Effective control measures limited measles outbreak after extensive nosocomial exposures in January-February 2008 in Gothenburg, Sweden

In January-February 2008, one imported case of measles initiated a series of exposures with around 380 nosocomial secondary contacts. Susceptible individuals were traced early and control measures were initiated that managed to limit the consequences considerably. Only four secondary cases were identified by the end of March. This minor outbreak illustrates the importance and efficiency of early control measures as well as the fact that the risk of measles outbreaks still exists in a country that has high measles, mumps, rubella vaccination coverage among children.

Effective control measures limited measles outbreak after extensive nosocomial exposures in January-February 2008 in Gothenburg, Sweden

In January-February 2008, one imported case of measles initiated a series of exposures with around 380 nosocomial secondary contacts. Susceptible individuals were traced early and control measures were initiated that managed to limit the consequences considerably. Only four secondary cases were identified by the end of March. This minor outbreak illustrates the importance and efficiency of early control measures as well as the fact that the risk of measles outbreaks still exists in a country that has high measles, mumps, rubella vaccination coverage among children.

Nasal and vaginal vaccinations have differential effects on antibody responses in vaginal and cervical secretions in humans

Sexually transmitted diseases are a major health problem worldwide, but there is still a lack of knowledge about how to induce an optimal immune response in the genital tract of humans. In this study we vaccinated 21 volunteers nasally or vaginally with the model mucosal antigen cholera toxin B subunit and determined the level of specific immunoglobulin A (IgA) and IgG antibodies in vaginal and cervical secretions as well as in serum. To assess the hormonal influence on the induction of antibody responses after vaginal vaccination, we administered the vaccine either independently of the stage in the menstrual cycle or on days 10 and 24 in the cycle in different groups of subjects. Vaginal and nasal vaccinations both resulted in significant IgA and IgG anti-cholera toxin B subunit responses in serum in the majority of the volunteers in the various vaccination groups. Only vaginal vaccination given on days 10 and 24 in the cycle induced strong specific antibody responses in the cervix with 58-fold IgA and 16-fold IgG increases. In contrast, modest responses were seen after nasal vaccination and in the other vaginally vaccinated group. Nasal vaccination was superior in inducing a specific IgA response in vaginal secretions, giving a 35-fold increase, while vaginal vaccination induced only a 5-fold IgA increase. We conclude that a combination of nasal and vaginal vaccination might be the best vaccination strategy for inducing protective antibody responses in both cervical and vaginal secretions, provided that the vaginal vaccination is given on optimal time points in the cycle.

[Control of methicillin resistant staphylococci at the Sahlgrenska hospital. Successful control program against MRSA outbreak]

In 1998-1999 a strain of methicillin resistant Staphylococcus aureus (MRSA) infected 147 patients in 40 out of 160 ward units at Sahlgrenska University Hospital, Gothenburg. The strain originated from a patient who had been treated in a hospital in Cyprus. In order to control this outbreak a plan of action was decided upon and carried out, including extensive information to the hospital staff, screening for carriers, and establishing a hospital infection control committee. Furthermore, a policy for screening all patients readmitted to the hospital was established in November 1999. This screening could be discontinued on July 1, 2001.

[Infection a dreaded central venous catheter-related complication. A reminder of the significance of good aseptics is justified]

The use of central venous catheters has increased markedly. Large numbers of patients are therefore at risk for catheter-related infections. This paper reviews the literature on prevention of intravascular catheter-related complications. Microbes colonising the catheter hubs and the skin around the insertion site are the source of most of these infections. By simple routines it is possible to reduce the risk for microbial spread from these sites to the bloodstream.

Local and systemic immune responses to rectal administration of recombinant cholera toxin B subunit in humans

The induction of immune responses to rectally administered recombinant cholera toxin B subunit (CTB) in humans was studied. Three immunizations induced high levels of CTB-specific antibody-secreting cells, particular of the immunoglobulin A isotype, in both rectum and peripheral blood. Antitoxin antibody responses in rectal secretions and serum were also found.

Induction and distribution of intestinal immune responses after administration of recombinant cholera toxin B subunit in the ileal pouches of colectomized patients

The induction and dissemination of mucosal immune responses to recombinant cholera toxin B subunit (rCTB) administered into the ileal pouches of patients, who had been colectomized because of ulcerative colitis, was analyzed. Biopsies from the duodenum and ileal pouch were collected, along with peripheral blood and ileostomy fluids. Two immunizations induced strong CTB-specific immunoglobulin A (IgA) antibody-secreting cell (ASC) responses in the duodenum in five of five patients, whereas weaker and less-frequent ASC responses were noted in the ileal pouch. Intestine-derived CTB-specific IgA ASCs were found in peripheral blood in three of the five patients. The vaccination also induced significant IgA antitoxin titer rises in ileostomy fluid in all of the patients. Increased production of gamma interferon in cell cultures from the ileal pouch was found in four of five patients after the vaccination. These results clearly indicate that rCTB administered into the distal ileum is capable of inducing B-cell responses in the "entire" small intestine and that homing of immunocompetent cells occurs preferentially to the duodenum.

Dose-dependent circulating immunoglobulin A antibody-secreting cell and serum antibody responses in Swedish volunteers to an oral inactivated enterotoxigenic Escherichia coli vaccine

The immunogenicity of different preparations of an oral inactivated enterotoxigenic Escherichia coli (ETEC) vaccine was evaluated in Swedish volunteers previously unexposed to ETEC infection. The vaccine preparations consisted of recombinant cholera toxin B subunit (CTB) and various amounts of formalin-killed whole bacteria expressing the most prevalent colonization factor antigens (CFAs). Significant immunoglobulin A (IgA) antibody-secreting cell (ASC) responses against CTB and the various CFA components were seen in a majority of volunteers after two doses of ETEC vaccine independent of the vaccine lot given. The IgA ASC responses against CTB were significantly higher after the second than after the first immunization, whereas the CFA-specific IgA ASC responses were almost comparable after the first and second doses of ETEC vaccine. Two immunizations with one-third of a full dose of CFA-ETEC bacteria induced lower frequencies of IgA ASC responses against all the different CFAs than two full vaccine doses, i.e., 63 versus 80% for CFA/I, 56 versus 70% for CS1, 31 versus 65% for CS2, and 56 versus 75% for CS4. The proportion of vaccinees responding with rises in the titer of serum IgA antibody against the various CFA antigens was also lower after immunization with the reduced dose of CFA-ETEC bacteria. These findings suggest that measurements of circulating IgA ASCs can be used not only for qualitative but also for quantitative assessments of the immunogenicity of individual fimbrial antigens in various preparations of ETEC vaccine.

Enterotoxin-specific immunoglobulin E responses in humans after infection or vaccination with diarrhea-causing enteropathogens

Cholera toxin (CT)-specific antibody responses of the immunoglobulin E (IgE) isotype in the sera of adult patients suffering from infection with either Vibrio cholerae O1, V. cholerae O139, or enterotoxigenic Escherichia coli (ETEC) were analyzed and compared with those in the sera of volunteers immunized with a bivalent B subunit O1/O139 whole-cell cholera vaccine. A significant IgE response to CT was observed in 90% of the patients with V. cholerae O1 infection (18 of 20; P = <0.001) and 95% of the patients with V. cholerae O139 infection (19 of 20; P = <0.001). Similarly, the majority of the patients with ETEC diarrhea (83%; 13 of 15) showed a positive IgE response to CT. Eight of 10 North American volunteers (80%) orally challenged with V. cholerae O1 showed CT-specific IgE responses (P = 0.004). In contrast, Swedish volunteers immunized with the oral cholera vaccine showed no IgE responses to CT (P value not significant). During the study period, total IgE levels in the sera of the diarrheal patients, the North American volunteers, and the Swedish cholera vaccinees alike remained unchanged. However, the total IgE levels in the sera of patients and healthy Bangladeshi controls were on average 89-fold higher than those in the sera of the healthy Swedish volunteers and 34-fold higher than those in the sera of the North American volunteers.

Oral, inactivated, whole cell enterotoxigenic Escherichia coli plus cholera toxin B subunit vaccine: results of the initial evaluation in children. PRIDE Study Group

Two randomized, double-blinded trials assessed the safety and immunogenicity of an oral, killed enterotoxigenic Escherichia coli (ETEC) plus cholera toxin B subunit vaccine in Egyptian children. Two doses of vaccine or E. coli K-12 were given 2 weeks apart to 105 6- to 12-year-olds and 97 2- to 5-year-olds. Safety was monitored for 3 days after each dose. Blood was collected before immunization and 7 days after each dose to measure immune responses. Few children reported postdosing symptoms, with no differences in the frequency of symptoms between treatment groups. Most vaccinees had an IgA antibody-secreting cell response against colonization factor antigen I (100%, 6-12 years; 95%, 2-5 years), coli surface antigen 2 (92%, 6-12 years; 83%, 2-5 years), and coli surface antigen 4 (93%, 6-12 years). Vaccination evoked a >/=4-fold rise in antitoxic IgA and IgG titers in 93% and 81% of children, respectively. In conclusion, the oral ETEC vaccine was safe and immunogenic in 2- to 12-year-old children, justifying further evaluation in infants.

Immune responses in ileostomy fluid and serum after oral cholera vaccination of patients colectomized because of ulcerative colitis

The capacity of an oral inactivated B-subunit-whole-cell cholera vaccine to induce immune responses in patients colectomized due to ulcerative colitis was studied. Two doses of vaccine induced significant mucosal immunoglobulin A (IgA) antibody responses in ileostomy fluid against cholera toxin in 14 of 15 (93%) patients and against whole vibrios in 9 of 15 (60%) cases. The serological responses were lower (but not significantly) than those observed in healthy Swedish volunteers. Increased IgA antitoxin levels were found in ileostomy fluid as late as 2 years after vaccination.

Intestinal immune responses to an inactivated oral enterotoxigenic Escherichia coli vaccine and associated immunoglobulin A responses in blood

An inactivated oral enterotoxigenic Escherichia coli (ETEC) vaccine against ETEC diarrhea was given to 25 adult Swedish volunteers. The vaccine consisted of formalin-killed E. coli bacteria expressing the most common colonization factor antigens (CFAs), i.e., CFA/I, -II, and -IV, and recombinantly produced cholera B subunit (CTB). Immunoglobulin A (IgA) antibody responses in intestinal lavage fluid to CTB and CFAs were determined and compared with corresponding responses in stool extracts and serum as well as with IgA antibody-secreting cell (ASC) responses in peripheral blood. Two doses of vaccine induced significant IgA responses to the different CFAs in lavage fluid in 61 to 87% of the vaccinees and in stool in 38 to 81% of them. The most frequent responses were seen against CFA/I. The magnitudes of the antibody responses against CTB and CFA/I in stool correlated significantly (CTB, P < 0.01; CFA/I, P < 0. 05) with those in intestinal lavage. Intestinal lavage responses against CFAs were best reflected by the ASC responses, with the sensitivity of the ASC assay being 80 to 85%, followed by stool (sensitivity of 50 to 88%) and serum antibody (sensitivity of 7 to 65%) analyses. CTB-specific immune responses were seen in >90% of the vaccinees in all assays.

Kinetics of local and systemic immune responses to an oral cholera vaccine given alone or together with acetylcysteine

The possibility that a mucolytic drug, i.e., acetylcysteine, given orally may enhance the gut mucosal or systemic immune response to an oral B-subunit-whole-cell (B-WC) cholera vaccine was evaluated for 40 adult Swedish volunteers, and the kinetics of the immune responses were monitored for responding volunteers. Two doses of vaccine induced similar frequencies of immunoglobulin A (IgA) and IgG antitoxin responses (80 to 90%) and vibriocidal titer increases (60 to 65%) in serum irrespective of whether the vaccine was given alone or together with 2 g of acetylcysteine. In feces the frequencies of IgA antitoxin (67%) and antibacterial (33 to 40%) antibody responses were also comparable in the two immunization groups. Six months after vaccination, IgA and IgG antitoxin as well as vibriocidal antibody titer increases in serum could still be detected in approximately 80% of initially responding vaccinees. Significantly elevated fecal antitoxin and antibacterial IgA antibody levels were found in, respectively, 50 and 43% of those volunteers who initially had responded to the vaccine. Determination of IgA antibodies in feces does not seem to offer any advantages compared to determination in serum for assessment of immune responses after immunization with inactivated cholera vaccine.

Safety and immunogenicity of an oral, killed enterotoxigenic Escherichia coli-cholera toxin B subunit vaccine in Egyptian adults

Enterotoxigenic Escherichia coli (ETEC) is the leading cause of bacterial diarrhea in young children in developing countries. The safety and immunogenicity of a killed, oral ETEC vaccine consisting of whole cells plus recombinantly produced cholera toxin B subunit (rCTB) was evaluated in Egypt, which is endemic for ETEC diarrhea. Seventy-four healthy Egyptian adults (21-45 years old) were randomized and received two doses of the ETEC/rCTB vaccine (E003) or placebo 2 weeks apart. The frequency of adverse events after either dose did not differ by treatment group, and no severe adverse events were reported. After vaccination, peripheral blood IgA B cell responses to CTB (100%) and to vaccine colonization factor antigens CFA/I (94%), CS4 (100%), CS2 (81%), and CS1 (69%) were significantly higher than response rates for the placebo group. These favorable results in Egyptian adults indicate that the ETEC/rCTB vaccine is a promising candidate for evaluation in younger age groups in this setting.

Safety and immunogenicity of an oral inactivated enterotoxigenic Escherichia coli vaccine

The safety and immunogenicity of two different lots, 001 and 003, of an oral inactivated enterotoxigenic Escherichia coli (ETEC) vaccine consisting of a mixture of formalin-killed whole bacteria expressing the most prevalent colonisation factor antigens, i.e. CFA/I, CFA/II and CFA/IV and recombinantly produced cholera B subunit (rCTB) have been evaluated in Swedish volunteers. Neither of the two vaccine preparations, containing different CFA/II-expressing strains but otherwise identical, gave rise to any significant side-effects. Mucosal immune responses, as reflected in antibody-secreting cell (ASC) responses in peripheral blood, were studied after two doses of vaccine and did not differ significantly for the two vaccine lots. Vaccination induced high levels of CTB-specific IgA ASCs in 100% of the volunteers, and significant IgA ASC responses (9- to 36-fold) were noted in 84% of them against CFA/I, in 87% against CFA/II subcomponents CS1-CS3 and in 91% against CFA/IV subfactors CS4 and/or CS5. The frequencies and magnitudes of CFA IgA ASC responses were similar when giving the vaccine with a 1 or 2 week interval. Results from serological analyses showed that the local IgA responses against CFAs are only infrequently associated with serum antibody titre rises.

Differential expression of tissue-specific adhesion molecules on human circulating antibody-forming cells after systemic, enteric, and nasal immunizations. A molecular basis for the compartmentalization of effector B cell responses

Expression of the adhesion molecules CD44, L-selectin (CD62L), and integrin alpha 4 beta 7 by antibody-secreting cells (ASC) was examined in human volunteers after oral, rectal, intranasal, or systemic immunization with cholera toxin B subunit. Almost all blood ASC, irrespective of immunization route, isotype (IgG and IgA), and immunogen, expressed CD44. On the other hand, marked differences were observed between systemically and intestinally induced ASC with respect to expression of integrin alpha 4 beta 7 and L-selectin, adhesion molecules conferring tissue specificity for mucosal tissues and peripheral lymph nodes, respectively. Thus, most ASC induced at systemic sites expressed L-selectin, whereas only a smaller proportion of ASC expressed alpha 4 beta 7. In contrast, virtually all IgA- and even IgG-ASC detected after peroral and rectal immunizations expressed alpha 4 beta 7, with only a minor fraction of these cells expressing L-selectin. Circulating ASC induced by intranasal immunization displayed a more promiscuous pattern of adhesion molecules, with a large majority of ASC coexpressing L-selectin and alpha 4 beta 7. These results demonstrate that circulating ASC induced by mucosal and systemic immunization express different sets of adhesion molecules. Furthermore, these findings provide for the first time evidence for differential expression of adhesion molecules on circulating ASC originating from different mucosal sites. Collectively, these results may explain the anatomical division of mucosal and systemic immune responses in humans as well as the compartmentalization of mucosal immune responses initiated in the upper vs. the lower aerodigestive tract.

Local intravaginal vaccination of the female genital tract

In a clinical trial the authors tested whether local intravaginal or oral vaccination would stimulate a mucosal immune response in the female genital tract. The whole cell/B subunit (CTB) oral cholera vaccine was used. Two groups of previously unimmunized volunteers were given three doses of vaccine at 2-week intervals: a first group of seven women received oral immunizations and a second group of seven women were immunized locally in the genital tract by mixing the vaccine with a well defined gel, eldexomer, and applying it directly in the fornix of the vagina. The women were given the first vaccination on day 10 of the menstrual cycle. Sampling of peripheral blood and of cervical mucus (CM) using an Aspiglaire syringe was performed immediately prior to the first dose and at 8-10 days following the last immunization. The study showed that while only three of the seven orally immunized women responded with detectable IgA and IgG anti-CTB antibodies in the genital tract, six out of the seven women in the locally vaccinated group responded with genital tract antibodies. The responses were also generally stronger and CM contained higher specific IgA and secretory component containing anti-CTB titres in the locally vaccinated group. Of the orally vaccinated individuals all responded with increases in serum anti-CTB IgG and 4,7 also exhibited specific IgA serum titres. By contrast, only 3/7 in the intravaginal group responded with increases in serum IgG and IgA anti-CTB titers following immunization. The authors conclude that local intravaginal vaccination using a well-defined gel appears to be the route of choice to stimulate immunity in the female genital tract.

Intestinal and systemic immune responses in humans after oral immunization with a bivalent B subunit-O1/O139 whole cell cholera vaccine

There is a need for an effective vaccine that can protect against cholera caused by either Vibrio cholerae O1 or by the new pandemic serotype O139 Bengal. An oral bivalent B subunit-O1/O139 whole cell (B-O1/O139 WC) cholera vaccine has been prepared by adding formalin-killed O139 vibrios to the recently licensed oral recombinant B-O1 WC vaccine. When tested in Swedish volunteers, this B-O1/O139 WC vaccine was found to be safe and immunogenic. Two vaccine doses given 2 weeks apart induced statistically significant, P < 0.05, mucosal IgA antibody responses in intestinal lavage fluid against cholera toxin in all of nine vaccinees and against both O1 and O139 vibrios in seven of nine cases. The intestinal responses were associated with similar high frequencies of intestine-derived antibody-secreting cell responses in peripheral blood to the different antigens. A third dose of vaccine given after 5-6 weeks did not result in any further increased response. All of 12 vaccinees responded with significant IgA and IgG antitoxin responses in serum associated with significant vibriocidal antibody titre rises against O1 vibrios in 10 cases (83%) and against O139 vibrios in eight vaccinees (67%). The frequencies and magnitudes of the serological responses to the B subunit and O1 WC components were similar to those induced by the B-O1 WC vaccine. Thus, the O139 component of the vaccine induced intestinal and systemic antibacterial immune responses in the majority of the vaccinees, and its addition to the vaccine did not interfere with the immunogenicity of the B subunit or O1 WC components.

Immunological memory after immunization with oral cholera B subunit--whole-cell vaccine in Swedish volunteers

The capacity of peroral immunization with either two or three doses of B subunit-whole cell (B-WC) cholera vaccine to induce immunological memory was examined in Swedish volunteers by testing the immune responses to a single dose of B-WC vaccine given 10 months after the initial immunization. Antibody responses in serum and antibody-secreting cell (ASC) responses in peripheral blood were studied, since these responses seem to reflect the gut mucosal IgA immune responses after oral immunization with B-WC vaccine. Previously immunized volunteers responded to a single dose of B-WC vaccine more frequently and with higher levels of IgA and IgG antitoxin antibodies as well as vibriocidal antibodies in serum than did previously unvaccinated controls. The IgA-ASC responses to cholera toxin B subunit were also higher in primed volunteers than in controls. Two doses of B-WC vaccine were as effective as three doses in inducing immunological memory for cholera immunity. A new B-WC cholera vaccine based on recombinant B subunit had the same capacity as the first generation of B-WC vaccine to induce immunological memory for cholera antitoxin immunity.

Evaluation of different immunization schedules for oral cholera B subunit-whole cell vaccine in Swedish volunteers

Different immunization schedules for oral B subunit-whole cell (B-WC) cholera vaccine were evaluated in Swedish volunteers to obtain information for recommendations of vaccine use in non-endemic areas. Two peroral doses of B-WC vaccine were as effective as three doses in inducing IgA and IgG antitoxin as well as vibriocidal antibody responses in serum. Administration of two vaccine doses either at 7, 14 or 28-42 day intervals resulted in comparable antitoxin responses in serum, whereas a 3-day immunization interval resulted in significantly lower titre increases. Vibriocidal antibody responses were comparable after the different time intervals tested (3-42 days). The B-WC vaccine can be effectively administered together with a cheap, commercially available sodium bicarbonate powder dissolved in water to protect the vaccine from gastric acid.

Empiric treatment of acute diarrheal disease with norfloxacin. A randomized, placebo-controlled study. Swedish Study Group

OBJECTIVE

To evaluate the clinical and microbiologic efficacy and safety of norfloxacin for acute diarrhea.

DESIGN

Double-blind, placebo-controlled, randomized clinical multicenter trial.

SETTING

Six departments of infectious disease.

PARTICIPANTS

Patients 12 years of age or older with a history of acute diarrhea lasting 5 or fewer days. Eighty-five percent of patients (511/598) were evaluable for efficacy. Of these evaluable patients, 70% had traveled abroad within the previous 6 weeks.

INTERVENTIONS

Patients received either norfloxacin, 400 mg, or placebo twice daily for 5 days.

MEASUREMENTS

Enteric pathogens were isolated in 51% of the evaluable patients: Campylobacter species in 29%, Salmonella species in 16%, Shigella species in 3.5%, and other pathogens in 2.6%.

RESULTS

Norfloxacin had a favorable overall effect compared with placebo (cure rate, 63% compared with 51%; P = 0.003). There were statistically favorable effects in culture-positive patients, patients with salmonellosis, and severely ill patients but not in culture-negative patients or patients with campylobacteriosis or shigellosis. A significant difference was noted between norfloxacin and placebo in median time to cure among all evaluable patients (3 compared with 4 days, P = 0.02) and in patients with campylobacteriosis (3 compared with 5 days, P = 0.05) but not in patients. Culture-positive, but not culture-negative patients, in the norfloxacin group had significantly fewer loose stools per day compared with patients in the placebo group from day 2 onward (P less than or equal to 0.01). Norfloxacin was significantly less effective than placebo in eliminating Salmonella species on days 12 to 17 (18% compared with 49%, P = 0.006), whereas the opposite was true for Campylobacter species (70% compared with 50%, P = 0.03). In six of nine patients tested, norfloxacin-resistant Campylobacter species (MIC, greater than or equal to 32 micrograms/mL) appeared after norfloxacin treatment.

CONCLUSION

Empiric treatment reduced the intensity and, to some extent, the duration of symptoms of acute diarrhea. The effect was restricted to patients who had bacterial enteropathogens or who were severely ill. The clinical usefulness of this treatment is limited by the fact that norfloxacin seems to delay the elimination of salmonella and to induce resistance in campylobacter.

Safety and immunogenicity of an oral recombinant cholera B subunit-whole cell vaccine in Swedish volunteers

The safety and immunogenicity of a 'new' oral B subunit-whole cell (B-WC) cholera vaccine based on recombinantly produced B subunit was evaluated in Swedish volunteers. The recombinant B-WC vaccine was comparable to the 'old' type of B-WC vaccine in inducing IgA and IgG antitoxin antibody responses as well as vibriocidal antibody responses in serum, which are known to be good serological correlates of the gut mucosal IgA antitoxic and antibacterial immune responses after oral immunization with B-WC vaccine. Neither of the two B-WC vaccines was associated with any significant side-effects. The results indicate that the more easily and cheaply produced recombinant B subunit can replace the 'old' type of B subunit isolated from cholera toxin for use in the oral B-WC cholera vaccine.

An oral B subunit: whole cell vaccine against cholera

During the last decade there has been a rapid progress in the development of new, much improved vaccines against cholera. These vaccines, which are given orally to stimulate the gut mucosal immune system, are based on either a combination of purified cholera toxin B (binding) subunit and killed cholera vibrios of Inaba and Ogawa serotypes and El Tor and classical biotypes (B subunit-whole cell vaccine, B-WC) or on a live attenuated mutant strain of Vibrio cholerae producing the B subunit (CVD 103-HgR). The safety of the oral B-WC cholera vaccine and the immunogenicity and protective efficacy of this vaccine against both cholera and diarrhoea caused by enterotoxigenic Escherichia coli have been extensively documented, e.g. in a large randomized, placebo-controlled field trial in 90,000 persons living in a cholera endemic area. The potential for inexpensive large-scale manufacturing of the B-WC vaccine has recently been much facilitated by the introduction of recombinant DNA technology for production of the B subunit component. This now gives promise that this vaccine could become a useful, cost-effective tool in future strategies to control cholera both in endemic situations and in relation to acute epidemic outbreaks.

Enterotoxin-producing bacteria isolated from Swedish travellers with diarrhoea

The isolation rate of bacterial enteropathogens of different species, particularly enterotoxin-producing Gram-negative bacteria, was determined in stool specimens from Swedish travellers with diarrhoea. Overall, bacterial enteropathogens were identified in 101 (47%) of the 217 travellers on their return home. The most common isolates were enterotoxin-producing bacteria (20%), Salmonellae (18%) and Campylobacter (8%), whereas Shigellae (3%) and Yersinia (0.5%) were rarely identified. Mixed infections were only found in 8 (4%) of the stool specimens. Enterotoxigenic bacteria of Escherichia coli (ETEC), Klebsiella, Morganella, Citrobacter, Pseudomonas and EF-group 10 species were identified. ETEC accounted for 37/43 (86%) enterotoxin-producing strains, and among them 54% produced heat-stable enterotoxin (ST) alone, 16% heat-labile enterotoxin (LT) alone and 30% both LT and ST. Four of the enterotoxin-producing non-E. coli strains produced ST and 2 produced LT alone. The isolation rate of enterotoxin-producing bacteria was somewhat higher in travellers visiting Africa, Asia and Latin America (24%) than in those travelling to Southern Europe (14%). Salmonellae, on the other hand, were identified in stools significantly more often after travel to Southern Europe (26%) than to various subtropical and tropical areas (12.5%).

Infection with bacterial enteropathogens in Swedish travellers to South-East Asia--a prospective study

Infection with potential bacterial enteropathogens was studied prospectively in 94 Swedish travellers. Three faecal samples were collected, regardless of diarrhoeal symptoms, after each of three 1-week stays in Singapore, Hong Kong and Japan. The specimens were analyzed for salmonella, shigella, yersinia, campylobacter and different enterotoxin-producing bacteria. A potential enteropathogen was identified in 30% (28/94) of the participants, i.e. in 26% of the healthy and in 39% of the travellers with diarrhoea. The most common isolates were enterotoxigenic bacteria of different species (14%), salmonella (11%) and campylobacter (7%). By performing enterotoxin-tests on six different colonies from the primary culture of each specimen enterotoxigenic Escherichia coli (ETEC) as well as enterotoxin-producing Klebsiella sp., Citrobacter sp. and Morganella morganii were identified. The latter strains were as prevalent as ETEC. In the 33 participants with diarrhoea enterotoxigenic bacteria (18%) and campylobacter (18%) were the most common isolates. Campylobacter-infected travellers developed symptomatic disease (6/7) significantly (P less than 0.02) more often than those infected with salmonella (3/10) or enterotoxigenic bacteria (6/13; 2 ETEC, 4 other species).

Estimation of symptomatic and asymptomatic Salmonella infections

Since the surveillance of salmonellosis in Sweden is primarily passive, it can be assumed that most of the asymptomatic salmonella infections are never identified. We here report the proportion of asymptomatic and symptomatic salmonella infections in Swedish travellers to different geographic areas as well as in "contacts" to index cases with salmonellosis. In the 346 travellers studied Salmonellae were isolated equally often among those who remained healthy (10/216; 4.6%) as in those with intestinal symptoms (7/130; 5.4%). Similarly, most of the salmonella-infected "contacts" to index cases (11/15; 73%) had an asymptomatic infection. No difference in the mean duration of excreting Salmonella in the stool was found between carriers with symptomatic and asymptomatic infection. The literature concerning transmission of nontyphi Salmonellae from carriers was reviewed. Since person to person transmission is rarely noted, screening for carriers may be limited to food handlers and hospital personnel taking care of patients susceptible to low infective doses of Salmonella. Similarly, follow-up faecal cultures in individuals with notified salmonella infection may be restricted to these groups.

Serum antibody responses to bacterial enteropathogens in Swedish travelers to south-east Asia

The possibility that serological analysis may be more sensitive than bacteriological examinations of stool samples to detect enteric infections was evaluated in 80 Swedish travellers to South-East Asia. Serum and faecal specimens were collected before, during and after their travel. Serological analyses of pre-travel and any later serum specimen identified infection with enterotoxinogenic Escherichia coli (ETEC), Salmonella or Campylobacter jejuni in 28% of the travellers. The seroconversion rate was 72% in travellers excreting the homologous pathogen in their stool; all symptomatic cases and half of those who had an asymptomatic infection seroconverted. Bacteriological examinations of stool samples collected repeatedly during travel identified an enteropathogen in 20% of the travellers. However, the isolation rate decreased to 11%, when only a single routine faecal specimen was examined. Our findings suggest that serological analyses of pre- and post-travel specimens are sufficiently specific and may be at least as sensitive as conventional bacteriology to identify infections with bacterial enteropathogens in travellers. However, reliable serodiagnosis requires collection of pre-travel sera and might therefore only be useful in prospective studies of travellers' diarrhoea.

Short-term self-treatment of travellers' diarrhoea with norfloxacin: a placebo-controlled study

In a randomized, double blind, placebo-controlled, multicentre trial, 447 travellers to Africa, Asia or Latin America started three days treatment with norfloxacin 400 mg bd or placebo within 24 h after the onset of travellers' diarrhoea. One hundred and four subjects developed diarrhoea and of those 94 (46 in the norfloxacin group and 48 in the placebo group) could be analysed for efficacy. By the last treatment day, 34 patients in the norfloxacin and 18 in the placebo group were cured (P = 0.0001), four and three improved and five and 19, respectively, were failures. Recurrences were seen in three patients on norfloxacin and eight on placebo. The mean time to cure was 3.2 days in the norfloxacin group and 4.4 days in the placebo group (P less than 0.005). The number of loose stools was significantly lower in the norfloxacin group. Nine adverse events were reported; seven in the placebo and two in the norfloxacin group. Pre- and post-travel faecal samples were studied in 19 patients treated with norfloxacin, 21 treated with placebo and 21 untreated subjects without diarrhoea. In treated subjects, increased frequencies of Escherichia coli resistant to ampicillin, co-trimoxazole, doxycycline and chloramphenicol were found in both groups, though more frequently in the placebo one. No subject had norfloxacin resistant Esch. coli pre- and post-travel.

IgG and IgA subclass distribution of antitoxin antibody responses after oral cholera vaccination or cholera disease

The immunoglobulin subclass distribution of cholera antitoxin antibody responses in serum was studied in Swedish volunteers after different routes of immunization with a cholera B subunit-whole cell vaccine (B + WCV) and in Bangladeshi patients convalescing from cholera disease. Both oral and parenteral immunization induced antitoxin antibodies of all the different IgG subclasses (IgG1, IgG2, IgG3 and IgG4) whilst the IgA antibodies were restricted to the IgA1 subclass. A single oral dose of B + WCV induced proportionally higher levels of IgG4 antitoxin in previously cholera-immunized volunteers than in a matched group who had not been cholera-vaccinated before, suggesting that repeated immunization preferentially stimulate formation of IgG4 antibodies. The IgG and IgA subclass distribution of antitoxin antibodies in orally vaccinated Swedes closely resembled that in Bangladeshi cholera patients.

Enterotoxigenic Escherichia coli diarrhea in an endemic area prepares the intestine for an anamnestic immunoglobulin A antitoxin response to oral cholera B subunit vaccination

We examined whether infection with enterotoxigenic Escherichia coli (ETEC) producing the heat-labile enterotoxin (LT) can prime the gut immune system to respond more efficiently to the immunologically related cholera B subunit component of a recently developed oral B subunit-whole-cell cholera vaccine (B-WCV). Nine Bangladeshi adults who had been hospitalized for watery diarrhea caused by LT-producing ETEC were given a single oral immunization with B-WCV on day 28 after hospital admission. The vaccine preparation used was adjusted to contain a lower-than-usual dose of B subunit, which had been found in previous studies to elicit a significant gut mucosal immunoglobulin A antitoxin response mainly in individuals with previous toxin-specific priming of their gut immune system. For comparison, nine patients convalescing from severe cholera disease and eight healthy subjects with no recent history of either cholera or ETEC infection were given the same oral vaccination with B-WCV. Vaccination in the ETEC convalescents induced an immunoglobulin A antitoxin response in intestinal lavage fluid which was comparable with that in the vaccinated cholera convalescents and superior to that in the vaccinated, previously uninfected controls. By contrast, only the cholera patients responded with anamnestic-type anti-cholera lipopolysaccharide antibody titer rises in the intestine after vaccination. These data support the specificity of the anamnestic anti-cholera toxin response in the ETEC patients after vaccination with cholera B-WCV.

A prospective study of serum antibody responses to enterotoxinogenic Escherichia coli in Swedish travellers

Serological responses to relevant enterotoxinogenic Escherichia coli (ETEC) antigens were studied in 85 Swedish travellers to subtropical and tropical areas. Serum samples were collected from the travellers before and then after 3-5 weeks, i.e. within a week after return to Sweden, when a faecal specimen was also taken. 40% of the participants had traveller's diarrhoea during their visit abroad, while 21% reported "loose stools" and 39% had no such problems. ETEC was rarely isolated from the stool of any of the travellers on their return to Sweden (6%). Salmonellae, Shigellae or Campylobacter jejuni were isolated from 13 (15%) of the travellers, 12 of whom were healthy when the specimens were collected and 4 of whom had been healthy during travel as well. Significant serum antibody responses to E. coli heat-labile enterotoxin (LT) and colonization factor antigens CFA I or II were seen in 33% and 20% of the travellers, respectively. Anti-LT responses were comparable in participants with traveller's diarrhoea or "loose stools" and in the healthy ones, whereas anti-CFA responses were more frequent in those with symptomatic infections. Of 34 Swedes in a non-travelling control group none responded to LT and one to CFA I or CFA II.

Saliva, breast milk, and serum antibody responses as indirect measures of intestinal immunity after oral cholera vaccination or natural disease

The possibility that antibody responses in serum, saliva, or breast milk samples to oral vaccines or enteric infections may reflect the intestinal immune response was evaluated in Bangladeshi volunteers orally immunized with a cholera B subunit-whole-cell vaccine (B + WCV) and in patients convalescing from enterotoxin-induced diarrheal disease. Two peroral doses of B + WCV induced antitoxin and antibacterial antibody responses in the intestinal fluids of 76 and 92%, respectively, of the volunteers and in serum samples in 90 and 69% of those tested. These responses were comparable to those obtained after cholera or enterotoxigenic Escherichia coli disease. Whereas immunoglobulin A (IgA) antitoxin titer increases in saliva (44%) and breast milk (29%) specimens after vaccination were less frequent than in intestinal fluid (76%), antitoxin responses in saliva and breast milk occurred in 80 to 90% of the patients after disease. Also, antilipopolysaccharide (anti-LPS) titer increases in extraintestinal body fluids were found more frequently after disease than after vaccination. A comparison of the frequency and magnitude of antibody response in different body fluids with those in intestinal lavage fluid revealed no extraintestinal antibody that directly reflected the intestinal immunity. However, comparison of vibriocidal and IgG antitoxin antibodies in serum specimens with antitoxin and anti-LPS IgA responses in intestinal fluids after the vaccination of volunteers showed a sensitivity of 70 to 90% and a predictive accuracy of about 80% for the serum analyses reflecting the intestinal immune responses. Furthermore, antitoxin and anti-LPS antibody responses in saliva and breast milk samples seemed to be useful proxy indicators of a gut mucosal response of these antibodies after enterotoxin-induced diarrheal disease showing sensitivity vales of 70 to 90% and predictive accuracy vales of 70 to 100%.

Mucosal antitoxic and antibacterial immunity after cholera disease and after immunization with a combined B subunit-whole cell vaccine

Mucosal and systemic immune responses to a new oral cholera vaccine, consisting of the B subunit plus killed vibrios, were studied in Bangladeshi volunteers and compared with those to clinical cholera. A single peroral dose of vaccine induced a local IgA antitoxin response in intestinal-lavage fluid of seven of eight vaccinees; the response closely mimicked that of patients convalescing from cholera, and evidence of the induction of local immunologic memory was found as well. Two peroral doses were needed for stimulation of an intestinal IgA immune response to the lipopolysaccharide of Vibrio cholerae that was comparable to the response obtained after clinical cholera. This response to peroral immunization was considerably stronger than that to parenteral vaccination, although the intramuscular route gave rise to the strongest IgG antitoxin and antilipolysaccharide responses in serum. The results suggest that B subunit-whole cell vaccine, when given in at least two oral doses, may be a good candidate for use in cholera prophylaxis.

Gut mucosal, salivary and serum antitoxic and antibacterial antibody responses in Swedes after oral immunization with B subunit-whole cell cholera vaccine

Gut mucosal, salivary and serum antibody responses to a new oral cholera vaccine, consisting of B subunit and whole cell vaccine (WCV), were studied in Swedish volunteers. A single immunization with a 0.5 mg dose of B subunit together with WCV (5 X 10(10) killed cholera vibrios) induced a local intestinal immunoglobulin A (IgA) antitoxin response in 4/6 (67%) vaccine recipients as evident from specific antibody titre rises in intestinal lavage fluid. A second administration of vaccine did not further enhance the intestinal immune response beyond the peak level induced by the initial immunization. Different doses of B subunit (2.5 and 0.5 mg) given together with 5 X 10(10) killed vibrios (WCV) induced antitoxin antibody responses in serum in about the same frequency, 10/13 (77%) responders versus 13/14 (93%), as well as in saliva, 7/13 (54%) versus 9/14 (64%), and a single immunization was almost as efficient as two vaccine administrations. Single or repeated oral vaccination only irregularly resulted in modest antibacterial titre rises in serum (9/27 = 33%) or saliva (12/27 = 44%), but stimulated a significant mucosal antibacterial response in intestine of 5/6 (83%) examined volunteers.

Phlebitis induced by parenteral treatment with flucloxacillin and cloxacillin: a double-blind study

Two studies were performed on a total of 54 patients with staphylococcal infections. Study I compares with phlebitogenic properties of flucloxacillin after intravenous infusions when either saline or sterile water was used as a solvent. No difference was observed between the two solvents, and the frequency of phlebitis for the total material without respect to solvents was 5% after 1 day of treatment and 13% after 2 days. Study II was a double-blind comparison of phlebitis caused by intravenous infusions of either flucloxacillin or cloxacillin. The frequencies of phlebitis were found to be 18 and 13%, respectively. After 2 days of treatment the frequency of phlebitis increased dramatically for both drugs. All infusions were given through a plastic cannula of 5-cm length and 1.2-mm diameter.