Normothermic ex vivo perfusion provides superior organ preservation and enables viability assessment of hearts from DCD donors.

The shortage of donors in cardiac transplantation may be alleviated by the use of allografts from donation after circulatory death (DCD) donors. We have previously shown that hearts exposed to 30 min warm ischemic time and then flushed with Celsior supplemented with agents that activate ischemic postconditioning pathways, show complete recovery on a blood-perfused ex vivo working heart apparatus. In this study, these findings were assessed in a porcine orthotopic heart transplant model. DCD hearts were preserved with either normothermic ex vivo perfusion (NEVP) using a clinically approved device, or with standard cold storage (CS) for 4 h. Orthotopic transplantation into recipient animals was subsequently undertaken. Five of six hearts preserved with NEVP demonstrated favorable lactate profiles during NEVP and all five could be weaned off cardiopulmonary bypass posttransplant, compared with 0 of 3 hearts preserved with CS (p < 0.05, Fisher's exact test). In conclusion, DCD hearts flushed with supplemented Celsior solution and preserved with NEVP display viability before and after transplantation. Viability studies of human DCD hearts using NEVP are warranted.

Increasing the tolerance of DCD hearts to warm ischemia by pharmacological postconditioning.

Donation after circulatory death (DCD) offers a potential additional source of cardiac allografts. We used a porcine asphyxia model to evaluate viability of DCD hearts subjected to warm ischemic times (WIT) of 20­40 min prior to flushing with Celsior (C) solution. We then assessed potential benefits of supplementing C with erythropoietin, glyceryl trinitrate and zoniporide (Cs), a combination that we have shown previously to activate ischemic postconditioning pathways. Hearts flushed with C/Cs were assessed for functional, biochemical and metabolic recovery on an ex vivo working heart apparatus. Hearts exposed to 20-min WIT showed full recovery of functional and metabolic profiles compared with control hearts (no WIT). Hearts subjected to 30- or 40-min WIT prior to C solution showed partial and no recovery, respectively. Hearts exposed to 30-min WIT and Cs solution displayed complete recovery, while hearts exposed to 40-min WIT and Cs solution demonstrated partial recovery. We conclude that DCD hearts flushed with C solution demonstrate complete recovery up to 20-min WIT after which there is rapid loss of viability. Cs extends the limit of WIT tolerability to 30 min. DCD hearts with ≤30-min WIT may be suitable for transplantation and warrant assessment in a transplant model.

Relationship between estimated pretest probability and accuracy of automated Mycobacterium tuberculosis assay in smear-negative pulmonary tuberculosis.

BACKGROUND: The AMPLICOR assay (Roche; Branchburg, NJ), a rapid direct amplification test for Mycobacterium tuberculosis, has only been licensed for use in smear-positive respiratory specimens. However, many patients with pulmonary tuberculosis (PTB) have smear-negative disease. The clinical utility of this test in patients with smear-negative PTB is unknown. OBJECTIVE: To evaluate the effect of pretest probability of PTB estimated by chest physicians on the accuracy of the AMPLICOR assay in patients with smear-negative PTB. DESIGN AND METHODS: A prospective study of consecutive patients suspected of having smear-negative PTB. Two chest physicians estimated the pretest probability of active disease (high, intermediate, and low categories). Respiratory specimens were examined with radiometric broth medium cultures and with the AMPLICOR assay for M tuberculosis. The decision on a final diagnosis of PTB was blinded to the AMPLICOR results. RESULTS: Active PTB was diagnosed in 25 of 441 patients (5.7%). The AMPLICOR assay had an overall sensitivity of 44% and a specificity of 99%. Results of the assay were negative in seven patients with culture-negative PTB. The proportions of patients in the high, intermediate, and low pretest groups were 4.5%, 19.7%, and 75.7%, respectively. The incidence of PTB for each group was 95%, 3.4%, and 0.9%, respectively. The sensitivities of the AMPLICOR assay in the three groups of patients were 47%, 33%, and 33%, respectively, while the specificities were 100%, 98%, and 99%, respectively. CONCLUSIONS: In patients suspected of having smear-negative PTB, the following conclusions were drawn: (1) the incidence of active PTB was low; (2) pretest estimates accurately discriminated between patients with high and low risk of PTB; (3) the risk of PTB was overestimated in the intermediate group; and (4) the utility of the AMPLICOR assay in the intermediate-risk group may be limited by the overestimation of disease prevalence and low test sensitivity. Further studies are needed on the role of the AMPLICOR assay in better selected patients with an intermediate risk of having smear-negative PTB.

In vitro activity of meropenem against organisms causing serious infections in a Singapore hospital.

Meropenem (MEM) is a carbapenem antibiotic effective against infections caused by a variety of organisms. This study was conducted to evaluate MEM, which has not been previously used in the hospital, in parallel with some antimicrobial agents now in use, against organisms causing serious infections in the hospital. A total of 382 organisms isolated from blood cultures were included in the study. In the case of Bacteroides spp. and Burkholderia pseudomallei, organisms recovered from blood as well as from other sites were also included. In addition to MEM, 12 antimicrobial agents were tested against Gram-negative bacilli and seven against staphylococci. Antimicrobial susceptibility testing was carried out by the Kirby-Bauer disc diffusion technique based on the M2-A4 standard. The present paper demonstrates that meropenem, imipenem and ciprofloxacin are the most active antimicrobial agents against clinically important organisms causing serious infections in the hospital.

Widespread resistance to new antimicrobials in a university hospital before clinical use.

The activity of cefpirome, cefepime and piperacillin/tazobactam previously unused in the hospital was evaluated in parallel with five broad-spectrum antibiotics (ceftazidime, ceftriaxone, imipenem, ciprofloxacin and amikacin) currently being used to treat serious infections in the National University Hospital, Singapore. Two hundred and two clinically significant, organisms consecutively isolated during 1998 were included in the study. In vitro efficacy of cefepime, cefpirome and piperacillin/tazobactam was not superior to imipenem, ciprofloxacin and amikacin which are currently used. More than 40% of Enterbacteriaceae were found to be ESBL producers. The incidence of nosocomial organisms resistant to drugs used in serious infections had increased since 1995. Imipenem-resistance occurred in 34.4% of Acinetobacter spp. and 19.2% Pseudomonas aeruginosa. No single agent appeared to be suitable for empirical monotherapy of serious sepsis.

A study of 245 infected surgical wounds in Singapore.

The aims of the study were to correlate the laboratory detection rate of wound infections with the actual wound infection rate, and to analyse the bacteriology of these wounds to provide a rationale for antibiotic usage in prophylaxis and treatment of surgical wound infections. The wound infection rate in a general surgical unit was determined using the most comprehensive surveillance available to us and was correlated with the laboratory detection rate. A correlation coefficient of 0.8 was obtained, allowing a reasonable estimation of the actual wound infection rate from laboratory data. Review of the bacteriology of consecutive infected surgical wounds over a 4 year period in a university hospital, revealed that the commonest organisms cultured were Staphylococcus aureus, Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, enterococci and beta-haemolytic streptococci. Methicillin-resistant S. aureus (MRSA) caused 50% of all staphylococcal wound infections. All MRSA isolates were sensitive to fusidic acid and vancomycin. All the non-MRSA isolates of S. aureus were sensitive to cephalexin. Some 89% of E. coli were sensitive to gentamicin, with 93% and 100% sensitive to cefuroxime and ceftriaxone respectively. Klebsiella isolates have shown an increased resistance to aminoglycosides, with a new strain from one patient, isolated in 1990, resistant to penicillins, aminoglycosides and third generation cephalosporins. Pseudomonas spp., enterococci and beta-haemolytic streptococci did not show a change in resistance patterns over the same time period.

Antimicrobial resistance problem in a university hospital.

In a study conducted in 1991 in the National University Hospital, Singapore, the susceptibilities of a total of 2156 recent clinical isolates were tested against 25 antimicrobial drugs. The organisms were those isolated from routine specimens received in the microbiology laboratory. About 40% Staphylococcus aureus isolations in the hospital were resistant to methicillin. A high incidence of the resistance was noted among Staphylococcus aureus and coagulase negative staphylococci to antistaphylococcal drugs. Acinetobacter sp. and Klebsiella sp. are becoming major threats with regard to antimicrobial treatment as they are multi-drug resistant. Pseudomonas aeruginosa did not show a resistance problem except to pefloxacin (74%). Ampicillin resistance of Acinetobacter sp. (93%) was reduced to 71% by ampicillin/clavulanic acid and to 7% by ampicillin/sulbactam. With regards to the urinary isolates higher rates of resistance were noticed with Pseudomonas aeruginosa to antipseudomonas drugs and for co-trimoxazole with other Gram negative organisms, compared to non-urinary isolates.

Bacteria, viruses, yeasts and protozoans associated with diarrheal disease in Singapore.

Labile toxin producing enterotoxic E. coli (ETEC) were the commonest pathogen isolated from diarrheal stools of hospitalized children (21%) and adults (26%) in Singapore. Salmonellas ranked a close second in children (19%). Other bacterial pathogens were isolated from less than 5% of subjects. Blastocystis hominis was detected in 4.3% of diarrheal stools when a simple sedimentation technique was used. Cryptosporidium was not detected at all. An analysis of yeast counts in smears of diarrheal and non-diarrheal stools suggested they were etiologically associated with at least 6% of diarrhea in children and 19% in adults. Testing for rotaviruses by Latex agglutination and for adenovirus by electronmicroscopy showed an association with 6 per cent and 3 per cent diarrhea respectively. The study highlighted a need for: case control studies on ETEC and B. hominis; studies on the epidemiology of diarrhea by yeasts; establishing the true incidence of adenovirus diarrhea; studies on the prevalence and seasonality of rotavirus infection in Singapore.

Urinary tract infections in patients with diabetes mellitus.

We have endeavoured to determine whether there is any difference in the bacteriological pattern of UTI and the antibiotic sensitivity patterns of the pathogens concerned between diabetic and non-diabetic patients. Over a period of 1 year, a total of 287 diabetic patients (221 females and 66 males) with community-acquired and nosocomial urinary tract infections were studied. There were 265 patients (228 females and 37 males) without any predisposition to urinary tract infections (UTI) and who served as controls. Although Escherichia coli was the predominant organism in community-acquired UTI in diabetic patients, it was found significantly less than in the non-diabetic population (P less than 0.005). The percentage of Klebsiella species causing community-acquired UTI in diabetic patients was significantly higher than in non-diabetics (P less than 0.005). The antibiotic sensitivity patterns of the organisms in the two groups, however, were not significantly different. The organisms isolated from nosocomial UTI in diabetics showed a significantly greater preponderance of Klebsiella spp. and a significantly lower percentage of E. coli when compared to community-acquired UTI in diabetics (P less than 0.005). Klebsiella spp. in nosocomial UTI of diabetics showed an overall increase in resistance to antibiotics. At least a quarter of the isolates of Klebsiella spp. in nosocomial UTI were resistant to third-generation cephalosporins. Patients with diabetes mellitus appear to have an increased incidence of Klebsiella spp. as the pathogen in both community-acquired and nosocomial UTI. Antibiotic resistance in the organisms isolated from nosocomial UTI is greater than that related to community-acquired UTI in diabetic patients.

Moraxella catarrhalis respiratory infection in adults.

Moraxella catarrhalis (MC) is an upper respiratory tract commensal which may also be pathogenic. In this report we examined the clinical features, microbiology and therapeutic response in 30 consecutive adult patients with pneumonia who had MC isolated in the sputum. The mean age was 66 years with an equal sex ratio. Most patients gave a history of cigarette smoking (77%) and had underlying pulmonary diseases (73%). Dyspnea and productive cough were the most common complaints (87%). Fever was a manifestation in 60% of patients. Chest X-ray features of pneumonia were noted in 78% of patients while leucocytosis (> 11,000/mm3) was evident in 70%. While all isolates were susceptible to tetracycline, 70% were resistant to penicillin/ampicillin by in-vitro testing. Three patients died, two from their underlying illnesses and one from myocardial infarct. We believe that MC isolated in sputum cultures from symptomatic adults with underlying respiratory diseases should be treated as a pathogen. The short term prognosis is good.

Multiple antibiotic resistance in Klebsiella spp. and other Enterobacteriaceae isolated in Singapore.

A common pattern of multiple antibiotic resistance has been noted in bacteria isolated from Singaporean patients. The resistance pattern includes: ampicillin, cefuroxime, ceftazidime and other third generation cephalosporins, aztreonam, gentamicin and other aminoglycosides. The bacterial species implicated are Klebsiellas and other members of the Enterobacteriaceae. Preliminary laboratory investigation with a disk-diffusion augmentation test suggests the presence of extended-spectrum beta-lactamases. A retrospective study of laboratory blood culture records shows a rising incidence of resistance in Klebsiella spp. since 1985. Antimicrobial susceptibility results suggest a high degree of co-transfer of aminoglycoside resistance. The high frequency of this type of multiple antibiotic resistance should result in greater caution in the selection of presumptive antibiotic therapy for septicaemia, in order to avoid treatment failure and further selection of resistant strains.

The pattern of utilisation and accuracy of a commercial nucleic acid amplification test for the rapid diagnosis of Mycobacterium tuberculosis in routine clinical practice.

BACKGROUND: Several nucleic acid amplification (NAA) tests are available for the rapid detection of Mycobacterium tuberculosis (MTB) in clinical specimens. AIMS: To identify the pattern of utilisation and accuracy of the AMPLICOR test in routine clinical practice in an acute care setting. DESIGN: A retrospective descriptive study. METHOD: We studied 159 consecutive specimens in which the AMPLICOR (Roche; Branchburg, NJ) test was requested by attending doctors. The sensitivities and specificities of the AMPLICOR for detection of active tuberculosis (TB) were calculated in relation to types of specimens, smear and culture results. RESULTS: The number of requests more than doubled from 1999 to 2000. Thirty-eight percent of the specimens were not from the respiratory tract. The majority of the specimens had requests for one or more additional test (mean 1.8). The rate of active TB was 18%. The sensitivities of the AMPLICOR on per specimen, per patient, per smear negative specimen and per smear negative patient basis were found to be 81%, 80%, 66.7% and 71.4% respectively. The specificities for these groups accordingly were 99%, 98.6%, 99% and 98.6% respectively. The sensitivity and specificity for respiratory specimens were 97.5% and 98.5%, while for non-respiratory specimens, they were 60% and 100%. In smear negative specimens, the sensitivity and specificity for respiratory specimens were 60% and 98.5%, while for non-respiratory specimens, they were 75% and 100%. The AMPLICOR assay was negative in all 21 specimens of pleural or spinal fluid. CONCLUSIONS: There is a growing demand for NAA in the rapid diagnosis of TB with a high proportion of non-respiratory specimens. The number of additional diagnostic tests performed on each specimen should be limited. In routine clinical practice, the AMPLICOR assay is a useful confirmatory test for active pulmonary TB. The utility of the AMPLICOR assay for MTB detection in exudative fluid specimens needs further evaluation.

Genital Group B Streptococcus carriage in the antenatal period: its role in prom and preterm labour.

Of 326 high vaginal swabs taken during the antenatal period, Group B Streptococcus (GBS) was isolated from the birth canal in 46 women, giving a carrier rate of 14.1%, which is within the often quoted range of between 5% - 25% in different parts of the world. Carriage rates were similar at different gestations. In a subgroup of 34 women, 2 swabs taken at least 5 weeks apart yielded results which were discordant in over one fifth of the time. This knowledge of the natural history of GBS carriage questions the practice of treating asymptomatic carriers of GBS in the antenatal period to prevent transmission of GBS to the neonate. The group of women with positive swabs in the antenatal period did not have a significantly higher incidence of preterm labour and/or prelabour rupture of membranes (PROM) compared with the group of women with negative swabs. Routine screening of the antenatal population for GBS carrier status prior to 32 weeks gestation may not identify women at high risk of PROM or preterm labour.

Endemic typhus in Singapore--a re-emerging infectious disease?

UNLABELLED: Singapore is a modern urban city and endemic typhus is thought to be a disease of the past. This may be due to lack of specific serological testing as indirect immunoperoxidase testing using specific rickettsial antigens (U.S. Army Medical Research Unit, Institute of Medical Research, Kuala Lumpur, Malaysia) has only recently become available. In the last fourteen months, twenty-one cases of endemic typhus were diagnosed in patients hospitalised for acute febrile illnesses at the National University Hospital. We conducted a case control study to define the clinical and laboratory features of endemic typhus in Singapore. METHOD: Demographic, clinical and laboratory data were reviewed for cases and twenty-one age and sex matched controls who had negative serologic tests as part of a work-up for fever of unknown origin. RESULTS: Apart from a higher initial temperature (39 degrees C vs 37.9 degrees C (p < 0.001)) and ALT(p = 0.002), cases and controls had similar presentations of fever, myalgia, headache, cough, normal WBC and platelet counts. Singapore residents and migrant workers were represented in both groups (p = ns). CONCLUSION: Endemic typhus remains an important cause of acute febrile illness in Singaporein both the local and migrant worker populations. The presentation is similar to other causes of acute febrile illnesses and the diagnosis will be missed unless it is specifically sought.

Epidemiological, clinical and laboratory characteristics of 19 serologically confirmed rickettsial disease in Singapore.

AIM: To identify epidemiological, clinical and laboratory features of serologically-proven typhus in the local setting. METHOD & RESULTS: Retrospective study looking at rickettsial serologies done over a six-month period and collection of the epidemological, clinical, laboratory and treatment response data from the case notes of the patients with an ordered rickettsial serology. Twenty of the 35 cases had a positive serology. Of these 20 patients, 18 were already clinically diagnosed as having murine typhus. All except one were males and all were migrant workers. Majority of the patients were construction workers staying in containers where rats abound. The most consistent clinical features were high fever (100%) for a median period of seven days, headache (94%) and cough (47%). The white cell count was usually normal (74%) but thrombocytopenia was common (68%). Transaminitis was also common (90%) with the AST component higher than the ALT in half of the cases. Response to doxycycline therapy was rapid and most (88%) were afebrile by 72 hours. CONCLUSION: Typhus (notably murine type) can be confidently diagnosed from consistent clinical features supported by epidemiological and laboratory clues. Early recognition with the prompt treatment response will result in shorter hospital stay with decreased cost. Serological testing may only prove useful in difficult situations when the clinical diagnosis is less clear.

Adult community acquired bacterial meningitis in a Singaporean teaching hospital. A seven-year overview (1993-2000).

BACKGROUND: The objective of this study is to describe the bacteriological, clinical and laboratory features of community acquired bacterial meningitis in adults admitted to a Singapore tertiary-care hospital. METHODS: Two hundred sixty-nine cases of meningitis or meningoencephalitis admitted between 1993 and 2000 were identified by their discharge diagnosis codes. All case records except for 57 which could not be retrieved were retrospectively reviewed. Patients less than 14 years or with skull fractures, post-neurosurgery or with indwelling intracranial devices were excluded. Inclusion criteria was a clinical picture compatible with a diagnosis of bacterial meningitis with either (1) positive cerebral-spinal fluid (CSF) cultures or latex coagglutination or CSF neutrophilic pleocytosis accompanied by positive blood cultures or (2) in the absence of positive blood cultures, CSF cultures and latex agglutination, presence of CSF pleocytosis of at least 100 neutrophils per microL. RESULTS: Fifteen "culture-positive" and 11 "culture negative" cases were identified. Six (55%) of the "culture-negative" cases received antibiotics prior to admission. Cultures grew Streptococcus pneumoniae in four cases, three cases each of Group B streptococci and Neisseria meningitides. Listeria monocytogenes and Klebsiella pneumoniae were each seen twice and Streptococcus suis once. All cases of Group B streptococci occurred in the year 1998. Mortality was 19% (n = 5), six developed infections in other sites, three epileptic seizures, three developed hydrocephalus, and two hearing loss. CONCLUSIONS: Pathogens are similar to those reported in other studies but for an outbreak of Group B Streptococcus in 1998. There were a high number of "culture-negative" cases which may be due to preceding antibiotic intervention.

Prospective study of the aetiology of adult community acquired bacterial pneumonia needing hospitalisation in Singapore.

A prospective survey of 96 consecutive adult patients with community acquired pneumonia requiring hospitalisation was carried out at National University Hospital, Singapore. Causative pathogens were identified in 58% of patients. Mycobacterium tuberculosis was the most common pathogen (21%), followed by Streptococcus pneumoniae (12%), Haemophilus influenzae (5.2%), Mycoplasma pneumoniae (5.2%) and Staphylococcus aureus (4.2%). Gram-negative organisms (apart from Haemophilus influenzae) were found in 10% of pneumonia patients. More than half of the patients had pre-existing illness, the most common was diabetes mellitus (21%).

Sequence and phylogenetic analysis of SH, G, and F genes and proteins of Human respiratory syncytial virus isolates from Singapore.

To study the genetic variability and molecular epidemiology of Human respiratory syncytial virus (HRSV) occurring in Singapore, nucleotide sequencing of three membrane-associated genes (SH, G and F) of four local isolates was performed. Comparison of their nucleotide and amino acid sequences with those of the prototype strains A2 (subgroup A) and CH-18537 (subgroup B) indicated that the Singapore isolates belong to the subgroup A. Comparison of the Singapore isolates with the reference strain A2 showed that whereas the G protein was the most divergent with up to 15% difference, the F and SH proteins showed less diversity of only up to 4%. Each gene exhibited its distinct variable and conserved regions. The N- and O-glycosylation sites within the G protein of the isolates were analyzed to ascertain their potential implications on the antigenicity of the viral glycoprotein. Based on the second variable region of the G protein, phylogenetic analysis of the Singapore isolates with 91 previously identified genotypes of subgroup A revealed that more than one genotype (GA2 and GA5) may circulate in the local population at a given time. This epidemiological study reflects the pattern of genetic relationships between the HRSV isolates from Singapore to those from other parts of the world.

A comparison of costs and effectiveness of the BACTEC NR-730 system and a conventional method of blood culture.

Results and costs of the first six months experience with BACTEC NR-730 were compared with a series of blood cultures performed by the conventional method previously used. The newer technology detected the growth of 14.1% of significant isolates on the day of receipt of the specimens. The previous method lacked blind subcultures on the day of receipt and therefore detected growth only after overnight incubation. No direct comparison of the sensitivities of the methods was possible, but the percentages of cultures yielding significant isolates were similar for the two methods. With the new method, technicians needed less time for daily screening of blood cultures, fewer subcultures were required and less contamination was observed. The method used to calculate the directly-related variable costs of the two methods is set out. In the particular situation reported, workload and labor costs were such that introduction of BACTEC NR-730 resulted in a saving on variable costs.