU, recrudescence of the outbreak occurred, evidently from a small inapparent source of environmental contamination. Changes in gastrointestinal (GI) tract function (motility) and administration of medications, other than antibiotics, that have an effect on the GI tract may increase the risk of GI tract colonization by VRE in burn patients. Application of barrier isolation and an aggressive environmental decontamination program can eradicate VRE from a burn population.

Control of glycopeptide-resistant enterococci in an oncology unit

Enterococci are responsible for 10-12% of nosocomial infections. Since 1987 the incidence of glycopeptide-resistant enterococci (GRE; termed vancomycin-resistant enterococci in the United States) has increased dramatically. The mechanism of GRE is well understood and involves mutation of a single terminal amino acid in a peptidoglycan precursor leading to reduced vancomycin affinity. Studies implicated antibiotic selection pressure as a major risk factor for GRE infection and colonization. In the hematology unit of a London hospital, GRE emerged in December 1993, with 38% of patients positive in a point prevalence study. Between December 1993 and June 1995, 13 patients acquired GRE bacteremia, five of whom died. Between 1995 and 1996 a prospective sequential study was undertaken to determine the effect of changing antibiotic treatment of febrile neutropenia (FN). All patients admitted to the hematology unit were enrolled in the study. In phase 1, treatment continued with ceftazidime monotherapy. In phase 2, piperacillin-tazobactam replaced ceftazidime, and enhanced infection control measures were encouraged. In phase 3, therapy returned to ceftazidime. In phase 1, 57% of patients became colonized or infected with GRE. Phase 2, which was divided into two 4-month cohorts, showed a significant reduction in GRE acquisition, falling to 8% colonization and no clinical infections in the second 4 months. In phase 3, despite heightened infection control procedures, the acquisition rate rose to 36%.

Continuing high prevalence of VanA-type vancomycin-resistant enterococci on Norwegian poultry farms three years after avoparcin was banned

Avoparcin was used as a feed additive in Norwegian broiler and turkey production from 1986 until 1995. It was banned due to the selection of VanA-type vancomycin-resistant enterococci (VRE) in animal husbandry and to reduce the potential for human exposure to VRE. The aim of the present study was to investigate the prevalence of VRE carriage in Norwegian poultry farmers and their poultry three years after avoparcin was banned. Corresponding faecal samples from poultry and humans on farms where avoparcin had previously been used (exposed farms, n = 73) and farms where avoparcin had never been used (unexposed farms, n = 74) were analysed for the presence of VRE. For each farm, one sample from the poultry house and one sample from the farmer were obtained. VRE were isolated from 72 of 73 (99%) and eight of 74 (11%) poultry samples from exposed and unexposed farms, respectively. VRE were isolated from 13 of 73 (18%) and one of 74 (1%) farmer samples from exposed and unexposed farms, respectively. All VRE isolates were highly resistant to vancomycin and possessed the vanA gene, as shown by PCR. The high prevalence of VRE is in accordance with previous Norwegian studies, and shows a remarkable stability of the VanA resistance determinant in an apparently non-selective environment.

Pathogenic Mechanisms of Enterococcal Endocarditis

Enterococci are gram-positive bacteria that are now established as major nosocomial pathogens and have become increasingly important in recent years due to the development and transmission of antibiotic resistance traits. These organisms commonly cause a variety of nosocomial infections, including surgical wound infections and urinary tract infections, as well as cardiovascular infections such as bacteremia and endocarditis. Infective endocarditis is a life-threatening microbial infection of the endothelial surface of the heart, which typically occurs on heart valve tissue. The enterococci are the third most common cause of infective endocarditis, and are becoming increasingly significant in this disease. In this review, we discuss the role of enterococci in infective endocarditis and focus on the current knowledge of enterococcal virulence mechanisms, with specific reference to this disease.

Efficacy of percutaneous abscess drainage in patients with vancomycin-resistant enterococci

OBJECTIVE

We reviewed a 4-year experience draining fluid collections infected with vancomycin-resistant enterococci to determine the outcome of percutaneous intervention in patients with this highly resistant and increasingly common organism.

MATERIALS AND METHODS

Charts of patients from whom vancomycin-resistant enterococci had been isolated during percutaneous drainage were reviewed to determine patient response to drainage, catheter management, and outcome of treatment.

RESULTS

Twenty-one patients underwent percutaneous drainage of 28 fluid collections from which vancomycin-resistant enterococci were isolated, including 16 intraabdominal abscesses, seven biliary or urinary obstructions, and five empyemas. The drainage of 27 (96%) of 28 collections were technically successful. In seven patients, drainage provided the first isolation of vancomycin-resistant enterococci from the patient. Five patients also had blood cultures with positive findings for vancomycin-resistant enterococci, and 14 collections were coinfected with other bacteria or with fungi. Twenty collections (71%) or obstructions were successfully treated with percutaneous drainage. Drainage was unsuccessful in treating eight collections in seven patients.

CONCLUSION

Despite high-level antibiotic resistance, fluid collections infected with vancomycin-resistant enterococci can be successfully drained percutaneously, resulting in a favorable likelihood of recovery for patients.

Comparison of efficacy and safety of teicoplanin and vancomycin in children with antineoplastic therapy-associated febrile neutropenia and gram-positive bacteremia

To compare their efficacy and safety, teicoplanin and vancomycin were randomly administered to 32 children for 52 gram-positive bacteremias during malignancy-associated neutropenia (<1000/microl). Patients mainly suffered from hematological malignancies. Twenty-five episodes were treated with teicoplanin (10 mg x kg(-1) x d(-1)) and 21 with vancomycin (40 mg x kg(-1) x d(-1)) plus ceftazidime and netilmicin. Six episodes were treated with teicoplanin because of previous "red man" reaction to vancomycin. Staphylococci (12% Staphylococcus aureus) were isolated from 50 episodes and viridans streptococci from 2. Defervescence on 3rd-4th day occurred in 29/31 (93.5%) teicoplanin-treated and 18/21 (85.7%) vancomycin-treated episodes. All 12 teicoplanin-treated and 13/13 vancomycin-treated episodes with repeat blood cultures on 3rd-4th day showed microbiological response. Two teicoplanin-treated and 3 vancomycin-treated patients required antifungals. Mild renal insufficiency appeared in 5 vancomycin-treated patients that was corrected without drug discontinuation. While both glycopeptides exhibit equal clinical and microbiological efficacy, teicoplanin is less likely to induce allergic reactions or nephrotoxicity in children.

Isolation and characterization of glycopeptide-resistant enterococci from hospitalized patients over a 30-month period

In February 1996, a Hospital Infection Control Practices Advisory Committee-style screening program was commenced to isolate and subsequently characterize glycopeptide-resistant enterococci (GRE) from patients at a hospital trust in Glasgow, Scotland. Over the next 30 months, GRE were isolated from 154 patients. GRE were isolated from patients in traditionally high-risk areas such as the renal unit and intensive care unit and also in areas considered to be lower risk, including medical wards and associated long-stay geriatric hospitals. The majority (90%) of isolates were Enterococcus faecium vanB. The remaining isolates consisted of seven E. faecalis (vanA), three E. gallinarum (vanC), and a further six E. faecium (five vanA, one both vanA and vanB) isolates. Analysis of SmaI-digested DNA by pulsed-field gel electrophoresis revealed that 34 of 40 (85%) VanB E. faecium isolates were identical or closely related, while 11 of 13 (85%) VanA GRE were distinct. High-level aminoglycoside resistance was seen in less than 8% of isolates. VanB E. faecium isolates were almost uniformly resistant to ampicillin and tetracycline. In this study, GRE have been isolated over a prolonged period from a broad range of patients. Glycopeptide resistance within the study hospital trust appeared to be mainly due to the clonal dissemination of a single strain of E. faecium VanB.

[Problems with gram-positive bacteria: resistance in staphylococci, enterococci, and pneumococci to antimicrobial drugs]

The resistance in staphylococci, enterococci, and pneumococci is reviewed. The author also recalls the first cases, and presents an overview of the distribution of cases in the world, the genetic and molecular mechanisms of resistance, the importance in Brazil and therapeutic alternatives. The factors that contribute to the dissemination of these problem bacteria and the measures for their control are emphasized.

Nosocomial cross transmission as a primary cause of vancomycin-resistant enterococci in Austria

Stool specimens from 226 patients from intensive care units (N=69), general wards (N=112), and outpatient-clinics (N=45) at the Innsbruck University Hospital and from 433 healthy volunteers were inoculated on to Enterococcosel Agar supplemented with 5 microg/mL vancomycin and 4 microg/mL cefodizime. Faecal specimens from 105 dairy cows, 171 pigs and 47 egg-laying hens were processed the same way. Thirteen of 226 patients (5.8%) harboured 14 vancomycin-resistant enterococci (VRE) of the vanA genotype; 12 E. faecium (from 11 patients) and two E. faecalis (ICU patients: 5.8%, general ward patients: 5.4%, outpatients: 6.7%). None of the faecal specimens from healthy volunteers or animals yielded VRE. Nine of the 13 patients harbouring VRE had received antibiotic therapy during the previous four weeks (broad-spectrum cephalosporins: six patients; i.v. vancomycin: five patients). Of the 14 VRE (vanA type) isolates six strains were indistinguishable by PFGE using Sma I as restriction endonuclease, six strains formed three pairs, and only two single isolates showed unique patterns. The results of our study supports the view that nosocomial cross transmission is currently the main cause of colonization and infection with VRE in Austria.

Role of transposon Tn5482 in the epidemiology of vancomycin-resistant Enterococcus faecium in the pediatric oncology unit of a New York City Hospital

During a 36-month period between 1993 and 1995 in the Pediatric Oncology Unit of Memorial Sloan Kettering Cancer Center, 74 patients experienced episodes of infection or colonization caused by vancomycin-resistant enterococci (VRE). Characterization of the 74 bacterial isolates by microbiological and molecular techniques (pulsed-field gel electrophoresis and hybridization with DNA probes specific for the vanA and vanB genes and for IS1251) identified 73 Enterococcusfaecium and one Enterococcusfaecalis (vanB) among the primary VRE isolates. Most (69/73) of the E. faecium isolates carried vanA and four isolates, the vanB gene complex. The overwhelming majority (67/69) of the vanA -positive isolates also gave hybridization signal for IS1251, indicating the presence of the newly described conjugative transposon Tn5482. No hybridization with IS1251 was obtained with the four vanB-carrying isolates. About 30% of the vanA-positive strains (23/69) were represented by PFGE subtype variants of a single clone, most isolates of which were recovered during a 4-month period between April to June of 1994. The larger portion of the vanA-carrying VRE represented by close to 70% of the isolates (46/69) belonged to as many as 37 different clonal types, indicating tremendous genetic diversity. Among 67 of the 69 vanA-carrying isolates, the localization of the Tn5482-associated vanA gene complex could be unequivocally identified either on the chromosome (40/69) or in plasmids (27/69). Transconjugants recovered from filter mating experiments using either a chromosomally located or plasmid-borne vanA donor strain and a single vancomycin-susceptible strain of either E. faecium or E. faecalis were analyzed by molecular typing techniques. Seven out of 10 independent transconjugants recovered from the same cross showed extensive differences in PFGE pattern and also in the localization of the vanA hybridizing DNA fragment transferred from the common VRE donor with chromosomally located vanA. The observations suggest that the extensive genetic diversity observed among the clinical isolates of VRE may be generated during conjugation between vancomycin-resistant and -susceptible enterococcal isolates. The observations also suggest that the epidemic spread of VRE in the United States may be linked to the frequent presence of Tn5482 among the American isolates.

Vancomycin resistance in Gram-positive bacteria other than Enterococcus spp

This is a review article on vancomycin resistance on gram positive bacteria other than enterococci. Epidemiology of varying resistance, its clinical relevance and therapeutic options in infections caused by vancomycin resistant Listeria spp., Corynebacteria, streptococci and staphylocci are discussed.

A nationwide, multicenter, case-control study comparing risk factors, treatment, and outcome for vancomycin-resistant and -susceptible enterococcal bacteremia

National Nosocomial Resistance Surveillance Group participants from 22 hospitals across the United States reviewed medical records for hospitalized patients with vancomycin-resistant enterococcal (VRE) or vancomycin-susceptible enterococcal (VSE) bacteremia to identify risk factors associated with the acquisition of VRE bacteremia, describe genetic traits of VRE strains, and identify factors predictive of clinical outcome. VRE cases were matched to VSE controls within each institution. Multiple logistic regression (LR) and classification and regression tree (CART) analysis were used to probe for factors associated with VRE bacteremia and clinical outcome. A total of 150 matched-pairs of VRE cases and VSE controls were collected from 1995 to 1997. Using LR, the following were found to be highly associated with VRE bacteremia: history of AIDS, positive HIV status, or drug abuse (OR 9.58); prior exposure with parenteral vancomycin (OR 8.37); and liver transplant history (OR 6. 75). CART analysis revealed that isolation of Enterococcus faecium, prior vancomycin exposure, and serum creatinine values > or = 1.1 mg/dl were predictors of VRE bacteremia. Greater proportions of clinical failure (60% versus 40%, P < 0.001) and all-cause mortality (52% versus 27%, P < 0.001) were seen in patients with VRE versus VSE bacteremia. Results from both LR and CART indicated that patients with persisting enterococcal bacteremia, intubation at baseline, higher APACHE II scores, and VRE bacteremia were at greater risk for poor outcome.

[Effects of restrictions on use of vancomycin in a German university hospital]

BACKGROUND

Recently, increasing antibiotic resistance has been observed among gram-positive bacteria. However, only few isolates were found to be resistant against glycopeptides. Therefore, internationally accepted guidelines recommend a restricted use of vancomycin and other glycopeptide antibiotics in order to prevent the development of resistance against these clinically important antibiotics. In many countries, the hospital pharmacies play a key role in control and reinforcement of antibiotic formulary restrictions. In Germany, however, the hospital pharmacies usually do not take over such control functions, and most wards keep a stock of regularly used drugs including antibiotics, which makes reinforcement of restrictions difficult.

METHODS

In an attempt to achieve a restriction of vancomycin use, the pharmacy of our university hospital was advised to deliver vancomycin to the wards only on request with a special order form signed by an attending, individually for every patient who should receive vancomycin. The efficacy of this restriction measure was evaluated in 3-month periods before and after the restriction became effective.

RESULTS

Hospitalwide, this led to a 20.1% reduction of i.v. vancomycin and an 85.7% reduction of oral vancomycin use per 1000 patient days. If the hematology/oncology units were not considered, the reduction of i.v. vancomycin use was 41.8%, and the total use after the restriction 24.2 g per 1000 patient days. Microbiology results which justified the use of vancomycin decreased by 8.3% (10.9% hematology/oncology units not considered) between the 2 observation periods. Assuming a 7-day mean course of i.v. vancomycin therapy, the empirical use of i.v. vancomycin decreased from 39.9% to 8% after the restriction had been instituted.

CONCLUSION

Allowing only experienced physicians (attendings) to decide on the use of vancomycin therapy, proved in our experience to be an effective measure to reduce unnecessary vancomycin use.

High prevalence of antibiotic resistance of common pathogenic bacteria in Taiwan. The Antibiotic Resistance Study Group of the Infectious Disease Society of the Republic of China

We analyzed the antimicrobial susceptibilities of all clinical isolates of 14 common pathogenic bacteria recovered from patients in eight medical centers in Taiwan during 1995 and 1996. Susceptibility to commonly used antimicrobial agents was tested by the disk diffusion method as recommended by the National Committee for Clinical Laboratory Standards. Of the Staphylococcus aureus isolates, 59.3% and 62% were oxacillin-resistant in 1995 and 1996, respectively, whereas 63.2% of the coagulase-negative staphylococci isolates during the study period were oxacillin-resistant. The rate of penicillin-resistance among Streptococcus pneumoniae isolates was 39.7% in 1995 and 53.7% in 1996. Macrolide-resistance was found in 71.4%, 42.1%, and 46.7% of S. pneumoniae, beta-hemolytic streptococci, and viridans streptococci, respectively, in 1996. Less than 2% of the enterococcal isolates were vancomycin resistant, but 77% of them were gentamicin resistant. Resistance to gentamicin was also common in Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter baumannii. Various degrees of resistance to ampicillin, piperacillin, cephalosporins, aztreonam, and ciprofloxacin were detected in Enterobacteriaceae, P. aeruginosa, and A. baumannii. More than 55% of Haemophilus influenzae isolates were ampicillin resistant. In summary, resistance to many antimicrobial agents in various common pathogenic bacteria is very common in Taiwan. Our results implicate that antibiotic resistance in the developing countries need to be monitored closely.

Epidemiology of glycopeptide-resistant enterococci colonizing high-risk patients in hospitals in Johannesburg, Republic of South Africa

Recent cases of infections caused by glycopeptide-resistant enterococci (GRE) have highlighted the emergence of these organisms in the Republic of South Africa. During May 1998 we conducted a prevalence study in four hospitals in Johannesburg and obtained 184 rectal swabs from patients identified as being at high risk for GRE colonization. Twenty enterococcal isolates showing various glycopeptide resistance genotypes were recovered: 3 Enterococcus faecium vanA isolates, 10 E. faecium vanB isolates, 6 E. gallinarum vanC1 isolates, and 1 E. avium vanA isolate. Macrorestriction analysis was used to demonstrate the clonal spread of GRE strains within hospitals. Evidence also demonstrated the likely persistence of the original E. faecium vanA isolate associated with the first confirmed death contributed to by GRE infection in South Africa in March 1997.

Emergence of vancomycin-resistant enterococci at a university hospital in Taiwan: persistence of multiple species and multiple clones

OBJECTIVES

To describe the epidemiology of vancomycin-resistant enterococci (VRE) in a university hospital in Taipei, Taiwan.

DESIGN

Retrospective review over a 27-month period, from March 1996 to May 1998.

SETTING

A tertiary-care teaching hospital in Taiwan.

PARTICIPANTS

Patients with VRE isolated from any body site.

METHODS

Patients were identified through hospital microbiology and infection control records. Patient charts were reviewed for clinical and epidemiology data, including age, gender, previous hospital admissions, underlying diseases, types of infection, and recent antibiotic use. VRE isolates were characterized by their typical biochemical reactions, cellular fatty acid profiles, and the presence of van genes. Antibiotypes using the E-test and randomly amplified polymorphic DNA (RAPD) patterns of these isolates were used to determine the clonality.

RESULTS

Twenty-five isolates of VRE recovered from 12 patients were identified. One patient with a perianal abscess had 12 isolates of VRE (4 Enterococcus faecalis, 7 Enterococcus faecium, and 1 Enterococcus casseliflavus) recovered from perianal lesions. Among 3 patients who were hospitalized in the same room, 1 had a community-acquired cellulitis over the left leg caused by E. faecalis, and the other 2 patients both had anal colonization with 2 isolates of E. faecalis. The other 8 patients had 1 E. faecalis isolate each from various clinical specimens. All isolates possessed vanA resistance phenotype and vanA genes. Different antibiotypes and RAPD patterns of the isolates from different patients excluded the possibility of nosocomial spread at the hospital.

CONCLUSIONS

Multiple species of VRE (E. faecalis, E. faecium, and E. casseliflavus) and multiple clones of E. faecium could colonize or infect hospitalized patients. In addition, clones of VRE can persist long-term in patients' lower gastrointestinal tracts. These results extend our knowledge of the coexistence and the persistence of multiple species and multiple clones of VRE in hospitalized patients.

Molecular epidemiology of vancomycin-resistant Enterococcus faecium in a large urban hospital over a 5-year period

To investigate the dissemination of vancomycin-resistant Enterococcus faecium (VREF) in a 728-bed tertiary-care hospital, all clinical VREF isolates recovered from June 1992 to June 1997 were typed by pulsed-field gel electrophoresis, and the transfer histories of the patients were documented. A total of 413 VREF isolates from urine (52%), wounds (16%), blood (11%), catheter tips (6%), and other sites (15%) were studied. VREF specimens mostly came from patients on wards (66%) but 34% came from patients in an intensive care unit. The number of VREF isolates progressively increased over time, with higher rates of isolation during the winter months and lower rates in the late summer months. Four distinct banding patterns were detected by pulsed-field gel electrophoresis among 316 samples (76%). Strain A (122 samples; 30%) appeared in June 1992 as the first VREF strain and was found until December 1994 throughout the entire hospital. Type B (92 samples; 22%) was initially detected in January 1994 and disappeared in November 1996. Strain C (10 samples; 2%) was limited to late 1996 and early 1997. Strain D (92 samples; 22%) showed two major peaks during March 1996 to August 1996 and January 1997 to February 1997. Unrelated strains (97 samples; 24%) appeared 1 year after the appearance of the first VREF isolate, and the numbers increased slightly over the years. Nosocomial acquisition (i.e., no known detection prior to admission and first isolation from cultures performed with samples retrieved >/=2 days after hospitalization) was found for 316 (91%) of 347 patients. Despite the implementation of Centers for Disease Control and Prevention guidelines, the proportion of related strains and high number of nosocomial cases of infection indicate a high transmission rate inside the hospital. The results imply an urgent need for stringent enforcement of more effective infection control measures.

The epidemiology of vancomycin-resistant enterococci

Major differences in the epidemiology of vanA carrying enterococci exist between Europe and the USA, where these organisms have been well investigated. These differences are probably related to the differences in antibiotic use in humans and animals in both continents, but more research is needed before firm conclusions can be drawn.

Enteric carriage of vancomycin-resistant Enterococcus faecium in patients tested for Clostridium difficile

OBJECTIVE

To identify independent risk factors for enteric carriage of vancomycin-resistant Enterococcus faecium (VREF) in hospitalized patients tested for Clostridium difficile toxin.

DESIGN

Retrospective case-cohort study.

SETTING

Tertiary-care teaching hospital.

PATIENTS

Convenience sample of 215 adult inpatients who had stool tested for C difficile between January 29 and February 25, 1996.

RESULTS

41 (19%) of 215 patients had enteric carriage of VREE Five independent risk factors for enteric VREF were identified: history of prior C difficile (odds ratio [OR], 15.21; 95% confidence interval [CI95], 3.30-70.10; P < .001), parenteral treatment with vancomycin for > or = 5 days (OR, 4.06; CI95, 1.54-10.73; P = .005), treatment with antimicrobials effective against gram-negative organisms (OR, 3.44; CI95, 1.20-9.87; P = .021), admission from another institution (OR, 2.95; CI95, 1.21-7.18; P =.017), and age > 60 years (OR 2.57; CI95, 1.13-5.82; P = .024). These risk factors for enteric VREF were independent of the patient's current C difficile status.

CONCLUSIONS

Antimicrobial exposures are the most important modifiable independent risk factors for enteric carriage of VREF in hospitalized patients tested for C difficile.

Vancomycin-resistant enterococci (VRE) colonization of high-risk patients in tertiary care Canadian hospitals. Canadian VRE Surveillance Group

We isolated 1487 Enterococcus species from 1200 stool specimens collected from high-risk patients in 12 Canadian tertiary care hospitals between October 1995 and November 1996. The composition of the 1487 isolates was 601 vancomycin-sensitive Enterococcus faecalis (40.4%), 667 vancomycin-sensitive Enterococcus faecium (44.9%), 18 vancomycin-resistant (nine isolates MIC 8-16 micrograms/mL; nine isolates MIC > or = 32 micrograms/mL) E. faecium (VREF) (1.2%), 95 vancomycin-sensitive Enterococcus gallinarum (6.4%), 29 vancomycin-resistant (all MICs 8-16 micrograms/mL) E. gallinarum (2.0%), and 77 vancomycin-sensitive Enterococcus casseliflavus (5.2%). Nine of the 18 VREF isolates collected possessed the vanA genotype and were from three patients at one hospital. Two other VREF isolates, of the vanB genotype, were from a single patient at a second hospital, and the remaining seven isolates, also all of the vanB genotype, were from five patients at a third hospital. All VREF were ampicillin resistant (MIC > or = 16 micrograms/mL), streptomycin resistant (MIC > 1000 micrograms/mL), and ciprofloxacin resistant (MIC > or = 4 micrograms/mL). Ten of the 18 VREF were also resistant to gentamicin (MIC > 500 micrograms/mL), while all 18 isolates had quinupristin/dalfopristin MICs < or = 0.5 microgram/mL. In conclusion, high-risk patients in tertiary care Canadian hospitals are rarely colonized (9/1200 patients, 0.75%) with VREF in their lower gastrointestinal tract. These findings correlate well with the lack of reported VREF infection in high-risk patients in Canadian hospitals. Quinupristin/dalfopristin demonstrated excellent in vitro activity against VREF and other non-faecalis species of Enterococcus, many of which also possessed high-level ampicillin, and/or high-level aminoglycoside, and/or ciprofloxacin resistance.

Outcome of a screening program for vancomycin-resistant enterococci in a hospital in Victoria

OBJECTIVE

To screen for faecal colonisation with vancomycin-resistant enterococci (VRE) among potentially at-risk patients.

DESIGN

Infection control screening program.

SETTING

Monash Medical Centre (a tertiary care hospital), Melbourne, Victoria, in the seven months from June 1997.

PATIENTS

Patients in the Renal, Oncology and Intensive Care (ICU) Units.

MAIN OUTCOME MEASURES

Presence of VRE in a rectal swab or faecal specimen taken at admission and at regular intervals during inpatient stay; presence of vancomycin-resistance genes (vanA, vanB and vanC) assessed by polymerase chain reaction (PCR); genetic clonality of isolates assessed by pulsed-field gel electrophoresis (PFGE).

RESULTS

574 patients (356 renal, 134 ICU and 84 oncology) were screened; 12 were colonised with VRE--nine renal inpatients, two having peritoneal dialysis or incentre haemodialysis, and one ICU patient. Nine isolates were Enterococcus faecalis (seven positive for vanB and two negative for all three resistance genes) and three were Enterococcus faecium (all positive for vanB). Eight were high-level gentamicin resistant. PFGE suggested genetic clonality between the index isolate and five other isolates from renal patients. No specific clinical practice was associated with VRE colonisation. Attempts to clear rectal carriage with oral ampicillin/amoxycillin or bacitracin were of limited success. Although antibiotic prescribing in the Renal Unit was generally consistent with defined protocols, use of vancomycin and third-generation cephalosporins has been further restricted.

CONCLUSIONS

Renal inpatients in our institution appear most at risk of VRE colonisation (4.6% overall) and therefore of VRE infection. Routine screening, especially of potentially high-risk patients, should be considered in major Australian hospitals.

Vancomycin-resistant enterococci: recent advances in genetics, epidemiology and therapeutic options

Vancomycin-resistant enterococci (VRE) have gained much attention in the last decade. Currently, there are five known types of vancomycin resistance based on genes encoding ligase enzymes that the organisms use to produce their cell wall precursors, namely, VanA, VanB, VanC, VanD and VanE. An additional unclassified type was discovered in Australia. The basis of resistance among these phenotypes appears to be similar in that the resistant organisms produce peptidoglycan precursors that end in moieties other than D-alanyl-D-alanine, the usual target of vancomycin. The other dipeptide-like termini identified to date include D-alanyl-D-lactate and D-alanyl-D-serine, which have low affinity for glycopeptides. Recent evidence suggests that glycopeptide-producing organisms might be the remote origin of the vancomycin resistance genes. In European countries, avoparcin, a glycopeptide used in farm animals as a growth promoter, has been linked to the occurrence of VRE and occasional common strains have been identified in food products, farm animals, healthy subjects and hospitalized patients. There have been no such reports in the USA where heavy use of vancomycin and use of broad spectrum antibiotics such as cephalosporins have been identified as important risk factors for acquisition of VRE. Transmission within the same or between hospitals has been reported in many countries. Infection control measures and efforts to use antibiotics, particularly vancomycin, more appropriately have been implemented in a number of healthcare facilities with varying degrees of success. Many antibiotics, as a single agent or a combination of drugs, as well as various new antibiotics have been tested in vitro, in animal models, or used in anecdotal cases but clinical data from large comparative trials are not available to date. Because of the limited susceptibility of many VRE to other agents, efforts to control these organisms are particularly important. Copyright 1999 Harcourt Publishers LtdCopyright 1999 Harcourt Publishers Ltd.

Intrinsically vancomycin-resistant gram-positive organisms: clinical relevance and implications for infection control

Intrinsic resistance to vancomycin in gram-positive bacteria presumably predates acquired vancomycin resistance in enterococci but it has only recently generated interest. Intrinsically resistant enterococci possessing the vanC gene and the non-enterococcal genera Leuconostoc, Lactobacillus, Pediococcus and Erysipelothrix are known to cause human infection. This review examines the available data on their identification, resistance mechanisms, epidemiology, clinical infections and antimicrobial susceptibility. Intrinsically vancomycin-resistant gram-positives are usually opportunistic pathogens. Although serious infections may occur, treatment options remain available. No additional infection control measures for the intrinsically resistant genera appear justified with currently available evidence, although vigilance should be maintained to detect future changes in susceptibility patterns.

Comparison of glycopeptide-resistant Enterococcus faecium isolates and glycopeptide resistance genes of human and animal origins

One hundred thirty-two glycopeptide-resistant Enterococcus faecium (GREF) isolates from different hospitals and pig and poultry farms in Belgium were compared on the basis of (i) their antibiotic susceptibilities, (ii) their SmaI pulsed-field gel electrophoresis (PFGE) patterns, and (iii) the organization of their Tn1546 or related elements in order to detect possible phenotypic and genotypic relationships among both groups of isolates. Human and animal vanA-positive GREF isolates were found to have similar susceptibility patterns; they remained susceptible to gentamicin and were, in general, susceptible to ampicillin. PFGE demonstrated a very high degree of genomic heterogeneity in both groups of isolates. However, indistinguishable isolates were found within different farms or hospitals, and in two instances, epidemiologically unrelated pig and human isolates showed indistinguishable PFGE patterns. In total, eight different transposon types were identified, and all were related to the prototype transposon Tn1546. The two predominant types, Tn1546 and type 2 transposons, which differed at three band positions, were present in both human and animal isolates. Type 2 transposons were significantly associated with pig isolates. The other types were seldom detected. These data suggest a possible exchange of glycopeptide resistance markers between animals and humans.

An interprovincial external quality assessment of the ability of Canadian laboratories to detect the vancomycin and penicillin resistance of Enterococcus faecium D366

OBJECTIVE: To evaluate the ability of Canadian laboratories to identify enterococci and detect low-level resistance to penicillin, ampicillin and vancomycin in five provinces and two territories by two external quality assessment schemes. METHODS: Enterococcus faecium, strain D366, with minimum inhibitory concentrations for vancomycin and penicillin of 32 and 16 mg/L respectively, was distributed during a routine proficiency survey. Laboratories were required to culture and identify the isolate and to test antimicrobial susceptibility. Participants were assessed against consensus reference values. RESULTS: Three hundred and sixty-four hospital, commercial and public-health laboratories participated, using their established procedures for patient samples. The isolate was identified to the species level by 222 (61%) laboratories and to the genus level by a further 98 participants. Forty-four failed to meet the expected standard. Vancomycin resistance was detected by 94%. Those reporting a falsely susceptible result used disk diffusion testing. Penicillin resistance was noted by 250 of 258 laboratories reporting on this agent. An incorrect ampicillin-susceptible finding was reported by 62 of 147 laboratories using automated microdilution or agar dilution methods. CONCLUSIONS: Most laboratories identified the isolate to an appropriate level. Detection of low-level vancomycin and penicillin resistance was achieved by the majority. Ampicillin resistance was less readily detected.

A randomized trial of surgical antimicrobial prophylaxis with and without vancomycin in organ transplant patients

BACKGROUND

Gram-positive organisms, including vancomycin-resistant enterococci (VRE), have emerged as major pathogens on the organ transplant service at our institution. We hypothesized that our use of vancomycin as part of routine surgical prophylaxis increased the risk of VRE colonization and infection; conversely, there was concern that failure to use vancomycin prophylaxis would increase peri-operative morbidity due to gram-positive organisms.

METHODS

Renal transplant recipients (n = 88) were randomized to receive either a) vancomycin/ceftriaxone or b) cefazolin; and pancreas transplants (n = 24) to receive either a) vancomycin/gentamicin or b) cefazolin/gentamicin. Stool samples or rectal swabs were obtained for culture for enterococci within 24 h of transplantation and weekly while hospitalized.

RESULTS

Enterococci were isolated on stool culture from 38 (34%) of 102 patients at the time of transplantation; 4 (11%) of the isolates were VRE. The percentage of patients who subsequently acquired VRE was low (1-7% per wk) but remained constant during hospitalization. There was no association between new VRE detection and vancomycin use for either prophylactic or therapeutic purposes. Forty-four patients (39%) had a post-operative infection with 46% of these infections due to gram-positive organisms; rates were unaffected by prophylactic vancomycin use. Pancreas transplant patients who did not receive vancomycin prophylaxis had a significantly longer initial hospitalization (p = 0.03); however, differences were not statistically significant when total length of stay (LOS) within the first 90 d of transplantation was compared.

CONCLUSIONS

Vancomycin surgical prophylaxis does not appear to have an effect on VRE colonization or infection, or on rates of infection with gram-positive bacteria. Elimination of vancomycin prophylaxis in renal transplant patients may be a reasonable part of an overall program to limit vancomycin usage, although as a single measure, its impact may be minimal. Vancomycin surgical prophylaxis may be of greater importance in pancreas transplants.

In vitro and in vivo antibacterial activities of a novel glycylcycline, the 9-t-butylglycylamido derivative of minocycline (GAR-936)

The 9-t-butylglycylamido derivative of minocycline (TBG-MINO) is a recently synthesized member of a novel group of antibiotics, the glycylcyclines. This new derivative, like the first glycylcyclines, the N,N-dimethylglycylamido derivative of minocycline and 6-demethyl-6-deoxytetracycline, possesses activity against bacterial isolates containing the two major determinants responsible for tetracycline resistance: ribosomal protection and active efflux. The in vitro activities of TBG-MINO and the comparative agents were evaluated against strains with characterized tetracycline resistance as well as a spectrum of recent clinical aerobic and anaerobic gram-positive and gram-negative bacteria. TBG-MINO, with an MIC range of 0.25 to 0.5 microgram/ml, showed good activity against strains expressing tet(M) (ribosomal protection), tet(A), tet(B), tet(C), tet(D), and tet(K) (efflux resistance determinants). TBG-MINO exhibited similar activity against methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant streptococci, and vancomycin-resistant enterococci (MICs at which 90% of strains are inhibited, < or = 0.5 microgram/ml). TBG-MINO exhibited activity against a wide diversity of gram-negative aerobic and anaerobic bacteria, most of which were less susceptible to tetracycline and minocycline. The in vivo protective effects of TBG-MINO were examined against acute lethal infections in mice caused by Escherichia coli, S. aureus, and Streptococcus pneumoniae isolates. TBG-MINO, administered intravenously, demonstrated efficacy against infections caused by S. aureus including MRSA strains and strains containing tet(K) or tet(M) resistance determinants (median effective doses [ED50s], 0.79 to 2.3 mg/kg of body weight). TBG-MINO demonstrated efficacy against infections caused by tetracycline-sensitive E. coli strains as well as E. coli strains containing either tet(M) or the efflux determinant tet(A), tet(B), or tet(C) (ED50s, 1.5 to 3.5 mg/kg). Overall, TBG-MINO shows antibacterial activity against a wide spectrum of gram-positive and gram-negative aerobic and anaerobic bacteria including strains resistant to other chemotherapeutic agents. The in vivo protective effects, especially against infections caused by resistant bacteria, corresponded with the in vitro activity of TBG-MINO.