Mohammad-Hossein MALEKI, Farid Azizi JALILIAN, Hatef KHAYAT, Maryam MOHAMMADI, Fazel POURAHMAD, Khairollah ASADOLLAHI, Iraj PAKZAD, Nourkhoda SADEGHIFARD, Setareh SOROUSH, Mohammad EMANEINI and Morovat TAHERIKALANI

ABSTRACT

The emergence of fluoroquinolone resistance among A. baumannii isolates is now of particular concern. Phenotypic and genotypic characteristics of resistance to ciprofloxacin among 50 Acinetobacter baumannii isolated from burn wound infections of Tehran were evaluated by E-test and broth microdilution in presence and absence of efflux pump inhibitor phenylalanine- arginine β-naphthylamide (PAβN) and PCR-sequencing methods. All isolates were then typed by REP-PCR fingerprinting to find the clonal relationship between resistant isolates. Our results indicated that resistance to ciprofloxacin among A. baumannii isolated from burn infections in Tehran are high with resistance rate of 100% and ciprofloxacin resistant isolates have a mutation of Serine 83 →Leucine in the quinolone resistance determining region (QRDR) of DNA gyrase subunit A (GyrA). 38% of the isolates showed MIC ranges of 64 to ≥512μg/ml and were considered as highly resistant. We could not detect Par C mutations and plasmid-mediated quinolone resistance A (qnrA) among ciprofloxacin resistant isolates. When we used the efflux pump inhibitor PAβN, MIC of ciprofloxacin was reduced two-to four folds. REP-type A (25/50; 50%), B (20/50; 30%) and C (10/50; 20%) were the most common REP-types among A. baumannii isolates. It seems that mutation in GyrA is the main mechanism of resistant to ciprofloxacin among A. baumannii isolates from burn infections and presence of efflux pumps is just secondary target for ciprofloxacin resistant among A. baumannii in Iran. Regarding with limitation of REP-types detected in this study, we found good correlation between resistance to ciprofloxacin and REP-types A-C.

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Mohammad EMANEINI, Akbar MIRSALEHIAN, Reza BEIGVIERDI, Abbas Ali Imani FOOLADI, Fatemeh ASADI, Fereshteh JABALAMELI and Morovat TAHERIKALANI

ABSTRACT

Background: Streptococcus agalactiae or Group B Streptococci (GBS) is an important bacterial pathogen that causes a wide range of infections including neonatal sepsis, meningitis, pneumonia and soft tissue or urinary tract infections.

Material and methods: One hundred and fifteen isolates of Streptococcus agalactiae collected from urine specimens of patients attending a hospital in Tehran. All isolates were screened for their capsular types and genes encoding resistance to the macrolide and tetracycline antibiotics by PCR and multiplex PCR–based methods.

Results: Most of isolates belonged to capsular types III (49%), V (19%), II (16%), and Ib (6%). Twelve isolates (10%) were nontypable. All isolates were susceptible to penicillin and Quinupristindalfopristin, but were resistant to clindamycin (35%), chloramphenicol (45%), erythromycin (35%), linezolid (1%) and tetracycline (96%). The most prevalent antimicrobial resistance gene was tetM found in 93% of the isolates followed by ermTR, ermB, and tetK, found in 23%, 16%, and 16% of isolates, respectively. The genes, tetL, tetO, ermA, ermC and mefA were not detected in any of the S. agalactiae isolates. Of the 110 tetracycline resistant S. agalactiae, 89 isolates harbored the tetM gene alone and eighteen isolates carried the tetM gene with the tetK gene. All erythromycin-resistant isolates exhibited cMLSB resistance phenotype, 22 isolates harbored the ermTR gene alone and five isolates carried the ermTR gene with the ermB gene. The rate of coexistence of genes encoding the erythromycin and tetracycline resistance determinants was 34%.

Conclusion: The present study demonstrated that S. agalactiae isolates obtained from urine samples showed a high rate of resistance to tetracycline, chloramphenicol and macrolide antibiotics and were commonly associated with the resistance genes temM, ermTR or ermB.

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