The 2002 Chandigarh cholera outbreak revisited: utility of MALDI-TOF as a molecular epidemiology tool

In July 2002, an outbreak of cholera occurred in north India with two separate geographical foci. Pulsed field gel electrophoresis (PFGE) was previously used in typing a representative sample of these isolates. This study evaluates the usefulness of MALDI-TOF as an epidemiological tool for typing Vibrio cholerae isolates in comparison with PFGE and Amplified fragment length polymorphisms (AFLP). Forty-six isolates of V. cholerae isolated from stool of patients affected in the July 2002 outbreak were typed using MALDI-TOF. To validate its utility, clinical and environmental isolates previously characterized by PFGE and AFLP were included for dendrogram analysis. All 46 isolates were correctly identified by MALDI-TOF to species level. Two distinct clades appeared on dendrogram using MALDI-TOF corresponding to the two geographical foci of the outbreak. For the study of evolution of organisms from environment, AFLP was superior as it clearly demarcated clinical and environmental isolates. The outbreak was not due to a single clone but due to multiple clones circulating simultaneously, as was seen with PFGE also.

SIGNIFICANCE AND IMPACT OF THE STUDY

MALDI-TOF appears to be a highly discriminatory, cost-effective and rapid epidemiological typing technique that can be used in the investigation of cholera outbreaks.

Free living amoebae in water sources of critical units in a tertiary care hospital in India

BACKGROUND

Isolation of free-living amoebae (FLA) is reported sparsely from water taps, ventilators, air conditioners, haemodialysis units and dental irrigation systems of hospitals worldwide. Their prevalence in hospital environment especially in wards having immunocompromised patients may pose a risk to this group of susceptible population as they may cause disease themselves or may carry pathogens inside them. No study from India has performed such surveillance.

OBJECTIVE

To evaluate extent of FLA contamination in water sources of bone marrow transplant (BMT) intensive care unit (ICU), transplant ICU, haemodialysis unit and high dependency unit in a tertiary care hospital in India.

MATERIALS AND METHODS

A total of hundred samples including fifty each of tap water samples and swabs from mouth of taps used for drinking, bathing and hand washing purposes in these units were collected according to standard procedure. Samples were inoculated onto non-nutrient agar plates at room temperature followed by morphological confirmation. Molecular identification including polymerase chain reaction (PCR) and sequencing was performed in culture positive samples.

RESULTS

Four tap water samples and ten swab samples showed growth of trophozoites and cyst formation. Morphologically, four amoebae resembled Acanthamoeba spp. which was further confirmed by PCR and sequencing showed them to be of T3 and T4 genotypes.

CONCLUSION

The presence of these FLA in hospital water sources emphasises the urgent need of implementing effective preventive measures. Further studies are required to estimate the true prevalence of FLA in Indian hospitals by taking larger number of samples.

Utility of whole-cell repetitive extragenic palindromic sequence-based PCR (REP-PCR) for the rapid detection of nosocomial outbreaks of multidrug resistant organisms: experience at a tertiary care center in North India

BACKGROUND

There is a huge need to develop molecular typing methods which are simple to perform, rapid and cost effective to confirm clonality of nosocomial isolates in outbreak situations.

OBJECTIVES

The aim of the study was to investigate a hospital outbreak of multi-drug resistant (MDR) Klebsiellapneumoniae septicemia in a paediatric surgery intensive care unit (PSICU) using a repetitive extragenic palindromic polymerase chain reaction (REP-PCR).

MATERIALS AND METHODS

MDR Klebsiella pneumoniae isolates from an outbreak of nosocomial sepsis were typed byREP-PCR using consensus primers. Isolates from different intensive care units (ICUs) but with similar antibiogram were also genotyped for comparison.

RESULTS AND CONCLUSION

A cluster of twelve MDR K Pneumoniae septicemia cases was identified at the PSICU by genotyping using REP-PCR. Surveillance cultures failed to pick up any source of infection. REP-PCR was found to be a rapid and simple tool for investigation outbreaks in hospitals. Due to early detection we could initiate infection control practices with focus on hand washing and prevent the further transmission of the organism.

Pyonephrosis due to Chryseobacterium gleum: a first case report

Chryseobacterium spp are widely distributed in nature but data of their isolation from clinical samples is scanty. Here, we report the first case of AmpC producing C. gleum causing pyonephrosis in a patient having bilateral nephrolithiasis on double J (DJ) stent. The present isolate was resistant to vancomycin, erythromycin, clindamycin, carbapenems and ciprofloxacin and susceptible to tetracycline and minocycline. The patient was treated with tetracycline and recovered without the need for removal of the DJ stent. The environmental surveillance carried out to trace the nosocomial origin of the isolate was negative. Since antimicrobial susceptibility of this isolate is different from previous reports, we emphasise that in vitro susceptibility testing should be sought to choose optimal antimicrobial agents for these Nonfermentative Gram-Negative Bacilli (NFGNBs) with different susceptibility patterns.

Mandatory public reporting of healthcare-associated infections in developed countries: how can developing countries follow?

The threat posed by increased transmission of drug-resistant pathogens within healthcare settings and from healthcare settings to the community is very real and alarming. Although the developed world has taken strong steps to curb this menace, there has been little pressure on developing countries to take any corrective action. If the reporting of alarming rates of healthcare-associated infections (HCAIs) from hospitals in India and many other developing countries was made mandatory, it would help to force stakeholders (e.g. healthcare workers, legislators, administrators and policy makers in hospitals) to acknowledge and tackle the problem. This would introduce quality control in a long neglected area of health care, and enable patient empowerment which is practically non-existent in India. Healthcare institutions should commit towards enforcing 'zero tolerance' towards lapses in prevention of HCAIs. Public pressure would force the Indian Government to acknowledge the problem, and to allocate more funds to improve resources and infrastructure; this could substantially elevate the standard of health care given to the average Indian. Despite the numerous challenges, overall public benchmarking of HCAIs is a commendable goal that would go a long way towards tackling this menace in developing countries such as India.

Point prevalence surveys of healthcare-associated infections and use of indwelling devices and antimicrobials over three years in a tertiary care hospital in India

Few hospitals in India perform regular surveillance for healthcare-associated infections (HAIs) and use of indwelling devices and antimicrobials. The aim of this study was to conduct two one-day point prevalence surveys of HAIs and use of indwelling devices and antimicrobials in a large 1800-bed tertiary care hospital in India. The overall prevalence of HAIs was 7%, and surgical site infections were the most common (33%). Indwelling devices were present in 497 (27%) patients, and 915 (50%) patients were receiving antimicrobials. This study helped to generate robust baseline data on the prevalence of HAIs and use of indwelling devices and antimicrobials in the study hospital.

Comparing hand hygiene measures in a neonatal ICU: a randomized crossover trial

OBJECTIVE

To compare plain soap, alcohol hand rub and iodophors as hand hygiene measures in a neonatal intensive care unit (NICU).

DESIGN

Randomized, crossover, three-armed, controlled trial with blinded outcome measurement.

SETTING

Level III NICU.

PARTICIPANTS

35 NICU nurses.

INTERVENTION

Participants were assigned to plain soap hand washing, alcohol hand rub and povidone-iodine hand scrub by a random cross-over design. Interventions were preceded by 14-day neutral periods. Cultures from hands were taken before and after each hand-hygiene use, prior to 5 patient-care activities.

MAIN OUTCOME MEASURE

The primary outcome was mean post-hygiene colony forming unit count (CFU-C).

RESULTS

There were differences between soap, alcohol and povidone groups vis a vis posthygiene CFUC [median: 60, 8 and 10.5, respectively (P<0.001)], absolute reduction in CFU-C [median: 15, 100 and 40, respectively (P<0.001)], percent reduction in CFUC [median: 33.3, 92 and 87, respectively (P<0.001)] and proportion with low CFU-C [47%, 71% and 72%, respectively (P<0.001)]. Alcohol [Adjusted OR 3.2 (95% CI 1.9, 5.3)], povidone-iodine [AOR 3.1 (95% CI 1.8, 5.3)] and high prehygiene CFU-C (>300) [AOR 0.18 (95% CI 0.1, 0.3)] were independently associated with low CFU-C.

CONCLUSION

After a 2 minute hand wash at entry into NICU, alcohol hand rub and povidone-iodine scrub are superior to plain soap hand wash for subsequent decontamination of hands of nurses working in NICU.

Detection of Shiga toxin variants among Shiga toxin-forming Escherichia coli isolates from animal stool, meat and human stool samples in India

AIM

To study the prevalence and distribution of various variants in the stx gene of Shiga toxin-producing Escherichia coli (STEC) isolated from diverse environmental sources (animal stool, meat) and human illness, from a large geographic area in India, and to understand the association between variants, serotype distribution and human disease.

METHODS AND RESULTS

A surveillance for STEC was conducted in the semi-urban and rural areas of Punjab, Himachal, Haryana and Chandigarh. Shiga toxin-producing Escherichia coli isolates (80 animal stool, 39 meat, 21 human stool from diarrhoea and HUS cases) were characterized for stx variants by PCR. Shiga-like toxin (Stx) was detected using Ridascreen-EIA assay. Variant stx2c was the most common (25·1%), followed by stx1d (13%), stx1c (10·7%) and stx2d (9·2%), whereas stx2e, stx2f and stx2g were absent. Only 8/21 (38%) human isolates harboured stx variants, of which stx2c and stx2d were found in 2 and 1 isolates, respectively. The low frequency of carriage of these potentially more pathogenic variants may explain the low severity of human illness seen in India. Shiga-like toxin was detected in only 42 of the isolates positive for the stx genes probably due to the low levels of toxins produced. Serogroup distribution was found to be diverse, suggesting the lack of any predominant circulating type.

CONCLUSIONS

The presence of stx variants 1c, 1d, 2c and stx2d in diverse environmental and human sources in India was demonstrated. The prevalence of the most common subtype stx2c found in this study in animal isolates may pose a threat to the public health. We report the subtyping of human STEC isolates and report the presence of stx1d subtype for the first time from India.

SIGNIFICANCE AND IMPACT OF THE STUDY

We demonstrated the presence of potentially pathogenic subtypes in the environmental specimens which may act as a reservoir for human infections. Serogroups new to India were also reported.

Viability kinetics, induction, resuscitation and quantitative real-time polymerase chain reaction analyses of viable but nonculturable Vibrio cholerae O1 in freshwater microcosm

AIM

To study the induction of a viable but nonculturable (VBNC) state in Vibrio cholerae O1 in freshwater, in response to cold temperatures (4°C) and starvation.

METHODS AND RESULTS

Vibrio cholerae O1 cells were inoculated in freshwater microcosm and incubated at 4°C. The cells became coccoid, rugose and subsequently nonculturable by day 16 on tryptic soy agar (TSA) and by day 23 on TSA-SP, while 87 and 65% of the cells retained their membrane integrity, respectively. Viable cells were observed until day 30 using direct fluorescent antibody-direct viable count method. In vitro resuscitation was demonstrated by temperature upshift. Utilizing 16S rRNA as an endogenous control, the DNA pol II (27·43-fold), fliG (12·44-fold), ABC transporter (27·11-fold), relA (60·76-fold) and flaC (15·29-fold) were significantly up-regulated in VBNC cells, while the expression of fadL-3 was comparable. The expression of DNA pol II, fliG, ABC transporter, relA and flaC was 3·3, 1·1, 5·9, 5·8 and 1·2-fold, respectively, for resuscitated cells. VBNC cells were found to be virulent, as ctxA and tcpA were expressed.

CONCLUSIONS

Vibrio cholerae undergoes both phenotypic alteration and genotypic modulation to protect itself from stress in freshwater.

SIGNIFICANCE AND IMPACT OF THE STUDY

Induction and resuscitation of the VBNC state in freshwater is important for an understanding of the epidemiology of cholera in the freshwater environment.

Environmental and epidemiological surveillance of Vibrio cholerae in a cholera-endemic region in India with freshwater environs

AIM

To conduct epidemiological and ecological surveillance of cholera in freshwater environments.

METHODS AND RESULTS

A freshwater region of India was surveyed between April 2007 and December 2008. Vibrio cholerae was isolated from 59·5% of water and plankton samples (n = 357) and 35·5% of stool samples (n = 290). Isolation from water was dependent on air (r = 0·44) and water temperatures (r = 0·49) (P < 0·01) but was independent of rainfall (r = 0·15), chlorophyll a (r = 0·18), salinity (r = 0·2) or pH (r = 0·2) (P > 0·05). Isolation from plankton was dependent on temperature of air (r = 0·45), water temperature (r = 0·44), chlorophyll a concentration (r = 0·42), pH (r = 0·23) and salinity (r = 0·39) (P < 0·01). Cholera cases correlated with rainfall (r = 0·82, P < 0·01) and chlorophyll a concentration (r = 0·42, P < 0·05), but not with air temperature (r = 0·3, P = 0·37). Vibrio cholerae O1 possessed ctxB, ctxA, rstR and tcpA (ElTor), toxR, toxT, rtxA, rtxC, mshA and hylA. Among non-O1-non-O139, the distribution of virulence-associated and regulatory protein genes was heterogeneous with - 0·7, 2·2, 94·77, 97·76, 99·25, 100 and 100% isolates being positive for tcpA, toxT, rtxA, rtxC, hylA, toxR and mshA, respectively. Two-thirds of non-O1-non-O139 isolates exhibited antibiotic resistance to various antibiotics that did not correlate with geographical site or time of origin for the isolates. RAPD and AFLP showed V. cholerae to be a diverse bacterium. AFLP demonstrated separate lineages for non-O1-non-O139 and O1 isolates.

CONCLUSION

Environmental parameters played a significant role in the emergence and spread of cholera and the abundance of V. cholerae. But based on virulence gene profiling and genetic fingerprinting, the possibility of origin of toxigenic isolates from nontoxigenic environmental isolates seems unlikely in freshwater environs of India.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study explains the ecology, epidemiology and seasonality of cholera in freshwater environs.

Demonstration of viable but nonculturable Vibrio cholerae O1 in fresh water environment of India using ciprofloxacin DFA-DVC method

AIM

To demonstrate the presence of culturable and nonculturable viable pathogenic Vibrio cholerae O1 in fresh water environments of a cholera-endemic region in India.

METHODS AND RESULTS

Conventional culture and ciprofloxacin DFA-DVC were utilized to investigate the existence of V. cholerae O1. We isolated pathogenic culturable V. cholerae O1 from water samples collected from cholera-affected areas. No culturable V. cholerae O1 was isolated from water and plankton samples from natural fresh water bodies. Ciprofloxacin was used for DFA-DVC as V. cholerae O1 are 100% resistant to nalidixic acid in our region. The viable but nonculturable O1 cells were demonstrated in 2.21 and 40.69% samples from natural water bodies and cholera-affected areas, respectively.

CONCLUSION

Vibrio cholerae O1 VBNC could be demonstrated using modified DFA-DVC technique. Ciprofloxacin is preferable to nalidixic acid for DVC in view of existing high-level resistance to nalidixic acid in cholera-endemic areas.

SIGNIFICANCE AND IMPACT OF THE STUDY

We endorse that for public health surveillance, cholera outbreak investigation and disease control water samples in addition to culture should be tested for V. cholerae using DFA-DVC.

Validity of quantitative unspun urine microscopy, dipstick test leucocyte esterase and nitrite tests in rapidly diagnosing urinary tract infections

OBJECTIVES

Rapid diagnostic tests can screen out negative samples and can save valuable time and money. The study was conducted to assess the usefulness of leukocyte esterase, nitrate reductase and quantitative microscopic unspun urine wet mount examination in rapidly diagnosing urinary tract infections (UTI).

METHODS

Four hundred and fifty samples were tested by semi-quantitative culture on cysteine lactose electrolyte deficient medium, microscopic examination of unspun urine for significant pyuria, dipstick leucocyte esterase test (LET) and nitrite test (NT). Culture was used as gold standard to evaluate the performance of direct microscopy and dipstick tests.

RESULTS

Urine culture examination revealed significant bacteriuria (>10(5) cfu/ml) 98 (21.8%), in urine samples. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and the diagnostic odds ratio (DOR) of the dip-stick LET were 73.5%, 58.5%, 33.0%, 88.8%, and 3.9 respectively; those of the dip-stick NT were 57.1%, 78.7%, 42.7%, 86.8%, and 4.9 respectively; and those for microscopic significant pyuria detection were 68.4%, 60.8%, 32.7%, 87.3%, and 3.4 respectively. Highest sensitivity (95.9%), NPV (97.9%) and DOR (25.7) was obtained on combining microscopy and dip-stick LET and NT (either of them positive). This can potentially cut costs by 79%.

CONCLUSION

Quantitative unspun urine wet mount microscopy and dipstick tests for leucocyte esterase and nitrite test should be added into routine laboratory practices for faster diagnosis of UTI.

Spread of cholera with newer clones of Vibrio cholerae O1 El Tor, serotype inaba, in India

During 2004 and 2005, cholera was recorded in 15 states of India, with 7 outbreaks. The newly emerged Vibrio cholerae O1 Inaba had a different antibiogram and ribotype, different pulsotypes, and different mutations in the wbeT gene. Due to the absence of serogroup O139, the Inaba serotype may have acquired the potential to affect the population at large.

Imipenem resistance in nonfermenters causing nosocomial urinary tract infections

Nonfermenting gram-negative bacilli (nonfermenters) have emerged as important nosocomial pathogens causing opportunistic infections in immunocompromised hosts. These organisms show high level of resistance to b-lactam agents, fluoroquinolones and aminoglycosides. Imipenem is a carbapenem antibiotic, which can be very useful for treatment of infections caused by nonfermenters. Eighty-five nonfermenters causing nosocomial UTI were tested for MIC to imipenem by agar dilution method. Resistance to other antimicrobial agents was compared between imipenem sensitive (S) and resistance (R) groups. Overall 36.4% of nonfermenters were resistant to imipenem. Forty two percent of P. aeruginosa and 18.5% of Acinetobacter baumanii were imipenem resistant. Other nonfermenters showed variable resistance, resistance in Alcaligenes spp. being very high. More than 70% of the nonfermenters were resistant to ceftazidime, gentamicin and ciprofloxacin. Piperacillin and amikacin had the best in vitro susceptibility. No significant difference was found in the antibiotic susceptibility profile among imipenem sensitive (S) or resistant (R) strains.

Nosocomial outbreak of diarrhoea by enterotoxigenic Escherichia coli among preterm neonates in a tertiary care hospital in India: pitfalls in healthcare

An outbreak of watery diarrhoea accompanied by low-grade fever and weight loss in 16 preterm neonates (age range 2-20 days) admitted to a neonatal intensive care unit (NICU) over four days in August 2000 is reported. Escherichia coli having similar antibiograms were identified on routine bacterial stool cultures in 14 (87.5%) neonates and none of the other known enteropathogens were detected. An investigation was undertaken to trace the source of infection. Surveillance cultures of swabs from the utensils used to prepare milk feed, culture of the formula feed and all items handled by one particular cook yielded growth of E. coli as did culture of his hand swabs and faecal sample. The causative agent was identified as enterotoxigenic E. coli (ETEC) as toxin production could be demonstrated by reverse passive latex agglutination in all the strains of E. coli isolated both from the infected neonates and the source of infection. The outbreak was effectively controlled by appropriate therapy and institution of proper measures of hygiene after identification of the source of infection.

Prevention of postoperative infections in ophthalmic surgery

Postoperative endophthalmitis is a serious, vision-threatening complication of intraocular surgery. Better instrumentation, surgical techniques, prophylactic antibiotics and better understanding of asepsis have significantly reduced the incidence of this complication. Postoperative endophthalmitis may occur as an isolated event or as a cluster infection. Topical antibiotics, preoperative periocular preparation with povidone-iodine combined with a sterile operating room protocol significantly reduce the incidence of isolated postoperative endophthalmitis. The role of antibiotics in the irrigating fluid and subconjunctival antibiotics remains controversial. Cluster infections on the other hand are more likely to occur due to the use of contaminated fluids/viscoelastics or a breach in operating room asepsis. Prevention of postoperative endophthalmitis requires strict adherence to operating room norms, with all involved personnel discharging their assigned roles faithfully.

Irradiation of mitochondria initiates apoptosis in a cell free system

The ability to modulate the sensitivity of mammalian cells to ionizing radiation (IR) (e.g. using chemotherapeutics) is dependent on our understanding of the primary target and biochemical pathway that leads to IR-induced apoptosis. We demonstrate using a cell free assay that irradiation of mitochondria is a primary event that initiates IR-induced apoptosis. IR results in loss of mitochondrial membrane potential, opening of the permeability transition pore (PTP) and the release of cytochrome c (cyto c). Apaf-1 and ATP were required to initiate apoptosis upon release of cyto c from mitochondria. The importance of mitochondrial events in the initiation of IR-induced apoptosis was also supported by the observation that inhibition of caspase-9 by the over-expression of dominant negative mutants resulted in the inhibition of IR-induced apoptosis. In contrast, inhibition of caspase-8 had only a minor impact on IR-induced apoptosis. Over-expression of Bcl-X(L) inhibited the initiation of IR-induced apoptosis due to its ability to prevent the loss of mitochondrial membrane potential, PTP opening and cytochrome c release. In a cell free assay for apoptosis, mitochondria as well as cytosol derived from Bcl-X(L) over-expressing cells were less efficient at supporting apoptosis in response to IR suggesting multiple roles for Bcl-X(L) in the regulation of apoptosis.

Indomethacin-induced apoptosis in esophageal adenocarcinoma cells involves upregulation of Bax and translocation of mitochondrial cytochrome C independent of COX-2 expression

The prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs) has been shown to exert a chemopreventive effect in esophageal and other gastrointestinal tumors. The precise mechanism by which this occurs, however, is unknown. While the inhibition of COX-2 as a potential explanation for this chemopreventive effect has gained a great deal of support, there also exists evidence supporting the presence of cyclooxygenase-independent pathways through which NSAIDs may exert their effects. In this study, immunohistochemical analysis of 29 Barrett's epithelial samples and 60 esophageal adenocarcinomas demonstrated abundant expression of the COX-2 protein in Barrett's epithelium, but marked heterogeneity of expression in esophageal adenocarcinomas. The three esophageal adenocarcinoma cell lines, Flo-1, Bic-1, and Seg-1, also demonstrated varying expression patterns for COX-1 and COX-2. Indomethacin induced apoptosis in all three cell lines, however, in both a time- and dose-dependent manner. In Flo-1 cells, which expressed almost undetectable levels of COX-1 and COX-2, and in Seg-1, which expressed significant levels of COX-1 and COX-2, indomethacin caused upregulation of the pro-apoptotic protein Bax. The upregulation of Bax was accompanied by the translocation of mitochondrial cytochrome c to the cytoplasm, and activation of caspase 9. Pre-treatment of both cell lines with the specific caspase 9 inhibitor, z-LEHD-FMK, as well as the broad-spectrum caspase inhibitor, z-VAD-FMK, blocked the effect of indomethacin-induced apoptosis. These data demonstrate that induction of apoptosis by indomethacin in esophageal adenocarcinoma cells is associated with the upregulation of Bax expression and mitochondrial cytochrome c translocation, and does not correlate with the expression of COX-2. This may have important implications for identifying new therapeutic targets in this deadly disease.

Erythromycin in pityriasis rosea: A double-blind, placebo-controlled clinical trial

BACKGROUND

The study stemmed from an incidental observation of improvement in 2 patients with pityriasis rosea while receiving erythromycin.

OBJECTIVE

The purpose of the study was to evaluate the efficacy of erythromycin in patients with pityriasis rosea.

METHODS

A double-blind, placebo-controlled clinical study was performed in an outpatient setting in a major hospital. Ninety patients over a period of 2 years were alternatively assigned to treatment group or placebo group. Patients in the treatment group received erythromycin in divided doses for 14 days. The response was categorized as complete response, partial response, or no response. All patients were followed up for 6 weeks.

RESULTS

Both groups were comparable with regard to age at presentation, sex, and average duration of disease at the time of reporting to the clinic. Upper respiratory tract infection before the appearance of skin lesions was reported in 68.8% of all patients. Complete response was observed in 33 patients (73.33%) in the treatment group and none in the placebo group (P <.0001).

CONCLUSION

Oral erythromycin was effective in treating patients with pityriasis rosea.

A caspase-resistant form of Bcl-X(L), but not wild type Bcl-X(L), promotes clonogenic survival after ionizing radiation

Bcl-2 and Bcl-X(L) belong to a family of proteins overexpressed in a variety of human cancers which inhibit apoptosis in response to a number of stimuli including chemotherapeutic agents and ionizing radiation. To better understand the role of these polypeptides in modulating the response of cancer cells to ionizing radiation we used cell lines that were engineered to overexpress the two polypeptides. Although Bcl-2 and Bcl-X(L) overexpression resulted in inhibition of radiation-induced apoptosis, it did not result in enhanced clonogenic survival. Consistent with this was the observation that Bcl-2 and Bcl-X(L) protected cells from DNA fragmentation, loss of mitochondrial membrane potential, and caspase activation for up to 72 hours after irradiation. Beyond 72 hours, there was a rapid loss in the ability of Bcl-2 and Bcl-X(L) to inhibit these markers of apoptosis. When Bcl-X(L) was analyzed at 72 hours after irradiation and beyond, a rapid accumulation of a 16-kDa form of Bcl-X(L) was observed. To test the hypothesis that cleavage of the 29-kDa form of Bcl-X(L) by caspases to a 16-kDa polypeptide results in its inability to inhibit apoptosis beyond 72 hours, we constructed a cell line that overexpressed a caspase-resistant form of Bcl-X(L) (Bcl-X(L)-deltaloop). Cells overexpressing Bcl-X(L)-deltaloop were resistant to apoptosis beyond 72 hours after irradiation and did not contain the 16-kDa form at these time points. In addition, Bcl-X(L)-deltaloop overexpression resulted in enhanced clonogenic survival compared with control or Bcl-X(L) overexpressing cells. These results provide a molecular basis for the observation that expression of Bcl-2 or Bcl-X(L) is not a prognostic marker of tumor response to cancer therapy.

Effects of tea polyphenols and flavonoids on liver microsomal glucuronidation of estradiol and estrone

Administration of 0.5 or 1% lyophilized green tea (5 or 10 mg tea solids per ml, respectively) as the sole source of drinking fluid to female Long-Evans rats for 18 days stimulated liver microsomal glucuronidation of estrone, estradiol and 4-nitrophenol by 30-37%, 15-27% and 26-60%, respectively. Oral administration of 0.5% lyophilized green tea to female CD-1 mice for 18 days stimulated liver microsomal glucuronidation of estrone, estradiol and 4-nitrophenol by 33-37%, 12-22% and 172-191%, respectively. The in vitro addition of a green tea polyphenol mixture, a black tea polyphenol mixture or (-)-epigallocatechin gallate inhibited rat liver microsomal glucuronidation of estrone and estradiol in a concentration-dependent manner and their IC50 values for inhibition of estrogen metabolism were approximately 12.5, 50 and 10 microg/ml, respectively. Enzyme kinetic analysis indicates that the inhibition of estrone glucuronidation by 10 microM (-)-epigallocatechin gallate was competitive while inhibition by 50 microM (-)-epigallocatechin gallate was noncompetitive. Similarly, several flavonoids (naringenin, hesperetin, kaempferol, quercetin, rutin, flavone, alpha-naphthoflavone and beta-naphthoflavone) also inhibited rat liver microsomal glucuronidation of estrone and estradiol to varying degrees. Naringenin and hesperetin displayed the strongest inhibitory effects (IC50 value of approximately 25 microM). These two hydroxylated flavonoids had a competitive mechanism of enzyme inhibition for estrone glucuronidation at a 10 microM inhibitor concentration and a predominantly noncompetitive mechanism of inhibition at a 50 microM inhibitor concentration.