Bacteriology of Sputum Samples: A Descriptive Cross-sectional Study in a Tertiary Care Hospital

Introduction:

Lower respiratory tract infection is a common infection and accounts for a greater burden of disease worldwide. It is a great challenge to the clinician and still more, with increasing antimicrobial resistance. Its empirical treatment may vary according to the type of causative organisms. The objective of this study is to identify the pathogenic microorganisms and their antimicrobial susceptibility pattern from sputum sample.

Methods:

This descriptive cross-sectional study was conducted in KIST Medical College and Teaching Hospital from February 2015 to January 2016. Ethical approval was taken from institutional review committee prior to the study with reference no. 0051/2014/15. Data on culture and sensitivity of isolates from sputum samples were collected from the records of the hospital. Sample collection, processing, identification of microorganisms and antimicrobial susceptibility tests were performed according to the Clinical and Laboratory Standards Institute guidelines. All the data were tabulated in an Excel sheet and analyzed using SPSS version 20.

Results:

Out of 2318 samples, 694 (29.93%) sputum samples at 95% confidence interval (737.21650.79) were reported as culture positive. Klebsiella was the most common isolate followed by Pseudomonas, Escherichia coli, Acinetobacter, Staphylococcus aureus, Candida albicans, Streptococcus pneumoniae, Streptococcus pyogenes, and others. Imipenem and vancomycin showed the most sensitivity towards gram-negative and gram-positive bacteria respectively.

Conclusions:

Proper diagnosis, identification of causative agents and their antimicrobial susceptibility pattern are important steps to limit the irrational use of antimicrobials. Prescribing antimicrobials empirically in the case of suspected lower respiratory tract infection is difficult.

Effect of Different Doses of Inhaled Corticosteroids on the Isolation of Nasopharyngeal Flora in Children with Asthma

OBJECTIVE

To find the effects of inhaled corticosteroids and the impact of different doses of inhaled corticosteroids on the isolation of nasopharyngeal flora in asthmatic children aged 1-15 years.

METHODS

The study included 75 children with asthma and 25 age-matched controls. Nasopharyngeal swabs were obtained. Bacteria were identified by standard techniques.

RESULTS

Pathogenic organisms were isolated from 36% of asthmatic children and 20% of controls, the difference was not significant statistically (OR=2.25, 95% CI=0.75-6.67, P=0.13). There was no statistically significant association of using a high dose of inhaled corticosteroids with the isolation of pathogenic organisms. Usage of biomass fuel for cooking in the household of asthmatic children increases the risk of colonization (OR=3.4, 95% CI= 1.26-9.10, P=0.03).

CONCLUSIONS

Inhaled corticosteroids are safe in the treatment of asthma and there is no association between different doses of Inhaled corticosteroids and isolation of the pathogenic organism.

Long-term Experience with Rapid Screening for Platelet Bacterial Contamination in a High-volume Transfusion Service

Bacterial sepsis after platelet transfusion is a major cause of transfusion-transmitted infections in the US. The Food and Drug Administration (FDA) recommends performing quality control for platelet bacterial detection on days 4 and 5 before platelet transfusion. We assessed the feasibility of implementing the Pan Genera Detection (PGD) test, an FDA-approved immunoassay for platelet bacterial detection, for the primary and secondary bacterial screening of platelet units in a high-volume setting. Records were reviewed from January 2010 through December 2015. All apheresis platelets underwent primary screening by using culture methods. Additional screening with the PGD test was performed daily until February 2013, when PGD testing of apheresis platelets was performed at the start of storage day 5. In April 2015, PGD testing of apheresis platelet products was performed at the start of storage day 4. Post-storage pooled whole blood-derived platelets were screened by using the PGD test on the day of use. During the 6-year study period, 16,839 PGD tests were performed. If the PGD test was reactive, repeat PGD testing was performed. In cases of repeat reactivity, units were quarantined and cultured. Initially, 42 (0.25%) tests were reactive; 26/42 (61.91%) were repeatedly reactive and resulted in an overall PGD repeat reactivity rate of 0.15%. Only one sample grew coagulase-negative Staphylococcus No transfusion-transmitted infections were reported. The PGD bacterial detection assay was feasible and efficient in our high-volume transfusion service.

Epidemiological characteristics of pulmonary tuberculosis in Shandong, China, 2005-2017: A retrospective study

This study aimed to analyze the epidemiology of pulmonary tuberculosis (PTB) and gained insight into the future TB control plan in China.We extracted epidemiological, clinical, and geographic data from TB prevention and control institutions in 6 cities of Shandong province, China, during 2005 to 2017.Among 224,480 diagnosed PTB, rural residents accounted for 93%, smear-positive PTB 52%, and new cases 92%. The incidence rate of overall PTB declined from 40.8 to 26.25 per 100,000 during 2005 to 2017. Except smear-negative PTB (7.57-19.87 per 100,000), the incidence of smear-positive PTB and all that stratified by age, sex, and treatment history decreased. With 80% reduction, the incidence of smear-positive PTB (6.38 per 100,000) and relapse cases (1.01 per 100,000) were already very low in 2017.With persistent efforts to combat TB, the disease burden had shifted from smear-positive PTB to smear-negative PTB. While new cases need continuous attention, further reducing the incidence of smear-negative PTB and elderly patients may have a greater impact on future TB control.

The Significance of Repeat Cultures in the Treatment of Severe Fungal Keratitis

PURPOSE

To identify fungal keratitis patients who are at risk of a poor outcome and may benefit from closer follow-up or more aggressive treatment.

DESIGN

Secondary analysis of randomized clinical trial data.

METHODS

We compared the clinical outcomes of patients who had positive 6-day fungal cultures with those who did not, using backward stepwise regression with covariates for all baseline clinical characteristics.

SUBJECTS

Patients presenting with a smear-positive filamentous fungal ulcer and visual acuity of 20/400 or worse, and who subsequently had a 6-day fungal culture performed at the Aravind Eye Care system (India), Lumbini Eye Hospital (Nepal), or Bharatpur Eye Hospital (Nepal).

MAIN OUTCOME MEASURES

The primary outcome is rate of corneal perforation and/or the need for therapeutic penetrating keratoplasty. Secondary outcomes include 3-month best spectacle-corrected visual acuity (BSCVA), 3-month infiltrate and/or scar size, and rate of re-epithelialization.

RESULTS

Patients who tested positive at their 6-day culture had twice the hazard of experiencing a corneal perforation or the need for therapeutic penetrating keratoplasty (P = .002) than those who tested negative, even after controlling for baseline ulcer characteristics. These patients also had on average 0.26 logMAR lines worse BSCVA at 3 months (P = .001). Culture positivity at day 6 was not a statistically significant predictor of 3-month infiltrate/scar-size (-0.24 mm¹; P = .45) or time to re-epithelialization (hazard ratio = .81; P = .31).

CONCLUSIONS

Here we identify a uniquely valuable clinical tool, day 6 culture results, for the treatment of severe fungal keratitis. Risk stratification based on repeat culture positivity is an objective way to assess response to medical therapy and identify patients who are at high risk of a poor clinical outcome. This establishes a new standard of care for severe fungal keratitis management.

Efficacy of periodic surveillance culture in a neonatal intensive care unit in the presumption of causative pathogens of late-onset bacterial infection

BACKGROUND

Surveillance cultures have been recommended for infection control of resistant bacteria in neonatal intensive care units (NICUs). However, the utility of surveillance cultures in the presumption of causative bacteria in late-onset bacterial infection has been controversial. The aim of the present study was to investigate the relationship between the causative pathogens of late-onset bacterial infection and the results of periodic surveillance cultures in a NICU.

METHODS

A retrospective study was performed on 600 patients hospitalized in the NICU of a large metropolitan hospital from 2010-2013. The correspondence of the results of surveillance cultures with causative pathogens was analyzed in patients who developed late-onset bacterial infection.

RESULTS

Staphylococcus species and enterobacterium were the most prevalent in the samples obtained from the oropharynx and rectum, respectively, during the investigation period. Twenty patients (3.3%) developed late-onset bacterial infection. The causative pathogens in 15 patients (75%) were also detected from the final surveillance cultures; these patients tended to be older than the other 5 patients (P = .003).

CONCLUSIONS

Surveillance cultures might be useful for the presumption of causative pathogens of late-onset bacterial infection in patients with risk factors for the development of nosocomial bacterial infection.

Cost-effectiveness analysis of universal screening for carbapenemase-producing Enterobacteriaceae in hospital inpatients

The purpose of this study was to assess the cost-effectiveness of screening all hospital inpatients for carbapenemase-producing Enterobacteriaceae (CPE) at the time of hospital admission, compared to not screening, from a US hospital perspective. We used a linked transmission/Markov model to compare outcomes for a typical hospitalized medical patient, from a community with a colonization prevalence of 0.05%. Outcomes were number of colonized patients, CPE-related clinical infections and deaths, expected quality-adjusted life years (QALYs), cost, and the incremental cost-effectiveness ratio (ICER). Sensitivity analyses were performed to assess the effect of parameter uncertainty, using a willingness-to-pay threshold of $100,000 per QALY gained. Screening prevented six CPE colonization cases per 1000 patients (1/1000 colonized with screening, 7/1000 without screening), over half of all symptomatic CPE infections (2/10,000 symptomatic with screening, 5/10,000 symptomatic without screening), and nearly half of all CPE-related deaths (8/100,000 deaths with screening, 15/100,000 deaths without screening). Screening accrued 0.0009 additional QALYs and cost an additional $24.68, compared to not screening, and was cost-effective (ICER $26,283 per QALY gained). Our results were sensitive to uncertainty in prevalence and the number of secondary colonizations per colonized patient. Screening was not cost-effective at a prevalence below 0.015% or if transmission to fewer than 0.9 new patients occurred for each colonized patient. At prevalence levels above 0.3%, screening was cost-saving compared to not screening. Screening inpatients for CPE carriage is likely cost-effective, and may be cost-saving, depending on the local prevalence of carriage.

Validation of Procedural Codes to Identify Infants Evaluated for Serious Bacterial Infection

OBJECTIVE

To validate a novel coding method using Current Procedural Terminology, Fourth Edition (CPT-4) codes for identifying infants who underwent a full evaluation for serious bacterial infection (SBI).

METHODS

We performed a multicenter, retrospective examination to determine the accuracy of a combination of CPT-4 codes for blood, cerebrospinal fluid (CSF), and urine cultures to identify previously healthy infants ≤90 days old admitted to a general care floor and fully evaluated for SBI. Full SBI evaluation was defined as blood, CSF, and urine cultures performed during the emergency department encounter or corresponding hospitalization. Cases were defined as infants who had codes for blood, CSF, and urine cultures (87040, 87070, and either 87086 or 87088), and these were compared with all other encounters. We validated these findings by comparing medical record documentation of blood, CSF, and urine cultures to the corresponding CPT-4 codes, with calculation of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

We identified 8548 qualifying encounters, and 347 (4%) had a combination of CPT-4 codes 87040, 87070, and either 87086 or 87088. This combination had a sensitivity of 100% (95% confidence interval, 98.9-100) and specificity of 98.2% (95% confidence interval, 97.3-98.8) for identifying infants who underwent full SBI evaluation for an unknown source.

CONCLUSIONS

CPT-4 codes provide an accurate means to identify infants who underwent complete SBI evaluation.

T-CELL RESPONSES ASSESSED USING IGRA AND TST ARE NOT CORRELATED WITH AFB GRADE AND CHEST RADIOGRAPH IN PULMONARY TUBERCULOSIS PATIENTS

A definitive marker determining the bacillary load of Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), and hence disease severity, is required for patient monitoring and management. In this study, the association among T-cell responses based on the interferon-gamma release assay (IGRA) and the tuberculin skin test (TST), the sputum acid-fast bacilli (AFB) grade and types of radiological lesions were analyzed in new cases of pulmonary TB patients (n = 54) at Srinagarind Hospital, Khon Kaen, Thailand between September 1, 2012 and March 31, 2014. It was found that infiltrative and cavitary lesions from chest radiographs were associated with high sputum AFB grade (p = 0.048). T-cell responses from both IGRA and TST were not correlated with sputum AFB grade. Neither IGRA nor TST was correlated with the bacillary load as defined by AFB grade and chest radiographs. Patients with cavitary lesions on chest radiographs tended to have high IFN-γ concentrations and large TST indurations. In addition, TB patients with previous BCG vaccination showed significantly higher IFN-γ induction compared to the non-vaccinated group (p = 0.001). This study showed T-cell responses based on both IGRA and TST were not correlated with AFB grade and chest radiograph. In areas of high rates of BCG vaccination, as in Thailand, the BCG may affect IGRA and TST interpretations.

External validation of the Cham score for ordering of blood cultures in emergency department patients with non-hospital acquired pneumonia

INTRODUCTION

The aim of this study was to externally validate the Cham score for the prediction of bacteraemia in emergency department (ED) patients with non-hospital acquired pneumonia.

MATERIALS AND METHODS

This is a secondary analysis of a dataset collected to identify independent predictors of bacteraemia in adult ED patients with non-hospital acquired pneumonia. The primary outcome of interest was the predictive performance (sensitivity, specificity, negative predictive value) of the score with respect to bacteraemia. Secondary outcomes included the performance of the score in patients not known to be intravenous (IV) drug users, the predictive performance of pneumonia severity index (PSI) class IV/V and PSI class IV/V or IV drug use as predictors and the clinical impact of score application on test ordering. Data analysis was by clinical performance and receiver operator characteristic curve analysis.

RESULTS

A total of 200 patients were studied; 14 true positive blood cultures (7%, 95% CI, 4% to 11%). The Cham score had a sensitivity of 92.9% (95% CI, 64.2% to 99.6%), specificity of 26.3% (95% CI, 20.3% to 33.4%) and negative predictive value (NPV) of 98% (87.0% to 99.9%). Area under the receiver operating characteristic (ROC) curve was 0.71 (95% CI, 0.56 to 0.86). Using PSI class IV/V or known IV drug use as predictors had sensitivity of 92.9% (95% CI, 64.2% to 99.6%), specificity of 51.1% (95% CI, 43.7% to 58.4%) and NPV of 99% (95% CI, 93.5% to 99.9%).

CONCLUSION

In retrospective external validation, the Cham score performed better than in derivation with acceptable sensitivity and NPV. Simplified criteria (PSI class IV/V or known IV drug use), as yet not validated, had similar sensitivity and NPV but would avoid blood cultures in a higher proportion of patients.

Changes in concentration of Alternaria and Cladosporium spores during summer storms

Fungal spores are known to cause allergic sensitization. Recent studies reported a strong association between asthma symptoms and thunderstorms that could be explained by an increase in airborne fungal spore concentrations. Just before and during thunderstorms the values of meteorological parameters rapidly change. Therefore, the goal of this study was to create a predictive model for hourly concentrations of atmospheric Alternaria and Cladosporium spores on days with summer storms in Szczecin (Poland) based on meteorological conditions. For this study we have chosen all days of June, July and August (2004-2009) with convective thunderstorms. There were statistically significant relationships between spore concentration and meteorological parameters: positive for air temperature and ozone content while negative for relative humidity. In general, before a thunderstorm, air temperature and ozone concentration increased, which was accompanied by a considerable increase in spore concentration. During and after a storm, relative humidity increased while both air temperature ozone concentration along with spore concentrations decreased. Artificial neural networks (ANN) were used to assess forecasting possibilities. Good performance of ANN models in this study suggest that it is possible to predict spore concentrations from meteorological variables 2 h in advance and, thus, warn people with spore-related asthma symptoms about the increasing abundance of airborne fungi on days with storms.

Survey of methods used to detect bacterial contamination of platelet products in the United States in 2011

BACKGROUND

Testing of platelets (PLTs) for bacterial contamination is required by the AABB Standards but is not fully standardized. On January 31, 2011, a new AABB Standard, 5.1.5.1.1, specified that bacterial detection methods for PLT components shall use assays either approved by the Food and Drug Administration (FDA) or validated to provide sensitivity equivalent to these FDA-approved methods.

METHODS

An Internet-based survey of AABB member institutions was conducted from May to June 2012, to document current practices used in 2011 for bacterial detection in different PLT products and to assess the impact of the new standard.

RESULTS

Of 1053 AABB member institutions surveyed, 40 of 99 blood centers (40.4%) and 184 of 954 hospital blood banks or transfusion services (19.3%) responded. Sixty-four respondents manufactured PLTs. Apheresis PLTs (APs) were predominantly screened with the BacT/ALERT system (89.5%); the majority (95.2%) were cultured with at least 8 mL of product. There was substantial variation in the minimum incubation time of cultures before release of PLTs (range, 0 to >24 hr). Recalls of released AP for possible bacterial contamination were largely successful (67.3%); successful interdiction before transfusion was associated with incubation for more than 12 hours before release (p < 0.01). After Standard 5.1.5.1.1 took effect, there was a decrease in production of whole blood-derived PLT concentrates (WBPCs). Point-of-issue ("rapid") immunoassays were used to screen a substantial proportion of WBPC PLTs, but were rarely used as secondary tests for previously cultured APs.

CONCLUSION

The survey identified variability in culture methods and release times with AP, while use of WBPC decreased after AABB Standard 5.1.5.1.1 became effective.

[Routine written intervention asserting the advantages of multiple blood cultures increases their order rate among doctors]

PURPOSE

Obtaining two or more blood culture sets is important for achieving good sensitivity and for detecting contamination. However, many doctors still only order one set for their laboratory testing. We wished to determine if routine written intervention to these doctors could increase the number of multiple blood cultures they ordered.

MATERIALS AND METHODS

On November 11, 2011 at Tokyo Teishin Hospital, we began sending letters asserting the advantages of using multiple blood culture sets to doctors who only ordered solitary blood cultures. The effect of the intervention was determined by measuring the order rate of multiple blood culture sets at the hospital. We compared the order rate one year before intervention with that of one year after. We used a chi-square test (without Yates correction) to analyze the data, and p values less than 0.05 were considered to be statistically significant; all tests were two-tailed.

RESULTS

Before written intervention, the order rate of multiple blood cultures was 41%. This increased significantly to 68% after intervention (p < 0.001). The latter figure was 1.7 times greater than the former (relative risk, 1.7; 95% confidence interval, 1.5-1.8).

CONCLUSION

Routine written educational intervention asserting the advantage of multiple blood cultures led to an increase in their order rate by doctors. While this is a significant increase, it is still insufficient. Therefore, we propose the need for internal policies requiring at least two blood culture sets to ensure better sensitivity and detection of contamination. To enforce these policies, hospital personnel should be allowed to routinely intervene by either sending warning letters to the doctors or displaying this information on the patient's electronic chart.

Utilization of bacteriological culture for increased diagnostic performance at a tuberculosis reference center hospital

The purpose of this study was to assess the increase in positive results of bacteriological diagnostic tests for tuberculosis with the utilization of culture at a referral hospital for tuberculosis (TB). A retrospective analysis was conducted based on the positive bacteriological results obtained at the Júlia Kubistchek Hospital. The number of bacteriological diagnoses was increased by 24.6 % with the utilization of culture of sputum samples and by 56.1% of bronchoalveolar lavage samples. With regard to pleural fluid, all six positive cultures were negative for bacilloscopy. Mycobacterium tuberculosis was isolated in 59.6 % of positive cultures. Since mycobacterial culture was not undertaken for all clinical samples, this procedure is an important laboratory routine at the Júlia Kubistchek Hospital in order to learn the real TB prevalence.

Evaluation of different micro/nanobeads used as amplifiers in QCM immunosensor for more sensitive detection of E. coli O157:H7

Micro/nanobeads with different materials (magnetic, silica and polymer) and different sizes (diameters from 30nm to 970nm) were investigated for their use as amplifiers in a quartz crystal microbalance (QCM) immunosensor for more sensitive detection of Escherichia coli O157:H7. The micro/nanobeads were conjugated with anti-E. coli antibodies. E. coli O157:H7 cells were first captured by the first antibody immobilized on the electrode surface, and then micro/nanobeads labeled secondary antibodies attached to the cells, and finally the complexes of antibody-E. coli-antibody modified beads were formed. The results showed that antibody-labeled beads lead to signal amplification in both the change in frequency (ΔF) and the change in resistance (ΔR). Since the penetration depth of the oscillation-induced shear-waves for a ∼8MHz crystal is limited to 200nm, the interpretation of how the signal is amplified by the adsorbed particles was represented in terms of the coupled-oscillator theory. The amplification is not sensed in terms of increase in mass on the sensor surface. Amplification is sensed as a change in bacterial resonance frequency when the spheres adsorb to the bacteria. The change in the values of ΔF caused by different micro/nanobeads (amplifiers) attaching on target bacterial cells is indicative of the ratio between the resonance frequency of the absorbed bacterial-particle complex (ω(s)), and the resonance frequency of the crystal (ω).

Determination of operating characteristic, retesting, and testing amount probabilities associated with testing for the presence of Salmonella in foods

The relatively small perceived probability associated with retesting a food for the presence of Salmonella at low levels is often considered as one of the reasons that a confirmatory or check-analysis tends to disagree in practice with the results of an original test. Given a retesting process where a retest is only performed to confirm an original positive Salmonella test, the probability that both the original and retest will test positive for Salmonella has been traditionally determined by some as the product of the probabilities of a positive Salmonella test for the original and retest samples. When examining the probabilities associated with the retesting process, we found that our results disagreed with those based on intuitions apparently held by others concerning how these probabilities should be calculated. For Salmonella testing, operating characteristic values were computed to demonstrate the protections afforded by the Salmonella sampling plans presented in the U.S. Food and Drug Administration's Bacteriological Analytical Manual and to obtain the probability of a positive Salmonella test. The geometric distribution was examined for possible utility in determining the probabilities associated with testing amounts, i.e., the number of Salmonella tests needed to obtain a positive test.

Evaluation of the MIT RMID 1000 system for the identification of Listeria species

The Micro Imaging Technology (MIT) 1000 Rapid Microbial Identification (RMID) System is a device that uses the principles of light scattering coupled with proprietary algorithms to identify bacteria after being cultured and placed in a vial of filtered water. This specific method is for pure culture identification of Listeria spp. A total of 81 microorganisms (55 isolates) were tested by the MIT 1000 System, of which 25 were Listeria spp. and 30 a variety of other bacterial species. In addition, a total of 406 tests over seven different ruggedness parameters were tested by the MIT 1000 System to determine its flexibility to the specifications stated in the MIT 1000 System User Guide in areas where they might be deviated by a user to shorten the test cycle. Overall, MIT concluded that the MIT 1000 System had an accuracy performance that should certify this Performance Test Method for the identification of Listeria spp. This report discusses the tests performed, results achieved, and conclusions, along with several reference documents to enable a higher understanding of the technology used by the MIT 1000 System.

Access to tuberculosis diagnosis in Itaboraí City, Rio de Janeiro, Brazil: the patient's point of view

SETTING

Itaboraí Municipality in Rio de Janeiro, Brazil.

OBJECTIVE

To evaluate access to tuberculosis (TB) diagnosis for users of the Family Health Program (FHP) and Reference Ambulatory Units (RAUs).

DESIGN

A cross-sectional study was conducted in Itaboraí City, Rio de Janeiro, Brazil. Between July and October 2007, a sample of 100 TB patients registered consecutively with the TB Control Program was interviewed using the primary care assessment tool. The two highest scores, describing 'almost always' and 'always', or 'good' and 'very good', were used as a cut-off point to define high quality access to diagnosis.

RESULTS

FHP patients were older and had less education than RAU interviewees. Sex and overcrowding did not differ in the two groups. Patient groups did not differ with regard to the number of times care was sought at a unit, transport problems, cost of attending units and availability of consultation within 24 h. Adequate access to diagnosis was identified by 62% of the FHP patients and 53% of the RAU patients (P = 0.01).

CONCLUSION

In Itaboraí, Rio de Janeiro, TB patients believe that the FHP units provide greater access to TB diagnosis than RAUs. These findings will be used by the Department of Health to improve access to diagnosis in Itaboraí.

[Selective decontamination of the digestive tract: repercussions on microbiology laboratory workload and costs, and antibiotic resistance trends]

INTRODUCTION

This study determines the workload and cost of implementing selective digestive decontamination in the microbiology laboratory, and reports the impact on microbial flora and bacterial resistance trends in the intensive care unit (ICU).

METHODS

The total microbiological workload and cost were quantified, as well as the part charged to the petitioning service, in the year before and the year after introducing the procedure. Changes in microbial flora were evaluated and bacterial resistance trends were analyzed over 12 years in 21 sentinel antimicrobial/microorganism combinations.

RESULTS

The workload ascribed to the ICU increased by 10% and cost increased by 1.8% in the period after introduction of the procedure (non-significant differences). The increased workload resulting from epidemiological surveillance cultures was compensated by significant reductions in quantitative endotracheal aspirate cultures, blood cultures, exudate cultures, identification tests with antibiograms, and serologies. The procedure has been associated with a significant decrease in Acinetobacter isolates and a significant increase in Enterococcus. Three significant trends of increased resistance were detected, all of them in Pseudomonas aeruginosa (imipenem, tobramycin, and ciprofloxacin).

CONCLUSIONS

In our hospital, implementation of selective digestive decontamination did not cause a significant increase in the workload or costs in the microbiology laboratory. Selective digestive decontamination was associated with a significant decrease in Acinetobacter, an increase in Enterococcus, and higher resistance to imipenem, tobramycin and ciprofloxacin in P. aeruginosa.

Validation of a modification to Performance-Tested Method 070601: Reveal Listeria Test for detection of Listeria spp. in selected foods and selected environmental samples

A modification to Performance-Tested Method (PTM) 070601, Reveal Listeria Test (Reveal), is described. The modified method uses a new media formulation, LESS enrichment broth, in single-step enrichment protocols for both foods and environmental sponge and swab samples. Food samples are enriched for 27-30 h at 30 degrees C and environmental samples for 24-48 h at 30 degrees C. Implementation of these abbreviated enrichment procedures allows test results to be obtained on a next-day basis. In testing of 14 food types in internal comparative studies with inoculated samples, there was a statistically significant difference in performance between the Reveal and reference culture [U.S. Food and Drug Administration's Bacteriological Analytical Manual (FDA/BAM) or U.S. Department of Agriculture-Food Safety and Inspection Service (USDA-FSIS)] methods for only a single food in one trial (pasteurized crab meat) at the 27 h enrichment time point, with more positive results obtained with the FDA/BAM reference method. No foods showed statistically significant differences in method performance at the 30 h time point. Independent laboratory testing of 3 foods again produced a statistically significant difference in results for crab meat at the 27 h time point; otherwise results of the Reveal and reference methods were statistically equivalent. Overall, considering both internal and independent laboratory trials, sensitivity of the Reveal method relative to the reference culture procedures in testing of foods was 85.9% at 27 h and 97.1% at 30 h. Results from 5 environmental surfaces inoculated with various strains of Listeria spp. showed that the Reveal method was more productive than the reference USDA-FSIS culture procedure for 3 surfaces (stainless steel, plastic, and cast iron), whereas results were statistically equivalent to the reference method for the other 2 surfaces (ceramic tile and sealed concrete). An independent laboratory trial with ceramic tile inoculated with L. monocytogenes confirmed the effectiveness of the Reveal method at the 24 h time point. Overall, sensitivity of the Reveal method at 24 h relative to that of the USDA-FSIS method was 153%. The Reveal method exhibited extremely high specificity, with only a single false-positive result in all trials combined for overall specificity of 99.5%.

Validation of a modification to Performance-Tested Method 010403: microwell DNA hybridization assay for detection of Listeria spp. in selected foods and selected environmental surfaces

A modification to Performance-Tested Method 010403, GeneQuence Listeria Test (DNAH method), is described. The modified method uses a new media formulation, LESS enrichment broth, in single-step enrichment protocols for both foods and environmental sponge and swab samples. Food samples are enriched for 27-30 h at 30 degrees C, and environmental samples for 24-48 h at 30 degrees C. Implementation of these abbreviated enrichment procedures allows test results to be obtained on a next-day basis. In testing of 14 food types in internal comparative studies with inoculated samples, there were statistically significant differences in method performance between the DNAH method and reference culture procedures for only 2 foods (pasteurized crab meat and lettuce) at the 27 h enrichment time point and for only a single food (pasteurized crab meat) in one trial at the 30 h enrichment time point. Independent laboratory testing with 3 foods showed statistical equivalence between the methods for all foods, and results support the findings of the internal trials. Overall, considering both internal and independent laboratory trials, sensitivity of the DNAH method relative to the reference culture procedures was 90.5%. Results of testing 5 environmental surfaces inoculated with various strains of Listeria spp. showed that the DNAH method was more productive than the reference U.S. Department of Agriculture-Food Safety and Inspection Service (USDA-FSIS) culture procedure for 3 surfaces (stainless steel, plastic, and cast iron), whereas results were statistically equivalent to the reference method for the other 2 surfaces (ceramic tile and sealed concrete). An independent laboratory trial with ceramic tile inoculated with L. monocytogenes confirmed the effectiveness of the DNAH method at the 24 h time point. Overall, sensitivity of the DNAH method at 24 h relative to that of the USDA-FSIS method was 152%. The DNAH method exhibited extremely high specificity, with only 1% false-positive reactions overall.

Addendum: ISO culture methods comparative testing of BBL CHROMagar Salmonella prepared plated culture medium

BBL CHROMagar Salmonella (CS) was evaluated for the detection of Salmonella species compared to the International Organization for Standardization (ISO) 6579:2002 reference method media. Raw chicken, raw ground beef, raw fish, lettuce, and shell eggs were evaluated by an independent laboratory. Raw chicken was found to be naturally contaminated with Salmonella; all other matrixes were seeded with Salmonella at a low level. Four Salmonella serovars were used for seeding the food matrixes. A total of 120 food samples were analyzed. The detection and isolation of Salmonella on CS was compared to the ISO culture methods reference media, using the recommended pre-enrichments and selective enrichments. BBL CS produced results comparable to those of the reference methods on all matrixes, resulting in a method agreement of 100% based on the Chi-square results. Known isolates were tested and had a sensitivity of 96.8% and specificity of 94%. No false negatives were found in testing the food matrixes. The results of this study demonstrate that BBL CS is an effective medium for the recovery and detection of Salmonella in raw chicken, raw ground beef, raw fish, lettuce, and shell eggs using ISO method 6579.

Minor modification to official method 2000.14, Reveal for E. coli O157:H7 test in selected foods and environmental swabs (20-hour method): validation of the test for 375 g raw beef samples

A lateral flow immunoassay for Escherichia coli O157:H7 (Reveal E. coli O157:H7, 20-h version), previously validated for 25 g raw ground beef, raw beef cubes, apple cider, lettuce rinse, and environmental swab samples, has been validated for use in testing 375 g samples of raw ground beef and raw beef cubes. The Reveal method, including culture confirmation of positive immunoassay results, was evaluated in comparison to the current reference culture procedure of the U.S. Department of Agriculture-Food Safety and Inspection Service. For raw ground beef, the Reveal and reference methods produced the same number of confirmed positive results. For raw beef cubes, the Reveal method produced more positives than the reference method, but this difference was not statistically significant. The Reveal method exhibited 100% specificity, with no false-positive results obtained on uninoculated control samples. It is recommended that this minor modification to Method 2000.14 be adopted Revised First Action.

USDA FSIS and FDA BAM culture methods BBL CHROMagar Salmonella prepared plated and Difco dehydrated culture media

BBL and Difco CHROMagar Salmonella (CS) was evaluated internally and externally for the recovery of Salmonella in raw chicken, raw ground beef, raw fish, lettuce, and shell eggs. The raw chicken and ground beef were processed according to the U.S. Department of Agriculture, Food Safety and Inspection Service reference methods. The raw fish, lettuce, and shell eggs were processed according to the U.S. Food and Drug Administration, Bacteriological Analytical Manual procedures. Only raw chicken was found to be naturally contaminated with Salmonella; all other matrixes were seeded with an appropriate dilution of organism to achieve fractionally positive results. Salmonella strains were permitted to equilibrate with the culture-negative matrixes for 48 h at 4 degrees C. Twenty 25 g samples of each food matrix plus 5 uninoculated samples were processed. CS prepared plates (CS PPM) and laboratory prepared plates from dehydrated culture media (CS DCM) were evaluated with the reference method media. A total of 16 positive cultures were obtained from the raw chicken samples, 17 in the raw ground beef, 18 in the raw fish and lettuce, and 11 in the shell eggs. A Chi-square analysis was performed on each of the food matrixes. BBL CS produced comparable results with the reference methods on all matrixes, resulting in a method agreement of 100% based on the Chi-square results. In testing known isolates the sensitivity and specificity was determined to be 94%. Specificity improved to 98% when tetrathionate broth enrichment was used. A negative- and false-positive rate of 6% was found with known isolates. No false negatives were found in testing the food matrixes. The performance of the CS prepared plate and laboratory prepared plate was identical.

Genome-based identification and molecular analyses of pathogenicity islands and genomic islands in Salmonella enterica

Pathogenicity islands and genomic islands (GI) are key elements in the evolution of bacterial virulence and environmental adaptation. In Salmonella enterica, Salmonella pathogenicity islands ISPI) confer important virulence traits; however, many of these loci have not been characterized in molecular detail. In this chapter, procedures for the identification and molecular characterization of SPI and GI are described. Based on genome sequence data, bioinformatics approaches allow the identification of putative SPI and GI. The role of these loci can be analyzed after the generation of deletion mutant strains using the Red recombination approach. For further analyses, cosmid libraries of S. enterica genomic DNA are screened for clones harboring entire SPI or GI. Such cosmid clones are then used for complementation of SPI or GI deletions as well as for the transfer of these loci to other bacterial species and subsequent functional assays. This set of methods allows the rapid and efficient analyses of the functions of SPI and GI.

New recommendations for duration of respiratory isolation based on time to detect Mycobacterium tuberculosis in liquid culture

It was hypothesised that the time to detect Mycobacterium tuberculosis in liquid culture of sputum from patients with pulmonary tuberculosis may be a better indicator for the duration of respiratory isolation than sputum smear status. Pre-treatment and during-treatment sputum acid-fast bacilli (AFB) smear and culture results were reviewed in 284 patients with pulmonary tuberculosis. The time to detect M. tuberculosis in liquid culture (TTD-TB) was the number of days from inoculation of the Mycobacterial Growth Indicator Tube to culture detection and visualisation of AFB. The median (interquartile range) TTD-TB for smear group 0 (no bacilli seen) was 14 (12-20) days. This value was used as the standard at which release from isolation could be permitted. In smear group 4 (>9 AFB per high-power field (hpf) in sputum specimens before treatment) patients, the TTD-TB exceeded 14 days after a median of 25 days of treatment. The current authors recommend that patients in smear groups 1 and 2 (1-9 AFB per 100 hpf and 1-9 AFB per 10 hpf in sputum specimens before treatment, respectively) receive treatment in respiratory isolation for 7 days, provided the risk of drug resistance is low. Smear group 3 (1-9 AFB per hpf) and 4 patients should receive treatment in respiratory isolation for 14 and 25 days, respectively. These criteria would have reduced the duration of respiratory isolation by 1,516 days in the 143 study participants with sputum smear-positive pulmonary tuberculosis. Provided clinical and radiographical criteria are satisfactory, use of the time to detect Mycobacterium tuberculosis in liquid culture could enable the duration of respiratory isolation to be predicted from the pre-treatment sputum smear grade. The recommendations enable isolation to end well before sputum becomes smear negative, with considerable benefits to patients and healthcare providers.

Sensitivity of direct plating for detection of high levels of E. coli O157:H7 in bovine fecal samples

To assess the sensitivity of direct plating of bovine fecal samples for detection of Escherichia coli O157:H7, calves (n = 28) were orally inoculated with 10(9) colony-forming units (cfu) per calf of a mixture of three strains of nalidixic acid-resistant E. coli O157:H7, and fecal samples were collected for analysis. One-gram samples from inoculated calves were mixed with 9 mL of Gram-negative broth with vancomycin, cefixime, and cefsoludin. From this suspension, serial dilutions were made (10(-1) to 10(-4)) and spread plated in triplicate on Sorbitol MacConkey agar with nalidixic acid for enumeration of E. coli O157:H7 in fecal samples. Direct plating samples were streaked for isolation on Sorbitol MacConkey agar with cefixime, and tellurite (SMACct). After incubation overnight at 37 degrees C, morphologically typical colonies from direct streak plates were plated onto blood agar and incubated overnight at 37 degrees C; then an indole test was performed on each colony. Indole-positive colonies were confirmed by O157 agglutination and were then plated on SMAC agar with 20 microg/mL nalidixic acid (SMACnal) to confirm nalidixic acid resistance. Overall sensitivity of detection was 32.5% (110/338 samples). Sensitivity to detect fecal samples shedding at above 5 x 10(4) cfu/g was 83% (71/86 samples). Based on these data, direct plating of fecal samples might be an effective way to identify cattle that are likely to be shedding E. coli O157 at high levels.

Do peripheral blood cultures taken in the emergency department influence clinical management?

BACKGROUND

Blood cultures are routinely used to investigate suspected sepsis in the emergency department despite several studies demonstrating their limited influence on patient management.

OBJECTIVES

To quantify the use and clinical relevance of blood cultures obtained in the emergency department.

METHODS

A retrospective study of blood cultures taken in the emergency department between 1 January 2003 and 31 December 2004. Microbiology results and patient records were reviewed to determine the influence of positive cultures on subsequent patient management.

RESULTS

2213 blood cultures were taken in the emergency department over the study period. 132 (6%) yielded a positive result. Three positive cultures cases had incomplete information. Of the remaining 129 positive cultures, 30 (1.4% of all cultures) were "true positives" and 4 (0.18%) influenced subsequent patient management.

CONCLUSIONS

Blood cultures taken in our emergency department rarely yield bacterial growth and over 2 years, only four seemed to directly influence patient management. Better guidelines are required for targeted use of blood cultures in the emergency department.

Do peripheral blood cultures taken in the emergency department influence clinical management?

BACKGROUND

Blood cultures are routinely used to investigate suspected sepsis in the emergency department despite several studies showing their limited influence on patient management.

OBJECTIVES

To quantify the use and clinical relevance of blood cultures obtained in the emergency department.

METHODS

A retrospective study of blood cultures taken in the emergency department between 1 January 2003 and 31 December 2004. Microbiology results and patients' records were reviewed to determine the influence of positive cultures on subsequent patient management.

RESULTS

2213 blood cultures were taken in the emergency department over the study period. 132 (6%) yielded a positive result. Three positive cultures had incomplete information. Of the remaining 129 positive cultures, 30 (1.4% of all cultures) were "true positives" and 4 (0.18%) influenced subsequent patient management.

CONCLUSIONS

Blood cultures taken in our emergency department (Southern General Hospital, Glasgow, UK) rarely yield bacterial growth, and over 2 years only four cultures seemed to directly influence patient management. Better guidelines are required for targeted use of blood cultures in the emergency department.

One-step, nanoparticle-mediated bacterial detection with magnetic relaxation

Acknowledging the need for the development of fast and sensitive bacterial detection methods, we functionalized superparamagnetic iron oxide nanoparticles to identify Mycobacterium avium spp. paratuberculosis (MAP), through magnetic relaxation. Our results indicate that the MAP nanoprobes (1) bind specifically to MAP, (2) can quantify the bacterial target quickly in milk and blood with high sensitivity, and (3) are not susceptible to interferences caused by other bacteria. The use of the described magnetic nanosensors in the identification and quantification of bacteria in clinical and environmental samples is anticipated.

Repeat urine cultures in children who are admitted with urinary tract infections

OBJECTIVE

Urinary tract infections are a common cause of hospitalization in the pediatric population. Hospitalization for urinary tract infections in children usually involves intravenous antibiotics, invasive methods of obtaining sterile urine specimens, and imaging studies to assess the anatomy of the urinary system. The objective of this study was to determine the frequency of positive repeat urine cultures that are obtained after 2 days of antibiotics among pediatric inpatients who are admitted with diagnosed or suspected infections of the urinary tract.

METHODS

A retrospective survey was conducted of all pediatric patients (< or = 18 years of age) who were admitted to Elmhurst Hospital in Queens, New York, with a suspected or diagnosed urinary infection from December 1998 through December 2004. Results of repeat urine cultures that were obtained after 2 days of antibiotics were abstracted from a computerized medical charts database. Nominal data analysis was used to establish the frequency of positive repeat urine cultures.

RESULTS

A total of 328 (54.8%) of 599 eligible admissions met inclusion criteria. Of these 328 admissions, only 1 (0.3%) repeat urine culture was positive after 2 days of antimicrobial therapy.

CONCLUSIONS

Positive repeat urine cultures after 2 days of antibiotics are exceedingly rare. Elimination of mandatory "proof-of-bacteriologic-cure" benchmarks before hospital discharge is supported by this study.

Comparative analysis of a monoclonal antibody-based Streptococcus mutans detection method with selective culture assays using polymerase chain reaction as a gold standard

The aim of this study was to compare a recently developed monoclonal antibody (MAb)-based salivary Streptococcus mutans detection method with various selective media using polymerase chain reaction (PCR) as the gold standard. Salivary S. mutans cells were enumerated with a MAb-based method, along with three commonly used selective media, mitis-salivarius-bacitracin agar (MSB), trypticase yeast-extract cystine sucrose bacitracin agar (TYCSB), and glucose-sucrose-potassium tellurite-bacitracin (GSTB) agar. Statistical analysis showed no significant correlations between each method. With PCR as the standard, a MAb-based detection method was found to provide the highest sensitivity (91%) and specificity (96%) among these four methods. This study demonstrates that the MAb-based detection method may provide more accurate enumeration of salivary S. mutans than selective media.

Determination of the gene content of Salmonella genomes by microarray analysis

Microarray technology provides a convenient and relatively inexpensive way of investigating the genetic content of bacterial genomes by comparative genomic hybridization. In this method, genomic DNA of an unknown bacterial strain of interest and that of a closely related sequenced isolate are hybridized to the same array. Hybridization signals are subsequently translated into gene absence and presence predictions for the experimental strain. Our nonredundant microarray of PCR products representing almost all genes from a number of the sequenced Salmonella enterica serovars (including Typhimurium, Typhi, Paratyphi A, and Enteritidis) allows accurate predictions of gene presence and absence in hundreds of Salmonella isolates on whole genome scale, for a fraction of the cost of complete genome sequencing, or resequencing using tiled oligo-arrays.

Amplified fragment length polymorphism analysis of Salmonella enterica

Amplified fragment length polymorphism (AFLP) is a powerful PCR-based fingerprinting method and has the capacity to reveal variation around the whole genome by selectively amplifying a subset of restriction fragments for comparison. The restriction fragments analyzed are small, and even mutation of 1 bp can be detected. The use of different sets of restriction enzymes or different primer combinations can generate large numbers of different AFLP fingerprints. AFLP is of particular value for studies of closely related strains, such as analysis of variation within a serovar of Salmonella enterica. We present here protocols for both radioactively labeled and fluorescent dye-labeled AFLP analyses that are also applicable to other bacterial species. Fluorescent AFLP has proved to be reproducible and capable of standardization.

Evaluación de la capacidad invasiva de las micobacterias no pigmentadas de crecimiento rápido mediante el estudio de la morfología de las microcolonias en fibroblastos

OBJECTIVE

The invasive capacity of rapidly-growing nonpigmented mycobacteria strains was evaluated by means of a fibroblast microcolony assay and related to the colony phenotype on Middlebrook 7H11 and to the clinical significance of the isolates.

METHODS

Twenty-nine strains [Mycobacterium chelonae (8), M. fortuitum (6), M. peregrinum (5), M. abscessus (5), M. mucogenicum (4) and M. septicum (1)], proceeding from a bacterial collection and clinical isolates, were evaluated. The smooth or rough phenotype of the colonies was assessed in Middlebrook 7H11 medium. Intracellular invasiveness was determined by the fibroblast-microcolony assay described by Shepard. Quantitative culture characteristics were compared with Student's t-test, and qualitative characteristics with Fisher's exact test.

RESULTS

No significant differences were found between colonies with different phenotypes or strains having a different clinical significance, except for two strains of Mycobacterium chelonae isolated from cases of catheter-related bacteremia, which showed elongated microcolonies. M. fortuitum and M. peregrinum strains showed larger microcolonies than M. chelonae, M. abscessus and M. mucogenicum, and displayed a fluffy appearance, while the latter two strains showed rounded colonies.

CONCLUSION

Very few strains of mycobacteria had invasive capacity and the majority of strains isolated from human infections do not show this characteristic; hence this trait is not essential for mycobacteria to cause infection in humans.

Sensitivity of Ziehl-Neelsen method for centrifuged deposit smears of sputum samples transported in cetyl-pyridinium chloride

BACKGROUND & OBJECTIVES

Sensitivity of Ziehl-Neelsen (ZN) method is known to be low for liquefied sputum smears. Information on the ZN sensitivity for centrifuged deposit smears is not known. This study was carried out to determine the sensitivity of ZN method for acid fast bacilli (AFB) in centrifuged deposit smears and liquefied sputum smears made from sputum samples transported in cetyl-pyridinium chloride (CPC) solution.

METHODS

Liquefied sputum smears and the corresponding centrifuged deposit smears from each of the 607 consecutive sputum samples collected from tuberculosis patients admitted to receive treatment transported in CPC were read by the same readers and their results compared with culture results.

RESULTS

A significantly (P<0.001) higher proportion of samples were positive in centrifuged deposit smears (40%) compared to liquefied sputum smears (30%). The results of 341 culture-positive specimens revealed that the sensitivity of ZN method was 47 per cent using liquefied sputum smears and 63 per cent using centrifuged deposit smears (P<0.001).

INTERPRETATION & CONCLUSION

Our study demonstrated that the sensitivity of ZN method for AFB in centrifuged deposit smears and liquefied sputum smears was reduced if sputum samples are transported in CPC solution.

Microbiological assay for the determination of telithromycin in tablets

This study describes the development and validation of a microbiological assay, applying the cylinder-plate method, for the determination of the antibiotic telithromycin. The microbiological method consisted of a cylinder-plate agar diffusion assay using Micrococcus luteus ATCC 9341 as the test microorganism. The response graphs for standard and sample solutions were linear (r = 0.9987), and no parallelism deviations were detected in the tested concentrations (0.25, 0.5, and 1.0 microg/mL). The interday precision was 2.67%. Recovery values were between 96.75 and 100.91%. A preliminary stability study of telithromycin showed that the microbiological assay is specific for the determination of telithromycin in the presence of its degradation products. The proposed method allows the quantitation of telithromycin in pharmaceutical dosage form and can be used for drug analysis in routine quality control.

Modification to the AOAC Sporicidal Activity of Disinfectants Test (Method 966.04): collaborative study

In an effort to improve AOAC Method 966.04, the Sporicidal Activity of Disinfectants Test, selected modifications to the procedure were evaluated in a collaborative study. Method 966.04 is used to generate efficacy data to support the product registration of sporicides and sterilants. The method is a carrier-based test that provides a qualitative measure of product efficacy against spores of Bacillus subtilis and Clostridium sporogenes. The use of garden soil extract and the lack of standard procedures for the enumeration of spores and neutralization of the test chemicals have been considered problematic for many years. The proposed modifications were limited to the B. subtilis and hard surface carrier (porcelain penicylinder) components of the method. The study included the evaluation of a replacement for soil extract nutrient broth and an establishment of a minimum spore titer per carrier, both considered crucial for the improvement and utilization of the method. Additionally, an alternative hard surface material and a neutralization confirmation procedure were evaluated. To determine the equivalence of the proposed alternatives to the standard method, 3 medium/carrier combinations, (1) soil extract nutrient broth/porcelain carrier (current method), (2) nutrient agar amended with 5 microg/mL manganese sulfate/porcelain carrier, and (3) nutrient agar amended with 5 microg/mL manganese sulfate/stainless steel carrier were analyzed for carrier counts, HCI resistance, efficacy, quantitative efficacy, and spore wash-off. The test chemicals used in the study represent 3 chemical classes and are commercially available antimicrobial liquid products: sodium hypochlorite (bleach), glutaraldehyde, and a combination of peracetic acid and hydrogen peroxide. Four laboratories participated in the study. The results of the spore titer per carrier, HCI resistance, efficacy, and wash-off studies demonstrate that amended nutrient agar in conjunction with the porcelain is comparable to the current method, soil extract nutrient broth/porcelain. The nutrient agar method is simple, inexpensive, reproducible, and provides an ample supply of high quality spores. Due to the current use of porcelain carriers for testing C. sporogenes, it is advisable to retain the use of porcelain carriers until stainless steel can be evaluated as a replacement carrier material for Clostridium. The evaluation of stainless steel for Clostridium has been initiated by the Study Director. Study Director recommendations for First Action revisions are provided in a modified method.

Development and evaluation of a rapid, simple, and sensitive immunochromatographic assay to detect thermostable direct hemolysin produced by Vibrio parahaemolyticus in enrichment cultures of stool specimens

Thermostable direct hemolysin (TDH) is considered to be a major virulence factor in Vibrio parahaemolyticus, and most cases of V. parahaemolyticus diarrhea in humans are caused by tdh gene-positive strains. In the present study, we developed an immunochromatographic assay to detect TDH (TDH-ICA) and evaluated the utility of TDH-ICA for the diagnosis of V. parahaemolyticus diarrhea. TDH-ICA allowed the detection of 0.2 ng/ml of TDH within 10 min. Fecal homogenates were spiked with various numbers of tdh-positive V. parahaemolyticus organisms, and their enrichment cultures were tested with TDH-ICA. The results of detection of TDH in the enrichment cultures by TDH-ICA were in accord with the results of recovery of the spiked V. parahaemolyticus organisms from the enrichment cultures by plating onto thiosulfate-citrate-bile salts-sucrose agar. When enrichment cultures of 217 stool specimens from patients with diarrhea were tested with TDH-ICA, the TDH-ICA results showed 100% sensitivity and specificity compared to the results of isolation of V. parahaemolyticus from the stool specimens by a conventional bacterial culture test. Since TDH-ICA was able to detect TDH in a fecal enrichment culture within 10 min, TDH-ICA testing of a fecal enrichment culture could be completed rapidly and easily within approximately 16 h, including incubation time for the fecal enrichment culture. These results indicate that TDH-ICA is a rapid, simple, and sensitive TDH detection method and that TDH-ICA testing of a fecal enrichment culture is useful as an adjunct to facilitate the early diagnosis of V. parahaemolyticus diarrhea.

Prospective study of the value of quantitative culture of organisms from blood collected through central venous catheters in differentiating between contamination and bloodstream infection

Collection of blood through a central venous catheter for the diagnosis of bacteremia is a debated topic. Quantitative cultures of organisms from blood collected through central venous catheters were found to be highly sensitive, specific, and predictive of bacteremia, especially when a cutoff point of 15 colonies of skin organisms was used.

Effective detection of toxigenic Clostridium difficile by a two-step algorithm including tests for antigen and cytotoxin

We evaluated a two-step algorithm for detecting toxigenic Clostridium difficile: an enzyme immunoassay for glutamate dehydrogenase antigen (Ag-EIA) and then, for antigen-positive specimens, a concurrent cell culture cytotoxicity neutralization assay (CCNA). Antigen-negative results were > or = 99% predictive of CCNA negativity. Because the Ag-EIA reduced cell culture workload by approximately 75 to 80% and two-step testing was complete in < or = 3 days, we decided that this algorithm would be effective. Over 6 months, our laboratories' expenses were US dollar 143,000 less than if CCNA alone had been performed on all 5,887 specimens.

Performance assessment of the DR. MTBC Screen assay and the BD ProbeTec ET system for direct detection of Mycobacterium tuberculosis in respiratory specimens

The performance of the DR. MTBC PCR-based assay and the BD ProbeTec ET Mycobacterium tuberculosis Complex Direct Detection (DTB) assay for the direct detection of Mycobacterium tuberculosis was evaluated using 1,066 consecutive clinical respiratory samples collected from 494 patients who did not have old cases of pulmonary tuberculosis and were not receiving antituberculosis treatment at National Taiwan University Hospital from January to February 2005. The results of both assays were compared to the "gold standard" of combined culture results and clinical diagnosis. The overall sensitivity and specificity of the DR. MTBC Screen assay were 56.6% and 98.9%, respectively, and of the DTB assay were 63.2% and 98.4%, respectively. The positive and negative predictive values for the DR. MTBC Screen assay were 84.5% and 95.4%, respectively, and for the DTB assay were 81.7% and 96.0%, respectively. The DR. MTBC Screen assay produced 11 false-positive results for 11 patients, including three samples yielding non-M. tuberculosis mycobacteria (one each for M. abscessus, a mixture of M. abscessus and M. chelonae, and unidentified non-tuberculosis mycobacteria). The DTB assay produced 15 false-positive results for 13 patients, including five samples from four patients yielding non-tuberculosis mycobacteria (two for M. abscessus, one for a mixture of M. abscessus and M. chelonae, and two for unidentified non-tuberculosis mycobacteria). This study demonstrated that the DR. MTBC Screen assay has a similar diagnostic value but fewer false-positive results than the DTB assay for respiratory specimens.

Comparison of testing methods for detection of decreased linezolid susceptibility due to G2576T mutation of the 23S rRNA gene in Enterococcus faecium and Enterococcus faecalis

E-test, Vitek 2, MicroScan, agar dilution, and disk diffusion were compared for detection of decreased linezolid susceptibility due to 23S rRNA gene G2576T mutation among 32 clinical Enterococcus strains initially reported as intermediate or resistant by E-test alone or Vitek 2 confirmed by E-test. Agar and broth dilution methods were in concordance with PCR detection of the mutation, and disk diffusion was somewhat less sensitive but equally specific.

Sensitivity of Escherichia coli O157 detection in bovine feces assessed by broth enrichment followed by immunomagnetic separation and direct plating methodologies

In order to more precisely predict food safety risks, the fecal presence of food-borne pathogens among animals at slaughter must be correctly determined. Quantification of Escherichia coli O157 is also desirable. In two separate experiments, detection and enumeration of a nalidixic acid-resistant strain of E. coli O157 in bovine feces was assessed by culture on MacConkey agar supplemented with nalidixic acid (MACnal) and compared to overnight broth enrichment followed by immunomagnetic separation (IMS) and to direct plating of dilutions of bovine feces onto sorbitol MacConkey agar containing cefixime and tellurite (SMACct). The sensitivity of detection of E. coli O157 by both direct plating and IMS was highly dependent upon the initial concentration of the target organism in the sample. Sensitivity of detection by IMS was poor below 100 CFU/g but was better, and not affected by initial E. coli O157 numbers, above this concentration. Sensitivity of detection of E. coli O157 in bovine feces at low initial concentrations is very poor for both direct plating and IMS. Direct plating of dilutions of bovine feces on SMACct can be used to determine the magnitude of fecal E. coli excretion among cattle excreting greater than 100 CFU/g. Among positive samples identified by direct plating on SMACct, the direct counts of E. coli O157:H7 were highly correlated with the estimates obtained with the MACnal plates (r = 0.88, P < 0.001). Because the majority of cattle excrete less than 10(2) CFU E. coli O157/g feces, most studies, including those using IMS methods, probably grossly underestimate the prevalence of E. coli O157 in cattle.

Sensitivities of antigen detection and PCR assays greatly increased compared to that of the standard culture method for screening for group B streptococcus carriage in pregnant women

Group B streptococcus (GBS) is a major cause of serious infections in neonates. The 2002 revised guidelines of the Centers for Disease Control and Prevention (CDC) for the prevention of perinatal GBS disease recommend that all pregnant women be screened for GBS carriage at between 35 and 37 weeks of gestation and that intrapartum antibiotic prophylaxis be given to carriers. We studied the performances of four different GBS detection assays in the context of antenatal screening. Between May and August 2004, the 605 vaginorectal swab specimens received at our bacteriology laboratory for GBS antenatal detection were tested by the four assays. The standard culture method was done according to the CDC recommendations. The three experimental assays performed with the growth from the selective enrichment (LIM) broth (Todd-Hewitt broth with 15 mug/ml nalidixic acid and 10 mug/ml colistin) after overnight incubation were a GBS antigen detection assay (PathoDx) and two PCR assays (for cfb and scpB). The most accurate assay was the scpB PCR (sensitivity, 99.6%; specificity, 100%), followed by the cfb PCR (sensitivity, 75.3%; specificity, 100%), GBS antigen detection (sensitivity, 57.3%; specificity, 99.5%), and standard culture (sensitivity, 42.3%; specificity, 100%). The GBS antigen detection assay was found to be more sensitive than the standard culture method, and moreover, the assay has a low cost and is easy to perform in all obstetrical centers which have access to the most basic of diagnostic microbiology services. We believe that antigen detection on incubated LIM broth should replace the standard culture method for screening for GBS carriage at 35 to 37 weeks of gestation. The impact of the greater sensitivities of PCR assays on the diminution of neonatal GBS infections remains to be demonstrated.

Evaluation of a rapid Gram stain interpretation method for diagnosis of bacterial vaginosis

A simple Gram stain evaluation for the diagnosis of bacterial vaginosis was assessed in comparison to Nugent's method. The sensitivity (90%), specificity (94%), positive and negative predictive values (90% and 94%), and good interobserver agreement obtained indicate that the test method can be performed reliably in the routine clinical microbiology laboratory.

Accuracy of three automated systems (MicroScan WalkAway, VITEK, and VITEK 2) for susceptibility testing of Pseudomonas aeruginosa against five broad-spectrum beta-lactam agents

One hundred recent clinical Pseudomonas aeruginosa isolates were used to assess the quantitative (MIC) and qualitative (susceptibility category) accuracies of the MicroScan WalkAway, VITEK, and VITEK 2 automated susceptibility test systems when five-broad spectrum beta-lactams, aztreonam, cefepime, ceftazidime, imipenem, and piperacillin-tazobactam, were tested. Isolates were selected so that the MICs for the isolates overrepresented the MICs near the breakpoints to assess precisely the agreement between the results obtained with the automated systems and the results obtained by the reference tests. The categorical and MIC results from the automated systems were compared to the consensus result of three reference methods: broth microdilution, agar dilution, and disk diffusion. The consensus categorical testing (susceptibility and resistance) rates were 47 and 27%, respectively, for aztreonam; 59 and 14%, respectively, for cefepime; 44 and 43%, respectively, for ceftazidime; 71 and 19%, respectively, for imipenem; and 50 and 50%, respectively, for piperacillin-tazobactam. All systems tested exhibited a high, unacceptable level of very major (false-susceptible) errors for piperacillin-tazobactam (19 to 27%). Major (false-resistant) error rates were generally acceptable (0 to 3%), but minor error rates were elevated (8 to 32%) for cefepime (VITEK 2 and VITEK) and for aztreonam (all three systems), leading to consistent trends toward false resistance. Manufacturer reevaluation of these automated systems for the testing of selected beta-lactams with current clinical isolates of P. aeruginosa that exhibit contemporary resistance mechanisms would be prudent to minimize the potential for serious reporting errors.