Japanese Journal of Infectious Diseases
Online ISSN : 1884-2836
Print ISSN : 1344-6304
ISSN-L : 1344-6304
Volume 66, Issue 4
Displaying 1-23 of 23 articles from this issue
Review
  • Fantahun Biadglegne, Weghata Tesfaye, Belay Anagaw, Belay Tessema, Tew ...
    Article type: Review
    2013 Volume 66 Issue 4 Pages 263-268
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Tuberculosis (TB) is one of the most serious public health challenges in Ethiopia. Indeed, Ethiopia ranks 7th among 22 countries with a high burden of TB worldwide. Both pulmonary TB and extrapulmonary TB (EPTB) are issues of concern. Ethiopia ranks 3rd in terms of the number of EPTB patients worldwide, with TB lymphadenitis (TBL) being the most common. According to the World Health Organization's Global TB Report 2009, the estimated number of TB patients in Ethiopia was 314,267 in 2007, with an estimated incidence rate of 378 patients per 100,000 population. Furthermore, 36% patients suffered from EPTB, with TBL accounting for 80% of these patients. In Ethiopia, pathological services, culture, and drug susceptibility testing for mycobacterium species are not available as routine tests, not even for cases with suspected infection by drug-resistant strains. Therefore, the management of multidrug-resistant (MDR) TB in Ethiopia is currently unsatisfactory. Against this background, a high index of clinical doubt and timely use of diagnostic methods, prompt confirmation of diagnosis, and early initiation of specific anti-TB treatment are the key factors for the successful management of MDR-TB and TBL in Ethiopia.
    Download PDF (221K)
Original Article
  • Toyoko Nakagomi, Kazuya Kato, Hiroyuki Tsutsumi, Osamu Nakagomi
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 269-275
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Rotavirus gastroenteritis (RVGE) is one of the most common early childhood diseases; however, little information exists on the frequency of RVGE attacks during peak epidemic months and the subsequent clinical consequences in Japanese children. Therefore, we conducted a nationwide internet survey that targeted mothers whose children recently experienced an episode of RVGE or influenza from January 2011 to April 2011. Data concerning the incidence and clinical consequences of RVGE and influenza among 15,137 children aged <3 years were collected. Of these, 1,286 children who experienced an RVGE episode and 1,487 children who experienced an influenza episode visited a physician or required hospital admission. Data analysis of 867 RVGE episodes and 897 influenza episodes found that 25% of children with RVGE required 8–14 days for recovery, 28% received intravenous rehydration, 7% were hospitalized, 15% visited an emergency department, 70% sought medical interventions ≥2 times, and 32% sought medical intervention ≥3 times. Compared with influenza, RVGE required a longer recovery period, and was associated with more frequent episodes of intravenous rehydration, hospitalization, and emergency department and physician visits. Our results indicate that, like influenza, RVGE occurring during peak epidemic months in children aged <3 years imposes a substantial burden on families and medical institutions in Japan.
    Download PDF (419K)
  • Itsuki Hamamoto, Kazuhiro Harazaki, Naohiko Inase, Hiroshi Takaku, Mas ...
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 276-283
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Influenza is a global public health problem that causes a serious respiratory disease. Influenza virus frequently undergoes amino acid substitutions, which result in the emergence of drug-resistant viruses. To control influenza viruses that are resistant to currently available drugs, it is essential to develop new antiviral drugs with a novel molecular target. Here, we report that cyclosporin A (CsA) inhibits the propagation of influenza virus in A549 cells by interfering with a late event in the virus life cycle. CsA did not affect adsorption, internalization, viral RNA replication, or synthesis of viral proteins in A549 cells, but inhibited the step(s) after viral protein synthesis, such as assembly or budding. In addition, siRNA-mediated knockdown of the expression of the major CsA targets, namely cyclophilin A (CypA), cyclophilin B (CypB), and P-glycoprotein (Pgp), did not inhibit influenza virus propagation. These results suggest that CsA inhibits virus propagation by mechanism(s) independent of the inhibition of the function of CypA, CypB, and Pgp. CsA may target an unknown molecule that works as a positive regulator in the propagation of influenza virus. Our findings would contribute to the development of a novel anti-influenza virus therapy and clarification of the regulatory mechanism of influenza virus multiplication.
    Download PDF (414K)
  • Ja Young Lee, Jeong A. Kim, Haeng Soon Jeong, Jeong Hwan Shin, Chulhun ...
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 284-289
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    The study aimed to investigate the prevalence of various serotypes and extended-spectrum β-lactamase-producing features of Salmonella strains and to determine the antimicrobial susceptibility of 256 Salmonella strains other than Salmonella serotype Typhi, which were isolated at 12 university hospitals in Korea. We identified 46 serotypes of Salmonella spp. Serogroup D was the most common (39.5%), followed by B (32.4%), C (22.7%), E (2.7%), A (2.3%), and G (0.4%). The three most common Salmonella serotypes were Enteritidis (36.3%), Typhimurium (16.8%), and Infantis (7.8%). Six strains that belonged to serotype Paratyphi A and nine that belonged to serotype Paratyphi B were also detected. The 256 Salmonella strains had a 38.7% rate of resistance to ampicillin, 23.0% to chloramphenicol, 8.2% to cefotaxime, 8.6% to ceftriaxone, and 6.3% to trimethoprim-sulfamethoxazole. The antimicrobial resistance rates of Salmonella serogroups B and D were higher than those of the other serogroups. Seven isolates carried blaCTX-M: four CTX-M-15, two CTX-M-14, and one CTX-M-3.
    Download PDF (121K)
  • Young June Choe, Young-Joon Park, Hye Suk Eom, Eun Seong Kim, Geun-Rya ...
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 290-294
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Measles was declared eliminated from the Republic of Korea in 2006; however, recently the number of reported cases has been gradually increasing. To address this issue, we summarized the measles surveillance data collected during 2002–2011, and aimed to evaluate the performance of the current surveillance system in Korea. We analyzed data from the national surveillance system to describe the occurrence of measles. Surveillance indicators proposed by the World Health Organization were used to evaluate the performance of the current measles surveillance system. Between 2002 and 2005, a gradual decrease in confirmed cases of measles was noted, whereas cyclical increases were noted from 2006 to 2011. Since 2006, confirmed cases of measles were more likely to be identified by laboratory methods. In general, the incidence of confirmed case was less than one per million in Korea; however, this figure increased in 2002 (1.3/million), 2007 (4.0), and 2010 (2.3). Most cases were occurred in the age groups 0–23 months and 12–17 years. Laboratory testing was performed in most suspected cases; however, the proportion of discarded cases was low. Overall, more than half of the reported cases experienced an onset of symptoms from April to June. The incidence of measles is relatively low in Korea, and the laboratory surveillance may have helped in identifying under-diagnosed cases within the country. It remains important to continuously assess the surveillance data to improve the surveillance performance.
    Download PDF (232K)
  • Toshiro Kuroki, Tomoe Ishihara, Ichiro Furukawa, Alexandre Tomomitsu O ...
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 295-298
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    A total of 87 wild snakes of 6 species in 2 families collected in Japan were examined for the presence of Salmonella. The prevalence of Salmonella was 58.6%, and that of Salmonella enterica subspecies I, which includes most human pathogenic serotypes, accounted for 12.6%. S. enterica subspecies I was isolated from Japanese grass snakes and Japanese four-striped snakes, and the isolates belonged to 6 serotypes: S. enterica subspecies enterica serotypes Eastbourne, Mikawashima, Narashino, Newport, Saintpaul, and Thompson. The prevalence of S. enterica subspecies IIIb was higher (41.4%) than that of S. enterica subspecies I, and it was isolated from 4 snake species. The prevalence of Salmonella enterica subspecies and isolation of serotypes that are commonly detected in reptiles and human salmonellosis suggest that wild snakes may become a source of Salmonella infection.
    Download PDF (112K)
  • Dilek Guldemir, Atila T. Kalaycioglu, A. Basak Altas, Gulay Korukluogl ...
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 299-305
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    The aimes of the present study were to monitor genetic alterations in the hemagglutin (HA) gene and oseltamivir resistance-related alterations in the neuraminidase (NA) gene of influenza A(H1N1)pdm09 viral isolates detected during the post-pandemic period in Turkey. A total of 2601 clinical specimens obtained from suspected cases of influenza A(H1N1)pdm09 viral infections were analyzed by real-time reverse transcription polymerase chain reaction. Viral RNA was detected in 233 (9%) clinical specimens. Sequence analysis of the HA gene in 16 random isolates showed >98.7% homology among each other and with the A/California/07/2009 vaccine strain. These 16 isolates had common (75%–100%) amino acid substitiutions at positions P83S, D97N, S203T, R205K, I216V, V249L, I321V, and E374K in the HA gene. In addition, two additional rare mutations were also observed at positions S162N (addition of a glycosylation site, 6.25%) and A186T (receptor binding region, 6.25%). On the basis of amino acid substitutions in the HA1 domain, majority of the Turkish isolates were classified in the genetic group v and others in the genetic groups ii, iii, and vi. In the present study, we observed an increase in the variety and ratio of mutations detected in the HA1 and HA2 domains of the HA gene; however, these alterations have not yet resulted in vaccine escape mutants in Turkey. In addition, analysis of the NA regions of the isolates revealed that oseltamivir resistance was not an issue in Turkey.
    Download PDF (602K)
  • M. Sayan, A. Willke, N. Ozgunes, F. Sargın
    Article type: Original Article
    2013 Volume 66 Issue 4 Pages 306-311
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    In this study, we determined the subtype distribution and the primary drug-resistant mutations in HIV-1 strains isolated from antiretroviral therapy (ART)-naive patients in Turkey. The study included 117 newly diagnosed HIV-1 positive Turkish patients. HIV-1 subtypes and circulating recombinant forms (CRFs) were identified by phylogenetic analysis (neighbor-joining method), and drug-resistant mutations were analyzed according to the 2009 World Health Organization list of surveillance drug-resistant mutations. Subtype CRFs (CRF 02_AG, CRF 01_AE, CRF 12_BF and CRF 03_AB; 47%, 55/117) and B (33.3%, 39/117) were identified as the most common occurring HIV-1 subtypes in Turkey. The patients had primary antiretroviral resistance mutations to nucleos(t)ide reverse transcriptase (RT) inhibitors (NRTIs) (M41L, T215C, T215D, and K219Q), non-nucleoside RT inhibitors (NNRTIs; K103N), and protease inhibitors (PIs; I47V, G73S). The prevalence of overall primary antiretroviral resistance was 7.6% (9/117) in HIV-1 patients from Turkey and drug-resistant rate for NRTIs, NNRTIs, and PIs were 4.2% (5/117), 1.7% (2/117), and 1.7% (2/117), respectively. In this study, various CRFs of HIV-1 were determined, for the first time, in Turkey. The prevalence of HIV-1 primary drug-resistant mutations in ART-naive patients suggested that resistance testing should be incorporated as an integral part of HIV management, and the choice of a first-line therapy regime should be guided by the results of genotypic resistance in Turkey.
    Download PDF (302K)
Short Communication
  • Takayoshi Tashiro, Koichi Izumikawa, Masato Tashiro, Yoshitomo Morinag ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 312-316
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Chronic necrotizing pulmonary aspergillosis (CNPA) is an indolent, cavitating process in the lungs resulting from invasion of lung tissue by Aspergillus spp. However, most previous reports have not found any clear evidence of parenchymal invasion, and clinical distinction between CNPA and chronic cavitary pulmonary aspergillosis (CCPA) is difficult. We performed a histopathological study of lung specimens obtained by autopsy, surgical resection, or biopsy to clarify the characteristic pathological and clinical features of CNPA. We present 4 cases of proven CNPA, diagnosed by histological demonstration of tissue invasion by the fungus, and present its clinical features. These 4 patients were male, and the mean age was 62 years (range, 51–75 years). Their underlying conditions were chronic obstructive pulmonary disease (n = 3), sequelae of pulmonary tuberculosis (n = 2), and diabetes mellitus (n = 1). Aspergillus precipitation tests were positive for 3; and Aspergillus antigen tests were positive for 2 on admission, and subsequently, for all 4. The isolated pathogens were Aspergillus niger for 1 and A. fumigatus for 1. Initial radiographic findings were infiltrates or nodular lesions, which slowly progressed and cavitated before the appearance of fungus balls. Although CNPA has characteristic pathological features, it is clinically difficult to distinguish CNPA from CCPA. We propose to use the term chronic progressive pulmonary aspergillosis for both CNPA and CCPA.
    Download PDF (477K)
  • Seung-Ji Kang, Joon Hwan An, Jin Kim, Mi Ok Jang, Seong Eun Kim, Kyung ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 317-319
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    The efficacy and safety of raltegravir (RAL) with tenofovir (TDF)/emtricitabine (FTC) have been well studied in human immunodeficiency virus (HIV)-infected patients. However, limited clinical data are available on the use of RAL with abacavir (ABC)/lamivudine (3TC) or zidovudine (ZDV)/3TC. We investigated HIV-1-infected Korean adults, including 13 antiretroviral-naïve patients and 15 antiretroviral-experienced patients, treated with RAL plus ABC/3TC or ZDV/3TC. Virological suppression was achieved in 12 of the 13 (92%) antiretroviral-naïve patients within 24 weeks and in all (100%) patients within 96 weeks. In 13 of the 15 treatment-experienced patients, ritonavir-boosted lopinavir (LPV/r) was replaced with RAL because of hyperlipidemia (n = 11) and diarrhea (n = 2). A significant decrease in median total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels was observed in these patients (P < 0.01, each). No adverse event related to RAL was observed in any of the 28 patients. The RAL plus ABC/3TC or ZDV/3TC regimens were effective and safe in antiretroviral-naïve Korean HIV-infected patients, and replacing LPV/r with RAL significantly improved lipid abnormalities in patients previously treated with regimens including LPV/r.
    Download PDF (129K)
  • Nobuhito Nakajima, Masayuki Ueda, Mineo Yamazaki, Toshiyuki Takahashi, ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 320-322
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    In this study, we report the case of a 35-year-old woman with modified measles complicated by aseptic meningitis and subsequent optic neuritis. Although her initial manifestations were only flu-like symptoms without any Koplik's spots or skin rashes, virological testing confirmed an acute measles infection. Subsequently, right optic neuritis appeared after aseptic meningitis and was completely resolved following steroid pulse therapy. In general, modified measles is believed to be associated with mild symptoms and few neurological complications; however, our present observations demonstrated that modified measles can cause rapid neurological complications.
    Download PDF (137K)
  • Daniel Tena, Nora Mariela Martínez, Jesús Oteo, David S& ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 323-326
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Here we describe the clinical, microbiological, epidemiological, and molecular characterization of an outbreak of multidrug-resistant Acinetobacter baumannii (MRAB) involving 5 patients admitted to the internal medicine ward of our hospital. Over a 6-week period, 5 MRAB isolates were recovered from 5 patients, including 1 with fatal meningitis, 3 with skin and soft tissue infections, and 1 with respiratory colonization. One sample obtained during environmental monitoring in the ward was A. baumannii-positive. According to the pulsed-field gel electrophoresis typing results, the strains isolated from all patients and the environmental sample belonged to a single clone, identified as ST79 by multilocus sequence typing. The blaOXA-24 and blaOXA-51 carbapenemases were detected in all isolates. Four patients died, but only the death of the meningitis patient was probably related to the A. baumannii infection. The infection source was probably the hands of the healthcare workers because the outbreak strain was isolated from the surface of a serum container. The results of the present study revealed the importance of strict adherence to control measures by all healthcare workers because the consequences of noncompliance can be very serious.
    Download PDF (117K)
  • Sudarat Nakbanpot, Pattara Rattanawong
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 327-330
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    We report the death of an infant due to severe sepsis caused by congenital tuberculosis following treatment with antituberculous drugs and antibiotics, who was born to a mother with misdiagnosed symptomatic pulmonary tuberculosis during pregnancy. Therefore, pregnant women with chronic cough and constitutional symptoms must be examined for pulmonary tuberculosis, particularly in tuberculosis endemic areas.
    Download PDF (270K)
  • Soo-Han Lee, Byung-Hyun Chung, Won-Chang Lee
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 331-333
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    In this study, we performed a retrospective, quantitative analysis of the epidemiological aspects and risk factors of Vibrio vulnificus infections in Korea from 2001 to 2010. In a total of 588 V. vulnificus infection cases (prevalence rate, 0.12 cases/100,000 persons), 285 were fatal (case-fatality rate [CFR], 48.5%). Males were more significantly infected by V. vulnificus than females (86.1% versus 13.9%; P < 0.01), and a higher incidence of V. vulnificus infections was observed in people aged more than 40 years (95.1%; P < 0.01). Moreover, most V. vulnificus infections occurred in the unemployed (42.0%; P < 0.01). The seasonal patterns of outbreaks revealed that most outbreaks occurred in June (early summer) throughout November (the end of autumn) (99.6%; P < 0.01), and significantly more outbreaks occurred in the southern part (65.3%) of the Korean peninsula compared with those in the northern (29.4%) and central (5.3%) parts (P < 0.01). In addition, the number of V. vulnificus infections was significantly higher in rural and coastal villages (69.9%) than in urban areas (30.1%) (P < 0.01). In conclusion, because of the rapid aggravation and high CFR of V. vulnificus infections, public health education should strongly recommend avoiding raw seafood products and limited exposure to marine water during the summer.
    Download PDF (96K)
  • Ryohei Nomoto, Le Hong Thuy Tien, Tsutomu Sekizaki, Ro Osawa
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 334-336
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Susceptibilities to some antimicrobial agents and distribution of genes associated with resistance were examined in a total of 66 Streptococcus gallolyticus isolates and reference strains from various sources. All the tested bacteria were susceptible to vancomycin, penicillin G, and ampicillin. Most of the erythromycin-resistant isolates were observed in human clinical samples. Tetracycline and doxycycline resistance was prevalent in the isolates from human patients, diseased animals, and healthy broiler chickens, while the prevalence was significantly lower in the isolates from healthy mammals. All the isolates resistant to tetracycline possessed tet(M) and/or tet(L) and/or tet(O) genes. However, most isolates from healthy animals, which were susceptible to tetracycline, possessed the above-cited resistance genes, implying the potential ability for resistance under exposure to the corresponding antimicrobial agents.
    Download PDF (77K)
  • L'ubica Majtánová, Juraj Majtán, Viktor Majt&aacu ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 337-340
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Salmonella enterica serovar Typhimurium is a common cause of non-typhoid salmonellosis in humans. Since 2006, an increase in the human infections caused by U302 phage type in Slovakia has been documented and, from 2006 to 2011, a total of 291 U302 human strains were isolated. Antimicrobial susceptibility testing demonstrated that these strains had a high overall antimicrobial resistance and 244 (83.8%) of the tested strains were multidrug-resistant (MDR). The most prevalent resistance was to ampicillin, streptomycin, sulfisoxazole, and tetracycline (R-type ASSuT), which was verified in 87 (29.9%) strains. The annual rate of this resistance type varies, but the largest number of these strains were identified in 2009 and 2010. The classical pentaresistance phenotype (R-type ACSSuT), characteristic of the DT104 phage type, was found only in 40 (13.7%) U302 strains. These results suggested that although the prevalence of DT104 phage type has decreased, ASSuT as well as ACSSuT resistance markers continue to circulate. Therefore, continual surveillance of the occurrence of these and similar MDR phage types is necessary.
    Download PDF (78K)
  • Chih-Yuan Wang, Hwa-Jen Teng, Si-Jia Lee, Cheo Lin, Jhy-Wen Wu, Ho-She ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 341-344
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    We conducted a laboratory study to evaluate the efficacy of control agents against small larvae, large larvae, and pupae of Aedes aegypti to determine an appropriate larvicide regime to employ in emergency dengue control programs. The control agents included Bacillus thuringiensis var. israelensis (Bti), pyriproxyfen (an insect growth regulator), a larvicidal oil, Aquatain AMF (polydimethylsiloxane, a monomolecular film), and temephos at the recommend application dosages and rates. Our results showed that Bti, pyriproxyfen, and temephos were efficacious (100% mortality) against larvae, irrespective of the instar stage, but not against pupae of Ae. aegypti (1.5–7.8% mortality). Aquatain AMF, on the other hand, was very effective at controlling the pupal stage (100% mortality), but had limited efficacy against small larvae (38.0% mortality) and large larvae (78.0% mortality). The larvicidal oil was effective against all immature stages (93.3–100% mortality). Therefore, we concluded that for effectively interrupting the dengue transmission cycle, larvicides that kill the pupal stage (Aquatain AMF or larvicidal oil) should be included in an emergency dengue control program in addition to Bti, pyriproxyfen, or temephos.
    Download PDF (81K)
  • Keishin Sunagawa, Toshiyuki Ishige, Yosiaki Kusumi, Masatake Asano, Er ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 345-347
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    A 14-year-old girl with acute lymphocytic leukemia complained of right flank pain and fever. As her fever was prolonged, she underwent renal biopsy and was diagnosed with mucormycosis. We performed right nephrectomy, and subsequent pathological examination of her tissue specimen also detected mucormycosis. Here, we report a rare case of renal mucormycotic abscess.
    Download PDF (328K)
  • Takahiro Ohnishi, Hiroko Furusawa, Tomoya Yoshinari, Akiko Yamazaki, K ...
    Article type: Short Communication
    2013 Volume 66 Issue 4 Pages 348-350
    Published: 2013
    Released on J-STAGE: July 24, 2013
    JOURNAL FREE ACCESS
    Kudoa septempunctata is a myxosporean parasite of Paralichthys olivaceus (olive flounder) that causes more than 50 cases of foodborne illness in Japan each year. For quantitatively assessing the presence of K. septempunctata spores in the causative fish at food poisoning outbreaks, both a direct observation method using microscopy and a quantitative real-time PCR (qRT-PCR) method are officially accepted in Japan. However, lower correlations have been often noticed between the number of spores counted using the direct observation method and the DNA amount determined using the qRT-PCR method. To elucidate the cause of this discrepancy, we observed muscle tissues of infected olive flounders with K. septempunctata by transmission electron microscopy. The images demonstrated unsynchronized development of K. septempunctata spores in plasmodia found within myofibers; in other words, the plasmodium contained not only developed spores with completed shell valves but also developing spores (sporoblasts) composed of spore-forming cells without shell valves. Furthermore, the ratio between developed spores and sporoblasts varied at different parts of muscles. The direct microscopic observation method could count developed spores, whereas the qRT-PCR method could quantify the amount of not only spores but also sporoblastic cells regardless of the cellular development and differentiation. Considering that the food toxicity caused by K. septempunctata is induced by viable spores passing through the gastric environment, the direct observation method counting only developed spores is better than the qRT-PCR method for assessing the cause of foodborne illness at the outbreak as well as the risk of human illness in monitoring surveys of aquacultured or natural-water fish.
    Download PDF (579K)
Laboratory and Epidemiology Communications
ERRATUM
feedback
Top