Distribution and Characteristics of Bacteria Isolated from Cystic Fibrosis Patients with Pulmonary Exacerbation.

Background: Cystic fibrosis (CF) is an inherited recessive disorder characterized by recurrent and persistent pulmonary infections, resulting in lung function deterioration and early mortality. Methods: A cross-sectional study was conducted on the bacterial profile and antibiotic resistance pattern of 103 respiratory specimens from CF patients with signs of pulmonary exacerbation. Antibiotic susceptibility testing and biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa isolates were performed by the Kirby-Bauer disc diffusion method and microtiter plate assay, respectively. Molecular typing of S. aureus and P. aeruginosa isolates was carried out by spa typing and repetitive extragenic palindromic element PCR. Results: In a total of 129 isolates, the most prevalent organisms were S. aureus (55.3%) and P. aeruginosa (41.7%). Other less prevalent bacterial isolates include coagulase-negative staphylococci, Escherichia coli, klebsiella spp., Enterobacter spp., and Achromobacter xylosoxidans. The highest rate of resistance for S. aureus was observed to azithromycin and erythromycin (80%), ciprofloxacin (52.3%), clindamycin (44.6%) and tetracycline (43%). Twenty percent of S. aureus isolates were methicillin-resistant S. aureus (MRSA) and 47.6% were MDR S. aureus. For P. aeruginosa isolates the highest resistance was to cefepime (38.3%) and levofloxacin (33.3%) and 20% showed MDR phenotype. Conclusion: Our study demonstrated a significant decline in the prevalence of P. aeruginosa infections in comparison to previous studies. We found S. aureus to be more prevalent in younger patients, whereas mucoid P. aeruginosa showed a shift in prevalence toward older ages. Molecular typing methods showed great diversity between isolates.

Molecular detection of Bordetella holmesii in two infants with pertussis-like syndrome: the first report from Iran.

BACKGROUND AND OBJECTIVES: Bordetella holmesii is associated with a pertussis-like respiratory syndrome in healthy individuals and also a rare cause of septicaemia, endocarditis, pneumonia, and septic arthritis, mostly in immunocompromised patients. Culture technique and real-time PCR are 2 methods used to detect Bordetella spp. MATERIALS AND METHODS: In this study, 435 nasopharyngeal specimens of patients with suspected whooping cough were checked for the presence of B. holmesii using 2 methods of culture technique and real-time PCR. RESULTS: In this study, we detected hIS1001 and IS481 of B. holmesii in 2 infants suspected of having pertussis-like syndrome. CONCLUSION: Our observations demonstrate that accurate diagnosis is needed to discriminate between B. holmesii and B. pertussis infections among pertussis cases; otherwise, it could lead to misestimating pertussis rate and vaccine efficacy.

The First Macrolide-Resistant Bordetella pertussis Strains Isolated From Iranian Patients.

BACKGROUND: Whooping cough was considered as one of the major causes of childhood morbidity and mortality worldwide. Resistant isolates of Bordetella pertussis to macrolides in some countries have been recently reported. OBJECTIVES: Recent reports on macrolide-resistant B. pertussis isolates and lack of evidence for such resistance in clinical isolates of the Iranian patients led the authors of the current study to study antibiotic susceptibility of the collected isolates in the country. Susceptibility of the B. pertussis isolates to three antibiotics was studied. Relatedness of the strains recovered in this research was also examined. MATERIALS AND METHODS: The antibacterial activities of erythromycin, azithromycin, and clarithromycin antibiotics against the recovered isolates of 779 nasopharyngeal swabs were examined using MIC (Minimum Inhibitory Concentration) method. Relationship of the strains was characterized by Pulsed-field Gel Electrophoresis (PFGE). RESULTS: Among the specimens, 11 cases (1.4%) were culture-positive. Among these isolates, only two isolates had high MIC values for erythromycin and clarithromycin. Pulsed-field gel electrophoresis analysis of the isolates revealed 6 PFGE profiles (A-F) among which three and two isolates had the same patterns in profiles A and B, respectively. CONCLUSIONS: Azithromycin can be a good drug of choice to treat patients infected by B. pertussis in Iran. Clonal relationship of the isolates showed that the same B. pertussis strains were isolated from different patients in Iran.

Comparison of culture and real-time PCR for detection of Bordetella pertussis isolated from patients in Iran.

BACKGROUND AND OBJECTIVE: Due to contagiousness of pertussis, a rapid and sensitive method for diagnosis is required to initiate the treatment and interrupt its transmission. MATERIALS AND METHODS: To detect B. pertussis strains, we used two real-time PCR targeting IS481 and BP283 sequences and compared factors influencing culture and real-time PCR results. RESULTS: Totally, 779 specimens were collected from patients among which 11 (1.4%) were culture positive. Using IS481 and BP283 primers, 122 (15.6%) and 100 (12.8%) were diagnosed as infected specimens respectively. There were significant relationships between the real-time PCR method for diagnosis of B. pertussis and age, sex and vaccination of patients before sampling. CONCLUSION: The real-time PCR is superior and much more sensitive than culture for diagnosis of B. pertussis. However, the sensitivity was improved when both IS481 and BP283 were used. Correct sampling and transportation of specimen also improved the detection rate in our research.

Molecular characterization of CTX-Mß-lactamases among Klebsiella pneumoniae isolated from patients at Tehran hospitals.

PURPOSE: Plasmid-encoded CTX-M-group of extended-spectrum ß-lactamases (ESBLs) represent a significant and rapidly emerging problem in most part of the world. The aim of the present study was to describe the prevalence of CTX-M producing Klebsiella pneumoniae at Tehran hospitals. MATERIALS AND METHODS: Clinical isolates of K. pneumoniae (n=250) were collected from 10 hospitals of Tehran. Susceptibility to antimicrobial agents, MIC of cefotaxime and ESBLs production of collected isolates were detected. All ESBL-producing isolates were screened for bla CTX-M genes using PCR and DNA sequencing. Molecular typing of bla(CTX-M) harboring isolates was performed by Pulsed-field gel electrophoresis assay. RESULTS: Of 250 K. pneumoniae clinical isolates, 102 isolates revealed ESBLs - phenotype. PCR assay and sequencing detected bla(CTX-M) genes in 71.5% (n= 73) of ESBL-producing isolates. The prevalence of CTX-M -I and CTX-M-III clusters among these isolates was 35.61% (n=26) and 21.9 % (n=16) respectively. Coexistence of CTX-M -I and CTX-M-III clusters was found among 42.5% (n= 31) of isolates. Of 102 isolates that were positive in the phenotypic confirmatory test (PCT), 29 isolates (28.4%) did not produce any amplicons in PCR for bla(CTX-M) gene. The results of PCR for CTX-M -II and CTX-M-IV clusters were also negative. Analysis of the 31 CTX-M producing K. pneumoniae isolates by PFGE typing showed 26 distinct patterns. CONCLUSIONS: The bla CTX-M genes are widespread among Iranian isolates of K. pneumoniae. PFGE demonstrated the high diversity of K. pneumoniae harboring bla(CTX-M) in our study.

Identification and genetic characterization of metallo-beta-lactamase-producing strains of Pseudomonas aeruginosa in Tehran, Iran.

Metallo-beta-lactamases (MBLs) are being reported with increasing frequency worldwide. The aim of this study was to investigate the prevalence of blalMP-1, blaVIM-1,2 and blaSPM-1 genes encoding metallo-beta-lactamases (MBLs) among a collection of Pseudomonas aeruginosa strains isolated from patients at different hospitals in Tehran and to trace the disseminated clones at these hospitals by pulsed field gel electrophoresis (PFGE). Susceptibility of 610 P aeruginosa to 14 different antibiotics was determined using disc diffusion method. Isolates showing resistance to imipenem and ceftazidime were subjected to micro broth dilution assay to determine their MIC values. The blaIMP-1, blaVIM-1, blaVIM-2, and blaSPM-1, genes were amplified by PCR. Isolates containing blaVIM-1 were analyzed by PFGE. Sixty-eight isolates were resistant to imipenem (MIC > or = 4 microg/ml) of which 16 isolates carried blaVIM-1 gene using PCR assay. No other MBL genes were detected in this study. Three different unrelated patterns were found for isolates containing blaVIM-1 gene by PFGE of which pattern A was predominant. All isolates were susceptible to colistin and polymixin B. blaVIM-1 was the main gene encoding MBL among the isolates of P aeruginosa in our study. Clonal spread of isolates containing blaVIM-1 had occurred at Tehran hospitals. However, heterogeneous clones also were involved in the outbreaks.

Prevalence of ESBLs genes among multidrug-resistant isolates of Pseudomonas aeruginosa isolated from patients in Tehran.

Drug susceptibility testing and PCR assay were used to determine the antibiotic susceptibility patterns and prevalence of genes encoding five different extended spectrum betalactamases (ESBLs) (PER, VEB, SHV, GES, and TEM) among 600 isolates of Pseudomonas aeruginosa cultured from patients at two hospitals in Tehran. Susceptibility of isolates to 12 different antibiotics was tested using disk diffusion method. The MICs for ceftazidime and imipenem were also determined using microbroth dilution assay. Isolates showing MICs >or=16 for ceftazidime were subjected to PCR targeting bla(SHV), bla(PER), bla(GES), bla(VEB), and bla(TEM) genes that encode ESBL. The rates of resistance were as follows: tetracycline (92%), carbenicillin (62%), cefotaxime (56%), ceftriaxon (53%), piperacilin (46%), gentamicin (31%), piperacilin/tazobactam (28%), ceftazidime (25%), amikacin (23%), ciprofloxacin (19.5%), and imipenem (6%). Thirty-nine percent of isolates (n = 234) showed MICs >or=16 microg/ml for ceftazidime, and 5.45% showed MICs >or=16 microg/ml for imepenem. The imipenem-resistant isolates showed high rate of susceptibility to colistin (89%) and polymixin B (95.5%). The frequency of bla(VEB), bla(SHV), bla(PER), bla(GES), and bla(TEM) among the ESBL isolates (MIC >or=16) were 24%, 22%, 17%, 0%, and 9%, respectively. Isolates containing bla(VEB) were resistant to almost all tested antibiotics except imepenem. This is the first report on the existence of bla(VEB), and bla(PER) in Iran. Colistin and polymixin B are highly potent against the imipenem-resistant isolates of P. aeruginosa.