Belgode Narasimha Harish

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.

Antimicrobial resistance in typhoidal salmonellae

Infections with Salmonella are an important public health problem worldwide. On a global scale, it has been appraised that Salmonella is responsible for an estimated 3 billion human infections each year. The World Health Organization (WHO) has estimated that annually typhoid fever accounts for 21.7 million illnesses (217,000 deaths) and paratyphoid fever accounts for 5.4 million of these cases. Infants, children, and adolescents in south-central and South-eastern Asia experience the greatest burden of illness. In cases of enteric fever, including infections with S. Typhi and S. Paratyphi A and B, it is often necessary to commence treatment before the results of laboratory sensitivity tests are available. Hence, it is important to be aware of options and possible problems before beginning treatment. Ciprofloxacin has become the first-line drug of choice since the widespread emergence and spread of strains resistant to chloramphenicol, ampicillin, and trimethoprim. There is increase in the occurrence of strains resistant to ciprofloxacin. Reports of typhoidal salmonellae with increasing minimum inhibitory concentration (MIC) and resistance to newer quinolones raise the fear of potential treatment failures and necessitate the need for new, alternative antimicrobials. Extended-spectrum cephalosporins and azithromycin are the options available for the treatment of enteric fever. The emergence of broad spectrum β-lactamases in typhoidal salmonellae constitutes a new challenge. Already there are rare reports of azithromycin resistance in typhoidal salmonellae leading to treatment failure. This review is based on published research from our centre and literature from elsewhere in the world. This brief review tries to summarize the history and recent trends in antimicrobial resistance in typhoidal salmonellae.

EMERGENCE OF VANCOMYCIN INTERMEDIATE STAPHYLOCOCCUS SPECIES IN SOUTHERN INDIA

Since the emergence of meticillin-resistant Staphylococcus aureus (MRSA), vancomycin has been the only uniformly effective treatment for staphylococcal infections in India, teicoplanin and linezolid not being commonly used. The incidence of vancomycin-intermediate S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA) has been increasing in various parts of the world. The first clinical isolate of VRSA was reported from the United States in 2002 (CDC, 2002). More recently, some workers have reported vancomycin-resistant staphylococcal strains from Brazil (Palazzo et al., 2005), Jordan (Bataineh, 2006) and India (Tiwari & Sen, 2006). Vancomycin intermediateresistant Staphylococcus haemolyticus has been reported previously (Schwalbe et al., 1987), and perhaps this is a critical antecedent of VISA. As documented reports of VISA/VRSA in India are very few (Assadullah et al., 2003), we decided to monitor the vancomycin susceptibility of clinical meticillin-resistant Staphylococcus spp. in the tertiary care teaching hospital, JIPMER.

Molecular description of plasmid-mediated AmpC β-lactamases among nosocomial isolates of Escherichia coli & Klebsiella pneumoniae from six different hospitals in India

Background & objectives: Plasmid mediated AmpC β-lactamase (PMABL) resistance in Escherichia coli and Klebsiella spp. is an emerging problem worldwide. Phenotypic methods are commonly used for detection of PMABL production in Gram-negative isolates, but molecular data about the prevalence of plasmid-mediated AmpC-type resistance at the national level are needed. Hence, a prospective study was undertaken to determine the occurrence of PMABL gene and its types among clinical isolates of E. coli and K. pneumoniae obtained from six different hospitals in India. Methods: A total of 241 nosocomial isolates of K. pneumoniae (n=109) and E.coli (n=132) from six geographically distant hospitals in India were included. These were screened for cefoxitin resistance. AmpC disk test and modified three dimensional extraction test were used for phenotypic detection of PMABL production. Molecular types were determined by a multiplex PCR. Results: Among the 241 isolates, 187 (77.5%) were found to be cefoxitin resistant (K. pneumoniae n=83, E. coli n=104). AmpC activity was detectable in 153 (63.4%) isolates, (K. pneumoniae n=69, E. coli n=84). By PCR, the plasmid encoded AmpC genes were found in 92 (38.1%) isolates and the molecular types of the genes detected predominantly were DHA, CIT followed by MOX and ACC types. Interpretation & conclusions: A high percentage of plasmid-encoded AmpC enzymes was noted in E. coli and K. pneumonia isolates obtained from different parts of the country. Phenotypic methods alone may not reflect the true number of PMABL producers. Genotypic methods need to be employed in national surveillance studies.

Maternal genital bacteria and surface colonization in early neonatal sepsis

Objective: The study was intended to evaluate the role of maternal genital bacteria and babys surface colonization in early onset neonatal sepsis.Methods: Babies (born in the hospital of Jawaharlal Institute of Postgraduate Medical Education and Research) who developed clinical signs of sepsis were studied. Swabs were collected for culture from babys umbilicus, ear, throat in addition to gastric aspirate and blood culture. The genital tract of the mother was also studied for bacterial colonization. The organisms isolated from the maternal genital tract and babys surface colonization were correlated with those isolated from blood culture by calculating Phi correlation coefficient.Results:Esch coli was the most common organism isolated from maternal genital tract and surface cultures of babies, but Klebseilla-Spp was the most common organism isolated from blood. There was a significant correlation between surface colonization of babies and matermal genital bacteria, so also was babys surface culture and blood culture. However, correlation between maternal genital bacteria and babys blood culture was not significant.Conclusion: Surface colonizing bacteria and not maternal genital bacteria are important in early onset neonatal sepsis.

Molecular Analysis of Fluoroquinolone-resistant Salmonella Paratyphi A Isolate, India

Salmonella enterica serovar Paratyphi A is increasingly a cause of enteric fever. Sequence analysis of an Indian isolate showed a unique strain with high-level resistance to ciprofloxacin associated with double mutations in the DNA gyrase subunit gyrA (Ser83→Phe and Asp87→Gly) and a mutation in topoisomerase IV subunit parC (Ser80→Arg).

Typhoid and paratyphoid fever

Typhoid and paratyphoid fever are diseases of the intestinal tract caused by the Salmonella Typhi and Salmonella Paratyphi bacteria. Typhoid is rare in developed countries where environmental hygiene is poor, as in many developing countries, typhoid is a major public health problem. The greatest risk exists to travellers visiting countries where the disease is common. In Queensland, several cases of paratyphoid fever are notified each year, most occurring in returned overseas travellers.

Cryptococcal meningoencephalitis diagnosed by blood culture

Increase in cryptococcal infection has been noticed after acquired immunodeficiency syndrome pandemic. Cryptococcus neoformans can be isolated from blood in the process of dissemination to brain. We report a case of cryptococcal fungaemia in a patient whose cerebrospinal fluid was negative for Cryptococcus neoformans. Retrospective analysis revealed human immunodeficiency virus seropositivity of the patient. He was treated with amphotericin B and fluconazole. Antiretroviral therapy was started, however, the patient succumbed to the infection.

Comparison of an in-house latex agglutination test with IgM ELISA and MAT in the diagnosis of leptospirosis

The laboratory diagnosis of leptospirosis is fraught with several problems. Isolation of Leptospira by culture has a low sensitivity and the microscopic agglutination test (MAT) is time consuming To overcome these problems, a rapid latex agglutination test (LAT) has been standardized for the detection of antileptospiral antibodies in serum samples from suspected cases of leptospirosis. We compared the efficiency of the LAT to a commercially available IgM ELISA and MAT. A total of 150 serum samples were tested by LAT, IgM ELISA, and MAT. The positivity was 26.7%, 26% and 24% respectively. The sensitivity and specificity of LAT as compared to MAT was 90.62 and 91.96% respectively. Even though LAT and ELISA showed similar results, its rapidity and simplicity made latex agglutination test more suitable as a rapid screening test.

Factors predicting occult bacteremia in young children

A febrile child without a definite localizing sign of infection may be in initial phase of bacteremia which unless treated would result in systemic complication. These instances are referred to as “Occult bacteremia”. The common pathogens isolated in these children areStreptococcus pneumoniae, Hemophilus influenzae andNeisseria meningitidis. A hundred consecutive children in the age group of 3–36 months attending pediatric outpatient department and casualty were clinically evaluated using AIOS (acute illness observation scale) score and were subjected to complete blood counts, smear for malarial parasites, ESR and blood culture. In the 19-month study period, 4 instances of occult bacteremia were identified.Streptococcus pneumoniae was cultured in 3 cases andH. influenzae in one. A febrile and toxic child in the age group of 3–36 months has a high risk of occult bacteremia. High fever of temperature ≥ 102°F, ESR ≥ 15 mm/hour, and total leukocyte count ≥ 15,000 / mm3, in a child with AIOS score of ≥ 10 may be considered for more detailed investigations and early intervention with antimicrobial therapy.