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M J Alfa

Publications and source records attributed to M J Alfa.

At least 19 recordsLinked to original sources
PubMed1999

E test versus agar dilution for antimicrobial susceptibility testing of viridans group streptococci.

Viridans group streptococci (VGS) are commonly isolated from the blood of hospitalized patients. The E test represents a convenient method for determining the MICs for VGS, but for this purpose it has not been well validated against reference methods. In this study, 180 unselected VGS isolates were identified to a species level, and the MICs of penicillin, cefuroxime, cefotaxime, and vancomycin were determined by both agar dilution and the E test. Available data regarding demographic and laboratory variables for each VGS bacteremic episode were collected, the significance of each VGS isolate was assessed, and the associations between and among laboratory and clinical variables were investigated. Among all VGS isolates, 68.3% (median of three runs) were found to be fully susceptible to penicillin by agar dilution. The E test and agar dilution showed average agreements (within +/-1 dilution) of 92.2% for penicillin, 95.7% for cefuroxime 91.3% for cefotaxime, and 86.7% for vancomycin. Agreements over serial E tests and serial agar dilutions were excellent for beta-lactam agents (intraclass correlation coefficients, >0.9) but less impressive for vancomycin. Very major error rates for the E test were </=0.7%, and combined major and minor error rates were within acceptable limits for all antimicrobial agents tested. Lysis-centrifugation culture methods were more often associated with clinically insignificant VGS isolates; otherwise, no associations between clinical and laboratory variables were noted.

Anti-Bacterial Agents↗
PubMed1998

Comparison of liquid chemical sterilization with peracetic acid and ethylene oxide sterilization for long narrow lumens.

The aim of this study was to determine how well peracetic acid liquid chemical sterilization (LCPAS) killed test organisms in the presence of 10% fetal bovine serum and 0.65% salt challenge (RPMI-S) compared with a 100% ethylene oxide (ETO) sterilizer and an ETO hydrochlorofluorocarbon (ETO-HCFC) sterilization method with long (125 cm), narrow (3-mm internal diameter) flexible lumens as the test carrier. The inoculated lumens were dried overnight before processing. The test organisms included Mycobacterium chelonei, Enterococcus faecalis, and Bacillus subtilis. For all 3 organisms tested, the LCPAS process resulted in a 6 log10 reduction in bacterial load compared with a 2.5 log10 to 6 log10 reduction for the 100% ETO and ETO-HCFC sterilizers. Sterilization was achieved for 100%, 61%, and 67% of the lumen test carriers for the LCPAS, 100% ETO, and ETO-HCFC sterilizers, respectively. The data indicate that of the sterilization methods evaluated, LCPAS was the most effective for sterilizing narrow flexible lumens in the presence of residual inorganic and organic soil. This effectiveness was achieved through a combination of organism wash-off and peracetic acid sterilant killing of organisms. Salt was the major compounding factor for effective ETO gas sterilization, because carriers inoculated with organisms in 10% fetal bovine serum alone all were sterilized by both 100% ETO and ETO-HCFC sterilization methods. Our data support the critical need to ensure adequate precleaning of narrow flexible lumen endoscopes before any sterilization method.

Bacillus subtilis↗
PubMed1998

Survey of incidence of Clostridium difficile infection in Canadian hospitals and diagnostic approaches.

A questionnaire relating to Clostridium difficile disease incidence and diagnostic practices was sent to 380 Canadian hospitals (all with > 50 beds). The national questionnaire response rate was 63%. In-house testing was performed in 17.6, 61.5, and 74.2% of the hospitals with < 300, 300 to 500, and > 500 beds, respectively. The average test positivity rates were 17.2, 15.3, and 13.2% for hospitals with < 300, 300 to 500, and > 500 beds, respectively. The average disease incidences were 23.5, 30.8, and 40.3 cases per 100,000 patient days in the hospitals with < 300, 300 to 500, and > 500 beds, respectively. In the 81 hospitals where in-house testing was performed, cytotoxin testing utilizing tissue culture was most common (44.4%), followed by enzyme-linked immunosorbent assay (38.3%), culture for toxigenic C. difficile (32.1%), and latex agglutination (13.6%). The clinical criteria for C. difficile testing were variable, with 85% of hospitals indicating that a test was done automatically if ordered by a doctor. Our results show that C. difficile-associated diarrhea is a major problem in hospitals with > or = 200 beds. Despite a lower disease incidence in smaller hospitals, there was a higher diagnostic test positivity rate. This may reflect the preference of smaller hospitals for culture and latex agglutination tests.

Bacterial Proteins↗
PubMed1997

Attachment of Haemophilus ducreyi to human foreskin fibroblasts involves LOS and fibronectin.

Haemophilus ducreyi is the causative agent of the genital ulcer disease Chancroid. Chancroid has been shown to increase the risk of heterosexual transmission of HIV. Little is known regarding the attachment or localization of this organism to human cells in either the dermal or epidermal layer. In this study the attachment of H. ducreyi to human foreskin fibroblast (HFF) cells was further characterized. Attachment was mediated by more than one mechanism. Proteinase K treatment but not trypsinization of H. ducreyi significantly reduced attachment suggesting protein involvement. In addition, purified lipooligosaccharide (LOS) was able to inhibit attachment in a dose dependent manner. It appeared that the organism binds to fibronectin in the extracellular matrix of HFF cells, since competition studies using fibronectin showed that it was able to significantly reduce attachment in a dose dependent manner whereas collagen did not. We hypothesize that the attachment of H. ducreyi involves both a protein mediator of attachment (likely pili) as well as LOS and that one or both of these bacterial components interacts with fibronectin in the extracellular matrix to mediate attachment to HFF cells.

Antibodies, Monoclonal↗
PubMed1997

Bacterial killing ability of 10% ethylene oxide plus 90% hydrochlorofluorocarbon sterilizing gas.

OBJECTIVES: To use a serum and salt challenge in narrow-lumen carriers to evaluate a 10% ethylene oxide plus 90% hydrochlorofluorocarbon (EO-HCFC) sterilant mixture in a retrofitted 12/88 sterilizer as an alternative to the banned chlorofluorocarbon-ethylene oxide (EO) sterilant mixture. DESIGN: An EO-HCFC sterilizing gas mixture in a retrofitted 12/88 sterilizer was compared to 100% ethylene oxide (100% EO) sterilizing gas to determine its relative ability to kill seven different bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis spores, Bacillus stearothermophilus spores, Bacillus circulans spores, and Mycobacterium chelonei) in the presence or absence of a combined 10% serum and 0.65% salt challenge using both penicylinders (PC) and long narrow-lumen (LU) carriers. RESULTS: The EO-HCFC sterilant mixture (96% sterile carriers) was equivalent to the 100% EO sterilant (98% sterile carriers) for killing vegetative organisms, as well as spore suspensions, on the 27 PC and 27 LU carriers in the absence of serum and salt. In the presence of serum and salt, the EO-HCFC sterilant mixture was markedly better than the 100% EO sterilant at reducing the bacterial load on the 63 PC carriers (95% vs 62% sterile PC carriers, respectively), whereas both sterilizers were equivalent for the 63 LU carriers (49% vs 40% sterile LU carriers, respectively). Of the seven test organisms, E faecalis, B subtilis, B stearothermophilus, and B circulans were the most difficult to kill for both PC and LU carriers when serum and salt were present. CONCLUSIONS: The data presented in this report indicate that the EO-HCFC sterilant mixture is an effective alternative for gas sterilization. Indeed, the efficiency of bacterial killing for the EO-HCFC sterilant mixture was similar to that achieved by the 12/88 EO-CFC sterilant mixture.

Bacteria↗
PubMed1997

Improved detection of bacterial growth in continuous ambulatory peritoneal dialysis effluent by use of BacT/Alert FAN bottles.

Culture-negative peritonitis is a major complication for patients on continuous ambulatory peritoneal dialysis (CAPD) and precludes organism-specific therapy. The aim of the present study was to compare inoculation of 10 ml of CAPD effluent into BacT/Alert blood culture bottles (FAN [fastidious antimicrobic neutralizing], BacTAlert aerobic [BTA], and BacT/Alert anaerobic [BTAn] bottles) to our conventional method of using 50 ml of concentrated CAPD effluent to inoculate peptone broth bottles (BD bottles) and MacConkey agar and blood agar medium (BA-MAC). The FAN, BTA, and BTAn bottles were monitored automatically in the BacT/Alert blood culture instrument. A total of 207 CAPD effluents were studied, and in 97 bacteria were detected by at least one method. Compared to BTA bottles (79 of 97; 81.4%), BTAn bottles (78 of 97; 80.4%), and BD bottles (88 of 97; 90.7%), the single best broth medium for detecting bacterial growth in CAPD effluents was the FAN bottle (90 of 97 effluents; 92.8%). A total of 125 bacterial species were detected by any method, and the majority (91.8%) of CAPD effluents were infected with a single species. A combination of FAN and BTAn bottles detected 111 of 125 (88.8%) of all organisms, whereas a combination of BD bottles and BA-MAC detected 107 of 125 (85.6%) of all organisms. One or more organisms that would have been completely missed by the conventional method with BD bottles and BA-MAC were detected in 18 CAPD effluents. Of these 18 CAPD effluents, 6 showed no growth by the conventional method with BD bottles and BA-MAC. On the basis of our data, the most sensitive and least labor intensive method was direct inoculation of 10 ml of CAPD effluent into a FAN bottle and a BTAn bottle, which could be automatically monitored by the BacT/Alert blood culture instrument. On the basis of case definitions for peritonitis, the sensitivities and specificities of the methods with FAN and BTAn bottles and with BD bottles and BA-MAC were 81.1 and 98.8% and 74.5 and 96.5%, respectively.

Bacteria↗
PubMed1996

Comparison of ion plasma, vaporized hydrogen peroxide, and 100% ethylene oxide sterilizers to the 12/88 ethylene oxide gas sterilizer.

OBJECTIVE: The performance of a standard gas sterilizer, which uses a mixture of 12% ethylene oxide (EtO) and 88% chlorofluorocarbon as the sterilizing gas (12/88), was compared to selected gas, ion plasma, and vaporized hydrogen peroxide (H2O2) sterilizers that do not use chlorofluorocarbons. The effect of serum and salt on sterilizer performance was evaluated. DESIGN: Test carriers (porcelain and stainless steel penicylinders, or 125-cm lengths of plastic tubing [internal diameter of 3.2 mm]) were inoculated with Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Mycobacterium chelonei, Bacillus stearothermophilus spores, Bacillus subtilis spores, and Bacillus circulans spores and then subjected to sterilization using 12/88, 100% EtO, ion plasma, or vaporized H2O2. The bacterial inoculum was prepared with and without 10% serum and 0.65% salt, and the residual bacterial load after sterilization as determined using viable counts. RESULTS: All of the sterilizers tested effected a six-log10 reduction of the bacterial inoculum on penicylinders, unless 10% serum and 0.65% salt were present, in which case the 100% EtO, vaporized H2O2, and ion plasma sterilizers were not as effective as the 12/88 sterilizer. None of the sterilizers could eradicate 10(6) CFU of all of the bacteria in 10% serum and 0.65% salt when inoculated inside a narrow lumen. CONCLUSIONS: The margin of safety for the 100% EtO, vaporized H2O2, and ion plasma sterilizers is less than that of the 12/88 sterilizer. The inability of all sterilizers, including the 12/88, to kill organisms in narrow lumens reliably when serum and salt were present raises concern about the current practice of gas sterilization of flexible endoscopes.

Analysis of Variance↗
PubMed1995

Mycobacterium abscessus infection of a Norplant contraceptive implant site.

The authors report a case of Mycobacterium abscessus infection of a subdermal levonogestrel implant (Norplant) site. The infection lasted 12 weeks and was indolent, skin manifestations were low grade and difficult to detect. Culture of exudate samples showed that M. abscessus was the only causative agent. After the implant was removed the patient's arm healed uneventfully without antimycobacterial therapy. The authors recommend that if Gram staining of apparently infected material from an implant site does not reveal a causative organism, then cultures should be done for mycobacteria and fungi. Kinyoun staining for acid-fast bacteria and calcoflour-white staining for fungi should also be performed. The implant should be removed and the patient given antimicrobial therapy as indicated. The authors emphasize the need to be aware of the potential for M. abscessus infection of implant sites and stress that appropriate microbiologic culture procedures are essential for accurate diagnosis.

Adult↗
PubMed1995

Transmission of Ureaplasma urealyticum from mothers to full and preterm infants.

This study assessed maternal genital colonization and subsequent neonatal transmission rate of Ureaplasma urealyticum in pregnant women in an average socioeconomic population. In addition very low birth weight infants were assessed to determine whether the presence of U. urealyticum correlated with increased risk of developing respiratory problems. The study group consisted of 108 sequential full term mothers and 104 preterm mothers delivering in a tertiary care hospital in central Canada. The genital carriage rates (assessed using placental sampling) of ureaplasmas in term and preterm mothers were 25.9 and 19.2%, respectively (P = 0.3185). Acquisition of ureaplasmas in the neonatal respiratory tract of neonates occurred significantly (P = 0.0182) more often in preterm neonates (11 of 130; 8.5%) than in term neonates (2 of 110; 0.9%). Very low birth weight (VLBW) infants (< or = 1500 g) were at greater risk (P = 0.042) of acquiring ureaplasmas in their respiratory tracts (5 of 26; 19%) than larger preterm neonates (6 of 104; 5.8%). All VLBW infants with respiratory colonization by ureaplasmas (5 of 5) developed bronchopulmonary dysplasia compared with 33% (7 of 21) of VLBW neonates without ureaplasmas (P = 0.028). This difference in bronchopulmonary dysplasia development among VLBW infants was independent of further stratification by birth weight. These VLBW neonates with ureaplasmas also stayed significantly (P = 0.037) longer in the neonatal intensive care unit (43.6 +/- 10.4 days) than did other preterm neonates (22.1 +/- 20.8 days). Our results demonstrate that VLBW preterm neonates have increased risk of acquiring U. urealyticum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Use of tissue culture and animal models to identify virulence-associated traits of Haemophilus ducreyi.

To identify virulence-associated properties of Haemophilus ducreyi, 34 strains of this sexually transmitted pathogen were evaluated for in vitro phenotypic characteristics of potential relevance to chancroid pathogenesis and for their ability to produce lesions in the temperature-dependent animal model for chancroid. Of the 34 strains tested, all but three produced a cytopathic effect on human foreskin fibroblasts (HFF) and all but six strains formed large microcolonies on HFF monolayers. A subset of 12 selected strains underwent more extensive analyses and, when evaluated for both their cytadherence kinetics and growth in the presence of HFF monolayers, it was found that several of these strains had a very limited ability to attach to HFF cells. When the same 12 strains were tested in the temperature-dependent rabbit model, only the seven strains which were positive in all of these in vitro-based tests readily produced lesions. In contrast, the five strains that were noted to be deficient in one or more of the phenotypic characteristics scored in the in vitro systems did not produce lesions. This association between the traits measured in vitro and the ability to produce dermal lesions was significant (P = 0.0012). These results suggest that in vitro behavior may be used to predict the virulence potential of H. ducreyi strains. Moreover, the phenotypic characteristics described in this study are appropriate focal points for efforts to determine the molecular basis of the virulence of this pathogen.

Animals↗
PubMed1994

A quantitative chemiluminescent ribosomal probe method for monitoring adherence of Haemophilus ducreyi to eukaryotic cells.

This study evaluated a commercially available chemiluminescent-labelled, ribosomal RNA-directed DNA probe (CRP) as a method to quantitate attachment of H. ducreyi to human foreskin fibroblast (HFF) cells. Evaluation of four strains of H. ducreyi demonstrated that the CRP assay was unaffected by eukaryotic cells and its advantages were: (i) quantitation was done after attachment so it did not interfere with the attachment process, and (ii) it was a rapid, reliable method for quantitating bound bacteria, despite bacterial clumping. Gentamicin-killed H. ducreyi attached to both HFF cells and viable controls, suggesting that the adhesins are components constitutively present on the surface of H. ducreyi. This method may be widely applicable, since the probe recognizes most prokaryotic rRNA sequences.

Bacterial Adhesion↗
PubMed1994

In-hospital evaluation of orthophthalaldehyde as a high level disinfectant for flexible endoscopes.

One hundred endoscopes used for bronchoscopy (30), gastroscopy (35) or colonoscopy (35) were studied to determine the efficiency of a new high level disinfectant, orthophthalaldehyde (OPA). Manual cleaning was the method studied since this would be the least effective and thereby provide the greatest challenge to the 0.5% (w/v) OPA solution. The OPA was convenient and easy to use since it did not have irritating vapours and as it is used directly, does not require dilution. Our study demonstrated that the OPA was stable for up to 14 days despite repeated re-use. The cleaning/disinfection procedure could achieve a > or = 5 LOG10 reduction in bacterial load. This in-hospital evaluation supports the conclusion that OPA is an effective choice as a high level disinfectant for flexible endoscopes.

Bronchoscopes↗
PubMed1994

Methicillin-resistant Staphylococcus aureus. Optimization of the agar screen plate method.

Swab inoculation of oxacillin agar screen plates was compared with drop inoculation for detection of methicillin-resistant Staphylococcus aureus. The poor sensitivity of the swab method (59%) was related to heteroresistance of the S. aureus isolates. We recommend the drop method (100% sensitivity) because interpretation of results was significantly easier, making it more reliable.

Methicillin Resistance↗
PubMed1993

Humoral immune response of humans to lipooligosaccharide and outer membrane proteins of Haemophilus ducreyi.

The humoral immune response to purified lipooligosaccharide (LOS) and outer membrane proteins (OMP) of Haemophilus ducreyi was evaluated. Sera from chancroid-endemic (Uganda, Kenya) and -nonendemic (Canada) countries were tested by an ELISA. The response to OMPs was cross-reactive with other Haemophilus species, and elevated levels of antibody were detected in patients that did not have chancroid. The LOS component stimulated an H. ducreyi-specific immune response that was detected only in patients with chancroid. The sensitivity of the LOS ELISA was 96% (95% confidence interval, 89.9%-100%) and the specificity was 97% (95% confidence interval, 95.8%-98.2%). Thus, the anti-H. ducreyi LOS immune response is a significant diagnostic and epidemiologic indicator.

Adolescent↗
PubMed1993

Haemophilus ducreyi adheres to but does not invade cultured human foreskin cells.

Haemophilus ducreyi is the etiologic agent of the localized genital ulcer disease known as chancroid. The pathogenesis of this organism is poorly understood. The role of attachment in the disease process has not been evaluated. In this study, 125I-H. ducreyi was used to quantitatively evaluate the interaction of virulent and avirulent H. ducreyi strains with human foreskin cells. Using this in vitro model system, we demonstrated that, at 22 and 35 degrees C, the attachment of virulent H. ducreyi 35000 to human foreskin cells was significantly more marked than that of avirulent H. ducreyi A77. Although H. ducreyi penetrated between human foreskin cells, internalization was not a major component. Our competition assay data suggest that the attachment mechanism of H. ducreyi may be similar to that of Neisseria gonorrhoeae. We speculate that the attachment and microcolony formation of virulent H. ducreyi may provide a mechanism for bacterial localization and evasion of host defenses.

Bacterial Adhesion↗