Association between Beta-lactam Antibiotic Resistance and Virulence Factors in AmpC Producing Clinical Strains of P. aeruginosa

OBJECTIVES: The purpose of this study was to determine the presence of IMP and OXA genes in clinical strains of Pseudomonas aeruginosa (P. aeruginosa) that are carriers of the ampC gene. METHODS: In this study, 105 clinical isolates of P. aeruginosa were collected. Antibiotic resistance patterns were determined using the disk diffusion method. The strains carrying AmpC enzymes were characterized by a combination disk method. Multiplex-PCR was used to identify resistance and virulence genes, chi-square test was used to determine the relationship between variables. RESULTS: Among 105 isolates of P. aeruginosa, the highest antibiotic resistance was to cefotaxime and aztreonam, and the least resistance was to colictin and ceftazidime. There were 49 isolates (46.66%) that showed an AmpC phenotype. In addition, the frequencies of the resistance genes were; OXA48 gene 85.2%, OXA199, 139 3.8%, OXA23 3.8%, OXA2 66.6%, OXA10 3.8%, OXA51 85.2% and OXA58 3.8%. The IMP27 gene was detected in 9 isolates (8.57%) and the IMP3.34 was detected in 11 isolates (10.47%). Other genes detected included; lasR (17.1%), lasB (18%) and lasA (26.6%). There was a significant relationship between virulence factors and the OX and IMP genes (p ≤ 0.05). CONCLUSION: The relationship between antibiotic resistance and virulence factors observed in this study could play an important role in outbreaks associated with P. aeruginosa infections.

[Isolation of Citrobacter spp. from blood specimens in patients hospitalized in Kermanshah Imam Khomeini hospital and determination of the of isolates sensitivity to antibiotics: short communication]

Background and Aim: Citrobacter is a gram-negative, nonsporeforming, facultative anaerobic and motile bacillus within the family of Enterobacteriaceae and is ubiquitous in nature. This opportunistic pathogen causes a wide spectrum of infections. The aim of the present study was to examine the isolation of Citrobacter spp. from blood specimens in patients hospitalized in Kermanshah Imam Khomeini hospital and to determine the isolates sensitivity to antibiotics

Materials and Methods: This cross- sectional study was carried out on 2285 blood specimens collected from hospitalized patients between March 2012 and February 2012. In the beginning, the blood samples were inoculated in blood culture tubes media. The Citrobacter spp. isolates were identified and their identification was confirmed by means of morphological and biochemical laboratory tests. Drug sensitivity test was carried out according to CLSI [2011] recommendations through using the standard disc diffusion method

Results: In this study Citrobacter spp. were isolated from 21 [15.8%] of 133 culture positive blood specimens collected from the hospitalized patients. The most effective antimicrobial agents against Citrobacter isolates were imipenem [90.4%], and amikacin [71.5%], respectively. The most frequent resistance observed was to cephalothin [76.2%], ciprofloxacin [76.2%], ceftazidime [66.6%] and co-trimoxazole [62%]

Conclusion: Citrobacter isolates showed high resistance to betalactam antibiotics. Therefore, it is necessary that these drugs should only be administered to patients whose diagnostic isolates reveal sensitivity in vitro