Chromogenic Agar Plates Research Articles

The performance of a resazurin chromogenic agar plate with a combined disc method for rapid screening of extended-spectrum-β-lactamases, AmpC β-lactamases and co-β-lactamases in Enterobacteriaceae.

A promising means of rapid screening of extended-spectrum-β-lactamase (ESBL), AmpC β-lactamase, and co-production of ESBL and AmpC that combines resazurin chromogenic agar (RCA) with a combined disc method is here reported. Cefpodoxime (CPD) discs with and without clavulanic acid (CA), cloxacillin (CX) and CA+CX were evaluated against 86 molecularly confirmed β-lactamase-producing Enterobacteriaceae, including 15 ESBLs, 32 AmpCs, nine co-producers of ESBL and AmpC and 30 carbapenemase producers. The CA and CX synergy test successfully detected all ESBL producers (100% sensitivity and 98.6% specificity) and all AmpC producers (100% sensitivity and 96.36% specificity). This assay also performed well in screening for co-existence of ESBL and AmpC (88.89% sensitivity and 100% specificity). The RCA assay is simple and inexpensive and provides results within 7 hr. It can be performed in any microbiological laboratory, in particular, in geographic regions in which ESBL, AmpC or co-β-lactamase-producing Enterobacteriaceae are endemic.

Colonisation with extended-spectrum beta-lactamase (ESBL) not detected in a prevalence study.

The Mid-West of Ireland has higher than average national rates of invasive extended-spectrum beta-lactamase (ESBL) bloodstream infections and carbapenemase-producing Enterobacteriaceae (CPE), with increasing numbers of ESBL isolates detected in community-dwelling patients. To conduct a point prevalence study in a convenience sample of the Mid-West population with the aim of determining the extent of ESBL colonisation. Utilising anonymised community stool samples that had completed routine analysis, we conducted a point prevalence study over a 4-week period on all samples that met defined inclusion and exclusion criteria. Limited epidemiological data was recorded: (1) age of patient, (2) gender, and (3) sender location. From these stool specimens, rectal swabs were inoculated (eSwab™ 480CE, Copan, Italy), which were subsequently cultured on selective chromogenic agar (Colorex™ ESBL). Culture plates were incubated aerobically at 37°C for 24h. Of 195 samples processed, 58% (n=112) were from females. The median patient age was 62.4years (range 20-94years). 186 samples (95%) originated from general practitioner clinics. During the study period, only nine eligible stool samples were received from LTCF (6 public). From 195 Colorex™ ESBL chromogenic agar plates cultured, no ESBL-producing organisms were detected. This community point prevalence study did not identify ESBL colonisation despite high numbers of patients with invasive ESBL bloodstream infections presenting for admission in our institution. We believe this may be because of our small sample size. Data regarding antimicrobial exposure and other risk factors for ESBL colonisation were also not available. We remain vigilant for ESBL-producing organisms.

High Nasal Carriage Rate of Staphylococcus aureus Containing Panton-Valentine leukocidin- and EDIN-Encoding Genes in Community and Hospital Settings in Burkina Faso.

The objectives of the present study were to investigate the rate of S.aureus nasal carriage and molecular characteristics in hospital and community settings in Bobo Dioulasso, Burkina Faso. Nasal samples (n = 219) were collected from 116 healthy volunteers and 103 hospitalized patients in July and August 2014. Samples were first screened using CHROMagar Staph aureus chromogenic agar plates, and S. aureus strains were identified by mass spectrometry. Antibiotic susceptibility was tested using the disk diffusion method on Müller-Hinton agar. All S. aureus isolates were genotyped using DNA microarray. Overall, the rate of S. aureus nasal carriage was 32.9% (72/219) with 29% in healthy volunteers and 37% in hospital patients. Among the S. aureus isolates, only four methicillin-resistant S. aureus (MRSA) strains were identified and all in hospital patients (3.9%). The 72 S. aureus isolates from nasal samples belonged to 16 different clonal complexes, particularly to CC 152-MSSA (22 clones) and CC1-MSSA (nine clones). Two clones were significantly associated with community settings: CC1-MSSA and CC45-MSSA. The MRSA strains belonged to the ST88-MRSA-IV or the CC8-MRSA-V complex. A very high prevalence of toxinogenic strains 52.2% (36/69), containing Panton-Valentine leucocidin- and EDIN-encoding genes, was identified among the S. aureus isolates in community and hospital settings. This study provides the first characterization of S. aureus clones and their genetic characteristics in Burkina Faso. Altogether, it highlights the low prevalence of antimicrobial resistance, high diversity of methicillin-sensitive S. aureus clones and high frequency of toxinogenic S. aureus strains.

Microdot method: used with chromogenic agar is a useful procedure for sanitary monitoring in aquaculture

The microdot method is a downscaling methodology of traditional tenfold serial dilution procedure used in microbiology. The microdot method uses 100 µL for serial dilution and count colonies in a spot of 10 µL. In this study we counted colonies directly in a chromogenic agar plate to determine, at the same time, the presence and cell concentration of target bacteria required for sanitary monitoring of Chilean export fishery products. Due to among importers countries the most concerning bacteria included in sanitary monitoring are Escherichia coli , Listeria monocytogenes and Staphylococcus aureus , we used the chromogenic agar; CHROMagar ECC, CHROMagar Listeria and Baird Parker agar, respectively. The results shows no differences between quantitative results obtained with microdot and traditional method during the quantification of a culture of Escherichia coli (1.5 L). The sensitivity and specificity of the microdot method in association with each chromogenic agar was demonstrated in vitro with reference strains. In addition, the usefulness in sanitary monitoring of aquaculture procedures was evaluated in Artemia salina tanks. This method did not detected sanitary problems in surface water. Although other colonies grown in the chromogenic agar plate, their morphological and chromogenic properties not correspond to Escherichia coli , Listeria monocytogenes and Staphylococcus aureus , being identified as Salmonella enterica subsp. enterica, Microbacterium sp., Bacillus sp. and Staphylococcus pasteuri by 16S rRNA gene sequence analysis. Hence, we propose the microdot chromogenic method as a low cost, specific and reliable procedure for sanitary monitoring of aquaculture procedures.

Automatic Digital Plate Reading for Surveillance Cultures.

The automation of specimen processing and culture workup has rapidly emerged in clinical microbiology laboratories throughout the world and more recently in the United States. While many U.S. laboratories have implemented some form of automated specimen processing and some have begun performing digital plate reading, automated colony analysis is just beginning to be utilized clinically. In this issue of the Journal of Clinical Microbiology, M. L. Faron et al. (J Clin Microbiol 54:2470-2475, 2016, http://dx.doi.org/10.1128/JCM.01040-16) report the results of their evaluation of the performance of the WASPLab Chromogenic Detection Module (CDM) for categorizing chromogenic agar plates as negative or "nonnegative" for vancomycin-resistant enterococci (VRE). Their major finding was 100% sensitivity for detection of "nonnegative" specimens using CDM compared to manual methods for specimens plated on two different types of VRE chromogenic agar plates. Additionally, utilization of digital plate reading in conjunction with automated colony analysis was predicted to result in significant savings based on greatly reduced labor costs.

A combined disc method with resazurin agar plate assay for early phenotypic screening of KPC, MBL and OXA-48 carbapenemases among Enterobacteriaceae.

To validate a combined disc method along with resazurin chromogenic agar for early screening and differentiation of Klebsiella pneumoniae carbapenemase, metallo-β-lactamase and OXA-48 carbapenemase-producing Enterobacteriaceae. The combined disc test comprising of meropenem alone and with EDTA, phenylboronic acid or both EDTA and phenylboronic acid, and temocillin alone were evaluated with the resazurin chromogenic agar plate assay against a total of 86 molecularly confirmed Enterobacteriaceae clinical isolates (11 metallo-β-lactamases, eight Kl.pneumoniae carbapenemases, 11 OXA-48, 32 AmpC and 15 extended-spectrum-β-lactamase producers and nine co-producers of extended-spectrum-β-lactamase and AmpC). The inhibition zone diameters were measured and interpreted at 7h for the presence of carbapenemase. All carbapenemase producers were phenotypically distinguished by this assay with 100% sensitivity and specificity. This early phenotypic method is very simple, inexpensive, and reliable in the detection and differentiation of carbapenemase-producing Enterobacteriaceae. It could be exploited in any microbiological laboratory for diagnosis of these recalcitrant bacteria. This assay poses excellent performance in discrimination of Kl.pneumoniae carbapenemase, metallo-β-lactamase and OXA-48 carbapenemases within 7h, which is much faster than conventional disc diffusion methods. The rapid detection could help clinicians screen patients, control infection and provide epidemiological surveillance.

Evaluation of two commercially available chromogenic media for confirmation of methicillin-resistant Staphylococcus aureus from human, animal, and food samples

We compared the diagnostic performance of two chromogenic media, Brilliance MRSA 2 agar (Thermo Fisher Scientific) and ChromID MRSA agar (bioMérieux), for MRSA confirmation of 239 Staphylococcus aureus isolates from clinical, animal and food samples. Statistically significant differences were not observed between MRSA confirmation by mecA/mecC PCR, and by culture in both chromogenic media. However, a statistically significant difference was observed between the results obtained by both chromogenic media (p=0.003). Segregated analysis of the results depending on the origin of the isolates (clinical, animal, and food) revealed a significant lower performance in the MRSA confirmation of food-derived isolates by using Brilliance MRSA 2 agar in comparison to PCR confirmation (p=0.003) or ChromID MRSA agar (p<0.001). Both chromogenic media provided a good diagnostic performance for detection of MRSA isolates of human and animal origin. In conclusion, the use of chromogenic agar plates for MRSA confirmation of S. aureus isolates can provide a good diagnostic performance (sensitivity >92% and specificity >89%) regardless of the type of chromogenic media used or the origin of the S. aureus isolates. However, our results revealed a lower diagnostic performance for MRSA confirmation of S. aureus isolates from food samples by using Brilliance MRSA 2 agar.

Antibiofilm efficacy evaluation of a bioelectric dressing in mono- and multi-species biofilms.

Chronic infections are often related to the formation of single or polymicrobial biofilms, which lead to hard-to-treat infections, difficult wound management, and recurrent infections. In this study, we evaluated in vitro antibiofilm properties of a silver and zinc bioelectric dressing (Procellera). We customised and established a poloxamer biofilm model using glass coverslips for the efficacy evaluation of the bioelectric dressing. For antimicrobial susceptibility testing, each bacterial pathogen was diluted to 10(5)CFUs/ml, mixed with 30% poloxamer hydrogels and dropped onto round glass coverslips (25mm diameter) as an abiotic support. Additionally, we mixed four bacterial strains and developed multi-species biofilms in the poloxamer model to examine anti-biofilm efficacy testing against polymicrobial biofilms. After 24 hours incubation, we observed significant inhibition of bacterial growth in nine pathogens (∼2- or 3-fold log10 reduction) compared to controls (no treatment, gauze, and blank polyester with no silver and zinc). The smallest effect was seen with Enterococcus faecalis strain where there was approximately a 1-fold log10 reduction of microbial growth. The antibiofilm efficacy against multi-species (four pathogens) biofilms, evaluated on chromogenic agar plates, was 1- or 2-fold log10 reduction compared to controls. This poloxamer biofilm model was easy to set up, simple to apply, and demonstrated appropriate biofilm formation. The data showed the formation of biofilms inoculated with either single or polymicrobial bacteria under no shear condition, and the bioelectric dressing tested in this study showed effective antibiofilm activity against both the mono- and multi-species biofilms. None. The opinions or assertions contained here are the private views of the authors, based on scientific investigation, and are not to be construed as official or as reflecting the views of the US Department of the Army, the Department of Defense, the Department of Veterans Affairs, or the Henry M. Jackson Foundation for the Advancement of Military Medicine.

Vancomycin Resistant Enterococci Infections in Trinidad and Tobago

Aims: To document Vancomycin Resistant Enterococci (VRE) infections prevalence, risk factors, antimicrobial susceptibility patterns and evaluation of chromogenic plates in identifying VRE isolates in Trinidad and Tobago. Study Design : This was a cross sectional prospective observational and descriptive study . Place and Duration of Study: Study was carried out in all major regional hospitals in Trinidad & Tobago over a four year period, 2009 to 2013. Methodology : All cases of Enterococcus infections from major hospitals in the country were reviewed. Standardized questionnaire was used to analyze epidemiological and clinical data of VRE infected patients. Enterococcal speciation, minimum inhibitory concentrations (MIC) were evaluated using Microscan Walk Away 96SI (Siemens, USA). Isolates were further identified using 6.5% NaCl and pyrrolidonyl arylamidase activity according to CLSI guidelines. Brain Heart Infusion agar, Bile esculin azide agar containing 6 mg/L of vancomycin and chromogenic agar plates Chromagar VRE and chrom ID VRE were used to screen and confirm VRE isolates Results: A low (3.9%) VRE infections were encountered from 1,141 enterococcal infections

Carbapenem-resistantKlebsiella pneumoniaecolonization at liver transplantation: A management challenge

(CR-KP) and perhaps to die for this infection (1-4). Hence, different preventive strategies for patients colonized with CR-KP have been advocated, varying from the selective intestinal decontamination to the avoidance of transplantation. However, literature data on the real incidence and timing of invasive infection with CR-KP among colonized patients underwent LT are limited and confusing. To investigate the incidence rate of post surgical CR-KP infection within 30 and 60 days after LT among patients colonized and no colonized at transplantation, we performed a matched case-control study at our 1,350-bed teaching hospital, from July 2011 to June 2013. Matching was performed at a ratio of 1:2 according to the age, sex and Model-for End-stage-Liver-Disease (MELD) score before transplantation. If there were several potential matching control patients, the control patient closest to the case patient in age and MELD was selected. Each patient was included only once. Rectal swabs (RSs) for carrying out colonization with CR-KP were routinely performed in all LT candidates monthly until LT, and at the time of hospital admission immediately prior to transplant. RSs were then repeated every week after LT until hospital discharge. Isolation and contact precautions were activated for patients found to be CR-KP carriers, but no eradication treatment was started in patients without invasive disease. Samples were inoculated on a chromogenic agar plate (Oxoid Brilliance CRE, Thermo Fisher Scientific, United Kingdom) containing a carbapenem antibiotic as selective agent. Biochemical identification and antimicrobial susceptibility testing of isolates were further carried out using the Vitek 2 semi-automated system (Biomerieux, Marcy l’Etoile, France). Overall, 10 out of the 139 (7.2%) patients admitted for LT were found to be CR-KP carriers at LT. Comparison of cases and controls is shown in Table 1. Page 3 of 7John Wiley & Sons, Inc.Liver Transplantation

P168 Comparison of five urine chromogenic agar plates for isolation and identification of urinary tract pathogens

P168 Comparison of five urine chromogenic agar plates for isolation and identification of urinary tract pathogens

Blood pressure cuffs as a vector for transmission of multi‐resistant organisms: Colonisation rates and effects of disinfection

Blood pressure (BP) cuffs are potential vectors for transmission of multi-resistant organisms (MROs). The present study aims to determine MRO colonisation rates in BP cuffs from areas of high patient flow as an assessment of the quality of disinfection and infection control practices. BP cuffs in the ED, high dependency unit (HDU) and operating theatres (OT) were prospectively examined after routine disinfection procedures. Swabs collected from the inner and outer surfaces of BP cuffs during inter-patient intervals were plated onto replicate organism detection and counting, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) chromogenic agar plates to detect rates of bacterial, MRSA and VRE colonisation, respectively. High bacterial colonisation rates were detected in BP cuffs from all three areas. BP cuffs from OT were significantly less colonised compared with cuffs from HDU and ED; 76% versus 96% and 100% (P < 0.0001) for inner surfaces and 86% versus 98% and 100% (P < 0.0001) for outer surfaces, respectively. Equivalent or higher bacterial growth was observed on the inner surface compared with outer surface in 54%, 84% and 86% of BP cuffs from OT, HDU and ED, respectively. MRSA was detected in 3 of 150 (2%) swabs collected, but no VRE was detected. Although MRSA and VRE were infrequently isolated, current disinfection and infection control protocols need to be improved given the greater recovery of organisms from the inner compared with outer surfaces of BP cuffs.

Towards a phenotypic screening strategy for emerging β-lactamases in Gram-negative bacilli

The purpose of this manuscript was to review recent literature and guidelines regarding phenotypic detection of emerging β-lactamases [extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases and carbapenemases] in Gram-negative bacilli (GNB) in order to formulate recommendations on best practice to screen for them. We conclude that chromogenic ESBL screening agar plates are suitable to screen for ESBL-producing Enterobacteriaceae directly from clinical samples. Furthermore, ceftazidime (CAZ) and ceftriaxone or cefotaxime (CTX) are the indicator antimicrobial agents of choice for ESBL detection in GNB. In non-inducible Enterobacteriaceae, the combined double-disk synergy test (CDDST) with at least CTX and CAZ and additionally cefepime as indicators is the preferred ESBL confirmation assay. The two most suitable ESBL confirmation strategies in AmpC co-producing Enterobacteriaceae are adapted CDDSTs: (i) with addition of 3-aminophenylboronic acid to CTX and CAZ disks; and (ii) with addition of cloxacillin (CLOX) to Mueller–Hinton agar. Reduced cefoxitin susceptibility and decreased susceptibility to cefotetan are regarded as suitable screening tests for plasmid-mediated and derepressed AmpC production. A CLOX-based CDDST with CTX and CAZ as indicators is considered to be the best AmpC confirmation assay. Finally, in Enterobacteriaceae isolates we suggest to screen for carbapenemases with a 0.5μg/mL meropenem screening breakpoint. For class A carbapenemase confirmation, the home-prepared as well as the commercially available boronic acid-based CDDST can be considered. For metallo-β-lactamase confirmation, ethylene diamine tetra-acetic-acid-based home-prepared assays are recommended. The most suitable method (CDDST or DDST) and indicator antimicrobial agent(s) vary depending on the bacterial genus.

Infection Risk from Surgeons' Eyeglasses

To assess bacterial contamination of 20 eyeglasses from surgeons. 40 samples were taken from the nose pad (n=20) and earpiece (n=20) of 20 eyeglasses from orthopaedic surgeons using a sterile swab stick soaked in sterile distilled water. Swabs were incubated and inoculated onto 3 plates: Staphylococcus/Streptococcus agar plate, Mannitol salt plate, and Chromogenic agar plate. Organisms isolated were identified. Of 20 eyeglasses, 19 were contaminated with Staphylococcus epidermidis (3 of them additionally grew S haemolyticus or S xylosus) and the remaining one grew S aureus . Eyeglasses are a source of surgical infection. Contamination can be caused by direct contact of the eyeglasses to the wound and indirect contact by the surgeon's fingers, splashes from saline irrigation, and through air. Therefore, disinfection should be performed for eyeglasses of surgeons. The use of surgical visor masks or filtered exhaust helmets (space suits) are alternatives.

A cost-effective protocol for screening patients for methicillin-resistant Staphylococcus aureus

The incidence of hospital-acquired infection with methicillin-resistant Staphylococcus aureus (MRSA) is rising worldwide. Rapid identification of MRSA carriers is an important step in reducing the risk of transmission to other patients. Molecular methods are increasingly popular but are technically demanding and expensive. This study assesses the modification of one of the commercially available latex agglutination tests (Mastalex-MRSA) for the identification of penicillin-binding protein 2’ on known strains of MRSA as well as other organisms identified from chromogenic agar plates. A total of 3050 patients with unknown MRSA status were processed through the routine laboratory during the investigation period and 73 of these were presumptive positive following overnight incubation. Of 70 patients who could be evaluated, 32 (43.8%) specimens would be suitable for use with the kit directly from overnight incubation on chromogenic agar, and the other 38 (52.1%) would be suitable following four hours’ incubation on blood agar. The cost of one positive MRSA test with the inclusion of this test is e15.15 compared with published reports of e35.00 for a commercial polymerase chain reaction (PCR) test. This protocol would allow the reporting of presumptive positive MRSA results approximately 24 hours earlier than currently achieved.

Predominance and Persistence of a Single Clone of Listeria ivanovii in a Manchego Cheese Factory Over 6 Months

In an attempt to study the diversity and persistence of molecular subtypes of pathogenic Listeria spp. in a cheese factory at the La Mancha region of Spain, 43 samples were taken from incoming raw milk (cow's, ewe's, goat's and mixed species) and from certain food-contact and environmental surfaces before and/or after sanitation. Of these samples, 12 contained pathogenic Listeria. From the chromogenic agar plates corresponding to those, 46 phosphatidylinositol-specific phospholipase C-positive isolates were randomly taken for further analysis, including biochemical tests and pulsed-field gel electrophoresis (PFGE). They coincided in identifying all the 46 as Listeria ivanovii subsp. ivanovii, apparently a single PFGE type. Both ewe's and goat's raw milk batches from asymptomatic animals tested along the 6-month period persistently carried the same strain, which was also obtained from inner surfaces of raw milk truck tanks and the milk dump tank at the cheese factory. Biofilm-forming abilities of this L. ivanovii clone and interference against L. monocytogenes Scott A reference strain were tested, but failed to account for the clone's apparent pervasive presence.

When are the hands of healthcare workers positive for meticillin-resistant Staphylococcus aureus?

Hand hygiene is a key component in reducing infection. There are few reports on the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) on healthcare workers' (HCWs') hands. The aim of this study was to establish whether HCWs' fingertips were contaminated with MRSA in a clinical hospital setting. The study was conducted in an acute tertiary referral hospital on four MRSA wards that were part of a larger research study on MRSA epidemiology and four other wards not included in the study. The fingertips from all categories of 523 HCWs were sampled on 822 occasions by the imprinting of fingertips on MRSA chromogenic agar plates. The type of hand hygiene agent used, if any, and the immediate prior activity of the HCW were recorded. Overall, 38/822 (5%) fingertips from 523 HCWs were MRSA-positive; 12/194 (6%) after clinical contact, 10/138 (10%) after contact with the patient's environment and 15/346 (4%) after no specific contact. MRSA was recovered on 2/61 (3%) occasions after use of alcohol hand rub, 2/35 (6%) after 4% chlorhexidine detergent, 7/210 (3%) hand washing with soap and water, and 27/493 (5%) when no hand hygiene had been performed. MRSA was recovered from HCWs on seven of the eight wards. MRSA was more frequently present on fingertips on the four non-study wards vs the four MRSA study wards [18/250 (7%), 3/201 (1%), respectively; P<or=0.004]. The isolation of MRSA from HCWs' fingertips, including after hand hygiene, indicates that more educational programmes are necessary to improve the quality of hand hygiene to prevent transmission of MRSA.

Comparison of three chromogenic media and enrichment broth media for the detection of methicillin-resistant Staphylococcus aureus from mucocutaneous screening specimens

This study compares the performance of three chromogenic culture agar plates, chromID MRSA, MRSA-Screen and MRSA-Select, by challenging with a collection of Staphylococcus aureus strains and screening samples obtained from hospitalised patients. All chromogenic media showed excellent sensitivity (>95%) and specificity after 18 h on the methicillin-resistant Staphylococcus aureus (MRSA) collection strains, but the specificity of MRSA-Screen decreased markedly after 42 h. Sixty-eight of 1,002 screening specimens yielded MRSA on at least one medium. The sensitivity of all media to detecting MRSA after 18 h was <50%, but this increased to 75% (chromID MRSA), 81% (MRSA-Screen) and 72% (MRSA-Select) after 42 h and 85% after enrichment and plating on the same media. The specificity at 18 h was excellent, but was significantly lower for MRSA-Screen after 42 h and enrichment. In conclusion, all media showed equivalent sensitivities after 18 h of incubation and performed better when enriched before inoculation. MRSA-Screen was more sensitive but less specific than the two other media after 42 h of incubation.

Validation of NMKL method No. 136 — Listeria monocytogenes, detection and enumeration in foods and feed

A collaborative study was organised to define the performance characteristics of the revised NMKL Method No.136 “ Listeria monocytogenes. Detection and enumeration in foods”. Chromogenic L. monocytogenes specific plating medium, Agar Listeria according to Ottaviani and Agosti (ALOA) was introduced in the revised method in order to improve the sensitivity and specificity of the method, and to shorten the analysis time. Efficacy of ALOA One Day from AES (ready-to-use agar in bottles), Listeria Chromogenic Agar (Agosti and Ottaviani Listeria agar) from Lab M (LCA) (dehydrated powder), Chromogenic Listeria Agar Plates from Oxoid (OCLA) (ready-to-use plates) and L. monocytogenes blood agar medium LMBA from Lab M (dehydrated powder) were tested . Three types of food matrices (vacuum-packed hot-smoked salmon, soft cheese and cooked ham) and one feed matrix (wheat grain) inoculated with two levels of L. monocytogenes with or without L. innocua were used in the study. A total of 24 samples were analysed both in the detection and enumeration part of the study by 18 and 17 Nordic laboratories, respectively. The sensitivities of ALOA, LCA, OCLA and LMBA in the detection of L. monocytogenes in food samples after one-step enrichment (Half-Fraser) were 94.4–96.4% and after two-step enrichment (Half-Fraser followed by Fraser) 97.7–100%. For wheat grain the respective figures were 84.7–88.9% and 90.3–93.1%, respectively. The precision characteristics were generally good for the enumeration of L. monocytogenes in the food samples with high levels of inoculation. Several poor values obtained from the food samples with low levels of inoculation probably reflect high uncertainty of measurement when less than 10 cfu/g was counted. Poor values obtained from the wheat grain samples by any of the media evaluated were due to poor precision for feed samples. According to the study, the revised NMKL Method No.136, 4th ed. showed excellent results in the detection and satisfactory results in the enumeration of L. monocytogenes in foods. The results for the detection of L.monocytogenes in wheat grain were good, but the method cannot be recommended for the enumeration of L. monocytogenes in feed-stuffs. Any one of the media evaluated can interchangeably be used as an obligatory isolation medium for the detection and enumeration of L. monocytogenes in foods, and for the detection in feed-stuffs. The L. monocytogenes specific plating media that were evaluated shorten the time of analysis and significantly reduce the work load. The detection of positive samples mostly after Half-Fraser enrichment, reduces the analysis time further, and makes it possible to skip the secondary enrichment. However, secondary enrichment cannot be totally left out, because samples with low levels of L. monocytogenes, with high levels of competing flora, and with injured L. monocytogenes, do need secondary enrichment.

Urinary Tract Infection-A Survey of Local Population

Urinary Tract Infection, commonly known as UTI, affects as many as 50% women at least once during their lifetime. All individuals are susceptible to Urinary Tract Infection (UTI); however the prevalence of infection differs with age, sex and certain predisposing factors. With the above background in mind we conducted a survey of the local population (women of 3 age groups) to compare the urinary tract microbial community of control individuals with the UTI positive patients. Attempts were made to identify pathogens through Serum Bactericidal Antibody Response. 200 urine samples collected from control as well as UTI patients were randomly inoculated in parallel on four varieties of chromogenic agar plates and the Colony Forming Units (CFU) per milliliters (ml) of each microbe was determined. The serum bactericidal antibody assay was performed to demonstrate the presence of serum antibodies with bactericidal activity against the bacterium found in urine. However, with further experimental analysis, this bactericidal activity was found to be non specific and a similar percentage of bacteriolysis was observed incase of the control population also. 104-105 CFU mL-1 was the demarcating value between normal and pathological samples in asymptomatic cases. A significant variation was also noted in the microbial profile of various age groups. E. coli is the most prevalent pathogen in the post menopausal group. 15 different bacterial isolates were obtained of which the 16S rDNA sequence of the 6 novel ones are available in GenBank. The control and patient population showed a clear cut variation in the percentage of urinary tract microbes.