Multiple intensive care unit outbreak of Acinetobacter calcoaceticus subspecies anitratus respiratory infection and colonization associated with contaminated, reusable ventilator circuits and resuscitation bags

Single-Center Experience of Control of Ventilator-Circuit-Transmitted Burkholderia cepacia Outbreak in an Intensive Care Unit

Burkholderia cepacia is an emerging nosocomial pathogen frequently associated with outbreaks, but the exact transmission route of this pathogen can at times be elusive in spite of extensive environmental investigative cultures. Active surveillance for sputum cultures was performed for all patients from September 2008 to September 2009 in an intensive care unit (ICU) with B. cepacia outbreak. With evidence of persistent positive conversion of sputum cultures (colonization) and infections among patients, discontinuing re-usable ventilator circuits was introduced. A total of 689 patients were admitted to this unit for a mean duration of 8.7 ± 7.5 days. There were 489 patients (71.0%) with a stay for one to ten days; 161 (23.4%) patients for 11 to 20 days; and 39 (5.7%) with over 20 days. In the first group, 13.5% of patients had cultures converting from negative to positive, in contrast to 66.7% in the last group (p < 0.01). With intervention of using disposable ventilator circuits since June 2009, the incidence of isolated B. cepacia decreased gradually. The estimated 30-day isolation-free probabilities of the groups before, during, one month (August 2009) after, and two months (September 2009) after this intervention were 38.5%, 47.3%, 66.5%, and 96.0%, respectively (p < 0.01). Furthermore, the effect of discontinuing reusable ventilator circuit persisted in the following 6 years; both total isolates of B. cepacia and the infection caused by it were much lower compared to the outbreak period. In summary, this six-year outbreak in a medical ICU persisted until reusable ventilator circuits were discontinued in 2009. The effect of disposable circuits on the decreased incidence of B. cepacia infection maintained in the following years.

Cerebrospinal fluid (CSF) augments metabolism and virulence expression factors in Acinetobacter baumannii

In a recent report by the Centers for Disease Control and Prevention (CDC), multidrug resistant (MDR) Acinetobacter baumannii is a pathogen described as an "urgent threat." Infection with this bacterium manifests as different diseases such as community and nosocomial pneumonia, bloodstream infections, endocarditis, infections of the urinary tract, wound infections, burn infections, skin and soft tissue infections, and meningitis. In particular, nosocomial meningitis, an unwelcome complication of neurosurgery caused by extensively-drug resistant (XDR) A. baumannii, is extremely challenging to manage. Therefore, understanding how A. baumannii adapts to different host environments, such as cerebrospinal fluid (CSF) that may trigger changes in expression of virulence factors that are associated with the successful establishment and progress of this infection is necessary. The present in-vitro work describes, the genetic changes that occur during A. baumannii infiltration into CSF and displays A. baumannii's expansive versatility to persist in a nutrient limited environment while enhancing several virulence factors to survive and persist. While a hypervirulent A. baumannii strain did not show changes in its transcriptome when incubated in the presence of CSF, a low-virulence isolate showed significant differences in gene expression and phenotypic traits. Exposure to 4% CSF caused increased expression of virulence factors such as fimbriae, pilins, and iron chelators, and other virulence determinants that was confirmed in various model systems. Furthermore, although CSF's presence did not enhance bacterial growth, an increase of expression of genes encoding transcription, translation, and the ATP synthesis machinery was observed. This work also explores A. baumannii's response to an essential component, human serum albumin (HSA), within CSF to trigger the differential expression of genes associated with its pathoadaptibility in this environment.

Aminoglycoside 6'-N-acetyltransferase Type Ib [AAC(6')-Ib]-Mediated Aminoglycoside Resistance: Phenotypic Conversion to Susceptibility by Silver Ions

Clinical resistance to amikacin and other aminoglycosides is usually due to the enzymatic acetylation of the antimicrobial molecule. A ubiquitous resistance enzyme among Gram-negatives is the aminoglycoside 6′-N-acetyltransferase type Ib [AAC(6′)-Ib], which catalyzes acetylation using acetyl-CoA as a donor substrate. Therapies that combine the antibiotic and an inhibitor of the inactivation reaction could be an alternative to treat infections caused by resistant bacteria. We previously observed that metal ions such as Zn²⁺ or Cu²⁺ in complex with ionophores interfere with the AAC(6′)-Ib-mediated inactivation of aminoglycosides and reduced resistance to susceptibility levels. Ag¹⁺ recently attracted attention as a potentiator of aminoglycosides′ action by mechanisms still in discussion. We found that silver acetate is also a robust inhibitor of the enzymatic acetylation mediated by AAC(6′)-Ib in vitro. This action seems to be independent of other mechanisms, like increased production of reactive oxygen species and enhanced membrane permeability, proposed to explain the potentiation of the antibiotic effect by silver ions. The addition of this compound to aac(6′)-Ib harboring Acinetobacter baumannii and Escherichia coli cultures resulted in a dramatic reduction of the resistance levels. Time-kill assays showed that the combination of silver acetate and amikacin was bactericidal and exhibited low cytotoxicity to HEK293 cells.

Functional Analysis of the Acinetobacter baumannii XerC and XerD Site-Specific Recombinases: Potential Role in Dissemination of Resistance Genes

Modules composed of a resistance gene flanked by Xer site-specific recombination sites, the vast majority of which were found in Acinetobacter baumannii, are thought to behave as elements that facilitate horizontal dissemination. The A. baumannii xerC and xerD genes were cloned, and the recombinant clones used to complement the cognate Escherichia coli mutants. The complemented strains supported the resolution of plasmid dimers, and, as is the case with E. coli and Klebsiella pneumoniae plasmids, the activity was enhanced when the cells were grown in a low osmolarity growth medium. Binding experiments showed that the partially purified A. baumannii XerC and XerD proteins (XerCAb and XerDAb) bound synthetic Xer site-specific recombination sites, some of them with a nucleotide sequence deduced from existing A. baumannii plasmids. Incubation with suicide substrates resulted in the covalent attachment of DNA to a recombinase, probably XerCAb, indicating that the first step in the recombination reaction took place. The results described show that XerCAb and XerDAb are functional proteins and support the hypothesis that they participate in horizontal dissemination of resistant genes among bacteria.

Carbapenemases: Transforming Acinetobacter baumannii into a Yet More Dangerous Menace

Acinetobacter baumannii is a common cause of serious nosocomial infections. Although community-acquired infections are observed, the vast majority occur in people with preexisting comorbidities. A. baumannii emerged as a problematic pathogen in the 1980s when an increase in virulence, difficulty in treatment due to drug resistance, and opportunities for infection turned it into one of the most important threats to human health. Some of the clinical manifestations of A. baumannii nosocomial infection are pneumonia; bloodstream infections; lower respiratory tract, urinary tract, and wound infections; burn infections; skin and soft tissue infections (including necrotizing fasciitis); meningitis; osteomyelitis; and endocarditis. A. baumannii has an extraordinary genetic plasticity that results in a high capacity to acquire antimicrobial resistance traits. In particular, acquisition of resistance to carbapenems, which are among the antimicrobials of last resort for treatment of multidrug infections, is increasing among A. baumannii strains compounding the problem of nosocomial infections caused by this pathogen. It is not uncommon to find multidrug-resistant (MDR, resistance to at least three classes of antimicrobials), extensively drug-resistant (XDR, MDR plus resistance to carbapenems), and pan-drug-resistant (PDR, XDR plus resistance to polymyxins) nosocomial isolates that are hard to treat with the currently available drugs. In this article we review the acquired resistance to carbapenems by A. baumannii. We describe the enzymes within the OXA, NDM, VIM, IMP, and KPC groups of carbapenemases and the coding genes found in A. baumannii clinical isolates.

Identification of Potential Virulence Factors in the Model Strain Acinetobacter baumannii A118

Acinetobacter baumannii A118, a strain isolated from the blood of an infected patient, is naturally competent and unlike most clinical strains, is susceptible to a variety of different antibiotics including those usually used for selection in genetic manipulations. These characteristics make strain A118 a convenient model for genetic studies of A. baumannii. To identify potential virulence factors, its complete genome was analyzed and compared to other A. baumannii genomes. A. baumannii A118 includes gene clusters coding for the acinetobactin and baumannoferrin iron acquisition systems. Iron-regulated expression of the BauA outer membrane receptor for ferric-acinetobactin complexes was confirmed as well as the utilization of acinetobactin. A. baumannii A118 also possesses the feoABC genes, which code for the main bacterial ferrous uptake system. The functionality of baumannoferrin was suggested by the ability of A. baumannii A118 culture supernatants to cross feed an indicator BauA-deficient strain plated on iron-limiting media. A. baumannii A118 behaved as non-motile but included the csuA/BABCDE chaperone-usher pilus assembly operon and produced biofilms on polystyrene and glass surfaces. While a known capsular polysaccharide (K) locus was identified, the outer core polysaccharide (OC) locus, which belongs to group B, showed differences with available sequences. Our results show that despite being susceptible to most antibiotics, strain A118 conserves known virulence-related traits enhancing its value as model to study A. baumannii pathogenicity.

Nosocomial bacterial infections and their antimicrobial susceptibility patterns among patients in Ugandan intensive care units: a cross sectional study

Background

The intensive care unit (ICU) admits critically ill patients requiring advanced airway, respiratory, cardiac and renal support. Despite the highly-specialized interventions, the mortality and morbidity is still high due to a number of reasons including nosocomial infections, which are the most likely complications in hospitalized patients with the rates being highest among ICU patients.

Methods

In this cross-sectional study of 111 adult patients admitted to 2 of the ICUs in Uganda, we set out to describe the commonest bacterial infections, their antimicrobial susceptibility patterns and factors associated with development of a nosocomial infection.

Results

Klebsiella pneumoniae (30%), Acinetobacter species (22%) and Staphylococcus aureus (14%) were the most frequently isolated bacteria. The prevalence of multidrug resistant bacterial species was 58%; 50% Escherichia coli and 33.3% Klebsiella pneumoniae were extended spectrum beta lactamase or AmpC beta lactamase producers and 9.1% Acinetobacter species were extensive drug resistant. Imipenem was the antibiotic with the highest susceptibility rates across most bacterial species. Institution of ventilator support (P 0.003) and severe traumatic brain injury (P 0.035) were highly associated with the development of nosocomial infections.

Conclusion

Due to the high prevalence of multi drug resistant (MDR) and extensive drug resistant bacterial species, there is a need for development of strong policies on antibiotic stewardship, antimicrobial surveillance and infection control to help guide empirical antibiotic therapy and prevent the spread of MDR bacteria and antibiotic drug resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2695-5) contains supplementary material, which is available to authorized users.

Bacterial and viral contamination of breathing circuits after extended use - an aspect of patient safety?

BACKGROUND

In the past, anaesthetic breathing circuits were identified as a source of pathogen transmission. It is still debated, whether breathing circuits combined with breathing system filters can be safely used for more than 1 day. The aim of this study was to evaluate the transmission risk of bacteria and also viruses via breathing circuits after extended use.

METHODS

The inner and outer surface of 102 breathing circuits used for 1 day and of 101 circuits used for 7 days were examined for bacteria and viruses. Additionally, 10 and 20 breathing circuits each were examined after use on patients with pulmonary virus infection and with multidrug-resistant organism (MDRO) colonisation/infection respectively. Bacteria were detected by standard microbiological procedures; PCR techniques were applied for herpes simplex virus, cytomegalovirus, influenza, parainfluenza and respiratory syncytial virus.

RESULTS

Endoluminal bacterial contamination of breathing circuits remained unchanged after 7-day vs. 1-day use (5.9% vs. 7.8%) [CI95%: -0.0886-0.0506, pnon-inferiority 0.0260]. Only outside surface contamination with bacteria belonging to environmental species or human flora increased (16.8 vs. 6.9%) [CI 95%: 0.0118 - 0.1876, pnon-inferiority 0.8660]. Viruses occurred on the patient side, but not in breathing circuits. No MDRO occurred in the 20 circuits after use on patients harbouring such germs.

CONCLUSION

Endoluminal contamination of breathing circuits with bacteria did not increase after extended use. No viruses were detected in the breathing circuits using filters. Based on our results, the extended use of ABC without exceptions appears safe, if a high level of anaesthesia workplace cleaning is secured.

The Inanimate Environment of an Intensive Care Unit as a Potential Source of Nosocomial Bacteria: Evidence for Long Survival of Acinetobacter calcoaceticus

Environmental surface and personnel hand impression cultures were obtained during 13 sampling periods in the University of Virginia Pediatric Intensive Care Unit to document potential reservoirs of nosocomial pathogens. In 78 environmental cultures Staphylococcus aureus was found eight times and gram-negative bacilli ten times. The patient chart cover was the most commonly contaminated surface. Acinetobacter calcoaceticus was found in five of ten cultures positive for gram-negative bacilli. Thirty of 59 hand cultures were positive for S aureus and gram-negative bacilli; nurses and residents had both, respiratory therapists only gram-negative bacilli, and A calcoaceticus was the most commonly isolated bacterium of potentially nosocomial significance (14/30). Laboratory investigation of bacterial survival revealed that gramnegative bacilli survived on a dry formica surface from a few hours up to three days but Acinetobacter survived up to 13 days. Since A calcoaceticus has been implicated in many nosocomial infections, its long survival on a dry surface may be an additional factor in its transmission in hospitals and suggests that more attention be paid to environmental surfaces as a source of significant nosocomial pathogens.

Antibiotic-Resistant Acinetobacter baumannii Increasing Success Remains a Challenge as a Nosocomial Pathogen

Antibiotic-resistant infectious bacteria currently imply a high risk and therefore constitute a strong challenge when treating patients in hospital settings. Characterization of these species and of particular strains is a priority for the establishment of diagnostic tests and preventive procedures. The relevance of Acinetobacter baumannii as a problematic microorganism in inpatient facilities, particularly intensive care units, has increased over time. This review aims to draw attention to (i) the historical emergence of carbapenem-resistant Acinetobacter baumannii, (ii) the current status of surveillance needs in Latin America, and (iii) recent data suggesting that A. baumannii continues to spread and evolve in hospital settings. First, we present synopsis of the series of events leading to the discovery and precise identification of this microorganism in hospital settings. Then key events in the acquisition of antibiotic-resistant genes by this microorganism are summarized, highlighting the race between new antibiotic generation and emergence of A. baumannii resistant strains. Here we review the historical development of this species as an infectious threat, the current state of its distribution, and antibiotic resistance characteristics, and we discuss future prospects for its control.

Inhibition of AAC(6')-Ib-mediated resistance to amikacin in Acinetobacter baumannii by an antisense peptide-conjugated 2',4'-bridged nucleic acid-NC-DNA hybrid oligomer

Multiresistant Acinetobacter baumannii, a common etiologic agent of severe nosocomial infections in compromised hosts, usually harbors aac(6')-Ib. This gene specifies resistance to amikacin and other aminoglycosides, seriously limiting the effectiveness of these antibiotics. An antisense oligodeoxynucleotide (ODN4) that binds to a duplicated sequence on the aac(6')-Ib mRNA, one of the copies overlapping the initiation codon, efficiently inhibited translation in vitro. An isosequential nuclease-resistant hybrid oligomer composed of 2',4'-bridged nucleic acid-NC (BNA(NC)) residues and deoxynucleotides (BNA(NC)-DNA) conjugated to the permeabilizing peptide (RXR)4XB ("X" and "B" stand for 6-aminohexanoic acid and β-alanine, respectively) (CPPBD4) inhibited translation in vitro at the same levels observed in testing ODN4. Furthermore, CPPBD4 in combination with amikacin inhibited growth of a clinical A. baumannii strain harboring aac(6')-Ib in liquid cultures, and when both compounds were used as combination therapy to treat infected Galleria mellonella organisms, survival was comparable to that seen with uninfected controls.

Draft Genome of the Multidrug-Resistant Acinetobacter baumannii Strain A155 Clinical Isolate

Acinetobacter baumannii is a bacterial pathogen with serious implications on human health, due to increasing reports of multidrug-resistant strains isolated from patients. Total DNA from the multidrug-resistant A. baumannii strain A155 clinical isolate was sequenced to greater than 65× coverage, providing high-quality contig assemblies.

Nosocomial Infection Caused by Antibiotic-Resistant Organisms in the Intensive-Care Unit

Resistance to antimicrobial agents is an evolving process, driven by the selective pressure of heavy antibiotic use in individuals living in close proximity to others. The intensive care unit (ICU), crowded with debilitated patients who are receiving broad-spectrum antibiotics and being cared for by busy physicians, nurses, and technicians, serves as an ideal environment for the emergence of antibiotic resistance. Problem pathogens presently include multiply resistant gram-negative bacilli, methicillin-resistantStaphylococcus aureus, and the recently emerged vancomycin-resistant enterococci. The prevention of antimicrobial resistance in ICUs should focus on recognition via routine unit-based sur veillance, improved compliance with handwashing and barrier precautions, and antibiotic-use policies tailored to individual units within hospitals.

Acute Emergence of Elizabethkingia meningoseptica Infection among Mechanically Ventilated Patients in a Long-Term Acute Care Facility

Objective.

To describe an outbreak of infection associated with an infrequently implicated pathogen, Elizabethkingia meningoseptica, in an increasingly prominent setting for health care of severely ill patients, the long-term acute care hospital.

Design.

Outbreak investigation.

Setting.

Long-term acute care hospital with 55 patients, most of whom were mechanically ventilated.

Methods.

We defined a case as E. meningoseptica isolated from any patient specimen source from December 2007 through April 2008, conducted an investigation of case patients, obtained environmental specimens, and performed microbiologic testing.

Results.

Nineteen patients had E. meningoseptica infection, and 8 died. All case patients had been admitted with respiratory failure that required mechanical ventilation. Among the 8 individuals who died, the time from collection of the first specimen positive for E. meningoseptica to death ranged from 6 to 43 days (median, 16 days). Environmental sampling was performed on 106 surfaces; E. meningoseptica was isolated from only one swab. Three related pulsed-field gel electrophoresis patterns were identified in patient isolates; the environmental isolate yielded a fourth, unrelated pattern.

Conclusion.

Long-term acute care hospitals with mechanically ventilated patients could serve as an important transmission setting for E. meningoseptica. This multidrug-resistant bacterium could pose additional risk when patients are transferred between long-term acute care hospitals and acute care hospitals.

Detection of quorum sensing signal molecules and identification of an autoinducer synthase gene among biofilm forming clinical isolates of Acinetobacter spp

Background

Quorum sensing is a term that describes an environmental sensing system that allows bacteria to monitor their own population density which contributes significantly to the size and development of the biofilm. Many gram negative bacteria use N-acyl-homoserine lactones as quorum sensing signal molecules. In this study, we sought to find out if the biofilm formation among clinical isolates of Acinetobacter spp. is under the control of autoinducing quorum sensing molecules.

Methodology/Principal Findings

Biofilm formation among clinical isolates of Acinetobacter spp. was assessed and the production of signal molecules were detected with Chromobacterium violaceum CV026 biosensor system. Characterisation of autoinducers was carried out by mass spectrometric analysis. We have also reported the identification of an autoinducer synthase gene, abaΙ among the isolates that produce quorum sensing signal molecules and have reported that the mutation in the abaI gene influences their biofilm forming capabilities. Using a microtitre-plate assay it was shown that 60% of the 50 Acinetobacter spp. isolates significantly formed biofilms. Further detection with the biosensor strain showed that some of these isolates produced long chain signal molecules. Mass spectrometric analysis revealed that five of these isolates produced N-decanoyl homoserine lactone and two isolates produced acyl-homoserine lactone with a chain length equal to C₁₂. The abaΙ gene was identified and a tetracycline mutant of the abaΙ gene was created and the inhibition in biofilm formation in the mutant was shown.

Conclusions/Significance

These data are of great significance as the signal molecules aid in biofilm formation which in turn confer various properties of pathogenicity to the clinical isolates including drug resistance. The use of quorum sensing signal blockers to attenuate bacterial pathogenicity is therefore highly attractive, particularly with respect to the emergence of multi antibiotic resistant bacteria.

Use of adherence monitors as part of a team approach to control clonal spread of multidrug-resistant Acinetobacter baumannii in a research hospital

BACKGROUND

Multidrug-resistant Acinetobacter baumannii (MDRAB) is difficult to treat and eradicate. Several reports describe isolation and environmental cleaning strategies that controlled hospital MDRAB outbreaks. Such interventions were insufficient to interrupt MDRAB transmission in 2 intensive care unit-based outbreaks in our hospital. We describe strategies that were associated with termination of MDRAB outbreaks at the National Institutes of Health Clinical Center.

METHODS

In response to MDRAB outbreaks in 2007 and 2009, we implemented multiple interventions, including stakeholder meetings, enhanced isolation precautions, active microbial surveillance, cohorting, and extensive environmental cleaning. We conducted a case-control study to analyze risk factors for acquiring MDRAB. In each outbreak, infection control adherence monitors were placed in MDRAB cohort areas to observe and correct staff infection control behavior.

RESULTS

Between May 2007 and December 2009, 63 patients acquired nosocomial MDRAB; 57 (90%) acquired 1 or more of 4 outbreak strains. Of 347 environmental cultures, only 2 grew outbreak strains of MDRAB from areas other than MDRAB patient rooms. Adherence monitors recorded 1,330 isolation room entries in 2007, of which 8% required interventions. In 2009, around-the-clock monitors recorded 4,892 staff observations, including 127 (2.6%) instances of nonadherence with precautions, requiring 68 interventions (1.4%). Physicians were responsible for more violations than other staff (58% of hand hygiene violations and 37% of violations relating to gown and glove use). Each outbreak terminated in temporal association with initiation of adherence monitoring.

CONCLUSIONS

Although labor intensive, adherence monitoring may be useful as part of a multifaceted strategy to limit nosocomial transmission of MDRAB.

[Successful treatment of thoracic drainage using urokinase for empyema in an elderly man]

A 76-year-old man was admitted to our hospital because of progressive dyspnea, fever, and consciousness disturbance. Empyema was diagnosed by chest image findings and laboratory findings of pleural effusion and serum. The patient was first given an antimicrobial agent, and chest drainage was performed. Although his general condition improved, his systemic inflammation and chest radiograph findings did not. Then, thoracoscopy under local anesthesia was considered. However, surgery was almost impossible, because he was hemiparetic, with mild conscious disturbance following cerebral hemorrhage. We decided to insert another drain into the thoracic cavity and continued to perform irrigation with saline in addition to the systemic administration of antibiotics for 3 weeks. His general condition gradually improved. Although the volume of drained fluid from the thoracic cavity decreased, the empyema lesions did not completely disappear. We then performed irrigation with saline and urokinase for 3 days, from the 40th hospital day. Irrigation drainage using saline was more effective than previously, before urokinase administration; his symptoms and empyema lesions markedly improved without antibiotics treatment. He was discharged on the 95th hospital day. For the treatment of chronic emypema, surgery using recently developed thoracoscopic techniques should be considered first, but may not be appropriate for frail elderly with severe systemic complications. Conventional intrathoracic irrigation using saline containing urokinase may be a treatment of choice for intractable empyema in frail older patients with hemiplegia caused by cerebral infarction.

Genomic analysis of Acinetobacter baumannii A118 by comparison of optical maps: identification of structures related to its susceptibility phenotype

Acinetobacter baumannii A118, a naturally competent clinical isolate, is unusually susceptible to several antibiotics. Comparison of the optical map of strain A118 with in silico-generated restriction maps of sequenced genomes and sequence analyses showed that the AbaR region, commonly found inserted within the comM gene in other isolates, is missing in strain A118, which could in part explain the susceptible phenotype exhibited by this isolate. These comparative studies also showed differences in regions where genes coding for functions that may be involved in drug resistance or susceptibility are located. Further sequencing demonstrated that cat and bla(ADC), named bla(ADC-55), are present but that a tet(A) gene usually found in other strains is not. In addition, carO and pbp2, which may play a role in susceptibility to carbapenems, are present in strain A118. These findings support the idea that A. baumannii strains possess multiple mechanisms that contribute to antibiotic resistance, and the presence of some of them is not sufficient for a resistant phenotype. The results shown here indicate that optical mapping is a useful tool for preliminary comparative genomic analysis.

Naturally competent Acinetobacter baumannii clinical isolate as a convenient model for genetic studies

Acinetobacter baumannii A118 was isolated from a patient's blood culture. It is susceptible to several antibiotics, is naturally competent, and supports replication and stable maintenance of four plasmid replicons. A. baumannii A118 took up a fluorophore-labeled oligonucleotide analog. These characteristics make this isolate a convenient model for genetic studies.

In vitro activity and in vivo efficacy of clavulanic acid against Acinetobacter baumannii

Clavulanic acid (CLA) exhibits low MICs against some Acinetobacter baumannii strains. The present study evaluates the efficacy of CLA in a murine model of A. baumannii pneumonia. For this purpose, two clinical strains, Ab11 and Ab51, were used; CLA MICs for these strains were 2 and 4 mg/liter, respectively, and the imipenem (IPM) MIC was 0.5 mg/liter for both. A pneumonia model in C57BL/6 mice was used. The CLA dosage (13 mg/kg of body weight given intraperitoneally) was chosen to reach a maximum concentration of the drug in serum similar to that in humans and a time during which the serum CLA concentration remained above the MIC equivalent to 40% of the interval between doses. Six groups (n = 15) were inoculated with Ab11 or Ab51 and were allocated to IPM or CLA therapy or to the untreated control group. In time-kill experiments, CLA was bactericidal only against Ab11 whereas IPM was bactericidal against both strains. CLA and IPM both decreased bacterial concentrations in lungs, 1.78 and 2.47 log10 CFU/g (P < or = 0.001), respectively, in the experiments with Ab11 and 2.42 and 2.28 log10 CFU/g (P < or = 0.001), respectively, with Ab51. IPM significantly increased the sterility of blood cultures over that for the controls with both strains (P < or = 0.005); CLA had the same effect with Ab51 (P < 0.005) but not with Ab11 (P = 0.07). For the first time, we suggest that CLA may be used for the treatment of experimental severe A. baumannii infections.

Methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii on computer interface surfaces of hospital wards and association with clinical isolates

Background

Computer keyboards and mice are potential reservoirs of nosocomial pathogens, but routine disinfection for non-water-proof computer devices is a problem. With better hand hygiene compliance of health-care workers (HCWs), the impact of these potential sources of contamination on clinical infection needs to be clarified.

Methods

This study was conducted in a 1600-bed medical center of southern Taiwan with 47 wards and 282 computers. With education and monitoring program of hand hygiene for HCWs, the average compliance rate was 74% before our surveillance. We investigated the association of methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Acinetobacter baumannii, three leading hospital-acquired pathogens, from ward computer keyboards, mice and from clinical isolates in non-outbreak period by pulsed field gel electrophoresis and antibiogram.

Results

Our results revealed a 17.4% (49/282) contamination rate of these computer devices by S. aureus, Acinetobacter spp. or Pseudomonas spp. The contamination rates of MRSA and A. baumannii in the ward computers were 1.1% and 4.3%, respectively. No P. aeruginosa was isolated. All isolates from computers and clinical specimens at the same ward showed different pulsotypes. However, A. baumannii isolates on two ward computers had the same pulsotype.

Conclusion

With good hand hygiene compliance, we found relatively low contamination rates of MRSA, P. aeruginosa and A. baumannii on ward computer interface, and without further contribution to nosocomial infection. Our results suggested no necessity of routine culture surveillance in non-outbreak situation.

Outcomes ofAcinetobacter baumanniiInfection in Critically Ill Surgical Patients

BACKGROUND

Multi-drug resistant (MDR) organisms in intensive care units (ICUs) are a growing concern. The emergence of several infections with MDR Acinetobacter baumannii prompted a review of cases and evaluation of the efficacy of intervention.

OBJECTIVE

To determine the rate of clinical cure, the incidence of drug resistance, and the mortality rate associated with A. baumannii infection.

METHOD

Retrospective review of A. baumannii infections in three surgical ICUs between January, 2004 and November, 2005. Infection was identified in 291 patients, 20 of whom were excluded because of incomplete documentation. Of the remaining 271 patients, 71% were male, and the mean age was 47 +/- 18 years (range 13-90 years).

RESULTS

Patients had a mean length of stay in the ICU of 14 days (range 0-136 days) before infection. The initial positive cultures were from bronchoalveolar lavage fluid (BAL) in 72.3%, blood in 16.2%, a catheter tip in 6.3%, urine in 1.8%, wound in 2.2%, and abscess in 1.1%. In 46.9% of patients, the first culture was polymicrobial. The Acinetobacter isolates were resistant or intermediate-resistant to imipenem-cilastatin in 81.2% of cases; 19.9% were resistant to all drugs except colistin, and two were resistant to all tested drugs. Colistin was used in 75.6% of patients (intravenous 61.5%, nebulized 38.5%). The mean duration of treatment was 13 +/- 8.9 days (range 0-56 days), and clinical cure was achieved in 73.8% of patients. Recurrent infection after initial cure was found in 19.2% of patients. There was no significant difference in clinical cure rates between patients treated with colistin and those treated with other culture-directed drugs (75.1% vs. 69.7%), or between patients treated with intravenous vs. nebulized colistin (72.4% vs. 79.5%). The mortality rate was 26.2% for the entire group and was significantly higher in the subgroup of transplant patients (n = 31) (64.5% vs. 21.4%; p < 0.001).

CONCLUSION

The majority of A. baumannii isolates were MDR, and a significant proportion were sensitive only to colistin. Treatment of A. baumannii infection with colistin is effective by both intravenous and nebulized routes of administration. However, infection with A. baumannii in critically ill surgical patients is associated with a high mortality rate, particularly in transplant patients.

Control of an outbreak of pandrug-resistant Acinetobacter baumannii colonization and infection in a neonatal intensive care unit

OBJECTIVE

To investigate the potential reservoir and mode of transmission of pandrug-resistant (PDR) Acinetobacter baumannii in a 7-day-old neonate who developed PDR A. baumannii bacteremia that was presumed to be the iceberg of a potential outbreak.

DESIGN

Outbreak investigation based on a program of prospective hospital-wide surveillance for nosocomial infection.

SETTING

A 24-bed neonatal intensive care unit in a 2,200-bed major teaching hospital in Taiwan that provides care for critically ill neonates born in this hospital and those transferred from other hospitals.

INTERVENTIONS

Samples from 33 healthcare workers' hands and 40 samples from the environment were cultured. Surveillance cultures of anal swab specimens and sputum samples were performed for neonates on admission to the neonatal intensive care unit and every 2 weeks until discharge. The PDR A. baumannii isolates, defined as isolates resistant to all currently available systemic antimicrobials except polymyxin B, were analyzed by pulsed-field gel electrophoresis. Control measures consisted of implementing contact isolation, reinforcing hand hygiene adherence, cohorting of nurses, and environmental cleaning.

RESULTS

One culture of an environmental sample and no cultures of samples from healthcare workers' hands grew PDR A. baumannii. The positive culture result involved a sample obtained from a ventilation tube used by the index patient. During the following 2 months, active surveillance identified PDR A. baumannii in 8 additional neonates, and isolates from 7 had the same electrokaryotype. Of the 9 neonates colonized or infected with PDR A. baumannii, 1 died from an unrelated condition. Reinforcement of infection control measures resulted in 100% adherence to proper hand hygiene protocol. The outbreak was stopped without compromising patient care.

CONCLUSIONS

In the absence of environmental contamination, transient hand carriage by personnel who cared for neonates colonized or infected with PDR A. baumannii was suspected to be the mode of transmission. Vigilance, prompt intervention and strict adherence to hand hygiene protocol were the key factors that led to the successful control of this outbreak. Active surveillance appears to be an effective measure to identify potential transmitters and reservoirs of PDR A. baumannii.

Epidemiology of multiple Acinetobacter outbreaks in The Netherlands during the period 1999–2001

An increase in the number of outbreaks of Acinetobacter infection was notified in The Netherlands during 1999-2001. The present study compared the outbreaks at the species and strain levels, and analysed the epidemiology and control measures at the different locations. For each institute, three representative isolates from three patients were identified to the species and strain levels by genotyping methods. A questionnaire investigated the impact of the outbreak, the control measures that were taken, and the possible effects of the measures. Seven outbreaks were associated with Acinetobacter baumannii (three outbreaks with a strain designated strain A, two outbreaks with a strain designated strain B, and one outbreak each with strains designated C and D). An additional outbreak was caused by genomic species 13TU, which is related closely to A. baumannii. Strains B and D were identified as European clones III and II, respectively. Except for two hospitals with outbreaks caused by strain A, there was no known epidemiological link between the participating hospitals. In all hospitals the outbreak occurred on one or several intensive care units, and spread to other departments was noted in two hospitals. The number of patients affected ranged from six to 66 over a period of 2-22 months. In most outbreaks, patients were the likely reservoir from which spread occurred. In all hospitals, a large panel of measures was required to bring the outbreak to an end. Extensive environmental sampling yielded numerous positive samples in most but not all hospitals.

Detection and analysis of iron uptake components expressed by Acinetobacter baumannii clinical isolates

The Acinetobacter baumannii 19606 prototype strain produces a 78-kDa iron-regulated outer membrane protein immunologically related to FatA, which is required for iron acquisition by the fish pathogen Vibrio anguillarum via the anguibactin-mediated system. This A. baumannii strain also secretes histamine, a biosynthetic precursor of the siderophore anguibactin. In contrast, the A. baumannii 8399 clinical strain isolated in Oregon produces a siderophore and a putative 73-kDa iron-regulated outer membrane (OM73) receptor that are different from those produced by V. anguillarum and A. baumannii 19606. These observations suggest that different A. baumannii clinical isolates express unrelated iron uptake systems. This hypothesis is supported by differences in outer membrane protein profiles among A. baumannii isolates obtained from Oregon and Europe. The 19606 isolate and some European isolates expressed a FatA-like protein, while neither 19606 nor any of the European isolates expressed proteins related to OM73. Some European isolates failed to express FatA- and OM73-like proteins. All but one of the Oregon isolates expressed OM73-like proteins, while none of them contained a FatA-like protein. The presence of these proteins always correlated with the presence of the om73- and fatA-like genes in the cognate strains. While 19606 and a few European isolates produced histamine, none of the Oregon isolates had this capability. Interestingly, one strain each from the Oregon and European isolates did not express any of these products involved in iron acquisition, indicating that they could acquire iron through siderophore-mediated transport systems different from those expressed by the 19606 and 8399 clinical isolates.

The activity of meropenem and comparators against Acinetobacter strains isolated from European hospitals, 1997-2000

In vitro susceptibilities to meropenem and comparators of Acinetobacter strains isolated from serious infections in 37 European hospital centers participating in the Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Program (1997-2000) were tested. There were 635 Acinetobacter strains collected: 490 A. baumannii; 51 A. calcoaceticus var. lwoffii; and 94 other Acinetobacter strains. Overall, meropenem and imipenem were the most effective agents tested. Resistance to the antimicrobials was: 14%, meropenem; 16%, imipenem; 39%, piperacillin-tazobactam; 41%, tobramycin; 45%, ceftazidime; and 53%, ciprofloxacin. Thus, the carbapenems have useful activity against Acinetobacter spp. and represent a viable choice for treating infections caused by these organisms.

Genetic organization of an Acinetobacter baumannii chromosomal region harbouring genes related to siderophore biosynthesis and transport

The Acinetobacter baumannii 8399 clinical isolate secretes dihydroxybenzoic acid (DHBA) and a high-affinity catechol siderophore, which is different from other bacterial iron chelators already characterized. Complementation assays with enterobactin-deficient Escherichia coli strains led to the isolation of a cosmid clone containing A. baumannii 8399 genes required for the biosynthesis and activation of DHBA. Accordingly, the cloned fragment harbours a dhbACEB polycistronic operon encoding predicted proteins highly similar to several bacterial proteins required for DHBA biosynthesis from chorismic acid. Genes encoding deduced proteins related to the E. coli Fes and the Bacillus subtilis DhbF proteins, and a putative Yersinia pestis phosphopantetheinyl transferase, all of them involved in the assembly and utilization of catechol siderophores in other bacteria, were found next to the dhbACEB locus. This A. baumannii 8399 gene cluster also contained the om73, p45 and p114 predicted genes encoding proteins potentially involved in transport of ferric siderophore complexes. The deduced products of the p114 and p45 genes are putative membrane proteins that belong to the RND and MFS efflux pump proteins, respectively. Interestingly, P45 is highly related to the E. coli P43 (EntS) protein that participates in the secretion of enterobactin. Although P114 is similar to other bacterial efflux pump proteins involved in antibiotic resistance, its genetic arrangement within this A. baumannii 8399 locus is different from that described in other bacteria. The product of om73 is a Fur- and iron-regulated surface-exposed outer-membrane protein. These characteristics together with the presence of a predicted TonB box and its high similarity to other siderophore receptors indicate that OM73 plays such a role in A. baumannii 8399. The 184 nt om73-p114 intergenic region contains promoter elements that could drive the expression of these divergently transcribed genes, all of which are in close proximity to almost perfect Fur boxes. This arrangement explains the iron- and Fur-regulated expression of om73, and provides strong evidence for a similar regulation for the expression of p114.

Acinetobacter outbreaks, 1977-2000

This review of Acinetobacter outbreaks summarizes factors related to the presence and recognition of organism transmission and describes the implementation of control and prevention measures directed at limiting spread. Exogenous transmission of Acinetobacter should be considered when infections are endemic and when case rates increase. Increasing or new antimicrobial resistances in a collection of isolates also suggest transmission, and transmission can be definitively confirmed when isolates are found to be indistinguishable from or related to one another by a discriminatory genotyping test. An investigation for a common source should be conducted. When a common source cannot be found and eliminated, or once an endemically transmitted organism is established, containment or prevention efforts may require aggressive interventions, complex interventions, or both. Colonization at multiple sites, the relative ease of induction of antibiotic resistance in the organism following patient exposure to multiple drugs, and long-term environmental survival provide enhanced opportunities for the transmission of Acinetobacter between and among patients. New approaches and interventional trials are needed to define effective measures for the prevention and control of Acinobacter infections.

Genetic and phenotypic analysis of Acinetobacter baumannii insertion derivatives generated with a transposome system

Acinetobacter baumannii is a metabolically versatile pathogen that causes severe infections in compromised patients. However, little is known about the genes and factors involved in its basic physiology and virulence properties. Insertion mutagenesis was used to initiate the identification and characterization of some of these factors and genes in the prototype strain 19606. The utilization of the pLOFKm suicide delivery vector, which harbors a suicide mini-Tn10 derivative, proved to be unsuccessful for this purpose. The EZ::TN <R6Kgammaori/KAN-2> Tnp transposome system available from Epicentre was then used in conjunction with electroporation to generate isogenic insertional derivatives of A. baumannii 19606. Replica plating showed that 2% of the colonies that grew after electroporation on agar plates without antibiotics also grew in the presence of 40 micro g of kanamycin per ml. DNA hybridization proved that all of the kanamycin-resistant derivatives contained the EZ::TN <R6Kgammaori/KAN-2> insertion element, which was mapped to different genomic locations. Replica plating on Simmons citrate agar and microtiter plate-plastic tube assays identified growth- and biofilm-defective derivatives, respectively. The location of the insertion in several of these derivatives was determined by self-ligation of NdeI- or EcoRI-digested genomic DNA and electroporation of Escherichia coli TransforMax EC100D (pir(+)). Sequence analysis of the recovered plasmids showed that some of the A. baumannii 19606 growth-defective derivatives contain insertions within genes encoding activities required for the generation of energy and cell wall components and for the biosynthesis of amino acids and purines. A gene encoding a protein similar to the GacS sensor kinase was interrupted in four derivatives, while another had an insertion in a gene coding for a hypothetical sensor kinase. A. baumannii 19606 derivatives with defective attachment or biofilm phenotypes had insertions within genes that appear to be part of a chaperone-usher transport system described for other bacteria. DNA hybridization experiments showed that the presence of strain 19606 genes encoding regulatory and attachment or biofilm functions is widespread among other A. baumannii clinical isolates.

Outbreak of Acinetobacter baumannii bacteremia in a neonatal intensive care unit: clinical implications and genotyping analysis

BACKGROUND

Outbreaks of sepsis associated with have been rarely reported in neonatal intensive care units (NICUs). We describe such an outbreak in a NICU, and the results of molecular epidemiologic investigations are presented.

MATERIALS AND METHODS

Between August and September 2000, 6 premature infants hospitalized in a pediatric NICU developed sepsis. Three additional cases had infections during November and December. For an environmental culture survey, 94 environmental specimens and hand washings of all 43 health care workers involved in this unit were examined for the presence of this organism. Two genotyping methods, pulsed field gel electrophoresis of genomic DNA digested with I and infrequent restriction site polymerase chain reaction, were used to analyze the 9 bacteremic isolates and any isolates obtained from the environmental survey and the hand washings. Another 3 bacteremic isolates of collected in the same NICU in 1999 were incorporated as controls.

RESULTS

The 9 infants were premature and had birth weights of <1,500 g. Before onset of sepsis 9 infants had received total parenteral nutrition, and 8 infants had had central venous catheters and received intrafat emulsion. Five (5.3%) environmental specimens and 10 (23.3%) hand washing specimens were positive for the organism. Except for the strain from Case 9, the results of both genotyping methods were concordant; 11 patterns were identified by infrequent restriction site polymerase chain reaction and 10 patterns by pulsed field gel electrophoresis. One major genotype was demonstrated in the first 6 bacteremic isolates as well as 3 hand washing isolates. The genotypes of the other 3 bacteremic isolates, the 3 control strains, the 5 environmental isolates and 7 other hand washing isolates were distinct from the genotype of outbreak strains.

CONCLUSION

An outbreak of bacteremia in a NICU was clearly demonstrated by the molecular epidemiologic investigation and was possibly transmitted via the hands of health care workers.

In vitro investigation of the susceptibility of Acinetobacter baumannii strains isolated from clinical specimens to ampicillin/sulbactam alone and in combination with amikacin

The sensitivity of 52 strains of Acinetobacter baumannii was determined to 13 antimicrobial drugs. All strains tested were multiresistant. Compared with MICs of amikacin and ampicillin/sulbactam alone, there was a significant decrease in MICs for both drugs when the combination was used. The results of the in vitro study of this combination showed a synergistic or partial synergistic effect in 98% of the strains.

An outbreak due to multiresistant Acinetobacter baumannii in a burn unit: risk factors for acquisition and management

OBJECTIVES

To describe the investigation and management of an outbreak due to multiresistant Acinetobacter baumannii and to determine risk factors for acquisition of the organism.

SETTING

A 14-bed regional burn unit in a Canadian tertiary-care teaching hospital.

DESIGN

Case-control study with multivariate analysis of potential risk factors using logistic regression analysis. Surveillance cultures were obtained from the hospital environment, from noninfected patients, and from healthcare providers.

RESULTS

A total of 31 (13%) of 247 patients with acute burn injuries acquired multiresistant A. baumannii between December 1998 and March 2000; 18 (58%) of the patients were infected. The organism was recovered from the hospital environment and the hands of healthcare providers. Significant risk factors for acquisition of multiresistant A. baumannii were receipt of blood products (odds ratio [OR], 10.8; 95% confidence interval [CI95], 3.4 to 34.4; P < .001); procedures performed in the hydrotherapy room (OR, 4.1; CI95, 1.3 to 13.1; P = .02); and increased duration of mechanical ventilation (OR, 1.1 per day; CI95, 1.0 to 1.1; P= .02).

INTERVENTIONS

Improved compliance with hand hygiene, strict patient isolation, meticulous environmental cleaning, and temporary closure of the unit to new admissions.

CONCLUSIONS

Acquisition of multiresistant A. baumannii was likely multifactorial, related to environmental contamination and contact with transiently colonized healthcare providers. Control measures addressing these potential sources of multiresistant A. baumannii were successful in terminating the outbreak. Ongoing surveillance and continued attention to hand hygiene and adequate environmental cleaning are essential to prevent recurrent outbreaks due to antibiotic-resistant bacteria in burn units.

Carbapenem-resistant Acinetobacter and role of curtains in an outbreak in intensive care units

Multiple-antibiotic-resistant Acinetobacter baumanii, including meropenem resistance, was first isolated from a patient in the general intensive care unit of a tertiary-referral university teaching hospital in Birmingham in December 1998. Similar strains were subsequently isolated from 12 other patients, including those on another intensive care unit within the hospital. The outbreak followed an increase in the use of meropenem in both the units. Environmental screening revealed the presence of the multiple-resistant Acinetobacter species on fomite surfaces in the intensive care unit and bed linen. The major source appeared to be the curtains surrounding patients' beds. Typing by pulsed field gel electrophoresis demonstrated that the patients' isolates and those from the environment were indistinguishable. Rigorous infection control measures including increased frequency of cleaning of the environment with hypochlorite (1000 ppm) and twice-weekly changing of curtains were implemented, along with restriction of meropenem use in the units. Isolation of the multiple-resistant Acinetobacter spp. subsequently diminished and it was not detected over a follow-up period of 18 months. To our knowledge, this is the first reported outbreak of carbapenem-resistant Acinetobacter spp. from the UK. This outbreak also highlights environmental sources, particularly dry fabrics such as curtains, as an important reservoir for dissemination of acinetobacters.

Risk factors for Acinetobacter baumannii nosocomial bacteremia in critically ill patients: a cohort study

Nosocomial bacteremia caused by Acinetobacter baumannii (AB) is of increasing concern in critically ill patients, and the risk factors for this infection are not well established. An inception cohort study in a 40-bed medical and surgical intensive care unit (ICU) at a single institution was conducted during a 2-year period to determine the risk factors for AB nosocomial bacteremia. Risk factors related to the underlying diseases, the clinical picture at admission, and those acquired during the stay in the ICU were recorded upon admission and daily throughout the ICU stay. We defined an "invasive procedures index" as the number of invasive procedures performed every day during the ICU stay before the onset of AB bacteremia divided by the number of days in the ICU before the onset of AB bacteremia. Risk factors that were independently associated with AB bacteremia were immunosuppression, unscheduled admission to the hospital, respiratory failure at ICU admission, previous antimicrobial therapy, previous sepsis in the ICU, and the invasive procedures index.

Acinetobacter baumannii has two genes encoding glutathione-dependent formaldehyde dehydrogenase: evidence for differential regulation in response to iron

The adhC1 gene from Acinetobacter baumannii 8399, which encodes a glutathione-dependent formaldehyde dehydrogenase (GSH-FDH), was identified and cloned after mapping the insertion site of Tn3-HoHo1 in a recombinant cosmid isolated from a gene library. Sequence analysis showed that this gene encodes a protein exhibiting significant similarity to alcohol dehydrogenases in bacterial, yeast, plant and animal cells. The expression of the adhC1 gene was confirmed by the detection of GSH-FDH enzyme activity in A. baumannii and Escherichia coli cells that expressed the cloned gene. However, the construction and analysis of an A. baumannii 8399 adhC1::Tn3-HoHo1 isogenic derivative revealed the presence of adhC2, a second copy of the gene encoding GSH-FDH activity. Enzyme assays and immunoblot analysis showed that adhC2 encodes a 46.5 kDa protein that is produced in similar amounts under iron-rich and iron-limited conditions. In contrast, the expression of adhC1, which encodes a 45 kDa protein with GSH-FDH activity, is induced under iron limitation and repressed when the cells are cultured in the presence of free inorganic iron. The differential expression of adhC1 is controlled at the transcriptional level and mediated through the Fur iron-repressor protein, which has potential binding sites within the promoter region of this adhC copy. The expression of both adhC copies is significantly enhanced by the presence of sub-inhibitory concentrations of formaldehyde in the culture media. Examination of different A. baumannii isolates indicates that they can be divided into two groups based on the type of GSH-FDH they produce. One group contains only the constitutively expressed 46.5 kDa protein, whilst the other produces this GSH-FDH type in addition to the iron-regulated isoenzyme. Further analysis showed that the presence and expression of the two adhC genes does not confer resistance to exogenous formaldehyde, nor does it enable it to utilize methylated compounds as a sole carbon source when cultured under iron-rich as well as iron-deficient conditions.

Acinetobacter bacteraemia in a teaching hospital, 1989-1998

Background: The mortality rate from bacteraemia is one of the highest among infections in hospitals, especially in the intensive care unit (ICU). Recently, an increase in nosocomial bacteraemia caused by gram-negative resistant pathogens has been observed. In this work we review the clinical and laboratory findings of adult patients with Acinetobacter bacteraemia in order to identify risk factors associated with mortality. Methods: A retrospective review of the medical records of patients with Acinetobacter bacteraemia identified by blood cultures from the Diagnostic Microbiology Laboratory was conducted between January 1989 and March 1998. Results: We identified 59 cases of Acinetobacter bacteraemia. Most of the infections (71%) were nosocomial; the majority occurred in the Department of Internal Medicine (28.8%), followed by Haematology (27%) and the ICU (23%). A. lwoffii was isolated in 52.5% of cases and A. baumannii in 47.5%. The related mortality was 17%. Staying in the ICU was associated with A. baumannii bacteraemia (P<0.004). An intravascular catheter was the leading source of infection (37%). Main risk factors were mechanical ventilation (28%), parenteral nutrition (23%) and the presence of a urinary catheter (22%). In the multivariate analysis the independent prognostic factors for mortality were the presence of shock (P<0.05) and the severity of the underlying disease, according to the classification of McCabe (P<0.05). Conclusions: The incidence of Acinetobacter bacteraemia has increased in the last decade, mainly since 1995. The development of septic shock and the severity of the underlying disease appear to be associated with an increase in mortality.

Investigation of an outbreak of multi-drug resistant Acinetobacter baumannii in an intensive care burns unit

Over a three month period there was an outbreak of infection, due to a multi-drug resistant Acinetobacter baumannii in the intensive care burns unit with spread of infection to other patients, both within the unit and elsewhere in the hospital. Microbiological sampling of the environment and of the healthcare workers' (HCWs) hands were carried out. Strain relatedness of the isolates was confirmed by pulsed field gel electrophoresis. Fifteen patients were involved in the outbreak, whose infections were all hospital-acquired. The burns room environment was contaminated with the A. baumannii, as was the door handle of the door leading from the ante-chamber between both rooms. This allowed the hands of HCWs to be contaminated by A. baumannii despite appropriate handwashing procedures prior to leaving the rooms. Two staff members were colonized with A. baumannii. One HCW who was directly involved in patient care was found to be "heavily" colonized, the other, with less patient contact, was only "lightly" colonized. Review of handwashing practices revealed that chlorhexidine/alcohol hand wash solution was not used by the HCW whose hands were heavily colonized.A combination of a review of handwashing practice, education about the spread of bacteria via hands and contaminated environment, and the revision of infection control procedures in the unit contributed to a prompt termination of the outbreak.

Surveillance of antibiotic resistance in European ICUs

Antibiotic resistance among bacteria causing hospital-acquired infections poses a threat, particularly to patients in intensive care units (ICUs). In order to control the spread of resistant bacteria, local, regional and national resistance surveillance data must be used to develop efficient intervention strategies. In an attempt to identify national differences and the dynamics of antibiotic resistance in European ICUs, data have been merged from several networks of resistance surveillance performed during the 1990s. It should be stressed, however, that comparisons of results from different studies using different methods and different population samples must be made with caution. Antibiotic resistance across all species and drugs was, with some exceptions, highest in southern European countries and Russia, and lowest in Scandinavia. More effective strategies are needed to control the selection and spread of resistant organisms. Antibiotic intervention policies, efficient infection control measures and an overall awareness of the serious implications at public health level will contribute to the management of antibiotic resistance.

An outbreak of imipenem-resistant Acinetobacter baumannii in critically ill surgical patients

OBJECTIVE

To describe an outbreak of imipenem-resistant Acinetobacter baumannii (IR-Ab) and the measures for its control, and to investigate risk factors for IR-Ab acquisition.

DESIGN

An observational and a case-control study.

SETTING

A surgical intensive care unit (ICU) in a university tertiary care hospital.

METHODS

After admission to the ICU of an IR-Ab-positive patient, patients were prospectively screened for IR-Ab carriage upon admission and then once a week. Environmental cleaning and barrier safety measures were used for IR-Ab carriers. A case-control study was performed to identify factors associated with IR-Ab acquisition. Cases were patients who acquired IR-Ab. Controls were patients who were hospitalized in the ICU at the same time as cases and were exposed to IR-Ab for a similar duration as cases. The following variables were investigated as potential risk factors: baseline characteristics, scores for severity of illness and therapeutic intervention, presence and duration of invasive procedures, and antimicrobial administration.

RESULTS

Beginning in May 1996, the outbreak involved 17 patients over 9 months, of whom 12 acquired IR-Ab (cases), 4 had IR-Ab isolates on admission to the ICU, and 1 could not be classified. Genotypic analysis identified two different IR-Ab isolates, responsible for three clusters. Ten of the 12 nosocomial cases developed infection. Control measures included reinforcement of barrier safety measures, limitation of the number of admissions, and thorough environmental cleaning. No new case was identified after January 1997. Eleven of the 12 cases could be compared to 19 controls. After adjustment for severity of illness, a high individual therapeutic intervention score appeared to be a risk factor for IR-Ab acquisition.

CONCLUSION

The outbreak ended after strict application of control measures. Our results suggest that high work load contributes to IR-Ab acquisition.

An outbreak of Acinetobacter baumannii: the importance of cross-transmission

OBJECTIVE

To investigate an outbreak of nosocomial infections due to multidrug-resistant (MDR) Acinetobacter baumannii and to analyze the contribution of cross-transmission in the rise in infection rates.

DESIGN

Epidemiological investigation; molecular typing using pulsed-field gel electrophoresis (PFGE); matched case-control study to identify risk factors for infection.

SETTING

A 34-bed surgical intensive care unit at a tertiary-care hospital.

PATIENTS

Eighteen patients who developed MDRA baumannii nosocomial infection were matched to 36 patients who were admitted to the same surgical intensive care unit (SICU) room and did not develop an infection during the outbreak period.

RESULTS

Prior to the outbreak, the baseline attack rate of MDR A baumannii nosocomial infections was 3 per 100 patients per month. From February 1 through March 22, 1998, the attack rate rose to 16 per 100 patients per month, with a total of 18 infections. All isolates had indistinguishable PFGE patterns. Seventy environmental cultures were negative for MDR A baumannii. Following intense infection control education, the attack rate decreased to 4 per 100 patients per month. By conditional logistic regression, cases were exposed to a significantly higher number of patients with MDR A baumannii infections compared to controls (odds ratio, 1.1; 95% confidence interval, 1.01-1.2; P=.02), even after adjusting for length of SICU admission and exposure to antibiotics and invasive devices.

CONCLUSION

Cross-transmission between patients contributed to the rise in rates of MDRA baumannii infections. A common environmental source was not detected.

Nosocomial bloodstream infections caused by Acinetobacter species in United States hospitals: clinical features, molecular epidemiology, and antimicrobial susceptibility

We examined the clinical and epidemiological features of nosocomial bloodstream infections (BSIs) caused by Acinetobacter species and observed from 1 March 1995 through 28 February 1998 at 49 United States hospitals (SCOPE National Surveillance Program). Acinetobacter species were found in 24 hospitals (49%) and accounted for 1.5% of all nosocomial BSIs reported. One hundred twenty-nine isolates were identified either as A. baumannii (n=111) or other Acinetobacter species (n=18). Patients with A. baumannii BSI, compared with patients with nosocomial BSI caused by other gram-negative pathogens, were more frequently observed in the intensive care unit (69% vs. 47%, respectively; P<.001; odds ratio [OR] 2.4; 95% confidence interval [CI] 1.6-3.7) and were more frequently receiving mechanical ventilation (58% vs. 30%, respectively; P<.001; OR 3.2; 95% CI 2.1-4.8). Crude mortality in patients with A. baumannii BSI was 32%. Molecular relatedness of strains was studied by use of polymerase chain reaction-based fingerprinting. Clonal spread of a single strain occurred in 5 hospitals. Interhospital spread of epidemic A. baumannii strains was not observed. The most active antimicrobial agents against A. baumannii (90% minimum inhibitory concentration values) were imipenem (1 mg/L; 100% of isolates susceptible), amikacin (8 mg/L; 96%), tobramycin (4 mg/L; 92%), and doxycycline (4 mg/L; 91%). Thirty percent of isolates were resistant to > or =4 classes of antimicrobials and were considered to be multidrug resistant.

Acinetobacter calcoaceticus pneumonia and the formation of pneumatoceles

Pneumatoceles are cystic lesions of the lungs often seen in children with staphylococcal pneumonia and positive-pressure ventilation. Acinetobacter calcoaceticus is an aerobic, short immobile gram-negative rod, or coccobacillus, which is an omnipresent saprophyte. The variant anitratus is the most clinically significant pathogen in this family, usually presenting as a lower respiratory tract infection. Acinetobacter has been demonstrated to be one of the most common organisms found in the ICU. We present three critically ill surgery patients with Acinetobacter pneumonia, high inspiratory pressures, and the subsequent development of pneumatoceles. One of these patients died from a ruptured pneumatocele, resulting in tension pneumothorax. Treatment of pneumatoceles should center on appropriate intravenous antimicrobial therapy. This should be culture directed but is most often accomplished with Imipenem. Percutaneous, computed tomographic-guided catheter placement or direct tube thoracostomy decompression of the pneumatocele may prevent subsequent rupture and potentially lethal tension pneumothorax.

Comparison of differential plating media and two chromatography techniques for the detection of histamine production in bacteria

The bacterial enzyme histidine decarboxylase (Hdc) catalyses the conversion of histidine into histamine. This amine is essential for the biosynthesis of iron chelators (siderophores) and is an important cause of food poisoning after consumption of fish contaminated with histamine-producing bacteria. In this work we compared different methods for detecting histamine secreted by different bacterial strains. The presence of histamine in the culture supernatant of Vibrio anguillarum, which produces Hdc and secretes the histamine-containing siderophore anguibactin, was detected by thin-layer chromatography. Similar results were obtained using the culture supernatant of the Acinetobacter baumannii 19606 prototype strain that secretes the histamine-containing siderophore acinetobactin. Conversely, histamine was not detected in the culture supernatant of an isogenic V. anguillarum Hdc mutant and the A. baumannii 8399 strain that secretes a catechol siderophore different from anguibactin and acinetobactin. These results were confirmed by capillary gas chromatography/mass spectrometry. However, all these strains tested positive for histamine secretion when cultured on differential plating media containing histidine and a pH indicator, which were specifically designed for the detection of histamine-producing bacteria. The pH increase of the medium surrounding the bacterial colonies was however drastically reduced when the histidine-containing medium was supplemented with peptone, beef extract, and glucose. The histidine-containing culture supernatants of the A. baumannii and V. anguillarum strains showed an increase of about two units of pH, turned purple upon the addition of cresol red, and contained high amounts of ammonia. Escherichia coli strains, which are Hdc negative and do not use histidine as a carbon, nitrogen, and energy source, gave negative results with the differential solid medium and produced only moderate amounts of ammonia when cultured in the presence of excess histidine. This study demonstrates that, although more laborious and requiring some expensive equipment, thin-layer and gas chromatography/mass spectrometry are more accurate than differential media for detecting bacterial histamine secretion. The results obtained with these analytical methods are not affected by byproducts such as ammonia, which are generated during the degradation of histidine and produce false positive results with the differential plating media.

Epidemiology and risk factors for nosocomial pneumonia. Emphasis on prevention

VAP is a complex nosocomial infection, the disease expression and resulting patient outcome of which is dependent on host factors, the causative organism, the timing and adequacy of treatment, and the presence of intrinsic or inducible antibiotic resistance. Significant improvements have been achieved in our ability to reduce the occurrence of VAP in the hospital setting. Clinicians caring for mechanically ventilated patients should strive to develop focused programs for the prevention of VAP, other nosocomial infections, and the occurrence of antibiotic-resistant infections at their institutions. The benefits of such programs are well demonstrated. The components of a PDSA (Plan-Do-STUDY-Act) model that can be simply employed to develop a VAP prevention program are as follows: Stages Plan: 1. Identify potentially modifiable risk factors for VAP at the institutional level. 2. Develop a strategy to modify or prevent the occurrence of these risk factors. [figure: see text] Do: 1. Carry out the planned intervention strategy. 2. Identify problems in the implementation of the designed intervention. 3. Update the intervention with solutions for the identified problems. 4. Collect basic data (e.g., VAP rates, severity of illness).

STUDY

1. Analyze data. 2. Summarize the results. Act: 1. Determine the overall success or failure of the intervention. 2. Identify potential modifications to improve the intervention strategy. 3. Prepare for next PDSA cycle. Inherent in the development and application of such programs is the concept that they are continuous processes striving to improve clinical performance over time (Fig. 3). At any given institution, the most likely approach to the prevention of NP and VAP will be a multifaceted one, employing interventions aimed at reducing the occurrence of aerodigestive tract colonization with pathogenic bacteria and aspiration. To be successful, such quality improvement programs must be embraced at the institutional level. Only in this way can hospitals hope to successfully reduce their rates of VAP and sustain or improve upon those efforts over time.