Is the sutureless cataract incision a valve for bacterial inoculation?

Many cataract surgeons perform sutureless surgery to decrease operating time, postoperative astigmatism, and healing time. Anecdotal case reports of postoperative endophthalmitis after sutureless surgery prompted our investigation of this type of wound closure and its possible relationship to an increased incidence of infection. This in vitro study addressed the question: Is sutureless more likely than sutured cataract surgery to provide a route for inoculation of microbial organisms into the eye? Twenty-eight human eyes obtained postmortem were randomly divided into 14 pairs and successively incubated for 90, 150, 210, and 270 minutes each in a suspension of Staphylococcus epidermidis in physiologic media. Cultured aqueous aspirates yielded no significant differences between sutured and unsutured eyes in colony counts at any time interval. This suggests that both sutured and unsutured wounds resist bacterial ingrowth equally and that a properly constructed unsutured wound is not a significant valve for bacterial inoculation in an eye pressurized to physiological conditions.

Detection of cytomegalovirus in shell vial cultures by using a DNA probe and early nuclear antigen monoclonal antibody.

An in situ biotinylated DNA probe assay was evaluated as an adjunct to anti-cytomegalovirus early nuclear antigen indirect immunofluorescence and cytopathic effect on cytomegalovirus-infected monolayers in shell vial cultures. Viral infection was detected by early nuclear antigen indirect immunofluorescence at 24 h and by DNA probe assay and shell vial cytopathic effect at 5 days.

Evaluation of the syphilis Bio-EnzaBead assay for detection of treponemal antibody.

An enzyme-linked immunosorbent assay for Treponema pallidum antibody (Syphilis Bio-EnzaBead Kit; Organon Teknika Corp., formerly Litton Bionetics, Kensington, Md.) was compared with the standard fluorescent treponemal antibody absorption test for syphilis (indirect fluorescent-antibody confirmatory test; Zeus Scientific Inc., Raritan, N.J.). Six hundred specimens tested in the rapid plasma Reagin card test (Hynson, Westcott and Dunning, Inc., Baltimore, Md.) and microhemagglutination assay for antibodies to T. pallidum (Ames Division, Miles Laboratories, Inc., Elkhart, Ind.) were used for comparison testing. One hundred and sixty-two specimens were from either persons with syphilis or persons whose history was unknown but who showed reactive serology, whereas 438 were from persons without syphilis. The reactivity of each serum by the Bio-EnzaBead test was determined visually and from optical density readings. Excellent reproducibility of visual readings was obtained; all results were within +/- 1 gradation of the expected readings in all 60 coded sera tested. Overall agreement between the Bio-EnzaBead and fluorescent treponemal antibody absorption test results was 96.3% when read visually and greater than or equal to 95.7% when using optical density readings. Our data indicate that Bio-EnzaBead results read at 405 nm and determined by using the mean antigen optical density reading of the nonreactive control plus 0.025 as the cutoff value provide an overall sensitivity and specificity of 93.0 and 98.6%, respectively, along with the best agreement with the fluorescent treponemal antibody absorption assay. Ease of performance and objectivity also contribute toward the acceptability of this assay as an alternative confirmatory test for syphilis.

Identification of gram-negative bacilli using the Autobac IDX.

The Autobac IDX is a new system for the rapid identification of clinically significant members of the Enterobacteriaceae and Aeromonas, Acinetobacter, Alcaligenes, Flavobacterium, Moraxella, and Pseudomonas species. The use of 18 differentially inhibitory compounds such as dyes and antibiotics along with a computerized algorithm based on a multivariate analysis provides the basis for the identification of 30 different groups of gram-negative bacilli. Required preliminary tests include observations on the presence or absence of swarming on a sheep blood agar plate and noting the following: growth, lactose fermentation, and bile precipitation from a MacConkey plate. Spot indole and spot oxidase tests must be performed as well. Identification by the Autobac IDX System takes 3-6 hr after completion of the preliminary tests. From a total of 403 isolates tested, the Autobac system agreed with the MicroID AND N/F systems on 382 identifications (94.8%). Four isolates, two Acinetobacter anitratus, one Serratia marcescens and one Moraxella osloensis could not be identified by IDX. Additional testing was required on 35 (8.7%) of the isolates.

Viruses and human cancer.

The cause of human cancer is probably multifactorial and the role of viruses is unclear. The study of retroviruses has led to the identification of oncogenes responsible for transformation and tumor induction. Human viruses associated with malignancies include the JC virus (associated with progressive multifocal leukoencephalopathy) and some adenoviruses. No human malignancies have been associated with the latter group. A number of herpes viruses of lower animals have been associated with malignancies and herpes simplex virus type 2 has been associated with carcinoma of the cervix and vulva. The Epstein-Barr virus has been associated with Burkitt's lymphoma and nasopharyngeal carcinoma. Some circumstantial evidence suggests that cytomegalovirus may be associated with Kaposi's sarcoma among homosexuals. The hepatitis B virus (HBV) has been associated with hepatocellular carcinoma. The fullfillment of Koch's postulates presents ethical problems regarding man and proving the viral etiology of human malignancy. Social experiments may elucidate some of these questions. An increase in venereal herpes should be associated with an increase in carcinoma of the cervix and use of the HBV vaccine in populations with high incidences of HBV carrier states should decrease the incidence of hepatocellular carcinoma. The investigation of the retroviruses though not establishing viruses as causing human malignancies at least will improve our understanding of the malignant process.

Acridine orange staining and radiometric detection of microorganisms in blood cultures.

To determine whether acridine orange (AO) staining of blood cultures could be used as a substitute for blind subculture when used in conjunction with the BACTEC system (Johnston Laboratories, Inc., Towson, Md.), the two methods were compared on all BACTEC-negative specimens. Since blind subcultures were routinely performed in our laboratory on days 2 and 6 of incubation, AO staining was also performed on these days. Cultures which were BACTEC positive on day 1 of incubation were not included in the study. Of the 2,395 bottles tested after 2 days of incubation, 106 were subculture positive. Of these, 96 (90.6%) were also AO positive and BACTEC positive, 3 (2.8%) were AO positive and BACTEC negative, and 7 (6.6%) were AO negative and BACTEC positive. Of the 3,487 bottles tested on day 6 of incubation, 14 were subculture positive; 7 (50%) of these were AO positive and BACTEC positive, and seven were AO positive and BACTEC negative. Of the total of 10 culture-positive bottles missed by BACTEC, all were positive, and all 10 companion aerobic bottles were BACTEC positive. In both phases of the experiment, there was a total of only four false-positive AO stains. As a result of this investigation, we have substituted AO staining for blind subculturing of BACTEC-negative bottles.

Group B streptococcal infection in the neonate.

The incidence of disease caused by the Group B streptococci (GBS) has risen significantly in the past two to three decades and the GBS are now a leading cause of meningitis in the neonate. The GBS are sub-classified into five groups (Ia, Ib, Ic, II, and III) with type III being the most common, especially in meningitis. The two syndromes, early (first week) and the late (second to twentieth week) are associated with a 50 percent and 20 percent mortality, respectively. The acute syndrome is usually a result of infection from a maternal source whereas the late syndrome is more often associated with nosocomial or community acquisition of GBS. Antibiotic prophylaxis by treating infants at risk or colonized mothers has not proven efficacious; however, maternal antibodies have been shown to afford protection to neonates. Further evaluation of antibiotic prophylaxis and therapy, clarification of the mechanism of acquired immunity versus susceptibility and further characterization of the antigens of GBS with a possibility of a vaccine as a measure of prophylaxis are currently in progress.

Evaluation of a bioassay method for serum amikacin concentrations.

The bioassay system from American Diagnostic for amikacin was compared to the same company's radioimmunoassay (RIA) technique used in this hospital. The bioassay is performed by adding serum from a patient to wells cut in agar which have been seeded with a susceptible fast growing microorganism (Enterobacter). After incubation of five hours at 37 degrees, the zones of inhibition for four standards are measured and plotted. The amount of amikacin in the serum sample is then determined from the linear graph. Ten replicates of a serum with 8 microgram per ml of amikacin and 10 replicates of a serum with 20 microgram per ml of amikacin were assayed on each of four days. Aliquots of the same samples were assayed in a similar manner by RIA. The coefficients of variation (CVs) of the within run assays by the bioassay and RIA methods for the low amikacin test sample ranged from 4.7 to 7.2 percent and 6.2 to 13.0 percent, respectively. The within run CVs for the high amikacin test sample for the bioassay and RIA methods ranged from 5.2 to 6.9 percent and 5.0 to 13.9 percent, respectively. The day to day and overall CVs for the bioassay and RIA methods for the low amikacin test sample were 1.5 and 5.8 percent and 7.4 and 11.8 percent, respectively. For the high amikacin test sample, they were 0.4 and 6.0 percent and 4.0 and 9.6 percent, respectively. The correlation coefficient for 49 sera from patients on amikacin was 94 percent between the two methods.

Evaluation of an automated, computerized system (automicrobic system) for Enterobacteriaceae identification.

The automated and computerized AutoMicrobic system (AMS; Vitek Systems, Inc., subsidiary of McDonnell Douglas, Hazelwood, Mo.) was evaluated as a means of identifying the Enterobacteriaceae. The Micro-ID system (General Diagnostics, Morris Plains, N.J.) and, when necessary, conventional tubed media were used for comparison. Identification by AMS and Micro-ID differed in only 12 of 1,528 isolates (0.8%). Disagreements occurred primarily with Enterobacter spp. Precision testing of the AMS showed only 1 of 72 tests (1.4%) deviating from the expected. The AMS was found to be an accurate and precise method for the identification of Enterobacteriaceae.

A comparison of four commercial systems for the identification of nonfermentative gram-negative bacilli.

Four commercial systems for the identification of glucose nonfermentative, gram-negative bacilli and the conventional system used in our laboratory were compared. The API 20E, Roche Oxi/Ferm Tube, BBL Minitek, Flow N/F System, and our system were compared for accuracy, time needed for identification and number of isolates needing additional testing. A total of 241 different isolates were used. The API 20E identified 86.7% correctly; Oxi/FermTube, 83.0%; Minitek, 93.4%; N/F System, 90.5%; and our system, 90.0%. Within 24 hours after isolation, the API 20E identified 25.7%; Oxi/Ferm Tube and Minitek, 0%; N/F System 27.3%; and our system, 35.7%. After 48 hours, the API 20E identified 74.7%; Oxi/Ferm Tube, 35.7%; Minitek, 45.2%; N/F System, 83.0%; and our system, 94.6%. The number of isolates that required additional testing for identification by the API 20E was 119; Oxi/Ferm Tube, 161; Minitek, 88; N/F System, 43; and our system, 36. Ease of performance, technologist time, and level of identification required by individual laboratories are discussed.

Evaluation of the Bactec serum gentamicin assay.

A radiometric assay for gentamicin was compared with an established radioimmunoassay protocol. The coefficients of variation for within-run, day-to-day, and overall runs were consistently higher for the radiometric method as compared with the radioimmunoassay. The coefficient of correlation for 84 patient sera tested by the two methods for gentamicin levels was 0.82. Though less precise, the radiometric method was felt to be an acceptable means of determining gentamicin levels in laboratories where the radioimmunoassay is unavailable.

MIF-like activity in non-stimulated and virus infected cell cultures.

Macrophage-migration inhibition factor (MIF) is a lymphocyte-derived substance which plays an important role in cell mediated immunity. Soluble factors containing MIF-like activity and produced by non-stimulated and virus-infected non-lymphoid cell cultures have also been reported. In the present study, a MIF-like factor was repeatedly detected in Buffalo green monkey kidney cells infected with mumps and herpes simplex virus type 1 (HSV-1) indicating that this substance is reproducible and can be stimulated by two viruses of widely varying groups. Wistar-38 (WI-38) cell cultures also increased production of this substance in response to mumps but not HSV-1 infection, indicating that the production of this factor is not necessarily induced by all viruses. A factor which stimulated the spread of macrophages was also found to be induced in WI-38 cells by both viruses, suggesting yet another substance produced by non-lymphoid cells in response to viral infection. The ability of non-stimulated WI-38 cells to produce MIF-like activity was also confirmed, and this factor could be further stimulated or opposed by viral infection.

An identification scheme for gram-negative nonfermentative bacilli.

A series of six flow charts have been developed to identify the Gram-negative nonfermentative bacilli most commonly isolated from clinical specimens. Colonial morphology and oxidase reactivity determine the pathway to be followed on the flow chart which then indicates the specific test to be performed. Most isolates can be identified within 24 hours using 3 to 5 tests. Each pathway was selected on the basis of 94-100 per cent confidence limits otherwise an alternate pathway is shown. Results of 2,788 nonfermenters identified by this scheme are discussed.

Immunologic parameters in Down's syndrome.

Down's syndrome children are known to have increased susceptibility to respiratory infections. Quantitative or qualitative differences in the various components of the immune system could account for increased susceptibility to infection involving the upper respiratory tract. In an effort to establish certain normal values and to determine if humoral immune abnormalities are associated with the chromosomal anomalies of Down's syndrome, immunoglobulin levels, certain complement component levels, viral antibodies, hepatitis B surface antigen and milk precipitins from a population of inpatients and outpatients were compared with those of age, sex and race matched control populations. It does not appear that the upper respiratory infections are associated with abnormally low levels of immunoglobulins or complement, with the possible exception of IgM. Both the inpatient and outpatient Down's syndrome populations had decreased levels of IgM, indicating a possible relationship with the syndrome itself. In addition, the symptomatology does not seem to be due to IgE mediated atopic sensitivity. Hepatitis B surface antigen was found only in institutionalized Down's syndrome patients, but it did not seem to be related to the other immune components studied.

Evaluation of the acid-fast smear.

A retrospective analysis of the data involving all specimens submitted to the mycobacteriology laboratory over the past 20 months supports the continued use of the acid-fast smear as an aid in the detection of tuberculosis.