Transmission in the community of clonal Proteus mirabilis carrying VIM-1 metallo-β-lactamase

Bacteriological study and its antibiotics susceptibility pattern of Otitis Media in Iraqi patients

Otitis media is an acute upper respiratory tract infection-related inflammation of the middle ear and tympanic membrane, frequently affecting children. Typically, a subsequent bacterial infection complicates a viral infection, which ultimately causes the condition. The study aims to study the function of bacterial ear infections and its causes, as well as their resistance to medications, which was the focus of this investigation. The first axis of the research was the identification of bacterial isolates using recognized diagnostic tools, and the second axis was determining the antibiotic's resistance and sensitivity. Patients with otitis media were gathered from Al-Hakim General Hospital and Al-Sadr city hospital in Al-Najaf city between November 2020 and April 2021 for 100 clinical samples. More than 80 samples were found to be infected with bacteria. Bacterial strains found in this investigation are ( 30 ) isolates of Pseudomonas aeruginosa, (20) isolates of Klebsiella spp, (20) isolates of Proteus spp, ( 15 ) isolates of Staphylococcus aureus, (8) isolates Escherichia coli and (7) isolates Enterococcus fecalies. As part of this research, the disk diffusion method was used to assess how sensitive the test was. The results showed that Pseudomonas aeruginosa was resistant to most antibiotics, particularly the penicillin family, cephalosporin, and trimethoprim, with the existence of isolates resistant to meropenem. The investigation results varied for the quinolone, aminoglycoside, and macrolide families. Klebsiella spp. were tested for antibiotic sensitivity and found to be resistant to most antibiotics, particularly those in the penicillin family, cephalosporins, and trimethoprim. Some quinolones, aminoglycosides, and macrolides are also resistant. Proteus spp were resistant to most antibiotics, particularly the penicillin family (except for augmentin, which had some sensitive isolates) and cephalosporin (except for cefdinir and cefepime) had some susceptible isolates) and trimethoprim, in addition to the presence of isolates resistant to meropenem. There is a discrepancy in the examination results for the quinolone family. The aminoglycoside family is also highly resistant. S. aureus isolates were resistant to penicillin (except for augmentin, which some isolates were responsive to), trimethoprim, and quinolones, with the presence of isolates resistant to vancomycin. The macrolide class ( azithromycin) also has a significant resistance level. Escherichia coli is susceptible to meropenem, imipenem, and certain cephalosporin generations. Augmentin, cefepime, cephalothin, meropenem, imipenem, and azithromycin were ineffective against Enterococcus fecal. The conclusion is that Pseudomonas spp has a role in ear infections and the germs Klebsiella spp., Proteus spp., Staphylococcus aureus, Escherichia coli, and Enterococcus fecalies. Penicillin and cephalosporin resistance was seen in the majority of the identified isolates. The existence of isolates of Proteus and Pseudomonas species resistant to meropenem. Vancomycin-resistant strains of Staphylococcus aureus isolates are present. Keywords: Otitis media, Resistance antibiotic, S.aureus, P.aerginosa

Clonal outbreak caused by VIM-4-producing Proteus mirabilis in a Greek tertiary-care hospital

Carbapenem-resistant Enterobacterales have become a major public-health issue worldwide. Here we report an outbreak caused by a clonal multidrug-resistant Proteus mirabilis strain producing VIM-4 metallo-β-lactamase (MBL) and TEM-2 β-lactamase in a Greek tertiary-care hospital. From July 2015 to February 2016, 27 imipenem-resistant P. mirabilis isolates were recovered from 14 patients hospitalised in two intensive care units (ICUs) and the internal medicine department in AHEPA University Hospital, Thessaloniki. The isolates were either susceptible or resistant to meropenem and were resistant to all remaining β-lactams except aztreonam. Phenotypic and molecular analysis revealed that all of the isolates harboured a bla_VIM-4 MBL gene. Resistome analysis of a representative isolate showed the presence of an IncQ1 plasmid harbouring the bla_VIM-4 carbapenemase and bla_TEM-2 β-lactamase genes among resistance genes coding for resistance to β-lactams, aminoglycosides, trimethoprim, sulfonamides and lincosamides. Genotyping by pulsed-field electrophoresis (PFGE) revealed that the isolates were epidemiologically related. After recovery of the index carbapenemase-producing P. mirabilis clinical isolate, infection control measures were intensified in the affected departments. Rectal sampling for carbapenem-resistant bacteria was initiated on a weekly basis among patients admitted to the general ICU. The outbreak was finally interrupted 6 months later in February 2016. This is the first documentation of the bla_VIM-4 MBL gene in P. mirabilis as well as the first hospital outbreak caused by a MBL-producing P. mirabilis strain.

Genetics of Acquired Antibiotic Resistance Genes in Proteus spp

Proteus spp. are commensal Enterobacterales of the human digestive tract. At the same time, P. mirabilis is commonly involved in urinary tract infections (UTI). P. mirabilis is naturally resistant to several antibiotics including colistin and shows reduced susceptibility to imipenem. However higher levels of resistance to imipenem commonly occur in P. mirabilis isolates consecutively to the loss of porins, reduced expression of penicillin binding proteins (PBPs) PBP1a, PBP2, or acquisition of several antibiotic resistance genes, including carbapenemase genes. In addition, resistance to non-β-lactams is also frequently reported including molecules used for treating UTI infections (e.g., fluoroquinolones, nitrofurans). Emergence and spread of multidrug resistant P. mirabilis isolates, including those producing ESBLs, AmpC cephalosporinases and carbapenemases, are being more and more frequently reported. This review covers Proteus spp. with a focus on the different genetic mechanisms involved in the acquisition of resistance genes to multiple antibiotic classes turning P. mirabilis into a dreadful pandrug resistant bacteria and resulting in difficult to treat infections.

First report of extensively-drug-resistant Proteus mirabilis isolate carrying plasmid-mediated blaNDM-1 in a Tunisian intensive care unit

Emergence of the New Delhi metallo-β-lactamase (NDM-1), an Ambler class B metallo-β-lactamase able to hydrolyse all β-lactams except monobactams, constitutes a critical and increasingly important medical issue. The acquisition of bla_NDM-1 is of particular concern for Proteus mirabilis, which is intrinsically resistant to tetracycline, tigecycline and colistin, as this will make clinical treatment extremely difficult. To the authors' knowledge, this is the first report of the bla_NDM-1 gene in an extensively-drug-resistant P. mirabilis clinical isolate carrying plasmid-mediated resistance to carbapenems (bla_NDM-1), cephalosporins (bla_CMY-4), aminoglycosides (aph3 VIa and aph3 Ia) and fluoroquinolones (qnrA6).

Genetic characteristic of class 1 integrons in proteus mirabilis isolates from urine samples

Background: Proteus mirabilis is an opportunistic pathogen, commonly associated with complicated urinary tract infections (UTIs). UTIs caused by multidrug-resistant Proteus mirabilis have increased worldwide. Multidrug-resistance of Gram-negative enteric bacteria is usually associated with class 1 integrons.

Purposes: To investigate the prevalence and characterize gene cassettes of class 1 integrons in multidrug-resistant P. mirabilis

Methods: From 2006 to 2008, 314 P. mirabilis isolates from urine were collected from a regional teaching hospital. Antimicrobial resistance of the isolates was determined by disk diffusion methods. The phenotypic confirmatory test of extended-spectrum β-lactamase (ESBL) production was performed as described in the Clinical and Laboratory Standards Institute (CLSI) guideline. The genetic organization of the class 1 integron cassettes was investigated by PCR, cloning, and sequencing of the regions surrounding these genes.

Results: Seventy-nine (25%, 79/314) P. mirabilis isolates were ESBL-producing and most ESBL-producing P. mirabilis were positive for bla_CTX-M. Class 1 integrons were presented in 76 isolates (24.2%, 76/314), and were more frequently found in ESBL-positive (55/79, 70%) than ESBL-negative (21/235, 8.9%) P. mirabilis isolates. The most prevalence of the cassettes encoded resistance genes were aminoglycoside (aac(6’)-Ib, aacA7, aadAl, aadA2, and aadAla), trimethoprim (dfrAl and dfrA12) and chloramphenicol (catB3 and cmlA6). The most prevalent cassette of dfr12-orfF-aadA2 was found in 49 isolates. The cassette array aadB-catB3-oxa10-aadA1 was first found in P. mirabilis. The enterobacterial repetitive intergenic consensus (ERIC)-PCR fingerprinting patterns were detected in these 76 integron positive P. mirabilis isolates and belonged to 8 profiles.

Conclusion: This study investigated the prevalence and characterized gene cassettes of class 1 integrons in MDR P. mirabilis isolates from urine samples. The frequency of gene cassettes in P. mirabilis were partially by clonal spread of the carriers and the results could provide information for effective antimicrobial therapy and infection control.

The impact of production of extended-spectrum β-lactamases on the 28-day mortality rate of patients with Proteus mirabilis bacteremia in Korea

Background

The incidence of Proteus mirabilis antimicrobial resistance, especially that mediated by extended-spectrum β-lactamases (ESBLs), has increased. We investigated the impact of ESBL production on the mortality of patients with P. mirabilis bacteremia in Korea.

Methods

Patients diagnosed with P. mirabilis bacteremia between November 2005 and December 2013 at a 2000-bed tertiary care center in South Korea were included in this study. Phenotypic and molecular analyses were performed to assess ESBL expression. Characteristics and treatment outcomes were investigated among ESBL-producing and non-ESBL-producing P. mirabilis bacteremia groups. A multivariate analysis of 28-day mortality rates was performed to evaluate the independent impact of ESBLs.

Results

Among 62 P. mirabilis isolates from 62 patients, 14 expressed ESBLs (CTX-M, 2; TEM, 5; both, 6; other, 1), and the 28-day mortality rate of the 62 patients was 17.74%. No clinical factor was significantly associated with ESBL production. The 28-day mortality rate in the ESBL-producing group was significantly higher than that in the non-ESBL-producing group (50% vs. 8.3%, p = 0.001). A multivariate analysis showed that ESBL production (odds ratio [OR], 11.53, 95% confidence interval [CI], 2.11–63.05, p = 0.005) was independently associated with the 28-day mortality rate in patients with P. mirabilis bacteremia.

Conclusions

ESBL production is significantly associated with mortality in patients with bacteremia caused by P. mirabilis. Rapid detection of ESBL expression and prompt appropriate antimicrobial therapy are required to reduce mortality caused by P. mirabilis bacteremia.

Chromosomal Amplification of the blaOXA-58 Carbapenemase Gene in a Proteus mirabilis Clinical Isolate

Horizontal gene transfer may occur between distantly related bacteria, thus leading to genetic plasticity and in some cases to acquisition of novel resistance traits. Proteus mirabilis is an enterobacterial species responsible for human infections that may express various acquired β-lactam resistance genes, including different classes of carbapenemase genes. Here we report a Proteus mirabilis clinical isolate (strain 1091) displaying resistance to penicillin, including temocillin, together with reduced susceptibility to carbapenems and susceptibility to expanded-spectrum cephalosporins. Using biochemical tests, significant carbapenem hydrolysis was detected in P. mirabilis 1091. Since PCR failed to detect acquired carbapenemase genes commonly found in Enterobacteriaceae, we used a whole-genome sequencing approach that revealed the presence of bla_OXA-58 class D carbapenemase gene, so far identified only in Acinetobacter species. This gene was located on a 3.1-kb element coharboring a bla_AmpC-like gene. Remarkably, these two genes were bracketed by putative XerC-XerD binding sites and inserted at a XerC-XerD site located between the terminase-like small- and large-subunit genes of a bacteriophage. Increased expression of the two bla genes resulted from a 6-time tandem amplification of the element as revealed by Southern blotting. This is the first isolation of a clinical P. mirabilis strain producing OXA-58, a class D carbapenemase, and the first description of a XerC-XerD-dependent insertion of antibiotic resistance genes within a bacteriophage. This study revealed a new role for the XerC-XerD recombinase in bacteriophage biology.

Prognostic value of severity indicators of nursing-home-acquired pneumonia versus community-acquired pneumonia in elderly patients

BACKGROUND

The credibility of prognostic indicators in nursing-home-acquired pneumonia (NHAP) is not clear. We previously reported a simple prognostic indicator in community-acquired pneumonia (CAP): blood urea nitrogen to serum albumin (B/A) ratio. This retrospective study investigated the prognostic value of severity indicators in NHAP versus CAP in elderly patients.

METHODS

Patients aged ≥65 years and hospitalized because of NHAP or CAP within the previous 3 years were enrolled. Demographics, coexisting illnesses, laboratory and microbiological findings, and severity scores (confusion, urea, respiratory rate, blood pressure, and age ≥65 [CURB-65] scale; age, dehydration, respiratory failure, orientation disturbance, and pressure [A-DROP] scale; and pneumonia severity index [PSI]) were retrieved from medical records. The primary outcome was mortality within 28 days of admission.

RESULTS

In total, 138 NHAP and 307 CAP patients were enrolled. Mortality was higher in NHAP (18.1%) than in CAP (4.6%) (P<0.001). Patients with NHAP were older and had lower functional status and a higher rate of do-not-resuscitate orders, heart failure, and cerebrovascular diseases. The NHAP patients more frequently had typical bacterial pathogens. Using the receiver-operating characteristics curve for predicting mortality, the area under the curve in NHAP was 0.70 for the A-DROP scale, 0.69 for the CURB-65 scale, 0.67 for the PSI class, and 0.65 for the B/A ratio. The area under the curve in CAP was 0.73 for the A-DROP scale, 0.76 for the CURB-65 scale, 0.81 for the PSI class, and 0.83 for the B/A ratio.

CONCLUSION

Patient mortality was greater in NHAP than in CAP. Patient characteristics, coexisting illnesses, and detected pathogens differed greatly between NHAP and CAP. The existing severity indicators had less prognostic value for NHAP than for CAP.

Growing prevalence of Providencia stuartii associated with the increased usage of colistin at a tertiary health care center

From 2005 to 2009, at Detroit Medical Center, the prevalence of Providencia stuartii increased from 0.52 to 0.91/1000 patient-days (p<0.001). The use of colistin also increased (p<0.001) during the study period. The increase in the prevalence of P. stuartii was associated with an increased use of colistin (p<0.001). Facilities that frequently use colistin and tigecycline should closely monitor the prevalence of P. stuartii along with other Proteeae, since these organisms are intrinsically resistant to colistin and tigecycline.

Multidrug-resistant Proteus mirabilis bloodstream infections: risk factors and outcomes

Our aims were to identify (i) risk factors associated with the acquisition of multidrug-resistant (MDR, to 3 or more classes of antimicrobials) Proteus mirabilis isolates responsible for bloodstream infections (BSIs) and (ii) the impact on mortality of such infections. Risk factors for acquiring MDR P. mirabilis BSIs were investigated in a case-case-control study; those associated with mortality were assessed by comparing survivors and nonsurvivors in a cohort study. The population consisted of 99 adult inpatients with P. mirabilis BSIs identified by our laboratory over an 11-year period (1999 to 2009), 36 (33.3%) of which were caused by MDR strains, and the overall 21-day mortality rate was 30.3%. Acquisition of an MDR strain was independently associated with admission from a long-term care facility (odds ratio [OR], 9.78; 95% confidence interval [CI], 1.94 to 49.16), previous therapy with fluoroquinolones (OR, 5.52; 95% CI, 1.30 to 23.43) or oxyimino-cephalosporins (OR, 4.72; 95% CI, 1.31 to 16.99), urinary catheterization (OR, 3.89; 95% CI, 1.50 to 10.09), and previous hospitalization (OR, 2.68; 95% CI, 10.4 to 6.89). Patients with MDR P. mirabilis BSIs received inadequate initial antimicrobial therapy (IIAT, i.e., treatment with drugs to which the isolate displayed in vitro resistance) more frequently than those with non-MDR infections; they also had increased mortality and (for survivors) longer post-BSI-onset hospital stays. In multivariate regression analysis, 21-day mortality was associated with septic shock at BSI onset (OR, 12.97; 95% CI, 32.2 to 52.23), P. mirabilis isolates that were MDR (OR, 6.62; 95% CI, 16.4 to 26.68), and IIAT (OR, 9.85; 95% CI, 26.7 to 36.25), the only modifiable risk factor of the 3. These findings can potentially improve clinicians' ability to identify P. mirabilis BSIs likely to be MDR, thereby reducing the risk of IIAT--a major risk factor for mortality in these cases--and facilitating the prompt implementation of appropriate infection control measures.

Chromosomal integration and location on IncT plasmids of the blaCTX-M-2 gene in Proteus mirabilis clinical isolates

Analysis of five CTX-M-2-producing Proteus mirabilis isolates in Japan demonstrated that bla(CTX-M-2) was located on the chromosome in four isolates and on IncT plasmids in three isolates, including two isolates that also carried the gene on the chromosome. In all four isolates with chromosomal bla(CTX-M-2), ISEcp1 was responsible for the integration of the gene into the chromosome. Three different sites in the P. mirabilis genomic sequence were utilized as integration sites.

Dissemination of clinical isolates of Klebsiella oxytoca harboring CMY-31, VIM-1, and a New OXY-2-type variant in the community

The aim of the present study was to investigate the epidemiological link of multidrug-resistant Klebsiella oxytoca isolates causing community-onset infections among patients attending our outpatient department and to investigate the underlying resistance mechanisms. The isolates were tested by agar dilution MICs, phenotypic carbapenemase testing, enterobacterial repetitive intergenic consensus-PCR, and pulsed-field gel electrophoresis (PFGE). PCR assays and nucleotide sequencing were employed for the identification of bla gene types and the mapping of the integron-containing metallo-β-lactamase (MBL) gene. During the study period (January 2005 to April 2007), nine broad-spectrum cephalosporin-resistant K. oxytoca clinical isolates were prospectively collected from separate outpatients with urinary tract infections. In all cases, the patients had been hospitalized or exposed to health care facilities during the preceding year. Molecular typing revealed that all isolates belonged to the same K. oxytoca clonal type, which contained five PFGE subtypes. A novel chromosomal OXY-2 β-lactamase type variant (OXY-2-9) was detected in all isolates, but no mutations in the promoter region justifying bla(OXY) gene overproduction were detected. In addition, all isolates harbored the plasmidic CMY-31 (LAT-4) AmpC cephalosporinase, while three of them harbored VIM-1 MBL in a class 1 integron structure. This is the first study to present the dissemination in the community of multidrug-resistant K. oxytoca isolates causing extrahospital infections.

Multiresistant Gram-negative infections: a global perspective

PURPOSE OF REVIEW

Multiresistant Gram-negative infections are an increasing problem in hospitals and healthcare facilities worldwide. While much attention has been paid to Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus lately, the importance of Gram-negative nosocomial infections has also been recognized globally.

RECENT FINDINGS

Recent reports have described the spread of carbapenemase-producing Klebsiella pneumoniae across North America. In addition, many strains of Pseudomonas and Acinetobacter in Asia are resistant to all known antibiotics. The global epidemiology of multiresistant Gram-negative pathogens seems to vary by continent. There are very few existing agents which can be used for these pathogens and there are limited options on the horizon. This limited therapeutic armamentarium has been an impetus for novel approaches including combination therapies and increased attention to infection control and prevention efforts.

SUMMARY

Clinicians need to be aware of the rising problem of resistance in nosocomial and community-acquired Gram-negative pathogens. Novel agents are urgently needed to combat these infections and innovative infection control strategies need to be devised to protect our vulnerable patients.

Multiresistant Gram-negative bacteria: the role of high-risk clones in the dissemination of antibiotic resistance

Multilocus sequence typing reveals that many bacterial species have a clonal structure and that some clones are widespread. This underlying phylogeny was not revealed by pulsed-field gel electrophoresis, a method better suited to short-term outbreak investigation. Some global clones are multiresistant and it is easy to assume that these have disseminated from single foci. Such conclusions need caution, however, unless there is a clear epidemiological trail, as with KPC carbapenemase-positive Klebsiella pneumoniae ST258 from Greece to northwest Europe. Elsewhere, established clones may have repeatedly and independently acquired resistance. Thus, the global ST131 Escherichia coli clone most often has CTX-M-15 extended-spectrum β-lactamase (ESBL), but also occurs without ESBLs and as a host of many other ESBL types. We explore this interaction of clone and resistance for E. coli, K. pneumoniae, Acinetobacter baumannii- a species where three global lineages dominate--and Pseudomonas aeruginosa, which shows clonal diversity, but includes the relatively 'tight' serotype O12/Burst Group 4 cluster that has proved adept at acquiring resistances--from PSE-1 to VIM-1 β-lactamases--for over 20 years. In summary, 'high-risk clones' play a major role in the spread of resistance, with the risk lying in their tenacity--deriving from poorly understood survival traits--and a flexible ability to accumulate and switch resistance, rather than to constant resistance batteries.

Emerging carbapenemases: a global perspective

The celestial rise in antibiotic resistance among Gram-negative bacteria has challenged both the scientific and pharmaceutical sectors. The hallmark of this general increase is the unbridled dissemination of carbapenem resistance genes, namely KPC, OXA and metallo-β-lactamase variants. In particular, the media attention given to the NDM-1 metallo-β-lactamase has highlighted the global consequences of human behaviour on spreading antibiotic resistance.

Emergence of VIM-1 metallo-β-lactamase-producing Escherichia coli in a neonatal intensive care unit

A carbapenem-resistant Escherichia coli isolate was recovered from rectal swab of a 12-day-old female neonate, which was admitted to a Greek neonatal intensive care unit (NICU). Phenotypic testing, polymerase chain reaction assays with sequencing, and plasmid analysis revealed that the isolate harbored a plasmid-mediated bla(VIM-1) metallo-β-lactamase gene. The appearance of a metallo-β-lactamase-producing E. coli in NICU is worrisome. Further surveys are needed to determine whether such Enterobacteriaceae may also be spreading in other NICUs.

Controlling the spread of carbapenemase-producing Gram-negatives: therapeutic approach and infection control

Although the rapid spread of carbapenemase-producing Gram-negatives (CPGNs) is providing the scientific community with a great deal of information about the molecular epidemiology of these enzymes and their genetic background, data on how to treat multidrug-resistant or extended drug-resistant carbapenemase-producing Enterobacteriaceae and how to contain their spread are still surprisingly limited, in spite of the rapidly increasing prevalence of these organisms and of their isolation from patients suffering from life-threatening infections. Limited clinical experience and several in vitro synergy studies seem to support the view that antibiotic combinations should be preferred to monotherapies. But, in light of the data available to date, it is currently impossible to quantify the real advantage of drug combinations in the treatment of these infections. Comprehensive clinical studies of the main therapeutic options, broken down by pathogen, enzyme and clinical syndrome, are definitely lacking and, as carbapenemases keep spreading, are urgently needed. This spread is unveiling the substantial unpreparedness of European public health structures to face this worrisome emergency, although experiences from different countries-chiefly Greece and Israel-have shown that CPGN transmission and cross-infection can cause a substantial threat to the healthcare system. This unpreparedness also affects the treatment of individual patients and infection control policies, with dramatic scarcities of both therapeutic options and infection control measures. Although correct implementation of such measures is presumably cumbersome and expensive, the huge clinical and public health problems related to CPGN transmission, alongside the current scarcity of therapeutic options, seem to fully justify this choice.

Dispersal of carbapenemase blaVIM-1 gene associated with different Tn402 variants, mercury transposons, and conjugative plasmids in Enterobacteriaceae and Pseudomonas aeruginosa

The emergence of bla(VIM-1) within four different genetic platforms from distinct Enterobacteriaceae and Pseudomonas aeruginosa isolates in an area with a low prevalence of metallo-beta-lactamase producers is reported. Forty-three VIM-1-producing isolates (including 19 Enterobacter cloacae, 2 Escherichia coli, and 2 P. aeruginosa isolates, 18 Klebsiella pneumoniae isolate, and 2 Klebsiella oxytoca isolate) recovered from 2005 to 2007 and corresponding to 15 pulsed-field gel electrophoresis types were studied. The Enterobacteriaceae isolates corresponded to a hospital outbreak, and the P. aeruginosa isolates were sporadically recovered. The genetic context of the integrons carrying bla(VIM-1) (arbitrarily designated types A, B, C, and D) was characterized by PCR mapping based on known Tn402 and mercury transposons and further sequencing. Among Enterobacteriaceae isolates, bla(VIM-1) was part of integrons located either in an In2-Tn402 element linked to Tn21 (type A; In110-bla(VIM-1)-aacA4-aadA1) or in a Tn402 transposon lacking the whole tni module [type B; In113-bla(VIM-1)-aacA4-dhfrII (also called dfrB1)-aadA1-catB2] and the transposon was associated with an IncHI2 or IncI1 plasmid, respectively. Among P. aeruginosa isolates, bla(VIM-1) was part of a new gene cassette array located in a defective Tn402 transposon carrying either tniBDelta3 and tniA (type C; bla(VIM-1)-aadA1) or tniC and DeltatniQ (type D; bla(VIM-1)-aadB), and both Tn402 variants were associated with conjugative plasmids of 30 kb. The dissemination of bla(VIM-1) was associated with different genetic structures and bacterial hosts, depicting a complex emergence and evolutionary network scenario in our facility, Ramón y Cajal University Hospital, Madrid, Spain. Knowledge of the complex epidemiology of bla(VIM-1) is necessary to control this emerging threat.

Large dissemination of VIM-2-metallo-{beta}-lactamase-producing pseudomonas aeruginosa strains causing health care-associated community-onset infections

During a 3-year period (May 2005 to April 2008), a series of 45 outpatients presented with community-onset urinary tract infections due to carbapenem-resistant Pseudomonas aeruginosa isolates. Forty of them had a history of previous hospitalization or exposure to healthcare facilities, while the remaining five had not been previously admitted to our healthcare facilities or elsewhere within the preceding 12 months. In 18 outpatients, the carbapenem-resistant organisms caused recurrent community-onset urinary tract infections, while in three outpatients the organisms were also implicated in bacteremic episodes. All 45 single-patient P. aeruginosa isolates harbored the bla(VIM-2) metallo-beta-lactamase (MBL) gene in a common class 1 integron structure. They belonged to one predominant pulsed-field gel electrophoresis type and three sporadically detected types; two of the sporadic clonal types were identified among outpatients without previous exposure to healthcare facilities, while the predominant clonal type was also identified to cause infections in hospitalized patients. This is the first study documenting that MBL-producing P. aeruginosa isolates cause community-onset infections that are related or not with exposure to healthcare facilities. Community-onset infections in our patients most likely resulted from the nosocomial acquisition of MBL producers, followed by a prolonged digestive carriage. The high rate of recurrent infections in the community underlies the difficulty of constraining infections caused by such microorganisms in the extrahospital setting.

Infections with VIM-1 metallo-{beta}-lactamase-producing enterobacter cloacae and their correlation with clinical outcome

The aim of this study was to ascertain the incidence and clinical significance of metallo-beta-lactamases among Enterobacter strains isolated from patients with nosocomial infections. We prospectively collected data on patients with Enterobacter infection during a 13-month period. All of the strains were investigated for antibiotic susceptibility, the presence and expression of metallo-beta-lactamases, and clonality. Of 29 infections (11 involving the urinary tract, 7 pneumonias, 3 skin/soft tissue infections, 3 intra-abdominal infections, 3 bacteremias, and 2 other infections), 7 (24%) were caused by Enterobacter cloacae strains harboring a bla(VIM-1) gene associated or not with a bla(SHV12) gene. Infections caused by VIM-1-producing strains were more frequently associated with a recent prior hospitalization (P = 0.006), cirrhosis (P = 0.03), relapse of infection (P < 0.001), and more prolonged duration of antibiotic therapy (P = 0.01) than were other infections. All of the isolates were susceptible to imipenem and meropenem and had bla(VIM-1) preceded by a weak P1 promoter and inactivated P2 promoters. Most VIM-1-producing Enterobacter isolates belonged to a main clone, but four different clones were found. Multiclonal VIM-1-producing E. cloacae infections are difficult to diagnose due to an apparent susceptibility to various beta-lactams, including carbapenems, and are associated with a high relapse rate and a more prolonged duration of antibiotic therapy.

Detection of KPC-2 in a clinical isolate of Proteus mirabilis and first reported description of carbapenemase resistance caused by a KPC beta-lactamase in P. mirabilis

An isolate of Proteus mirabilis recovered from blood cultures of a diabetic patient was shown to be resistant to imipenem, meropenem, and ertapenem by disk diffusion susceptibility testing. Amplification of whole-cell and/or plasmid DNA recovered from the isolate with primers specific for the bla(KPC) carbapenemase gene produced an amplicon of the expected size which was confirmed to be bla(KPC-2) by sequence analysis. Transformation of a susceptible Escherichia coli host with plasmid preparations from the isolate generated a transformant for which the MICs of all of the carbapenems tested were increased three- to fourfold. We believe this to be the first report of carbapenem resistance in P. mirabilis caused by the acquisition of bla(KPC).