Skin carriage of acinetobacters in Hong Kong.

We studied the carriage of Acinetobacter spp. at five superficial sites in 79 patients from two hospitals, in 133 healthy controls from the community (medical students and new nurses), and in 198 student nurses in different classes. A total of 431 isolates from 364 positive sites of 201 subjects and 124 blood culture isolates (1997 to 1998) were genospeciated by amplified ribosomal DNA restriction analysis. Genospecies 3 was the most common species. The carriage rate of student nurses (42 of 131) was significantly lower than that of new nurses from the community (25 of 38) (chi-square test, P = 0.0004; odds ratio [OR], 4.08; 95% confidence limits, 1.78 to 9.41) but not significantly different (P = 0.1) from that of patients in the same hospital (20 of 42). Genospecies from blood cultures and subjects (acute patients and student nurses) from Prince of Wales Hospital were similar to one another but different from subjects from the community or from another hospital (chi-square test, P < 0.0001). Half of the subjects who were positive at at least two sites had different genospecies. Of the 28 sites examined, 68% showed strain variation among isolates of the same genospecies by random amplified polymorphic DNA analysis. Half of the 106 subjects who had samples taken again within 6 weeks or 6 months later were positive only once. In the 17 subjects who were positive on at least two occasions, each occasion yielded different genospecies in 13 subjects. Our results indicate that skin carriage in the majority of healthy subjects is characterized by low density, variation in genospecies and strains, short-term duration, and the typicality of a given locality.     

Surveillance of an adult intensive care unit for long-term persistence of a multi-resistant strain ofAcinetobacter baumannii

Sporadic infections withAcinetobacter spp., punctuated with prolonged outbreaks of infection involving larger numbers of patients and a particular epidemic strain ofAcinetobacter baumannii, have occurred in the adult intensive care unit (ICU) of Nottingham University Hospital since 1985. The aim of this study was to screen patients admitted to the ICU for three or more days during a non-outbreak period in 1994–1995 and to use DNA fingerprinting techniques to compare any isolates ofAcinetobacter spp. with isolates obtained from the same ICU during the previous ten years. In the present study, almost 20% of the ICU patients screened during 1994–1995 became colonized withAcinetobacter spp. The commonest species isolated from patients wasAcinetobacter baumannii; five different strains were identified by random amplified polymorphic DNA fingerprinting, including the epidemic strain responsible for outbreaks of infection in 1985–1986 and 1992–1993. Environmental sampling yieldedAcinetobacter spp. from one or more samples on four occasions;Acinetobacter radioresistens was the commonest species isolated, andAcinetobacter baumannii (not the epidemic strain) was isolated on only one occasion from the environment. The long-term persistence of a potentially epidemic strain in the ICU, even during a non-outbreak period, indicates a need for continued vigilance. Consequently, periodic patient and environmental surveillance, combined with typing of isolates, is recommended for ICUs where significant outbreaks ofAcinetobacter infection have occurred in the past.     

Serotyping of clinical isolates of Acinetobacter: serovars of genospecies 3

A total of 156 clinical isolates of genospecies 3, the second most commonly encountered member of the genus Acinetobacter at our institution, were identified with carbon source utilization tests among 400 Acinetobacter isolates. Checkerboard tube agglutination tests and reciprocal cross-absorption studies with polyclonal rabbit immune sera against heated (100 degrees C, 1 h) cells of serovar candidate strains of genospecies 3 permitted identification of 13 serovars. Minor one-way crossreactions were noted between serovars 10 and 8 and between serovars 2 and 12, respectively. Isolates of serovar 13 cross-reacted extensively one-way with serovar 2 and less so with serovars 4 and 12. Genospecies 3 serovars 3, 7, 8, and 9 cross-reacted with Acinetobacter baumannii serovars 19, 21, 6, and 15, respectively.     

Comparison of Amplified Ribosomal DNA Restriction Analysis, Random Amplified Polymorphic DNA Analysis, and Amplified Fragment Length Polymorphism Fingerprinting for Identification of Acinetobacter Genomic Species and Typing of Acinetobacter baumannii

Thirty-one strains of Acinetobacter species, including type strains of the 18 genomic species and 13 clinical isolates, were compared by amplified ribosomal DNA restriction analysis (ARDRA), random amplified polymorphic DNA analysis (RAPD), and amplified fragment length polymorphism (AFLP) fingerprinting. ARDRA, performed with five different enzymes, showed low discriminatory power for differentiating Acinetobacter at the species and strain level. The standardized commercially available RAPD kit clearly enabled the discrimination of all Acinetobacter genomic species but showed great polymorphism between isolates of Acinetobacter baumannii. AFLP fingerprinting with radioactively as well as fluorescently labelled primers showed high discriminatory power for the identification of 18 Acinetobacter genomic species and typing of 13 clinical Acinetobacter isolates. Compared to radioactive AFLP, fluorescent AFLP was technically fast and simple to perform, and it permitted analysis with an automated DNA sequencer. Fluorescent AFLP seems particularly well suited for studying the epidemiology of nosocomial infections and outbreaks caused by Acinetobacter species.     

Molecular and Antibiogram Relationships of Acinetobacter Isolates from Two Contrasting Hospitals in the United Kingdom and South Africa

 The aim of this study was to compare the molecular relationships and antibiograms of nosocomial isolates of Acinetobacter spp. from two acute-care hospitals in Nottingham, UK, and Soweto, South Africa, with different hospital infection control problems and procedures. In contrast to Nottingham, where randomly amplified polymorphic DNA fingerprinting demonstrated that a single multiresistant strain of Acinetobacter baumannii has predominated in the hospital intensive care unit over an 11-year period, the Soweto isolates formed a heterogeneous group of unrelated molecular clusters of different antibiograms, with numerous different strains of Acinetobacter baumannii, Acinetobacter sp. 3 and Acinetobacter sp. 13TU apparently being endemic throughout the Soweto hospital. The contrasting results illustrate the need to maintain exemplary infection control procedures in hospitals where high standards have been achieved and warn of what might result if such measures are diminished.     

Distribution of Acinetobacter species on human skin: comparison of phenotypic and genotypic identification methods.

At least 19 genomic species are recognized as constituting the genus Acinetobacter. However, little is known about the natural reservoirs of the various members of the genus. An epidemiological study was therefore performed to investigate the colonization with Acinetobacter spp. of the skin and mucous membranes of 40 patients hospitalized in a cardiology ward and 40 healthy controls. Single samples were obtained once from each of nine different body sites, i.e., forehead, ear, nose, throat, axilla, hand, groin, perineum, and toe web. Identification of Acinetobacter isolates was achieved by using phenotypic properties and was compared to identification by amplified ribosomal DNA restriction analysis. Selected isolates were further investigated with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, ribotyping, and DNA-DNA hybridization. Plasmid profile analysis was used for epidemiological typing. Thirty patients (75%) and 17 controls (42.5%) were found to be colonized with Acinetobacter spp., and the colonization rates of patients increased during their hospital stay. The most frequently isolated species were Acinetobacter lwoffii (47%), A. johnsonii (21%), A. radioresistens (12%), and DNA group 3 (11%). In contrast, A. baumannii and DNA group 13TU, the most important nosocomial Acinetobacter spp., were found only rarely on human skin (0.5 and 1%, respectively) and their natural habitat remains to be defined. A good correlation between phenotypic and genotypic methods for identification of Acinetobacter spp. was observed, and only two isolates could not be assigned to any of the known DNA groups.     

Differentiation of Acinetobacter calcoaceticus sensu stricto from related Acinetobacter species by electrophoretic polymorphism of malate dehydrogenase, glutamage dehydrogenase and catalase

Acinetobacter baumannii, unnamed Acinetobacter species 3 (studied by P.J.M. Bouvet and P.A.D. Grimont) and unnamed DNA group 13 (studied by I. Tjernberg and J. Ursing) are the most prevalent Acinetobacter species in hospitals. Using the identification scheme of Bouvet and Grimont, it is sometimes difficult to differentiate these species from A. calcoaceticus sensu stricto, a species of the natural environment that has seldom been found associated with human infection. Genetically identified Acinetobacter isolates belonging to A. calcoaceticus sensu stricto (n=12), A. baumannii (n=22), Acinetobacter species 3 (n=15) and DNA group 13 of Tjernberg and Ursing (n=26), Acinetobacter species 10 (n=2), Acinetobacter species 11 (n=2) and 3 strains ungrouped by DNA-DNA hybridization were investigated for electrophoretic separations of L-malate dehydrogenase (MDH), glutamate dehydrogenase (GDH) and catalase (CAT). All A. calcoaceticus sensu stricto isolates were easily differentiated from those of other species investigated by their high MDH values (relative mobility (Rf)=78), their low GDH values (Rf range: 24–28) and CAT values (Rf range: 34–42). Acinetobacter species 3 was differentiated from A. baumannii and DNA group 13 of Tjernberg and Ursing by high CAT values. A. baumannii could not be differentiated from Tjernberg and Ursing DNA group 13. Acinetobacter species 10 was clearly differentiated from Acinetobacter species 11. Once an Acinetobacter is phenotypically identified with the four closely related species investigated here, electrophoretic analysis of MDH, GDH and CAT might be a useful complement to the identification scheme of Bouvet and Grimont for accurately identifying A. calcoaceticus sensu stricto.     

Endemic and Epidemic Acinetobacter Species in a University Hospital: an 8-Year Survey

The prevalence of the currently known Acinetobacter species and related trends of antimicrobial resistance in a Dutch university hospital were studied. Between 1999 and 2006, Acinetobacter isolates from clinical samples were collected prospectively. Isolates were analyzed by amplified fragment length polymorphism fingerprinting. For species identification, a profile similarity cutoff level of 50% was used, and for strain identification, a cutoff level of 90% was used. Susceptibility for antimicrobial agents was tested by disk diffusion by following the CLSI guideline.The incidences of Acinetobacter isolates ranged from 1.7 to 3.7 per 10,000 patients per year, without a trend of increase, during the study years. Twenty different species were distinguished. Acinetobacter baumannii (27%) and Acinetobacter genomic species (gen. sp.) 3 (26%) were the most prevalent. Other species seen relatively frequently were Acinetobacter lwoffii (11%), Acinetobacter ursingii (4%), Acinetobacter johnsonii (4%), and Acinetobacter junii (3%). One large cluster of A. baumannii, involving 31 patients, and 16 smaller clusters of various species, involving in total 39 patients, with at most 5 patients in 1 cluster, occurred. Overall, 37% of the A. baumannii isolates were fully susceptible to the tested antibiotics. There was a borderline significant (P = 0.059) trend of decreasing susceptibility. A. baumannii was the Acinetobacter species causing the largest burden of multiple-antibiotic resistance and transmissions in the hospital.More than 30 named and unnamed species of Acinetobacter have been described (14), some of which are of clinical importance, including A. baumannii, Acinetobacter gen. sp. 3, and Acinetobacter gen. sp. 13TU, while other species, like A. junii, A. johnsonii, A. ursingii, and Acinetobacter schindleri, can also incidentally be associated with infections (8). Much attention has been paid to outbreaks caused by acinetobacters (28), which in most cases are caused by A. baumannii (15, 23). Notably, in diagnostic microbiology, isolates identified as A. baumannii may also include the closely related species Acinetobacter gen. sp. 3 or Acinetobacter gen. sp. 13TU. Bacteria belonging to other Acinetobacter species are frequently not further identified as or designated Acinetobacter species, as this would require genotypic methods that are usually not available in clinical diagnostic microbiology. These difficulties in identification explain why, overall, not much is known about the occurrences of the different Acinetobacter species in the hospital.The aim of the present study was to determine the prevalences of the currently known Acinetobacter species and related trends of antimicrobial resistance in our hospital through the years. To this aim, we identified all available Acinetobacter isolates obtained from our hospital in the period between 1999 and 2006 to the species level by amplified fragment length polymorphism (AFLP) analysis, a well-validated method for Acinetobacter species identification (7, 8). Furthermore, we tested the susceptibilities of the isolates to antibiotics and used AFLP analysis to assess strain relatedness as an indication of transmission of strains in the hospital.     

Application of a microsphere-based array for rapid identification of Acinetobacter spp. with distinct antimicrobial susceptibilities

Acinetobacter spp. have emerged as important nosocomial and multidrug-resistant pathogens in the last decade. A. calcoaceticus, A. baumannii, Acinetobacter genospecies 3, and Acinetobacter genospecies 13TU are genetically closely related and are referred to as the A. calcoaceticus-A. baumannii complex (ACB complex). Distinct Acinetobacter spp. may be associated with differences in antimicrobial susceptibility, so it is important to identify Acinetobacter spp. at the species level. We developed a microsphere-based array that combines an allele-specific primer extension assay and microsphere hybridization for the identification of Acinetobacter spp. This assay can discriminate the 13 different Acinetobacter spp. in less than 8.5 h, and it has high specificity without causing cross-reactivity with 14 other common nosocomial bacterial species. The sensitivity of this assay was 100 A. baumannii cells per ml of blood, and it could discriminate multiple species in various mixture ratios. The developed assay could differentiate clinical Acinetobacter spp. isolates with a 90% identification rate. The antimicrobial susceptibility test showed that A. baumannii isolates were resistant to most antimicrobial agents other than imipenem, while the genospecies 3 and 13TU isolates were more susceptible to most antimicrobial agents, especially ciprofloxacin and ampicillin-sulbactam. These results supported the idea that this assay possibly could be applied to clinical samples and provide accurate species identification, which might be helpful for clinicians when they are treating infections caused by Acinetobacter spp.     

Molecular epidemiology of Acinetobacter baumannii and Acinetobacter nosocomialis in Germany over a 5-year period (2005–2009)

To investigate the species distribution within the Acinetobacter calcoaceticus–Acinetobacter baumannii complex and the molecular epidemiology of A. baumannii and Acinetobacter nosocomialis, 376 Acinetobacter isolates were collected prospectively from hospitalized patients at 15 medical centres in Germany during three surveillance studies conducted over a 5-year period. Species identification was performed by molecular methods. Imipenem minimum inhibitory concentrations (MIC) were determined by broth microdilution. The prevalence of the most common carbapenemase-encoding genes was investigated by oxacillinase (OXA) -multiplex polymerase chain reaction (PCR). The molecular epidemiology was investigated by repetitive sequence-based PCR (rep-PCR; DiversiLab?). Acinetobacter pittii was the most prevalent Acinetobacter species (n = 193), followed by A. baumannii (n = 140), A. calcoaceticus (n = 10) and A. nosocomialis (n = 8). The majority of A. baumannii was represented by sporadic isolates (n = 70, 50%) that showed unique rep-PCR patterns, 25 isolates (18%) clustered with one or two other isolates, and only 45 isolates (32%) belonged to one of the previously described international clonal lineages. The most prevalent clonal lineage was international clone (IC) 2 (n = 34) and IC 1 (n = 6). According to CLSI, 25 A. baumannii isolates were non-susceptible to imipenem (MIC ≥ 8 mg/L), all of which produced an OXA-58-like or OXA-23-like carbapenemase. The rate of imipenem susceptibility among A. baumannii isolates decreased from 96% in 2005 to 76% in 2009. All other Acinetobacter isolates were susceptible to imipenem. The population structure of carbapenem-susceptible A. baumannii in Germany is highly diverse. Imipenem non-susceptibility was strongly associated with the clonal lineages IC 2 and IC 1. These data underscore the high clonality of carbapenem-resistant A. baumannii isolates.     

Evaluation of the ability of a commercial system to identifyAcinetobacter genomic species

A collection of 130Acinetobacter strains identified by DNA hybridization to 18 different genomic species was used to assess the ability of the API 20NE system (bioMérieux, France) to identifyAcinetobacter genomic species and to determine its accuracy. Fiftyeight (87%) of the 67 strains of genomic species defined in the database (version 5.1) were identified to the appropriate genomic species. TheAcinetobacter baumannii strains and theAcinetobacter haemolyticus strains were all identified correctly. Three of fiveAcinetobacter junii strains, three of eightAcinetobacter johnsonii strains, and 11 of 13Acinetobacter Iwoffii strains were also identified correctly. The 58 correctly identified strains represented 45% of the total 130 strains. Thirty-six of the 72 inappropriately identified strains were designatedAcinetobacter baumannii. Thirty-one of these 36 strains belonged to genomic species 1 (Acinetobacter calcoaceticus), 3, or 13TU. Analysis of the profiles showed that the API system does not discriminate between genomic species 1, 2, 3, and 13TU. Lumping of these groups into theAcinetobacter calcoaceticus-Acinetobacter baumannii complex in the API 20NE database would make the system considerably more accurate. Incorporation of these data into the database may improve identification of the remaining genomic species, including some that are not defined. However, the discriminative power of the tests in the API galleries is insufficient for correct identification of allAcinetobacter genomic species.     

High Frequency of Acinetobacter soli among Acinetobacter Isolates Causing Bacteremia at a Tertiary Hospital in Japan

Acinetobacter baumannii is generally the most frequently isolated Acinetobacter species. Sequence analysis techniques allow reliable identification of Acinetobacter isolates at the species level. Forty-eight clinical isolates of Acinetobacter spp. were obtained from blood cultures at Tohoku University Hospital. These isolates were identified at the species level by partial sequencing of the RNA polymerase β-subunit (rpoB), 16S rRNA, and gyrB genes. Then further characterization was done by using the PCR for detection of OXA-type β-lactamase gene clusters, metallo-β-lactamases, and carO genes. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing were also performed. The most frequent isolate was Acinetobacter soli (27.1%). Six of the 13 A. soli isolates were carbapenem nonsusceptible, and all of these isolates produced IMP-1. PFGE revealed that the 13 A. soli isolates were divided into 8 clusters. This study demonstrated that A. soli accounted for a high proportion of Acinetobacter isolates causing bacteremia at a Japanese tertiary hospital. Non-A. baumannii species were identified more frequently than A. baumannii and carbapenem-nonsusceptible isolates were found among the non-A. baumannii strains. These results emphasize the importance of performing epidemiological investigations of Acinetobacter species.     

Comparison of the Vitek 2, MicroScan,and Etest Methods with the Agar Dilution Method in Assessing Colistin Susceptibility of Bloodstream Isolates of Acinetobacter Species from a Korean University Hospital

We evaluated three commercial colistin susceptibility testing methods using 213 bloodstream Acinetobacter isolates identified by gene sequencing. Compared to the agar dilution reference method, excellent categorical agreements (both 99.1%) were observed using Vitek 2 and Etest, compared to 87.3% (95.7% for Acinetobacter baumannii and 80.7% for non-baumannii Acinetobacter isolates) using MicroScan.     

Distinct antimicrobial resistance patterns and antimicrobial resistance-harboring genes according to genomic species of Acinetobacter isolates

Using 58 isolates of Acinetobacter species recovered from a university hospital between August 2004 and March 2005, we performed genomic identification by amplified rRNA gene restriction analysis (ARDRA) and investigated the existence of metallo-beta-lactamase (MBL) producers and extended-spectrum beta-lactamase (ESBL) producers. Genomic species identification of Acinetobacter strains using ARDRA showed that 40 strains were genomic species 2 (Acinetobacter baumannii), 9 were 13 sensu Tjernberg and Ursing (13TU), 5 were Acinetobacter phenon 6/ct 13TU, and 4 were Acinetobacter genospecies 3. Among 58 strains, 13 isolates were MBL producers carrying bla(IMP-1) or bla(VIM-2) and 13 isolates were ESBL producers carrying bla(PER-1). Notably, the MBL producers were mostly 13TU, Acinetobacter phenon 6/ct 13TU, and Acinetobacter genospecies 3, which showed susceptibility to ciprofloxacin and ampicillin-sulbactam. However, 12 of 13 strains carrying bla(PER-1) were A. baumannii, showing multidrug resistance. The data revealed that the antimicrobial resistance patterns and resistance-harboring genes of Acinetobacter species are remarkably distinct according to the genomic species of Acinetobacter isolates.     

Specificity of Rabbit Antisera against Lipopolysaccharide of Acinetobacter

Acinetobacter has been reported to be involved in hospital-acquired infections with increasing frequency. However, clinical laboratories still lack simple methods that allow the accurate identification of Acinetobacter strains at the species level. For this study, proteinase K-digested whole-cell lysates from 44 clinical and environmental isolates were investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with hyperimmune rabbit sera to examine the possibility of developing a serotyping scheme based on the O antigen of Acinetobacter lipopolysaccharide (LPS). The antisera, obtained by immunization of rabbits with 13 of the heat-killed isolates investigated, were characterized by Western blotting and enzyme immunoassay by using proteinase K-digested whole-cell lysates and phenol-water-extracted LPS as antigens. In both assays, the antisera were shown to be highly specific for the homologous antigen. In addition, assignment of Acinetobacter LPS to the smooth or the rough phenotype was shown not to be reliable when it was based only on the results obtained with silver-stained gels. O-antigen reactivity, determined by Western blot analysis, was observed with 11 of the 31 isolates, most of which belonged to the species Acinetobacter baumannii (DNA group 2) and the unnamed DNA group 3. Interestingly, some O antigens were found in a DNA group different from that of the strain used for immunization. The results indicate that O serotyping of Acinetobacter strains is feasible and thus may provide a simple method for the routine identification of these opportunistic pathogens.     

Epidemiological typing and prevalence of integrons in multiresistant Acinetobacter strains

Seventy-seven Acinetobacter isolates were recovered from patients in a Korean hospital during the period from November to December 1998. The isolates were genotyped using randomly amplified polymorphic DNA (RAPD) analysis for epidemiological relationship, and investigated for antibiotic susceptibility and presence of integrons. Sixty-nine Acinetobacter baumannii isolates were distributed into five groups by RAPD profiles, with 5, 1, 60, 2 and 1 in each group. The major RAPD group of 60 isolates was further divided into six subgroups by antibiograms. Eight isolates belonging to Acinetobacter DNA group 13TU were distributed among six RAPD groups. Seventy-three of the Acinetobacter isolates were resistant to eight or more of the antibiotics tested. Integrase genes were detected in 66 of the 69 A. baumannii (96%) and in 5 of the 8 Acinetobacter DNA group 13TU isolates (63%). The intI1 and intI2 genes were found in 63 and 8 isolates, respectively. The intI3 gene was not detected. All integron-carrying isolates were resistant to multiple antibiotics. All strains isolated from more than one patient carried integrons. According to the results, the presence of integrons was significantly (p<0.01) associated with multiple antibiotic resistance and nosocomial spread in Acinetobacter strains.     

Analysis of carbapenem-resistant Acinetobacter from a tertiary care setting in North India

Multidrug-resistant (MDR) Acinetobacter baumannii is a worldwide concern as cause of serious nosocomial infections. We analysed 140 non-duplicate Acinetobacter sp. isolates from hospitalised patients in a tertiary care centre; 87% were MDR and 20% (28/140) meropenem resistant. Metallo-β-lactamase was produced by 16 of these, detected by ethylene-diamine-tetra-acetic acid disc synergy test. AmpC β-lactamase and efflux pump were present in 17 and 4 of the meropenem-resistant Acinetobacter, respectively. 9/16 MBL-positive isolates carried genes for carbapenem resistance as shown by polymerase chain reaction.     

Regional dissemination of Acinetobacter species harbouring metallo-β-lactamase genes in Japan

Metallo-β-lactamase (MBL) producers have been reported among the various Acinetobacter species worldwide. In this study, the epidemiology and molecular characteristics of carbapenemase-encoding genes and mobile elements were studied to analyse the regional dissemination of MBL genes in Acinetobacter species. From January 2001 to December 2006, 48 Acinetobacter isolates harbouring MBL genes identified from five hospitals in Kyoto and Shiga Prefecture, Japan were collected and analysed. The partial rpoB gene or the 16S-23S ribosomal RNA intergenic spacer region was sequenced to obtain a species-level identification. Molecular typing using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) was performed. Twenty-five Acinetobacter pittii isolates were divided into eight PFGE types and five sequence types (STs) using MLST. Nine Acinetobacter bereziniae isolates belonged to five PFGE types. Five Acinetobacter nosocomialis isolates were divided into two PFGE types and two STs. Three unclassified Acinetobacter species isolates were divided into two PFGE types. Eighteen of the 25 A. pittii isolates belonged to ST119 and were identified from four hospitals. The bla_IMP-19 gene was detected in 41 of 48 isolates, including all of the A. pittii ST119 isolates. The bla_IMP-1 and bla_IMP-11 genes were detected in four and three isolates, respectively. The MBL genes were all embedded within a class 1 integron as a gene cassette array: bla_IMP-19-aac(6′)-31-bla_OXA-21-aadA1, catB8-like/aacA4-bla_IMP-1 and bla_IMP-11. This study is the first report demonstrating the regional dissemination of MBL-producing Acinetobacter species. A. pittii ST119 harbouring bla_IMP-19 was widely spread throughout the Kyoto-Shiga region.     

Identification,Genotypic Relation,and Clinical Features of Colistin-Resistant Isolates of Acinetobacter Genomic Species 13BJ/14TU from Bloodstreams of Patients in a University Hospital

Colistin resistance remains rare among clinical isolates of Acinetobacter species. We noted the emergence of colistin-resistant bloodstream isolates of the Acinetobacter genomic species (GS) 13BJ/14TU from patients at a university hospital between 2003 and 2011. We report here, for the first time, the microbiological and molecular characteristics of these isolates, with clinical features of Acinetobacter GS 13BJ/14TU bacteremia. All 11 available patient isolates were correctly identified as Acinetobacter GS 13BJ/14TU using partial rpoB gene sequencing but were misidentified using the phenotypic methods Vitek 2 (mostly as Acinetobacter baumannii), MicroScan (mostly as A. baumannii/Acinetobacter haemolyticus), and the API 20 NE system (all as A. haemolyticus). Most isolates were susceptible to commonly used antibiotics, including carbapenems, but all were resistant to colistin, for which it is unknown whether the resistance is acquired or intrinsic. However, the fact that none of the patients had a history of colistin therapy strongly suggests that Acinetobacter GS 13BJ/14TU is innately resistant to colistin. The phylogenetic tree of multilocus sequence typing (MLST) showed that all 11 isolates formed a separate cluster from other Acinetobacter species and yielded five sequence types. However, pulsed-field gel electrophoresis (PFGE) revealed 11 distinct patterns, suggesting that the bacteremia had occurred sporadically. Four patients showed persistent bacteremia (6 to 17 days), and all 11 patients had excellent outcomes with cleared bacteremia, suggesting that patients with Acinetobacter GS 13BJ/14TU-associated bacteremia show a favorable outcome. These results emphasize the importance of precise species identification, especially regarding colistin resistance in Acinetobacter species. In addition, MLST offers another approach to the identification of Acinetobacter GS 13BJ/14TU, whereas PFGE is useful for genotyping for this species.     

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.