Ryuji Kawahara

Antimicrobial Susceptibility Survey of Streptococcus pyogenes Isolated in Japan from Patients with Severe Invasive Group A Streptococcal Infections

ABSTRACT We assessed antimicrobial susceptibility against 211 Streptococcus pyogenes strains isolated from patients with severe invasive group A streptococcal infections. Overall, 3.8, 1.4, 1.4, and 0.5% of the isolates were resistant to erythromycin, clindamycin, telithromycin, and ciprofloxacin, respectively, and 10.4% had intermediate resistance to ciprofloxacin. All isolates were susceptible to ampicillin and cefotaxime.

Prevalence, antibiotic resistance, and extended-spectrum and AmpC β-lactamase productivity of Salmonella isolates from raw meat and seafood samples in Ho Chi Minh City, Vietnam.

Salmonellosis is a type of foodborne disease caused by Salmonella enterica and is a frequent cause of childhood diarrhea in Vietnam. Of particular concern is the dissemination of multidrug-resistant Salmonella, as extended-spectrum β-lactamase (ESBL)-positive isolates were recently detected in children in Vietnam. In the present study, the prevalence and antibiotic resistance of Salmonella isolates obtained from 409 raw meat and seafood samples collected between October 2012 and March 2015 from slaughterhouses, wholesale fish market, and retail markets in Ho Chi Minh City, Vietnam were examined. A high rate of Salmonella contamination was detected in the pork (69.7%), poultry (65.3%), beef (58.3%), shrimp (49.1%), and farmed freshwater fish samples (36.6%). A total of 53 Salmonella serovars were found, of which S. Rissen, S. Weltevreden, S. London, S. Anatum, S. Typhimurium, and S. Corvallis were the most prevalent. In addition, 4 monophasic S. Typhimurium strains were identified using a PCR method for the detection of a specific IS200 fragment within the fliB-fliA intergenic region. The Salmonella isolates had a high prevalence (62.2%) of resistance to antimicrobial agents, particularly tetracycline (53.3%), ampicillin (43.8%), chloramphenicol (37.5%), and trimethoprim/sulfamethoxazole (31.3%). Isolates with resistance to three or more classes of antimicrobials were found (41.1%). Especially, isolates such as S. monophasic Typhimurium, S. Schwarzengrund, S. Indiana, S. Newport, S. Saintpaul and S. Bovismorbificans exhibited resistance to 6 classes of antimicrobials (3.3%). All 7 S. Indiana strains were resistant to between 4 and 6 classes of antimicrobials, including ciprofloxacin, which is commonly used for the treatment of human Salmonella infections. Two fish isolates were confirmed to be CTX-M-55 ESBL-producing Salmonella serovars Bovismorbificans and Newport, and five CMY-2 AmpC-producing Salmonella isolates of serovars Braenderup (4) and Typhimurium (1) were detected in poultry samples. The findings from this study, which is the first report of ESBL- and AmpC-producing Salmonella isolates from food in Vietnam, indicate that multidrug-resistant Salmonella are widely disseminated not only in meats, but also in seafood, within the food distribution system of Vietnam. The presence of these multidrug-resistant strains is a public health concern and suggests that the use of antimicrobial agents in both humans and animals in Vietnam should be tightly controlled.

Dissemination of Extended-Spectrum β-Lactamase- and AmpC β-Lactamase-Producing Escherichia coli within the Food Distribution System of Ho Chi Minh City, Vietnam

To investigate the dissemination of ESBL/pAmpC-producing E. coli within the food distribution system of Ho Chi Minh City (HCMC), Vietnam, the prevalence of ESBL/pAmpC-producing E. coli strains in chicken meat, pork, beef, and fish/shrimp samples obtained from slaughterhouses, a wholesale market, and supermarkets was examined. Among the total of 330 collected food samples, ESBL/pAmpC-producing E. coli was detected in 150 samples (45.5%). The highest prevalence of these isolates was in chicken meat (76/82, 92.7%), followed by pork (32/92, 34.8%), beef (18/74, 34.3%), and fish/shrimp (24/82, 29.3%). A total of 342 strains of ESBL/pAmpC-producing E. coli were isolated from 150 positive food samples. The most prevalent genes responsible for ESBL or pAmpC activity belonged to the CTX-M-9 (110/342, 31.2%), CTX-M-1 (102/342, 29.8%), and CIT (118/342, 34.5%) groups. To our knowledge, this is the first report of the high occurrence of pAmpC (37.1%) in animal-based food in Vietnam. Among the 342 total ESBL/pAmpC-producing E. coli isolates, 276 (80.7%) were resistant to at least 6 antibiotic agents. Notably, high percentages of resistance to ciprofloxacin and fosfomycin were found in isolates from chicken (80.5% and 50.8%, resp.). These findings demonstrate that animal-based food products in HCMC represent a major reservoir of ESBL/pAmpC-producing E. coli.

Isolation and characterization of vanA genotype vancomycin-resistant Enterococcus cecorum from retail poultry in Japan

The isolation rate of high-level vancomycin-resistant enterococci (VRE) from poultry samples in Japan has increased in recent years. As this raises concerns for the potential spread of genes encoding vancomycin resistance, poultry is routinely screened for VRE. Here, we report the isolation and characterization of a vanA genotype vancomycin-resistant Enterococcus cecorum strain (E. cecorum IPHa84) from retail domestic poultry in September 2009. The species identification was performed by biochemical testing and sequencing of the 16S rRNA and manganese-dependent superoxide dismutase genes. The vancomycin and teicoplanin susceptibility tests showed that E. cecorum IPHa84 was resistant to vancomycin and susceptible to teicoplanin, demonstrating that this isolate was VanB phenotype-vanA genotype VRE. Moreover, a vanA gene cluster was found in a chromosomally encoded Tn1546-related element, which exhibited the characteristic structure of the prototype Tn1546 element, but contained eight point mutations. The vanS sequence of E. cecorum IPHa84 contained three point mutations and was 100% identical to those of VRE isolated from different broiler droppings in Japan prior to the banning of avoparcin, indicating that the Tn1546-related element may be stable in poultry production environments, even in the absence of selective pressure. The isolation of a novel enterococcal species harboring the vanA gene reconfirms that poultry can serve as a reservoir of VanA-type VRE or vancomycin resistance genes, and suggests that the transmission of these risk factors from poultry to humans through the food chain remains a potential threat in Japan.

Evaluation of streptococcal toxic shock-like syndrome caused by group B streptococcus in adults in Japan between 2009 and 2013

Infection with Streptococcus agalactiae has long been recognized in infants. In recent years, S. agalactiae is an important cause of morbidity and mortality among adults and among those with underlying medical condition. Several cases of GBS infection and more fulminant disease similar to streptococcal toxic shock syndrome have recently been reported. We report here that 19 S. agalactiae strains were isolated from streptococcal toxic shock-like syndrome cases involving adult patients in Japan between 2009 and 2013. The average age of the patients was 66.3 years. At least one underlying disease was present in 47.4% (9/19) of the patients. The most prevalent serotype among these strains was Ib. All serotype Ib strains belonged to clonal complex 10 and were ciprofloxacin resistant. In contrast, all strains were susceptible to penicillin G, ampicillin, cefazolin, cefotaxime, imipenem, panipenem, and linezolid. The characteristic type distributions of streptococcal toxic shock-like syndrome isolates differed between isolates obtained from vaginal swabs of women and infants with invasive infections.

Spontaneous mutations in Streptococcus pyogenes isolates from streptococcal toxic shock syndrome patients play roles in virulence

Streptococcus pyogenes (group A Streptococcus; GAS) is a widespread human pathogen and causes streptococcal toxic shock syndrome (STSS). STSS isolates have been previously shown to have high frequency mutations in the csrS/csrR (covS/covR) and/or rgg (ropB) genes, which are negative regulators of virulence. However, these mutations were found at somewhat low frequencies in emm1-genotyped isolates, the most prevalent STSS genotype. In this study, we sought to detect causal mutations of enhanced virulence in emm1 isolates lacking mutation(s) in the csrS/csrR and rgg genes. Three mutations associated with elevated virulence were found in the sic (a virulence gene) promoter, the csrR promoter, and the rocA gene (a csrR positive regulator). In vivo contribution of the sic promoter and rocA mutations to pathogenicity and lethality was confirmed in a GAS mouse model. Frequency of the sic promoter mutation was significantly higher in STSS emm1 isolates than in non-invasive STSS isolates; the rocA gene mutation frequency was not significantly different among STSS and non-STSS isolates. STSS emm1 isolates possessed a high frequency mutation in the sic promoter. Thus, this mutation may play a role in the dynamics of virulence and STSS pathogenesis.

Development of selective medium for IMP-type carbapenemase-producing Enterobacteriaceae in stool specimens

BackgroundIdentification of carbapenemase-producing Enterobacteriaceae (CPE) in faecal specimens is challenging. This fact is particularly critical because low-level carbapenem-resistant organisms such as IMP-producing CPE are most prevalent in Japan. We developed a modified selective medium more suitable for IMP-type CPE.MethodsFifteen reference CPE strains producing different types of β-lactamases were used to evaluate the commercially available CHROMagar KPC and chromID CARBA as well as the newly prepared MC-ECC medium (CHROMagar ECC supplemented with meropenem, cloxacillin, and ZnSO4) and M-ECC medium (CHROMagar ECC supplemented with meropenem and ZnSO4). A total of 1035 clinical samples were then examined to detect CPE using chromID CARBA and M-ECC medium.ResultsAll tested strains producing NDM-, KPC-, and OXA-48-carbapenemases were successfully cultured in the media employed. Although most of the IMP-positive strains did not grow in CHROMagar KPC, chromID CARBA, or MC-ECC, all tested strains grew on M-ECC. When faecal samples were applied to the media, M-ECC medium allowed the best growth of IMP-type CPE with a significantly higher sensitivity (99.3%) than that of chromID CARBA (13.9%).ConclusionsM-ECC medium was determined as the most favourable selective medium for the detection of IMP-type CPE as well as other types of CPE.

Bronchitis caused by Bordetella holmesii in a child with asthma misdiagnosed as mycoplasmal infection

We report a case of a bronchitis caused by Bordetella holmesii in a 2-year-old girl with asthma. The patient had a moderate fever and productive cough, and her condition was initially diagnosed as mycoplasmal bronchitis on the basis of her clinical symptoms and rapid serodiagnosis of mycoplasmal infection. She was treated with a bronchodilator and clarithromycin, which resulted in complete recovery. However, after the initial diagnosis, nucleic acid amplification tests of her sputum showed the absence of both Mycoplasma pneumoniae and Bordetella pertussis infections. Sputum culture showed the presence of a slow-growing, gram-negative bacillus in pure culture on Bordetella agar plates; the bacillus was later identified as B. holmesii. B. holmesii infection is rare in immunocompetent children; however, the organism is a true pathogen that can cause bronchitis in young children with asthma.

Risk factors for fecal carriage of IMP-6-producing Enterobacteriaceae at a long-term care hospital in Japan: A follow-up report from the northern Osaka multicentre study group

The prevalence of carbapenem-resistant Enterobacteriaceae (CRE) has been increasing at medical institutions in Japan without even noticing. Recently, we performed a point prevalence survey for CRE carriage at a medical facility in northern Osaka that demonstrated an unexpectedly high prevalence of blaIMP-6-positive CRE, particularly at long-term care hospitals (LTCH). To identify the risk factors for CRE carriage, we collected clinical data of patients at a representative LTCH. Of 140 patients who were included in this study, 27 (19.3%) were colonized with metallo-beta-lactamase (IMP-6) producers. Pulsed-field gel electrophoresis of the IMP-6 producing Enterobacteriaceae suggested a non-clonal transmission of Escherichia coli, while a clonal spread was shown for Klebsiella pneumoniae. Risk factors for CRE colonization were a longer stay at the hospital stay and a lower independence state, as measured by Norton scales. We propose that a paradigm shift in infection control, inciting a coordinated regional effort to involve LTCHs, should be discussed in the aging society of Japan.

Foodborne Outbreak of Group G Streptococcal Pharyngitis in a School Dormitory in Osaka, Japan

ABSTRACT In September 2016, 140 patients with primary symptoms of sore throat and fever were identified in a school dormitory in Osaka, Japan. Epidemiological and laboratory investigations determined that these symptomatic conditions were from a foodborne outbreak of group G streptococcus (GGS), with GGS being isolated from samples from patients, cooks, and foods. The strain of GGS was identified as Streptococcus dysgalactiae subsp. equisimilis of two emm types (stG652.0 and stC36.0). The causative food, a broccoli salad, was contaminated with the two types of S. dysgalactiae subsp. equisimilis, totaling 1.3 × 104 CFU/g. Pulsed-field gel electrophoresis (PFGE) of samples from patients, cooks, and foods produced similar band patterns among samples with the same emm type. This result suggested the possibility of exposure from the contaminated food. The average onset time was 44.9 h and the prevalence rate was 62%. This is the first report to identify the causative food of a foodborne outbreak by Streptococcus dysgalactiae subsp. equisimilis.