Acinetobacter pittii and Acinetobacter nosocomialis among clinical isolates of the Acinetobacter calcoaceticus-baumannii complex in Sichuan,China

Among 82 clinical isolates of the Acinetobacter calcoaceticus-baumannii complex recovered in 13 hospitals of Sichuan, China, in 2011, 13 were Acinetobacter pittii and 2 were Acinetobacter nosocomialis. Multilocus sequence typing revealed a novel sequence type (ST) of A. nosocomialis and 7 novel STs of A. pittii. Most isolates were hospital-acquired and colonized in the respiratory tract, while 6 cases with pneumonia due to A. pittii were identified. This study provided a snapshot of the local incidence of A. pittii and A. nosocomialis.     

Investigation of carbapenem-resistant Acinetobacter baumannii isolates in a district hospital in Taiwan

A total of 34 Acinetobacter baumannii isolates from a district hospital in Taiwan were identified with carbapenem-hydrolyzing oxacillinase OXA-66/OXA-51-like. In addition, 26 of 28 carbapenem-resistant isolates harbored plasmid-encoded bla_OXA-23-like genes. Twenty of 28 carbapenem-resistant isolates mapped to the major genotype cluster A of carbapenemase producer by pulsed-field gel electrophoresis.     

Prevalence and diversity of carbapenemases among imipenem-nonsusceptible Acinetobacter isolates in Korea: emergence of a novel OXA-182

Increase in multidrug-resistant Acinetobacter poses a serious problem in Korea. In this study, 190 imipenem (IPM)-nonsusceptible (NS) Acinetobacter isolates from 12 Korean hospitals in 2007 were used to determine species, prevalence, and antimicrobial susceptibility of OXA carbapenemase- and metallo-β-lactamase (MBL)-producing isolates. bla_OXA-23-like and ISAba1-asssociated bla_OXA-51-like genes were detected in 80% and 12% of 178 IPM-NS Acinetobacter baumannii isolates, respectively. A novel bla_OXA-182 was detected in 12 IPM-NS A. baumannii isolates. Twelve out of 14 MBL-producing isolates were non-baumanniiAcinetobacter. A. baumannii isolates with OXA carbapenemase were more often resistant to aminoglycosides, ciprofloxacin, and tigecycline than non-baumannii Acinetobacter isolates with MBL. Identical pulsed- field gel electrophoresis patterns were observed in 89% of A. baumannii isolates with bla_OXA-23-like gene. In conclusion, extremely rapid increase of IPM-NS A. baumannii in previous Korean studies was mainly due to clonal spread of OXA-23-producing A. baumannii isolates. A novel OXA-182 emerged in Korea.     

Antibiotic resistance determinants of multidrug-resistant Acinetobacter baumannii clinical isolates in Algeria

Antibiotic susceptibility testing was performed on 71 Acinetobacter baumannii clinical isolates, and presence of antibiotic resistance genes was screened for by PCR amplification and sequencing. Resistance rates were very high for aminoglycosides (22–80%), fluoroquinolones (>90%), and cephalosporins (>90%) but remained low for rifampin (2.8%) or null for colistin. Antibiotic resistance encoding genes detected were as follows: bla_TEM-128 gene (74.6%), aph(3′)-VI (50.7 %), aadA (63.4%), ant(2″)-I (14.1%), aac(3)-Ia (91.1%), aac(6′)-Ib (4.2%), mutation Ser83Leu in gyrA (94.4%), double mutations Ser83Leu and Ser80Leu (or Ser84Leu) in gyrA and parC (69.0%), and mutation I581N in RRDR of the rpoB gene.     

Emergence of plasmid-mediated quinolone resistance genes in clinical isolates of Acinetobacter baumannii and Pseudomonas aeruginosa in Henan,China

A total of 216 clinical isolates of Acinetobacter baumannii and Pseudomonas aeruginosa were collected from a general hospital in Henan, China, and screened for the plasmid-mediated quinolone resistance (PMQR) determinants. The presence of β-lactamase genes and mutations in quinolone resistance–determining regions were investigated among the PMQR-positive isolates.     

Distribution of AdeABC efflux system genes in genotypically diverse strains of clinical Acinetobacter baumannii

Acinetobacter baumannii has emerged as a highly problematic hospital-associated pathogen. Different mechanisms contribute to the formation of multidrug resistance in A. baumannii, including the AdeABC efflux system. Distribution of the structural and regulatory genes encoding the AdeABC efflux system among genetically diverse clinical A. baumannii strains was achieved by using PCR and pulsed-field gel electrophoresis techniques. The distribution of adeABRS genes is extremely high among our A. baumannii strains, except the adeC gene. We have observed a large proportion of strains presenting multidrug-resistance phenotype for several years. The efflux pump could be an important mechanism in these strains in resistance to antibiotics.     

Distribution of blaOXA-carrying imipenem-resistant Acinetobacter spp. in 3 hospitals in Taiwan

We investigated the molecular epidemiology and OXA-type carbapenemase genes of 83 imipenem-resistant Acinetobacter spp. collected from 2 university hospitals (hospitals A and B) and a regional hospital (hospital C) during 2007 in Taiwan. Genotyping by pulsed-field gel electrophoresis identified 51 pulsotypes. None of the pulsotypes established predominance throughout the 3 hospitals. Multiplex polymerase chain reaction of blaOXA genes showed that 100% (18/18), 91%(31/34), and 100% (31/31) of the Acinetobacter spp. collected from hospital A, B, and C, respectively, possessed blaOXA-51–like genes. None of the strains carrying blaOXA-23–like and blaOXA-24–like genes were found in hospital A. The coexistences of blaOXA-51–like/blaOXA-23–like and blaOXA-51–like/blaOXA-24–like genes detected in hospitals B and C were 26% (9/34) and 12% (4/34) and 58% (18/31) and 3% (1/31), respectively. Among blaOXA-23–like gene-carrying isolates collected from hospitals, clonal spread of strains carrying the blaOXA-23 gene was detected in the regional hospital but not the other 2 university hospitals. The results suggest that interhospital dissemination of imipenem-resistant Acinetobacter spp. was not found in these hospitals. The increasing percentage of OXA-23 in OXA-type carbapenemases in Acinetobacter spp. from the regional hospitals to medical centers deserves further attention in Taiwan.     

Evaluation of Vitek2 and BD Phoenix in antimicrobial susceptibility testing of Acinetobacter baumannii and Pseudomonas aeruginosa

The accuracy of antimicrobial susceptibility testing of Vitek2 and BD Phoenix against Acinetobacter baumannii and Pseudomonas aeruginosa was evaluated. Both systems showed overall categoric agreement of ≤90% for cefepime and ceftazidime against A. baumannii and imipenem and cefepime (and ceftazidime with Vitek2) against P. aeruginosa because of high minor error rates.     

Two distinct clones of carbapenem-resistant Acinetobacter baumannii isolates from Korean hospitals

We investigated the characteristics of 48 carbapenem-resistant Acinetobacter baumannii isolates collected from 5 tertiary care hospitals in Korea by multilocus sequencing typing, pulsed-field gel electrophoresis, and polymerase chain reaction amplification of the antimicrobial resistance determinants. We identified 2 distinct main clones of carbapenem-resistant A. baumannii isolates, which showed different antimicrobial resistance profiles and are also differentiated by the kinds of oxacillinase (OXA) carbapenemases and Acinetobacter-derived cephalosporinase (ADC) β-lactamases. One main clone, ST22:A, had 27 carbapenem-resistant isolates (56.3%), showed high polymyxin B and colistin resistances (33.3% and 37.0%, respectively), and contained both bla_{OXA-51–like} and bla_{OXA-23–like} genes and the bla_ADC-29 or bla_ADC-30 gene. In contrast, the other main clone, ST28:B, included 15 isolates (31.3%), showed complete susceptibilities to polymyxin B and colistin, and contained only the bla_{OXA-51–like} gene and bla_ADC-31 or bla_ADC-32 genes. The distribution of these main carbapenem-resistant A. baumannii clones did not relate to locality, indicating that they are widespread in Korean hospitals. In addition, we found new types of PER β-lactamases, PER-6.     

Activity of doripenem with and without levofloxacin,amikacin, and colistin against Pseudomonas aeruginosa and Acinetobacter baumannii

At 24 h, sub-MIC doripenem and levofloxacin showed synergy against 21 of 25 Pseudomonas aeruginosa strains, sub-MIC doripenem and amikacin against 22 isolates, and sub-MIC doripenem and colistin against 19 isolates. Of 25 Acinetobacter baumannii strains, sub-MIC doripenem and levofloxacin showed synergy against 11 strains at 24 h, sub-MIC doripenem and amikacin against 24 strains, and sub-MIC doripenem and colistin against all isolates.     

Characterization of multidrug-resistant Klebsiella pneumoniae from Australia carrying blaNDM-1

bla_NDM genes, encoding metallo-β-lactamases providing resistance to carbapenems, have been reported in many locations since the initial report in 2008, including in several Enterobacteriaceae isolates in Australia/New Zealand. Here, we compare 4 additional carbapenem-resistant Klebsiella pneumoniae carrying bla_NDM-1 isolated in Australia. Two are sequence type ST147, previously associated with bla_NDM in Australia and elsewhere. They carry bla_NDM-1 and different 16S rRNA methylase genes (armA or rmtC) on different conjugative plasmids, in 1 case with an IncFII_Y replicon. One isolate belongs to the globally important ST11 but did not transfer a plasmid to Escherichia coli. The fourth isolate belongs to the novel ST1068 and transferred bla_NDM-1, armA, and an IncA/C plasmid. Amplification and sequencing of ompK porin genes suggest that, unlike the case for other carbapenemase genes, ompK36 defects may not be required for NDM to cause clinically relevant levels of carbapenem resistance.     

Acinetobacter baumannii infection was decreased by the structural renovation of a medical intensive care unit

Purpose

The study aimed to determine whether improvements in intensive care unit (ICU) structural environment affect the incidence of ICU-acquired infections (IAIs), particularly those caused by multidrug-resistant pathogens.

Methods

The incidence of IAI and the number of infections caused by organisms during the 6 months immediately before ICU renovation and during the 6 months immediately after ICU renovation were compared. The observational duration was prolonged for an additional 1 year after recruiting the after-renovation data to observe if the found effect of ICU structural renovation is maintained. The relevant data were prospectively gathered.

Results

The overall IAI incidence and distribution of infection site showed no difference in both periods. In IAI-causing pathogens, no considerable difference was found between before and after renovation, except for Acinetobacter baumannii. In comparison of the major pathogens’ identification rate between the entire hospital and the renovated ICU during the study periods, only A baumannii cases in the renovated ICU significantly decreased. However, the reduction of the IAI cases by A baumannii was not sustained for more than 1 year.

Conclusions

These results suggest that structural ICU renovations only may not improve overall IAI incidence, except for transient decrease in IAI by A baumannii.     

An unusual outbreak of rotavirus genotype G2P[6] during the 2005-2006 epidemic season in Philadelphia

bla(OXA-23) and bla(OXA-66) were detected in 49 Acinetobacter baumannii isolates. These isolates were assigned to 7 subtypes by enterobacterial repetitive intergenic consensus polymerase chain reaction and 7 representative isolates were of ST92 or ST75. In most cases, the ISAba1-bla(OXA-23)-ATPaseΔ structure was identical to Tn2008. The 16-bp sequence at the left end of Tn2008 resembled the inverted repeat of ISAba1, suggesting that ISAba1 might have utilized an alternative boundary to mobilize bla(OXA-23).     

Prevalence and characteristics of aac(6′)-Ib-cr in AmpC-producing Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens: a multicenter study from Korea

We investigated the prevalence of aac(6′)-Ib-cr and its association with other resistance genes in AmpC-producing Enterobacteriaceae without any selection criteria. A total of 479 clinical isolates of Enterobacter cloacae (179), Citrobacter freundii (134), and Serratia marcescens (166) from 12 laboratories between March and July 2005 were examined. We performed polymerase chain reaction for aac(6′)-Ib, bla_OXA-1, ISEcp1, and class 1 integron. The aac(6′)-Ib-cr was further identified by digestion with BstF5I and sequencing. The aac(6′)-Ib was detected in 110 (23%) of 479 isolates, and 15 isolates (3.1%) were cr variants (8 E. cloacae, 5 C. freundii, and 2 S. marcescens). The aac(6′)-Ib-cr was significantly associated with various resistance genes (bla_OXA-1, qnrS, qnrA, bla_CTX-M-3, and bla_CTX-M-14), mobile elements (ISEcp1, ISCR1, and class 1 integron), and quinolone resistance. Eleven of 15 aac(6′)-Ib-cr producers coharbored qnr genes. Although aac(6′)-Ib-cr was uncommon in Korean AmpC producers, its association with various resistance genes and mobile elements would facilitate the dissemination of this variant.     

肺炎患者痰液分离鲍曼不动杆菌耐药基因分析

目的分析呼吸内科肺炎患者痰液分离鲍曼不动杆菌携带β-内酰胺酶基因及主动外排泵基因情况。方法收集经生化鉴定为醋酸钙-鲍曼不动杆菌复合体的菌株160株,将鲍曼不动杆菌特异性片段(Ab-ITS)的二重PCR法确认为鲍曼不动杆菌者纳入研究。用PCR法检测鲍曼不动杆菌β-内酰胺酶基因和主动外排泵基因,包括A类β-内酰胺酶(bla_TEM、bla_PER和bla_CARB)、B类β-内酰胺酶(bla_IMP和bla_VIM)、C类β-内酰胺酶(bla_ADC和bla_DHA)、D类β-内酰胺酶(bla_OXA-23、bla_OXA-24、bla_OXA-51和bla_OXA-58)和主动外排泵相关基因(adeB、adeJ、macB、emrB、emrA、abeS、abeM和craA)。以微量肉汤稀释法检测加入外排泵抑制剂羰基氰化氯苯腙(CCCP)前后,携带adeB基因鲍曼不动杆菌对亚...     

In vitro activity of doripenem alone and in multi-agent combinations against extensively drug-resistant Acinetobacter baumannii and Klebsiella pneumoniae

Carbapenems are increasingly needed to treat infections caused by drug-resistant gram-negative bacilli (GNB), but carbapenem resistance is increasing. We evaluated the activity of doripenem by broth microdilution against 96 extensively drug-resistant (XDR) Acinetobacter baumannii and Klebsiella pneumoniae isolates from patients with hospital-associated infections. All isolates were non-susceptible to doripenem, but ≥1 doripenem combination demonstrated synergy (fractional inhibitory concentration index: ≤0.5 for 2 agents, ≤0.75 for 3 agents) against 7 (15%) A. baumannii and 23 (48%) K. pneumoniae isolates; doripenem with rifampin and/or polymyxin B were most active. As doripenem has unique potential for use in prolonged infusions, suggested pharmacodynamic (PD) breakpoints range from 2–8 μg/mL; synergistic activity was found for higher proportions of XDR-GNB at higher PD breakpoints with doripenem with amikacin or with rifampin. The clinical utility of these observations requires further study, as treatment options for XDR-GNB infections are limited.     

Diversity of the blaSHV genes

We investigated the diversity of nucleotide sequences of 297 SHV-encoding genes, based on nucleotide synonymous mutations and the presence or absence of the nonsynonymous mutation T92A. The analysis of this diversity allowed us to develop and propose a classification to differentiate the nucleotide sequence variants of the bla_SHV genes.     

Characterization of carbapenem-resistant Acinetobacter baumannii in Brazil (2008–2011): countrywide spread of OXA-23–producing clones (CC15 and CC79)

The study investigated the genetic relationship of carbapenem-resistant Acinetobacter baumannii clinical isolated from inpatients during 2008–2011 from 11 Brazilian states. Antimicrobial susceptibility profile was determined by disc diffusion method and Etest. Polymerase chain reaction was applied for carbapenemase genes, and ISAba1. Isolates were subjected to pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) for molecular typing. Most of the isolates showed high resistance rates to antibiotics tested. The bla_OXA-51-like gene was found in all isolates, and 146 (94.2%) isolates were positive for bla_OXA-23-like. In the most OXA-23–producing isolates, the bla_OXA-23-like gene was accompanied by ISAba1. A total of 146 OXA-23–producing isolates were clustered into 28 genotypes by PFGE. Molecular analysis by MLST identified 13 sequence types (STs). The most prevalent PFGE profiles were designated as ST15 (CC15), ST1 (CC1), and ST79 (CC79). This study showed the widespread of clonal complexes of A. baumannii harboring the bla_OXA-23-like gene in different Brazilian states.     

In vivo emergence of colistin resistance in Acinetobacter baumannii clinical isolates of sequence type 357 during colistin treatment

This study was performed to investigate the mechanisms of in vivo acquisition of colistin resistance in A. baumannii during colistin treatment. Three colistin-susceptible/resistant pairs of A. baumannii were recovered from patients who underwent colistin treatment. All of the 6 isolates included in this study shared an identical sequence type (ST), ST375, and they showed identical SmaI-macrorestriction patterns by pulsed-field gel electrophoresis. The individual colistin-resistant isolates harbored distinct mutations in the pmrB gene. Mutations detected in the pmrB gene were Ala227Val, Pro233Ser, and frame shift from Phe26. In matrix-assisted laser desorption ionization–time of flight analysis, colistin-resistant isolates were different from their colistin-susceptible counterparts, and they showed additional distinct peaks at 1852 m/z, 1937 m/z, 1954 m/z, 1975 m/z, 2034 m/z, and 2157 m/z. In vivo selection of colistin-resistant A. baumannii occurred independently in strains of ST357 during colistin treatment, and the strains acquired colistin resistance via mutations in the pmrB gene resulting in modification of lipid A components.