Changes in antibiotic resistance of the most common Gram-negative bacteria isolated in intensive care units

Virulence Constitution of Multi-Drug-Resistant Pseudomonas aeruginosa in Upper Egypt

Purpose

Ventilator-associated pneumonia caused by Pseudomonas aeruginosa (P. aeruginosa) is a major health-care problem. In this study, we explored the epidemiology of virulence determinants among multi-drug-resistant (MDR) clinical P. aeruginosa isolates from hospitalized patients with ventilator-associated pneumonia in intensive care units in Upper Egypt.

Patients and Methods

MDR P. aeruginosa isolates were screened for the presence of eight virulence factors and typed by ERIC-PCR.

Results

A total of 39 clinical MDR isolates were selected out of 173 isolated P. aeruginosa showing a combination of adhesion and cytotoxicity virulence patterns, with the detection of aprA, exoU, exoS, lasB, algD, toxA in 74.3%, 58.9%, 46.1%, 41.2%, 30.7%, 20.5% of the isolates, respectively. The MDR isolates were grouped into 13 different virulence profiles according to the pattern of virulence gene distribution. exoU genotype was more predominant among the P. aeruginosa isolates with more than 48% of the isolates harboring this gene alone, 7% harboring both exoU and exoS and 43.5% harboring exoS gene. An intermediate degree of diversity was detected by ERIC-PCR typing where the isolates were clustered in 7 major groups, indicating possible cross-infection within the hospital.

Conclusion

Our results highlight the increased frequency of virulent P. aeruginosa isolates with a shift to the more virulent cytotoxic exoU genotype. Further hospital infection-control measures are mandatory to control the hospital cross-transmission of these highly virulent isolates. This study could vastly be a help to develop efficient treatment policies against P. aeruginosa induced ventilator-associated pneumonia.

Molecular Detection of the Virulent ExoU Genotype of Pseudomonas aeruginosa Isolated from Infected Surgical Incisions

BACKGROUND

Pseudomonas aeruginosa is one of the major pathogens responsible for hospital-acquired infections, which harbor a wide array of virulence factors. The main aim of this study was to determine the frequency of the virulent ExoU genotype in relation to the ExoS genotype among isolated P. aeruginosa from infected surgical incisions, followed by phylogenetic analysis.

METHODS

A total of 66 P. aeruginosa isolates were identified by cultural and biochemical characteristics. All isolates were tested for antimicrobial susceptibility against the following antimicrobial agents: imipenem, amikacin, gentamicin, amoxycillin, cefotaxime, cefepime, and levofloxacin. Molecular detection of the ExoS and ExoU as well as two other virulence genes was done by polymerase chain reaction (PCR). Sequencing of ExoU gene and phylogenetic analysis was performed.

RESULTS

Approximately 81% of the isolated P. aeruginosa were multi-drug resistant. The ExoS genotype was more prevalent (63%) among the isolates than the ExoU genotype (18%), with 9% of the isolates possessing both toxins. LasB and AprA were detected in 63.6% and 27.2% of the isolates, respectively. An association was observed between the number of virulence genes and the presence of multi-drug resistance. All the ExoU were multi-drug resistant (MDR), whereas 71% of the ExoS were MDR. Phylogenetic analysis of ExoU gene showed a 99% similarity with four different strains.

CONCLUSION

Despite the greater frequency of the ExoS genotype, the presence of the virulent MDR ExoU genotype isolates from surgical site infections is an alarming sign requiring further intervention and investigations.

Virulence Gene Profiles of Multidrug-Resistant Pseudomonas aeruginosa Isolated From Iranian Hospital Infections

Background:

The most common hospital-acquired pathogen is Pseudomonas aeruginosa. It is a multidrug resistant bacterium causing systemic infections.

Objectives:

The present study was carried out in order to investigate the distribution of virulence factors and antibiotic resistance properties of Pseudomonas aeruginosa isolated from various types of hospital infections in Iran.

Patients and Methods:

Two-hundred and seventeen human infection specimens were collected from Baqiyatallah and Payambaran hospitals in Tehran, Iran. The clinical samples were cultured immediately and samples positive for P. aeruginosa were analyzed for the presence of antibiotic resistance and bacterial virulence genes using PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed using disk diffusion methodology with Müeller–Hinton agar.

Results:

Fifty-eight out of 127 (45.66%) male infection specimens and 44 out of 90 (48.88%) female infection specimens harbored P. aeruginosa. Also, 65% (in male specimens) and 21% (in female specimens) of respiratory system infections were positive for P. aeruginosa, which was a high rate. The genes encoding exoenzyme S (67.64%) and phospholipases C (45.09%) were the most common virulence genes found among the strains. The incidences of various β-lactams encoding genes, including bla_TEM, bla_SHV, bla_OXA, bla_CTX-M, bla_DHA, and bla_VEB were 94.11%, 16.66%, 15.68%, 18.62%, 21.56%, and 17.64%, respectively. The most commonly detected fluoroquinolones encoding gene was gyrA (15. 68%). High resistance levels to penicillin (100%), tetracycline (90.19%), streptomycin (64.70%), and erythromycin (43.13%) were observed too.

Conclusions:

Our findings should raise awareness about antibiotic resistance in hospitalized patients in Iran. Clinicians should exercise caution in prescribing antibiotics, especially in cases of human infections.

Influencing the use of antibiotics in a Chinese pediatric intensive care unit

OBJECTIVES

To demonstrate the effectiveness of an intervention in antibiotics prescribing, and evaluate the use of antibiotics in the pediatric intensive care unit (PICU) at the Beijing Children's Hospital.

METHODS

Our interventions included (1) educating the pediatricians on antibiotics prescribing, (2) applying an antimicrobial spectrum chart, and (3) controlling the prescription of specific antibiotics with the use of a guideline. Nine hundred clinical records, including clinical information and antibiotic usage data, were selected retrospectatively from the PICU admissions during the pre- and post-intervention periods.

RESULTS

In this 5-year survey, the mean rate of antibiotic prescribing was greater than 95% in the PICU. More than 76% of the prescriptions were started empirically. The most frequently used antibiotics were third-generation cephalosporins. After the intervention, we found a reduction in the rate of antibiotic cost/patient/day (P < 0.05); a decrease in the prescription rate of third-generation cephalosporins and macrolides (P < 0.01); an increase in the prescription rate of beta-lactam/beta-lactamase inhibitors and second-generation cephalosporins (P < 0.01); a reduction in the empiric treatment (P < 0.01); and a significant reduction in the incidence rates of bacterial resistance for imipenem-, cefepime-, and ceftazidime-resistant Pseudomonas aeruginosa (P < 0.05), and cefepime-resistant Escherichia coli and Klebsiella pneumoniae (P < 0.01).

CONCLUSION

Our interventions led to a significant reduction of broad-spectrum antibiotic prescribing associated with the significant reduction in bacterial resistance in the PICU. The implementation of the antibiotics guideline appeared to be effective.

Antimicrobial usage in paediatric intensive care units in China

AIM

The aim of the study was to determine antimicrobial usage in paediatric intensive care units (PICUs) in China.

METHODS

Data were equally collected from 540 charts of PICUs in the three Chinese tertiary teaching children hospitals in 2006. The data included demographic, clinical data and those on antimicrobial usage and results of microbiological examinations.

RESULTS

Of the 540 cases, 524 (94.7%) patients received at least one antimicrobial agent. The main treatment started empirically in 387 (71.6%). The third-generation cephalosporins were the major antimicrobials used in all participating hospitals, accounting for 227 (31%). Bacteria were isolated from 48%, 68% and 59% of the three PICUs. Six common pathogens accounted for more than 75% of the isolated bacteria. The rates of Escherichia coli isolates resistant to cefotaxime were 73.8%, 58.3% and 49.2%, respectively, with the rate being higher in H1 than in H2 and H3 (both p<0.01).

CONCLUSIONS

Irrational use of antimicrobials exists in clinical practice of PICUs in China. It is recommended that antimicrobial usage should be guided by bacterial isolation and antimicrobial susceptibility tests in order to select correct antimicrobials and to prevent emergency of drug-resistant strains in PICUs.