Cost-effectiveness of universal prophylaxis in pregnancy with prior group B streptococci colonization.

OBJECTIVE: To estimate the costs and outcomes of rescreening for group B streptococci (GBS) compared to universal treatment of term women with history of GBS colonization in a previous pregnancy. STUDY DESIGN: A decision analysis model was used to compare costs and outcomes. Total cost included the costs of screening, intrapartum antibiotic prophylaxis (IAP), treatment for maternal anaphylaxis and death, evaluation of well infants whose mothers received IAP, and total costs for treatment of term neonatal early onset GBS sepsis. RESULTS: When compared to screening and treating, universal treatment results in more women treated per GBS case prevented (155 versus 67) and prevents more cases of early onset GBS (1732 versus 1700) and neonatal deaths (52 versus 51) at a lower cost per case prevented ($8,805 versus $12,710). CONCLUSION: Universal treatment of term pregnancies with a history of previous GBS colonization is more cost-effective than the strategy of screening and treating based on positive culture results.

Clinical decisions related to CBC screening of asymptomatic full-term infants at risk for group B streptococcus disease

Objective. Although complete blood count (CBC) changes occur with the development of clinical sepsis in newborns, the CBC has not been reported to be a sensitive predictor of sepsis in asymptomatic full-term newborn infants, nor has it been reported to be related to risk factors for sepsis or clinical decisions. The objective of this study was to evaluate the relationship between the WBC/I:T (immature:total neutrophil) ratio and maternal group B streptococcal (GBS) risk factors (rupture of membranes ≥18 hours, maternal temperature ≥100.4°F, maternal age ≤20 years, previous infant with invasive GBS disease, maternal GBS bacteriuria, and black ethnicity); and to evaluate the relationship between the WBC/I:T ratios and providers' clinical decisions (observe versus repeat the CBC or complete sepsis evaluation) in the asymptomatic full-term newborn at risk for early-onset GBS sepsis. ^ Methods. Medical records of infants admitted to the well baby nursery at a tertiary care teaching hospital in Houston, TX between 1/1/99 and 12/31/00 whose gestational ages were ≥35 weeks; who had mothers with GBS positive or unknown culture status and inadequate intrapartum antibiotic prophylaxis; and who had screening CBCs performed in the first 30 hours of life because of GBS risk were reviewed (n = 412). Demographic information, maternal GBS risk factors, CBC results, clinical decisions, and rationales for clinical decisions were collected. ^ Results. With the exception of black ethnicity (p = .0000, odds ratio = 0.213), no statistically significant differences in risk factors between infants with normal and abnormal WBC counts or normal and abnormal I:T ratios were found. Infants with abnormal WBCs had a significantly higher likelihood of having a CBC repeated (p = 0.002 for WBC). Providers documented the CBC result in the rationale for clinical decisions in 62% of the cases. ^ Conclusion. The CBC results were not related to maternal risk factors for GBS except for ethnicity. Black infants had significantly lower WBC levels than infants of other ethnicities, although this difference was clinically insignificant. Infants with abnormal WBCs had a significantly higher likelihood of undergoing repeat CBCs but not sepsis evaluations. Provider rationale was difficult to evaluate due to insufficient documentation. The screening CBC result did not impact the clinicians' decisions to initiate sepsis evaluations in this population. ^

Persisting abdominal symptoms after travelers' diarrhea: Is there a genetic predisposition?

Functional gastrointestinal disorders (FGIDs) are defined as ailments of the mid or lower gastrointestinal tract which are not attributable to any discernable anatomic or biochemical defects.1 FGIDs include functional bowel disorders, also known as persisting abdominal symptoms (PAS). Irritable bowel syndrome (IBS) is one of the most common illnesses classified under PAS.2,3 This is the first prospective study that looks at the etiology and pathogenesis of post-infectious PAS in the context of environmental exposure and genetic susceptibility in a cohort of US travelers to Mexico. Our objective was to identify infectious, genetic and environmental factors that predispose to post infectious PAS. ^ Methods. This is a secondary data analysis of a prospective study on a cohort of 704 healthy North American tourists to Cuernavaca, Morelos and Guadalajara, Jalisco in Mexico. The subjects at risk for Travelers' diarrhea were assessed for chronic abdominal symptoms on enrollment and six months after the return to the US. ^ Outcomes. PAS was defined as disturbances of mid and lower gastrointestinal system without any known pathological or radiological abnormalities, or infectious, or metabolic causes. It refers to functional bowel disease, category C of functional gastrointestinal diseases as defined by the Rome II criterion. PAS was sub classified into Irritable bowel syndrome (IBS) and functional abdominal disease (FAD). ^ IBS is defined as recurrent abdominal pain or discomfort present at least 25% and associated with improvement with defecation, change in frequency and form of stool. FAD encompasses other abdominal symptoms of chronic nature that do not meet the criteria for IBS. It includes functional diarrhea, functional constipation, functional bloating: and unspecified bowel symptoms. ^ Results. Among the 704 travelers studied, there were 202 cases of PAS. The PAS cases included 175 cases of FAD and 27 cases of IBS. PAS was more frequent among subjects who developed traveler's diarrhea in Mexico compared to travelers who remained healthy during the short term visit to Mexico (52 vs. 38; OR = 1.8; CI, 1.3–2.5, P < 0.001). A statistically significant difference was noted in the mean age of subjects with PAS compared to healthy controls (28 vs. 34 yrs; OR = 0.97, CI, 0.95–0.98; P < 0.001). Travelers who experienced multiple episodes, a later onset of diarrhea in Mexico and passed greater numbers of unformed stools were more likely to be identified in PAS group at six months. Participants who developed TD caused by enterotoxigenic E.coli in Mexico showed a 2.6 times higher risk of developing FAD (P = 0.003). Infection with Providencia ssp. also demonstrated a greater risk to developing PAS. Subjects who sought treatment for diarrhea while in Mexico also displayed a significantly lower frequency of IBS at six months follow up (OR = 0.30; CI, 0.10–0.80; P = 0.02). ^ Forty six SNPs belonging to 14 genes were studied. Seven SNPs were associated with PAS at 6 months. These included four SNPs from the Caspase Recruitment Domain-Containing Protein 15 gene (CARD15), two SNPs from Surfactant Pulmonary-Associated Protein D gene (SFTPD) and one from Decay-Accelerating Factor For Complement gene (CD55). A genetic risk score (GRS) was composed based on the 7 SNPs that showed significant association with PAS. A 20% greater risk for PAS was noted for every unit increase in GRS. The risk increased by 30% for IBS. The mean GRS was high for IBS (2.2) and PAS (1.1) compared to healthy controls (0.51). These data suggests a role for these genetic polymorphisms in defining the susceptibility to PAS. ^ Conclusions. The study allows us to identify individuals at risk for developing post infectious IBS (PI-IBS) and persisting abdominal symptoms after an episode of TD. The observations in this study will be of use in developing measures to prevent and treat post-infectious irritable bowel syndrome among travelers including pre-travel counseling, the use of vaccines, antibiotic prophylaxis or the initiation of early antimicrobial therapy. This study also provides insights into the pathogenesis of post infectious PAS and IBS. (Abstract shortened by UMI.)^

Analysis of clonality and antibiotic resistance among early clinical isolates of Enterococcus faecium in the United States.

BACKGROUND: The Enterococcus faecium genogroup, referred to as clonal complex 17 (CC17), seems to possess multiple determinants that increase its ability to survive and cause disease in nosocomial environments. METHODS: Using 53 clinical and geographically diverse US E. faecium isolates dating from 1971 to 1994, we determined the multilocus sequence type; the presence of 16 putative virulence genes (hyl(Efm), esp(Efm), and fms genes); resistance to ampicillin (AMP) and vancomycin (VAN); and high-level resistance to gentamicin and streptomycin. RESULTS: Overall, 16 different sequence types (STs), mostly CC17 isolates, were identified in 9 different regions of the United States. The earliest CC17 isolates were part of an outbreak that occurred in 1982 in Richmond, Virginia. The characteristics of CC17 isolates included increases in resistance to AMP, the presence of hyl(Efm) and esp(Efm), emergence of resistance to VAN, and the presence of at least 13 of 14 fms genes. Eight of 41 of the early isolates with resistance to AMP, however, were not in CC17. CONCLUSIONS: Although not all early US AMP isolates were clonally related, E. faecium CC17 isolates have been circulating in the United States since at least 1982 and appear to have progressively acquired additional virulence and antibiotic resistance determinants, perhaps explaining the recent success of this species in the hospital environment.

Cotransfer of antibiotic resistance genes and a hylEfm-containing virulence plasmid in Enterococcus faecium.

The hyl(Efm) gene (encoding a putative hyaluronidase) has been found almost exclusively in Enterococcus faecium clinical isolates, and recently, it was shown to be on a plasmid which increased the ability of E. faecium strains to colonize the gastrointestinal tract. In this work, the results of mating experiments between hyl(Efm)-containing strains of E. faecium belonging to clonal cluster 17 and isolated in the United States and Colombia indicated that the hyl(Efm) gene of these strains is also carried on large plasmids (>145 kb) which we showed transfer readily from clinical strains to E. faecium hosts. Cotransfer of resistance to vancomycin and high-level resistance (HLR) to aminoglycosides (gentamicin and streptomycin) and erythromycin was also observed. The vanA gene cluster and gentamicin resistance determinants were genetically linked to hyl(Efm), whereas erm(B) and ant(6)-I, conferring macrolide-lincosamide-streptogramin B resistance and HLR to streptomycin, respectively, were not. A hyl(Efm)-positive transconjugant resulting from a mating between a well-characterized endocarditis strain [TX0016 (DO)] and a derivative of a fecal strain of E. faecium from a healthy human volunteer (TX1330RF) exhibited increased virulence in a mouse peritonitis model. These results indicate that E. faecium strains use a strategy which involves the recruitment into the same genetic unit of antibiotic resistance genes and determinants that increase the ability to produce disease. Our findings indicate that the acquisition of the hyl(Efm) plasmids may explain, at least in part, the recent successful emergence of some E. faecium strains as nosocomial pathogens.

Acquisition of a natural resistance gene renders a clinical strain of methicillin-resistant Staphylococcus aureus resistant to the synthetic antibiotic linezolid.

Linezolid, which targets the ribosome, is a new synthetic antibiotic that is used for treatment of infections caused by Gram-positive pathogens. Clinical resistance to linezolid, so far, has been developing only slowly and has involved exclusively target site mutations. We have discovered that linezolid resistance in a methicillin-resistant Staphylococcus aureus hospital strain from Colombia is determined by the presence of the cfr gene whose product, Cfr methyltransferase, modifies adenosine at position 2503 in 23S rRNA in the large ribosomal subunit. The molecular model of the linezolid-ribosome complex reveals localization of A2503 within the drug binding site. The natural function of cfr likely involves protection against natural antibiotics whose site of action overlaps that of linezolid. In the chromosome of the clinical strain, cfr is linked to ermB, a gene responsible for dimethylation of A2058 in 23S rRNA. Coexpression of these two genes confers resistance to all the clinically relevant antibiotics that target the large ribosomal subunit. The association of the ermB/cfr operon with transposon and plasmid genetic elements indicates its possible mobile nature. This is the first example of clinical resistance to the synthetic drug linezolid which involves a natural resistance gene with the capability of disseminating among Gram-positive pathogenic strains.

Eluding antibiotic resistance: capitalizing on antimicrobial peptides interaction with the lipid bilayer

It is widely accepted that the emergence of drug-resistant pathogens is the result of the overuse and misuse of antibiotics. Infectious Disease Society of America, Center for Disease Control and World Health Organization continue to view, with concern, the lack of antibiotics in development, especially those against Gram-negative bacteria. Antimicrobial peptides (AMPs) have been proposed as an alternative to antibiotics due to their selective activity against microbes and minor ability to induce resistance. For example, the Food and Drug Administration approved Daptomycin (DAP) in 2003 for treatment of severe skin infections caused by susceptible Gram-positive organisms. Currently, there are 12 to 15 examples of modified natural and synthetic AMPs in clinical development. But most of these agents are against Gram-positive bacteria. Therefore, there is unmet medical need for antimicrobials used to treat infections caused by Gram-negative bacteria. In this study, we show that a pro-apoptotic peptide predominantly used in cancer therapy, (KLAKLAK)2, is an effective antimicrobial against Gram-negative laboratory strains and clinical isolates. Despite the therapeutic promise, AMPs development is hindered by their susceptibility to proteolysis. Here, we demonstrate that an all-D enantiomer of (KLAKLAK)2, resistant to proteolysis, retains its activity against Gram-negative pathogens. In addition, we have elucidated the specific site and mechanism of action of D(KLAKLAK)2 through a repertoire of whole-cell and membrane-model assays. Although it is considered that development of resistance does not represent an obstacle for AMPs clinical development, strains with decreased susceptibility to these compounds have been reported. Staphylococci resistance to DAP was observed soon after its approval for use and has been linked to alterations of the cell wall (CW) and cellular membrane (CM) properties. Immediately following staphylococcal resistance, Enterococci resistance to DAP was seen, yet the mechanism of resistance in enterococci remains unknown. Our findings demonstrate that, similar to S. aureus, development of DAP-resistance in a vancomycin-resistant E. faecalis isolate is associated with alterations of the CW and properties of the CM. However, the genes linked to these changes in enterococci appear to be different from those described in S. aureus.

The impact of antibiotic associated diarrhea on health related quality of life in hospitalized patients

Objective. To determine the impact of antibiotic associated diarrhea (AAD) on health related quality of life (HRQOL) in hospitalized patients compared to matched controls without diarrhea. ^ Methods. This is a hospital-based, matched case-control study using secondary data from a prospective cohort trial of patients receiving broad-spectrum antibiotics. One hundred and seventy-eight patients were recruited of whom 18 (10%) reported having antibiotic associated diarrhea. Two non-diarrhea controls were selected for each case with diarrhea giving a final sample of 18 cases and 36 controls. Responses from Short Form (SF) 36 questionnaire were aggregated into eight domains including physical functioning (PF), role-functioning physical (RP), bodily pain (BP), general health (GH), social functioning (SF), vitality (VT), role-functioning emotional (RE), and mental health (MH). The eight domains were compared between cases and controls. A GI targeted HRQOL measure was administered to 13 patients with AAD. Responses from the disease-specific instrument were combined in eight subscale scores: dysphoria, interference with activity, body image, health worry, food avoidance, social reaction, sex, and relationships. ^ Results. The sample consisted of 41 females (75.9%) and 13 males (24.1%) aged 53.5 ± 14.4 years (range: 21-76 years). Twenty five patients (46%) were Caucasian, 15 (27%) were African American, 13(24%) were Hispanic and 1(2%) was Asian. In univariate analysis, no significant differences in quality of life outcomes were observed in each of the SF36 domains between the case patients and matched controls. There were trends for decreased scores on the role-functioning physical, bodily pain, general health, social functioning, mental health, and mental summary domains. In total, 7 of 8 domain scores were lower in patients with AAD and 5 of 8 domain scores were lower by more than 5 points (considered clinically significant). Controlling for age, patients with antibiotic associated diarrhea had significantly lower general health, vitality, and mental health scale scores (p<0.05 each). The disease-specific scores were significantly lower in patients with AAD than those in published norms for irritable bowel syndrome patients. ^ Conclusion. In this small sample, several areas of decreased QOL in patients with AAD compared to matched controls were noted. A larger sample size to validate these results is necessary.^

Antibiotic susceptibility and resistance among bacterial enteropathogens isolated from international travelers to Mexico, Guatemala, and India, 2006--2008

The incidence rates of travelers' diarrhea (TD) have remained unchanged for the last fifty years. More recently, there have been increasing recommendations for self-initiated therapy and even prophylactic therapy for TD. There is no recent data on the in vitro activities of commonly used antibiotics for TD therapy and whether there have been any changes in susceptibilities over the last ten years. 456 enteropathogens were isolated from adult travelers to Mexico, India, and Guatemala between the years 2006 to 2008. MICs were determined for 10 different antimicrobials by the agar dilution method. Traditional antibiotics such as ampicillin, trimethoprim/sulfamethoxazole, and doxycycline continue to show high levels of resistance. Current first line antibiotic agents including fluoroquinolones and azithromycin had significantly higher MICs when compared to 10 years ago and MIC90 levels were beyond the CSLI cutoffs for resistance. There were significant geographical differences in resistance patterns when comparing Central America with India. Entertoxigenic Escherichia coli (ETEC) isolates were more resistant to ciprofloxacin (p=0.023), and levofloxacin (p=0.0078) in India; whereas, enteroaggregative Escherichia coli (EAEC) isolates from Central America showed more resistance. When compared to MICs of isolates 10 years prior, there was a four to ten-fold increase in MIC90s for ceftriaxone, ciprofloxacin, levofloxacin and azithromycin for both ETEC and EAEC. There were no significant changes in rifaximin MICs over the last ten years, which makes it a promising agent for TD. Rising MICs over time implicate the need for continuous surveillance of susceptibility patterns worldwide and for geography specific recommendations in TD therapy.^

Importance of antibiotic class to the development of Clostridium difficile infection (CDI) in adults: A systematic review

C. difficile causes gastrointestinal infections in humans, including severe diarrhea. It is implicated in 20%-30% of cases of antibiotic-associated diarrhea, in 50%-70% of cases of antibiotic-associated colitis, and in >90% of cases of antibiotic-associated pseudomembranous colitis. Exposure to antimicrobial agent, hospitalization and age are some of the risk factors that predispose to CDI. Virtually all hospitalized patients with nosocomially-acquired CDI have a history of treatment with antimicrobials or neoplastic agent within the previous 2 months. The development of CDI usually occurs during treatment with antibiotics or some weeks after completing the course of the antibiotics. ^ After exposure to the organism (often in a hospital), the median incubation period is less than 1 week, with a median time of onset of 2days. The difference in the time between the use of antibiotic and the development of the disease relate to the timing of exogenous acquisition of C. difficile. ^ This paper reviewed the literature for studies on different classes of antibiotics in association with the rates of primary CDI and RCDI from the year 1984 to 2012. The databases searched in this systematic review were: PubMed (National Library of Medicine) and Medline (R) (Ovid). RefWorks was used to store bibliographic data. ^ The search strategy yielded 733 studies, 692 articles from Ovid Medline (R) and 41 articles from PubMed after removing all duplicates. Only 11 studies were included as high quality studies. Out of the 11 studies reviewed, 6 studies described the development of CDI in non-CDI patients taking antibiotics for other purposes and 5 studies identified the risk factors associated with the development of recurrent CDI after exposure to antibiotics. ^ The risk of developing CDI in non-CDI patients receiving beta lactam antibiotics was 2.35%, while fluoroquinolones, clindamycin/macrolides and other antibiotics were associated with 2.64%, 2.54% and 2.35% respectively. Of those who received beta lactam antibiotic, 26.7% developed RCDI, while 36.8% of those who received any fluoroquinolone developed RCDI, 26.5% of those who received either clindamycin or macrolides developed RCDI and 29.1% of those who received other antibiotics developed RCDI. Continued use of non-C. difficile antibiotics especially fluoroquinolones was identified as an important risk factor for primary CDI and recurrent CDI. ^

Does prior receipt of a rifamycin antibiotic increase the risk of acquiring an infection due to a rifamycin-resistant strain of Clostridium difficile?

Objectives. To examine the association between prior rifamycin exposure and later development of C. difficile infection (CDI) caused by a rifamycin-resistant strain of C. difficile , and to compare patient characteristics between rifamycin-resistant strains of C. difficile infection and rifamycin-susceptible strains of C. difficile infection. ^ Methods. A case-control study was performed in a large university-affiliated hospital in Houston, Texas. Study subjects were patients with C. difficile infection acquired at the hospital with culture-positive isolates of C. difficile with which in vitro rifaximin and rifampin susceptibility has been tested. Prior use of rifamycin, demographic and clinical characteristics was compared between case and control groups using univariate statistics. ^ Results. A total of 49 C. difficile strains met the study inclusion criteria for rifamycin-resistant case isolates, and a total of 98 rifamycin-susceptible C. difficile strains were matched to case isolates. Of 49 case isolates, 12 (4%) were resistant to rifampin alone, 12 (4%) were resistant to rifaximin alone, and 25 (9%) were resistant to both rifampin and rifaximin. There was no significant association between prior rifamycin use and rifamycin-resistant CDI. Cases and controls did not differ according to demographic characteristics, length of hospital stay, known risk factors of CDI, type of CDI-onset, and pre-infection medical co-morbidities. Our results on 37 rifaximin-resistant isolates (MIC ≥32 &mgr;g/ml) showed more than half of isolates had a rifaximin MIC ≥256 &mgr;g/ml, and out of these isolates, 19 isolates had MICs ≥1024 &mgr;g/ml. ^ Conclusions. Using a large series of rifamycin-non-susceptible isolates, no patient characteristics were independently associated with rifamycin-resistant CDI. This data suggests that factors beyond previous use of rifamycin antibiotics are primary risk factors for rifamycin-resistant C. difficile. ^

Rifaximin-mediated changes to the epithelial cell proteome: 2-D gel analysis

Diarrhea remains a significant cause of worldwide morbidity and mortality. Over 4 million children die of diarrhea annually. Although antibiotics can be used as prophylaxis or for treatment of diarrhea, concern remains over antibiotic resistance. Rifaximin is a semi-synthetic rifamycin derivative that can be used to treat symptoms of infectious diarrhea, inflammatory bowel syndrome, bacterial overgrowth of the small bowel, pouchitis, and fulminant ulcerative colitis. Rifaximin is of particular interest because it is poorly adsorbed in the intestines, shows no indication of inducing bacterial resistance, and has minimal effect on intestinal flora. In order to better understand how rifaximin functions, we sought to compare the protein expression profile of cells pretreated with rifaximin, as compared to cells treated with acetone, rifamycin (control antibiotic), or media (untreated). 2-D gel electrophoresis identified 38 protein spots that were up- or down-regulated by over 2-fold in rifaximin treated cells compared to controls. 16 of these spots were down-regulated, including keratin, annexin A5, intestinal-type alkaline phosphatase, histone h4, and histone-binding protein RbbP4. 22 spots were up-regulated, including heat shock protein HSP 90 alpha, alkaline phosphatase, and fascin. Many of the identified proteins are associated with cell structure and cytoskeleton, transcription and translation, and cellular metabolism. A better understanding of the functionality of rifaximin will identify additional potential uses for rifaximin and determine for whom the drug is best suited. ^

Pathogenesis of antibiotic-associated diarrhea (AAD)---a systematic review

A common complication of antibiotic use is the development of diarrheal illness. The pathogenesis of antibiotic associated diarrhea (AAD) may be mediated through alteration of intestinal microbiota, overgrowth of opportunistic pathogens, and direct drug toxicity on the gut. Alterations in the intestinal microbiota result in metabolic imbalances, loss of colonization resistance and in turn allow proliferation of opportunistic pathogens. Currently less than 33% of AAD cases can be attributable to Clostridium difficile leaving a large number of cases undiagnosed and poorly treated. Although the pathogenesis of Clostridium difficile infection (CDI) has been well documented, the role of other putative microbial etiologies (Clostridium perfringens, Staphylococcus aureus, Klebsiella oxytoca, Candida species) and their pathogenic mechanisms in AAD has been unclear. This review provides a comprehensive and systematic approach to the existing data on AAD and includes concise descriptions of the pathogenesis of CDI and non-CDI AAD in the form of figures.^

Clostridium difficile infection (CDI): Clinical outcomes associated with concomitant non-CDI antibiotic use

This research examined the relationship between concomitant non-CDI antibiotic use and complications arising due to Clostridium difficile infection. To observe the hypothesized association, 160 total CDI patients between the ages of 50-90 were selected, 80 exposed to concomitant antibiotics and 80 unexposed. Samples were matched based upon their age and Horn's index, a severity score for underlying illness. Patients were de-identified by a third party, and analyzed retrospectively for differences between the two groups. In addition, patients exposed to broad spectrum antibiotics at the time of CDI treatment were further studied to demonstrate whether antibiotics had any effect on CDI complications. Between the two groups, the outcomes of interest (recurrent CDI, refractory CDI, mortality, ICU stay, and length of hospitalization) were not associated with concomitant antibiotic use at the time of CDI therapy. However, within the exposed population, certain classes of antibiotics such as cephalosporin, antifungals, and tetracyclines were more common in patients compared to other types of therapy. In addition, days of therapy provided evidence that sustained use of antibiotics affected CDI (p = 0.08), although a more robust sample size and additional study would be needed. Finally, refractory CDI was found to be potentially overestimated within the exposed population due to the possibility of antibiotic-associated diarrhea.^

Design, synthesis and cellular and molecular pharmacology of 2$\sp\prime$-bromo-4$\sp\prime$-epidaunorubicin (WP401): A novel non-cross-resistant anthracycline antibiotic with the intrinsic ability to circumvent P -glycoprotein-mediated drug resistance

We designed and synthesized a novel daunorubicin (DNR) analogue that effectively circumvents P-glycoprotein (P-gp)-mediated drug resistance. The fully protected carbohydrate intermediate 1,2-dibromoacosamine was prepared from acosamine and effectively coupled to daunomycinone in high yield. Deprotection under alkaline conditions yielded 2$\sp\prime$-bromo-4$\sp\prime$-epidaunorubicin (WP401). The in vitro cytotoxicity and cellular and molecular pharmacology of WP401 were compared with those of DNR in a panel of wild-type cell lines (KB-3-1, P388S, and HL60S) and their multidrug-resistant (MDR) counterparts (KB-V1, P388/DOX, and HL60/DOX). Fluorescent spectrophotometry, flow cytometry, and confocal laser scanning microscopy were used to measure intracellular accumulation, retention, and subcellular distribution of these agents. All MDR cell lines exhibited reduced DNR uptake that was restored, upon incubation with either verapamil (VER) or cyclosporin A (CSA), to the level found in sensitive cell lines. In contrast, the uptake of WP401 was essentially the same in the absence or presence of VER or CSA in all tested cell lines. The in vitro cytotoxicity of WP401 was similar to that of DNR in the sensitive cell lines but significantly higher in resistant cell lines (resistance index (RI) of 2-6 for WP401 vs 75-85 for DNR). To ascertain whether drug-mediated cytotoxicity and retention were accompanied by DNA strand breaks, DNA single- and double-strand breaks were assessed by alkaline elution. High levels of such breaks were obtained using 0.1-2 $\mu$g/mL of WP401 in both sensitive and resistant cells. In contrast, DNR caused strand breaks only in sensitive cells and not much in resistant cells. We also compared drug-induced DNA fragmentation similar to that induced by DNR. However, in P-gp-positive cells, WP401 induced 2- to 5-fold more DNA fragmentation than DNR. This increased DNA strand breakage by WP401 was correlated with its increased uptake and cytotoxicity in these cell lines. Overall these results indicate that WP401 is more cytotoxic than DNR in MDR cells and that this phenomenon might be related to the reduced basicity of the amino group and increased lipophilicity of WP401. ^