Cryptococcus gattii infection in solid organ transplant recipients: description of Oregon outbreak cases.

Cryptococcus gattii was recognized as an emerging infection in the Pacific Northwest in 2004. Out of 62 total infections in Oregon since the outbreak, 11 were in solid organ transplant (SOT) recipients. SOT recipients were more likely to have disseminated disease and higher mortality than normal hosts, who mostly had isolated mass lesions. The median time from transplantation to C. gattii diagnosis was 17.8 months. The primary sites of infection were lung (n = 4), central nervous system (n = 3), or both (n = 4). The Oregon-endemic strain, VGII (subtypes IIa and IIc) was present in 10 of 11 patients; the median fluconazole minimum inhibitory concentration (MIC) was 12 µg/mL (range 2-32 µg/mL) for this strain. We found C. gattii infection among organ transplant recipients was disseminated at diagnosis, had low cerebrospinal fluid cryptococcal antigen titers, and was associated with an elevated fluconazole MIC and high attributable mortality.

Epidemiological and genetic characteristics of norovirus outbreaks in long-term care facilities, 2003-2006.

To identify the epidemiological and genetic characteristics of norovirus (NoV) outbreaks and estimate the impact of NoV infections in an older population, we analysed epidemiological and laboratory data collected using standardized methods from long-term care facilities (LTCFs) during 2003-2006. Faecal specimens were tested for NoV by real-time reverse transcriptase-polymerase chain reaction. NoV strains were genotyped by sequencing. Of the 234 acute gastroenteritis (AGE) outbreaks reported, 163 (70%) were caused by NoV. The annual attack rate of outbreak-associated NoV infection in LTCF residents was 4%, with a case-hospitalization rate of 3·1% and a case-fatality rate of 0·5%. GII.4 strains accounted for 84% of NoV outbreaks. Median duration of illness was longer for GII.4 infections than non-GII.4 infections (33 vs. 24 h, P<0·001). Emerging GII.4 strains (Hunter/2004, Minerva/2006b, Terneuzen/2006a) gradually replaced the previously dominant strain (Farmington Hills/2002) during 2004-2006. NoV GII.4 strains are now associated with the majority of AGE outbreaks in LTCFs and prolonged illness in Oregon.

Reactive arthritis following culture-confirmed infections with bacterial enteric pathogens in Minnesota and Oregon: a population-based study.

OBJECTIVE: To describe the epidemiology and clinical spectrum of reactive arthritis (ReA) following culture-confirmed infection with bacterial enteric pathogens in a population-based study in the USA. METHODS: We conducted telephone interviews of persons age>1 year with culture confirmed Campylobacter, Escherichia coli O157, Salmonella, Shigella and Yersinia infections reported to FoodNet (http://www.cdc.gov/FoodNet/) in Minnesota, USA and Oregon, USA between 2002 and 2004. SUBJECTS: with new onset joint pain, joint swelling, back pain, heel pain and morning stiffness lasting >or=3 days within 8 weeks of culture (possible ReA) were invited to complete a detailed questionnaire and physical examination. RESULTS: A total of 6379 culture-confirmed infections were reported; 70% completed screening interviews. Of these, 575 (13%) developed possible ReA; incidence was highest following Campylobacter (2.1/100,000) and Salmonella (1.4/100,000) infections. Risk was greater for females (relative risk (RR) 1.5, 95% CI, 1.3 to 1.7), adults (RR 2.5, 95% CI, 2.0 to 3.1) and subjects with severe acute illness (eg, fever, chills, headache, persistent diarrhoea). Risk was not associated with antibiotic use or human leukocyte antigen (HLA)-B27. A total of 54 (66%) of 82 subjects examined had confirmed ReA. Enthesitis was the most frequent finding; arthritis was less common. The estimated incidence of ReA following culture-confirmed Campylobacter, E coli O157, Salmonella, Shigella and Yersinia infections in Oregon was 0.6-3.1 cases/100,000. CONCLUSIONS: This is the first population-based study of ReA following infections due to bacterial enteric pathogens in the USA. These data will help determine the burden of illness due to these pathogens and inform clinicians about potential sequelae of these infections.

Group A streptococcal puerperal sepsis preceded by positive surveillance cultures.

BACKGROUND: Screening of pregnant women for vaginal and rectal carriage of group B streptococci may also identify group A streptococcal carriers. The clinical significance of prenatal group A streptococcal carriage is unknown. CASES: Two women developed group A streptococcal puerperal sepsis after delivery at one hospital 15 months apart. The first patient required hysterectomy and suffered complications including subcapsular hepatic hematoma, pleural effusion, and prolonged ileus. She recovered after a 35-day hospitalization. The second patient had endometritis and recovered. Both had had group A streptococci isolated from vaginal and rectal cultures taken for prenatal group B streptococcal screening. The acute sepsis isolates were both M-type 28, but pulsed-field gel electrophoresis determined that the strains were unrelated. CONCLUSIONS: Finding group A streptococci on prenatal culture may presage serious postpartum infection.

Macrolide resistance among invasive Streptococcus pneumoniae isolates.

CONTEXT: Macrolide antibiotics, including erythromycin, clarithromycin, and azithromycin, are the mainstays of empirical pneumonia therapy. Macrolide resistance among Streptococcus pneumoniae, the most common cause of community-acquired pneumonia, is increasing in the United States. Whether resistance is a significant problem or whether macrolides remain useful for treatment of most resistant strains is unknown. OBJECTIVE: To examine the epidemiology of macrolide-resistant pneumococci in the United States. DESIGN AND SETTING: Analysis of 15 481 invasive isolates from 1995 to 1999 collected by the Centers for Disease Control and Prevention's Active Bacterial Core surveillance system in 8 states. MAIN OUTCOME MEASURES: Trends in macrolide use (1993-1999) and resistance and factors associated with resistance, including examination of 2 subtypes, the M phenotype, associated with moderate minimum inhibitory concentrations (MICs), and the MLS(B) phenotype, associated with high MICs and clindamycin resistance. RESULTS: From 1993 to 1999, macrolide use increased 13%; macrolide use increased 320% among children younger than 5 years. Macrolide resistance increased from 10.6% in 1995 to 20.4% in 1999. M phenotype isolates increased from 7.4% to 16.5% (P<.001), while the proportion with the MLS(B) phenotype was stable (3%-4%). The median erythromycin MIC (MIC(50)) of M phenotype isolates increased from 4 microg/mL to 8 microg/mL. In 1999, M phenotype strains were more often from children than persons 5 years or older (25.2% vs 12.6%; P<.001) and from whites than blacks (19.3% vs 11.2%; P<.001). CONCLUSIONS: In the setting of increasing macrolide use, pneumococcal resistance has become common. Most resistant strains have MICs in the range in which treatment failures have been reported. Further study and surveillance are critical to understanding the clinical implications of our findings.

A nosocomial outbreak of fluoroquinolone-resistant salmonella infection.

BACKGROUND: Infection with fluoroquinolone-resistant strains of salmonella is rare, as is nosocomial salmonella infection. We describe the first recognized outbreak of fluoroquinolone-resistant salmonella infections in the United States, which occurred in two nursing homes and one hospital in Oregon. METHODS: We interviewed medical staff and reviewed patients' charts and death certificates. In Nursing Home A we conducted a case-control study. Patients were defined as residents of the nursing home from whom fluoroquinolone-resistant Salmonella enterica serotype Schwarzengrund was isolated between February 1996 and December 1998. Controls were residents with similar medical conditions whose cultures did not yield salmonella. We compared isolates using pulsed-field gel electrophoresis and sequence analysis. We reviewed pharmacy records to compare the use of fluoroquinolone among several nursing homes. RESULTS: Eleven patients with fluoroquinolone-resistant salmonellosis were identified at two nursing homes. The index patient had been hospitalized in the Philippines and had probably acquired the infection there. Transmission was probably direct (from patient to patient) or through contact with contaminated surfaces. Treatment with fluoroquinolones during the six months before a culture was obtained was associated with a significant risk of salmonella infection (4 of 5 patients had taken fluoroquinolones, as compared with 2 of 13 controls; odds ratio, 22.0; 95 percent confidence interval, 1.06 to 1177). The patients were not significantly more likely than the controls to have taken other antibiotics. More fluoroquinolones were used at Nursing Home A than at similar nursing homes in Oregon. The isolates from the outbreak had similar patterns on pulsed-field gel electrophoresis and the same gyrA mutations. The isolates from the outbreak were also similar to the only previous isolate of fluoroquinolone-resistant salmonella in the United States, which came from a patient in New York who had been transferred from a hospital in the Philippines. CONCLUSIONS: We describe a prolonged nosocomial outbreak of infection with fluoroquinolone-resistant S. enterica serotype Schwarzengrund. More such outbreaks are likely in institutional settings, particularly those in which there is heavy use of antimicrobial agents.

Emergence of antimicrobial-resistant shigellosis in Oregon.

Ampicillin and trimethoprim-sulfamethoxazole (TMP-SMZ) are currently considered acceptable empirical therapy for shigellosis in developed countries. However, there are few recently reported studies on antimicrobial resistance among shigellae isolated in the United States. We examined the epidemiology of shigellosis and the antimicrobial susceptibility of Shigella species isolated in Oregon from July 1995 through June 1998. Of 430 isolates, 410 were identified to the species level: Shigella sonnei accounted for 55% of isolates, and Shigella flexneri, for 40%. The overall annual incidence of shigellosis was 4.4 cases per 100,000 population. Children aged <5 years (annual incidence, 19.6 cases per 100,000 population) and Hispanics (annual incidence, 28.4 cases per 100,000 population) were at highest risk. Of 369 isolates tested, 59% were resistant to TMP-SMZ, 63% were resistant to ampicillin, 1% were resistant to cefixime, and 0.3% were resistant to nalidixic acid; none of the isolates were resistant to ciprofloxacin. Thirteen percent of the isolates had multidrug resistance to ampicillin, chloramphenicol, streptomycin, sulfisoxazole, and tetracycline. Infections due to multidrug-resistant shigellae are endemic in Oregon. Neither ampicillin nor TMP-SMZ should be considered appropriate empirical therapy for shigellosis any longer; when antibiotics are indicated, a quinolone or cefixime should be used.

Group B streptococcal disease in the era of intrapartum antibiotic prophylaxis.

BACKGROUND: Group B streptococcal infections are a leading cause of neonatal mortality, and they also affect pregnant women and the elderly. Many cases of the disease in newborns can be prevented by the administration of prophylactic intrapartum antibiotics. In the 1990s, prevention efforts increased. In 1996, consensus guidelines recommended use of either a risk-based or a screening-based approach to identify candidates for intrapartum antibiotics. To assess the effects of the preventive efforts, we analyzed trends in the incidence of group B streptococcal disease from 1993 to 1998. METHODS: Active, population-based surveillance was conducted in selected counties of eight states. A case was defined by the isolation of group B streptococci from a normally sterile site. Census and live-birth data were used to calculate the race-specific incidence of disease; national projections were adjusted for race. RESULTS: Disease in infants less than seven days old accounted for 20 percent of all 7867 group B streptococcal infections. The incidence of early-onset neonatal infections decreased by 65 percent, from 1.7 per 1000 live births in 1993 to 0.6 per 1000 in 1998. The excess incidence of early-onset disease in black infants, as compared with white infants, decreased by 75 percent. Projecting our findings to the entire United States, we estimate that 3900 early-onset infections and 200 neonatal deaths were prevented in 1998 by the use of intrapartum antibiotics. Among pregnant girls and women, the incidence of invasive group B streptococcal disease declined by 21 percent. The incidence among nonpregnant adults did not decline. CONCLUSIONS: Over a six-year period, there has been a substantial decline in the incidence of group B streptococcal disease in newborns, including a major reduction in the excess incidence of these infections in black infants. These improvements coincide with the efforts to prevent perinatal disease by the wider use of prophylactic intrapartum antibiotics.

Increasing prevalence of multidrug-resistant Streptococcus pneumoniae in the United States.

BACKGROUND: The emergence of drug-resistant strains of bacteria has complicated treatment decisions and may lead to treatment failures. METHODS: We examined data on invasive pneumococcal disease in patients identified from 1995 to 1998 in the Active Bacterial Core Surveillance program of the Centers for Disease Control and Prevention. Pneumococci that had a high level of resistance or had intermediate resistance according to the definitions of the National Committee for Clinical Laboratory Standards were defined as "resistant" for this analysis. RESULTS: During 1998, 4013 cases of invasive Streptococcus pneumoniae disease were reported (23 cases per 100,000 population); isolates were available for 3475 (87 percent). Overall, 24 percent of isolates from 1998 were resistant to penicillin. The proportion of isolates that were resistant to penicillin was highest in Georgia (33 percent) and Tennessee (35 percent), in children under five years of age (32 percent, vs. 21 percent for persons five or more years of age), and in whites (26 percent, vs. 22 percent for blacks). Penicillin-resistant isolates were more likely than susceptible isolates to have a high level of resistance to other antimicrobial agents. Serotypes included in the 7-valent conjugate and 23-valent pneumococcal polysaccharide vaccines accounted for 78 percent and 88 percent of penicillin-resistant strains, respectively. Between 1995 and 1998 (during which period 12,045 isolates were collected), the proportion of isolates that were resistant to three or more classes of drugs increased from 9 percent to 14 percent; there also were increases in the proportions of isolates that were resistant to penicillin (from 21 percent to 25 percent), cefotaxime (from 10 percent to 15 percent), meropenem (from 10 percent to 16 percent), erythromycin (from 11 percent to 16 percent), and trimethoprim-sulfamethoxazole (from 25 percent to 29 percent). The increases in the frequency of resistance to other antimicrobial agents occurred exclusively among penicillin-resistant isolates. CONCLUSIONS: Multidrug-resistant pneumococci are common and are increasing. Because a limited number of serotypes account for most infections with drug-resistant strains, the new conjugate vaccines offer protection against most drug-resistant strains of S. pneumoniae.

Tracking drug-resistant Streptococcus pneumoniae in Oregon: an alternative surveillance method.

With the emergence of drug-resistant Streptococcus pneumoniae, community-specific antimicrobial susceptibility patterns have become valuable determinants of empiric therapy for S. pneumoniae infections. Traditionally, these patterns are tracked by active surveillance for invasive disease, collection of isolates, and centralized susceptibility testing. We investigated whether a simpler and less expensive method aggregating existing hospital antibiograms--could provide community-specific antimicrobial susceptibility data. We compared 1996 active surveillance data with antibiogram data from hospital laboratories in Portland, Oregon. Of the 178 S. pneumoniae active surveillance isolates, 153 (86% [95% confidence interval (CI) = 80% to 91%]) were susceptible to penicillin. Of the 1,092 aggregated isolates used by hospitals to generate antibiograms, 921 (84% [95% CI = 82%-87%]) were susceptible to penicillin. With the exception of one hospital's erythromycin susceptibility results, hospital-specific S. pneumoniae susceptibilities to penicillin, cefotaxime, trimethoprim-sulfamethoxazole, and erythromycin from the two methods were statistically comparable. Although yielding fewer data than active surveillance, antibiograms provided accurate, community-specific drug-resistant S. pneumoniae data in Oregon.

Vancomycin in Oregon: who's using it and why.

OBJECTIVE: To determine the proportion of vancomycin orders that are appropriate according to national guidelines and to identify targets for educational messages. DESIGN: Population-based study of vancomycin use in Oregon during a 3-week period. Survey of pharmacists, prospective flagging of vancomycin orders, and data abstraction from patient charts using standardized forms. SETTING: Nonpsychiatric hospitals in Oregon. RESULTS: Four (6%) of the 66 Oregon hospitals had pharmacy restrictions on initial vancomycin orders. Sixty-four (97%) of the hospitals participated in the study of indications for use; 293 vancomycin orders were reported; 3.8 courses were initiated per 1,000 patient-days. Indications for use were determined for 266 (91%); of these, 159 (60%) were deemed appropriate. Of uses for prophylaxis, empirical treatment of suspected gram-positive infection, and treatment of documented gram-positive infection, 57%, 56%, and 65%, respectively, were appropriate. Of hospitals with <250, 251-475, and >475 licensed beds, 65%, 58%, and 57% of vancomycin orders were appropriate. No single medical specialty accounted for >16% of inappropriate vancomycin use. CONCLUSIONS: Vancomycin was used inappropriately by physicians of many different specialties, in hospitals of all sizes, and in sundry clinical situations. The problem of inappropriate vancomycin use does not lend itself to solution by educational strategies targeted at specific subgroups; restrictions by hospital pharmacies may be required.

Hamburger-associated Escherichia coli O157:H7 infection in Las Vegas: a hidden epidemic.

OBJECTIVES: This study sought to determine whether a multistate fast food hamburger-associated outbreak of Escherichia coli O157:H7 infection involved Las Vegas residents as well and, if so, why public health officials had not detected it. METHODS: A matched case-control study was conducted among persons with bloody diarrhea and their healthy meal companions. Hamburger production, distribution, and cooking methods were reviewed. Unused hamburger patties were cultured, and E. coli O157:H7 isolates were characterized. Local laboratory stool culture practices were reviewed. RESULTS: Fifty-eight cases of bloody diarrhea were identified. Illness was associated with eating regular hamburgers (matched odds ratio [OR] = 9.0, 95% confidence interval [CI] = 1.02,433.4), but 25% of ill persons reported eating only jumbo hamburgers. Regular and jumbo hamburger patties yielded E. coli O157:H7 indistinguishable from the lone clinical isolate. No local laboratory cultured routinely for E. coli O157:H7 until after the outbreak. CONCLUSIONS: A large outbreak of E. coli O157:H7 infections escaped timely notice in Las Vegas because local laboratories did not culture for this pathogen. Health officials should encourage laboratories to screen at least all bloody stools on sorbitol-MacConkey medium.

Evaluation of a statewide bicycle helmet law via multiple measures of helmet use.

OBJECTIVES: To evaluate an Oregon law requiring bicyclists younger than 16 year to wear a helmet and to compare methods of measuring helmet use. DESIGN: Four prelaw and postlaw statewide helmet use surveys: (1) statewide observations, (2) middle school observations, (3) classroom self-report surveys, and (4) a statewide adult telephone survey. SETTING: Oregon. SUBJECTS: Statewide observations, 3313 child bicyclists at 13 sites; middle school observations, 995 child bicyclists at 33 randomly selected middle schools; classroom self-report surveys, fourth, sixth, and eighth graders in 448 classrooms (ie, 8955 students) before the law was effected and 456 classrooms (ie, 9811 students) after the law was effected in 66 randomly selected schools; and statewide telephone survey, 1219 randomly called parents of 1437 children younger than 16 years. MAIN OUTCOME MEASURES: Prelaw and postlaw helmet use and ownership and knowledge and opinion about the law. RESULTS: Observed helmet use among youth was 24.5% before the law was effected and 49.3% after the law was effected. School-observed use increased from 20.4% to 56.1%. Classroom survey self-reported "always" use of helmets increased from 14.7% to 39.4%; reported use on the day of the survey increased from 25.8% to 76.0%. Telephone survey-reported "always" helmet use increased from 36.8% to 65.7%. Younger children and girls were more likely to use helmets. Most students (ie, 87.8%) and parents (ie, 95.4%) knew about the law; however, only 42.6% of children thought the law was a good idea. CONCLUSIONS: We conclude that (1) the law increased helmet use; (2) although use estimates differ, all helmet surveys showed similar degrees of prelaw and postlaw change; and (3) half of child bicyclists are still not wearing helmets, indicating a need for additional promotion of helmet wearing. Laws seem to be an effective way to increase helmet use.

An outbreak of type A botulism associated with a commercial cheese sauce.

BACKGROUND: Although botulism is rare, recognition of a possible case of this illness represents a public health emergency. To prevent more cases, prompt investigation must be done to determine whether illness is linked to commercial product or restaurant. Botulism can masquerade as other illnesses, and seemingly unlikely foods can harbor botulinum toxin. OBJECTIVE: To confirm the diagnosis and determine the cause and extent of an outbreak of botulism associated with food served at a delicatessen. DESIGN: Retrospective cohort study of patrons of the delicatessen; laboratory analysis of food, serum samples, and stool samples; and traceback of implicated food. SETTING: Community in Georgia. PARTICIPANTS: Patrons of the delicatessen. MAIN OUTCOME MEASURES: Botulinum toxin in food, serum, or stool and Clostridium botulinum in food and stools. RESULTS: 8 of 52 patrons (15%) met the case definition for botulism. In 4 of the 8 patrons, and illness other than botulism was initially diagnosed. Five of the 8 were hospitalized, and 1 died. Stool cultures from 4 patrons yielded type AC. botulinum, and two serum samples contained botulinum toxin. All ill persons ate food from the delicatessen on 1 October 1993. Of the 22 persons who ate at the delicatessen that day, all 8 ill persons but none of the 14 well persons ate a potato stuffed with meat and cheese sauce. An open can of cheese sauce contained type A botulinum toxin and yielded C botulinum on culture. Cheese sauce experimentally inoculated with C botulinum spores became toxic after 8 days at a temperature of 22 degrees C (room temperature). CONCLUSIONS: A commercial, canned cheese caused a botulism outbreak. This product readily becomes toxic when contaminated by C botulinum spores and left at room temperature. Mild botulism caused by unusual vehicles may be misdiagnosed. Botulism should be included in the differential diagnosis of persons with signs or symptoms of acute cranial nerve dysfunction.

Preventable disease in correctional facilities. Desmoteric foodborne outbreaks in the United States, 1974-1991.

BACKGROUND: Various disease outbreaks have been reported among prisoners. Recent foodborne outbreaks in correctional facilities in Georgia and Delaware prompted us to review the epidemiological characteristics of such outbreaks reported in the United States. METHODS: Foodborne outbreaks reported to the Centers for Disease Control and Prevention as part of routine surveillance from 1974 to 1991 were examined to identify outbreaks in jails, prisons, correctional facilities, and juvenile detention centers. Outbreak sizes, temporal trends, food vehicles, pathogens, and hygienic transgressions were analyzed. RESULTS: Eighty-eight desmoteric foodborne outbreaks involving 14307 cases of illness were reported from 31 states and territories. The mean outbreak size was 163 cases, compared with a mean of 31 cases for the 9107 reported outbreaks not involving prisoners. No fatalities among prisoners were reported. No pathogen was identified in 47 (53%) of the 88 outbreaks Salmonella species accounted for 15 (37%) of 41 outbreaks of known cause from 1974 to 1991, Clostridium perfringens for 14 (34%), and Staphylococcus aureus for 9 (22%). Fourteen of 15 Salmonella outbreaks occurred from 1984 to 1991. Food vehicles were reported for 63 (72%) of the outbreaks. Beef and poultry each were implicated in 9 (14%) of these, followed by fish or poultry salads and Mexican food, which accounted for 6 outbreaks (10%). Food-handling errors were reported for 69 (78%) of the 88 outbreaks. Improper food storage was reported in 62 (90%) of these. CONCLUSIONS: Foodborne outbreaks are reported regularly from correctional facilities in the United States. Outbreaks caused by Salmonella species, a special threat to prisoners with human immunodeficiency virus infection, seem to be increasing. Food production in correctional facilities should meet minimum safety standards, including sufficient refrigeration facilities, training of food handlers, and exemption of ill food handlers from work.

Antibodies to the serine rich Entamoeba histolytica protein (SREHP) prevent amoebic liver abscess in severe combined immunodeficient (SCID) mice.

Amoebic liver abscess caused by Entamoeba histolytica is a major cause of morbidity and mortality worldwide. We used mice with severe combined immunodeficiency (SCID mice) to study the role of antibody in protection from amoebic liver abscess, and to identify protective antigens of E. histolytica. Antisera to recombinant versions of two major surface antigens of E. histolytica, the serine rich E. histolytica protein (SREHP) and the 170 kDa adhesin were used in this study. We found that 100% of SCID mice passively immunized with antiserum to the recombinant SREHP molecule were protected from developing amoebic liver abscess after intrahepatic challenge with virulent E. histolytica trophozoites. In contrast, preimmune serum, antiserum to a portion of the 170 kDa adhesin, and antiserum to the trpE fusion partner of SREHP did not protect SCID mice from amoebic liver abscess. Our study demonstrates that antibodies to a recombinant version of the amoebic SREHP molecule can protect against amoebic liver abscess, and suggest the recombinant SREHP molecule should be considered as a possible vaccine candidate to prevent amoebic liver abscess.

Protection of gerbils from amebic liver abscess by immunization with a recombinant Entamoeba histolytica antigen.

Amebiasis, infection by the intestinal protozoan parasite Entamoeba histolytica, is a leading parasitic cause of death. As a step in the development of a recombinant antigen vaccine to prevent E. histolytica infection, we looked at the ability of a recombinant version of the serine-rich E. histolytica protein (SREHP) to elicit a protective immune response against invasive amebic disease. Gerbils, a standard model for amebic liver abscess, were immunized with either a recombinant SREHP/maltose-binding protein (MBP) fusion, recombinant MBP alone, or phosphate-buffered saline (PBS), all combined with complete Freund's adjuvant. In the first trial (group 1), gerbils received a primary and two booster immunizations intraperitoneally; in the second trial (group 2), gerbils were immunized by a single intradermal injection. SREHP/MBP-immunized gerbils in both groups produced antibody to native SHEHP and developed delayed-type hypersensitivity responses to recombinant SREHP. All gerbils were challenged by an intrahepatic injection with 5 x 10(4) virulent E. histolytica HM1-IMSS trophozoites. Complete protection from amebic liver abscess was seen in 64% of the SHEHP/MBP-immunized gerbils in group 1 and in 100% of the SREHP/MBP-immunized gerbils in group 2. There was no protection observed in MBP- or PBS-immunized gerbils in either group. Our results indicate that the SREHP molecule has potential as a vaccine to prevent amebic infection and demonstrate that successful vaccination of animals with recombinant E. histolytica antigen vaccines is possible.

Expression of a recombinant Entamoeba histolytica antigen in a Salmonella typhimurium vaccine strain.

The expression of a major surface antigen of the intestinal protozoal parasite Entamoeba histolytica in an attenuated Salmonella typhimurium vaccine strain is described. A polymerase chain reaction fragment derived from cDNA encoding the serine-rich Entamoeba histolytica protein, SREHP, was introduced into S. typhimurium chi 3987 (delta cya delta crp delta asd) using a plasmid expression vector (pYA292) containing the aspartate semialdehyde (asd) gene. S. typhimurium expressing recombinant SREHP as a SREHP/maltose binding protein fusion protein was administered orally to mice and gerbils (an important animal model for E. histolytica infection) and was recovered from splenic tissue in both species. Our study demonstrates the feasibility of expressing recombinant amoebic proteins in attenuated S. typhimurium strains, and shows that vaccine strains of S. typhimurium can successfully infect the gerbil, a widely used model for amoebic liver abscess and intestinal amoebiasis.