Colonization of hospital water systems by Legionella pneumophila, Pseudomonas aeroginosa, and Acinetobacter in ICU wards of Tehran hospitals.

BACKGROUND: Nosocomial infection caused by non-Enterobacteriaceae gram negative bacteria (GNB-NE) is increasing in intensive care units (ICU). AIM: The objective of this study was to determine whether potable water in ICU wards at Tehran hospitals is contaminated with L. pneomophila, P. aeroginosa and Acinetobacter spp. MATERIALS AND METHODS: A total of 52 water samples from shower bath and taps water in seven hospitals of Tehran were collected. The water sample concentrated by filtering through millipore cellulose filters and cultured on BCYE agar and tryptic soya agar media. The presence of Legionella pneumophila was confirmed by real time PCR assay using primers-probe designed for the mip gene. RESULTS: Legionella pneumophila, Pseudomonas aeroginosa and Acinetobacter were isolated from 5 (9.6%), 6 (11.4%) and 1 (1.8%) of the hospital water systems, respectively. This study demonstrated the presence of Legionella, Pseudomonas and Acinetobacter in water system in ICU wards of different hospitals in Tehran. CONCLUSIONS: Hot water from shower heads could be a potential source of infection for Legionella pneumophila. Water was also proved to contain Pseudomonas aeruginonsa, the main GNB-NE causing nosocomila pneumonia at Tehran hospitals. Care should be taken concerning cleanliness and decontamination of water supplies at ICUs for pathogenic organisms.

Hospital acquired pneumonia: comparison of culture and real-time PCR assays for detection of Legionella pneumophila from respiratory specimens at Tehran hospitals.

Legionella pneumophila is an important etiological agent in both hospital and community acquired pneumonia. The sensitivity of culture for isolation of L. pneumophila from clinical specimens is low and time consuming. Similar problem also exists when the method of direct immunofluorescence is used. To detect this organism quantitatively from respiratory specimens, a Taq Man based real-time PCR targeting the mip sequence was developed. Both real-time PCR and culture methods were applied on 262 respiratory specimens from 262 ICU patients with pneumonia admitted to 5 different hospitals in Tehran. The results of real-time PCR were compared with those obtained by culture. Real-time PCR and culture found 12 and 4 specimens, respectively, as positive for L. pneumophila. Its technical specificity (100%) was checked against a panel of microorganisms consisting of both Gram-positive and Gram-negative bacteria. Our real-time PCR assay showed high sensitivity (100%) and specificity (96.9%) and could detect 200 organisms per ml from respiratory specimens. Using real-time PCR as a screening method, the frequency of nosocomial pneumonia with L. pneumophila at Tehran hospitals was estimated as 4.58%.

Direct detection of Pseudomonas aeruginosa from patients with healthcare associated pneumonia by real time PCR.

Using oprL sequences, a TaqMan real time PCR was developed and used for quantitative detection of Pseudomonas aeruginosa from 99 broncoalveolar lavage and 11 sputum specimens collected from patients with health care associated pneumonia. All specimens were cultured on appropriate media to isolate bacteria. Twenty five specimens were positive by both methods. Polymicrobial infections were found in 13 specimens. Amplification of oprL in serial dilutions ranged from 10(9)CFU/ml to 10(2)CFU/ml. Standard curve of duplicated every dilution had slope 3.25±0.1 and R(2)>0.99 with SD 0.1. Our real time PCR assay showed high sensitivity (100%) and specificity (98.85%). This technique could detect and enumerate 100 bacteria directly from clinical specimens and showed that the threshold is 10(3)CFU/ml in cases with clinical symptoms. Our method can be used for quantitative detection of P. aeruginosa from BAL and sputum specimens in 1h and 10min.

Distribution of different carbapenem resistant clones of Acinetobacter baumannii in Tehran hospitals.

The MICs of imipenem, meropenem, piperacillin-tazobactam, cefotaxime, polymixin B and tigecycline against 80 isolates of Acintobacter baumanii from 6 hospitals were determined. A multiplex-PCR was used to detect the genes encoding carbapenemases. Field Inversion Gel Electrophoresis (FIGE) was then used to investigate the genetic relationships among the carbapenem-resistant isolates. Only 7 isolates were resistant to polymixin B and tigecycline (MIC = 16). All isolates were positive for at least 2 carbapenemase genes. At least 10 distinct clones were detected by FIGE. A dominant pattern designated as pulsotype A consisting of 23 isolates was detected from 4 hospitals. The majority of isolates in this pulsotype had a bla(OXA-51/23-like) and bla(OXA-51/24-like) carbapenemase genes and cultured from the patients at burns and ICU. The pan drug resistant isolates belonged to different FIGE patterns. Nosocomial infections with different clones of Acintobacter baumanii occur at Tehran hospitals. However, inter-hospital transmission with certain pulsotypes is likely.