Katsuko Okuzumi

Effect of fluconazole prophylaxis on fungal blood cultures: an autopsy-based study involving 720 patients with haematological malignancy

Summary. To investigate the utility of blood culture of invasive fungal infections in patients with haematological malignancies, an autopsy survey was conducted in 720 patients who were treated between 1980 and 1999. We identified 252 patients with invasive mycosis. These included Candida (n = 94), Aspergillus (n = 91), Zygomycetes (n = 34), Cryptococcus (n = 7), Trichosporon (n = 11), Fusarium (n = 1), and unknown fungi (n = 20). Of the 94 patients with invasive candidiasis, 20 had positive blood cultures. Of the 11 patients with invasive trichosporonosis, seven had positive blood cultures. The sensitivities of blood cultures were 1·1%, 0% and 14% for detecting invasive aspergillosis, zygomycosis and cryptococcosis respectively. Multiple regression analysis showed a significant correlation between results of Candida blood cultures and some variables, including prophylactic use of absorbable antifungals (P = 0·0181) and infection by Candida albicans (P = 0·0086). The sensitivity of blood cultures decreased when patients received antifungal chemoprophylaxis. Unless these agents are inactivated in culture bottles, conventional blood cultures might produce false‐negative results.

Multicenter Study To Evaluate Bloodstream Infection by Helicobacter cinaedi in Japan

ABSTRACT Helicobacter cinaedi has being recognized as an important human pathogen which causes bloodstream infections. Although the first case of bacteremia with this pathogen in Japan was reported in 2003, the true prevalence of H. cinaedi as a pathogen of bloodstream infections in this country is not yet known. Therefore, the aim of our study was to assess the incidence of bacteremia with H. cinaedi in Japan. We conducted a prospective, multicenter analysis in 13 hospitals during 6 months in Tokyo, Japan. Among positive blood cultures from 1 October 2003 to 31 March 2004, isolates suspected of being Helicobacter species were studied for further microbial identification. Identification of the organisms was based on their biochemical traits and the results of molecular analysis of their 16S rRNA gene sequences. A total of 16,743 blood culture samples were obtained during the study period, and 2,718 samples (17.7%) yielded positive culture results for coagulase-negative staphylococci. Among nine isolates suspected to be Helicobacter species, six isolates were finally identified as H. cinaedi. The positivity rate for H. cinaedi in blood culture was 0.06% of total blood samples and 0.22% of blood samples with any positive culture results. All patients with bacteremia with H. cinaedi were found to have no human immunodeficiency virus (HIV) infection, but many of them had complications with either malignancy, renal failure, or a history of surgical operation. Therefore, our results suggest that bacteremia with H. cinaedi is rare but can occur in compromised hosts other than those with HIV infection in Japan.

First Case of New Delhi Metallo-β-Lactamase 1–Producing Escherichia coli Infection in Japan

To the Editor—Emergence of multidrug-resistant organisms is a threat to public health, because there is limited effort devoted to the development of new antibiotics [1]. Multiple new mechanisms of resistance have been described recently, including a new type of carbapenem resistance gene, blaNDM-1, reported in 2009 [2]. Infections due to strains with blaNDM-1 have been reported in India, Pakistan, the United Kingdom, and the United States [2–4]. We report the first case, to our knowledge, of New Delhi metallo-blactamase 1 (NDM-1)–producing Escherichia coli infection in Japan. A 54-year-old Japanese man traveled to India for business in March 2009. During his trip, he developed dysarthria, blurring of his left eye, and tingling in his right upper extremity. He was admitted to a local hospital in India on 25 March 2009 with a diagnosis of Guillain–Barre syndrome, and he subsequently developed bradycardia, hypotension, and respiratory failure. He was intubated and received mechanical ventilation. Once he was deemed stable enough to travel with mechanical ventilation, he was transferred to the intensive care unit at Dokkyo Medical University Hospital in Japan on 4 April 2009. One month after the transfer, the patient developed fever, and 2 sets of blood cultures showed 2 types of E. coli simultaneously. One isolate was an extended-spectrum b lactamase (ESBL)

A Retrospective Study of Methicillin-Resistant Staphylococcus aureus Clinical Strains in Tokyo University Hospital

Staphylococcus aureus clinical strains isolated in 1982 and 1992 at Tokyo University Hospital were studied for their carriage ofmecA gene, antibiotic susceptibility patterns, toxin production, coagulase isotypes, and ribotyping patterns. ThemecA-carrying strains in 1982 were mostly producers of type-4 coagulase (21 out of 31;68%), but producers of other coagulase types (type-1,-2,-7) were also found. The degree of methicillin resistance varied but was moderate with these strains (MIC50=16; range, 0.5–512 μg/ml at 32°C with 2% NaCl), and some strains were even judged to be susceptible to methicillin in spite of their carriage ofmecA gene. In comparison,mecA-carrying strains in 1992 were mostly of single type in terms of production of type 2 coagulase (26 out of 27;96%), and high-level methicillin resistance (MIC50>-512). Clonal expansion of the coagulase type-2 strain was implicated under selective pressure of antibiotic usage during the last decade.

Fluoroquinolone enhances the mutation frequency for meropenem-selected carbapenem resistance in Pseudomonas aeruginosa, but use of the high-potency drug doripenem inhibits mutant formation.

ABSTRACT The mutation frequency for carbapenem resistance in Pseudomonas aeruginosa strains that were selected with carbapenems was enhanced in the presence of subinhibitory concentrations of fluoroquinolones. The mutants showed either a loss of OprD activity or increased mexAB-oprM expression. The highest mutant isolation frequency was obtained by selection with meropenem, while doripenem inhibited mutant growth.

Molecular emm genotyping and antibiotic susceptibility of Streptococcus dysgalactiae subsp. equisimilis isolated from invasive and non-invasive infections

To analyse the characteristics of infections caused by Streptococcus dysgalactiae subsp. equisimilis, clinical isolates (n=145) were collected at 11 medical institutions between September 2003 and October 2005. These isolates belonged to Lancefield group A (n=5), group C (n=18) or group G (n=122). Among all isolates, 42 strains were isolated from sterile samples such as blood, synovial fluid and tissue specimens from patients who were mostly over 50 years with invasive infections, and included seven cases of streptococcal toxic shock syndrome and necrotizing fasciitis. In contrast, the remaining 103 were isolated mainly from patients of all age groups with non-invasive infections such as pharyngotonsillitis. These isolates were classified into 25 types based on emm genotyping. A significant difference in emm types was observed between isolates from invasive and non-invasive infections (P<0.001): stG485, stG6792 and stG2078 predominated among isolates from invasive infections. A phylogenetic tree of complete open reading frames of emm genes in this organism showed high homology with those of Streptococcus pyogenes, but not with those of other streptococci. The presence of five different clones was estimated based on DNA profiles of isolates from invasive infections obtained by PFGE. Genes for resistance to macrolides [erm(A), three isolates; erm(B), five isolates; mef(A), seven isolates] and levofloxacin (mutations in gyrA and parC, four isolates) were identified in this organism. These results suggest the need for further nationwide surveillance of invasive infections caused by S. dysgalactiae subsp. equisimilis.

Incidence of penicillin-resistant streptococcus pneumoniae in Japan, 1993–1995

The Working Group for PRSP was organized through the participation of 40 institutions to investigate the incidence of penicillin (Pc)-resistantStreptococcus pneumoniae (PRSP) in Japan. We collected 2410S. pneumoniae clinical isolates between October 1994 and March 1995. The susceptibility to Pc, erythromycin, and minocycline was determined by an agar dilution method using Mueller-Hinton agar supplemented with 5% sheep blood. Pc-susceptibleS. pneumoniae (PSSP) were defined as bacteria for which the minimum inhibitory concentration (MIC) was ≤0.06 μg/mL; Pc-intermediateS. pneumoniae (PISP) as those for which the MIC ranged from 0.125 to 0.25 μg/mL; PRSP, as those with a MIC≥0.5μg/mL. The incidence of resistant strains including PISP and PRSP was 41.8% in 1994 and 40.8% in 1995. Logistic regression analysis showed that PRSP was significantly more frequent in infants aged 0 to 2 years old than in the general population and PSSP was significantly more frequent in elderly patients aged 60 or older. The rate of PRSP was significantly higher in the throat than in the sputum. Among 10 regions studied nationwide, PRSP was detected less frequently in the areas of Hokkaido and Hokuriku and more frequently in the areas of Chugoku, Shikoku, and Kyushu. Most PRSP were resistant to erythromycin and minocycline. PSSP serotyping using the capsule-quellung reaction indicated a number of types. In contrast, most PISP and PRSP were serotyped to types 19, 23, and 6.

In vitro Antiseptic Susceptibility of Clinical Isolates from Nosocomial Infections

To evaluate the susceptibility of a large number of strains to various antiseptics, we elaborated a simple, qualitative broth turbidity method in which we could quickly judge the efficacy visually. For this method, we prepared a modified neutralizer broth, consisting of trypticase soy broth containing 15% Tween 80, 1% soybean lecithin and 0.5% sodium thiosulfate. The susceptibilities of Serratia marcescens No. 26 to 4 antiseptics obtained from the turbidity method showed a good agreement with those obtained from the colony-counting method; the 4 antiseptics tested were povidone-iodine (PVP-I), chlorhexidine gluconate (CHG), benzalkonium chloride (BAC) and alkyldiaminoethylglycine hydrochloride (AEG). Both PVP-I and BAC had complete efficacy in 0.5 min against all isolates tested [100 isolates of S. marcescens, 103 of Klebsiella pneumoniae, 99 of Pseudomonas aeruginosa, 19 of Alcaligenes faecalis and 30 of A. xylosoxidans subsp. xylosoxydans (A. xylosoxydans)]. In contrast, the effectiveness of CHG was weak compared with PVP-I, BAC and AEG. Strong resistance against AEG was noted even after 3-min exposure in 1 isolate each of A. faecalis and A. xylosoxydans. It is concluded that the turbidity test is a simple and accurate method to evaluate susceptibility to various antiseptics and that it is suitable for a screening of a large number of strains. Among the 4 antiseptics tested, PVP-I and BAC showed a consistently high activity against all isolates, confirming PVP-I and BAC to be clinically useful antiseptics.

Evaluation of matrix-assisted laser desorption ionization-time of flight mass spectrometry for species identification of Acinetobacter strains isolated from blood cultures

The clinical relevance of Acinetobacter species, other than A. baumannii, as human pathogens has not been sufficiently assessed owing to the insufficiency of simple phenotypic clinical diagnostic laboratory tests. Infections caused by these organisms have different impacts on clinical outcome and require different treatment and management approaches. It is therefore important to correctly identify Acinetobacter species. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been introduced to identify a wide range of microorganisms in clinical laboratories, but only a few studies have examined its utility for identifying Acinetobacter species, particularly those of the non-Acinetobacter baumannii complex. We therefore evaluated MALDI-TOF MS for identification of Acinetobacter species by comparing it with sequence analysis of rpoB using 123 isolates of Acinetobacter species from blood. Of the isolates examined, we identified 106/123 (86.2%) to species, and 16/123 (13.0%) could only be identified as acinetobacters. The identity of one isolate could not be established. Of the 106 species identified, 89/106 (84.0%) were confirmed by rpoB sequence analysis, and 17/106 (16.0%) were discordant. These data indicate correct identification of 89/123 (72.4%) isolates. Surprisingly, all blood culture isolates were identified as 13 species of Acinetobacter, and the incidence of Acinetobacter pittii was unexpectedly high (42/123; 34.1%) and exceeded that of A. baumannii (22/123; 17.9%). Although the present identification rate using MALDI-TOF MS is not acceptable for species-level identification of Acinetobacter, further expansion of the database should remedy this situation.

Heterogeneously vancomycin-intermediate Staphylococcus aureus (hVISA) emerged before the clinical introduction of vancomycin in Japan: a retrospective study

Vancomycin-intermediate Staphylococcus aureus (VISA) and its precursor, heterogeneous VISA (hVISA), are increasingly the cause of vancomycin treatment failure. Prolonged glycopeptide treatment causes the emergence of these pathogens. However, we recently reported that hVISA can be generated by methicillin-resistant S. aureus (MRSA) exposure to imipenem (Katayama et al., Antimicrob Agents Chemother. 53:3190–6). We report here a retrospective prevalence study of VISA and hVISA on 750 MRSA clinical strains isolated from 31 Japanese national university hospitals in 1990, the year before the introduction of injectable vancomycin into clinical use in Japan in 1991. No VISA strain was identified, but population analysis identified 38 hVISA strains (5.1%) from 19 hospitals. We also determined the nucleotide sequences of vraSR, walRK,clpP, and rpoB genes whose mutations are known to be associated with vancomycin resistance. When compared with vancomycin-susceptible MRSA strain N315, six of the 38 hVISA strains possessed nonsynonymous mutations in vraSR, seven in walRK, and two in rpoB genes, Thirteen of 38 (34.2%) hVISA strains possessed at least one of these mutations. Results were consistent with our hypothesis that hVISA was present in Japanese hospitals before the clinical introduction of vancomycin.