Prevalence and epidemiological investigation of mgrB-dependent colistin resistance in extensively drug resistant Klebsiella pneumoniae in Iran.

Carbapenemases-producing K. pneumoniae are challenging antimicrobial therapy of hospitalised patients, which is further complicated by colistin resistance. The aim of this study was to investigate the molecular epidemiological insights into carbapenemases-producing and colistin-resistant clinical K. pneumoniaeA total of 162 colistin resistant clinical strains of K. pneumoniae were collected during 2017-2019. Antimicrobial susceptibility and the colistin minimum inhibitory concentration were determined. Using PCR assay, the prevalence of resistance-associated genes including blaKPC, blaIMP, blaVIM, blaOXA-48, blaNDM-1 and mcr-1 to -9 was examined. Additionally, a PCR assay was used to examine the mgrB gene in colistin-resistant bacteria. 94.4% of the tested strains were resistant to imipenem and 96.3% were resistant to meropenem. Colistin resistance (MIC > 4 µg/L) was observed in 161 isolates (99.4%) by Colistin Broth Disk Elution method. The KPC enzyme was the most common carbapenemase and was identified in 95 strains (58.6%), followed by the IMP, VIM and OXA-48 detected in 47 (29%), 23 (14.2%) and 12 (7.4%) isolates, respectively. However, no NDM-1 gene was detected. Additionally, none of the studied isolates harbored mcr variants, while mgrB gene was observed in 152 (92.6%) isolates. Colistin resistance of K. pneumoniae isolates may be associated with mgrB gene mutation. To stop the spread of resistant K. pneumoniae, surveillance must be improved, infection prevention protocols must be followed, and antibiotic stewardship must be practised.

Antimicrobial susceptibility of bacteria isolated from cerebrospinal fluids in an Iranian referral pediatric center, 1998-2008.

Antimicrobial susceptibility patterns of bacterial meningitis provide essential information regarding selection of antibiotic therapy for patients with bacterial meningitis. This study presents data on causes of bacterial meningitis and their susceptibility pattern among children at Children's Medical Center (CMC), a referral tertiary care center in Iran. In this comprehensive retrospective study we reviewed microbiology records of all inpatients suspected to bacterial meningitis, during 1998-2008 of period. Of 11269 CSF cultures examined in the study, 329 (2.9%) were positive for bacterial growth. Overall, coagulase negative staphylococci (CONS) were the most frequent group of organism recovered from our CSF cultures (40%), followed by gram negative enteric bacilli (19.7%). Also, high rates of oxacillin and vancomycin resistance were found among staphylococci. In our study more than 80% of gram-negative enteric bacteria were resistant to ampicillin; we also found high rates of cephalosporin resistance among these organisms. Over 55% of S. pneumoniae were resistant to penicillin. Staphylococci species and gram-negative enteric organisms were the most common pathogens isolated from CSF cultures in this study. It seems that nosocomial meningitis is the main cause of bacterial meningitis in CMC Hospital. Our report draws attention to the importance devising a national strategy to control the spread of resistance in Iran.

Five-year evaluation of the antimicrobial susceptibility patterns of bacteria causing bloodstream infections in Iran.

INTRODUCTION: Bloodstream infections (BSI) are a serious cause of morbidity and mortality worldwide. Emerging antimicrobial drug resistance among bacterial pathogens causing BSI can limit therapeutic options and complicate patient management. METHODOLOGY: To encourage the prudent use of appropriate antibiotics in our pediatric population at Children's Medical Center Hospital, Tehran, Iran, we studied the frequency and antibiogram patterns of blood culture isolates from January 2001 to December 2005. RESULTS: Of 25,223 blood cultures examined, 2,581 (10.23 %) were positive for bacterial growth. The frequency of Gram-positive bacteria isolated was 47.6% (1228 of 2581) and that for Gram-negatives was 52.4% (1353 of 2581). The rates of methicillin (oxacillin) resistance in Staphylococcus aureus and coagulase-negative staphylococci (CoNS) were 79% and 89%, respectively. About 45% of Streptococcus pneumoniae were resistant to trimethoprim-sulfamethoxazole and approximately 66% to penicillin. Among the Gram-negative isolates, Pseudomonas aeruginosa was most frequently isolated, representing 943 (36.7%) over five years. This possibly represents an unrecognized hospital outbreak or contamination of blood culture bottles or other products such as skin disinfectants. Additionally, this pathogen showed extremely high rates of antimicrobial resistance. There were notable differences in frequency of the five most common microorganisms isolated from blood cultures, which can help set priorities for focused infection control efforts. CONCLUSIONS: Our findings underscore the need to monitor blood culture isolates and their antimicrobial resistance patterns to observe resistance trends that would influence appropriate empiric treatment and infection control strategies for bacteremic children.