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Biomedical subjects

D H Gröschel

Publications and source records attributed to D H Gröschel.

At least 19 recordsLinked to original sources
PubMed1996

Effectiveness of contact isolation during a hospital outbreak of methicillin-resistant Staphylococcus aureus.

Contact isolation has been recommended by the Centers for Disease Control and Prevention for the prevention of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA), but there are few data which prospectively quantitate the effectiveness of contact isolation for this purpose. During an outbreak of MRSA in a neonatal intensive care unit between July 18, 1991 and January 30, 1992, weekly surveillance cultures were performed on all patients. Sixteen of 331 admissions became colonized with MRSA, and 3 (19%) developed infections: bacteremia, conjunctivitis, and dialysis catheter site infection. The isolates from all 16 patients were submitted to plasmid profile analysis and restriction enzyme analysis of whole cell DNA. All of the patients had identical chromosomal patterns and plasmid profiles, which differed from control isolates from other wards, indicating that the outbreak resulted from spread of a unique strain. None of 144 personnel who were cultured after recent contact with newly colonized patients during the outbreak were found to carry MRSA, which suggests that patients were the reservoir for transmission rather than caregivers. The most probable source for each individual transmission was determined based on proximity in time and space and shared exposure to caregivers. The rate of transmission of MRSA from patients on contact isolation was significantly lower (0.009 transmissions per day on isolation) than the rate for patients not on isolation (0.140 transmissions per day unisolated, relative risk = 15.6, 95% confidence interval 5.3-45.6, p < 0.0001). The authors conclude that the risk of nosocomial transmission of MRSA was reduced 16-fold by contact isolation during the outbreak in this neonatal intensive care unit. These data confirm the results of previous studies which have suggested that contact isolation was effective in controlling the epidemic spread of methicillin-resistant Staphylococcus aureus.

Contact Tracing↗
PubMed1996

Clostridium difficile infection.

The spore-forming anaerobe Clostridium difficile has become a serious enteropathogen. Changes in the composition of natural intestinal flora, mainly due to antibiotic therapy, permit its colonization of, and multiplication in, the colon. The disease is caused by (entero)toxin A and (cyto)toxin B, and infection ranges from asymptomatic carrier state and mild diarrhea to pseudomembranous colitis. The clinical diagnosis is made by observing inflammatory, sometimes bloody, diarrhea and by the colonoscopic detection of epithelial necrosis, ulceration, and, in the advanced state, pseudomembrane formation. The laboratory supports the diagnosis by detecting toxin A and/or B by an enzyme-linked immunoassay with high specificity, but sometimes less sensitivity than with the cytotoxin assay in tissue culture cells. Fecal leukocytes or fecal lactoferrin may be found. Culture for the isolation and identification of toxigenic C. difficile is time consuming but necessary for epidemiological studies. Polymerase chain reaction (PCR) tests have been tested for detection of the toxin B gene directly in stool. Therapy consists of stopping all systemic antibiotic treatment and the use of oral metronidazole or vancomycin. There may be more relapses after vancomycin therapy, and the increasing vancomycin resistance of Enterococcus is worrisome. Prevention, especially of nosocomial spread, requires isolation and enforced handwashing. For epidemiological studies, the bacteria can be typed by molecular DNA analyses, including PCR, protein electrophoresis, and immunological tests.

Antitrichomonal Agents↗
PubMed1993

Adenovirus type 8 epidemic keratoconjunctivitis in an eye clinic: risk factors and control.

Epidemic keratoconjunctivitis (EKC) due to adenovirus type 8 affected 126 (7%) of 1870 ophthalmology clinic patients during an outbreak. Risk factors and mode of transmission were studied by comparing cases (n = 58) and controls (n = 200) for exposure to risk factors. Pneumotonometry (odds ratio [OR], 10.5; 95% confidence interval [CI], 4.0-27.7), multiple clinic visits (OR, 5.9; 95% CI, 3.3-10.6), and contact with an infected physician (OR, 3.3; 95% CI, 1.2-9.0) were significant risk factors for infection. The hands of 3 patients and 3 physicians with EKC were cultured before and after hand washing to assess adenovirus removal; 3 had hand cultures positive for adenovirus after hand washing. In conclusion, this outbreak appeared to be due to inadequate disinfection of instruments, especially pneumotonometers, and finger-to-eye transmission by health care workers. Hand washing did not reliably remove adenovirus from contaminated fingers. Gloving for exam of eyes with EKC may help prevent transmission. Ophthalmologists with EKC were a significant risk factor for patients and should be furloughed for the duration of communicability.

Adenovirus Infections, Human↗
PubMed1991

Disinfectant testing in the USA.

The federally mandated registration of disinfectants with the United States Environmental Protection Agency (EPA) requires the submission of efficacy test data obtained with the accepted methods of the Association of Official Analytical Chemists (AOAC). These include qualitative suspension tests for bacteria and fungi and carrier tests with use-dilutions for bactericidal, mycobactericidal and sporicidal activity. There is no AOAC method for virucides, and the present methods set forth by the American Society for Testing and Materials (ASTM) and the EPA are under scrutiny by the scientific community. The AOAC use-dilution test was challenged by the users, and two collaborative studies by the EPA and the AOAC did not resolve all questions. A new, quantitative supension test was proposed. The AOAC mycobactericial carrier test was found to be deficient for testing glutaraldehydes; an updated version and a new quantitative suspension test have been accepted by the EPA for registration. As a result, different glutaraldehyde preparations carry different label claims which are confusing to the consumer. National and international standardization of testing is desirable.

Chemistry Techniques, Analytical↗
PubMed1991

Immunoblot studies to analyze antibody to the Rickettsia typhi group antigen in sera from patients with acute febrile cerebrovasculitis.

In 1986, an unusual syndrome of acute febrile cerebrovasculitis in the Piedmont Region of Virginia was reported. All patients had encephalopathy and prior exposure to both a sylvan environment and flea-infested animals. The initial serological studies suggested a rickettsial origin, corroborating clinical, epidemiological, and histopathological findings. Sera from four of five patients were subsequently studied by immunoblotting. Unabsorbed and absorbed sera were tested with electrophoresed and electroblotted Rickettsia typhi, Legionella bozemanii, and Proteus vulgaris OX19 antigens. The unabsorbed sera reacted with all three antigens. The P. vulgaris- and L. bozemanii-absorbed sera reacted with R. typhi only and without significantly less intensity. In contrast, the reactivity of R. typhi-absorbed sera was significantly lower with all three antigens. These results indicate that these patients had specific antibodies to a typhus group antigen. Although our findings suggest that a rickettsia of the typhus group may have caused this syndrome, no definitive diagnosis could be achieved because a rickettsial organism was not isolated.

Acute Disease↗
PubMed1989

Nosocomial Legionella micdadei pneumonia: 10 years experience and a case-control study.

Sixteen patients with nosocomial Legionella micdadei pneumonia, diagnosed between 1977 and 1988, were studied retrospectively to define clinical and epidemiological characteristics of the disease. Also, a case-control study was performed comparing the five patients with L. micdadei pneumonia during a cluster of cases in 1982, with uninfected patients with the same underlying diagnoses. No significant differences were noted in the case-control study with regard to age, presence of leucopenia, intensity or duration of immunosuppressive therapy, bed location, duration of hospital stay, frequency of transplant rejection or overall mortality. Legionella micdadei isolates from a sink on the renal transport ward, from hot water storage tanks, and one clinical isolate had identical cellular fatty acid composition. Extensive sampling of other potential sources failed to yield the organism. This indirect evidence suggests potable water as the source of infection.

Cross Infection↗
PubMed1989

The inanimate environment of an intensive care unit as a potential source of nosocomial bacteria: evidence for long survival of Acinetobacter calcoaceticus.

Environmental surface and personnel hand impression cultures were obtained during 13 sampling periods in the University of Virginia Pediatric Intensive Care Unit to document potential reservoirs of nosocomial pathogens. In 78 environmental cultures Staphylococcus aureus was found eight times and gram-negative bacilli ten times. The patient chart cover was the most commonly contaminated surface. Acinetobacter calcoaceticus was found in five of ten cultures positive for gram-negative bacilli. Thirty of 59 hand cultures were positive for S aureus and gram-negative bacilli; nurses and residents had both, respiratory therapists only gram-negative bacilli, and A calcoaceticus was the most commonly isolated bacterium of potentially nosocomial significance (14/30). Laboratory investigation of bacterial survival revealed that gram-negative bacilli survived on a dry formica surface from a few hours up to three days but Acinetobacter survived up to 13 days. Since A calcoaceticus has been implicated in many nosocomial infections, its long survival on a dry surface may be an additional factor in its transmission in hospitals and suggests that more attention be paid to environmental surfaces as a source of significant nosocomial pathogens.

Acinetobacter↗
PubMed1989

[The effect of thiocyanate on bacterial plasmids using the plasmid screening test].

A plasmid screening test (alkaline lysis and agarose gel electrophoresis) was used to assess the effect of thiocyanate on the plasmid replication on two bacterial strains with plasmids of different size, Klebsiella pneumoniae and Acinetobacter calcoaceticus. At concentrations physiologic for mammals (5-50 mg SCN-/l) no effect on the replication of extrachromosomal DNA was noted. This reaffirms the concept that a physiologic anion may be responsible for biological regulatory processes but will not affect the synthesis of extrachromosomal DNA when applied in vitro in physiologic concentrations.

Acinetobacter↗
PubMed1989

[Antisepsis and disinfection: the necessity of a conceptual demarcation].

Increasing international cooperation in the areas of research, teaching, trade and healthcare has called for standardization of the terminology. In disinfection and antisepsis such efforts have been pursued for almost 20 years but without great success. This contribution to the definition of antisepsis and its clear separation from disinfection is supposed to promote international discussion. German terms for skin, mucosa and wound antisepsis are proposed which permit to restrict the term disinfection to the application of antimicrobial measures to inanimate objects and surfaces.

Antisepsis↗
PubMed1988

Comparison of the lysis centrifugation and radiometric blood culture systems for recovery of yeast.

The performance of the Isolator (lysis centrifugation) and Bactec (radiometric) detection systems for the recovery of fungi from blood was studied prospectively by comparison of 2,188 paired cultures obtained at two geographically separated teaching hospitals. Eight-three yeast isolates were recovered from 78 (3.6%) cultures that were obtained from 43 patients. Seventy-three (88%) yeast strains were recovered using the Isolator system, and 60 (72%) were recovered in the Bactec system. The average time for recovery of yeast was 2.3 days for the Isolator system and 3.1 days for the Bactec system. Optimal recovery can be accomplished through the use of both systems.

Blood↗
PubMed1987

Comparison of radioactive (32P and 35S) and biotinylated probes for detection of cytomegalovirus DNA.

Cytomegalovirus (CMV) DNA was detected in a dot-blot assay by hybridization to a DNA probe labeled with radioisotopes (32P or 35S) or biotin. Limits of detection were established for both the radioisotopically labeled DNA probes as well as the biotin-labeled probe. Hybridization of the radioisotopically labeled probes was detected by autoradiography and liquid scintillation while the biotin-labeled probe was detected after coupling to one of three enzymes (e.g., horseradish peroxidase, alkaline phosphatase, or acid phosphatase). In addition, several different substrates were evaluated with the nonisotopic detection enzymes. Detection limits (and times for detection) were 1 pg (4 h) for 32P, approximately 1 pg (96 h) for 35S, 5 pg (1-3 h) for the phosphatases, and 25-50 pg for peroxidase. Thus, 32P-labeled probes appear to provide the best sensitivity whereas the avidin-linked phosphatases provide the best sensitivity among the nonisotopic detection systems.

Autoradiography↗
PubMed1986

Evaluation of a radiometric method for pyrazinamide susceptibility testing of Mycobacterium tuberculosis.

Pyrazinamide susceptibility testing of Mycobacterium tuberculosis requires an acid environment. By controlling the method of acidification and the quality and quantity of the inoculum, the test can be performed with the BACTEC radiometric system (Johnston Laboratories, Towson, Md.). We acidified BACTEC 7H12 medium with buffered phosphoric acid and adjusted the test inoculum to 1/10 of that usually employed in BACTEC protocols; after 5 days of growth we correctly identified 36 of 36 strains susceptible to 50 micrograms of pyrazinamide per ml. All 18 resistant strains were classified as pyrazinamide resistant. (Susceptibility or resistance had been determined by standard plate assays.) The test was able to detect small resistant populations in artificial mixtures of 1 or 2% resistant bacteria with a susceptible strain (10 mixtures each). We tested 70 M. tuberculosis strains in acidified BACTEC 7H12 medium and by the plate dilution test at pH 5.5. All strains grew in the BACTEC medium, but three strains failed to grow on plates and were not tested further; the results of both methods agreed for the remaining strains.

Culture Media↗
PubMed1986

Analysis of epidemiologic markers of nosocomial Serratia marcescens isolates with special reference to the Grimont biotyping system.

Seventy-one strains of Serratia marcescens obtained from hospitalized patients of the Instituto Nacional de la Nutricion in Mexico City and two Virginia hospitals (University of Virginia Medical Center and Norfolk General Hospital) were analyzed to find markers useful for the epidemiologic investigation of outbreaks with this organism. Biotyping with commercial microwell systems (API 20# system [Analytab Products, Plainview, N.Y.] and DMS Rapid NFT [DMS Laboratories, Inc., Flemington, N.J.]) was not useful. Biotyping with the system designed by Grimont (assimilation tests, pigment production, and the ability to reduce tetrathionate broth) was helpful to characterize all strains. Of the 37 Mexican strains, 36 belonged to biogroup A 5/8 and 32 were biotype A8b. The 34 strains from the Virginia hospitals were distributed among six different biogroups and 12 biotypes. Significant differences in antimicrobial susceptibility (50% MIC, microgram/ml) between Mexican and Virginia strains were seen with carbenicillin (256 versus 8), piperacillin (64 versus 4), amikacin (16 versus 2), gentamicin (2 versus 0.5), and tobramycin (16 versus 2). Some Mexican strains showed variability in the susceptibility to amikacin because they were low producers of 6'-N-acetyltransferase type I. The Mexican strains seemed to come from a hospital with cross-infection problems because most were isolated from urine, were multiresistant, and more nonpigmented; in contrast, the strains isolated at University of Virginia Medical Center represent the experience of a hospital with scattered S. marcescens infections. The Grimont biotyping scheme is a useful epidemiologic tool for the clinical microbiologist.

Aminoglycosides↗