Antimicrobial use and combination of resistance phenotypes in bacteraemic Escherichia coli in primary care: a study based on Japanese national data in 2018.

BACKGROUND: Antimicrobial use (AMU) in primary care is a contributing factor to the emergence of antimicrobial-resistant bacteria. We assessed the potential effects of AMU on the prevalence of a combination of resistance phenotypes in bacteraemic Escherichia coli in outpatient care settings between primary care facilities ('clinics') and hospitals. METHODS: Population-weighted total AMU calculated from the national database was expressed as DDDs per 1000 inhabitants per day (DID). National data for all routine microbiological test results were exported from the databases of a major commercial clinical laboratory, including 16 484 clinics, and the Japan Nosocomial Infections Surveillance, including 1947 hospitals. AMU and the prevalence of combinations of resistance phenotypes in bacteraemic E. coli isolates were compared between clinics and hospitals. RESULTS: The five most common bacteria isolated from patients with bacteraemia were the same in clinics, outpatient settings and inpatient settings in hospitals, with E. coli as the most frequent. Oral third-generation cephalosporins and fluoroquinolones were the top two AMU outpatient drugs, except for macrolides, and resulted in at least three times higher AMU in clinics than in hospitals. The percentage of E. coli isolates resistant to both drugs in clinics (18.7%) was 5.6% higher than that in hospitals (13.1%) (P < 10-8). CONCLUSIONS: Significant AMU, specifically of oral third-generation cephalosporins and fluoroquinolones, in clinics is associated with a higher prevalence of E. coli isolates resistant to both drugs. This study provides a basis for national interventions to reduce inappropriate AMU in primary care settings.

Nocardia sputorum sp. nov., an actinobacterium isolated from clinical specimens in Japan.

Two novel actinobacteria, designated IFM 12276T and IFM 12275, were isolated from clinical specimens in Japan, and their taxonomic positions were investigated using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strains IFM 12276 T and IFM 12275 have completely identical 16S rRNA gene sequences and were closely related to members of the genus Nocardia. The highest 16S rRNA gene sequence similarity was observed to Nocardia beijingensis (99.6 %) and Nocarida sputi (99.6 %), followed by Nocardia niwae (99.3 %) and Nocardia araoensis (99.3 %). The whole-cell hydrolysates of strains IFM 12276T and IFM 12275 contained meso-diaminopimelic acid, arabinose and galactose. The acyl type of muramic acid was N-glycolyl. The predominant isoprenoid quinone was MK-8(H4, ω-cycl.) and the principal polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. Strains IFM 12276T and IFM 12275 contained mycolic acids that co-migrated with those from the type strain of N. niwae. These chemotaxonomic features corresponded to those of the genus Nocardia. Meanwhile, the differences in some phenotypic characteristics, along with the results of average nucleotide identity and digital DNA-DNA hybridization analyses, indicated that strains IFM 12276 T and IFM 12275 should be distinguished from the recognized species of the genus Nocardia. Therefore, these strains represent a novel species of the genus Nocardia, for which the name Nocardia sputorum sp. nov. is proposed. The type strain is IFM 12276T (=NBRC 115477T=TBRC 17096T).

Emergence of Carbapenem-Resistant Providencia rettgeri and Providencia stuartii Producing IMP-Type Metallo-ß-Lactamase in Japan.

Four Providencia rettgeri isolates and one Providencia stuartii isolate were obtained from urine samples of five patients in 2018 in Japan. All of the isolates were resistant to imipenem and meropenem, and three were highly resistant to both carbapenems, with MICs of 512 µg/ml. The three highly carbapenem-resistant isolates harbored blaIMP-70, encoding a variant of IMP-1 metallo-ß-lactamase with two amino acid substitutions (Val67Phe and Phe87Val), and the other two harbored blaIMP-1 and blaIMP-11, respectively. Whole-genome sequencing revealed that an isolate harbored two copies of blaIMP-1 on the chromosome and that the other four harbored a copy of blaIMP-11 or blaIMP-70 in a plasmid. Expression of blaIMP-70 conferred carbapenem resistance in Escherichia coli Recombinant IMP-70 and an IMP-1 variant with Val67Phe but without Phe87Val had significant higher hydrolytic activities against meropenem than recombinant IMP-1, indicating that an amino acid substitution of Val67Phe affects increased activities against meropenem in IMP-70. These results suggest that Providencia spp. become more highly resistant to carbapenems by acquisition of two copies of blaIMP-1 or by mutation of blaIMP genes with amino acid substitutions, such as blaIMP-70.

Emergence of carbapenem-resistant and colistin-susceptible Enterobacter cloacae complex co-harboring blaIMP-1 and mcr-9 in Japan.

BACKGROUND: The spread of Enterobacteriaceae producing both carbapenemases and Mcr, encoded by plasmid-mediated colistin resistance genes, has become a serious public health problem worldwide. This study describes three clinical isolates of Enterobacter cloacae complex co-harboring blaIMP-1 and mcr-9 that were resistant to carbapenem but susceptible to colistin. METHODS: Thirty-two clinical isolates of E. cloacae complex non-susceptible to carbapenems were obtained from patients at 14 hospitals in Japan. Their minimum inhibitory concentrations (MICs) were determined by broth microdilution methods and E-tests. Their entire genomes were sequenced by MiSeq and MinION methods. Multilocus sequence types were determined and a phylogenetic tree constructed by single nucleotide polymorphism (SNP) alignment of whole genome sequencing data. RESULTS: All 32 isolates showed MICs of ≥2 µg/ml for imipenem and/or meropenem. Whole-genome analysis revealed that all these isolates harbored blaIMP-1, with three also harboring mcr-9. These three isolates showed low MICs of 0.125 µg/ml for colistin. In two of these isolates, blaIMP-1 and mcr-9 were present on two separate plasmids, of sizes 62 kb and 280/290 kb, respectively. These two isolates did not possess a qseBC gene encoding a two-component system, which is thought to regulate the expression of mcr-9. In the third isolate, however, both blaIMP-1 and mcr-9 were present on the chromosome. CONCLUSION: The mcr-9 is silently distributed among carbapenem-resistant E. cloacae complex isolates, of which are emerging in hospitals in Japan. To our knowledge, this is the first report of isolates of E. cloacae complex harboring both blaIMP-1 and mcr-9 in Japan.

A Novel VIM-Type Metallo-ß-Lactamase Variant, VIM-60, with Increased Hydrolyzing Activity against Fourth-Generation Cephalosporins in Pseudomonas aeruginosa Clinical Isolates in Japan.

A novel VIM-type metallo-ß-lactamase variant, VIM-60, was identified in multidrug-resistant Pseudomonas aeruginosa clinical isolates in Japan. Compared with VIM-2, VIM-60 had two amino acid substitutions (Arg228Leu and His252Arg) and higher catalytic activities against fourth-generation cephalosporins. The genetic context for blaVIM-60 was intI1-blaVIM-60-aadA1-aacA31-qacEdeltaI-sulI on the chromosome.

Pseudomonas juntendi sp. nov., isolated from patients in Japan and Myanmar.

A Gram-negative, aerobic, rod-shaped, non-spore-forming bacterium, designated as strain BML3T, was isolated from a sputum sample of a hospital patient in Japan. Strain BML3T grew at temperatures from 4 to 40 °C, in 1.0-7.0 % (w/v) NaCl and at pH 6.0-9.0. Results of phylogenetic analysis based on the sequences of housekeeping genes, including the 16S rRNA gene and rpoB, rpoD and gyrB, showed that strain BML3T was part of the Pseudomonas putida group and located close to Pseudomonas asiatica, Pseudomonas monteiliiand P. putida . Whole-genome comparisons, using average nucleotide identity and digital DNA-DNA hybridization, confirmed strain BML3T to be a distinct species among the P. putida group. Phenotypic characterization tests demonstrated that the utilization of phenylmercuric acetate could distinguish this strain from other closed species of the P. putida group. Based on genetic and phenotypic evidence, strain BML3T should be classified as a novel species, for which the name Pseudomonas juntendi sp. nov. is proposed. The type strain is BML3T (=DSM 109244T,=JCM 33395T), with a DNA G+C content of 62.66 mol %.

Microbiological and molecular epidemiological analyses of community-associated methicillin-resistant Staphylococcus aureus at a tertiary care hospital in Japan.

Molecular characterization of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is generally conducted referred to staphylococcal cassette chromosome mec (SCCmec) type IV or V. CA-MRSA is now a cause of concern since such strains have been isolated not only from individuals in a community but also from patients in healthcare settings. The aim of this study was to analyze microbiological and molecular epidemiological features of CA-MRSA strains at a Japanese tertiary care hospital using PCR based-open reading frame typing (POT). This technique allows for molecular classification into CA-MRSA (POT-CA) and hospital-associated (HA-) MRSA (POT-HA) with clonal discrimination. Clinical MRSA isolates obtained from consecutive patients between October 1, 2012 and September 30, 2013 at the hospital were analyzed in combination with the clinical definition for CA-MRSA by the Centers for Disease Control and Prevention and POT. Of 219 isolates (76 clonal groups), 64 (29.3%) were clinical-HA/POT-CA isolates (22 clonal groups). Some clones of them accumulated in this hospital and might be involved in nosocomial transmission. Virulent factors of the isolates were analyzed, and only one (1.6%) Panton-Valentine leukocidin gene positive isolate but no arginine catabolic mobile element genes positive isolate were found in clinical-HA/POT-CA. Additionally, clinical-HA/POT-CA isolates showed higher antimicrobial susceptibility than clinical-HA/POT-HA, especially to minocycline, doxycycline, and amikacin. The most frequent genotype of molecular CA-MRSA was multi-locus sequence type 5-SCCmecIV, previously not detected in Japan. Although CA-MRSA at this hospital showed low virulence and higher antimicrobial susceptibility, the risk of nosocomial infection from them should be recognized, requiring stricter infection control measures.

[A multicenter study of the antimicrobial susceptibility of Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, and Moraxella catarrhalis from community acquired infections in Saitama, Japan].

We examined regional surveillance of antimicrobial susceptibility of community acquired bacterial pathogens from patients in Saitama, Japan. The fourth-year survey was conducted in three of the period 2007-2010 (period I, 2007-2008; period II, 2008-2009; period III, 2009-2010). Antimicrobial susceptibility testing was conducted at the central reference laboratory according to the method recommended by Japanese Society of Chemotherapy using maximum 13 antibacterial agents. Susceptibility testing was evaluable with 789 strains (227 Streptococcus pneumoniae, 148 Streptococcus pyogenes, 220 Haemophilus influenzae, and 194 Moraxella catarrhalis). Ratio of penicillin-susceptible S. pneumoniae (PSSP, MIC of benzylpenicillin ≤ 0.06 µg/mL) was 43.5% (period I), 43.5% (period II) and 55.8% (period III), and those of erythromycin-sensitive and azithromycin-sensitive S. pyogenes were 100% and 65.5% (period I), 47.9% and 47.9% (period II), 29.4%, and 29.4% (period III) , respectively. Among H. influenzae, ß-lactamase-nonproducing ampicillin-resistant isolates were 34.9% (period I), 25.8% (period II), and 17.1% (period III); however, ß-lactamase-nonproducing ampicillin-intermediately resistant isolates were 19.8% (period I), 26.9% (period II), and 29.3% (period III). Regarding M. catarrhalis, macrolides showed potent activities, with MIC90s of ≤ 0.25-0.5 µg/mL, and fluoroquinolones showed strong activities, with MIC90s ≤0.03-0.125 µg/mL. The result of this survey indicated that the trends observed were similar to the results of previous nationwide surveillance.

Dissemination of 16S rRNA methylase ArmA-producing acinetobacter baumannii and emergence of OXA-72 carbapenemase coproducers in Japan.

Forty-nine clinical isolates of multidrug-resistant Acinetobacter baumannii were obtained from 12 hospitals in 7 prefectures throughout Japan. Molecular phylogenetic analysis revealed the clonal spread of A. baumannii sequence type 208 (ST208) and ST455 isolates harboring the armA gene and ST512 harboring the armA and blaOXA-72 genes. These findings show that A. baumannii isolates harboring armA are disseminated throughout Japan, and this is the first report to show that A. baumannii strains harboring blaOXA-72 and armA are emerging in hospitals in Japan.

Dissemination in Japan of multidrug-resistant Pseudomonas aeruginosa isolates producing IMP-type metallo-ß-lactamases and AAC(6')-Iae/AAC(6')-Ib.

The spread throughout Japan of antibiotic-resistance factors in multidrug-resistant (MDR) Pseudomonas aeruginosa isolates was investigated epidemiologically, using immunochromatographic assays specific for IMP-type metallo-ß-lactamases (IMPs) and aminoglycoside 6'-N-acetyltransferase [AAC(6')]-Iae and -Ib. Three hundred MDR P. aeruginosa isolates were obtained during each of two years, 2011 and 2012, from 190 hospitals in 39 prefectures in Japan. The percentage of P. aeruginosa isolates producing IMPs, AAC(6')-Iae or AAC(6')-Ib increased significantly from 170/300 (56.7%) in 2011 to 230/300 (76.7%) in 2012, with 134/170 (78.8%) in 2011 and 179/230 (77.8%) in 2012 producing both IMP and either AAC(6')-Iae or AAC(6')-Ib. The MICs of antibiotics, including cephalosporins and carbapenems, were markedly higher for isolates that did than did not produce these resistance factors. These results indicated that MDR P. aeruginosa producing IMPs, AAC(6')-Iae or AAC(6')-Ib have spread throughout Japan and that these antibiotic-resistance factors are useful markers for monitoring MDR P. aeruginosa in Japan.

[Trend of susceptibility testing of clinical isolates of Candida species from aseptic samples in hospitals in Saitama prefecture].

We investigated the susceptibility of Candida species from clinical aseptic samples, including blood, at some hospitals in Saitama prefecture. Candida spp. detected from aseptic samples in the 6 institutes in Saitama prefecture from November 2007 to July 2011 were studied. The number of isolates was 85, which are 43 (50.6%) of Candida albicans, 24 (28.2%) of Candida parapsilosis, 5 (5.9%) of Candida glabrata, 5 (5.9%) of Candida tropicalis, 4 (4.7%) of Candida guilliermondii, 2 (2.4%) of Candida fermentati, 1 (1.2%) of Candida famata and Candida lusitaniae, respectively. All isolates were susceptible to amphotericin B. However, resistant isolates against micafungin were 3 in 5 of C. glabrata. We analyzed susceptibility of Candida spp. in Saitama prefecture in the article, and our study might be useful for the fungal therapy in the region.

novel 6'-n-aminoglycoside acetyltransferase AAC(6')-Iaj from a clinical isolate of Pseudomonas aeruginosa.

Pseudomonas aeruginosa NCGM1588 has a novel chromosomal class 1 integron, In151, which includes the aac(6')-Iaj gene. The encoded protein, AAC(6')-Iaj, was found to consist of 184 amino acids, with 70% identity to AAC(6')-Ia. Escherichia coli transformed with a plasmid containing the aac(6')-Iaj gene acquired resistance to all aminoglycosides tested except gentamicin. Of note, aac(6')-Iaj contributed to the resistance to arbekacin. Thin-layer chromatography revealed that AAC(6')-Iaj acetylated all aminoglycosides tested except gentamicin. These findings indicated that AAC(6')-Iaj is a functional acetyltransferase that modifies the amino groups at the 6' positions of aminoglycosides and contributes to aminoglycoside resistance of P. aeruginosa NCGM1588, including arbekacin.

IMP-43 and IMP-44 metallo-ß-lactamases with increased carbapenemase activities in multidrug-resistant Pseudomonas aeruginosa.

Two novel IMP-type metallo-ß-lactamase variants, IMP-43 and IMP-44, were identified in multidrug-resistant Pseudomonas aeruginosa isolates obtained in medical settings in Japan. Analysis of their predicted amino acid sequences revealed that IMP-43 had an amino acid substitution (Val67Phe) compared with IMP-7 and that IMP-44 had two substitutions (Val67Phe and Phe87Ser) compared with IMP-11. The amino acid residue at position 67 is located at the end of a loop close to the active site, consisting of residues 60 to 66 in IMP-1, and the amino acid residue at position 87 forms a hydrophobic patch close to the active site with other amino acids. An Escherichia coli strain expressing blaIMP-43 was more resistant to doripenem and meropenem but not to imipenem than one expressing blaIMP-7. An E. coli strain expressing blaIMP-44 was more resistant to doripenem, imipenem and meropenem than one expressing blaIMP-11. IMP-43 had more efficient catalytic activities against all three carbapenems than IMP-7, indicating that the Val67Phe substitution contributed to increased catalytic activities against carbapenems. IMP-44 had more efficient catalytic activities against all carbapenems tested than IMP-11, as well as increased activities compared with IMP-43, indicating that both the Val67Phe and Phe87Ser substitutions contributed to increased catalytic activities against carbapenems.

Plasmids Harboring a Tandem Duplicate of blaVIM-24 in Carbapenem-Resistant ST1816 Pseudomonas aeruginosa in Japan.

The aim of this study was to clarify the biological and clinical significance of a tandem duplicate of blaVIM-24 in Pseudomonas aeruginosa ST1816 isolates. Thirteen ST1816 isolates carrying a plasmid harboring blaVIMs were obtained from two medical settings in Japan between 2016 and 2019. Complete sequencing revealed that, of the 13 plasmids, four had a tandem duplicate of blaVIM-24. These four plasmids harbored a replicon, a relaxase gene, and T4SS genes belonging to IncP-9, MOBF, and MPFT, respectively. All four plasmids transferred to PAO1 by filter mating. Cefepime marginally affected the growth of PAO1, carrying a pUCP19 harboring the tandem duplicate. Western blotting analysis showed that the relative intensity of VIM-24 metallo-ß-lactamase produced by a PAO1 transformant containing a tandem duplicate was 2.6-fold higher than that produced by a PAO1 transformant containing a single copy. These results suggest that the tandem duplicate of blaVIM-24 in plasmids may confer resistance against cefepime, enabling P. aeruginosa ST1816 strains to proliferate in hospitals in Japan.

Emergence of colistin-resistant Acinetobacter modestus harbouring the intrinsic phosphoethanolamine transferase EptA.

OBJECTIVES: Colistin-resistant Gram-negative pathogens have become a serious worldwide medical problem. This study was designed to reveal the effects of an intrinsic phosphoethanolamine transferase from Acinetobacter modestus on Enterobacterales. METHODS: A strain of colistin-resistant A. modestus was isolated from a sample of nasal secretions taken in 2019 from a hospitalised pet cat in Japan. The whole genome was sequenced by next generation sequencing, and transformants of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae harbouring the phosphoethanolamine transferase-encoding gene from A. modestus were constructed. Lipid A modification in E. coli transformants was analysed using electrospray ionization mass spectrometry. RESULTS: Sequencing of the entire genome revealed that the isolate harboured a phosphoethanolamine transferase-encoding gene, eptA_AM, on its chromosome. Transformants of E. coli, K. pneumoniae, and E. cloacae harbouring both the promoter and eptA_AM gene from A. modestus had 32-fold, 8-fold, and 4-fold higher minimum inhibitory concentrations (MICs) for colistin, respectively, than transformants harbouring a control vector. The genetic environment surrounding eptA_AM in A. modestus was similar to that surrounding eptA_AM in Acinetobacter junii and Acinetobacter venetianus. Electrospray ionization mass spectrometry analysis revealed that EptA_AM modified lipid A in Enterobacterales. CONCLUSION: This is the first report to describe the isolation of an A. modestus strain in Japan and show that its intrinsic phosphoethanolamine transferase, EptA_AM, contributes to colistin resistance in Enterobacterales and A. modestus.

Molecular epidemiology of carbapenem-non-susceptible Acinetobacter baumannii in Japan.

OBJECTIVES: Acinetobacter baumannii presents a clinical challenge when it is non-susceptible to carbapenems. The prevalence of carbapenem-non-susceptible A. baumannii in Japan is unclear, as previous studies have been limited in scope. We investigated the spread of carbapenem-non-susceptible A. baumannii in Japan and performed a comparison with findings from overseas. METHODS: A total of 305 non-duplicate clinical isolates of Acinetobacter spp. from 176 medical facilities in all geographical regions of Japan were tested for susceptibility to antimicrobial agents by the agar dilution method. Isolates with MICs of imipenem ≥ 4 mg/L underwent PCR analysis of OXA-type ß-lactamase gene clusters and metallo-ß-lactamase genes. These isolates were further analysed by sequencing of OXA-type ß-lactamases and by multilocus sequence typing (MLST). RESULTS: Fifty-five of the 305 clinical isolates had MICs of imipenem ≥ 4 mg/L. The OXA-51-like carbapenemase gene was detected in 52 of these 55 isolates. Within the OXA-51-like gene cluster, OXA-66 was found in 43 (82.7%) of the 52 isolates. MLST identified the following sequence types (STs): ST74, ST76, ST92, ST106, ST188 and ST195 in 2 (3.8%), 2 (3.8%), 40 (76.9%), 5 (9.6%), 2 (3.8%) and 1 (1.9%) of the isolates, respectively. In particular, ST92 was found in 31 (91.2%) of the 34 A. baumannii isolates with MICs of imipenem ≥ 16 mg/L. CONCLUSIONS: This is the first report on the molecular epidemiology of A. baumannii with MICs of imipenem ≥ 4 mg/L in Japan. OXA-66 and ST92 were dominant among these isolates.

High prevalence of extended-spectrum ß-lactamases and qnr determinants in Citrobacter species from Japan: dissemination of CTX-M-2.

OBJECTIVES: Extended-spectrum ß-lactamases (ESBLs) have become a problem among AmpC-producing Enterobacteriaceae and the emergence of concomitant quinolone resistance in ß-lactamase-producing isolates poses a global threat. In this study we investigated the prevalence and regional variation of ESBLs in Japanese clinical isolates of Citrobacter spp. and analysed plasmid-mediated quinolone resistance (PMQR) determinants in ESBL-producing Citrobacter spp. METHODS: A total of 348 clinical isolates of Citrobacter spp. collected throughout Japan were studied. Screening and the boronic acid disc test were performed to detect ESBLs in Citrobacter spp. with chromosomal AmpC ß-lactamases. PCR and sequencing were done to identify ESBL and PMQR genes. For ESBL-producing Citrobacter spp., PFGE was performed using the SfiI restriction enzyme. RESULTS: The number of ESBL-producing isolates confirmed phenotypically was 67 (19.3%). The prevalence of ESBL-producing Citrobacter koseri was significantly higher (32.1%) than that of ESBL-producing Citrobacter freundii (4.6%) (P < 0.01). Moreover, the prevalence of ESBLs was notably higher among C. koseri from southern Japan (60.0%). CTX-M-2 was predominant in C. koseri. Of the ESBL-producing C. koseri analysed, 23.2% possessed PMQR determinants, and there was a significant association between qnrB4 and bla(SHV-12). The 57 ESBL-producing Citrobacter spp. possessing bla(CTX-M), bla(SHV) or bla(TEM) were divided into 18 unique PFGE types. CONCLUSIONS: This is the first report about the prevalence of PMQR determinants among ESBL-producing Citrobacter spp. from Japan. Our data suggest that ESBLs and PMQR determinants are spreading among C. koseri in Japan.

[Nationwide antimicrobial susceptibility survey of Neisseria gonorrhoeae isolates in Japan].

In a nationwide antimicrobial susceptibility survey of 494 Nesseria gonorrhoeae isolates collected from February 2008 to December 2009 in 3 regions of Japan, 112 (22.7%) were collected from western Japan (Kinki, Chugoku, Shikoku, and Kyushu), 277 (56.1%) from mid-eastern Japan (Kanto), and 105 (21.1%) from eastern Japan (Tokai, Hokuriku, Koushinetsu, Tohoku, and Hokkaido). Resistance to ciprofloxacin (CPFX) was 72.8%, to penicillin G (PCG) 19.8%, and to tetracycline (TC) 18.2%. Intermediate resistance to CPFX was 1.8%, to PCG 73.7%, and to TC 43.7%. These results indicate that both types of resistance to the 3 agents were very high. Intermediate resistance to cefixime (CFIX) was 38.1% and to cefozidim (CDZM) 13.4%. Resistance to CFIX was only 0.4% and to CDZM 0%. Susceptibility to azithromycin was 96.6%, to ceftriaxone 99.8%, and to spectinomycin 100%. No significant difference in resistance was seen to different antimicrobial agent classes tested in the 3 regions, although intermediate resistance to CFIX in western Japan was significantly higher than in mid-eastern Japan.

Nationwide surveillance of antimicrobial susceptibility of 509 rapidly growing mycobacteria strains isolated from clinical specimens in Japan.

This study aimed to identify effective treatments against rapidly growing mycobacteria (RGM) infections by investigating the minimum inhibitory concentrations (MIC) of 24 antimicrobial agents and their molecular mechanisms of resistance. In total, 509 clinical RGM isolates were identified by analyzing the sequences of three housekeeping genes (hsp65, rpoB, and sodA), and their susceptibilities to 24 antimicrobial agents were tested. We also performed sequencing analysis of antimicrobial resistance genes (rrl, rrs, gyrA, and gyrB). To identify Mycobacteroides abscessus group subspecies, we performed PCR-based typing and determined the sequevar of erm(41). We identified 15 RGM species, most of which were susceptible to amikacin and linezolid. Among these species, arbekacin and sitafloxacin had the lowest MIC among the same class of antimicrobials. The MIC of rifabutin for M. abscessus subsp. abscessus (MAB) was lower than that for M. abscessus subsp. massiliense (MMA). The proportion of MAB isolates with MIC ≤ 2 mg/L for rifabutin was significantly higher than that of MMA [MAB: 50/178 (28.1%) vs. MMA: 23/130 (17.7%); p = 0.041]. In summary, our study revealed the antimicrobial susceptibility profile of 15 RGM species isolated in Japan and indicated that arbekacin, sitafloxacin, and rifabutin may be possible therapeutic options for RGM infections.

Geographical distribution and regional differences in 532 clinical isolates of rapidly growing mycobacterial species in Japan.

Infectious diseases caused by nontuberculous mycobacteria (NTM) are increasingly becoming a major global problem. Additionally, Mycobacteroides abscessus subsp. abscessus (MAB) infections are refractory to macrolides. This study was conducted to investigate the epidemiology of rapidly growing mycobacteria (RGM) species isolated from clinical specimens in Japan and assess differences in the regional distribution of lower respiratory specimens (LRS)- and non-lower respiratory specimens (NLRS)-derived species. 532 strains (427 LRS, 92 NLRS and 15 unknown specimens) were isolated in nine areas of Japan. We collected 418 specimens from Bio Medical Laboratories (BML), Inc., and 114 specimens from 45 hospitals in Japan. Their epidemiological differences were examined according to the specimen type, region, and climate. Fifteen species were identified. The proportion of M. abscessus group (MAG) strains was significantly lower in NLRS than in LRS (35.9% vs. 68.4%). The proportion of MAG strains was higher in northern Japan than in other regions (83.7% vs. 60.5%). Variations in strain abundance among RGM species was evident in regions with a mean annual temperature below 15 °C. We conclude that the proportions of MAG strains differed between NLRS and LRS in Japan. In addition, the mean annual temperature likely influenced the distribution of RGM species.