Characterizing interactions of Leptospira interrogans with proximal renal tubule epithelial cells

BACKGROUND

Leptospira interrogans is a pathogenic, spirochetal bacterium that is responsible for leptospirosis, an emerging worldwide zoonosis. Leptospires colonize the renal proximal tubules and chronically infect the kidney. Live bacteria are excreted into urine, contaminating the environment. While it is well known that leptospires can persist in the kidneys without signs of disease for several months, the interactions of leptospires with the proximal renal epithelial tubule cells that allow the chronic renal colonization have not been elucidated yet. In the present study, we compared the interactions between a virulent, low passage (LP) strain and a cultured-attenuated, high passage (HP) strain with renal proximal tubule epithelial cells (RPTECs) to elucidate the strategies used by Leptospira to colonize the kidney.

RESULTS

Kinetics analysis of kidney colonization in a mouse model of chronic infection performed by quantitative real-time PCR and immunofluorescence, showed that the LP strain reached the kidney by 3 days post infection (pi) and attached to the basal membrane side of the renal epithelial cells. At 10 days pi, some leptospires were attached to the luminal side of the tubular epithelia and the number of colonizing leptospires gradually increased. On the other hand, the HP strain was cleared during hematogenous dissemination and did not colonize the kidney. Transmission electron microscopy analysis of LP-infected kidneys at 25 days pi showed aggregated leptospires and membrane vesicles attached to the epithelial brush border. Leptospiral kidney colonization altered the organization of the RPTEC brush border. An in vitro model of infection using TCMK-1 cells, showed that leptospiral infection induced a host stress response, which is delayed in LP-infected cells.

CONCLUSIONS

After hematogenous dissemination, leptospires create protective and replicative niches in the base membrane and luminal sides of the RPTECs. During the long-term colonization, leptospires attached to the RPTEC brush borders and membrane vesicles might be involved in the formation of a biofilm-like structure in vivo. Our results also suggested that the virulent strain is able to manipulate host cell stress responses to promote renal colonization.

Effects of Psidium guajava leaf extract on secretion systems of Gram-negative enteropathogenic bacteria

We screened a total of 672 plant-tissue extracts to search for phytochemicals that inhibit the function of the type III secretion system (T3SS) of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC). Among candidates examined, we found that an extract from the leaves of Psidium guajava (guava) inhibited the secretion of the EspB protein from EPEC and EHEC without affecting bacterial growth. The guava extract (GE) also inhibited EPEC and EHEC from adhering to and injecting EspB protein into HEp-2 cells. GE seemed to block the translocation of EspB from the bacterial cells to the culture medium. In addition to EPEC and EHEC, GE also inhibited the T3SS of Yersinia pseudotuberculosis and Salmonella enterica serovar Typhimurium. After exposure to GE, Y. pseudotuberculosis stopped the secretion of Yop proteins and lost its ability to induce the apoptosis of mouse bone marrow-derived macrophages. S. Typhimurium exposed to GE ceased the secretion of Sip proteins and lost its ability to invade HEp-2 cells. GE inhibited EspC secretion, the type V secretion protein of EPEC, but not Shiga toxin2 from EHEC. Thus, our results suggest that guava leaves contain a novel type of antimicrobial compound that could be used for the therapeutic treatment and prevention of gram-negative enteropathogenic bacterial infections.

Leptospiral 3-hydroxyacyl-CoA dehydrogenase as an early urinary biomarker of leptospirosis

Leptospirosis, caused by spirochetes of the genus Leptospira, is a globally widespread, neglected and emerging zoonotic disease. The currently used diagnostic tests are time-consuming, require technical expertise or require the use of sophisticated equipment. Clinicians have pointed out the urgent need to develop a rapid test for the diagnosis of acute leptospirosis with a non-invasive and easy sampling method. In this study, we have focused on a leptospiral enzyme, 3-hydroxyacyl-CoA dehydrogenase (3-HADH), as a urinary biomarker of acute leptospirosis. A specific antiserum for pathogenic Leptospira spp. was produced, targeting a peptide corresponding to amino acids 410 to 424 of 3-HADH. The antiserum was used to investigate whether 3-HADH is excreted in the urine by Western blotting. Among 70 suspected leptospirosis patients, 40 were laboratory confirmed by microscopic agglutination test (MAT) using paired sera samples and/or polymerase chain reaction (PCR). In the acute phase of the laboratory-confirmed leptospirosis cases, sensitivity for 3-HADH, blood PCR and urine PCR were 52.5%, 57.5% and 12%, respectively. 3-HADH was detected from 2 days post-onset of illness (p.o) and could be detected at least until 9 days p.o. The combination of PCR and 3-HADH detection increased sensitivity of diagnosis to 100% in samples collected between 1 and 3 days p.o., and to 82% in samples collected between 4 and 9 days p.o. Our results suggested that the detection of 3-HADH can support a clinical diagnosis of leptospirosis, especially when serological methods are negative during the acute phase.

Epigallocatechin gallate inhibits the type III secretion system of Gram-negative enteropathogenic bacteria under model conditions

Epigallocatechin gallate (EGCG), a major polyphenol in green tea, inhibits the type III secretion system (T3SS) of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC, respectively), Salmonella enterica serovar Typhimurium, and Yersinia pseudotuberculosis. The inhibitory effect causes the inhibition of hemolysis, cell invasion, cell adhesion and apoptosis, which are functions of the type III secretion device. In the case of EPEC, EspB accumulates in the cells. RT-PCR showed that the translation of EspB was not blocked. The transcription of escN, which supplies energy for the injection of the effector factor into the host cells, was also not inhibited. EGCG does not suppress the transcription and translation of T3SS constitutive protein in bacterial cells, but it seems to suppress the normal construction or secretion of T3SS. When Luria-Bertani (LB) medium was used to visualize the EGCG-induced inhibition of T3SS, the inhibitory effect disappeared. The inhibition of T3SS was partially canceled when the T3SS inhibitory potency of EGCG was examined by adding yeast extract, which is a component of LB medium, to DMEM. These results suggest that EGCG probably inhibits secretion by suppressing some metabolic mechanisms of T3SS.

Analysis of Vibrio seventh pandemic island II and novel genomic islands in relation to attachment sequences among a wide variety of Vibrio cholerae strains

Vibrio cholerae O1 El Tor, the pathogen responsible for the current cholera pandemic, became pathogenic by acquiring virulent factors including Vibrio seventh pandemic islands (VSP)‐I and −II. Diversity of VSP‐II is well recognized; however, studies addressing attachment sequence left (attL) sequences of VSP‐II are few. In this report, a wide variety of V. cholerae strains were analyzed for the structure and distribution of VSP‐II in relation to their attachment sequences. Of 188 V. cholerae strains analyzed, 81% (153/188) strains carried VSP‐II; of these, typical VSP‐II, and a short variant was found in 36% (55/153), and 63% (96/153), respectively. A novel VSP‐II was found in two V. cholerae non‐O1/non‐O139 strains. In addition to the typical 14‐bp attL, six new attL‐like sequences were identified. The 14‐bp attL was associated with VSP‐II in 91% (139/153), whereas the remaining six types were found in 9.2% (14/153) of V. cholerae strains. Of note, six distinct types of the attL‐like sequence were found in the seventh pandemic wave 1 strains; however, only one or two types were found in the wave 2 or 3 strains. Interestingly, 86% (24/28) of V. cholerae seventh pandemic strains harboring a 13‐bp attL‐like sequence were devoid of VSP‐II. Six novel genomic islands using two unique insertion sites to those of VSP‐II were identified in 11 V. cholerae strains in this study. Four of those shared similar gene clusters with VSP‐II, except integrase gene.

Lose the battle to win the war: bacterial strategies for evading host inflammasome activation

The inflammasome is composed of nucleotide-binding, oligomerization domain (NOD)-like receptor (NLR) proteins, and leads to caspase-1 activation and subsequent secretion of the proinflammatory cytokines interleukin 1β (IL-1β) and interleukin-18 (IL-18). After certain pathogenic bacteria infect host cells, such as macrophages, NLR-mediated inflammasome activation is triggered to form part of the host defenses against the invading pathogens. However, recent evidence has shown that bacteria have strategies for evading inflammasome activation in host cells. In this review, we focus on NLR-mediated inflammasome activation and bacterial evasion of the inflammasome as part of the battle between the host defenses and pathogens.

Vibrio parahaemolyticus effector proteins suppress inflammasome activation by interfering with host autophagy signaling

Bacterial pathogens utilize pore-forming toxins or sophisticated secretion systems to establish infection in hosts. Recognition of these toxins or secretion system by nucleotide-binding oligomerization domain leucine-rich repeat proteins (NLRs) triggers the assembly of inflammasomes, the multiprotein complexes necessary for caspase-1 activation and the maturation of inflammatory cytokines such as IL-1β or IL-18. Here we demonstrate that both the NLRP3 and NLRC4 inflammasomes are activated by thermostable direct hemolysins (TDHs) and type III secretion system 1 (T3SS1) in response to V. parahaemolyticus infection. Furthermore, we identify T3SS1 secreted effector proteins, VopQ and VopS, which induce autophagy and the inactivation of Cdc42, respectively, to prevent mainly NLRC4 inflammasome activation. VopQ and VopS interfere with the assembly of specks in infected macrophages. These data suggest that bacterial effectors interfere with inflammasome activation and contribute to bacterial evasion from the host inflammatory responses.

V. parahaemolyticus is Gram-negative pathogen that causes a food poisoning in human. To date, a number of bacterial factors that play a role in V. parahaemolyticus virulence have been characterized, yet little is known about the host factors contributing to the disease process and susceptibility to these pathogens. IL-1β, in addition to TNF-α, is thought to be involved in inflammatory responses and disease development during infection with the pathogen, but the mechanisms of IL-1β production remain poorly defined. In this work we found that both the NLRP3 and NLRC4 inflammasomes are activated by thermostable direct hemolysins (TDHs) and type III secretion system 1 (T3SS1) in response to V. parahaemolyticus infection. The activated inflammasomes then triggers the activation of caspase-1, a cysteine protease that is essential for IL-1β processing and release. Furthermore, we identified T3SS1 secreted effector proteins, VopQ and VopS, which prevent mainly NLRC4 inflammasome activation. VopQ and VopS induce autophagy and the inactivation of Rho GTPases, including Cdc42, respectively, and these cellular events interfere with the assembly of specks, the platform of inflammasome activation. Collectively, T3SS1 effector-based suppression of inflammasome activation may provide important insights into bacterial strategies for evading inflammasome-mediated host immune responses.

Inflammasome activation via intracellular NLRs triggered by bacterial infection

Members of the nucleotide-binding, oligomerization domain (NOD)-like receptor (NLR) proteins assemble into a multiprotein platform, known as the inflammasome, to induce caspase-1 activation followed by the subsequent secretion of IL-1β and IL-18. In this review, we focus on the role of NLRs in inflammasome activation as part of the host defence against bacterial pathogens. One of activators of the NLRC4 inflammasome is bacterial flagellin secreted through type III or IV secretion systems, which are important for the pathogenicity of many Gram-negative bacteria. The NLRP3 inflammasome is mainly activated by a large number of bacterial pore-forming toxins. Despite our knowledge of inflammasome activation upon bacterial infection, the function of antibacterial defence under in vivo conditions remains to be elucidated. Further understanding of NLR function should provide new insights into the mechanisms of host pro-inflammatory responses and the pathogenesis of bacterial infections.

Detergents enhance EspB secretion from Escherichia coli strains harboring the locus for the enterocyte effacement (LEE) gene

The effects of detergents (cholic acid, deoxycholic acid, Triton X-100, and Nonidet P-40) on the secretion of EspB from the locus for enterocyte effacement (LEE) gene-positive Escherichia coli strains were examined. Clinical isolates of eight EPEC strains and seven STEC strains were used to detect EspB after they had been cultivated in Luria-Bertani (LB) broth containing one of the detergents. When the bacteria were cultured in LB broth supplemented with one of the detergents, the amount of EspB produced was increased by 2-32-fold depending on the detergent and the strain used. EspB was detected in all strains when they were cultured in LB broth containing all of the detergents. The results obtained in this study can be applied to immunological diagnostic methods for detecting EspB and also to the production of EspB for research purposes.

Pathogenic Vibrio activate NLRP3 inflammasome via cytotoxins and TLR/nucleotide-binding oligomerization domain-mediated NF-kappa B signaling

Vibrio vulnificus and Vibrio cholerae are Gram-negative pathogens that cause serious infectious disease in humans. The beta form of pro-IL-1 is thought to be involved in inflammatory responses and disease development during infection with these pathogens, but the mechanism of beta form of pro-IL-1 production remains poorly defined. In this study, we demonstrate that infection of mouse macrophages with two pathogenic Vibrio triggers the activation of caspase-1 via the NLRP3 inflammasome. Activation of the NLRP3 inflammasome was mediated by hemolysins and multifunctional repeat-in-toxins produced by the pathogenic bacteria. NLRP3 activation in response to V. vulnificus infection required NF-kappaB activation, which was mediated via TLR signaling. V. cholerae-induced NLRP3 activation also required NF-kappaB activation but was independent of TLR stimulation. Studies with purified V. cholerae hemolysin revealed that toxin-stimulated NLRP3 activation was induced by TLR and nucleotide-binding oligomerization domain 1/2 ligand-mediated NF-kappaB activation. Our results identify the NLRP3 inflammasome as a sensor of Vibrio infections through the action of bacterial cytotoxins and differential activation of innate signaling pathways acting upstream of NF-kappaB.

Diagnostic utility of brain-natriuretic peptide for left ventricular diastolic dysfunction in asymptomatic type 2 diabetic patients

AIM

Left ventricular (LV) diastolic dysfunction has been reported to be prevalent in diabetic subjects, but this recognition could often be missed. We evaluated prevalence of LV diastolic dysfunction and diagnostic utility of brain-natriuretic peptide (BNP) in asymptomatic patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

Plasma BNP levels and LV geometry and diastolic filling indices, including the ratio of peak early transmitral Doppler flow (E) over flow propagation velocity (Vp) measured by colour M-mode Doppler echocardiography, were analysed in 98 consecutive asymptomatic patients with type 2 diabetes mellitus and 51 age-matched controls.

RESULTS

The LV mass index and relative wall thickness were higher in diabetic groups than controls without any differences in LV systolic function. The frequency of diastolic dysfunction defined as E/Vp > or = 1.5 were 31% in diabetic groups and 15% in controls (chi(2) = 4.364, p = 0.037). By receiver-operating characteristic (ROC) curve analysis, a BNP cutoff value of 19.2 pg/ml in controls had a 53.1% positive predictive value (53.1%) and a high negative predictive value (94.4%) for E/Vp >/= 1.5, whereas a BNP cutoff value of 18.1 pg/ml in diabetic groups had a 61.8% positive and 97.3% negative predictive values.

CONCLUSIONS

The frequency of E/Vp > or = 1.5 was higher in asymptomatic diabetic patients, suggesting that LV diastolic dysfunction was prevalent. The plasma concentration of BNP could be used to depict LV diastolic dysfunction in such population.

Biological activity of the functional epitope of ciguatoxin fragment AB on the neuroblastoma sodium channel in tissue culture

It is well established that the targeted receptor for ciguatoxin (CTX) in mammalian tissues is the sodium channel, affecting the influx of sodium into cells and altering the action potential and function of the cell. Since the syntheses of fragments of CTX has become available, our focus has been on the receptor functions of the west sphere AB and east sphere JKLM fragments using the neuroblastoma cell assay, guinea pig atrium assay, and the membrane immunobead assay (MIA). The data presented here suggest that the west sphere AB of the ciguatoxin molecule is the active portion and is responsible for the activation of the sodium channels.

Short report: isolation of Escherichia coli O157:H7 from fecal samples of cows in Vietnam

Enterohemorrhagic Escherichia coli O157:H7 was isolated for the first time in Vietnam. Shiga toxin-producing E. coli were isolated from 8 of 100 cows examined. The two strains showing serotype O157:H7 carried the eae, ehxA, and stx2c genes, but the other six were negative for the eae gene.

The long polar fimbriae genes identified in Shiga toxin-producing Escherichia coli are present in other diarrheagenic E. coli and in the standard E. coli collection of reference (ECOR) strains

Long polar fimbriae (LPF) are related to type I fimbriae in genetic organization and were first identified in Salmonella enterica serovar Typhimurium. Four lpfA genetic variants designated lpfA(O157/OI-141), lpfA(O157/OI-154), lpfA(O26) and lpfA(O113) have been identified in Shiga toxin-producing Escherichia coli (STEC). In this study, PCR was employed to determine the distribution of STEC-lpfAs in enteropathogenic, enteroaggregative, enterotoxigenic and enteroinvasive E. coli (EPEC, EAEC, ETEC and EIEC) and in the standard E. coli collection of reference (ECOR). Among the 97 diarrheagenic strains from our collection, only 2 EPEC strains of serotypes O55:H7 and O119:NM were positive for both lpfA(O157/OI-141) and lpfA(O157/OI-154). lpfA(O157/OI-141) was also positive in 1 of 25 ETEC strains. lpfA(O113) was present in 51 of 97 strains and lpfA(O26) in 13 of 97 strains of diverse diarrheagenic categories. STEC-lpfAs were also present in non-pathogenic ECOR strains of all phylogenetic groups. This study showed that the lpfA genes identified in the genome of STEC strains are not specific to this category. Our results suggest that there is a relationship between the lpfA variant and the phylogenetic group.

Pathogenicity of Shigella in healthy carriers: a study in Vientiane, Lao People's Democratic Republic

Shigella spp. isolated from diarrheal patients and non-diarrheal carriers were examined by PCR for the presence of two pathogenic genes, chromosomal ipaH and invasive plasmid encoded ial. Shigella spp. were detected in 7 of 72 diarrheal cases examined (9.7%), and 9 of 145 non-diarrheal cases (6.2%). All isolates from diarrheal cases harbored both ipaH and ial, while all isolates from non-diarrheal cases were positive for ipaH but not ial. These results suggested that Shigella spp. in healthy carriers were basically non-pathogenic.

The relationship between O-antigens and pathogenic genes of diarrhea-associated Escherichia coli

To evaluate the serogrouping-based diagnosis of diarrheagenic Escherichia coli, a total of 1,130 strains of E. coli isolated in several countries were studied. The strains were regarded as enterovirulent on the basis of their O-antigens determined using a commercially available kit containing 43 antisera, and the presence of diarrhea-associated genes (eae, stx, aggR, est, elt, ipaH) was evaluated by PCR. Two hundred sixty-three strains of 1,130 (23.3%) were identified as diarrheagenic based on the presence of at least one pathogenic gene. The probability that E. coli identified as diarrheagenic on the basis of serogrouping actually possessed some pathogenic gene was highest for serogroup O119 (78.4%); other serogroups with a positive rate for pathogenic genes higher than 60% were O111 and O126. No target genes were detected among the strains belonging to serogroups O1, O29, O112ac, O143, O158 and O168. Our results suggest that, in practice, serogrouping is useful for the identification of diarrheagenic E. coli in a very limited number of serogroups.

A single dose of nateglinide improves post-challenge glucose metabolism and endothelial dysfunction in Type 2 diabetic patients

AIMS

This randomized crossover placebo-controlled study aimed to assess the efficacy of nateglinide, a phenylalanine-derived insulin secretagogue, on forearm endothelial function in diabetic subjects before and after an oral glucose load.

METHODS

Forearm blood flow (FBF) was measured using strain-gauge plethysmography during reactive hyperaemia before and after an oral glucose load (75 g) with a prior use of placebo or nateglinide (90 mg) in 15 diet-treated Type 2 diabetic patients or age-matched controls with normal glucose tolerance.

RESULTS

The peak FBF response and total reactive hyperaemic flow (flow debt repayment: FDR), indices of resistance artery endothelial function, were decreased after an oral glucose load in diabetic patients, but unchanged in controls. Nateglinide administered to diabetic patients accelerated insulin secretion and reduced post-challenge plasma glucose, and also abolished the post-challenge impairment of endothelial function. The peak FBF and FDR were well correlated with 120-min glucose levels and 30-min insulinogenic index.

CONCLUSIONS

A single challenge of glucose was shown to impair endothelial function in diabetic patients, and the post-challenge endothelial dysfunction was improved by a prior use of nateglinide. Long-term effects of nateglinide on endothelial function in Type 2 diabetic patients need to be clarified in future studies.

Drug susceptibility and its genetic basis in epidemic Vibrio cholerae O1 in Vietnam

The drug susceptibility and genes responsible for the drug resistance of Vibrio cholerae O1 isolated in Vietnam in 1995, 2000 and 2002 were studied. The strains isolated in 1995 were resistant to streptomycin and harboured the class I integron which contained the aadA1 gene responsible for streptomycin resistance. The strains isolated in 2000 were devoid of a class I integron but were multiple-drug resistant and harboured SXT constin, with several drug-resistant genes. The genes responsible for streptomycin resistance were strA and strB. The strains isolated in 2002 were sensitive to all drugs examined, and the organisms were devoid of both class I integron and SXT constin. Cholera outbreaks in the three periods examined (1995, 2000 and 2002) were apparently due to different categories of V. cholerae O1.

Initial stage of hospital contamination with methicillin-resistant Staphylococcus aureus in Lao People's Democratic Republic

Monitoring drug-resistant Staphylococcus aureus has been carried out in Lao People's Democratic Republic (Lao PDR) since 1993. No methicillin-resistant S. aureus (MRSA) strains were detected until 2001 when two isolates were found: 01LP40, which was coagulase type IV, enterotoxin non-productive, and SCCmec (staphylococcal chromosome cassette mec) type III; and 01LP63 from a different hospital, which was coagulase type II, enterotoxin productive, and the SCCmec belonged to a new type. In 2002 four MRSA isolates similar to the latter were detected, 02LP211, 02LP214, 02LP217 from the same hospital as 01LP63, and 02LP100 from a third hospital. This appears to be the initial stage of a MRSA epidemic in Lao PDR. Careful monitoring and intensive monitoring and precautions are recommended.

Comparative chracterization of Staphylococcus aureus isolates from throats and noses of healthy volunteers

Staphylococcus aureus isolates in 2001 from the nose and the throat of an adult population were characterized for their incidence and type. The incidence was 51%, present in 80 out of 157 individuals examined, consisting of 34 nasal carriers, 24 throat carriers, and 22 who carried the isolates in both the nose and throat. Among these isolates, 2 and 5 from the nose and the throat, respectively, were identified as methicillin-resistant S. aureus. S. aureus from the nose and throat of the same individuals were characterized for identification. Examination of their phenotypes revealed that in 11 individuals the clone of S. aureus in the throat was different from the nasal clone. These results suggested that staphylococcal flora in the nose and the throat were independently formed, and that attention should also be directed to the carriers of S. aureus in the throat for the control of nosocomial infection.

The incidence of Escherichia coli having pathogenic genes for diarrhea: a study in the People's Democratic Republic of Lao

The incidence of Escherichia coli having pathogenic genes for diarrhea was studied in Laos in 2002. A total of 525 E. coli strains from 278 patients (basically, two E. coli isolates from each patient) were examined by PCR to detect the known pathogenic genes (stx, eae, elt, est, ipaH, and aggR). These genes were detected in 23 strains from 16 patients (16/278: 5.8%). In 10 cases of the 16, one of the two isolates from each individual was negative for the gene, and in the other six cases, both isolates had the gene (same gene in four cases). E. coli having eae but no stx (enteropathogenic E. coli [EPEC]) was found in two cases out of 278 (0.7%). Nevertheless, Class I classical EPEC (serogroup-based) was found in 77 cases (28%). Enterotoxigenic E. coli, enteroaggregative E. coli, and enterohemorrhagic E. coli were found in 9, 4, and 1 cases, respectively. Enteroinvasive E. coli was not detected. This study suggested that the incidence of diarrhea due to E. coli is not as high as has been previously thought.

Multiplex PCR assay for identification of human diarrheagenic Escherichia coli

A multiplex PCR assay for the identification of human diarrheagenic Escherichia coli was developed. The targets selected for each category were eae for enteropathogenic E. coli, stx for Shiga toxin-producing E. coli, elt and est for enterotoxigenic E. coli, ipaH for enteroinvasive E. coli, and aggR for enteroaggregative E. coli. This assay allowed the categorization of a diarrheagenic E. coli strain in a single reaction tube.

Staphylococcus aureus isolated from hospital staff: a comparative study of Laos and Japan

Staphylococcus aureus isolated from hospital staff (nurses and doctors) in Laos were characterized for future reference and for comparison with organisms found in Okinawa, Japan. No methicillin-resistant S. aureus (MRSA), among 38 isolates examined, was found in Laos, but 16 of 36 Japanese isolates (44%) were identified as MRSA. The minimum inhibitory concentrations (MICs) of ampicillin and tetracycline against Lao isolates were definitely higher than those against Japanese isolates. The MIC(80) of tetracycline was 50 microg/ml and 0.4 microg/ml in Lao and Japanese isolates, respectively. There was no marked difference in the production of enterotoxin by S. aureus strains in the two countries. Toxic shock syndrome toxin-1 was produced by only 1 of 38 Lao isolates but by 5 of 36 Japanese isolates. Coagulase types varied greatly, but about 50% of the isolates in both countries produced untypable coagulase. Since the interaction of Laotians with foreigners has increased rapidly in recent years, the careful monitoring of drug-resistant pathogens is required.

Enteroaggregative Escherichia coli: incidence in Japan and usefulness of the clump-formation test

The usefulness of the clump-formation test described by Albert et al. for identifying enteroaggregative Escherichia coli (EAggEC) and the incidence of EAggEC in Japan were studied. One hundred and seventy strains of E. coli agglutinated with enteropathogenic E. coli diagnostic antisera were collected from a variety of districts in Japan. All isolates were from diarrheal stools. EAggEC was identified on the basis of the presence of the aggR gene accompanied by aggregative adhesion to HEp-2 cells. After 24 strains carrying eaeA, elt, est, stx-1, stx-2, or ipaH genes were eliminated, the remaining 145 strains were examined for adhesion to Hep-2 cells, the presence of the aggRgene, and clump formation on the surface of Muller-Hinton broth. aggR was detected in 10 strains, and 9 of them displayed aggregative adhesion to HEp-2 cells. Seven strains produced marked clumps and 22 showed moderate clump formation. The sensitivity and specificity of the clump-formation test for detecting EAggEC were each about 90%, and they varied slightly depending on the stringency of evaluation for the degree of clump formation. From these results, we conclude that the incidence of EAggEC cannot be ignored as a possible cause of diarrheal disease in Japan, and we strongly recommend the clump-formation test for detecting EAggEC.

Left ventricular pseudoaneurysm after sutureless repair of subacute left ventricular free wall rupture: a case report

A 65-year-old woman presenting with a left ventricular pseudoaneurysm 27 months after sutureless repair of a subacute left ventricular free wall rupture complicating acute myocardial infarction is described. An autologous pericardial patch and gelatin resorcin formaldehyde (GRF) glue were used in the repair. A small pseudoaneurysm bulged out over the true aneurysm of the left ventricle. We performed a Dor operation and concomitant bypass grafting to the right coronary artery. Although sutureless repair is an effective procedure for subacute left ventricular free wall rupture, left ventricular pseudoaneurysm in the late postoperative period may be a rare problem after this repair.

Cardiac reoperation in a patient with osteogenesis imperfecta: a case report

A case of a 40-year-old man with dehiscence of the prosthetic aortic valve and recurrence of mycotic aneurysm of the left ventricular outflow tract with osteogenesis imperfecta is presented. He had an operation of aortic valve replacement and direct closure of the mycotic aneurysm for infective endocarditis twenty-one months ago. We performed reoperation of prosthetic aortic valve, patch closure of the mycotic aneurysm and graft replacement of the ascending aorta. He was complicated with multiple fractures of bilateral scapla and dislocation of left shoulder one postoperative day. Fortunately, cardiac reoperation was performed successfully in this patient despite anticipated difficulties with tissue friability with osteogenesis imperfecta.

Transition of drug susceptibilities of Vibrio cholerae O1 in Lao People's Democratic Republic

The changes of drug susceptibilities of Vibrio cholerae O1 isolated during the past 7 years (1993-1999) in Lao PDR were investigated. The most noteworthy finding was the appearance of polymyxin B sensitive El Tor vibrios. Until 1996, the susceptibilities were almost as expected and cholera disappeared in 1997. When a cholera outbreak resurfaced in 1998, the susceptibilities of isolated V. cholerae O1 against tetracycline, sulfamethoxazol-trimethoprim, chloramphenicol and polymyxin B were quite different from those of previously isolated organisms. Minimum inhibitory concentrations (MICs) of tetracycline and chloramphenicol against the isolates in 1998 were about 16 times higher than those against the previous isolates, and the MICs of sulfamethoxazol-trimethoprim were about 256 times higher than those against the previous isolates, (trimethoprim 32 microg/ml: sulfamethoxazol 608 microg/ml). Eleven percent of the isolates (11/99) were as sensitive to polymyxin B as the classic cholera vibrios (MIC < 2 microg/ml). In 1999, the susceptibility pattern was almost the same as that in 1998 except for polymyxin B to which 58% of the isolates (21/36) became sensitive.

[Pathogenic bacteria in the nasal vestivulum of children with acute respiratory tract infection]

The isolation frequency of pathogenic bacteria for acute respiratory infection (ARI) in the pharynx and nasal vestivulum was investigated. Age group-matched children with or without ARI including 109 individuals in each group were examined. Any of the organisms, which are widely regarded as the pathogens causing ARI such as Haemophilus influenzae, Streptococcus pneumoniae, beta-haemolytic Streptococcus, Staphylococcus aureus, and Moraxella catarrhalis, were isolated from 91% of the patient group and from 77% of the healthy group. The isolation frequency of S. pneumoniae in the nasal vestivulum of the patient group was outstanding. The healthy carrier rates of S. pneumoniae in the pharynx and nasal vestivulum were 9% and 8%, respectively. Whereas the isolation frequencies from the patient group were 7% and 28%, respectively. alpha-haemolytic Streptococci except S. pneumoniae revealed different tendency from S. pneumoniae. These organisms were almost always isolated from their pharynx but rarely isolated from the nasal vestivulum. The isolation frequency of H. influenzae from the pharynx of the patient group was 41%, which was slightly higher than 34% in the healthy group, but the difference was statistically not significant. H. influenzae was not isolated from the nasal vestivulum of the healthy group, nevertheless it was isolated from 25% of the patient group. The isolation of H. influenzae from the nasal vestivulum may have some important information about ARI. S. aureus was isolated from the pharynx with higher rate than the nasal vestivulum in both groups, and moreover, the isolation frequency of S. aureus in the healthy group was higher than the patient group. It means that the diagnosis of staphylococcal infection should be made very carefully. Considering the results of this study, it could be said that bacteriologic examination of the specimens from nasal vestivulum is valuable to determine S. pneumoniae and H. influenzae as the etiologic agents of ARI.

A filamentous phage of Vibrio parahaemolyticus O3:K6 isolated in Laos

A filamentous phage, 'lvpf5,' of Vibrio parahaemolyticus O3:K6 strain LVP5 was isolated and characterized. The host range was not restricted to serotype O3:K6, but 7 of 99 V. parahaemolyticus strains with a variety of serotypes were susceptible to the phage. The phage was inactivated by heating at 80 C for 10 min and by treating with chloroform. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the phage exhibited a 3.8 kDa protein. The amino-terminal amino acid sequence of the coat protein was determined as AEGGAADPFEAIDLLGVATL. The phage genome consisted of a single-stranded DNA molecule. The activity of the phages was inhibited by anti-Na2 pili antibody.

Etiological study of diarrheal patients in Vientiane, Lao People's Democratic Republic

The etiological agents of diarrhea in Vientiane, Lao People's Democratic Republic (Lao PDR), were studied in the period from October 1996 to August 1997. A total of 880 patients with diarrhea visiting medical facilities were examined for Shigella, Salmonella, diarrheagenic Escherichia coli, vibrio, Aeromonas, Campylobacter, and rotavirus. Shigella spp., heat-stable enterotoxin (ST)-producing E. coli, and serogroup-based enteropathogenic E. coli were found to be the main organisms causing diarrhea in Vientiane, with frequencies of 16.8% (148 of 880), 17.2% (111 of 645), and 11.0% (97 of 880), respectively. Relatively low incidences were observed in the cases of Salmonella spp., (0.6%; 5 of 880), Campylobacter spp. (4.4%; 39 of 880), and rotavirus (6.1%; 9 of 148), and no isolates of V. cholerae O1 or O139 or Aeromonas were recovered. An analysis of the incidences of enteropathogens with respect to age and seasonal variations demonstrated that the frequencies of isolation of Shigella spp. and heat-labile enterotoxin-producing E. coli were significantly higher in those aged 1 to 5 years than in those younger than 1 year of age and those older than 5 years of age (P < 0.0001 and P < 0.05, respectively) and that the frequencies of isolation of Shigella spp. and ST-producing E. coli were significantly higher in the rainy season than in the dry season (P < 0.005 and P < 0.001, respectively). Almost all strains of Shigella spp. tested were resistant to ampicillin, tetracycline, and erythromycin and were susceptible to cefdinir and ofloxacin. This is the first intensive and longitudinal study to define the etiologic agents of diarrheal diseases in Lao PDR.

Adhesive property of toxin-coregulated pilus of Vibrio cholerae O1

The adhesive property of toxin-coregulated pilus (TCP) to the human intestine jejunum), and whether or not TCP mediates the adhesion of Vibrio cholerae 395 organisms to the intestinal epithelium were investigated using visually proving methods. The purified TCP did not agglutinate human erythrocytes nor adhere to the surface of human intestinal epithelium. V. cholerae 395 adhered to the epithelium, but the adhesion was not inhibited by blocking the pili with the Fab fraction of anti-TCP IgG. The organisms adhered to the intestine treated with purified TCP in advance, as well as to the intact intestine. These findings suggest that TCP is not involved in the adhesion of these organisms to the intestinal epithelium.

Comparison of a reversed passive latex agglutination and a polymerase chain reaction for identification of cholera toxin producing Vibrio cholerae O1

Production of cholera toxin (CT) in AKI medium and conservation of CT gene (ctx) of 49 strains of Vibrio cholerae O1 were compared by reversed passive latex agglutination (RPLA) and polymerase chain reaction (PCR). The production of CT agreed with conservation of the ctx in 48 out of the 49 strains. Ten strains were positive, and 38 strains were negative by both methods. Only one strain was negative in RPLA and positive in PCR. This suggested that the combination of AKI-SW and RPLA is comparable to PCR to identify CT-producing V. cholerae O1.

Characterization of Vibrio cholerae O139 synonym Bengal isolated from patients with cholera-like disease in Bangladesh

Vibrio cholerae O139 (synonym Bengal), a novel serovar of V. cholerae, is the causative agent of large outbreaks of cholera-like illness currently sweeping India and Bangladesh. Eight randomly selected V. cholerae O139 isolates were studied for their biological properties, which were compared with those of V. cholerae O1 and other V. cholerae non-O1. The V. cholerae O139 isolates were characterized by the production of large amount of cholera toxin, hemagglutination, weak hemolytic properties, resistance to polymyxin B, lysogeny with, and production of, kappa type phage (4/8 isolates only), and resistance to both classical and El Tor-specific phages. Thus, V. cholerae O139 isolates had an overall similarity with V. cholerae O1 El Tor.

Pili of vibrio cholerae widely distributed in serogroup O1 strains

The distribution of Vibrio cholerae O1 pili consisting of 16 kDa subunit protein (16K-pili) was examined by Western blotting, using 211 strains from various origins and specific anti-16K-pili sera. The 16 kDa protein was detected in all 211 strains. The pili were purified from 3 El Tor and 3 classical strains, and characterized by hemagglutination and inhibition tests. All purified pili were hemagglutinative. However, the hemagglutinating activity of classical pili disappeared after exposure to 5 M urea and the agglutination induced by the classical pili was inhibited by D-mannose, alpha-methylmannoside, D-glucose and N-acetylglucosamine. On the contrary, El Tor pili were resistant to these sugars and urea.

Culture conditions for stimulating cholera toxin production by Vibrio cholerae O1 El Tor

A method that stimulates cholera toxin (CT) production by Vibrio cholerae O1 biotype El Tor (El Tor vibrios) to the level of several micrograms per ml in the culture fluid was established. Such a large amount of CT was obtained by the following method: El Tor vibrios were cultured in AKI medium (1.5% Bacto peptone, 0.4% yeast extract-Difco, 0.5% NaCl, 0.3% NaHCO3) at 37 C for 4 hr in a stationary test tube and then for 16 hr in a shaken flask, with inoculum sizes of 10(5) to 10(7)/ml. With this method, 35 strains out of 60 examined produced 2 to 16 micrograms/ml of CT as determined by the reversed passive latex agglutination test (RPLA). Thirty-three randomly selected strains out of the 60 produced reasonable amounts of rabbit skin vascular permeability factor, reflecting the amount of CT titrated with RPLA.