Mushtaq A. Khan

Antimicrobial resistance trends in blood culture positive Salmonella Typhi isolates from Pondicherry, India, 2005–2009

Typhoid fever is caused by Salmonella enterica serovar Typhi, a major public health concern in developing countries. Recently, there has been an upsurge in the occurrence of bacterial isolates that are resistant to ciprofloxacin, and the emergence of broad spectrum β-lactamases in typhoidal salmonellae constitutes a new challenge for the clinician. A total of 337 blood culture isolates of S. Typhi, isolated from Pondicherry, India, between January 2005 and December 2009, were investigated using phenotypic, molecular and serological methods. Of the 337 isolates, 74 (22%) were found to be multidrug resistant (MDR) and 264 (78%) nalidixic acid resistant (NAR). Isolates with reduced susceptibility to ciprofloxacin possessed single mutations in the gyrA gene. A high rate of resistance (8%) was found to ciprofloxacin. All isolates with a ciprofloxacin MIC ≥ 4 mg/L possessed both double mutations in the QRDR of the gyrA gene and a single mutation in the parC gene. Active efflux pump mechanisms were also found to be involved in ciprofloxacin resistance. Finally, a large number of PFGE patterns (non-clonal genotypes) were observed among the S. Typhi isolates. In conclusion, a high rate of ciprofloxacin resistance was observed in comparison to other endemic areas in blood culture isolates of S. Typhi from Pondicherry, India, with steadily increasing NAR but decreasing MDR isolations over the study period. This is most likely to be due to an increased use of ciprofloxacin as a first-line drug of choice over more traditional antimicrobial agents for the treatment of typhoid fever.

Analysis of VanA vancomycin-resistant Enterococcus faecium isolates from Saudi Arabian hospitals reveals the presence of clonal cluster 17 and two new Tn1546 lineage types

OBJECTIVES The aim of this study was to characterize 34 vancomycin-resistant VanA Enterococcus faecium isolates obtained from two hospitals in Saudi Arabia and to assess Tn1546 variation within these isolates. METHODS PFGE and multilocus sequence typing (MLST) genotypes, antibiotic susceptibility patterns, the presence of enterococcal surface protein (esp) and hyaluronidase (hyl) genes and conjugation frequencies were determined. In addition, Tn1546 elements were characterized. RESULTS PFGE and MLST analysis revealed the presence of 31 and 6 different genotypes, respectively. Further, three new ST types were discovered. Ninety-seven percent (33/34) of the isolates were associated with clonal complex 17 (CC17), with all isolates but one being resistant to ampicillin and all isolates being susceptible to linezolid. The esp and hyl genes were found in 44% (15/34) and 53% (18/34) of the isolates, respectively. Tn1546 analysis revealed that the isolates belonged to five different groups, including two new lineages. The IS-element insertions described did not abolish the transfer of VanA resistance. CONCLUSIONS VanA vancomycin-resistant E. faecium isolates obtained from Saudi Arabian hospitals include CC17 MLST types, a clonal cluster associated with E. faecium nosocomial infection worldwide. Novel E. faecium MLST types are circulating in Saudi Arabia, as well as novel Tn1546 types. It seems likely that CC17 E. faecium isolates may be distributed throughout the Middle East as well as Europe, America, Africa and Australia.

bro β-lactamase and antibiotic resistances in a global cross-sectional study of Moraxella catarrhalis from children and adults

OBJECTIVES To compare and contrast the geographic and demographic distribution of bro beta-lactamase and antibiotic MIC(50/90) for 1440 global Moraxella catarrhalis isolates obtained from children and adults between 2001 and 2002. METHODS One thousand four hundred and forty M. catarrhalis isolates originating from seven world regions were investigated. The isolates were recovered from 411 children <5 years of age and 1029 adults >20 years of age. PCR-restriction fragment length polymorphism (RFLP) was performed to determine bro prevalence and to distinguish between bro types. MIC values of 12 different antibiotics were determined using the CLSI (formerly NCCLS) broth microdilution method. RESULTS Of the 1440 isolates, 1313 (91%) possessed the bro-1 gene and 64 (4%) possessed the bro-2 gene. Additionally, the prevalence of bro positivity between the child and adult age groups was significantly different (P < 0.0001), though bro-1 and bro-2 prevalences within age groups were not significantly different. Consistently higher beta-lactam MICs were observed for M. catarrhalis isolates originating in the Far East. Significant correlations in MICs were observed for several antibiotic combinations, including all five beta-lactams with each other, and among the two quinolones. CONCLUSIONS The worldwide prevalence of bro gene carriage in clinical isolates of M. catarrhalis is now approaching 95%, with children significantly more likely to harbour bro-positive isolates than adults. Further, statistically significant differences in the distribution of beta-lactam MICs were observed between different world regions, particularly with respect to the Far East.

High prevalence of ST-78 infection-associated vancomycin-resistant Enterococcus faecium from hospitals in Asunción, Paraguay

Forty infection-associated VanA-type vancomycin-resistant Enterococcus faecium (VRE) strains obtained from five collaborating hospitals in Asunción, Paraguay were investigated. Genotyping using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing revealed the presence of 17 cluster types and four STs, with 93% (37/40) of isolates comprising ST type 78. Other ST types included ST-132, ST-210 and one new ST type (ST-438). All but one isolate (ST-438) were associated with clonal complex 17 (CC17), and 97% of the total isolates carried the esp gene. Three Tn1546 variants were found, including a new lineage containing an ISEfa5 insertion in an existing IS1251 element.

New type F lineage-related Tn1546 and a vanA/vanB type vancomycin-resistant Enterococcus faecium isolated from patients in Dammam, Saudi Arabia during 2006-2007.

Knowledge regarding vancomycin-resistant enterococci (VRE) from Middle Eastern countries is scarce. We therefore investigated the antimicrobial resistance profiles and genetic relationships of VRE Enterococcus faecium isolates obtained from patients attending the King Fahad Specialist Hospital, Dammam, during 2006-2007. The predominant VRE comprised 20 vanB, five vanA and one vanA/vanB type isolates, which tended to fall into two genetic clusters that were identifiable phenotypically by their susceptibility to tetracycline. Multi-locus sequence typing of a random selection of isolates showed that they were part of clonal cluster 17, showing the importance of this genotype in nosocomial VRE infections in Saudi Arabia. Further analysis showed that four of the vanA genotype isolates possessed a new type F Tn1546 transposon, associated with IS1216V and IS1251. Finally, E. faecium vanA/B isolates are rarely reported in the clinical setting including in Saudi Arabia.

Antimicrobial resistance trends in blood culture positive Salmonella Paratyphi A isolates from Pondicherry, India.

Enteric fever is a public health problem with the upsurge in the occurrence of Salmonella isolates that are resistant to ciprofloxacin. In this study, a total of 284 blood culture isolates of S. Paratyphi A were investigated. Of these isolates, 281 (98.9%) were nalidixic acid resistant. A high rate (6.3%) of high-level resistance (≥4 μg/mL) was found to ciprofloxacin. The isolates with ciprofloxacin minimum inhibitory concentrations (MICs) of ≥12 μg/mL had 4 mutations, 2 mutations within the quinolone resistance-determining region of gyrA and 2 mutations also in parC. According to the Clinical Laboratory Standards Institute 2012 MIC breakpoints, 75.0% of isolates were resistant to ciprofloxacin. Finally, 3 major pulsed-field gel electrophoresis patterns were observed among the S. Paratyphi A isolates. The spread of fluoroquinolone resistant S. Paratyphi A necessitates a change toward ′evidence-based′ treatment for enteric fever. The research provides a perspective on the increasing prevalence of antimicrobial resistant S. Paratyphi A isolates in this region of India.

Rise of Clostridium difficile infections: an overview

&NA; Clostridium difficile is a Gram-positive, rod-shaped, motile, spore forming, obligate anaerobe, which is part of the gastrointestinal flora of man and animals. Some strains of C. difficile produce toxins and are capable of causing mild-to-severe diarrhea and pseudomembranous colitis. Further, C. difficile has been found to be a common cause of nosocomial antibiotic-associated diarrhea and is the most frequent cause of infectious diarrhea in hospitals and long-term care facilities globally. It is the only nosocomially significant anaerobic bacterium that forms spores (which are hard to destroy), though C. difficile may also be present as a colonizing inhabitant of the normal gut microbiota of some individuals and yet produce no visible signs of disease. Most cases of C. difficile infection occur in patients who are prescribed high-dose antibiotics or prescribed antibiotics for a prolonged period of time. These antibiotics can disturb the normal balance of the gut microbiota, altering its composition and allowing the overgrowth of C. difficile bacteria. When this occurs, the C. difficile bacteria produce toxins, which can damage gut tissues and cause diarrhea. This mini review discusses the epidemiology, history, role of antibiotics and virulence factors associated with C. difficile infections.