Five-year evaluation of frequency of occurrence and antimicrobial susceptibility patterns of bacteria from bloodstream infections in Children's Medical Center (CMC) Hospital in Tehran, Iran, 2001 – 2005

Seyed Alireza Sadr 1, Setareh Mamishi 2, Babak Pourakbari 3

1 Medical Student of Tehran University of Medical Sciences

2 Department of Pediatric Infectious Disease, Children’s Medical Center Hospital, School of Medicine,

3 Infectious Diseases Research Center, Tehran University of Medical Sciences

Clinically significant bacteraemia is a serious consequence of a wide variety of many initially localized infections. Bloodstream infections (BSI) due to bacterial and fungal pathogens affect over 200,000 individuals annually in the United States alone and are a tremendously important cause of morbidity and mortality worldwide, and septicaemia is the 13th leading cause of death. Many studies have found that inadequate empirical therapy of bacteraemic infections is associated with adverse outcomes, including increased mortality. The epidemiology of invasive bloodstream pathogens has changed dramatically over the years. The change in the incidence and epidemiology of infecting organisms has also brought about an increase in resistance to many antibiotic compounds. Appropriate surveillance is also essential to monitor resistance trends and help to identify the factors that may be driving them. Such knowledge is a prerequisite to implementing rational measures to tackle the resistance problem. Resistance data derived from surveillance studies can provide crucial information for the understanding of the spread of antibiotic resistance and encourage the prudent use of antibiotics, a key component in controlling the emergence and spread of resistance.

Objectives:

To provide crucial information for the understanding of the spread of antibiotic resistance and encourage the prudent use of antibiotics, a key component in controlling the emergence and spread of resistance.

Method and Material:

We reviewed the antimicrobial susceptibility patterns of bloodstream isolates of all kind of pathogens in 25,223 blood cultures at children medical center, Tehran, Iran from 2001 to 2005. All isolates were recovered from aerobic blood culture bottles and only one isolate was allowed from each patient. Data regarding the clinical significance of each isolate and whether the BSI was community or hospital acquired was not available. The antimicrobial agents selected for analysis were those commonly included in the treatment of BSI or septicemia patients in Iran. Antimicrobial susceptibility results were rounded down if <0.5 and were presented as whole numbers if
0.5

Result:

Of 25,223 blood cultures examined in this investigation, 2581 (10.23 %) were positive for bacterial growth. The frequency of isolation of Gram-positive bacteria was 47.5% (1228 of 2581) of all isolated microorganisms, and the remaining 52.5% (1353 of 2581) were Gram negative. Overall, staphylococci were the most frequent group of organisms recovered from our blood cultures, comprising 1036 (40.1%) of all bacteria recovered from blood cultures. Five groups of organisms, including Pseudomonas aeruginosa, CoNS, S. aureus, Escherichia coli and Klebsiella spp. were the most frequently isolated organisms or groups of organisms recovered from blood specimens of patients with BSI in this study. Pseudomonas aeruginosa were the most prevalent Gram-negative BSI pathogen isolated, comprising 69.7% of the Gram-negative organism bloodstream isolates. In statistical evaluations, during 5 years of the study (2001-2005), the most frequency of positive cultures belongs to year 2004. Frequency of resistance in all isolated pathogens was higher in comparison with our last report from this center. The rates of oxacillin resistance for S. aureus and CoNS isolates were similar (85.9% versus 89.3%); however, the rate of S. aureus vancomycin resistance was almost twice that of CoNS resistance (35% versus 18.9%). About 45% of S. pneumoniae were resistant to co-trimoxazole and approximately 98% to penicillin. Among Gramnegative isolates, the Chloramfenicol was the most active antibiotic against E. coli, Klebsiella pneumoniae, and Enterobacter species, with between 53% and 77% of all isolates being susceptible. P. aeruginosa was the first most common Gram-negative with 943 isolates evaluated. This pathogen showed extremely high rates of resistance to the majority of the antimicrobial agents tested. The most active compound against this pathogen in our center was the Carbencillin (38.2%).

Conclusion:

There were notable differences in the order of the five most common organisms isolated from blood cultures, which can help set priorities for focused control efforts. Our findings highlight the importance of a nationwide surveillance program to monitor the trends in isolation frequency of bacteria and their antimicrobial resistance patterns throughout Iran.