Concurrent Outbreak of Multidrug-Resistant and Susceptible Subclones of Acinetobacter baumannii Affecting Different Wards of a Single Hospital

Pan drug-resistant Acinetobacter baumannii causing nosocomial infections among burnt children

Background: Nosocomial infection caused by Acinetobacter baumannii has emerged as a world-wide serious problem in the emergence of multidrug-resistant (MDR). Infections caused by antibiotic-resistant strains of A. baumannii cannot be completely eliminated among the infected patients. This study aimed to monitor antibiotic resistance among A. baumannii strains isolated from burnt children.

Methods: After performing biochemical identification tests on 115 isolates, 62 were detected as A. baumannii . Minimum inhibitory concentration (MIC) was used to test susceptibility to colistin, and disk agar diffusion was used for the susceptibility of the isolates to the antibiotics Ciprofloxacin, Amikacin, Gentamicin, Cefepime, Meropenem, Imipenem, Ceftazidime, Levofloxacin and Piperacillin/Tazobactam. Bacterial species were isolated and identified as multidrug-resistant (MDR), extensively drug-resistant (XDR) and pan drug-resistant (PDR), based on the susceptibility patterns to elected antibiotics, deputing different classes of antimicrobial.

Results: The antibiotic susceptibility pattern out of a total of 62 bacterial strains used in this study. Thirty-six (58%) strains were categorized as MDR, 17 (27.5%) as XDR, and nine (14.5%) as PDR.

Conclusion: To reduce the threat of antimicrobial resistance, MDR, XDR and PDR A. baumannii strains must be evaluated by all clinical microbiology laboratories.

Study of multidrug resistance in prevalent Gram-negative bacteria in burn patients in Iran: A systematic review and meta-analysis

OBJECTIVES

Recently, multidrug-resistant (MDR) Gram-negative bacteria (GNB) have become a serious concern causing infections in hospitalised burn patients. This meta-analysis was conducted to detect the prevalence of infections caused by MDR-GNB in hospitalised burn patients in Iran.

METHODS

An electronic search was performed using PubMed, Scopus, Web of Science, EMBASE and Iranian databases. Statistical analysis was performed using STATA13. According to the results of the heterogeneity test, a fixed- or random-effects model was used. Publication bias was detected based on Egger's test. Of 1292 articles identified in the initial search, 107 studies were included in this review.

RESULTS

According to the results, the lowest resistance rate was observed in Acinetobacter baumannii and Pseudomonas aeruginosa to colistin, estimated at 21% [95% confidence interval (CI) 2-49%; I²=97.30%] and 27% (95% CI 0-82%; I²=99.27%), respectively. Moreover, the highest rate was to cefepime, estimated 98% (95% CI 93-100%; I²=88.28%) and 87% (95% CI 81-92%; I²=96.27%).

CONCLUSION

The prevalence of MDR-GNB in Iranian burn patients is very high. Thus, a comprehensive infectious control programme, a reduction in the use of antibiotic prophylaxis, and thorough information regarding antimicrobial resistance patterns is required.

One-year molecular surveillance of carbapenem-susceptible A. baumannii on a German intensive care unit: diversity or clonality

Background

A. baumannii is a common nosocomial pathogen known for its high transmission potential. A high rate of carbapenem-susceptible Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB)-complex in clinical specimens led to the implementation of a pathogen-based surveillance on a 32-bed surgical intensive care unit (SICU) in a German tertiary care centre.

Methods

Between April 2017 and March 2018, ACB-complex isolates with an epidemiological link to the SICU were further assessed. Identification to the species level was carried out using a multiplex PCR targeting the gyrB gene, followed by RAPD, PFGE (ApaI) and whole genome sequencing (WGS, core genome MLST, SeqSphere+ software, Ridom). Additional infection prevention and control (IPC) measures were introduced as follows: epidemiological investigations, hand hygiene training, additional terminal cleaning and disinfection incl. UV-light, screening for carbapenem-susceptible A. baumannii and environmental sampling. Hospital-acquired infections were classified according to the CDC definitions.

Results

Fourty four patients were colonized/infected with one or two (different) carbapenem-susceptible ACB-complex isolates. Fourty three out of 48 isolates were classified as hospital-acquired (detection on or after 3rd day of admission). Nearly all isolates were identified as A. baumannii, only four as A. pittii. Twelve patients developed A. baumannii infections. Genotyping revealed two pulsotype clusters, which were confirmed to be cgMLST clonal cluster type 1770 (n = 8 patients) and type 1769 (n = 12 patients) by WGS. All other isolates were distinct from each other. Nearly all transmission events of the two clonal clusters were confirmed by conventional epidemiology. Transmissions stopped after a period of several months. Environmental sampling revealed a relevant dissemination of A. baumannii, but only a few isolates corresponded to clinical strains. Introduction of the additional screening revealed a significantly earlier detection of carbapenem-susceptible A. baumannii during hospitalization.

Conclusions

A molecular and infection surveillance of ACB-complex based on identification to the species level, classic epidemiology and genotyping revealed simultaneously occurring independent transmission events and clusters of hospital-acquired A. baumannii. This underlines the importance of such an extensive surveillance methodology in IPC programmes also for carbapenem-susceptible A. baumannii.

Multi-drug resistant Acinetobacter species: a seven-year experience from a tertiary care center in Lebanon

Background

Acinetobacter species have become increasingly common in the intensive care units (ICU) over the past two decades, causing serious infections. At the American University of Beirut Medical Center, the incidence of multi-drug resistant Acinetobacter baumannii (MDR-Ab) infections in the ICU increased sharply in 2007 by around 120%, and these infections have continued to cause a serious problem to this day.

Methods

We conducted a seven-year prospective cohort study between 2007 and 2014 in the ICU. Early in the epidemic, a case-control study was performed that included MDR-Ab cases diagnosed between 2007 and 2008 and uninfected controls admitted to the ICU during the same time.

Results

The total number of patients with MDR-Ab infections diagnosed between 2007 and 2014 was 128. There were also 99 patients with MDR-Ab colonization without evidence of active infection between 2011 and 2014. The incidence of MDR-Ab transmission was 315.4 cases/1000 ICU patient-days. The majority of infections were considered hospital-acquired (84%) and most consisted of respiratory infections (53.1%). The mortality rate of patients with MDR-Ab ranged from 52% to 66%.

Conclusion

MDR-Ab infections mostly consisted of ventilator-associated pneumonia and were associated with a very high mortality rate. Infection control measures should be reinforced to control the transmission of these organisms in the ICU.

Allium stipitatum Extract Exhibits In Vivo Antibacterial Activity against Methicillin-Resistant Staphylococcus aureus and Accelerates Burn Wound Healing in a Full-Thickness Murine Burn Model

The in vivo antibacterial and burn wound healing potency of Persian shallot bulbs (Allium stipitatum) were explored in a mice burn model infected with methicillin-resistant Staphylococcus aureus (MRSA). Hexane (ASHE) and dichloromethane (ASDE) extracts were tested. Female BALB/c mice were inflicted with third-degree thermal injury followed by infection with MRSA. ASHE and ASDE formulated with simple ointment base (SOB) at concentrations of 1%, 2%, and 5% (w/w) were topically applied to burn wounds twice a day for 20 days. Silver sulfadiazine (1%) served as drug positive control. Microbiological analysis was carried out on 1, 2, 3, 4, and 5 days postwounding (dpw) and histopathological analysis at the end of the experiment (20 dpw). Both ointments demonstrated strong antibacterial activity with complete elimination of MRSA at 48–72 h after infection. The rate of wound contraction was higher (95–100%) in mice groups treated with ASHE and ASDE ointments after 15 dpw. Histological analysis revealed significant increase (p < 0.05) in epithelialization and collagenation in treated groups. The ASHE and ASDE were found to be relatively noncytotoxic and safe to Vero cell line (383.4 μg mL⁻¹; 390.6 μg mL⁻¹), suggesting the extracts as safe topical antibacterial as well as promising alternatives in managing thermal injuries.

Infection Control Programs and Antibiotic Control Programs to Limit Transmission of Multi-Drug Resistant Acinetobacter baumannii Infections: Evolution of Old Problems and New Challenges for Institutes

Background: Acinetobacter baumannii complex (A. baumannii) has been isolated worldwide. The rapid spread of multidrug-resistant A. baumannii complex (MDRAB) in clinical settings has made choosing an appropriate antibiotic to treat these infections and executing contact precautions difficult for clinicians. Although controlling the transmission of MDRAB is a high priority for institutions, there is little information about MDRAB control. Therefore, this study evaluated infection control measures for A. baumannii infections, clusters and outbreaks in the literature. Methods: We performed a review of OVID Medline (from 1980 to 2015), and analyzed the literature. Results: We propose that both infection control programs and antibiotic control programs are essential for control of MDRAB. The first, effective control of MDRAB infections, requires compliance with a series of infection control methods including strict environmental cleaning, effective sterilization of reusable medical equipment, concentration on proper hand hygiene practices, and use of contact precautions, together with appropriate administrative guidance. The second strategy, effective antibiotic control programs to decrease A. baumannii, is also of paramount importance. Conclusion: We believe that both infection control programs and antibiotics stewardship programs are essential for control of MDRAB infections.

A bronchofiberoscopy-associated outbreak of multidrug-resistant Acinetobacter baumannii in an intensive care unit in Beijing, China

Background

Bronchofiberscopy, a widely used procedure for the diagnosis of various pulmonary diseases within intensive care units, has a history of association with nosocomial infections. Between September and November 2009, an outbreak caused by multidrug-resistant Acinetobacter baumannii (MDR-Ab) was observed in the intensive care unit of a tertiary care hospital in Beijing, China. This study is aimed to describe the course and control of this outbreak and investigate the related risk factors.

Methods

Clinical and environmental sampling, genotyping with repetitive extragenic palindromic polymerase chain reaction (REP-PCR), and case–control risk factor analysis were performed in the current study.

Results

During the epidemic period, 12 patients were infected or colonized with MDR-Ab. Sixteen (72.7%) of twenty-two MDR-Ab isolates from the 12 patients and 22 (84.6%) of 26 MDR-Ab isolates from the bronchofiberscope and the healthcare-associated environment were clustered significantly into a major clone (outbreak MDR-Ab strain) by REP-PCR typing. Seven patients carrying the outbreak MDR-Ab strain were defined as the cases. Six of the seven cases (83%) received bronchofiberscopy versus four of the 19 controls (21%) (odds ratio, 22.5; 95% confidence interval, 2.07–244.84; P = 0.005). Several potential administrative and technical problems existed in bronchofiberscope reprocessing.

Conclusions

Bronchofiberscopy was associated with this MDR-Ab outbreak. Infection control precautions including appropriate bronchofiberscope reprocessing and environmental decontamination should be strengthened.

Blood stream infections (BSI) in severe burn patients--early and late BSI: a 9-year study

Bloodstream infections (BSI) and sepsis are among the most common complications occurring in severe burn patients. This study was designed to evaluate changes in BSI pathogens over almost a decade in severe burn patients at Rambam Healthcare Campus, and BSI occurrence during early and late hospitalization periods. Retrospective computerized data was retrieved from all severe burn patients hospitalized in our institution during the years 2001-2009. BSI in the first week was defined as early BSI, and in the second week and beyond, late BSI. Of 159 severe burns patients, 74 had at least one BSI episode. Most first BSI episodes were diagnosed during the first week of hospitalization. In late BSI, an increased prevalence of resistant bacteria (methicillin-resistant Staphylococcus aureus [MRSA], carbapenem-resistant Klebsiella pneumoniae [CRKP], imipenem-resistant Pseudomonas aeruginosa [PSE-IMP]) and Candida spp. were observed. However, over the 9-year study period, only CRKP increased significantly. In summary, except for the sudden appearance and increase in CRKP (8% increase; p=0.045), we did not observe a significant change in the BSI pathogen profile over the 9-year period. Nevertheless, over the hospitalization period, there is a clear change in the BSI bacteria profile, especially after 4 weeks of hospitalization.

Multi-drug-resistant gram-negative bacterial infection in surgical patients hospitalized in the ICU: a cohort study

We sought to identify risk factors for postoperative infections, caused by multi-drug-resistant gram-negative bacteria (MDR-GNB) in surgical patients. This was a retrospective cohort study among patients hospitalized in the intensive care unit (ICU) for more than 5 days, following general surgical operations. Comparison of patients who developed infection caused by MDR-GNB with the remainder of the cohort showed that every minute of operative time, use of special treatments during hospitalization (antineoplastic, immunosuppressive or immunomodulating therapies), every day of metronidazole, and every day of carbapenems use, increased patients' odds to acquire an infection caused by MDR-GNB by 0.7%, 8.9 times, 9%, and 9%, respectively [OR (95% CI): 1.007 (1.003-1.011), p = 0.001; 8.9 (1.8-17.3), p = 0.004; 1.09 (1.04-1.18), p = 0.039; 1.09 (1.01-1.18), p = 0.023, respectively]. The above were adjusted in the multivariable analysis for the confounder of time distribution of infections caused by MDR-GNB. Finally, the secondary comparison, with patients that did not develop any infection, showed that patients who had received antibiotics, within 3 months prior to admission, had 3.8 times higher odds to acquire an infection caused by MDR-GNB [OR (95% CI): 3.8 (1.07-13.2), p = 0.002]. This study depicts certain, potentially modifiable, risk factors for postoperative infections in patients hospitalized in the ICU for more than 5 days.

Epidemiology of nosocomial colonization/infection caused by Acinetobacter spp. in patients of six surgical clinics in war and peacetime

Background/Aim. Acinetobacter spp. has emerged as nosocomial pathogen during the past few decades in hospitals all over the world, but it has increasingly been implicated as a serious nosocomial pathogen in military hospitals. The aim of this study was to analyze and compare the surveillance data on Acinetobacter nosocomial colonization/infection (NCI) collected during the wartime with the data collected in peacetime. Methods. We conducted a prospective study of incidence of Acinetobacter spp. colonization/ infection. Also, the two nested case-control studies were conducted. The patients with nosocomial infection (cases) were compared with those with nosocomial colonization (controls) during the two different periods, wartime and peacetime. The patients with NCI by Acinetobacter spp. were identified by the case-based surveillance. The surveillance covered all the patients in 6 surgical clinics. Results. During the study periods a total of 166 patients had cultures that grew Acinetobacter spp. and the pooled rates of Acinetobacter spp. colonization and infection were significantly higher in wartime. When patients with NCI in wartime were compared with those with NCI in peacetime significant differences were observed. In the war year, the patients were more significantly males (p < 0.000). In a period of peace, most of the colonization/infections were reported from patients with certain chronic diseases (p = 0.020) and the survival of patients was more significant (p = 0.049). During the peacetime, proportions of Acinetobacter isolates resistent to ciprofloksacin, imipenem and meropenem were significantly higher (p < 0.001). Conclusion. This study provides additional important information about the risk factors of nosocomial Acinetobacter spp. infections in a large cohort of surgical patients. This is also the first study that directly examines epidemiological differences between NCI caused by Acinetobacter spp. during the war and peace period.

Current control and treatment of multidrug-resistant Acinetobacter baumannii infections

Institutional outbreaks caused by Acinetobacter baumannii strains that have acquired multiple mechanisms of antimicrobial drug resistance constitute a growing public-health problem. Because of complex epidemiology, infection control of these outbreaks is difficult to attain. Identification of potential common sources of an outbreak, through surveillance cultures and epidemiological typing studies, can aid in the implementation of specific control measures. Adherence to a series of infection control methods including strict environmental cleaning, effective sterilisation of reusable medical equipment, attention to proper hand hygiene practices, and use of contact precautions, together with appropriate administrative guidance and support, are required for the containment of an outbreak. Effective antibiotic treatment of A baumannii infections, such as ventilator-associated pneumonia and bloodstream infections, is also of paramount importance. Carbapenems have long been regarded as the agents of choice, but resistance rates have risen substantially in some areas. Sulbactam has been successfully used in the treatment of serious A baumannii infections; however, the activity of this agent against carbapenem-resistant isolates is decreasing. Polymyxins show reliable antimicrobial activity against A baumannii isolates. Available clinical reports, although consisting of small-sized studies, support their effectiveness and mitigate previous concerns for toxicity. Minocycline, and particularly its derivative, tigecycline, have shown high antimicrobial activity against A baumannii, though relevant clinical evidence is still scarce. Several issues regarding the optimum therapeutic choices for multidrug-resistant A baumannii infections need to be clarified by future research.

Genetic basis of multidrug resistance in Acinetobacter baumannii clinical isolates at a tertiary medical center in Pennsylvania

A total of 49 unique clinical isolates of multidrug-resistant (MDR) Acinetobacter baumannii identified at a tertiary medical center in Pittsburgh, Pennsylvania, between August 2006 and September 2007 were studied for the genetic basis of their MDR phenotype. Approximately half of all A. baumannii clinical isolates identified during this period qualified as MDR, defined by nonsusceptibility to three or more of the antimicrobials routinely tested in the clinical microbiology laboratory. Among the MDR isolates, 18.4% were resistant to imipenem. The frequencies of resistance to amikacin and ciprofloxacin were high at 36.7% and 95.9%, respectively. None of the isolates was resistant to colistin or tigecycline. The presence of the carbapenemase gene bla(OXA-23) and the 16S rRNA methylase gene armA predicted high-level resistance to imipenem and amikacin, respectively. bla(OXA-23) was preceded by insertion sequence ISAba1, which likely provided a potent promoter activity for the expression of the carbapenemase gene. The structure of the transposon defined by ISAba1 differed from those reported in Europe, suggesting that ISAba1-mediated acquisition of bla(OXA-23) may occur as an independent event. Typical substitutions in the quinolone resistance-determining regions of the gyrA and parC genes were observed in the ciprofloxacin-resistant isolates. Plasmid-mediated quinolone resistance genes, including the qnr genes, were not identified. Fifty-nine percent of the MDR isolates belonged to a single clonal group over the course of the study period, as demonstrated by pulsed-field gel electrophoresis.

Acinetobacter baumannii: emergence of a successful pathogen

Acinetobacter baumannii has emerged as a highly troublesome pathogen for many institutions globally. As a consequence of its immense ability to acquire or upregulate antibiotic drug resistance determinants, it has justifiably been propelled to the forefront of scientific attention. Apart from its predilection for the seriously ill within intensive care units, A. baumannii has more recently caused a range of infectious syndromes in military personnel injured in the Iraq and Afghanistan conflicts. This review details the significant advances that have been made in our understanding of this remarkable organism over the last 10 years, including current taxonomy and species identification, issues with susceptibility testing, mechanisms of antibiotic resistance, global epidemiology, clinical impact of infection, host-pathogen interactions, and infection control and therapeutic considerations.

Acinetobacter infection in the ICU

Acinetobacter is a formidable challenge to managing critically ill patients. This pathogen's ability to rapidly develop antimicrobial resistance to all currently available antimicrobial agents is concerning because increasing data support attributable mortality to these bacteria when associated with hospitalized patients with comorbidities and severe illness. The role of dual therapy is currently unclear and might be associated with increased toxicities without proven synergy or ability to prevent the development of resistance. Infection control and antibiotic control measures might have the greatest impact on these bacteria. Continued efforts are needed to develop new antimicrobial agents against this pathogen and assess the ideal currently available agents.

Early Experience with Tigecycline for Ventilator-Associated Pneumonia and Bacteremia Caused by Multidrug-ResistantAcinetobacter baumannii

STUDY OBJECTIVE

To evaluate early experience with tigecycline alone or in combination with other antimicrobials for treatment of ventilator-associated pneumonia (VAP) and/or bacteremia caused by multidrug-resistant Acinetobacter baumannii.

DESIGN

Retrospective case series.

SETTING

University-affiliated medical center.

PATIENTS

Twenty-five patients with multidrug-resistant A. baumannii who received tigecycline for VAP (19 patients), bacteremia (3), or VAP plus bacteremia (3) between September 1, 2005, and May 31, 2006. Five patients were treated with tigecycline alone.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes were resolution of clinical signs and symptoms of the infection and documented microbial eradication of A. baumannii with tigecycline. Overall, 21 (84%) of the 25 patients had clinical resolution. Four had clinical failure: three with VAP and one with VAP plus bacteremia that developed resistance to tigecycline during therapy. Microbial eradication was demonstrated in 12 (80%) of 15 patients in whom repeat cultures were obtained. Three patients with VAP had a recurrence of infection: one patient had two recurrences, and two patients had one recurrence each. All four recurrent episodes led to clinical resolution and microbial eradication. No patients discontinued tigecycline because of adverse events.

CONCLUSION

Tigecycline was effective in most of these 25 patients when used alone or in combination with other antimicrobials for VAP and/or bacteremia caused by multidrug-resistant A. baumannii. The emergence of a resistant strain while one patient was receiving therapy, however, is concerning.

Emergence of resistant Acinetobacter baumannii in critically ill patients within an acute care teaching hospital and a long-term acute care hospital

BACKGROUND

Acinetobacter baumannii is a gram-negative, coccobacillus found in water and is a significant nosocomial pathogen in hospitals. This report chronicles the appearance in June 2003 of a multidrug-resistant A baumannii (MDR-AB) strain, its dissemination, and interventions used to control it in an acute care hospital (ACH) and long-term acute care facility (LTAC).

METHODS

Molecular typing using pulsed-field gel electrophoresis (PFGE) showed that 88 of 99 strains (89%) gave an identical banding designated as clone A. Eight additional isolates were variants of clone A, and 3 isolates were unrelated.

RESULTS

A baumannii was isolated from 229 patients between January 2003 and December 2004. Of these patients, 151 (66%) were colonized/infected with MDR-AB. Most isolates were resistant to antibiotics except for imipenem and ampicillin/sulbactam. Isolates included 108 (72%) in the respiratory tract, 32 (21%) in wounds, 6 (4%) in blood, and 5 (3%) in urine. Most isolates were found in the LTAC (70 isolates), ICU step-down (27 isolates), and ICU (26 isolates).

CONCLUSION

This epidemiologic history illustrates (1) epidemic clonal spread, (2) target populations, (3) variable monthly prevalence, and (4) intervention outcomes. With intervention, the number of new isolates in the ACH decreased by dedicating an infection control professional to critical care, daily surveillance, isolation of positive MDR-AB patients, universal gloving, and routinely reporting results.

The diversity of definitions of multidrug-resistant (MDR) and pandrug-resistant (PDR) Acinetobacter baumannii and Pseudomonas aeruginosa

Different definitions of the terms multidrug-resistant (MDR) and pandrug-resistant (PDR) Acinetobacter baumannii and Pseudomonas aeruginosa have been used in the biomedical literature. The authors searched for relevant studies indexed in the PubMed database (01/2000-09/2005) to systematically examine the various definitions of MDR and PDR for these bacteria. Initially 107 retrieved relevant studies were reviewed. Ninety-two studies were further analysed, 50 of which focused on A. baumannii and 42 on P. aeruginosa. A considerable diversity of definitions of the terms MDR and PDR A. baumannii and P. aeruginosa was found. Of note, the term PDR was inappropriately used in all five studies that used it. The review reveals that various definitions have been used for the terms MDR and PDR A. baumannii and P. aeruginosa, a fact that causes confusion to researchers and clinicians. The authors believe that at least a widely accepted definition for PDR A. baumannii and P. aeruginosa should be uniformly used worldwide.

Carbapenem resistance in Acinetobacter baumannii: mechanisms and epidemiology

The increasing trend of carbapenem resistance in Acinetobacter baumannii worldwide is a concern since it limits drastically the range of therapeutic alternatives. Metallo-beta-lactamases (VIM, IMP, SIM) have been reported worldwide, especially in Asia and western Europe, and confer resistance to all beta-lactams except aztreonam. The most widespread beta-lactamases with carbapenemase activity in A. baumannii are carbapenem-hydrolysing class D beta-lactamases (CHDLs) that are mostly specific for this species. These enzymes belong to three unrelated groups of clavulanic acid-resistant beta-lactamases, represented by OXA-23, OXA-24 and OXA-58, that can be either plasmid- or chromosomally-encoded. A. baumannii also possesses an intrinsic carbapenem-hydrolysing oxacillinase, the expression of which may vary, that may play a role in carbapenem resistance. In addition to beta-lactamases, carbapenem resistance in A. baumannii may also result from porin or penicillin-binding protein modifications. Several porins, including the 33-kDa CarO protein, that constitute a pore channel for influx of carbapenems, might be involved in carbapenem resistance.

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.

Risk factors for the isolation of multi-drug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa: a systematic review of the literature

An understanding of the epidemiology of multi-drug-resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa infections is necessary in order to develop strategies to curtail their spread. For this purpose, the evidence linking the isolation of MDR A. baumannii and P. aeruginosa with specific risk factors was evaluated. PubMed was searched for the 20-year period from September 1985 to September 2005, and eligible studies were considered to be those that: (1) linked the isolation of A. baumannii and P. aeruginosa with specific risk factors; (2) described the characteristics of the affected patients in detail; and (3) provided data on the antibiotic resistance profile of the isolated micro-organisms. Fifty-five studies were found referring to A. baumannii (28 with case-control methodology and 27 outbreak investigations without case-control methodology), and 42 studies were found referring to P. aeruginosa (25 with case-control methodology and 17 outbreak investigations without case-control methodology). Although heterogeneous study designs and investigated risk factors limited this analysis, it was concluded that acquisition and spread of these micro-organisms appear to be related to a large number of variables. Among the most important were deficiencies in the implementation of infection control guidelines and the use of broad-spectrum antibiotics. Use of carbapenems and third-generation cephalosporins appear to be related to the development of an MDR phenotype by A. baumannii, while carbapenems and fluoroquinolones are implicated in MDR P. aeruginosa. The diversity of risk factors associated with the development of MDR A. baumannii and P. aeruginosa suggests that a separate outbreak investigation should be performed in each hospital setting. The development of innovative control strategies is needed in order to limit the spread of these pathogens.

Burn wound infections

Burns are one of the most common and devastating forms of trauma. Patients with serious thermal injury require immediate specialized care in order to minimize morbidity and mortality. Significant thermal injuries induce a state of immunosuppression that predisposes burn patients to infectious complications. A current summary of the classifications of burn wound infections, including their diagnosis, treatment, and prevention, is given. Early excision of the eschar has substantially decreased the incidence of invasive burn wound infection and secondary sepsis, but most deaths in severely burn-injured patients are still due to burn wound sepsis or complications due to inhalation injury. Burn patients are also at risk for developing sepsis secondary to pneumonia, catheter-related infections, and suppurative thrombophlebitis. The introduction of silver-impregnated devices (e.g., central lines and Foley urinary catheters) may reduce the incidence of nosocomial infections due to prolonged placement of these devices. Improved outcomes for severely burned patients have been attributed to medical advances in fluid resuscitation, nutritional support, pulmonary and burn wound care, and infection control practices.

Burn wound infections

Burns are one of the most common and devastating forms of trauma. Patients with serious thermal injury require immediate specialized care in order to minimize morbidity and mortality. Significant thermal injuries induce a state of immunosuppression that predisposes burn patients to infectious complications. A current summary of the classifications of burn wound infections, including their diagnosis, treatment, and prevention, is given. Early excision of the eschar has substantially decreased the incidence of invasive burn wound infection and secondary sepsis, but most deaths in severely burn-injured patients are still due to burn wound sepsis or complications due to inhalation injury. Burn patients are also at risk for developing sepsis secondary to pneumonia, catheter-related infections, and suppurative thrombophlebitis. The introduction of silver-impregnated devices (e.g., central lines and Foley urinary catheters) may reduce the incidence of nosocomial infections due to prolonged placement of these devices. Improved outcomes for severely burned patients have been attributed to medical advances in fluid resuscitation, nutritional support, pulmonary and burn wound care, and infection control practices.

Overview of nosocomial infections caused by gram-negative bacilli

We analyzed data from the National Nosocomial Infections Surveillance (NNIS) System from 1986-2003 to determine the epidemiology of gram-negative bacilli in intensive care units (ICUs) for the most frequent types of hospital-acquired infection: pneumonia, surgical site infection (SSI), urinary tract infection (UTI), and bloodstream infection (BSI). We analyzed >410,000 bacterial isolates associated with hospital-acquired infections in ICUs during 1986-2003. In 2003, gram-negative bacilli were associated with 23.8% of BSIs, 65.2% of pneumonia episodes, 33.8% of SSIs, and 71.1% of UTIs. The percentage of BSIs associated with gram-negative bacilli decreased from 33.2% in 1986 to 23.8% in 2003. The percentage of SSIs associated with gram-negative bacilli decreased from 56.5% in 1986 to 33.8% in 2003. The percentages pneumonia episodes and UTIs associated with gram-negative bacilli remained constant during the study period. The proportion of ICU pneumonia episodes associated with Acinetobacter species increased from 4% in 1986 to 7.0% in 2003 (P<.001, by the Cochran-Armitage chi2 test for trend). Significant increases in resistance rates were uniformly seen for selected antimicrobial-pathogen combinations. Gram-negative bacilli are commonly associated with hospital-acquired infections in ICUs. The proportion of Acinetobacter species associated with ICU pneumonia increased from 4% in 1986 to 7.0% in 2003.