Acinetobacter outbreaks, 1977-2000

Multidrug-resistant Acinetobacter infection mortality rate and length of hospitalization

Acinetobacter infections have increased and gained attention because of the organism’s prolonged environmental survival and propensity to develop antimicrobial drug resistance. The effect of multidrug-resistant (MDR) Acinetobacter infection on clinical outcomes has not been reported. A retrospective, matched cohort investigation was performed at 2 Baltimore hospitals to examine outcomes of patients with MDR Acinetobacter infection compared with patients with susceptible Acinetobacter infections and patients without Acinetobacter infections. Multivariable analysis controlling for severity of illness and underlying disease identified an independent association between patients with MDR Acinetobacter infection (n = 96) and increased hospital and intensive care unit length of stay compared with 91 patients with susceptible Acinetobacter infection (odds ratio [OR] 2.5, 95% confidence interval [CI] 1.2–5.2 and OR 2.1, 95% CI 1.0–4.3] respectively) and 89 uninfected patients (OR 2.5, 95% CI 1.2–5.4 and OR 4.2, 95% CI 1.5–11.6] respectively). Increased hospitalization associated with MDR Acinetobacter infection emphasizes the need for infection control strategies to prevent cross-transmission in healthcare settings.

Wasser als Infektionsquelle in medizinischen Einrichtungen, Prävention und Kontrolle

New epidemiological and microbiological investigations using molecular typing methods to link patient and environmental strains demonstrate a strong association between water-borne pathogens and nosocomial infections. Avoiding patient exposure to these pathogens results in a decreased incidence of water-borne nosocomial infections. There remains a tremendous potential to reduce hospital acquired infections previously viewed as inevitable and unavoidable through intervention and preventive measures. The characteristics of water application in health care facilities, the vulnerability of patients, the spectrum of relevant pathogens and their ecologic aspects, legal issues and important measures for prevention and control are discussed.

Surveillance cultures and duration of carriage of multidrug-resistant Acinetobacter baumannii

Isolating carriers of multidrug-resistant (MDR) Acinetobacter baumannii is the main measure to prevent its spread. Identification of carriers accompanied by contact precautions is essential. We aimed to determine the appropriate surveillance sampling sites and the duration of carriage of MDR A. baumannii. We studied prospectively two groups of patients from whom MDR A. baumannii was previously isolated: (i) those with recent clinical isolation (<or=10 days) and (ii) those with remote clinical isolation (>or=6 months). Screening for carriage was conducted from six sites: nostrils, pharynx, skin, rectum, wounds, and endotracheal aspirates. Strains recovered concurrently from different sites were genotyped using pulsed-field gel electrophoresis. Twelve of 22 with recent clinical isolation of MDR A. baumannii had >or=1 positive screening culture, resulting in a sensitivity of 55% when six body sites were sampled. Sensitivities of single sites ranged from 13.5% to 29%. Among 30 patients with remote clinical isolation, screening cultures were positive in 5 (17%), with a mean duration of 17.5 months from the last clinical culture. Remote carriers had positive screening cultures from the skin and pharynx but not from nose, rectum, wounds, or endotracheal aspirates. Eleven strains from five patients were genotyped. In all but one case, isolates from different sites in a given patient were clonal. Current methodology is suboptimal to detect MDR A. baumannii carriage. The sensitivity of surveillance cultures is low, even when six different body sites are sampled. The proportion of individuals with previous MDR A. baumannii isolation who remain carriers for prolonged periods is substantial. These data should be considered when designing measures to limit the spread of MDR A. baumannii.

[Prevalence of Acinetobacter baumannii carriage in patients of 53 French intensive care units on a given day]

OBJECTIVE

This study was made to evaluate multiresistant Acinetobacter baumannii colonization in French intensive care units.

DESIGN

We conducted a prevalence study on the carriage of A. baumannii for a one-day period in various French ICUs. On December 10, 2003, one nasal and/or rectal swab sampling was performed in 506 patients of 53 ICUs.

RESULTS

Sixteen patients (3.16%) from 7 centers (13%) were colonized by A. baumannii. None of the known risk factors for colonization by multiresistant A. baumannii were identified in these patients.

CONCLUSIONS

Overall, A. baumannii colonization is limited except during epidemic situations. Our study reflects the carriage of A. baumannii in ICUs on a given day. This study showed that there was no multiresistant A. baumannii epidemic clone, potentially responsible for outbreaks, present in the tested French ICUs.

Multicity outbreak of carbapenem-resistant Acinetobacter baumannii isolates producing the carbapenemase OXA-40

During 2005 we detected a multicity outbreak of infections or colonization due to high-level imipenem-resistant Acinetobacter baumannii (MIC, 64 microg/ml). One hundred isolates from diverse sources were obtained from seven acute-care hospitals and two extended-care facilities; 97% of the isolates belonged to one clone. Susceptibility testing of the first 42 isolates (January to April 2005) revealed broad resistance profiles. Half of the isolates were susceptible to ceftazidime, with many isolates susceptible only to colistin. The level of AmpC beta-lactamase expression was stronger in isolates resistant to ceftazidime. PCR and subsequent nucleotide sequencing analysis identified bla(OXA-40). The presence of an OXA-40 beta-lactamase in these isolates correlated with the carbapenem resistance. By Southern blot analysis, a bla(OXA-40)-specific probe revealed that the gene was both plasmid and chromosomally located. This is the first time in the United States that such carbapenem resistance in A. baumannii has been attributable to a carbapenemase.

Susceptibility of acinetobacter strains isolated from deployed U.S. military personnel

The susceptibilities of 142 Acinetobacter baumannii-calcoaceticus complex isolates (95 from wounded U.S. soldiers deployed overseas) to 13 antimicrobial agents were determined by broth microdilution. The most active antimicrobial agents (> or =95% of isolates susceptible) were colistin, polymyxin B, and minocycline.

The Epidemiological Profile of Infections with Multidrug-Resistant Pseudomonas aeruginosa and Acinetobacter Species

Isolates of Pseudomonas aeruginosa or Acinetobacter species that are resistant to all, or almost all, commercially available antibiotics are now prevalent worldwide. Typically, these strains are recovered from patients in intensive care units who have ventilator-associated pneumonia. "Panresistant" strains can be defined as strains that are resistant to all beta -lactam and quinolone antibiotics recommended as empirical therapy for ventilator-associated pneumonia. These strains are well adapted to the hospital environment--molecular epidemiological studies have frequently revealed that only 1 or 2 clones caused outbreaks in intensive care units. However, panresistant strains may also be selected by antibiotic use. Given the lack of antibiotic options to treat infection with panresistant strains, enhanced surveillance for these organisms is necessary at unit-specific, institutional, and national levels.

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.

Interinstitutional and intrainstitutional transmission of a strain of Acinetobacter baumannii detected by molecular analysis: comparison of pulsed-field gel electrophoresis and repetitive sequence-based polymerase chain reaction

Pulsed-field gel electrophoresis and repetitive sequence-based polymerase chain reaction provided comparable strain discrimination with minor discordance in typing Acinetobacter baumannii clinical isolates from patients at our hospital and affiliated institutions. Typing revealed a cluster strain with intrainstitutional and interinstitutional spread during the study period. A long-term acute care facility may have been the reservoir.

Control of an outbreak of multidrug-resistant Acinetobacter baumannii-calcoaceticus colonization and infection in an intensive care unit (ICU) without closing the ICU or placing patients in isolation

OBJECTIVE

To describe the control of multidrug-resistant Acinetobacter baumannii-calcoaceticus (MDRABC) colonization and infection in an intensive care unit (ICU).

SETTING

An 18-bed ICU in a large tertiary care teaching hospital in London.

INTERVENTIONS

After recognition of the outbreak, a range of infection control measures were introduced over several months that were primarily aimed at reducing environmental contamination with the outbreak strain. Strategies included use of a closed tracheal suction system for all patients receiving mechanical ventilation, use of nebulized colistin for patients with evidence of mild to moderate ventilator-associated pneumonia, improved availability of alcohol for hand decontamination, and clearer designation of responsibilities and strategies for cleaning equipment and the environment in the proximity of patients colonized or infected with MDRABC.

RESULTS

The outbreak lasted from June 2001 through November 2002 and involved 136 new cases of MDRABC infection or colonization. The number of newly diagnosed cases per month reached a maximum of 15 in February 2002, and the number of new cases slowly decreased over the next 9 months.

CONCLUSION

This outbreak was controlled by emphasizing the control of environmental reservoirs and did not require recourse to ward closure or placement of affected patients in isolation.

L'isolement septique des patients colonisés–infectés par Acinetobacter baumannii est-il totalement superflu, utile ou indispensable ?

Until 2001, the infection control department of the Besançon university hospital (France) recommended isolation precautions for all patients colonized-infected by Acinetobacter baumannii (Ab) whatever the antibiotic susceptibility of the strain. These systematic isolation procedures were given up at the beginning of 2002 since the number of colonized-infected patients remained stable from 1998 to 2001.

OBJECTIVE

The aim of this study was to evaluate the impact of this decision on the risk of Ab infection.

METHOD

Incidence rates of colonization-infections that were observed during years 2002 and 2003 were compared with expected incidence rate, based on data from 1998-2001 period. Infection control practices and antibiotics consumption were evaluated for each ward of hospitalisation. Genotyping made it possible to determine diversity of clones inside each unit and the whole hospital.

RESULTS

The expected incidence per 1000 patients-days was 0.22 in comparison with observed data in 2002, 0.34 (CI(95%) [0.28-0.42]), and in 2003, 0.53 (CI(95%) [0.45-0.63]). The expected number of Ab bloodstream infections, about two per year compared with the observed numbers in 2002 and 2003 respectively seven and 17. The number of unit with more than three cases per year increased from seven in 1999 to 18 in 2003. Antibiotics consumption did not change significantly.

CONCLUSION

Genotyping results show the importance of cross-transmission in these units. Finally, observed results suggest that some measures of isolation precautions in addition to standard precautions are needed to prevent outbreaks of Ab.

Sequence and organization of pMAC, an Acinetobacter baumannii plasmid harboring genes involved in organic peroxide resistance

Acinetobacter baumannii 19606 harbors pMAC, a 9540-bp plasmid that contains 11 predicted open-reading frames (ORFs). Cloning and transformation experiments using Acinetobacter calcoaceticus BD413 mapped replication functions within a region containing four 21-bp direct repeats (ori) and ORF 1, which codes for a predicted replication protein. Subcloning and tri-parental mating experiments mapped mobilization functions to the product of ORF 11 and an adjacent predicted oriT. Three ORFs code for proteins that share similarity to hypothetical proteins encoded by plasmid genes found in other bacteria, while the predicted products of three others do not match any known sequence. The product of ORF 8 is similar to Ohr, a hydroperoxide reductase responsible for organic peroxide detoxification and resistance in bacteria. This ORF is immediately upstream of a coding region whose product is related to the MarR family of transcriptional regulators. Disk diffusion assays showed that A. baumannii 19606 is resistant to the organic peroxide-generating compounds cumene hydroperoxide (CHP) and tert-butyl hydroperoxide (t-BHP), although to levels lower than those detected in Pseudomonas aeruginosa PAO1. Cloning and introduction of the ohr and marR ORFs into Escherichia coli was associated with an increase in resistance to CHP and t-BHP. This appears to be the first case in which the genetic determinants involved in organic peroxide resistance are located in an extrachromosomal element, a situation that can facilitate the horizontal transfer of genetic elements coding for a function that protects bacterial cells from oxidative damage.

Multidrug efflux inhibition in Acinetobacter baumannii: comparison between 1-(1-naphthylmethyl)-piperazine and phenyl-arginine-beta-naphthylamide

OBJECTIVES

1-(1-Naphthylmethyl)-piperazine (NMP) has been shown to reverse multidrug resistance (MDR) in Escherichia coli overexpressing RND-type efflux pumps but there are no data on its activity in non-fermenters like Acinetobacter.

METHODS

Antimicrobial susceptibility in the absence and presence of NMP and, for comparison, phenyl-arginine-beta-naphthylamide (PAbetaN), another putative efflux pump inhibitor (EPI), was tested in laboratory and mutant strains with differing intracellular dye accumulation and expression of adeB, and in clinical isolates of Acinetobacter baumannii.

RESULTS

Based on a 4-fold or greater MIC reduction, the effects of both EPIs at low concentrations (25 mg/L) were limited. PAbetaN had a highly selective action on the reduction in the MIC of rifampicin and clarithromycin. At a higher concentration of the putative EPIs (100 mg/L), NMP was more active than PAbetaN. This effect was not limited to strains with adeB overexpression, but affected the susceptibility to linezolid, chloramphenicol and tetracycline most, and was enhanced in clinical isolates with reduced fluoroquinolone susceptibility.

CONCLUSION

NMP can partially reverse MDR in A. baumannii and differs substantially in its activity from that of PAbetaN.

The epidemiology and control of Acinetobacter baumannii in health care facilities

Acinetobacter baumannii is a ubiquitous pathogen capable of causing both community and health care-associated infections (HAIs), although HAIs are the most common form. This organism has emerged recently as a major cause of HAI because of the extent of its antimicrobial resistance and its propensity to cause large, often multifacility, nosocomial outbreaks. The occurrence of outbreak is facilitated by both tolerance to desiccation and multidrug resistance, contributing to the maintenance of these organisms in the hospital environment. In addition, the epidemiology of A. baumannii infection is often complex, with the coexistence of epidemic and endemic infections, the latter of which often is favored by the selection pressure of antimicrobials. The only good news is that potentially severe A. baumannii infection, such as bacteremia or pneumonia in patients in the intensive care unit who are undergoing intubation, do not seem to be associated with a higher attributable mortality rate or an increased length of hospital stay.

Multidrug-resistant Acinetobacter extremity infections in soldiers

War wound infection and osteomyelitis caused by multidrug-resistant (MDR) Acinetobacter species have been prevalent during the 2003-2005 military operations in Iraq. Twenty-three soldiers wounded in Iraq and subsequently admitted to our facility from March 2003 to May 2004 had wound cultures positive for Acinetobacter calcoaceticus-baumannii complex. Eighteen had osteomyelitis, 2 burn infection, and 3 deep wound infection. Primary therapy for these infections was directed antimicrobial agents for an average of 6 weeks. All soldiers initially improved, regardless of the specific type of therapy. Patients were followed up to 23 months after completing therapy, and none had recurrent infection with Acinetobacter species. Despite the drug resistance that infecting organisms demonstrated in this series, a regimen of carefully selected extended antimicrobial-drug therapy appears effective for osteomyelitis caused by MDR Acinetobacter spp.

Update on Pseudomonas aeruginosa and Acinetobacter baumannii infections in the healthcare setting

PURPOSE OF REVIEW

Infections with Pseudomonas aeruginosa and Acinetobacter baumannii are of great concern for hospitalized patients, especially with multidrug-resistant strains. This review focuses on recent data that may help us to understand the emergence, spread, and persistence of antibiotic resistance, and summarizes the optional treatment feasible for these resistant bacteria.

RECENT FINDINGS

Multidrug-resistant P. aeruginosa and A. baumannii are increasingly causing nosocomial infections; multidrug-resistant clones are spreading into new geographic areas, and susceptible strains are acquiring resistance genes. New extended-spectrum beta-lactamases and carbapenemases are emerging, leading to pan-resistant strains. Current studies focus on the effect of antibiotics on gene expression in P. aeruginosa biofilms and their contribution to resistance to therapy. Treatment options for multidrug-resistant P. aeruginosa and A. baumannii infections are limited in most cases to carbapenems. Sulbactam is a treatment option for pan-resistant A. baumannii, and or renewed use of an old drug, colistin, is being entertained for pan-resistant A. baumannii and P. aeruginosa. Immunotherapy is a promising new modality being explored. Prevention of emergence of resistance through combination therapy and pharmacokinetic strategies are studied.

SUMMARY

The emergence and spread of multidrug-resistant P. aeruginosa and A. baumannii and their genetic potential to carry and transfer diverse antibiotic resistance determinants pose a major threat in hospitals. The complex interplay of clonal spread, persistence, transfer of resistance elements, and cell-cell interaction contribute to the difficulty in treating infections caused by these multidrug-resistant strains. In the absence of new antibiotic agents, new modalities of treatment should be developed.

Multi-resistant gram-negative organisms in Maryland: a statewide survey of resistant Acinetobacter baumannii

Following the development of multi-resistant Acinetobacter baumannii at several area hospitals, a volunteer task force from the Greater Baltimore Chapter of the Association of Professionals in Infection Control and Epidemiology, Inc (APIC) set out to assess the situation throughout the state. A survey was disseminated to all 70 acute, general, and specialty hospitals in Maryland. The response rate was 57%, and multi-resistant Acinetobacter was the most prevalent resistant gram-negative organism reported.

Hospital outbreak caused by a carbapenem-resistant strain of Acinetobacter baumannii: patient prognosis and risk-factors for colonisation and infection

Between October 2001 and August 2002, 30 hospital patients became infected or colonised by a multiresistant (including to carbapenems) epidemic strain of Acinetobacter baumannii (AbMR) in a hospital outbreak. This study analysed the risk-factors associated with acquisition of this epidemic strain and investigated the prognosis of patients infected by AbMR, with the aim of elucidating factors which lead to mortality. A case-control study of the acquisition of AbMR in patients infected or colonised in the hospital outbreak was performed. Independent risk-factors leading to death were studied by logistic regression analysis. Multivariate analysis of the risk-factors for colonisation/infection with AbMR revealed an independent association with the presence of an arterial catheter (OR, 1.13; 95% CI, 1.03-1.25) and administration of imipenem as monotherapy (OR, 11.12; 95% CI, 2.33-53.09). Multivariate analysis of the prognostic features leading to mortality revealed a significant association with hypotension or shock (OR, 24.63; 95% CI, 1.56-387.56) at the time of bacterial isolation.

Investigation of a nosocomial outbreak of extended-spectrum beta-lactamase VEB-1-producing isolates of Acinetobacter baumannii in a hospital setting

A nosocomial outbreak of epidemiologically related VEB-1 extended-spectrum beta-lactamase-producing isolates of Acinetobacter baumannii occurred in 33 patients in an intensive care unit. A case-control study identified previous treatment with third-generation cephalosporins as the only risk factor for A. baumannii acquisition. Rationale for antibiotic use should be strengthened.

Prevention and control of health care-associated waterborne infections in health care facilities

The current article is a review of the public health risks attributable to waterborne pathogens in health care. The consequences of health care-associated infections (HAIs) are discussed. Not only are Legionella spp involved in HAIs, but also Pseudomonas aeruginosa, other gram-negative microorganisms, fungi, and amoeba-associated bacteria. This is particularly noteworthy among immunocompromised patients. New prevention strategies and control measures brought about through advanced planning, facility remodelling and reconstruction, disinfection, and filtration have resulted in a significant reduction of the incidence of waterborne HAIs. The positive consequences of a comprehensive multibarrier approach including prevention and control programs in health care facilities are discussed. Environmental cultures are now integrated within the infection control program of some European countries. In high-risk areas, the application of disposable sterile point-of-use filters for faucets and shower heads appears to be the practice of choice to efficiently control waterborne pathogens and to prevent infections.

Multidrug-resistant Acinetobacter baumannii

A case-control, epidemiologic, and molecular study of nosocomial MDR A. baumannii showed the existence of multiple clones and a complex epidemiologic pattern.

To understand the epidemiology of multidrug-resistant (MDR) Acinetobacter baumannii and define individual risk factors for MDR, we used epidemiologic methods, performed organism typing by pulsed-field gel electrophoresis (PFGE), and conducted a matched case-control retrospective study. We investigated 118 patients, on 27 wards, in whom MDR A. baumannii was isolated from clinical cultures. Each case-patient had a control without MDR A. baumannii and was matched for hospital length of stay, ward, and calendar time. The epidemiologic investigation found small clusters of up to 6 patients each with no common identified source. Ten different PFGE clones were found, of which 2 dominated. The PFGE pattern differed within temporospatial clusters, and antimicrobial drug susceptibility patterns varied within and between clones. Multivariate analysis identified the following significant risk factors: male sex, cardiovascular disease, having undergone mechanical ventilation, and having been treated with antimicrobial drugs (particularly metronidazole). Penicillins were protective. The complex epidemiology may explain why the emergence of MDR A. baumannii is difficult to control.

Etiology of Ventilator-Associated Pneumonia

This review focuses on the top ten causes of ventilator-associated pneumonia (VAP), updating an earlier study. These pathogens have specific risk factors, different patterns of clinical resolution, and a wide range of attributable mortality. The discussion herein analyzes these aspects, placing particular emphasis on risk factors, attributable mortality, resistance, and the implications for management.

Persistent Acinetobacter baumannii? Look inside your medical equipment

Two outbreaks of multidrug-resistant Acinetobacter baumannii occurred in our hospital. The outbreak strains were eventually isolated from respiratory ventilators, an apparatus used to cool or warm patients, and four continuous veno-venous hemofiltration machines. Removing dust from the machines and replacing all dust filters brought the outbreaks to an end.

Resistance trends of Acinetobacter spp. in Latin America and characterization of international dissemination of multi-drug resistant strains: five-year report of the SENTRY Antimicrobial Surveillance Program

OBJECTIVES

To analyze the antimicrobial susceptibility of Acinetobacter spp. isolates collected from Latin American medical centers as part of the SENTRY Antimicrobial Surveillance Program and also to evaluate the dissemination of multi-drug resistant Acinetobacter spp. strains in the region.

METHODS

A total of 826 isolates of Acinetobacter spp. from multiple infection sites were collected from January 1997 to December 2001 in ten medical centers and susceptibility tested to >25 selected agents by broth microdilution. Multi-drug resistant Acinetobacter spp. isolates were molecular typed.

RESULTS

Resistance rates to carbapenems varied significantly among countries. A continued annual increase occurred in the Argentinean medical centers. In contrast, carbapenem resistance was rare in Chilean centers, and decreased significantly in the Brazilian institutions. Acinetobacter spp. isolates recovered from lower respiratory tract and bloodstream infections were associated with lower antimicrobial susceptibility rates. Resistance rates to imipenem were higher among isolates collected from intensive care units (13.5%) than among isolates from other units. A major ribogroup pattern (521-1) was detected among eight Acinetobacter spp. strains isolated from three distinct Latin American countries.

CONCLUSIONS

This study found that antimicrobial resistance is still a major issue among Acinetobacter spp. isolates collected from some Latin American countries. The dissemination of a major bacterial cluster in different regions reinforces the importance of longitudinal surveillance programs, such as SENTRY, as valuable tools for monitoring antimicrobial susceptibility rates and guiding local interventions.

Acinetobacter skin abscess in a neonate

Although Acinetobacter is usually a species of low virulence, it is becoming increasingly more important as a cause of hospital outbreaks, particularly on intensive care units. Antibiotic resistance can develop rapidly. This organism has not been reported to cause skin abscesses previously. We describe a case of a neonate who developed an Acinetobacter abscess on our neonatal intensive care unit.