Acquisition of flavour preferences in pigs through interactions with conspecifics that had previously consumed flavoured protein solutions

It is known that pigs can acquire flavour preferences by brief social interactions with conspecifics that previously consumed a flavoured solid feed. However, there is no information about whether a flavoured solution could support flavour preferences through social transmission. Ninety-six pigs (49 days old) were housed in 12 pens (8 pigs/pen). Four animals per pen were randomly selected to act as observers and four as demonstrators. Demonstrator animals were temporarily moved to an empty pen where a protein solution was offered (porcine digestive peptides (PDPs), 4% weight/volume) with the addition of 0.075% aniseed (six pens) or garlic (six pens) powdered artificial flavours for 30 min. Afterwards, demonstrators were returned to interact with observer animals for 30 min. A choice test (30 min) between aniseed and garlic PDP was performed for each observer group after the interaction. Observers showed a higher intake of solutions previously consumed by their demonstrator conspecifics (648 v. 468 ml; SEM 61.36, P < 0.05). As with flavoured solid feeds, protein solutions containing artificial flavours can create preferences in pigs for those flavours through social transmission from conspecifics.

Expression of host defense peptides in the intestine of Eimeria-challenged chickens

Avian coccidiosis is caused by the intracellular protozoan Eimeria, which produces intestinal lesions leading to weight gain depression. Current control methods include vaccination and anticoccidial drugs. An alternative approach involves modulating the immune system. The objective of this study was to profile the expression of host defense peptides such as avian beta-defensins (AvBDs) and liver expressed antimicrobial peptide 2 (LEAP2), which are part of the innate immune system. The mRNA expression of AvBD family members 1, 6, 8, 10, 11, 12, and 13 and LEAP2 was examined in chickens challenged with either E. acervulina, E. maxima, or E. tenella. The duodenum, jejunum, ileum, and ceca were collected 7 d post challenge. In study 1, E. acervulina challenge resulted in down-regulation of AvBD1, AvBD6, AvBD10, AvBD11, AvBD12, and AvBD13 in the duodenum. E. maxima challenge caused down-regulation of AvBD6, AvBD10, and AvBD11 in the duodenum, down-regulation of AvBD10 in the jejunum, but up-regulation of AvBD8 and AvBD13 in the ceca. E. tenella challenge showed no change in AvBD expression in any tissue. In study 2, which involved challenge with only E. maxima, there was down-regulation of AvBD1 in the ileum, AvBD11 in the jejunum and ileum, and LEAP2 in all 3 segments of the small intestine. The expression of LEAP2 was further examined by in situ hybridization in the jejunum of chickens from study 2. LEAP2 mRNA was expressed similarly in the enterocytes lining the villi, but not in the crypts of control and Eimeria challenged chickens. The lengths of the villi in the Eimeria challenged chickens were less than those in the control chickens, which may in part account for the observed down-regulation of LEAP2 mRNA quantified by PCR. Overall, the AvBD response to Eimeria challenge was not consistent; whereas LEAP2 was consistently down-regulated, which suggests that LEAP2 plays an important role in modulating an Eimeria infection.

Avoidance but not aversion following sensory preconditioning with flavors: a challenge to stimulus substitution

After two neutral stimuli have been paired (AB), directly conditioning a response to one of them (A) will also be reflected in a change in responding to the other (B). Standard accounts of this sensory preconditioning effect assume that it is mediated by a memory involving the stimulus that was directly conditioned (i.e., A). The reliance on this shared pathway implies that sensory preconditioning (involving B) and direct conditioning (involving A) should support qualitatively similar patterns of responding. In three experiments, directly pairing A with lithium chloride (LiCl) delivery resulted in both a reduction in consumption of A (i.e., avoidance) and a reduction in the size of licking clusters it elicits (i.e., aversion). In contrast, the sensory preconditioning effect resulted in a reduction in the consumption of B but no change in the nature of the licking response that it elicited; and a similar dissociation was observed after trace conditioning. These dissociations involving direct conditioning and sensory preconditioning, observed over a range of flavor concentrations and different doses of LiCl, undermine standard accounts of sensory preconditioning that are based on the assumption of stimulus substitution.

Re-assessing causal accounts of learnt behavior in rats

Rats received either a common-cause (i.e., A→B, A→food) or a causal-chain training scenario (i.e., B→A, A→food) before their tendency to approach the food magazine during the presentation of B was assessed as a function of whether it was preceded by a potential alternative cause. Causal model theory predicts that the influence of an alternative cause should be restricted to the common-cause scenario. In Experiment 1, responding to B was reduced when it occurred after pressing a novel lever during the test phase. This effect was not influenced by the type of training scenario. In Experiment 2, rats were familiarized with the lever prior to test by training it as a potential cause of B. After this treatment, the lever now failed to influence test responding to B. In Experiment 3, rats given common-cause training responded more to B when it followed a cue that had previously been trained as a predictor of B, than when it followed another stimulus. This effect was not apparent in rats that received causal-chain training. This pattern of results is the opposite of that predicted by causal model theory. Thus, in three experiments, the presence of an alternative cause failed to influence test responding in manner consistent with causal model theory. These results undermine the application of causal model theory to rats, but are consistent with associative analyses.

"Causal reasoning" in rats: a reappraisal

It has recently been argued that rats engage in causal reasoning and they do so in a way that is consistent with Bayes net theories (Blaisdell, Sawa, Leising & Waldmann, 2006). This argument was based upon the finding that the tendency of cues to elicit approach to a food-well was reduced when their presentation was contingent on lever pressing. There is, however, an alternative interpretation of the critical experimental findings that is based on the simple principle of response competition: wherein lever pressing interferes with the tendency to approach the food well. Here the authors replicated Experiments 1 and 2a of Blaisdell et al. (2006) and found reciprocal patterns of lever pressing and food well approach during the critical cues. These results lend direct support for an interpretation in terms of response competition while providing evidence contrary to Bayes net theories, and are readily interpreted within the theoretical framework provided by traditional associative learning theory.

Inhibitory associations contribute to perceptual learning in humans

Perceptual learning in humans was examined in 2 experiments. In Experiment 1, participants received intermixed exposure to 2 similar compounds (AX, BX, AX, BX, . . .) and blocked exposure to a 2nd pair of similar compounds (CY, CY, . . . , DY, DY, . . .). Aversions established to AX and CY generalized less to BX than to DY. In Experiment 2, 1 pair of compounds was presented in a forward order (i.e., AX3BX), whereas the 2nd pair of compounds was presented in a backward order (i.e., DY-->CY). Aversions established to AX and CY generalized less to BX than to DY. These results indicate that inhibitory associations contribute to perceptual learning in humans and thereby establish a fundamental similarity between the mechanisms that underlie perceptual learning in humans and rats.

Reinforcer devaluation in palatability-based learned flavor preferences

Rats exposed to simultaneous compounds of 1 neutral flavor with dilute (2%) sucrose and a 2nd flavor with dilute (2%) maltodextrin subsequently consumed both flavors in preference to a 3rd flavor that was never paired with a palatable taste. Brief training exposure under ad lib food and water minimized the post-ingestive effects of nutrients, emphasizing the contribution of palatability to these preferences. Devaluation of sucrose or maltodextrin by pairing with illness (Experiment 1) or sensory-specific satiety (Experiment 2) selectively reduced the preference for the flavor previously paired with the devalued reinforcer. Such reinforcer-specific devaluation effects suggest that palatability-based learned flavor preferences are under-pinned by a Pavlovian process whereby the cue flavor is associated with the taste of the concurrently consumed palatable reinforcer.

Characterization of a blood activated chitinolytic system in the midgut of the sand fly vectors Lutzomyia longipalpis and Phlebotomus papatasi

We characterized a cDNA from Phlebotomus papatasi, PpChit1, which encodes a midgut specific chitinase and show the presence of a functional, blood-induced chitinolytic system in sand flies. PpChit1 is detected only in the midgut and is regulated by blood feeding. A recombinant protein (rPpChit1) produced in HEK 293-F cells exhibited a similar activity profile to that found in the native protein against several specific substrates, including an oligomeric glycol chitin and synthetic 4-methyl-umbelliferone labelled substrates. Western blotting showed that the native protein is recognized by mouse polyclonal antibodies against rPpChit1. Additionally, the rPpChit1 and the native chitinase displayed similar retention times in a HPLC size fractionation column. When added to rPpChit1 or to midgut lysates, PpChit1 sera reduced chitinolytic activity by 65-70%.

Perceptual learning in humans: roles of preexposure schedule, feedback, and discrimination assay

In three experiments, humans received preexposure to two compound flavours (AX and BX: saline-lemon and sucrose-lemon) that were presented either in an intermixed (e.g., AX, BX,...BX, AX,...) or a blocked (e.g., AX, AX,...BX, BX...) fashion. Subsequently, AX was paired with an unpleasant bitter taste, and the discriminability of AX and BX was assessed using the accuracy of same/different judgements and by the extent to which any learned dislike of AX generalized to BX. When participants received feedback about the accuracy of their same/different judgements during preexposure those given intermixed preexposure were more accurate in making these judgements during the test than those given blocked preexposure (Experiments 1 and 2A), however, there was no evidence of any learned dislike in these experiments. In Experiment 2B, in which participants did not receive feedback about the accuracy of their judgements, there was no effect of the preexposure regime on same/different judgements, but there was a learned dislike of AX, and this generalized less to BX in participants given intermixed than in those given blocked preexposure. The beneficial effects of intermixed preexposure are consistent with results from other species (chicks and rats), but the differences created by the presence or absence of feedback place constraints on the analysis of these effects.

Learning about cues in their absence: evidence from flavour preferences and aversions

A simple behavioural task may involve the presentation of two or more stimuli. Any learning that takes place in such a situation may be analysed in terms of the formation of an association between the central representations of those stimuli. Presumably performance based on this learning can occur because presentation of one stimulus will then activate the representations of other stimuli that were previously presented with it. To examine the role that these representations play in learning in and of themselves requires that the stimuli themselves are absent. A review of a number of flavour preference and aversion studies indicates that an associatively activated stimulus representation can support learning that is both similar to and the opposite of that maintained by the presentation of the stimulus itself. Which occurs is dependent upon the nature of the reinforcer and the temporal relationships between the training events. Although this pattern of results appears suggestive of separate learning rules, a reanalysis raises the possibility of an explanation in terms of a single associative system.

Alternating exposure to two compound flavors creates inhibitory associations between their unique features

Rats were exposed to two compound solutions, saline-lemon and sucrose-lemon. In Group ALT, trials with one solution alternated with trials with the other. Group BLK received all trials with one solution before any trials with the other. Previous retardation tests had implied that only alternating exposure would establish sucrose as an inhibitor of saline. To provide a complementary summation test for this inhibition, in Experiment 1, all the animals received pairings of peppermint and saline and were tested for consumption of peppermint-sucrose under sodium depletion. Consumption was increased by sodium depletion only in Group BLK. In Experiment 2, a retardation test was used to show that presentation of saline-lemon before sucrose-lemon on each exposure day would establish sucrose as an inhibitor of saline. Neither exposure to sucrose-lemon before saline-lemon nor alternating exposure to sucrose and saline alone had the same effect. These results provide support for an associative theory of perceptual learning that suggests that exposure to complex stimuli aids later discrimination partially as a result of establishing inhibitory associations between their unique elements.

Evidence for inhibitory associations between the unique elements of two compound flavours

In each of two experiments, rats were pre-exposed to two flavoured solutions, saline-lemon and sucrose-lemon. For group ALT, trials with one solution alternated with trials with the other. Group BLK received all trials with one solution in a block, before any trials with the other. An associative theory suggests that the alternating, but not the blocked, schedule would establish an inhibitory association between sucrose and saline. To provide a retardation test of this inhibition, some animals in each group were then given a single pairing of saline and sucrose, experienced sodium depletion, and were finally tested for their consumption of sucrose. Sodium depletion increased consumption of sucrose more in group BLK than in group ALT. In groups given no saline-sucrose pairing, sodium depletion had only a small effect on sucrose consumption, which was the same in both groups. After multiple pairings of saline and sucrose, sodium depletion had an equally large effect on sucrose consumption in both ALT and BLK groups. These results imply that alternating pre-exposure to two compound solutions does establish an inhibitory association between their unique elements, and thus provide support for an associative theory of perceptual learning.

Mediated conditioning and retrospective revaluation with LiCl then flavour pairings

It is becoming accepted that the associative strength of a cue can change in its absence, despite this being difficult to explain using existing theories of Pavlovian conditioning. To investigate the influence of timing on learning about the representation of an absent cue, lithium chloride (LiCl) or a flavour previously paired with LiCl was presented in a distinctive context that had previously been paired with a neutral target flavour. The former treatment produced an aversion to the target flavour whether the LiCl was presented 10 min before, or immediately after, exposure to the context. However, presenting the flavour associate of LiCl created an aversion to the target flavour only if it had been presented 10 min after LiCl during initial training. This pattern of results cannot be explained in the terms of a simple timing account, and it is proposed that an explanation will require different associative rules operating in simultaneous and successive training schedules.

A unique surface membrane anchored purine-salvage enzyme is conserved among a group of primitive eukaryotic human pathogens

Previously, we isolated and characterized the gene encoding the 3'-Nucleotidase/Nuclease (Ld3'NT/NU) from the human pathogen, Leishmania donovani. This unique cell surface enzyme has been shown to be involved in the salvage of host-derived purines, which are essential for the survival of this important protozoan parasite. In this report, we assessed whether the 3'-Nucleotidase/Nuclease was conserved amongst other pathogenic Leishmania and related trypanosomatid parasites. Results of pulsed field gel electrophoresis and Southern blotting showed that a Ld3'NT/NU gene homolog was present in each of the visceral and cutaneous Leishmania species tested (i.e. isolates of L. donovani, L. infantum, L. tropica, L. major and L. mexicana, respectively). Further, results of colorimetric assays using 3'-adenosine monophosphate as substrate demonstrated that each of these organisms also expressed significant levels of 3'-nucleotidase enzyme activity. In addition, we showed that a Ld3'NT/NU gene homolog was expressed in each of these Leishmania species as a > 40 kDa 3'-nucleotidase enzyme activity. A Ld3'NT/NU gene homolog was also identified in two Crithidia species (C. fasciculata and C. luciliae) and Leptomonas seymouri but was only marginally detectable in Trypanosoma brucei, Trypanosoma cruzi and Phytomonas serpens. Cumulatively, results of this study showed that an Ld3'NT/NU homolog was conserved amongst pathogenic Leishmania sp. which suggests that this enzyme must play an critical role in purine salvage for all members of this group of human pathogens.

Invasive group B streptococcal disease in Maryland nursing home residents

Between 1991 and 1995, among 999 nonpregnant adult Maryland residents with group B Streptococcus (GBS) isolated from a normally sterile site, 84 resided in nursing homes (NHs). The age-adjusted annual incidence of GBS infection (per 100,000 population) among those > or = 65 years old was 72.3 for NH residents and 17.5 for community residents (relative risk, 4.1; P < 0.001). Thirty-four case patients resided in 11 NHs with > or = 2 cases; 1 NH had 8 case patients within 22 months. Six of 8 case patients from 3 NHs had serotype V GBS. Molecular subtyping of several isolates identified 2 case patients in 1 NH with identical subtype patterns. NH residents have a markedly higher incidence of invasive GBS than do community residents > or = 65 years old and may serve as a target group for immunization when GBS vaccines become available. Further evaluation of intra-NH transmission of GBS is warranted.

Secretory and endocytic pathways converge in a dynamic endosomal system in a primitive protozoan

Leishmania are a group of primitive eukaryotic trypanosomatid protozoa that are apically polarized with a flagellum at their anterior end. Surrounding the base of the flagellum is the flagellar reservoir that constitutes the site for endocytosis and exocytosis in these organisms. In the present study, we define a novel multivesicular tubular compartment involved in the intracellular trafficking of macromolecules in Leishmania. This dynamic structure appears to subtend the flagellar reservoir and extends towards the posterior end of the cell. Functional domains of several surface-expressed proteins, such as the gp63 glycosyl phosphatidyl inositol anchor and the 3'nucleotidase/nuclease transmembrane domain were fused to green fluorescent protein. These chimeric proteins were found to traffic through the secretory pathway and, while reaching their intended destinations, also accumulated within the intracellular tubular compartment. Using various compounds that are efficient fluid-phase markers used to track endocytosis in higher eukaryotes, we showed that this tubular compartment constitutes an important station in the endocytic pathway of these cells. Based on our functional observations of its role in the trafficking of expressed proteins and endocytosed markers, this compartment appears to have properties similar to endosomes of higher eukaryotes.

Molecular characterization of a hyperinducible, surface membrane-anchored, class I nuclease of a trypanosomatid parasite

The 3'-nucleotidase/nuclease (3'-NT/NU) is a surface enzyme unique to trypanosomatid parasites. These organisms lack the pathway for de novo purine biosynthesis and thus are entirely dependent upon their hosts to supply this nutrient for their survival, growth, and multiplication. The 3'-NT/NU is involved in the salvage of preformed purines via the hydrolysis of either 3'-nucleotides or nucleic acids. In Crithidia luciliae, this enzyme is highly inducible. For example, in these organisms purine starvation triggers an approximately 1000-fold up-expression of 3'-NT/NU activity. In the present study, we cloned and characterized a gene encoding this intriguing enzyme from C. luciliae (Cl). Sequence analysis showed that the Cl 3'-NT/NU deduced protein possessed five regions, which we defined here as being characteristic of members of the class I nuclease family. Further, we demonstrated that the Cl 3'-NT/NU-expressed protein possessed both 3'-nucleotidase and nuclease activities. Moreover, we showed that the dramatic up-expression of 3'-NT/NU activity in response to purine starvation of C. luciliae was concomitant with the approximately 100-fold elevation in steady-state mRNA specific for this gene. Finally, results of our nuclear run-on analyses demonstrated that such up-regulation in 3'-NT/NU enzyme activity was mediated at the posttranscriptional level.

Structurally conserved soluble acid phosphatases are synthesized and released by Leishmania major promastigotes

Previously it was reported that promastigotes of virtually all pathogenic Leishmania species, except Leishmania major, release a structurally conserved soluble acid phosphatase (AcP) activity during their growth in vitro (P. S. Doyle and D. M. Dwyer, Exp. Parasitol. 77, 435-444 1993). In the current study we used a highly sensitive fluorogenic detection method to demonstrate that soluble AcPs were in fact produced by promastigotes of several different strains of L. major. These L. major AcP activities were readily immunoprecipitated with a rabbit antibody previously generated against the L. donovani AcP. Results of metabolic labeling and immunoprecipitations demonstrated that AcPs produced by the L. majors strains examined had an apparent molecular mass of approximately 77 kDa. Results of Southern hybridization analysis with an L. donovani AcP gene probe showed that the AcP gene loci were conserved in the L. major strains examined. Taken together, these results indicate that the AcP enzyme has been structurally and functionally conserved throughout the evolution of pathogenic species of Leishmania. Such conservation suggests that the AcPs play a functional role in the growth and survival of this group of important human pathogens.

Dissection of the functional domains of the Leishmania surface membrane 3'-nucleotidase/nuclease, a unique member of the class I nuclease family

Class I nucleases are a family of enzymes that specifically hydrolyze single-stranded nucleic acids. Recently, we characterized the gene encoding a new member of this family, the 3'-nucleotidase/nuclease (Ld3'NT/NU) of the parasitic protozoan Leishmania donovani. The Ld3'NT/NU is unique as it is the only class I nuclease that is a cell surface membrane-anchored protein. Currently, we used a homologous episomal expression system to dissect the functional domains of the Ld3'NT/NU. Our results showed that its N-terminal signal peptide targeted this protein into the endoplasmic reticulum. Using Ld3'NT/NU-green fluorescent protein chimeras, we showed that the C-terminal domain of the Ld3'NT/NU functioned to anchor this protein into the parasite cell surface membrane. Further, removal of the Ld3'NT/NU C-terminal domain resulted in its release/secretion as a fully active enzyme. Moreover, deletion of its single N-linked glycosylation site showed that such glycosylation was not required for the enzymatic functions of the Ld3'NT/NU. Thus, using the fidelity of a homologous expression system, we have defined some of the functional domains of this unique member of the class I nuclease family.

Pathogenic leishmania secrete antigenically related chitinases which are encoded by a highly conserved gene locus

Recently, we identified and characterized a single-copy chitinase gene (LdCht1) from Leishmania donovani, a protozoan pathogen of humans. It has been hypothesized that this parasite enzyme plays a critical role in the survival of all Leishmania species within their sandfly vectors and for their transmission to humans. Thus, in the current study, pulse-field gel electrophoresis and Southern hybridization with the LdCht1 gene probe were used to demonstrate that this chitinase gene has been conserved across species lines of various pathogenic Leishmania. Further, immunoprecipitation and enzyme activity assays using an anti-LdCht1-peptide serum were used to show that the chitinases produced and released by this group of parasites possessed both highly conserved antigenic epitopes and enzyme activities. Results of these studies demonstrate that the chitinase gene locus and enzyme activity have been conserved across species lines among this group of human pathogens.

Invasive pneumococcal infection in Baltimore, Md: implications for immunization policy

BACKGROUND

Streptococcus pneumoniae is a leading cause of infectious morbidity and mortality. Although blacks are known to have a higher incidence of invasive pneumococcal infection than whites, detailed analyses of these differences and their implications for vaccine prevention have not been reported.

OBJECTIVE

To describe the epidemiological characteristics of invasive pneumococcal infection in Baltimore, Md, and its implications for immunization policy.

METHODS

Analysis of active, laboratory-based surveillance during 1995 and 1996 among residents of the Baltimore metropolitan area.

RESULTS

Of 1412 cases, 615 patients (43.6%) were classified as white and 766 (54.2%) as black. The annual incidence of invasive pneumococcal infection among white and black residents of the Baltimore metropolitan area was 17.8 and 59.2 per 100000 population, respectively (P<.01). Among patients aged 18 years and older, the median age of blacks with invasive pneumococcal infections was 27 years younger than that of whites (P<.01). Among males 40 to 49 years old, blacks had a 12-fold higher average incidence than whites (average incidence, 114.5 and 9.3, respectively; P<.01). By the age of 65 years, 83.8% of cases had occurred in black adults, as compared with 43.8% in white adults (P<.01). In a regression model, age, black race, male sex, low median family income, and county prevalence of acquired immunodeficiency syndrome were each independently associated with a higher incidence of pneumococcal infection.

CONCLUSIONS

Young urban black adults in the Baltimore metropolitan area have a dramatically higher incidence of invasive pneumococcal infection than whites. The vast majority of cases of invasive pneumococcal infection in blacks occur before age 65 years. Current immunization efforts have not addressed the high incidence of pneumococcal infection in this population.

Retrospective revaluation or mediated conditioning? The effect of different reinforcers

It is becoming accepted that the associative strength of a cue can change in its absence. However, the rules that govern the association of the representations of absent cues are in dispute. There is evidence to support both the idea that the representation of a cue is associated in the same fashion as the cue itself (e.g. Holland, 1990) and the contrary idea that the representation will be associated in the opposite manner to the cue itself (e.g. Dickinson & Burke, 1996). In three experiments an aversion to almond was formed by the pairing of the induction of nausea by lithium chloride injection with a context previously paired with almond. In addition in the third experiment an aversion was formed to almond when a flavoured solution previously paired with quinine was drunk in a context previously paired with almond. These results suggest that the rules governing the association of the representations of absent cues depend on the type of reinforcer.

Risk of meningococcal infection in college students

CONTEXT

The number of meningococcal outbreaks on college campuses have been increasing in the past few years. However, no published studies have documented the incidence of invasive meningococcal infection in college students or whether the incidence is higher than in the general population of the same age.

OBJECTIVE

To compare the incidence of invasive meningococcal infection in Maryland college students with that of the general population of the same age.

DESIGN

Retrospective cohort study.

SETTING AND PATIENTS

Maryland residents with meningococcal infection from 1992-1997 identified from active, laboratory-based, statewide surveillance for invasive meningococcal disease.

MAIN OUTCOME MEASURES

Incidence of invasive meningococcal infection.

RESULTS

Of 228 patients with invasive meningococcal infection, 67 were aged 16 to 30 years; 11 and 3 of these attended Maryland 4- and 2-year colleges, respectively. Of these, 12 (86%) had infection caused by Neisseria meningitidis serogroups included in the current meningococcal vaccine. The average annual incidence was 1.74 per 100000 among students in 4-year schools vs 1.44 per 100000 for the general population of the same age (P=.60). Among students in 4-year schools, the incidence was 3.24 per 100000 in on-campus residents vs 0.96 per 100000 in off-campus residents (relative risk, 3.4; 95% confidence interval, 1.0-11.6; P=.05).

CONCLUSIONS

The incidence of meningococcal infection in college students is similar to the incidence in the general population of the same age, but college students residing on campus appear to be at higher risk than those residing off campus.

Prevention and control of epidemic keratoconjunctivitis in a teaching eye institute

PURPOSE

To determine if an ongoing infection control program is associated with a reduction in rates of nosocomial outbreaks of epidemic keratoconjunctivitis (EKC) and outbreak morbidity from nosocomial EKC in a large teaching eye institute.

METHODS

The number of nosocomial EKC outbreaks, the number of affected patients, and the total number of patient visits were collected for each year between 1984 and 1997. An infection control program was implemented in 1992. The program included specified methods of patient screening and isolation, handwashing, instrument disinfection, medication distribution, and furlough of infected employees. The program included two levels of intensity of infection control measures, for non-outbreak and outbreak conditions. We compared rates per 100,000 patient visits of nosocomial outbreaks of EKC and affected patients for the 6-year period after the program was implemented, 1992-1997, with corresponding rates for 1984-1991.

RESULTS

One, to three nosocomial outbreaks of EKC occurred annually in the period 1984-1991. After the implementation of the infection control program, no nosocomial outbreaks occurred in three of six years studied. In the pre-infection control years 1984-1991, there were 3.89 outbreaks and 54.09 affected patients per 100,000 visits, respectively. For the post-infection control years 1992-1997, the corresponding rates were 0.54 outbreaks and 5.66 affected patients per 100,000 patient visits. Rates for both outbreaks and affected patients were significantly lower for the post-implementation period (p < 0.005 and p < 0.0005, respectively).

CONCLUSIONS

An ongoing infection control program was associated with decreased rates of nosocomial EKC outbreaks and outbreak morbidity from nosocomial EKC in our institute. Although several reports have described infection control measures that terminated individual outbreaks of nosocomial EKC, this study demonstrates that an ongoing infection control program may preemptively reduce nosocomial EKC outbreaks.

Leishmania: amastigotes synthesize conserved secretory acid phosphatases during human infection

Leishmania donovani is the major causative agent of Old World human visceral leishmaniasis (VL). In vitro, both promastigotes and axenic amastigotes of L. donovani constitutively secrete soluble acid phosphatases (SAcPs), which contain conserved antigenic epitopes. These SAcPs are the most abundant and best characterized secretory proteins of this parasite. The aim of this study was to determine whether this enzyme was produced by intracellular amastigotes during the course of human infection. To that end, sera from acutely infected leishmaniasis patients were tested for anti-SAcP antibodies using L. donovani promastigote culture supernatants. Our results showed that VL patient sera from different endemic foci immunoprecipitated parasite SAcP enzyme activity. Further, these VL patient sera recognized the 110- and 130-kDa SAcPs in both Western blots and radioimmunoprecipitation assays. Results of tunicamycin experiments demonstrated that VL patient anti-SAcP antibodies were directed against the polypeptide backbone of the parasite SAcPs. In addition, both radiolabeled L. donovani SAcPs and native enzyme activities were immunoprecipitated by sera from patients with various forms of cutaneous leishmaniasis. Together, these studies demonstrate that Leishmania amastigotes produce SAcPs during the course of human infections.

Implications of Calreticulin Function in Parasite Biology

Calreticulin (CR) is a Ca(2+)-binding, multifunctional protein. The amazing array of CR-associated functions range from intracellular activities in secondary messenger release, protein folding and the modulation of gene expression to potential interactions with host receptors and signaling machinery and recognition by the host immune system. The multifunctional nature of CR may impact upon the ability of cells to recognize extracellular stimuli and coordinate appropriate responses. Identification of CR isolated from parasites and the conservation of its functions suggests that investigations into the contributions of CR to various aspects of parasite biology should be undertaken because it may reveal information regarding parasite interaction with the host and how the parasite may modulate its response to the host.

Serotype distribution of invasive group B streptococcal isolates in Maryland: implications for vaccine formulation. Maryland Emerging Infections Program

Invasive group B streptococcal (GBS) infection is a major health problem among infants and adults. The formulation of GBS vaccines depends on knowledge of the GBS serotype distribution. Serotype V GBS infection appears to have recently emerged, suggesting that the serotype distribution changes over time. GBS isolates from 210 pediatric patients, 23 pregnant women, and 314 nonpregnant adults with invasive infection in Maryland were studied. The predominant serotypes from infants with early-onset disease were as follows: serotype III, 38% of isolates; serotype Ia, 36%; serotype V, 13%; and serotype II, 11%. Although the majority (60%) of isolates among infants with late-onset infection were serotype III, serotype Ia (23%) was also common. The predominant serotype among isolates from nonpregnant adult patients was serotype V, accounting for 29% of the isolates. The serotype distribution differs between pediatric patients and adults and is changing over time. The inclusion of a relatively small number of serotypes in a GBS vaccine could provide protection against the vast majority of isolates.

The Ld Cht1 gene encodes the secretory chitinase of the human pathogen Leishmania donovani

Leishmania donovani promastigotes were shown to release chitinase activity during their growth in vitro. A PCR-based strategy identified a single copy ORF capable of encoding the L. donovani chitinase (Ld Cht1, 1374 bp). Ld Cht1 was shown to be actively transcribed by L. donovani promastigotes using reverse transcription and PCR amplification. The deduced aa sequence of Ld Cht1 showed high conservation to known chitinases including the putative active and two substrate binding sites. Antiserum generated against four peptides derived from its deduced aa sequence immunoprecipitated an approx. 50-kDa in vitro transcription/translation product of Ld Cht1. Further, this antiserum also immunoprecipitated both the native L. donovani 50-kDa Cht1 protein and the native chitinase activity synthesized and released by these parasites. Cumulatively, these data demonstrated that Ld Cht1 encoded the chitinase of this important human pathogen.

A framework for capturing clinical data sets from computerized sources

The pressure to improve health care and provide better care at a lower cost has generated the need for efficient capture of clinical data. Many data sets are now being defined to analyze health care. Historically, review and research organizations have simply determined what data they wanted to collect, developed forms, and then gathered the information through chart review without regard to what is already available institutionally in computerized databases. Today, much electronic patient information is available in operational data systems (for example, laboratory systems, pharmacy systems, and surgical scheduling systems) and is accessible by agencies and organizations through standards for messages, codes, and encrypted electronic mail. Such agencies and organizations should define the elements of their data sets in terms of standardized operational data, and data producers should fully adopt these code and message standards. The Health Plan Employer Data and Information Set and the Council of State and Territorial Epidemiologists in collaboration with the Centers for Disease Control and Prevention and the Association of State and Territorial Public Health Laboratory Directors provide examples of how this can be done.

Transmission of Mycobacterium tuberculosis by a fiberoptic bronchoscope. Identification by DNA fingerprinting

CONTEXT

An ongoing restriction fragment length polymorphism (RFLP) study of Mycobacterium tuberculosis isolates from tuberculosis (TB) cases revealed an identical 10-banded IS6110 RFLP pattern unique to 2 patients diagnosed as having TB 6 months apart. Their only identifiable link was care at the same hospital.

OBJECTIVE

To determine if nosocomial transmission had occurred.

DESIGN

Traditional and molecular epidemiologic investigation.

MEASUREMENTS

We reviewed medical charts and bronchoscopic records, examined hospital locations visited by both patients, evaluated hospital ventilation systems, and observed cleaning and disinfection of bronchoscopes.

RESULTS

A patient with cough, hoarseness, and fever underwent bronchoscopy and was diagnosed as having TB. A second patient with a mediastinal mass underwent bronchoscopy 2 days later and was diagnosed as having small cell carcinoma. Following 6 months of chemotherapy and radiation therapy, the second patient developed fever and an infiltrate of the right upper lobe of the lung. Bronchoscopic washings revealed acid-fast bacilli and were culture positive for M tuberculosis. Both patients had undergone bronchoscopy with the same instrument in the same operating room with no intervening bronchoscopies. Bronchoscope cleaning and disinfection procedures were inconsistent with national guidelines.

CONCLUSIONS

A contaminated bronchoscope was the most likely source of M tuberculosis transmission between these 2 patients. The RFLP analysis of M tuberculosis isolates was responsible for detecting this nosocomial source of transmission and led to the implementation of public health measures to prevent further spread of infection and disease. This study emphasizes the need for continued vigilance in endoscope cleaning techniques.

Two tandemly arrayed genes encode the (histidine) secretory acid phosphatases of Leishmania donovani

Leishmania donovani promastigotes constitutively secrete a glycosylated and phosphorylated acid phosphatase activity. This secretory acid phosphatase (SAcP) was purified from L. donovani culture supernatants and amino-acid sequence was obtained from both the N-terminus and a tryptic peptide fragment derived from the isolated protein. A polymerase chain reaction (PCR)-based strategy, using degenerate oligo primers designed from the amino-acid sequence data, identified two single-copy, tandemly arrayed open reading frames (ORFs) capable of encoding the L. donovani SAcP (SAcP-1, 2052 bp and SAcP-2, 2124 bp). Both SAcP-1 and -2 were shown to be actively transcribed by L. donovani promastigotes by reverse transcription (RT) and PCR amplification. The deduced amino-acid sequences of SAcP-1 and SAcP-2 show high conservation to each other in four regions: a 23-amino-acid signal peptide; a catalytic domain containing several potential N-linked glycosylation sites; a Ser/Thr-rich repeat region containing multiple potential phosphorylation sites and a common C-terminus. Within the catalytic domain, the L. donovani SAcPs possess two conserved consensus sequences characteristic of histidine acid phosphatases (AcPs). Furthermore, antisera to native L. donovani SAcP immunoprecipitated in vitro transcription/translation products of both SAcP-1 and SAcP-2. Cumulatively, these data indicate that the acid phosphatase activity constitutively secreted by L. donovani promastigotes is composed of two (histidine) AcP isoforms that are encoded by SAcP-1 and SAcP-2, respectively.

Parkville virus: a novel genetic variant of human calicivirus in the Sapporo virus clade, associated with an outbreak of gastroenteritis in adults

This report describes the characterization of Parkville virus, the etiologic agent of an outbreak of foodborne gastroenteritis, that has the morphology of a calicivirus and genetic properties that distinguish it from previously identified strains in the Sapporo/Manchester virus clade. Sequence analysis of the Parkville virus genome showed it contained the RNA-dependent RNA polymerase motifs GLPSG and YGDD characteristic of members of the family Caliciviridae with an organization identical to that reported for the Manchester virus where the capsid region of the polyprotein is fused to the RNA polymerase. Parkville virus however, demonstrates considerable sequence divergence from both the Manchester and Sapporo caliciviruses, providing the first indications that genetic diversity exists within caliciviruses of this previously homogeneous clade. On the basis of recent advances in the genetic characterization of members of the family Caliciviridae, we propose a new interim phylogenetic classification system in which Parkville virus would be included with Manchester and Sapporo virus as a separate group distinct from the small round-structured viruses (Norwalk-like viruses) that also cause diarrhea in humans.

Weight loss in rats produced by running: effects of prior experience and individual housing

To investigate factors affecting activity-based anorexia (ABA) or activity-stress (AS), rats were given 2-hr access to a running wheel immediately prior to their daily 1.5-hr food access during the light cycle. This produced a reduction in food intake, a steady increase in running, and a large drop in body weight with a prolonged delay before weight recovery began. Experiment 1 found that these effects were reduced in rats with prior experience of eating at this time of day. In contrast, prior experience of running in the wheel when on ad lib food enhanced these effects in Experiment 2, where a subsequent change for half the subjects to individual housing produced a further decrease in body weight. The latter factor was investigated from the outset of Experiment 3 and again individually housed rats showed greater weight loss than did group-housed rats. This experiment also found that in rats of the same age a low initial body weight predicts greater vulnerability to ABA. It was concluded that ABA results from activity-induced reduction of feeding, which prolongs adaptation to a new feeding schedule and is accentuated by social isolation.

Activity-based anorexia in rats as failure to adapt to a feeding schedule

Progressive weight loss resulting from restriction to a daily 1.5-hr feeding period and access to a running wheel, the Activity-Based Anorexia (ABA) effect, was obtained in 3 experiments. However, bodyweight recovered when adaptation to the feeding schedule preceded access to the wheel (Experiment 1), when feeding was at the start of the dark period (Experiments 2 and 3), and when wheel access was denied in the 4 hr before food (Experiment 4). It was concluded that ABA results from interference with adaptation to a new feeding schedule due to the development of anticipatory behavior.

Handwashing and glove use in a long-term-care facility

OBJECTIVES

To determine glove use and handwashing practices, the factors associated with infection control practices, and the frequency of potential microbial transmission in a long-term-care facility (LTCF).

DESIGN

Observational study of 230 staff-resident interactions in an LTCF. We recorded resident characteristics, type of activity, staff credentials, and movements of the staff member's hands, then used the LTCF's guidelines to judge appropriateness of glove use and handwashing.

SETTING

255-bed, university-based LTCF in Baltimore, Maryland.

PARTICIPANTS

A systematic sample of staff-resident interactions.

RESULTS

Gloves were worn in 139 (82%) of 170 interactions when indicated, but changed appropriately in only 1 (16%) of 132. Hands were washed when needed before an interaction in 27%, during an interaction in 0%, and after an interaction in 63%. Gloves were less likely to be used when caring for residents with gastrostomy tubes compared with other residents (relative risk, 0.85; 95% confidence interval, 0.73-0.98). Guidelines were followed more frequently during wound care than during other activities. Microbial transmission potentially could have occurred in 158 (82%) of 193 evaluable interactions.

CONCLUSIONS

We documented marked deficiencies in glove and handwashing, demonstrated the possible impact of these deficiencies, and identified factors associated with inadequate handwashing and glove use. This information can be used in future educational and research efforts to improve infection control practices.

Pulmonary tuberculosis in a high school student and a broad contact investigation: lessons relearned

A case of acid-fast bacillus smear-positive cavitary tuberculosis (TB) was diagnosed in a high school senior (Student A) who lived in a community with a low prevalence for TB. A broad TB investigation was conducted in July 1994 among persons who attended the high school graduation with Student A. Follow-up investigations three months later focused on close contacts at highest risk. A positive tuberculin skin test (TST) was defined as induration of > or = 5 mm after placement of purified protein derivative. We determined the TST results and the estimated costs incurred by the local health department for the broad screening that was conducted. TST results were available for 122/161 (75%) close contacts, and for 1804 persons with nonclose contact with Student A. Her family members were known to have had prior positive TSTs. Positive TSTs were found among 3/122 (2.5%) close contacts, versus 34/1804 (1.9%) persons with nonclose contact. Only one close contact had conversion of TST from negative to positive, and no other active TB case was identified. We estimate the broad TST screening cost the local health department $36,507. Broad TST screening was costly and diverted staff from their customary public health service priorities. Local health departments and clinicians should follow the recommendations of the American Thoracic Society and the Centers for Disease Control and Prevention regarding TB contact investigations.

Isolation and characterization of Leishmania donovani calreticulin gene and its conservation of the RNA binding activity

Calreticulin has been implicated in multiple cell functions. Recently, we have shown that both human and simian calreticulin are RNA binding proteins and that their binding activity is due to phosphorylation. To demonstrate that the RNA binding property of calreticulin is an intrinsic part of this multi-functional molecule and is evolutionarily conserved, we isolated and characterized the calreticulin gene from the unicellular parasite, Leishmania donovani. Amino acid sequence homology between human and Leishmania calreticulin (L. d. cal) is limited, but like the human homologue, L. d. cal binds Ca+2, can be phosphorylated in vitro and binds certain RNA sequences in a phosphorylation-dependent manner. Unlike human calreticulin, L. d. cal is glycosylated and its binding to endogenous Leishmania RNA is phosphorylation-independent. The binding of L. d. cal to Leishmania RNA suggests that the RNA binding activity of calreticulin has remained evolutionarily conserved.

Conservation of low-copy gene loci in Old World leishmanias identifies mechanisms of parasite evolution and diagnostic markers

Genome plasticity has been hypothesized to be a driving force behind parasite speciation. We have evaluated divergence in single and low-copy genes in terms of locus organization, chromosomal localization and gene expression in Leishmania infantum, L. major, L. tropica and three widely divergent geographic isolates of L. donovani. Seventeen genes of low to moderate copy number (1-4 copies/haploid genome) were analyzed to identify restriction fragment length polymorphisms (RFLPs) providing heritable markers distinguishing Old World (OW) leishmanias. These RFLP markers were conserved in parasite isolates from primary infections demonstrating their utility as diagnostic tools. The species designations established by RFLP analysis of field isolates was confirmed by use of monoclonal antibodies. All 17 genes were present in each OW leishmania analyzed except LSIP (A45), which was absent from L. infantum. The 17 genes were found to be distributed among 9 distinct chromosomes. However, in spite of variations in chromosome karyotypes among the various OW leishmanias, individual gene probes localized to a similar sized chromosome from each isolate. These observations coupled with a molecular tree derived from RFLP data suggest that the OW leishmanias comprise a monophyletic lineage, with species associated with cutaneous disease exhibiting the greatest level of divergence. Data from this study supports previous observations that species causing cutaneous and visceral disease have diverged primarily by nucleotide substitutions. Such nucleotide divergence may not only lead to changes in protein function and antigenicity, but may also alter gene regulation programs as exemplified by the finding that the LdI-9-5 and LdE-6-1 genes were expressed only in visceralizing leishmanias.

An outbreak of viral gastroenteritis in a nursing home: importance of excluding ill employees

BACKGROUND

In May 1994, 43 persons in a nursing home were reported with gastroenteritis. An outbreak investigation was conducted to determine risk factors for gastroenteritis among residents and staff.

METHODS

Data were analyzed using contingency tables; relative risks (RR) and statistical significance were determined with Fisher's Exact Test. The chi-squared statistic to perform a goodness of fit test for the binomial distribution was used to determine whether cases occurred randomly and independently of each other. Stools were tested for bacterial enteric pathogens, ova, and parasites and were examined by electron microscopy, Southern hybridization, and reverse transcription-polymerase chain reaction. Paired sera were collected to detect fourfold rises in antibody titer by enzyme immunoassay against Norwalk viruses.

RESULTS

Of 121 residents, 62 (51%) had gastroenteritis, as did 64 (47%) of the 136 staff. The index case was a nurse who became ill at work and continued to work, while symptomatic, for another 2 days. Only residents who had received medications from this nurse between May 17 and May 20 became ill on the first day of the outbreak (13 of 35 versus 0 of 5). Nurses and nurse aides were more likely than employees without direct resident contact to be cases (46 of 68 versus 18 of 58; RR, 2.18; P < .001). Bacterial stool cultures and parasite examinations were negative. Results of electron microscopy, polymerase chain reaction with Southern hybridization, and enzyme immunoassay indicated the causative agent was a small, round, structured virus similar to the Snow Mountain Agent.

CONCLUSION

To minimize outbreaks in nursing homes, we recommend that ill staff be excluded from work until symptoms resolve.

Identification of childhood vaccine providers in Maryland

The purpose of the study was to compare the utility of an American Medical Association (AMA)-derived list and a Maryland State Department of Health and Mental Hygiene (state)-derived list of potential childhood vaccine providers (CVPs) in identifying true childhood vaccine providers for the Vaccines for Children (VFC) program in Maryland. A telephone survey of a sample of physicians from the two lists was used to determine their status as providers of routine vaccinations to children. Results showed a significant difference between the two lists. The state-derived list was composed of an estimated 60.7% CVPs, whereas the AMA-derived list was composed of an estimated 36.7% CVPs. Using the capture-recapture method, it was estimated that there are about 2077 CVPs in Maryland. Based on this figure, the state-derived list would have identified 71.7% of the state's CVPs, and the AMA-derived list would have identified 59.4%. Using the AMA-derived list would have required contacting approximately 1800 extra providers to identify the additional 350 CVPs (16.8%) not identified in the state-derived list. Accurate, up-to-date lists of providers that include pertinent practice characteristics would enhance the ability to contact specific providers for VFC program enrollment and for other clinical and public health purposes.

Crithidia luciliae: effect of purine starvation on S-adenosyl-L-methionine uptake and protein methylation

The utilization of S-adenosyl-L-[methyl-3H]methionine ([3H-methyl]AdoMet) by Crithidia luciliae was assessed under nutrient-replete and purine-starvation conditions. Uptake experiments with intact cells demonstrated that the radiolabel from this molecule was accumulated by purine-starved organisms at a rate approximately 10-fold greater than that observed in those cultivated in nutrient-replete medium. Purine-starved cells also incorporated the radiolabel into trichloroacetic acid insoluble material at an approximately 10-fold faster rate than nutrient-replete cells. No differences, however, were observed in the intracellular levels of AdoMet and its metabolites between organisms cultivated under the two conditions. Results of comparative labeling studies with [3H-methyl]AdoMet, S-adenosyl-L-[carboxyl-14C]methionine, L-[methyl-3H]methionine and L-[35S]methionine in the presence and absence of cycloheximide demonstrated that the incorporation of label from [3H-methyl]AdoMet was due to transmethylation and was independent of protein synthesis. Further, approximately 15 methylated protein bands were identified by SDS-PAGE analysis. Lysates from both purine-starved and nutrient-replete organisms demonstrated similar levels of activity of three protein methyltransferases (PMI, II, III). The differences observed in [3H-methyl]AdoMet utilization between purine-starved and nutrient-replete C. luciliae may reflect the enhanced purine transport capacity which results from purine starvation.

Identification of differentially expressed Leishmania donovani genes using arbitrarily primed polymerase chain reactions

Arbitrarily primed polymerase chain reactions (AP-PCR) were used to amplify polymorphic DNA fragments from the genomes of a variety of geographic isolates of Leishmania donovani (Ld). From the latter, five polymorphic DNA fragments were cloned and sequence analysis identified 15 unique clones. Northern blot analysis showed that 13 of the 15 clones hybridized to transcribed RNAs isolated from Ld. Eight of these 13 AP-PCR clones specifically hybridized to Ld RNAs that were differentially expressed in promastigote and 'amastigote' cells. Comparative Northern analysis of four differentially expressed AP-PCR clones indicated that two clones, LdS-14-14 and LdI-9-7, were expressed in Ld and several other Leishmania species. However, RNAs corresponding to two other AP-PCR clones, LdE-6-1 and LdI-9-5, were detected only in members of the Ld complex, and not in L. major (Lm) or L. tropica (Lt). Comparative Southern blot analysis of the LdS-14-14 locus revealed numerous restriction-fragment length polymorphisms (RFLP) distinguishing Lm and Lt from the Ld isolates and L. infantum. However, the LdS-14-14 loci were mapped to similar-sized chromosomes observed among all Old World Leishmania species tested, indicating that localized nucleotide divergence, not chromosomal rearrangement, was responsible for altered Southern blot patterns. These results demonstrate that AP-PCR is a very useful method for identifying expressed gene sequences in organisms of relatively low-complexity genomes. Interestingly, the majority of these sequences identified in this study correspond to differentially expressed genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Congenital syphilis in Maryland, 1989-1991: the effect of changing the case definition and opportunities for prevention

BACKGROUND

The reported incidence of congenital syphilis in the United States rose dramatically during the 1980s. Although lack of prenatal care has been associated with congenital syphilis, little has been published regarding missed opportunities for prenatal intervention.

GOAL OF THIS STUDY

To determine whether congenital syphilis increases in Maryland between 1989 and 1991 resulted from a true increase in congenital syphilis incidence or a change in the surveillance case definition, and to describe missed opportunities for prenatal intervention.

STUDY DESIGN

This was a retrospective cohort study.

RESULTS

When the revised case definition was used, a 473% increase in the number of cases was seen. Among infants who met the revised definition, 45% of mothers had received no prenatal care. Among those whose mothers had received prenatal care, opportunities to intervene were missed for 53%.

CONCLUSIONS

Although a true increase in congenital syphilis incidence occurred before 1990, the increase reported in Maryland between 1989 and 1991 was primarily due to the change in case definition. Many cases of congenital syphilis could have been prevented with early and adequate prenatal care.

Relapsing invasive group B streptococcal infection in adults

OBJECTIVE

To study recurrent group B streptococcal infection in adults.

DESIGN

Patients with more than one reported group B streptococcal infection were identified through active surveillance for this infection. Sterile-site group B streptococcal isolates were evaluated for serotype and molecular subtyping using restriction endonuclease analysis of chromosomal DNA (REAC).

SETTING

All acute-care hospitals in Maryland.

PATIENTS

Nonpregnant residents of Maryland 18 years of age or older.

RESULTS

22 adults had at least two group B streptococcal episodes that were separated by 2 to 95 weeks (mean, 24 weeks). Of 395 patients with invasive group B streptococcal infection who survived the first episode and were followed for at least 1 year, 17 (4.3% [95% CI, 2.6% to 6.9%]) had more than one episode. Several patients were found to have endocarditis or osteomyelitis during the second episode. Group B streptococcal isolates from both episodes were obtained from 18 of 22 patients. Of the 18 isolate pairs, 13 (72% [CI, 46% to 90%]) had identical REAC patterns; the probability that at least 13 matches would be found by chance alone was less than 0.000001. Among patients with recurrent infection caused by the same strain, the interval between episodes was shorter (mean, 14 weeks) than that among patients with recurrent infection caused by another strain (mean, 43 weeks; P = 0.05).

CONCLUSIONS

Recurrent group B streptococcal infection is common among adults and in most cases appears to be caused by relapse. The optimal management of adults with a first episode of group B streptococcal infection needs to be further defined to minimize the likelihood of recurrent disease.

Molecular cloning and characterization of a Leishmania donovani alpha-tubulin gene

We have isolated a cDNA for an alpha-tubulin mRNA from L. donovani promastigotes and determined its complete nucleotide sequence. Both nucleotide and deduced amino acid sequence analysis of this cDNA showed significant similarity with a previously reported, partial sequence of an L. enriettii alpha-tubulin and the complete sequence of human alpha-tubulin. Further, the in vitro translated L. donovani alpha-tubulin gene product was specifically immunoprecipitated with a monoclonal antibody against human alpha-tubulin. Northern blot analysis revealed that there was little change in the expression of the L. donovani alpha-tubulin RNA during parasite differentiation from promastigote to the in vitro grown "amastigote" form. Southern blot analysis revealed a simple genomic organization for the L. donovani alpha-tubulin gene with more than one copy of the alpha-tubulin gene in the parasite genome. To our knowledge, this is the first complete sequence of an alpha-tubulin for Leishmania to be reported in the literature.