Management of lower respiratory tract infections (LRTI's): clinical microbiologists' perspective.

In the era of emergence and re-emergence of newer and existing microorganisms, clinical and laboratory diagnosis of LRTI’s requires regular evaluation. Elaborating on possible predisposing factors will be critical to health care workers in the better management of patients suffering with Lower Respiratory Tract Infections (LRTI’s). Microbiologist’s role becomes crucial in deciding the culture methods to be employed to isolate the suspected causative microorganism and identification of the probable pathogen among mixed growth of the isolated bacteria/fungi. Antimicrobial therapy should necessarily be guided by the susceptibility patterns of various antibiotics against different microorganisms from a given geographical region, which should be regularly updated.

Seroprevalence of Blood-borne Viral Infections in Post HAART Era at a Tertiary Care Hospital in South India: A Five Year Trend Analysis (2008- 2012) and a Comprehensive Review.

Aim: Human Immunodeficiency Virus (HIV), Hepatitis B (HBV) and Hepatitis C (HCV) viruses are the major causes of chronic viral infections globally and their prevalence has been extensively reported in the literature in various study groups including general population, health care workers, sex workers, homosexuals, pregnant woman. There are only fewer reports of Seroprevalence in tertiary care centers. We aim to study the trends of such infections in a tertiary care teaching hospital located at South India. Study Design: This is a prospective study conducted over a 5 year period (2008-2012). Place and Duration of Study: Department of Microbiology, Prathima Institute of Medical Sciences, Karimnagar, Andhrapradesh, India from 2008-2012. Methodology: We performed a prospective study of patients presenting at the Prathima institute of medical Sciences, a rural tertiary care teaching hospital over a period of 5- years (Jan 2008 to Dec 2012). Screening for anti-HIV I and 2, HBsAg detection and anti- HCV antibodies test were carried out by commercially available enzyme linked immunosorbent assay (ELISA). Results: Of the 16796 individuals tested a total of 570 (3.3%) showed seropositivity to one of the three viral infections tested. Among the population tested 258(1.5%) were seropositive for antibodies against HIV-1, and none showed HIV-2 seroprevalence (0%). Prevalence of Hepatitis B and Hepatitis C were found as 305(1.8%) and 7(0.04%) respectively. Co-infection of HIV-1 with Hepatitis B was observed only in 10(0.06%) cases. Conclusion: The present study revealed that there was a slight increasing trend for Seroprevalence of HIV- 1 antibodies among the tested population. Hepatitis B surface antigen Seroprevalence has shown a gradual increase during the last five years. Seroprevalence rates of Hepatitis C viral infection also showed an increasing trend through a five year period.

Staphylococcus aureus colonization of anterior nares of school going children.

Objective. To determine the colonization rates of S. aureus in anterior nares of school going children, evaluate the antimicrobial resistance of such isolates against various antibiotics. Methods. Nasal swabs taken for S.aureus in 392 healthy school going children aged between 5 and 15 yr belonging to three schools surrounding Kamineni Institute of Medical Sciences, Narketpally, Andhra Pradesh, India. Swabs were inoculated in to Mannitol Salt Agar (MSA) and incubated at 37o C for 24hr, Staphylococcus aureus isolates were identified by standard microbiological methods such as Gram’s stain, catalase and coagulase. MICs were determined by Agar dilution technique against Vancomycin, Ciprofloxacin, Sparfloxacin, Sparfloxacin ß Cyclodextrin. Antimicrobial resistance patterns of all the isolates against Oxacillin (1 μg) Penicillin (10units), Ampicillin (10μg), Co-trimoxazole (23.75 μg), Erythromycin (15 μg), Tetracycline (30 μg) and Gentamicin (10 μg) were tested using Kirby-Bauer disk diffusion method in accordance with CLSI standards. Results. Of the 392 samples screened 63(16%) showed the growth of Staphylococcus aureus. Twelve (19%) isolates were found to be MRSA. Antimicrobial susceptibility testing using Agar dilution method against Vancomycin, ciprofloxacin , Sparfloxacin, and Sparfloxacin β Cyclodextrin revealed MICs in the range of 0.52 μg/ml, 0.51 μg/ml, 0.5 μg/ml and <0.0312- 0.250 μg/ml respectively. Disk diffusion method showed that all the isolates were resistant to Penicillin and Ampicillin. A resistance of 14.3%, 25% and 22.2% was observed against Co-trimoxazole, Erythromycin and Tetracycline respectively. Gentamiicin was the only antibiotic against which most of the isolates were sensitive. Conclusion. Our results suggest that healthy school going children under 16 yr of age are potential carriers of S. aureus and in particular MRSA and multi-drug resistant strains.

Purification of catalytically active hepatic NADPH cytochrome P450 oxidoreductase from the rhesus monkey, Macaca mulatta.

Hepatic NADPH cytochrome P450 oxidoreductase capable of supporting polysubstrate monooxygenase (PSMO) reactions was purified from microsomes obtained from phenobarbitone (PB) pretreated rhesus monkey. Two preparations of the enzyme purified by affinity and molecular exclusion chromatographic techniques demonstrated specific content of 19.5 and 37.9 nmol cytochrome c reduced/min/mg protein and subunit molecular weight of 66 and 80 kDa, respectively. Both forms supported oxidation of NADPH and reduction of cytochrome c and DCIP but only 80 kDa preparation supported PSMO reactions. The reconstituted system consisted of hepatic P450, NADPH cytochrome P450 oxidoreductase, cytochrome b5 all purified from PB pretreated rhesus monkey and dilauroyl phosphatidylcholine or microsomal lipid. Eighty kDa preparation supported the metabolism of aminopyrine and tolbutamide by hepatic P4502C and erythromycin, ethylmorphine and nifedipine by hepatic P450 3A, respectively. The turnover of these substrates increased in the presence of partially purified cytochrome b5 from the rhesus monkey. To best of our knowledge this is the first report on the purification of monkey hepatic NADPH cytochrome P450 oxidoreductase capable of supporting in vitro PSMO by different isozymes of P450.

Gene regulation of cytochrome P450--an overview.

Xenobiotics have played a role in elucidating the regulation of gene expression of hepatic cytochrome P450 in the eukaryotes. The major regulation of P450 genes in the eukaryotes is at the transcriptional and post transcriptional level. Polycyclic aromatic hydrocarbons regulate the gene expression by binding the cytosolic aryl hydrocarbon receptor and its translocation to the nucleus where it forms a ternary complex with aryl hydrocarbon nuclear translocator. The ternary complex PAH-AHR-ARNT acts as a transcription factor and binds aromatic hydrocarbon responsive element to increase the expression of CYP1A1 gene. Phenobarbitone and ethanol regulate the expression of respective P450s within CYP2 gene family by different mechanisms but without the involvement of a cytosolic receptor. PB uses phosphorylation as a switch to increase the affinity of the transcription factor(s) for the positive rather than negative PB regulatory element within CYP2B1/2. This is one of the novel ways that nature has designed for a protein to act as a negative as well as a positive acting transcription factor. Ethanol regulates the expression of CYP2E1 by posttranslational stabilization making it resistant to the proteolytic digestion. Steroids regulate expression of CYP3A genes through a receptor mediated mechanism. The binary complex of the steroid and its receptor increases the transcription of CYP3 genes by binding glucocorticoid responsive element which is already occupied by another protein. Peroxisome proliferators also follow a receptor mediated mechanism in which a binary complex of PP activated receptor and retinoid X receptor acts a transcription factor and increases the expression of CYP4A genes by binding peroxisome proliferator responsive element. These studies demonstrate that PAH, glucocorticoids and PP follow a receptor mediated whereas PB and ethanol follow a nonreceptor mediated mechanism for the regulation of respective P450 genes in the eukaryotes.