Pseudomonas aeruginosa Population Structure Revisited

At present there are strong indications that Pseudomonas aeruginosa exhibits an epidemic population structure; clinical isolates are indistinguishable from environmental isolates, and they do not exhibit a specific (disease) habitat selection. However, some important issues, such as the worldwide emergence of highly transmissible P. aeruginosa clones among cystic fibrosis (CF) patients and the spread and persistence of multidrug resistant (MDR) strains in hospital wards with high antibiotic pressure, remain contentious. To further investigate the population structure of P. aeruginosa, eight parameters were analyzed and combined for 328 unrelated isolates, collected over the last 125 years from 69 localities in 30 countries on five continents, from diverse clinical (human and animal) and environmental habitats. The analysed parameters were: i) O serotype, ii) Fluorescent Amplified-Fragment Length Polymorphism (FALFP) pattern, nucleotide sequences of outer membrane protein genes, iii) oprI, iv) oprL, v) oprD, vi) pyoverdine receptor gene profile (fpvA type and fpvB prevalence), and prevalence of vii) exoenzyme genes exoS and exoU and viii) group I pilin glycosyltransferase gene tfpO. These traits were combined and analysed using biological data analysis software and visualized in the form of a minimum spanning tree (MST). We revealed a network of relationships between all analyzed parameters and non-congruence between experiments. At the same time we observed several conserved clones, characterized by an almost identical data set. These observations confirm the nonclonal epidemic population structure of P. aeruginosa, a superficially clonal structure with frequent recombinations, in which occasionally highly successful epidemic clones arise. One of these clones is the renown and widespread MDR serotype O12 clone. On the other hand, we found no evidence for a widespread CF transmissible clone. All but one of the 43 analysed CF strains belonged to a ubiquitous P. aeruginosa “core lineage” and typically exhibited the exoS+/exoU− genotype and group B oprL and oprD alleles. This is to our knowledge the first report of an MST analysis conducted on a polyphasic data set

Epidemiology of community-acquired Pseudomonas aeruginosa infections in children

The epidemiology of community-acquired Pseudomonas aeruginosa infections in children during a one-year period (January through December 1993) was evaluated, A total of 6,859 clinical samples, each one representing a separate individual with suspected infection, were cultured. Pseudomonas aeruginosa was isolated from 218 children with various infections occurring in the following order of frequency: chronic suppurative otitis media, 76.3%; appendicitis/peritonitis, 10.3%; osteomyelitis, 8.9%; skin or soft tissue infection, 6.3%; acute conjunctivitis, 3.0%; and urinary tract infection, 0.1%. A variety of O serogroups were identified: O1 (15.2%), O6 (14.7%), O11 (12.4%), O10 (11.5%), O3 (10.6%), O5 (5.1%), and O9 (4.6%), Other serogroups and nontypable strains were recovered at a frequency of 11.2% and 14.7%, respectively, Nontypable strains predominated in chronic otitis media (18.9%), while serogroups O1 (18.3%), O6 (17.5%), and O11 (17.5%) were recovered most frequently among the typable isolates, Susceptibility of Pseudomonas aeruginosa to antipseudomonadal agents was extremely high. The rate of susceptibility to ceftazidime was 99.6%, to azlocillin 98.6%, to piperacillin 98.2%, to aztreonam 97.3%, to gentamicin and netilmicin 97.7%, and to ciprofloxacin 99.1%, All isolates were susceptible to tobramycin, imipenem, and amikacin. The results might suggest that community-acquired Pseudomonas aeruginosa infections in children can be treated successfully with any antipseudomonadal antibiotic

Risk factors for nosocomial infections caused by Gram-negative bacilli

Two hundred and ninety-nine Gram-negative hospital-acquired infections room 257 patients, consecutively identified during one month (November 1992) in five hospitals in the greater Athens area, were divided into four groups on the basis of the bacterium isolated: Group 1 (Escherichia coli group) included infections owing to E. coli, Group 2 (Proteus group) consisted of infections owing to Proteus spp. and Providencia spp., Group 3 (Kiebsiella/Enterobacter group) involved infections owing to Kiebsiella spp., Enterobacter spp., Citrobacter spp. and Serratia spp. Infections owing to Pseudomonas spp. and other non-fermenters were allocated into Group 4 (non-fermenters group). The four groups were studied in relation to risk factors including the duration of hospitalization, type of ward, underlying disease, history of operation, medical procedures/devices and antimicrobial therapy. A stepwise multiple logistic regression technique (SPSS Inc) was used to analyse the data, and the three groups (the Proteus group, the Klebsiella/Enterobacter group and the non-fermenters group) were analysed separately against the E. coli group. Infections with the Kiebsiella/Enterobacter group were associated with: (a) length of hospital stay before the infection, (b) treatment with newer antibiotics, and (c) hospitalization in an intensive-care unit (ICU). Infections with non-fermenters were associated with: (a) length of hospital stay before infection, (b) a urinary catheter, (c) type of disease (chronic infection being negatively associated), (d) treatment with newer antibiotics and (e) hospitalization in an ICU. Proteus group infections were associated with (a) length of hospital stay before infection, (b) treatment with newer antibiotics and (c) operation during present hospitalization (negative association). Interestingly, no specific hospitals were identified as risk factors. Identification of patients at risk for acquiring an infection owing to a nosocomial pathogen is vital in the development of a preventive strategy for hospital-acquired infections

In vitro activity of loracarbef against TEM extended-spectrum beta-lactamase-producing Escherichia coli strains and its interaction with the enzymes

The in vitro activity of loracarbef was evaluated against Escherichia coli strains producing TEM extended-spectrum beta-lactamases (ESBLs). The MICs of loracarbef were lower than those of cefaclor and cephalothin. The antibiotic was active (MICs less than or equal to 2 mg/l) against strains producing TEM-6, TEM-8, TEM-10, TEM-16, TEM-26 and TEM-28 beta-lactamases. The MICs for TEM-3-, TEM-5- and TEM-24-producing strains were higher (greater than or equal to 16 mg/l). Hydrolysis studies indicated that the latter beta-lactamases inactivated loracarbef more efficiently than the remaining TEM-type ESBLs examined

Expanded-spectrum cephalosporin resistance in non-typhoid Salmonella

Expanded-spectrum cephalosporins (ESCs) such as ceftriaxone, together with fluorinated quinolones, are the choice antibiotics in the treatment of invasive salmonella infections. Resistance to ESCs among non-typhoid salmonella has been recognised since the late 1980s. Currently, ESC-resistant salmonella strains are reported world-wide and in some areas their incidence is significant. Resistance is mainly due to acquisition of multi-resistant plasmids encoding a variety of extended- spectrum and AmpC-type beta-lactamases. The origins of ESC-resistant salmonellae are diverse. Exchange of resistance determinants between salmonellae and nosocomial enterobacteria seems to be frequent, at least in developing countries. Also, the use of newer beta-lactams in animal husbandry and veterinary medicine may have facilitated the spread of ESC-resistant salmonella strains in livestock. (C) 2004 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved