Resistance to antiretroviral drugs in patients with primary HIV-1 infection. Investigators of the Quebec Primary Infection Study

The widespread use of antiretroviral agents (ARVs) and the growing occurrence of HIV strains resistant to these drugs have given rise to serious concerns regarding the transmission of resistant viruses to newly infected persons. Plasma viral RNA from 80 individuals newly infected between 1997 and 1999 was genotyped by automated sequencing to analyze the profile of viruses resistant to nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs and NNRTIs) and to protease inhibitors (PIs). The prevalence of mutations that conferred primary resistance to PIs (L10I, D30Y, V82A, L90M) was 15% of the cohort. RT genotypic variants, associated with high-level resistance to ARVs, were observed in 21% of individuals, including NRTI, NNRTI and multidrug (MDR) resistance in 6, 5, and 10% of cases, respectively. The phenotypic susceptibility of viral isolates to ARVs was also assayed and showed transmission of high-level resistance to ZDV, 3TC, and PIs in those individuals with MDR. The transmission of drug-resistant HIV genotypic variants is a serious problem that merits further attention by public health officials, virologists, and clinicians.

Development of mupirocin resistance among methicillin-resistant Staphylococcus aureus after widespread use of nasal mupirocin ointment

All methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from colonized or infected patients in a 625-bed public teaching hospital during an epidemic, and for 3 years thereafter, underwent susceptibility testing to mupirocin. Mupirocin resistance among MRSA increased markedly over this period (1990, 2.7%; 1991, 8.0%; 1992, 61.5%; 1993, 65%) in association with increased use of mupirocin ointment as an adjunct to infection control measures.

Growth inhibition of Mycobacterium tuberculosis by polyoxyethylene stearate present in the BACTEC pyrazinamide susceptibility test

We have previously found that approximately 3.5% of 428 clinical isolates of Mycobacterium tuberculosis yield uninterpretable results in the BACTEC pyrazinamide (PZA) susceptibility test system, because of inadequate growth. We tested the hypothesis that polyoxyethylene stearate (POES), the ingredient of the reconstituting fluid for the test, was the cause of this growth inhibition. A total of 15 isolates known for their previously uninterpretable results and 100 randomly chosen clinical isolates were tested in parallel both with and without POES. Repeat testing of the isolates with previously uninterpretable results yielded results in the presence of POES in only seven (47%). In the absence of POES, all gave interpretable results but one such result showed false resistance. For the other 100 clinical isolates, interpretable results were obtained with and without POES, but growth was enhanced in the absence of POES, especially in the PZA-susceptible strains. This was evidenced by a decreased time to attain a growth index of 200 in the control vial (4.9 days without POES versus 5.8 days with POES; P < 0.001) and a higher mean growth index ratio on the day of interpretation of the test (7.4% without POES versus 2.2% with POES; P < 0.001). However, the enhanced growth without POES led to 20 susceptible strains being misinterpreted as either resistant or borderline. We suggest that isolates of M. tuberculosis which yield uninterpretable results in the BACTEC PZA test system should be retested both with and without POES. If interpretable results indicating PZA resistance are obtained only in the absence of POES, the result should be confirmed by a pyrazinamidase assay or by the conventional proportion method. Routine omission of POES from the BACTEC test for all clinical strains is discouraged because of the unacceptably high false-resistance rates.

Testing of susceptibility of Mycobacterium tuberculosis to pyrazinamide: comparison of Bactec method with pyrazinamidase assay

The susceptibility of 428 clinical isolates of Mycobacterium tuberculosis to pyrazinamide was assessed by the Bactec method and the Wayne pyrazinamidase assay. The correlation between the two tests was 98.2 and 100% for susceptible and resistant strains, respectively. False resistance was seen in four (0.8%) strains with the Bactec test, and false-susceptible results occurred in two (0.5%) pyrazinamidase assays. The Bactec test is rapid and reliable, and the Bactec results correlate well with the pyrazinamidase test results, although some strains did not grow well in the test medium.

Pneumococcal resistance to antimicrobial agents in the province of Québec, Canada

The serogroup/serotypes (SGTs) and antimicrobial susceptibilities to 10 antimicrobial agents of 110 clinical strains of Streptococcus pneumoniae were determined. Strains intermediately resistant or highly resistant to penicillin G (80 of 110) belonged predominantly to SGTs 23 (45.0%), 19 (13.7%), 6 (10.0%), 9 (6.2%), and 14 (3.7%). The MICs of all cephalosporins, tetracycline, trimethoprim-sulfamethoxazole, and chloramphenicol increased along with the MICs of penicillin G. However, erythromycin resistance and clindamycin resistance were observed more frequently among the intermediately penicillin-resistant strains. Multiple resistance was observed for 32 strains, of which 25 were highly resistant to penicillin G and belong to SGT 23F. All strains were susceptible to vancomycin.

Growth curves of Staphylococcus aureus, Candida albicans, and Moraxella osloensis in propofol and other media

Propofol, 2,6 diisopropylphenol, in an emulsion formulation (Diprivan), has been associated with postsurgical infections caused by Staphylococcus aureus, Moraxella osloensis and Candida albicans. These organisms were individually inoculated into each of the following media: (1) the emulsion preparation of propofol, (2) Intralipid 10%, (3) pure 2,6 diisopropylphenol, and (4) trypticase soy broth (TSB). The organisms were incubated and subcultured hourly for eight hours at room temperature. Propofol supported the growth of all three organisms, but for S. aureus and M. osloenis, the growth rate was slower in propofol than in TSB (P less than 0.05). There was no difference between the growth rate of any organism in propofol than in Intralipid 10%. The authors conclude that propofol, in the emulsion formulation, supports bacterial growth and, therefore, must be prepared for administration in an aseptic manner. Also, by administering propofol soon after preparation, the risk of introduction of a significant inoculum to the patient will be reduced.

Ability of National Committee for Clinical Laboratory Standards-recommended quality control strains from the American Type Culture Collection to detect errors in disk diffusion susceptibility tests

The National Committee for Clinical Laboratory Standards (NCCLS) recommends, as a quality control for the disk diffusion susceptibility test, the use of three strains from the American Type Culture Collection: Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922. This study assesses the capacity of these strains to detect errors in the overall method. ATCC strains were tested by comparing testing by the standard NCCLS-recommended procedure (ST) with testing under the following conditions: incubation at 25 degrees C, Mueller-Hinton agar depths of 2 mm (AD2) and 8 mm (AD8), agar pHs of 6.5 and 8, inocula with McFarland standards of 0.25 (0.25M) and 4.0 McFarland (4.0M), direct inoculation without preincubation of inoculum (DI), and a 2-h delay between inoculation and disk application (2HR). The frequency of zone measurements outside the NCCLS-recommended control zone limits were as follows: ST, 0%; AD2, 18%; AD8, 9.6%; pH 6.5, 7.9%; pH 8, 5.3%; 0.25M, 3.5%; 4.0M, 24%; DI, 3.4%; 2HR, 1.8%; 25 degrees C (only E. coli and P. aeruginosa were evaluable), 28%. These results suggest that the quality control strains are only partially effective in detecting single extreme laboratory errors and that careful laboratory supervision is necessary even in the setting of properly monitored quality control strains.

Strategies for the prevention of neonatal infection with herpes simplex virus: a decision analysis

Decision analysis was used in the evaluation of nine strategies for the prevention of neonatal infection with herpes simplex virus (HSV). These strategies involve physical examination at labor, weekly screening of pregnant women for shedding of HSV, use of serologic methods specific for HSV type 2, and performance of a rapid diagnostic test at labor. Rates of cesarean delivery and of neonatal infection with HSV were estimated for each strategy, and the estimates were compared with those for a strategy of no intervention. The effects of variations in the sensitivities and specificities of the diagnostic and serologic tests used were analyzed. Given the currently available data and technology, physical examination at labor is the optimal strategy if the primary goal is to minimize the ratio of excess cesarean sections to cases of neonatal HSV infection averted.

Zirconium compound-induced pulmonary fibrosis

Despite suspicion that inhalation of zirconium should be capable of causing human pulmonary disease, documentation of zirconium pneumoconiosis in humans has been lacking. We studied a likely case of zirconium compound-induced pulmonary fibrosis. The diagnosis was based on the following: (1) a history of gradual increase in symptoms and slowly progressing pulmonary fibrosis by chest roentgenogram compatible with a pneumoconiosis; (2) an appropriate history of exposure and a latency period of about 15 years before the onset of dyspnea and of roentgenographic changes; (3) analysis of open lung biopsy material revealing end-stage fibrosis and honeycombing, a moderate number of birefringent particles, and extremely high levels of a variety of zirconium compounds; and (4) no other potential cause of fibrosis. We conclude that zirconium should be considered a likely cause of pneumoconiosis and that appropriate precautions should be taken in the workplace.

Streptococcus pneumoniae acute suppurative parotitis in a patient with Sjögren's syndrome

A case of suppurative parotitis due to Streptococcus pneumoniae is reported in a patient with Sjögren's syndrome. The rarity of this condition is noted by a review of the literature.

Replacement of special enzyme immunoassay transport medium by a standard viral transport medium in the Herpcheck herpes simplex virus antigen detection test

A new direct herpes simplex virus antigen enzyme immunoassay (EIA) uses a special EIA transport medium (ETM) for transport of herpes simplex virus (HSV) specimens. As ETM lyses the virus precluding culture and typing, we evaluated the relative performance of this EIA when performed on specimens transported in either ETM or a standard viral transport medium (VTM). These EIA results were also compared to cell culture performed on specimens transported in VTM (VTM-CC) and direct rapid inoculation into cell culture (CC). Based on all confirmed positives, by any test, the sensitivities for CC was 97% (66/68), for VTM-CC 91% (62/68), for ETM-EIA 97% (66/68), and for VTM-EIA 93% (63/68). It appears that VTM may be a slightly less desirable substitute than ETM in the performance of EIA. However, VTM-EIA is certainly as sensitive as cell culture performed on VTM.

Natural killer cell function in patients with acquired immunodeficiency syndrome and related diseases

This review describes current knowledge of changes in natural killer (NK) cell function in acquired immunodeficiency syndrome (AIDS)-related disorders, vis-à-vis associated abnormalities in NK cytolytic function, NK cell subset distribution, NK cytopathology, and lymphokine regulation. NK cells, which are closely associated with large granular lymphocytes, are spontaneously cytotoxic to tumor and virally infected targets. As such, they may play a role in natural resistance to human immunodeficiency virus type 1 (HIV-1)-associated disorders and other opportunistic infections. Yet, peripheral blood NK activity is frequently reduced in patients with HIV-1-induced disease. NK cells are heterogeneous both with respect to their expression of serologically defined membrane antigens and functional activity. In AIDS-related syndromes, there appears to be a diminution of the NK pool (CD16+ cells) involved in cytolytic function, while there is an elevation of the NK pool that coexpresses NK (Leu 7+) and T (CD8+) cell markers, which show little or no involvement in cytolytic function. The impairment of in vitro NK function is not associated with a reduced frequency of lytic conjugates of effectors and target cells nor with the recycling capacity of these effector cells but rather is associated with defects in the NK cell lytic machinery following formation of such conjugates. NK cells in AIDS patients show an impairment in effector cell microtubule rearrangement following target cell interaction. The causes of NK cell dysfunction in AIDS-related disorders remain unknown. NK cells do not appear to express the CD4 epitope of the HIV receptor, nor have they been demonstrated to be susceptible to infection by HIV-1. There appears to be a preponderance of immature NK cells and a lymphokine imbalance in patients with HIV-1 associated disease. Interleukin-2 can partially restore diminished in vitro NK function. Elucidation of the involvement of the NK compartment in natural resistance to HIV-1 merits further investigation.

Diagnosis of herpes simplex virus infection in a clinical setting by a direct antigen detection enzyme immunoassay kit

A commercial 4-h direct herpes simplex virus (HSV) antigen detection enzyme immunoassay (EIA) kit (Du Pont Herpchek) was evaluated by using 273 clinical specimens obtained in a hospital-based infectious disease practice. The EIA was compared with a standard culture method in which WI38 cells were inoculated within 20 min of sample collection. Cultures were observed for 2 weeks, and positive findings were confirmed by fluorescein-labeled monoclonal antibody (FA) staining. The values for the overall HSV detection rate were 40.7% by the standard culture method and 41.4% by EIA. In eight cases, the EIA was positive, while the culture method was negative; however, clinical data and confirmatory blocking EIA suggested that a true HSV infection was present. For six FA-confirmed, culture-positive samples, the direct EIA was negative; however, an EIA performed on the supernatants of these cultures was positive, suggesting that the failure of the EIA to detect these samples was not due to lack of strain specificity of the test. After confirmatory tests of standard culture and EIA discrepant results, the overall sensitivity of the test was 95.0% (113 of 119) and the specificity was 100% (154 of 154).

The effect of cyclosporine A on infection of susceptible cells by human immunodeficiency virus type 1

The effect of cyclosporine A (CyA) on the ability of the human immunodeficiency virus type 1 (HIV-1) to infect the H-9 T-cell leukemic line, as well as interleukin-2 (IL-2)-grown human peripheral blood-derived lymphocytes, has been studied. Pretreatment of H-9 cells and human lymphocytes with CyA over 24 hours completely prevented viral infection over a 21-day period, whereas the addition of drug at two hours postinfection with HIV-1 had a significant inhibitory effect on viral replication and expression of the virus-specific antigens p17 and p24. However, if CyA was added at later times to these lymphocytic cells, this inhibitory effect was lost. Indeed, the removal of CyA from cultures that had been treated from two hours after infection led to the rapid production of progeny virus. HIV-1 was able to infect peripheral blood lymphocytes obtained from each of four kidney allograft recipients on long-term CyA antirejection therapy, as long as drug was not included in the culture medium. In addition, we asked what effect pretreatment with CyA of cells of the U-937 monocytic line and primary cultures of human monocytes/macrophages might have on infection by HIV-1. CyA had no demonstrable effect on the ability of HIV-1 to infect cells of either type.

'Toxic strep syndrome'. A manifestation of group A streptococcal infection

Three patients presented with multisystem disease that shared many of the features of toxic shock syndrome. Bacteriologic and serologic evidence strongly suggested that group A beta-hemolytic Streptococcus had caused the illnesses. Group A streptococcal infection may be an underdiagnosed cause of a toxic streptococcal syndrome, a syndrome of multisystem disease apparently mediated by toxins.

Susceptibility testing with the sensititer breakpoint broth microdilution system

The antimicrobial susceptibility profiles of a total of 318 aerobic and facultatively anaerobic bacteria (255 gram-negative bacilli and 63 gram-positive cocci) were determined, using a new commercially available breakpoint broth microdilution procedure (Sensititer Breakpoint System (SBS), Gibco Diagnostics, Inc., Madison, WI) that categorizes test results in the form of susceptibility categories: susceptible, intermediate, and resistant. Results obtained with the SBS were compared with those achieved with a standardized disk diffusion procedure. Among a total of 4,414 organism-antimicrobic comparisons, concordance between the results of the SBS and the disk diffusion procedure was observed in 3,888 cases (88.1%). Four hundred twenty-three (9.6%) minor discrepancies, 45 (1.0%) major discrepancies, and 58 (1.3%) very major discrepancies were noted. Arbitration of major and very major discrepancies with a full-range minimum inhibitory concentration (MIC) procedure confirmed the results of the SBS in 53.4% of cases. A single organism-antimicrobial combination, the nonenterococcal streptococci tested against the aminoglycosides, yielded a significant number of very major errors which were arbitrated in favor of the disk diffusion result. These errors were probably due to poor growth of the test organism in the broth medium used for performing the SBS test (i.e., cation-supplemented Mueller-Hinton broth). With this exception, the SBS was found to be at least as accurate as the standardized disk diffusion procedure.