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Acinetobacter anitratus infections in man.

During a period of 17 months, 142 strains of Acinetobacter anitratus were isolated from 140 patients. They were examined for biochemical characteristics, antibiotic susceptibilities to 15 chemotherapeutic drugs and clinical and epidemiologic features. Biochemical studies were necessary for positive identification of this gram negative rod. Many isolates were susceptible to kanamycin, gentamicin, polymixin B, cotrimoxazole and nalidixic acid. Most isolates were hospital acquired and had been cultured from a number of anatomic sites in the presence of a variety of clinical situations. Acinetobacter anitratus was the primary infecting organism in two cases of septicaemia (one fatal), two pneumonias, two wound infections and six urinary tract infections. Because of its potential pathogenicity this organism should not be dismissed as a harmless commensal by laboratory staff and clinicians.

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Acinetobacter calcoaceticus infection following a dog bite.

A frequent complication of dog bite wounds is bacterial infection. The choice of antibiotics is based upon the most likely organisms. Failure to achieve wound healing suggests that an uncommon organism(s) is present and should lead the clinician to culture the wound. A case of Acinetobacter calcoaceticus infection following a dog bite is described.

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Nosocomial colonization and infection with multiresistant Acinetobacter baumannii: outbreak delineation using DNA macrorestriction analysis and PCR-fingerprinting.

The prevalence of nosocomial acinetobacter colonization and infection in a university hospital was reviewed and multiresistant Acinetobacter baumannii infections in an intensive care unit (ICU) were investigated using epidemiological typing and a case-control study. Acinetobacter colonization at various body sites was found in 3.2 to 10.8 per 1000 patients. Acinetobacter infection accounted for 0.3% of endemic nosocomial infections in critically ill patients and for 1% of nosocomial bacteraemia hospitalwide. Over a three-week period, four ventilated patients developed colonization, followed by pneumonia in two patients, with A. baumannii resistant to multiple antimicrobials. Cultures of samples from respiratory equipment and ICU surfaces (n = 27) as well as from hands of personnel (n = 14) failed to yield A. baumannii, except for one sample of respiratory tubing. Antibiogram, biotype, chromosomal DNA macrorestriction profiles and polymerase chain reaction (PCR) mediated fingerprints of A. baumannii isolates (n = 31) indicated that this outbreak was caused by two strains, one of which later spread to another hospital where it caused a second outbreak. Both strains were clearly discriminated from control strains from cases of sporadic infection. Risk factors for cross-colonization that were identified by a case-control comparison were neurosurgery, mechanical ventilation and treatment with broad-spectrum antibiotics. Transmission was controlled by implementing contact isolation precautions and routine sterilization of ventilator tubing. Wider use of sensitive genotypic methods like DNA macrorestriction analysis and PCR-mediated fingerprinting for typing nosocomial pathogens should improve the detection of micro-epidemics amenable to early control.

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An outbreak of infections with Acinetobacter calcoaceticus in burn patients: contamination of patients' mattresses.

During a 21-month period Acinetobacter calcoaceticus was the most common organism causing infections in a university burn center. Forty-three of 103 patients admitted became infected with this organism. Risk factors associated with burn wound colonization with Acinetobacter included larger burns and Foley catheter use; however, only a longer duration of hospitalization was an independent discriminator of colonization. Infection-control measures, including strict isolation and closure and repainting of the burn unit, did not prevent the transmission of Acinetobacter. An investigation found that wet mattresses served as environmental reservoirs of Acinetobacter. This finding led to a policy of discarding each patient's mattress on the day of the patient's discharge from the burn unit. Life table analysis demonstrated that this intervention led to a reduced risk of burn wound colonization with Acinetobacter (P less than .05) and ultimately resulted in the complete elimination of the organism from the burn unit.

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Genotypic investigation of multidrug-resistant Acinetobacter baumannii infections in a medical intensive care unit.

Multi-resistant Acinetobacter baumannii isolates obtained from 13 hospitalized patients over a six-month period were evaluated. One patient had an isolate susceptible only to imipenem; the next three had isolates susceptible to imipenem and ampicillin/sulbactam; the next six patients had isolates which were susceptible to imipenem, amikacin, and ampicillin/sulbactam; while the final three patients had isolates which were susceptible to imipenem and ampicillin/sulbactam. Ten patients died, five within 10 days of a positive culture. Five of six patients with bacteraemia succumbed to the infection. DNA extracted from all isolates was amplified by polymerase chain reaction using four random primers (RAPD). The resulting band patterns were compared and strains identified. In addition, all isolates were biotyped. RAPD analysis and biotyping showed that there were two distinct strains involved. The first four patients were infected with one strain (genotype ¿A', biotype 9), the subsequent nine patients were infected with a second strain (genotype ¿B', biotype 1). These results suggested that there was patient-to-patient spread of strains. Institution of, and strict adherence to, isolation procedure and other infection control practices controlled the spread of infection. These data emphasize the need for active surveillance for multidrug-resistant organisms in critically ill patients, and the value of molecular typing of strains in a hospital setting to investigate spread of infection.

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Peritoneal nitric oxide is a marker of peritonitis in patients on continuous ambulatory peritoneal dialysis.

Nitric oxide plays an important role in mediating the inflammatory process. The aim of this study was to evaluate if nitric oxide production was increased during peritonitis in patients receiving continuous ambulatory peritoneal dialysis (CAPD), and the association with the prognosis. The study population comprised 21 patients with 22 episodes of peritonitis. Fifteen patients without peritonitis were controls. Nitrate was measured by HPLC and nitrite by the Griess method, to reflect nitric oxide production. Peritoneal dialysate effluent and plasma were collected from six patients during peritonitis and 1 week after treatment to study changes in dialysate:plasma ratio. In 15 patients, nitrite was measured during peritonitis and every 3 days for 2 weeks or until normalized for evolutional changes. The dialysate:plasma ratios of nitrate and nitrite during peritonitis were reduced 26% and 41.5%, respectively, after 1 week of treatment, indicating the peritoneal production of nitric oxide during peritonitis. In the evolutional study, a 5.1-fold increase of peak nitrite levels in bacterial peritonitis (n = 13) and a 2.5-fold increase in fungal peritonitis (n = 3) were observed compared to controls. Nitrite gradually declined to control levels (9.3 +/- 7.2 days) after effective antibiotic treatment, but took longer than to normalize leukocyte count in the peritoneal dialysate effluent (3.9 +/- 1.9 days). In four patients with refractory peritonitis (Candida infection in three, Acinetobacter infection in one), the nitrite levels remained elevated 2-fold despite treatment, and the catheters were removed. It is concluded that nitrite levels in peritoneal dialysate effluent may serve as a marker to assess treatment efficacy in CAPD patients with peritonitis.

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Risk factors for an outbreak of multi-drug-resistant Acinetobacter nosocomial pneumonia among intubated patients.

INTRODUCTION: Acinetobacter baumanii is a Gram-negative coccobacillus that is normally a commensal pathogen but can be a nosocomial pathogen. An epidemiologic study was performed to investigate an outbreak of A baumanii that occurred in our medical intensive care unit (MICU) from March to September 1995. METHODS: A case-control study was performed by retrospective chart review, comparing case patients to randomly selected patients who were mechanically ventilated in the MICU for at least 1 week during the outbreak. A case patient was defined as any patient with an Acinetobacter infection in which the epidemic strain was considered to be a pathogen. The epidemic strain was defined by its antibiogram. Case patients and control patients were compared for age, gender, underlying disease, acute physiology and chronic health evaluation III score, length of MICU stay, prior antibiotic use, presence of fever, sepsis, type of pulmonary infiltrate, and outcome. Environmental and hand-washing studies also were performed during the period of the outbreak. Molecular typing was performed on available bloodstream isolates. RESULTS: There were 15 cases of A baumanii nosocomial pneumonia. Fifty percent were bacteremic; one chart was unavailable for review. Twenty-nine patients were identified as control patients. The mean age for case patients was 50 (range, 21 to 84). The mean duration of time from admission to the ICU to infection was 12.8 days (range, 4 to 40). Sepsis developed in 35% of the case patients. Forty-three percent of the case patients died during their hospitalization, with two of those deaths attributed to Acinetobacter infection. Univariate analysis showed that prior use of ceftazidime was associated with infection with Acinetobacter (11/14 case patients compared to 11/29 control patients; p < 0.01). Pulsed-field gel electrophoresis revealed two strains to be responsible for the outbreak. Hand washing was performed before patient contact by only 10% of health-care workers, and only 32% washed their hands after patient contact. CONCLUSION: The use of ceftazidime was associated with an increased risk of nosocomial pneumonia with resistant strains of Acinetobacter. Health-care workers need to improve compliance with hand-washing recommendations.

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Infections with Acinetobacter calcoaceticus (Herellea vaginicola): clinical and laboratory studies.

In a retrospective review of 53 patients, 58 episodes of infection due to Acinetobacter calcoaceticus var. anitratus (Herellea vaginicola) were studied. Although the organism is widely distributed in nature, it is of relatively low virulence since colonization is more frequently noted than infection and since most infections occur in patients subjected to the epidemiologic pressures common to nosocomial, gram-negative bacillary infection: prior antibiotic therapy; instrumentation and manipulation (e.g., endotracheal intubation, urinary bladder catheterization, arterial and venous cannulation); surgery; hospitalization, especially with residence in an intensive care unit; severe underlying disease, either systemic (e.g., chronic obstructive pulmonary disease, malignancy) or localized to the infected area (e.g., prior bacterial or aspirational pneumonia, trauma). Pneumonia was the most common infection due to A. calcoaceticus, and occurred only in patients with a tracheostomy or endotracheal tube in place. In over half the 25 patients, more than one lobe was involved and bronchopneumonia was the usual roentgenographic appearance. Cavitation (2 patients) and empyema formation (3 patients) were uncommon. The severity of acinetobacter pneumonia is reflected in the high mortality rate (44% overall, with a 36% mortality rate due primarily to infection). Tracheobronchitis due to A. calcoaceticus was less severe than pneumonia since no patients died primarily as a result of the infection. Urinary tract infections occurred in five patients, none of whom were ill and none of whom died. Urinary bladder catheterization was thought to be responsible for infection in three patients, and in at least four of the five patients infection was restricted to the lower tract. Wound infections were noted in six patients who had undergone surgery and were related to the presence of foreign bodies in the operative site in five of the patients. Surgical debridement and/or drainage of the infected area was the primary therapeutic measure employed in most cases. Only one patient died and this was a result of noninfectious causes. Skin infection due to A. calcoaceticus was seen in two patients, one of whom exhibited fulminant, fatal cellulitis and septicemia in the setting of pancytopenia. All nine patients with acinetobacter septicemia had received antecedent antibiotic therapy, and in all cases intravenous catheters were in place at the time bacteremia occurred. Clinically, seven of the nine patients were in shock. The mortality rate was 44% overall, with a 22% mortality rate due to infection. Although septicemia was thought to be "line-related" in five of the nine patients, serious post-bacteremic complications developed in three patients: prosthetic valve endocarditis, suppurative thrombophlebitis and subhepatic abscess.

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Immune response to Acinetobacter calcoaceticus infection in man.

After growth in an iron-depleted chemically-defined medium Acinetobacter calcoaceticus expressed four high mol. wt outer-membrane proteins (OMPs) which were repressed under iron supplementation or in a complex laboratory medium. Immunoblotting with serum from a septicaemic patient infected with A. calcoaceticus revealed antibody binding to these iron-repressible OMPs, indicating that they were expressed in vivo, and also to the 42- and 18-Kda OMPs. Although the antibody response to the OMPs did not vary significantly during convalescence, the response to the O-polysaccharide component of lipopolysaccharide decreased significantly. However, antibodies in serum from patients with A. calcoaceticus wound infections reacted with the iron repressible OMPs and a 54-Kda antigen suggesting a difference in immune recognition between local and systemic infection.

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[Incidence of colonization and infection by Acinetobacter baumannii in an endemic seting (ICU). Analysis of risk factors by means of a surveillance study].

BACKGROUND: Our ICU has witnessed a gradual increase in infections due to Acinetobacter baumannii complex that has reached a level of stable endemia since 1995. This situation, aggravated by a high degree of resistance, has led to the present prospective study, designed to establish the incidence of Acinetobacter colonization and to investigate the role of risk factors and their relation to environmental colonization. METHODS: Serial sampling of all patients from the time of ICU admission to discharge. Sample collection from the environment and from hospital personnel. Monitorization of pre-established risk factors and detection of episodes of infection. RESULTS: One-third of patients were colonized during their stay, with the trachea (43%), rectum (31%), and skin (35%) being the most frequent sites. In 92% of cases, colonization was established within the first 9 days after admission. Significant risk factors included mechanical ventilation (p < 0.01) and previous use of antibiotics (p < 0.007). Acinetobacter was recovered from thermometers (35%), respirator switches (43%), and damp surfaces (54%). Infection developed in 8% of patients; all had been previously colonized. CONCLUSIONS: In an endemic setting, Acinetobacter colonization can occur in a third of ICU patients. This event is relatively early and often precedes infection. Duration of mechanical ventilation and previous use of antibiotics are the main risk factors. Environmental elements are frequent bacterial reservoirs, but the main reservoir is the colonized patient.

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Investigation of an outbreak of infection with Acinetobacter calcoaceticus in a special care baby unit.

During a period of 6 months, an 'epidemic strain' of Acinetobacter calcoaceticus was isolated from 10 pre-term neonates in a special care baby unit (scbu). Of these, nine had pulmonary infections. The tenth was found to have conjunctival colonization only. The 'epidemic strain' was characterized by serotyping, biotyping, bacteriocin typing and antibiograms. An identical strain was isolated from an 'Ambu' resuscitation device but not from other environmental samples or from staff on the unit. The outbreak ceased after the colonized resuscitator was removed and an appropriate disinfection policy implemented for the replacement resuscitators.

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Safety and efficacy of colistin in Acinetobacter and Pseudomonas infections: a prospective cohort study.

OBJECTIVE: To assess renal dysfunction and outcome in patients treated exclusively with colistin vs. other antibiotics. DESIGN AND SETTING: Prospective cohort study in a mixed ICU in a university-affiliated hospital. PATIENTS: 185 patients infected with Acinetobacter baumannii and Pseudomonas aeruginosa after an ICU stay longer than 48 h: 55 in the colistin group and 130 in the noncolistin group, similar in age, APACHE II, medical status, and SOFA score. MEASUREMENTS AND RESULTS: We recorded data on epidemiology and severity of illness, site of infection, renal function before and after treatment, clinical cure, and mortality. Clinical cure was defined as simultaneous normalization of central temperature (< or = 38 degrees), leukocyte count (< or = 10,000/mm3), and PaO2/FIO2 ratio (>187). Before treatment creatinine was 0.9+/-0.2 in the colistin group and 0.9+/-0.1 in the noncolistin group; after treatment the value was 1.0+/-0.3 in both groups. The most frequent infection was ventilator-associated pneumonia: 53% vs. 66% in colistin and noncolistin groups, respectively, Acinetobacter was the cause in 65% and 60% and Pseudomonas in 35% and 53%. In the noncolistin group 81% of patients were treated with carbapenems. Inadequate empirical antimicrobial treatment was more frequent in the colistin group (100% vs. 8%), but there were no differences in the frequency of clinical cure on day 6 of treatment (15% and 17%) or in mortality (29% and 24%). CONCLUSIONS: Colistin appears to be as safe and as effective as other antimicrobials for treatment of sepsis caused by Acinetobacter and Pseudomonas in critically ill patients.

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