Evaluation and diagnosis of acute infectious diarrhea.

The appropriate approach to the diagnosis and management of acute infectious diarrhea is determined by the frequency and setting of the illness, the recognizable causes or syndromes, the cost and yield of available diagnostic tests, and the treatability of the disease. Acute diarrhea affects everyone throughout the world from one to more than six times each year, depending on age, location, and living conditions. The range of identifiable viral, bacterial, and parasitic etiologies is great, and the cost of indiscriminate use of etiologic studies for diagnosis is prohibitive. Because of its insensitivity for many organisms and poor selection of cases for testing, routine stool culture has been one of the most costly and ineffective microbiologic tests; the cost per positive result has traditionally exceeded $900 to $1,000. The appropriate treatment for the vast majority of cases (independent of their cause) is simple and effective: oral glucose- and electrolyte-containing rehydration solution. On the basis of an appropriate history and understanding of pathogenesis, fecal specimens can be selectively obtained and promptly examined for leukocytes and parasites, and the common noninflammatory diarrheas can be separated from the inflammatory infections in order to focus further studies on the latter group. The bacteria for which specific antimicrobial therapy should be considered usually cause inflammatory diarrhea in the United States. Therefore, only when the history or fecal leukocyte findings indicates an inflammatory process is it appropriate to culture for the routine invasive bacterial pathogens. In sporadic inflammatory diarrhea, culture methods should include those for Campylobacter jejuni as well as Salmonella and Shigella. Several special circumstances may prompt a consideration of parasites (including Giardia, Entamoeba, Strongyloides, Cryptosporidium), Vibrio, Yersinia, Clostridium difficile, enterotoxigenic Escherichia coli, food-borne agents, or sexually transmitted pathogens. The practical value of specific identification of rotaviruses (by enzyme-linked immunosorbent assay, Rotazyme, or electron microscopy) is primarily epidemiologic, particularly in hospitalized infants or young children. Using such a selective approach to fecal culture will greatly increase its yield and can reduce the cost per positive result from $1,000 to less than $150.

Pneumonia treated with imipenem/cilastatin.

In an open, prospective, multicenter trial the efficacy and tolerance of imipenem/cilastatin for the treatment of bacterial pneumonia was investigated. Forty-three adults were studied: 29 with nosocomial and 14 with community-acquired infections. Significant underlying disease was present in 91 percent of patients. Nosocomial infection was frequently associated with endotracheal intubation (48 percent), prior antibiotic therapy (48 percent), and recent surgery (31 percent). Most frequent sputum isolates included Pseudomonas aeruginosa (10, all nosocomial), Hemophilus influenzae (10), Escherichia coli (eight), Staphylococcus aureus (seven), and Streptococcus pneumoniae (six). Treatment with imipenem/cilastatin was associated with clinical cure in 93 percent of patients. Two of three failures and one superinfection occurred in association with isolates of Pseudomonas aeruginosa resistant to imipenem. Overall, six of 10 strains of Pseudomonas aeruginosa isolated prior to therapy developed resistance to imipenem after an average of 10 days of therapy. Adverse effects occurred in nine patients (21 percent) and included one case of pseudomembranous colitis. Monotherapy with imipenem/cilastatin of serious lower respiratory tract infections was relatively safe and highly effective with the exception of disease associated with P. aeruginosa.

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.

Leukocyte esterase activity and nitrite test as a rapid screen for significant bacteriuria.

The results of a simple, inexpensive reagent strip test for the detection of leukocyte esterase and nitrite in 252 urine specimens were compared with semiquantitative urine cultures. Negative reagent strip results predicted correctly all urine culture results with less than 10(5) CFU/mL. Screening of urine specimens with the Chemstrip L/N could aid in reducing the cost of laboratory testing.

Bacterial colonization and phlebitis-associated risk with transparent polyurethane film for peripheral intravenous site dressings.

Previous studies of various brands of polyurethane dressings have noted differences in the rates of catheter colonization. We compared Bioclusive transparent polyurethane (TP) dressing with a cotton gauze (CG) dressing on peripheral intravenous (IV) access sites for the incidence of phlebitis, catheter tip colonization, skin colonization, and catheter-related bacteremia. The study, involving 598 ward patients, was case controlled, prospective, and randomized for a period of 4 months. Each patient was entered into the study only once, and all dressings were applied by a member of the IV therapy team. No significant difference was seen for phlebitis rate (TP: 9.8% vs. CG: 7.6%) or catheter tip colonization, defined as greater than 15 colony forming units (CFU) (5.7% vs. 4.4%) by a semiquantitative technique. Cultures of specimens from the skin and catheter tips of the majority of patients (91%) showed no growth. An association was found between those patients with greater than 15 CFU isolated from catheter tips and those with phlebitis (p = 0.022). No documented catheter-related bacteremia occurred in either study group.

Air sampling in hospitals.

Air sampling in hospitals is performed for the epidemiologic investigation of nosocomial infections, for the elucidation of spread and control of airborn microorganisms, for assessing biohazards associated with instruments, equipment and procedures and for controlling the performance of devices and techniques used for the reduction of airborne contaminants. Many different air-sampling devices are available but only a few have found use in hospitals. Certain samplers are used for special studies such as the Andersen stacked-sieve impactor or the liquid impingers. Lately, samplers have been developed which due to their size and weight are more useful to the hospital microbiologist and epidemiologist than the older slit samplers. the Ross Microban sieve sampler and the Biotest Reuter Centrifugal Sampler were tested in comparison with the Casella slit sampler and found to show comparable results. The hand-held, battery-operated Biotest RCS sample is the most versatile for general sampling of hospital air.

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.

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.

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.

In-use testing of four glutaraldehyde disinfectants in the Cidematic washer.

Four glutaraldehyde disinfectants (Cidex, Glutarex, Sonacide, and Sporicidin) were tested in routine use in the Cidematic washer to identify the most economic, effective disinfectant among them. An in vitro killing test with Pseudomonas aeruginosa (10-min exposure) and Mycobacterium smegmatis (20-min exposure) was used. All four disinfectants were effective prior to first use. In the use tests, Cidex killed both organisms for its claimed effectiveness period of 2 weeks. Glutarex was effective against Pseudomonas for its claimed effectiveness period of 4 weeks but was effective against Mycobacterium only 3 weeks. Sonacide, claimed to be effective for 4 weeks, killed Pseudomonas for 2 weeks but was ineffective against Mycobacterium after 1 week. Sporicidin (1:15 dilution), claimed to be effective for 30 days, did not kill either test organism after 5 days. Glutarex used for a 3-week period was found to be the most economic, effective substitute for Cidex in the Cidematic machine.

Is there a need for state health department sanitary codes for public hydrotherapy and swimming pools?

The Board of Health of the Commonwealth of Virginia has an outdated sanitary code for its public hydrotherapy and swimming pools. The code is restricted to pools in hotels and other lodging places. The absence of modern regulations for public hydrotherapy and swimming pools has permitted serious deficiencies in pool maintenance, which are highlighted in this report. The most notable of these deficiencies was the presence of high levels of bacterial contamination that could predispose to infect in the water of one public hot tub. The results of this study indicate that the Virginia Board of Health sanitary code for pool water must be revised immediately and should include all public hydrotherapy and swimming pools. Other states and communities may want to assess their codes for swimming pools and hydrotherapy tubs to avoid deficiencies that could be detrimental to public health.

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.

Evaluation of the BACTEC radiometric method for detection of 1% resistant populations of Mycobacterium tuberculosis.

BACTEC and conventional methods of antimicrobial susceptibility testing were compared with the use of artificial mixtures of 1% resistant and 99% susceptible Mycobacterium tuberculosis strains. Inocula for the assays were prepared on the basis of radiometric readings. A total of 40 resistant strains were tested: 18 were resistant to isoniazid, 16 to rifampin, 5 to streptomycin, and 1 to ethambutol. The BACTEC method detected 27 of 39 strains at the greater than 0.5% resistance level, whereas the conventional plate method detected only 8 of 40. In addition, the results of the BACTEC assay were closer to the expected 1% resistance level (0.7%) than were the data obtained with the proportional plate method (0.3%; P = 0.001). This difference was most striking with the isoniazid-resistant strains. The precision of the assay methods was quite different (coefficients of variation, 26% for BACTEC and 54% for plates; P = 0.0002). Streptomycin-resistant strains had the highest variability in both assay methods. A 1-day delay in calculating the BACTEC data after the control vial reading was equal to or greater than 30 resulted in a 25% reduction in the calculated level of resistance (0.7 to 0.53). By adhering exactly to the recommended procedures for the BACTEC test method and by using log-phase inocula, this method shows better precision and accuracy at the 1% resistance level than does the proportional plate method.

Modification of Grimont biotyping system for epidemiologic studies with nosocomial Serratia marcescens isolates.

A modification of the Grimont biotyping system for Serratia marcescens permitted the rapid testing of nosocomial strains by a plate-disk assimilation technique instead of with individual substrate tubes.

Rapid, modified oxidase test for oxidase-variable bacterial isolates.

A modified oxidase reagent, 1% tetramethyl-p-phenylenediamine in dimethyl sulfoxide, proved superior to the routinely used 1% aqueous tetramethyl-p-phenylenediamine dihydrochloride in detecting weakly oxidase-positive gram-negative bacteria after 24 h of growth on agar media (40 of 40 positive versus 22 of 40 positive). The bacterial inoculum was obtained with a cotton-tipped swab instead of a loop or wooden applicator, and the reaction required less than 15 s.

Who introduced typhoid vaccination: Almroth Write or Richard Pfeiffer?

The British pathologist Almroth Wright generally is credited with the initiation of typhoid vaccination in 1896. His claims of priority were challenged as early as 1907 in favor of Richard Pfeiffer, a German bacteriologist and a student of Robert Koch. A review of the original literature of the 1890s and the early 1900s revealed that several groups were working on typhoid vaccine at the same time and that the credit for the initiation of typhoid vaccine studies should be shared by these two great researchers.

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.

[The effect of thiocyanate on bacterial plasmids using the plasmid screening test]. / Untersuchungen zum Einfluss von Thiocyanat auf Bakterienplasmide mit Hilfe des Plasmid-Screening-Tests.

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.

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.