Blastocystis hominis: an organism in search of a disease.

Blastocystis hominis is a protozoan organism frequently found in the human intestinal tract. Eleven consecutive patients with symptoms of enteritis and having B. hominis as the sole enteropathogen were studied in an attempt to define the association of blastocystosis with clinical disease. B. hominis could not be implicated as the etiologic agent of enteritis in any of these patients. All eleven had alternative (and usually noninfectious) explanations for their intestinal symptoms. There was no correlation between resolution of symptoms and either antiprotozoal therapy or disappearance of B. hominis from the stools. All prior reports associating B. hominis with human disease have been reviewed and provide no convincing proof of a causal relation. B. hominis is rarely, if ever, a human pathogen, and treatment directed at the eradication of B. hominis is not indicated.

Comparison of quantitative and semiquantitative culture techniques for burn biopsy.

Accurate evaluation of bacterial colonization as a predictive index for wound sepsis has relied on a quantitative culture technique that provides exact colony counts per gram of tissue by culture of five serial dilutions of biopsy tissue homogenate. The method, while useful to the physician, is both labor intensive and expensive. In this study 78 eschar biopsies were cultured by a semiquantitative technique that involved the use of 0.1- and 0.01-ml samples of inocula and by the serial dilution method. Exact colony counts from the semiquantitative culture method were available only from cultures containing 10(4) to 10(6) CFU/g of tissue. Other colony counts were reported as less than 10(4) or greater than 10(6) CFU/g. Agreement by category of colony counts between the two methods was 96%. For prediction of wound sepsis, the semiquantitative procedure had a positive predictive value of 100% and a negative predictive value of 93.7%. This method also resulted in an approximately 30% reduction of work units (as defined by the College of American Pathologists) and a 60% reduction in the amount of media for specimen processing. Therefore, this semiquantitative culture technique provides accurate information to the physician while saving both time and materials.

Stratified outcome comparison of clindamycin-gentamicin vs chloramphenicol-gentamicin for treatment of intra-abdominal sepsis.

A randomized, prospective trial was conducted of 93 patients with operatively confirmed intra-abdominal sepsis. The study compared clindamycin-gentamicin and chloramphenicol-gentamicin for treatment of carefully stratified patient groups. Malnutrition, age over 65 years, shock, alcoholism, gastrointestinal tract bleeding, steroid administration, diabetes, obesity, and organ malfunction were present with equal frequencies in each group. The duration of antibiotic treatment averaged 8 1/2 days, and the average length of postoperative hospitalization was 29 days. Study antibiotics were changed for bacteriologic reasons in 11 patients taking clindamycin-gentamicin and 12 patients taking chloramphenicol-gentamicin (25% of the total), and two patients in the clindamycin-gentamicin group had a minor adverse reaction. Initial satisfactory clinical responses were obtained in 59 (63%) patients. Twenty-five patients (27%) subsequently developed unsatisfactory courses, but 48 (52%) patients remained well through the 30-day period. Septic-related mortality occurred in 18 (19%) patients, and two (2%) patients had unrelated deaths. There were no significant differences between the study regimens by the outcome criteria evaluated.

Paragonimiasis: diagnosis and the use of praziquantel in treatment.

Paragonimiasis was diagnosed in eight patients: five with sputum specimens positive for characteristic ova and three with only stool specimens positive for ova. Clinical symptoms, roentgenograms and serologic findings appeared to correlate with severity of disease. All eight patients were treated with praziquantel (oral dose, 75 mg/kg of body weight daily for two consecutive days). Of seven patients who completed the treatment, six had ova-negative sputum and stool specimens by day 90; the seventh patient's specimens became ova negative by day 120. The eighth patient, who had failed to respond to prior treatment with bithionol, could not tolerate the daily dosage of 75 mg/kg because of nausea. Although he received the same total dose (150 mg/kg) over four days his specimens remained ova positive on day 90. Adverse effects included nausea (two patients), headache (one patient), and urticaria (two), the last effect possibly secondary to release of antigen from drug-damaged parasites. A review of the epidemiology, clinical presentation, and treatment of pulmonary paragonimiasis is presented.

Evaluation of GonoGen coagglutination test for serodiagnosis of Neisseria gonorrhoeae: identification of problem isolates by auxotyping, serotyping, and with a fluorescent antibody reagent.

GonoGen (Micro-Media Systems, Potomac, MD) is a commercially available coagglutination test for the identification of Neisseria gonorrhoeae. We tested 84 strains of Neisseria spp. and Branhamella catarrhalis, including 50 clinical isolates of N. gonorrhoeae. Eighty-six percent (51/59) of N. gonorrhoeae, including 86% (43/50) of clinical isolates of N. gonorrhoeae, were identified correctly in the GonoGen test. In contrast, all N. gonorrhoeae isolates reacted with a fluorescent antibody research reagent composed of monoclonal antibodies. Both reagents were specific for N. gonorrhoeae. Clinical isolates were classified by auxotyping and were serotyped with research monoclonal antibody reagents in coagglutination tests to characterize problem isolates; two auxotype/serovar classes, prototrophic/IA-4 and proline-requiring/IA-4, accounted for 71% (5/7) of GonoGen-negative clinical isolates. Five of the seven isolates that were missed with the first GonoGen lot we tested did react with a second lot of GonoGen reagent. Investigators from different cities in the U.S. have reported different rates of success with GonoGen. Our results indicate that certain N. gonorrhoeae serovars may account for the difference in performance observed with serological tests.

Staphylococcus saprophyticus beta-lactamase production and disk diffusion susceptibility testing for three beta-lactam antimicrobial agents.

beta-Lactamase production and MIC determinations for penicillin, methicillin, and cephalothin were assessed for 67 strains of Staphylococcus saprophyticus and correlated with results of disk diffusion susceptibility testing. Fifty-five (82%) of the 67 strains produced beta-lactamase, and 40 (77%) of these beta-lactamase-producing strains were susceptible (zone size, greater than 29 mm) by disk diffusion techniques. Although the range of zone sizes for beta-lactamase producers was broad (26 to 36 mm), all 38 strains with a zone size of less than 31 mm by disk diffusion testing were beta-lactamase producers compared with 17 (59%) of 29 with larger zone sizes (P = 0.0000008). The median penicillin MIC for 12 S. saprophyticus strains was 0.25 micrograms/ml and was not related to beta-lactamase production. Although the methicillin MICs for 15 strains were in the susceptible range (4.0 micrograms/ml), interpretation of disk diffusion testing for oxacillin varied greatly among laboratories using identically prepared media and standardized techniques. Criteria presently used to define susceptibility of Staphylococcus aureus to penicillin and oxacillin by disk diffusion are inappropriate for S. saprophyticus. The clinical significance of the beta-lactamase produced by these strains needs further evaluation.

Characterization of Neisseria cinerea, a nonpathogenic species isolated on Martin-Lewis medium selective for pathogenic Neisseria spp.

An asaccharolytic, gram-negative, oxidase-positive diplococcus was isolated on Martin-Lewis medium from the cervix of a patient attending an arthritis clinic at Seattle Public Health Hospital, Seattle, Wash. This strain, NRL 32165, did not produce detectable acid from glucose, maltose, sucrose, fructose, mannitol, or lactose in either cystine Trypticase agar (BBL Microbiology Systems, Cockeysville, Md.) or modified oxidation-fermentation medium and was identified presumptively as a glucose-negative Neisseria gonorrhoeae strain, but was identified later as Neisseria cinerea on the basis of its biochemical reactions. Nitrate was not reduced, nitrite (0.001%, wt/vol) was reduced, and polysaccharide was not produced from sucrose. Proline, arginine, and cystine-cysteine were required for growth on defined medium. Strain NRL 32165 did not react with antigonococcal protein I monoclonal antibodies and did not produce immunoglobulin A protease. In DNA:DNA homology studies with N. gonorrhoeae NRL 8038 (F62) and N. cinerea type strain NRL 30003, strain NRL 32165 showed 95% homology relative to N. cinerea and 44% homology relative to N. gonorrhoeae. Thus, the identity of strain NRL 32165 was confirmed as N. cinerea (von Lingelsheim 1906) Murray 1939. Of all Neisseria spp., N. cinerea is most likely to be misidentified as a glucose-negative N. gonorrhoeae strain.

Successful praziquantel treatment of paragonimiasis following bithionol failure. A case report.

A patient from Southeast Asia with cough and hemoptysis was documented to have pulmonary paragonimiasis. Initial treatment with bithionol failed. The patient was then treated with praziquantel 75 mg/kg body weight a day for 2 days under an investigational protocol. Subsequent follow-up studies showed clinical improvement and indicated parasitologic cure. A concurrent asymptomatic Clonorchis infection was also cured following praziquantel treatment. Side effects were minor.

Effect of clindamycin on growth and haemolysin production by Escherichia coli.

The effect of clindamycin on growth and haemolysin production by four strains of Escherichia coli was tested. Clindamycin MICs were greater than 256 mg/l for all strains. Clindamycin concentrations of 16-256 mg/l significantly inhibited growth, while concentrations from 2-32 mg/l significantly inhibited haemolysin production. Administration of clindamycin to rats with peritonitis due to haemolytic E. coli reduced mortality. Subinhibitory concentrations of clindamycin can inhibit growth and haemolysin production by E. coli and reduce mortality in an animal model of haemolytic E. coli peritonitis.

Determinants of organ malfunction or death in patients with intra-abdominal sepsis. A discriminant analysis.

One hundred and six patients found at operation to have intra-abdominal sepsis were prospectively followed up to determine the incidence of organ malfunction and death. These outcomes were correlated with age, preexisting disease, underlying cause of sepsis, shock, nutritional status, and alcoholism. Organ malfunction occurred in 31 patients (29%), 19 (61%) of whom died. Two (3%) of 75 patients without organ malfunction died. Discriminant analysis revealed a significantly increased risk of death in patients with shock at any time, age greater than 65 years, alcoholism, bowel infarction, or malnutrition. A discriminant equation based only on preoperative variables correctly assigned the outcome of death or survival in 97 (92%) of the patients based on probabilities derived from this analysis. At present, this information is primarily of interest for researchers comparing outcomes in groups of patients, but with additional refinements it may become clinically useful for individual patients.

Genetics of hemolysin of Escherichia coli.

The expression of alpha-hemolysin is a property frequently associated with Escherichia coli extraintestinal infections. We have examined the genetic basis for hemolysin expression by an E. coli strain isolated from a human urinary tract infection. The genes necessary for hemolysin synthesis were found to be chromosomal and to map near the ilv gene cluster. Isogenic hly+ and hly derivatives were also prepared and tested for virulence in the chicken embryo model system. Hemolysin was found to be necessary but not in itself sufficient for E. coli virulence in this in vitro model.

Mutational enzymatic resistance of Enterobacter species to beta-lactam antibiotics.

Mutants with enhanced beta-lactam resistance were selected from strains of Enterobacter cloacae and E. aerogenes by using three antibiotics. High-level beta-lactamase-producing mutants had similar degrees of increased resistance, enzyme substrate profiles, and isoelectric (pI) values irrespective of the selective agent. Reverse mutants from a resistant E. cloacae mutant regained the susceptibility pattern originally exhibited by the wild type, or were of enhanced susceptibility, and no longer expressed increased beta-lactamase production. beta-Lactamases of the mutants were similar in pI values to the wild-type enzyme. The increased resistance of the mutants therefore appeared to be accounted for by increased beta-lactamase production.

Duration of preventive antibiotic administration for penetrating abdominal trauma.

Eighty-two patients with penetrating abdominal trauma and visceral injuries requiring laparotomy were prospectively randomized to receive either 12 hours or five days of penicillin G potassium and doxycycline hyclate beginning before operation. Distribution between groups was equivalent for all risk factors except shock, which was more prevalent in the 12-hour group. Antibiotics were first administered an average of 64 minutes following injury, and 90% of all patients had received antibiotics and were being operated on within 3 hours 15 minutes. Overall infection rates were 17% in patients with colon penetration, 14% in patients without colon penetration but with other intestinal penetration, and 0% in patients without intestinal penetration. Twelve-hour and five-day antibiotic regimens were comparable in the prevention of postoperative infectious complications following penetrating abdominal injuries. Intestinal penetration was the most important risk factor for developmental of infectious complications in this patient population.

Implications of leukocytosis and fever at conclusion of antibiotic therapy for intra-abdominal sepsis.

Outcomes of 65 patients after operation who had exhibited a clinical response to treatment for intra-abdominal sepsis were compared based on the presence or absence of leukocytosis and fever at the conclusion of antibiotic therapy. Fifty-one patients were afebrile when antibiotics were stopped. Intra-abdominal infection developed in 7 of 21 (33%) who had a persistent leukocytosis, but no intra-abdominal infections developed after operation in 30 patients who had normal WBC counts at the end of antibiotic treatment (p less than 0.005). Nosocomial infections developed in 6 (12%) of the 51 patients, and there was no difference in the incidence between patients with or without leukocytosis. Eleven of 14 (79%) patients who were still febrile when antibiotics were discontinued developed infections after operation. Nosocomial infections occurred in three (21%) and intra-abdominal infections in eight (57%). Of the 15 patients who developed intra-abdominal infection after operation, only four responded to appropriate antibiotic treatment without requiring further surgery. The other patients required surgical management for definitive control within two months of the initial operation. In conclusion, patients at risk of developing infection after operation after exhibiting a clinical response to treatment of intra-abdominal sepsis are those who are afebrile with a persistent leukocytosis or who are still febrile when antibiotics are stopped.

Construction and expression of recombinant plasmids encoding type 1 or D-mannose-resistant pili from a urinary tract infection Escherichia coli isolate.

Isolates of Escherichia coli from human urinary tract infections frequently express adherence properties found less often among normal intestinal isolates. These properties include adherence to human uroepithelial cells and primary monkey kidney cells, as well as D-mannose-resistant hemagglutination of human erythrocytes, and they are mediated by a pilus type different from type 1. The genes encoding this pilus type (pyelonephritis-associated pili, pap) and those encoding type 1 pili have been cloned from a urinary tract infection isolate of E. coli and transferred to an E. coli K-12 derivative. The recombinant plasmids were found to express functional pili and to endow the new host with all of the adherence properties of the urinary tract infection isolate. Both pilus types were found to be genetically distinct, and unlike the adherence genes from bovine, porcine, and human diarrheal isolates, both were found to be chromosomally encoded.

Effect of ionized calcium and soluble magnesium on the predictability of the performance of Mueller-Hinton agar susceptibility testing of Pseudomonas aeruginosa with gentamicin.

The soluble and ionized calcium and magnesium contents of 18 lots of Mueller-Hinton agar medium from three different manufacturers were analyzed, and the results were correlated with medium performance. A standardized disk diffusion test, with Pseudomonas aeruginosa (ATCC 27853) and a 10-microgram gentamicin disk, served as an indicator of medium performance. Zone diameters correlated well with the ionized calcium values and the sum of the ionized calcium and soluble magnesium values in the different lots (r = -0.88 for both). Zone diameters correlated poorly with ionized magnesium values (r = -0.57), which were best described by a curvilinear relationship. Supplementation of lots of Mueller-Hinton agar medium with equivalent amounts of calcium and magnesium as the chloride, gluconate, or glycerophosphate salts produced identical decreases in zone sizes. Adjustment of deficient lots of Mueller-Hinton agar medium with ionized calcium or soluble magnesium or both (as the gluconate salts), to match the concentrations in lots that provided satisfactory zone sizes (17 to 19 mm), resulted in performance comparable to that of the control lots. Sixteen strains of Pseudomonas aeruginosa, ranging from resistant to susceptible, responded to cation adjustment in the same manner as the ATCC quality control strain. Satisfactory medium performance can obviously be assured by biological means in aminoglycoside susceptibility testing of Pseudomonas aeruginosa on Mueller-Hinton medium; however, cation adjustment of medium to predetermined levels of ionized calcium and soluble magnesium can now also provide desirable performance levels for P. aeruginosa on Mueller-Hinton medium.

Leukocytosis at termination of antibiotic therapy: its importance for intra-abdominal sepsis.

Postoperative outcomes of 31 afebrile patients who had responded to treatment for intra-abdominal sepsis were compared based on the presence or absence of leukocytosis (WBC count greater than 10,000/cu mm) at the conclusion of antibiotic therapy. In 68% of the patients who had leukocytosis, postoperative septic complications developed within two months of their operation. In patients without leukocytosis, complications developed in only 8.3%. Afebrile patients who exhibit leukocytosis but have responded clinically to treatment are at risk for postoperative infection and multisystem failure.

Cation components of Mueller-Hinton agar affecting testing of Pseudomonas aeruginosa susceptibility to gentamicin.

Seven lots of Mueller-Hinton agar were examined for calcium and magnesium contents and their distribution in pools or compartments. Gel disruption and centrifugation yielded the soluble cations, which varied from 9 to 113% of the total calcium and from 76 to 102% of the total magnesium. Throughout the experiments, a standardized disk diffusion test, using Pseudomonas aeruginosa (ATCC 27852) and a 10-mug gentamicin disk, served as an indicator for medium performance. Zone diameters correlated well with the sums of the soluble calcium and magnesium values in the different lots (r = -0.85). Ionized calcium, presumably the biologically active ion, was measured with a calcium-specific electrode. It represented only a fraction of the soluble calcium pool in three lots. Autoclaving resulted in shifts of the cations between the different pools. Addition of magnesium to one medium lot resulted in shifts of soluble and ionized calcium, indicating an interdependence of calcium and magnesium, and zone diameters correlated with soluble magnesium (r = -0.98), soluble calcium (r = -0.96), and ionized calcium (r = -0.96) in this experiment. Manipulation of one medium to match the performance of another showed that excess amounts of both ions were required to obtain similar performance. Satisfactory performance of an individual medium can be obtained by cation supplementation, but simple adjustment will not suffice for all media. The interaction of the other cation pool components must also be evaluated.

In vitro response of Enterobacter to ampicillin.

Three strains of Enterobacter were studied for their response to ampicillin. They exhibited a basic level of resistance that depended on the medium used and high-level mutational resistance at a frequency of 10(-5) to 10(-7). Two classes of mutants were selected, one of which showed markedly enhanced antibiotic inactivation as indicated by a biological assay and the other of which resembled the wild type in this regard. Both mutants showed cross-resistance to other beta-lactam antibiotics. The results explained discrepancies between traditional broth dilution minimum inhibitory concentration tests and early read automated procedures.

Erythromycin and clindamycin resistance in Corynebacterium diphtheriae from skin lesions.

Erythromycin- and clindamycin-resistant Corynebacterium diphtheriae isolates were recovered from skin lesions. Resistance to erythromycin and clindamycin was induced by a subinhibitory concentration (0.03 microgram/ml) of erythromycin. Clindamycin (0.07 microgram/ml) was a more effective inducer of its own resistance than of erythromycin resistance. Erythromycin-inducible cross-resistance to vernamycin B alpha was demonstrated in disk diffusion tests.