Use of macrorestriction analysis to demonstrate interhospital spread of multiresistant Acinetobacter baumannii in São Paulo, Brazil

Characterization of the Biodiesel Degrading Acinetobacter oleivorans Strain PT8 Isolated from the Fecal Material of a Painted Turtle (Chrysemys picta)

Acinetobacter species are gram-negative, non-fermenting bacteria with coccobacilli morphology. The bacteria are found ubiquitously and have the ability to occupy niches which include environmental sites, animals, and humans. The original purpose of this study was to determine if painted turtles (Chrysemys picta) living in the wild in Western Wisconsin were colonized with carbapenem-resistant bacteria. Fecal samples from ten turtles were examined for carbapenem-resistant bacteria. None of the isolates were found to be carbapenem resistant by antimicrobial susceptibility testing. However, all the isolates were resistant to other β-lactams and chloramphenicol classes of antimicrobials. One isolate, Acinetobacter oleivorans strain PT8, was selected for additional characterization, including whole-genome sequencing (WGS). Strain PT8 is capable of degrading biodiesel, forming biofilms, and has a putative type 6 gene cluster. Finally, the taxonomic position of the available whole-genome sequences of 25 A. oleivorans genomes from purified isolates was determined.

Clinical Features and Epidemiology ofAcinetobacter baumanniiColonization and Infection in Spanish Hospitals

Objective:

To investigate the clinical features and the epidemiology ofAcinetobacter baumanniiin Spanish hospitals.

Design:

Prospective multicenter cohort study.

Setting:

Twenty-seven general hospitals and one paraplegic center in Spain.

Methods:

All cases ofA. baumanniicolonization or infection detected by clinical samples during November 2000 were included. Isolates were identified using phenotypic and genotypic methods. The molecular relatedness of the isolates was assessed by pulsed-field gel electrophoresis.

Results:

Twenty-five (89%) of the hospitals had 221 cases (pooled rate in general hospitals, 0.39 case per 1,000 patient-days; range, 0 to 1.17). The rate was highest in intensive care units (ICUs). Only 3 cases were pediatric. The mean age of the patients in the general hospitals was 63 years; 69% had a chronic underlying disease and 80% had previously received antimicrobial treatment. Fifty-three percent of the patients had an infection (respiratory tract, 51%; surgical site, 16%; and urinary tract, 11%). Crude mortality was higher in infected than in colonized patients (27% vs 10%; relative risk, 1.56; 95% confidence interval, 1.2 to 2.0;P= .003). Molecular analysis disclosed 79 different clones. In most hospitals, a predominant epidemic clone coexisted with other sporadic clones. Imipenem resistance was present in 39% of the hospitals.

Conclusions:

A. baumanniiwas present in most participating Spanish hospitals (particularly in ICUs) with different rates among them. The organisms mainly affected predisposed patients; half of them were only colonized. Epidemic and sporadic clones coexisted in many centers.

Performance accuracy of antibacterial and antifungal susceptibility test methods: report from the College of American Pathologists Microbiology Surveys Program (2001-2003)

CONTEXT

The College of American Pathologists Microbiology Surveys Program provides external proficiency samples that monitor the performance of nearly 3000 laboratories that perform and report antimicrobial susceptibility tests.

OBJECTIVE

To summarize results obtained with bacterial and yeast challenge samples (2001 through 2003).

DESIGN

One organism every 4 months was tested by surveys participants against antibacterials/antifungals by routinely used methods. Reports were graded by interpretive category (susceptible, intermediate, resistant) based on an 80% consensus of referees/participants.

RESULTS

The most common antibacterial test methods/systems were Vitek (38%-43%), MicroScan (39%-43%), and the disk diffusion test (14%-15%), although Etest was most used for fastidious species. YeastOne was the dominant antifungal test (50%-55%). Antifungal results demonstrated continuous, improved accuracy (83%-88%), highest for YeastOne (96%) and broth microdilution (95%) methods. Antibacterial test accuracy was consistently greater than 97% against gram-positive organism challenges and greater than 98% against gram-negative challenges. For gram-negative strains with well-characterized resistance mechanisms, the accuracy by method was disk diffusion greater than broth microdilution greater than automated systems. Major problems identified were (1) Haemophilus influenzae control ranges require re-evaluation, (2) overuse of beta-lactamase tests, (3) errors among Enterococcus faecium against penicillins (Vitek 2, MicroScan), (4) false-susceptible results with trimethoprim/sulfamethoxazole against coagulase-negative staphylococci (MicroScan), (5) macrolide false-susceptibility for beta-hemolytic streptococcus (MicroScan), (6) flawed reporting for antimicrobials not active at the infection site, (7) use of outdated interpretive criteria, and (8) failure to follow Clinical and Laboratory Standards Institute testing/reporting recommendations.

CONCLUSIONS

Susceptibility tests were generally performing satisfactorily as measured by the surveys, but serious errors were identified with some drug/organism combinations that may require action by the Clinical and Laboratory Standards Institute and/or the Food and Drug Administration.

Integron-associated imipenem resistance in Acinetobacter baumannii isolated from a regional hospital in Taiwan

We investigated the genetic properties of imipenem-resistant Acinetobacter baumannii collected from a regional hospital in Taiwan. Pulsed-field gel electrophoresis demonstrated that the isolates were genetically diverse. Polymerase chain reaction, DNA sequencing, and DNA-DNA hybridisation showed that the bla(IMP-1) gene resided as a cassette in a plasmid-borne class 1 integron in two isolates. The majority of the resistant isolates were plasmid-less and carried no bla(IMP), bla(VIM) or bla(CFI) genes, indicating that other uncharacterised metallo-beta-lactamases or mechanisms other than enzyme production are involved in carbapenem resistance in this group of A. baumannii. We conclude that multidrug resistance of A. baumannii was a combined effect of lateral gene transfer and clonal spread of multiple resistant clones. Strict measures should be implemented to control the further spread of resistance.

Variable resistance patterns of integron-associated multidrug-resistant Acinetobacter baumannii isolates in a surgical intensive care unit

Between 1998 and 2000, we characterized 91 nosocomial isolates of Acinetobacter baumannii by antibiotyping and genotyping. A total of 25 ribotypes were obtained among these 91 isolates. When the isolates from surgical intensive care units (ICUs) and other wards were compared, multiresistant A. baumannii isolates with the same ribotype 25 (R-25) were significantly more prevalent in nosocomial infections among the surgical patients. Further subtyping of the strains by pulsed-field gel electrophoresis confirmed that strains of the same ribotype in surgical ICUs and a few isolates from other wards were identical or clonally related. Different antibiotic resistance profiles were observed among these R-25 isolates. All R-25 isolates contained intI1 integrase, and two clusters of integron cassettes were found. These clusters of cassettes were encoded by an open reading frame (ORF) of -5'CS-aac(3)Ia-aadA1a-unknown or f-3'CS or 5'CS-aacA4-aadA1-catB8-3'CS, indicating the involvement of different resistant genes. Two isolates contained bla (IMP-1), which was acquired from a conjugatively transferable plasmid and did not involve integron-associated resistance. In conclusion, an epidemic of nosocomial infections associated with A. baumannii strains that have different resistance profiles was identified. Resistance profiles can change by a combination of plasmid- and integron-associated acquisition, especially in a unit with high antibiotic selective pressures. Infectious control personnel should be alert to the change in resistance profiles during routine monitoring.

Antibiotic susceptibility and REP-PCR fingerprints of Acinetobacter spp. isolated from a hospital ten years apart

The antibiotic susceptibility profiles and the repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR)-determined genotypes of 109 Acinetobacter strains collected from the University Malaya Medical Center (UMMC), Kuala Lumpur, Malaysia, in 1987 (N=21) and 1996-1998 (N=88) were established. Twelve antibiotic susceptibility profiles of antibiotics used at the UMMC were obtained. In descending order of effectiveness, imipenem, amikacin and ciprofloxacin were the most effective against the Acinetobacter strains. Compared with 1987 isolates, the isolates obtained in 1996-1998 had decreased susceptibility to these antibiotics and were tolerant to the antibiotics up to an MIC90 of > or =256 mg/L. REP-PCR DNA fingerprints of all the isolates revealed the presence of four Acinetobacter spp. lineages; 92% of all the isolates belonged to two dominant lineages (genotypes 1 and 4). Genotype 4 isolates predominant in 1987 showed increased resistance and antibiotic tolerance to imipenem, amikacin and ciprofloxacin compared with the 1996-1998 isolates. In contrast, genotype 1 isolates from 1996-1998 were mainly sensitive to these antibiotics. These findings demonstrate the presence of at least two independent Acinetobacter spp. lineages in the same hospital, and suggest the possibility that genotype 4 Acinetobacter spp. acquired the resistance phenotype in situ, whereas most of the genotype 1 isolates were probably introduced to the hospital in recent years.

Genotypic Characterization of Carbapenem-NonsusceptibleAcinetobacterspp. Isolated in Latin America

The principal aim of this study was to evaluate the genomic diversity among the imipenem-nonsusceptible Acinetobacter spp. (INSA) collected from the Latin American medical centers within the SENTRY Antimicrobial Surveillance Program. The INSA isolates were collected from patients with bloodstream infections, who were hospitalized in seven Latin American countries between 1997 and 1999. For epidemiologic comparison, 20 carbapenem-susceptible Acinetobacter spp. (CSA) isolates were collected in the same period of time from the respective medical centers. A total of 23 Acinetobacter spp. isolates exhibiting imipenem MIC values of >/=8 microg/ml were typed by ribotyping, an automated molecular method. The isolates showing an identical ribogroup were also typed by pulsed-field gel electrophoresis (PFGE). The antimicrobial susceptibility to various antimicrobial agents was evaluated using a reference broth microdilution technique. Among the INSA isolates, 13 distinct ribogroups were observed, whereas 16 ribogroups were detected among the CSA. Nearly 57% of the INSA belonged to only four ribogroups. Identical ribogroups and PFGE patterns were observed among INSA and CSA isolates collected from medical centers located in different countries (Brazil and Argentina). Our results showed: (1) a higher genomic variability among the CSA; (2) presence of epidemic clones among INSA isolates encountered in Latin American medical centers; and (3) spread of INSA and CSA epidemic clones between Latin American countries.

Interhospital transfer of pan-resistant Acinetobacter strains in Johannesburg, South Africa

BACKGROUND

Acinetobacter species infections are increasingly found to cause nosocomial infections, particularly in intensive care units. These pathogens are difficult to eliminate from the hospital environment, and the emergence of multiple-drug-resistant strains complicates patient treatment. In this retrospective study, several strains were analyzed to study the possible spread of pan-resistant strains.

METHODS

Macrorestriction analysis was performed on isolates collected in July 2001 from Johannesburg Hospital and strains collected from a number of hospitals in Johannesburg a year later.

RESULTS

A strain endemic to Johannesburg Hospital that was cefepime and ceftazidime sensitive in 2001 developed resistance to these antibiotics within 1 year. This and other resistant strains were found to have spread among academic and private hospitals in the area by July 2002.

CONCLUSIONS

The development of resistance is believed to be a response to antibiotic pressure and the spread of resistant strains a result of health care worker and/or patient transfer among hospitals. This snapshot epidemiologic study highlights the need to institute stricter infection control measures to limit the spread of organisms such as Acinetobacter among hospitals.

Antimicrobial resistance among gram-negative organisms in the intensive care unit

PURPOSE OF REVIEW

We review the hospital-acquired gram-negative organisms commonly encountered among patients in the intensive care unit and discuss pertinent surveillance data, resistance mechanisms and patterns, and optimal treatment regimens for these pathogens.

RECENT FINDINGS

There has been a notable increase in antibiotic resistance among gram-negative intensive care unit pathogens. Data from surveillance programs such as National Nosocomial Infections Surveillance System, Intensive Care Antimicrobial Resistance Epidemiology, and others have documented undesirable trends in antibiotic resistance, indicating decreasing efficacy of antibiotic classes such as third-generation cephalosporins, carbapenems, and fluoroquinolones, The increased prevalence of extended-spectrum beta-lactamases has contributed to the finding of multidrug resistance among bacteria such as Klebsiella and Escherichia coli. Furthermore, organisms such as Acinetobacter baumannii, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia display intrinsic resistance to many antibiotics, making selection of optimal therapy difficult. Studies have correlated infection by these organisms with prior antibiotic exposure, and containment of the spread of infection can be achieved by careful antibiotic use and infection control practices.

SUMMARY

Antibiotic resistance continues to rise among hospital-acquired gram-negative pathogens. Optimal management of these infections requires knowledge of local epidemiology and practices to control their spread.

Molecular epidemiology and mechanisms of carbapenem resistance in Acinetobacter baumannii endemic in New York City

Multidrug-resistant Acinetobacter baumannii has emerged as a serious nosocomial pathogen in certain areas. In Brooklyn, New York, citywide surveillance revealed that approximately 2 of every 3 isolates were resistant to carbapenem antibiotics. Genetic fingerprinting revealed that 2 strains accounted for 82% of these resistant isolates. Compared with carbapenem-susceptible isolates, carbapenem-resistant isolates had reduced expression of 47-, 44-, and 37-kDa outer-membrane proteins. No specific carbapenemase was found; however, carbapenem-resistant isolates expressed greater levels of a class C cephalosporinase. Although expression of penicillin-binding proteins varied among strains, no consistent pattern appeared to account for carbapenem resistance. An efflux pump, present in several strains, did not appear to contribute to carbapenem resistance. Clonal spread of carbapenem-resistant A. baumannii has occurred in hospitals in Brooklyn. The preliminary findings for a small number of strains suggest that diminished production of outer-membrane porins, together with increased expression of a class C cephalosporinase, appear to be important factors leading to carbapenem resistance in this region.

Impact of antibiotic-resistant pathogens colonizing the respiratory secretions of patients in an extended-care area of the emergency department

OBJECTIVE

To determine the incidence of acquired infection, and the incidence, risk factors, and molecular typing of multidrug-resistant bacterial organisms (MROs) colonizing respiratory secretions or the oropharynx of patients in an extended-care area of the emergency department (ED) in a tertiary-care university hospital.

METHODS

A case-control study was conducted regarding risk factors for colonization with MROs in ED patients from July 1996 to August 1998. The most prevalent MRO strains were determined using plasmid and genomic analysis with PFGE.

RESULTS

MROs colonized 59 (25.4%) of 232 ED patients and 173 controls. The mean ED length of stay for the 59 cases was 13.9 days versus 9.8 days for the 173 controls. The mean length of stay prior to the first isolation of MROs was 9.9 days. MRO species included Acinetobacter baumannii, Staphylococcus aureus, and Pseudomonas aeruginosa. The rate of hospital-acquired infection was 32.7 per 1,000 ED patient-days. The case fatality rate was significantly higher for cases. Univariate analysis identified mechanical ventilation, nebulization, nasogastric intubation, urinary catheterization, antibiotic therapy, and number of antibiotics as risk factors for MRO colonization. Multivariate regression analysis found that mechanical ventilation and nasogastric intubation independently predicted MRO colonization. Endemic clones were identified by PFGE in ED patients and were also found in patients in other parts of the hospital.

CONCLUSIONS

Prolonged stay in the ED posed a risk for colonization with MROs and for contracting nosocomial infections, both of which were associated with increased mortality. Patients colonized with antibiotic-resistant A. baumannii may serve as a reservoir for spread in this hospital.

The impact of Acinetobacter baumannii in the intensive care unit

Acinetobacter baumannii is a significant problem in critically ill patients. It is widespread, can colonise patients quickly and causes virulent infections. However, its overall impact on morbidity and mortality in the critically ill remains unmeasured. This study was designed to investigate A. baumannii colonisation and infection rates in a critically ill population over an 18-month period. Twenty-seven patients from a population of 347 were identified as having A. baumannii. Sixteen were colonised, whereas 11 were infected. Eleven of the 27 patients with A. baumannii died (41%). Of these, eight were colonised and three were infected. In the same period, 320 patients did not have A. baumannii and their mortality rate was 20% (n = 64). The mortality rate of patients with A. baumannii was significantly higher than that of patients without infection.

Pathogen occurrence and antimicrobial resistance trends among urinary tract infection isolates in the Asia-Western Pacific Region: report from the SENTRY Antimicrobial Surveillance Program, 1998-1999

Worldwide surveillance of antimicrobial resistance among urinary tract pathogens is useful to determine important trends and geographical variation for common Gram-positive and -negative species. The most common causative uropathogens often have intrinsic or acquired resistance mechanisms which include ESBL production among enteric bacilli, multi-drug resistant staphylococci and non-fermentative Gram-negative bacilli such as Pseudomonas aeruginosa and Acinetobacter spp. and vancomycin-resistant Enterococcus spp. This study evaluates pathogen frequency and the resistance rates among urinary tract infection (UTI) pathogens in 14 medical centres in the Asia-Pacific region between 1998 and 1999. The isolates were referred to a central monitor for reference NCCLS broth microdilution testing, identification confirmation and patient demographic analysis. Over 50% of the 958 pathogens were Escherichia coli and Klebsiella spp. followed by P. aeruginosa, Enterococcus spp. and Enterobacter spp. Susceptibility for the three enteric bacilli was high for carbapenems (100%), 'fourth-generation' cephalosporins (cefepime 94.9-98.6%) and amikacin (> or = 93.0%). Beta-lactamase inhibitor compounds were more active against E. coli (piperacillin/tazobactam; > 90% susceptible) than the other two enteric species and all other tested agents had a narrower spectra of activity. The rank order of anti-pseudomonal agents was amikacin (91.5% susceptible)> imipenem > piperacillin/tazobactam > tobramycin > ceftazidime and cefepime (77.4 and 76.4% susceptible, respectively). Susceptibility to quinolones for the P. aeruginosa isolates was only 63.2-67.0%. Only one vancomycin-intermediate Enterococcus spp. (van C phenotype) was detected among the 103 strains tested. Newer fluoroquinolones (gatifloxacin; MIC(50), mg/l) were more potent against enterococci than ciprofloxacin (MIC(50), 2 mg/l) and high-level resistance to aminoglycosides was common (41.7%). The data presented are compared to studies of similar design from other areas which are part of the SENTRY surveillance network.

Molecular epidemiology of nosocomial infection associated with multi-resistant Acinetobacter baumannii by infrequent-restriction-site PCR

Acinetobacter baumannii was considered endemic in a university-affiliated tertiary hospital. A significant increase was noted in the proportion of nosocomial infections associated with this micro-organism from 1996 to 1999, although no apparent clusters could be found. Between July 1998 and February 2000, 58 nosocomial isolates of A. baumannii were collected and characterized by antibiotyping and a genotyping method, infrequent-restriction-site PCR (IRS-PCR). High resistance to the 14 antimicrobial agents examined was observed among the isolates. Of the 13 antibiograms detected, eight were multi-resistant to gentamicin and almost all of the traditional and extended-spectrum beta-lactams. These multi-resistant strains consisted of 41 isolates (71%), distributed amongst different wards and intensive care units (ICUs). By IRS-PCR, 23 types were obtained, with one major type found among 28 (48%) isolates. All of these 28 isolates were collected from surgical ICUs. It appears that a single strain of multi-resistant A. baumannii was responsible for the prevalence of nosocomial infection amongst surgical patients, clearly differentiating this outbreak from the previous endemic situation. An efficient molecular typing method played a vital role in making this discrimination.

Emerging importance of multidrug-resistant Acinetobacter species and Stenotrophomonas maltophilia as pathogens in seriously ill patients: geographic patterns, epidemiological features, and trends in the SENTRY Antimicrobial Surveillance Program (1997-1999)

As part of the SENTRY Antimicrobial Surveillance Program, a total of 1078 Acinetobacter species and 842 Stenotrophomonas maltophilia isolates were collected between January 1997 and December 1999 from 5 geographic regions (Canada, the United States, Latin America, Europe, and the Asia-Pacific). The frequency of infections (by geographic region and body site), including those due to imipenem-resistant Acinetobacter species and trimethoprim-sulfamethoxazole (TMP-SMZ)-resistant S. maltophilia, was evaluated. The possibility of seasonal variations in bloodstream infections caused by Acinetobacter species was studied, as was the activity of several therapeutic antimicrobials against all strains. Acinetobacter species and S. maltophilia were most frequently associated with pulmonary infections, independent of the region evaluated. In contrast, patterns of antimicrobial resistance markedly varied among distinct geographic regions, especially for nosocomial isolates. Although the carbapenems were the most active antimicrobials against Acinetobacter species, nearly 11.0% of the nosocomial isolates were resistant to this drug group in both regions. TMP-SMZ, ticarcillin-clavulanic acid, gatifloxacin, and trovafloxacin were the only agents with consistent therapeutic activity against S. maltophilia isolates. Rates of resistance to TMP-SMZ ranged from 2% in Canada and Latin America to 10% in Europe. The geographic differences in resistance patterns among Acinetobacter species and S. maltophilia isolates observed in this study emphasize the importance of local surveillance in determining the most adequate therapy for acinetobacter and S. maltophilia infections and the possible clonal, epidemic nature of occurrence.

Increasing threat of Gram-negative bacteria

The widespread use of broad-spectrum antibiotics has led to emergence of antibiotic-resistant strains of many Gram-negative organisms. This problem is particularly serious in critically ill patients, especially those with ventilator-associated pneumonia. Extensive antibiotic resistance has developed in Gram-negative bacteria, due both to innate resistance in some species and the fact that they are highly adept at acquiring antibiotic-resistant determinants from each other. Antibiotic resistance develops through the following three basic mechanisms: alteration of the drug target, prevention of drug access to the target (including actively removing the drug from the bacteria), and drug inactivation. Certain Gram-negative microorganisms are particular problems in the intensive care unit, including Pseudomonas aeruginosa, Acinetobacter spp., Stenotrophomonas maltophilia, and the Enterobacteriaceae. The combination of an increasing population at risk, and the natural virulence and adaptability of Gram-negative bacteria guarantees that critical care physicians will face a persistent and increasing challenge from these pathogens.

Perfil de sensibilidade a antimicrobianos de bactérias isoladas do trato respiratório baixo de pacientes com pneumonia internados em hospitais brasileiros: resultados do Programa SENTRY, 1997 e 1998

Introdução: Pneumonia hospitalar é a mais fatal das infecções hospitalares, com taxas de mortalidade de 30 a 60%. Estima-se que 15% de todas as mortes associadas à hospitalização estejam diretamente relacionadas a pneumonias hospitalares. O SENTRY é um estudo de vigilância de resistência a antimicrobianos envolvendo centros médicos em todo o mundo. Objetivo: Avaliar a sensibilidade a antimicrobianos de bactérias isoladas no trato respiratório baixo de pacientes com pneumonia internados em hospitais brasileiros. Material e métodos: Foram avaliadas 525 amostras bacterianas de 11 hospitais brasileiros, como parte do programa SENTRY. Os isolados foram testados por microdiluição em caldo contra um grande número de antimicrobianos. Resultados: As cinco espécies mais freqüentes foram (n/%): Pseudomonas aeruginosa (158/30,1%), Staphylococcus aureus (103/19,6%), Acinetobacter spp. (68/13,0%), Klebsiella spp. (50/9,5%), e Enterobacter spp. (44/8,4%). Essas cinco espécies representam mais de 80% de toda a amostragem. A P. aeruginosa apresentou altas taxas de resistência à maioria dos antimicrobianos testados. As maiores taxas de sensibilidade foram apresentadas por piperacilina/tazobactam (71,5%) e meropenem (69,0%). Os compostos com maior atividade in vitro contra Acinetobacter spp. foram imipenem e meropenem (80,9% de sensibilidade) seguido pela tetraciclina (63,2%). A sensibilidade das amostras de Klebsiella spp. foi muito baixa. MICs > ou = 2mig/mL para ceftriaxona ou ceftazidima, indicando produção de ESBL, foram encontrados em 36,0% das amostras. Os antimicrobianos mais ativos contra Klebsiella spp. foram os carbapenens (100% de sensibilidade) e as quinolonas (92,0% de sensibilidade). Ceftriaxona foi ativa contra somente 56,8% das amostras de Enterobacter spp. (MIC50, 1mig/mL), enquanto a cefepima foi ativa contra 88,6% destes isolados (MIC50, <= 0,12mig/mL). A resistência à oxacilina foi detectada em 43,7% dos isolados de S. aureus. As drogas mais ativas contra essa espécie foram: vancomicina, teicoplanina, quinupristin-dalfopristin e linezolida. Conclusões: Os resultados do presente estudo mostraram alta prevalência de Acinetobacter spp. e altas taxas de resistência entre bacilos gram-negativos quando comparados com resultados de estudos norte-americanos e europeus.

Endemic carbapenem-resistant Acinetobacter species in Brooklyn, New York: citywide prevalence, interinstitutional spread, and relation to antibiotic usage

Acinetobacter species are problematic nosocomial pathogens. In November 1997, pathogens isolated by microbiology laboratories were collected from 15 hospitals in Brooklyn, New York. Acinetobacter species accounted for 10% of gram-negative isolates. Only half of Acinetobacter species were susceptible to carbapenems; 11 hospitals had at least 1 isolate resistant to carbapenems. Other Acinetobacter susceptibility rates were as follows: polymyxin, 99%; amikacin, 87%; ampicillin/sulbactam, 47%; ceftazidime, 25%; and ciprofloxacin 23%. Overall, 10% were resistant to all commonly used antibiotics. Genetic analysis by use of pulsed-field gel electrophoresis of 12 carbapenem-resistant isolates revealed 4 strains that were recovered from >1 hospital, which suggests interinstitutional spread. Antibiotic usage data from 11 hospitals revealed that the use of third-generation cephalosporins was associated significantly with the percentage of carbapenem-resistant strains (P=.03). Resistant Acinetobacter species have become endemic in Brooklyn, New York. Citywide strategies that involve surveillance, infection-control practices, and the reduction of antibiotic usage may be necessary to control the spread of these pathogens.

Activity and spectrum of 22 antimicrobial agents tested against urinary tract infection pathogens in hospitalized patients in Latin America: report from the second year of the SENTRY antimicrobial surveillance program (1998)

The potency and spectrum of various antimicrobial agents tested against 434 bacterial isolates causing urinary tract infection (UTI) in hospitalized patients in Latin America were evaluated. The genotypes of the extended-spectrum beta-lactamase-producing and selected multi-resistant isolates were also evaluated by molecular typing techniques. Escherichia coli (60.4%) was the most common aetiological agent causing UTI, followed by Klebsiella spp. (11.2%) and Pseudomonas aeruginosa (8.3%). In contrast, Enterococcus spp. isolates caused only 2.3% of UTIs. Fewer than 50% of E. coli isolates were susceptible to broad-spectrum penicillins. The resistance rates to ciprofloxacin and the new quinolones were also high among these isolates. The molecular characterization of ciprofloxacin-resistant E. coli showed that most of them have a double mutation in the gyrA gene associated with a single mutation in the parC gene. The Klebsiella pneumoniae isolates studied demonstrated high resistance rates to beta-lactam drugs, including broad-spectrum cephalosporins. The carbapenems were the compounds with the highest susceptibility rate among these isolates (100.0% susceptible) followed by cefepime (91.7% susceptible). Meropenem, imipenem and cefepime were also the most active drugs against Enterobacter spp. Among P. aeruginosa isolates, meropenem (MIC(50), 2 mg/L) was the most active compound, followed by imipenem (MIC(50), 4 mg/L), cefepime (MIC(50), 8 mg/L) and ceftazidime (MIC(50), 16 mg/L). The results presented in this report confirm that bacterial resistance continues to be a great problem in Latin American medical institutions.

Outer-membrane proteins pattern and detection of beta-lactamases in clinical isolates of imipenem-resistant Acinetobacter baumannii from Brazil

In order to compare imipenem-sensitive and -resistant Acinetobacter baumannii strains isolated from three patients, ribotyping, plasmid, beta-lactamase detection and outer-membrane analysis were performed. Ribotyping and the use of a beta-lactam during the period when the strains were isolated suggested that they had a common origin and that resistance occurred in vivo. Outer membrane analysis showed no difference between susceptible and resistant strains with the exception of an A2 imipenem-resistant strain that lost a protein band of 31-36 kDa. Beta-lactamases were detected using isoelectric focusing in all strains (pI of 7.4). In addition, two beta-lactamases (pI of 5.9 and 6.7) were found in imipenem-resistant isolates. The double-disc technique demonstrated the presence of a beta-lactamase capable of imipenem inactivation in resistant strains. Plasmid analysis showed that all susceptible strains had the same pattern, one resistant strain did not have any plasmid, one had the same plasmid pattern of its susceptible pair and only one had a different pattern when compared with its susceptible pair.

The genomic diversity of coagulase-negative staphylococci associated with nosocomial infections

A total of 117 isolates of coagulase-negative staphylococci (CNS) were collected from patients in three medical centres. They were genotyped by pulsed-field gel electrophoresis (PFGE) following digestion with restriction enzymes SmaI and SstII. The isolates included Staphylococcus epidermidis, S. simulans, S. hominis, S. lugdunensis, S. capitis, S. saprophyticus, S. caprae and S. sciuri. They were collected at random from 82 patients and were associated with infected central venous lines, continuous ambulatory peritoneal dialysis (CAPD) catheters, endocarditis, osteomyelitis of prosthetic hips and internally fixed fractures. The genetic heterogeneity of the strains was demonstrated by PFGE profiles and two dendrograms. Though the strains were segregated into species, there was no clustering of the strains by type of infection, associated medical unit or geographical location of the patient. Numerous genotypes were identified, suggesting that no specific strains of CNS are associated with prosthetic related infection.

Phenotyping and genotyping methods applied to investigate the relatedness of Brazilian isolates of Enterobacter cloacae

In order to evaluate the resolving power of several typing methods to identify relatedness among Brazilian strains of Enterobacter cloacae, we selected twenty isolates from different patients on three wards of a University Hospital (Orthopedics, Nephrology, and Hematology). Traditional phenotyping methods applied to isolates included biotyping, antibiotic sensitivity, phage-typing, and O-serotyping. Plasmid profile analysis, ribotyping, and macrorestriction analysis by pulsed-field gel electrophoresis (PFGE) were used as genotyping methods. Sero- and phage-typing were not useful since the majority of isolates could not be subtyped by these methods. Biotyping, antibiogram and plasmid profile permitted us to classify the samples into different groups depending on the method used, and consequently were not reliable. Ribotyping and PFGE were significantly correlated with the clinical epidemiological analysis. PFGE did not type strains containing nonspecific DNase. Ribotyping was the most discriminative method for typing Brazilian isolates of E. cloacae.

Antimicrobial susceptibility of bacteria causing urinary tract infections in Latin American hospitals: results from the SENTRY Antimicrobial Surveillance Program (1997)

OBJECTIVE: To evaluate the antimicrobial susceptibility patterns among 469 pathogens isolated as a significant cause of urinary tract infections in 10 Latin American medical centers. METHODS: Consecutively collected isolates were susceptibility tested by broth microdilution methods, and selected isolates were characterized by molecular typing methods. RESULTS: Escherichia coli and Klebsiella spp. isolates revealed high rates of resistance to broad-spectrum penicillins and to fluoroquinolones. Ceftazidime MICs of >/=2 mg/L, suggesting the production of extended-spectrum b-lactamases (ESBLs), were observed in 37.7% of K. pneumoniae and 8.3% of Escherichia coli isolates. Enterobacter spp. isolates were characterized by high resistance rates to ciprofloxacin (35%) and to ceftazidime (45%), but they generally remained susceptible to cefepime (95% susceptible). Pseudomonas aeruginosa and Acinetobacter spp. were highly resistant to ciprofloxacin and ceftazidime. Imipenem was active against 80% of P. aeruginosa and 93% of Acinetobacter spp. isolates. CONCLUSIONS: Our results demonstrate a high level of resistance to various classes of antimicrobial agents among isolates causing nosocomial urinary tract infections in Latin American hospitals. Clonal dissemination of ESBL-producing K. pneumoniae strains was infrequent.

Unusual genetic heterogeneity of Acinetobacter baumannii isolates in a university hospital in Italy

BACKGROUND

Acinetobacter baumannii has become an increasingly important nosocomial pathogen, particularly in intensive care units (ICUs). The aim of this investigation was to study the molecular epidemiology of A baumanii in a university hospital in Italy.

METHODS

All A baumanii isolates were collected and typed with phenotypic and genotypic methods during a 7-month period. A 1-year prospective surveillance of ICU-acquired infections was performed by using the National Nosocomial Infections Surveillance methodology.

RESULTS

A baumanni accounted for 28.4% of all infections and 46.7% of all pneumonia acquired in the ICU, with a nosocomial infection rate of 12.4% or 8 infections per 1000 patient-days. Risk factors for A baumannii acquisition in the ICU were mechanical ventilation and previous use of broad-spectrum antibiotics, whereas administration of carbapenems showed a significant protective effect. Pulsed-field gel electrophoresis of genomic Apa I digests identified at least 5 outbreaks in the ICU caused by 5 different clones, one replacing the other in a well-defined temporal order.

CONCLUSIONS

Whereas the sequential temporal cluster of epidemic clones in the ICU is intriguing and requires further research, the clear evidence of cross-contamination of A baumannii isolates involved with infections in the ICU demands extensive preventive efforts.