Incidence of constitutive and inducible clindamycin resistance among hospital-associated Staphylococcus aureus.

Clindamycin is one of the important alternative antibiotics in the therapy of Staphylococcus aureus infections. Clinical failure of clindamycin therapy has been reported due to multiple mechanisms that confer resistance to macrolides, lincosamides and Streptogramin B (MLSB) antibiotics. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes, resulting in the treatment failure. Although data from the developed countries have shown to be enormity of the problem, data from the developing countries are lacking. The aim of the study was to distinguish different resistance phenotypes in erythromycin-resistant S. aureus by a simple double-disc diffusion test (D test). A total of 153 S. aureus isolates were subjected to routine antibiotic susceptibility testing, including cefoxitin disc (30 µg) and by oxacillin screen agar. Inducible clindamycin resistance was tested by 'D test' as per CLSI guidelines. Odds ratios (OR) and 95 % confidence intervals (95 % CI) were calculated. P values were calculated using SPSS (version 18). Among 153 S. aureus isolates, 42 (27.45 %) were resistant to methicillin, whereas 111 (72.54 %) were methicillin susceptible. Out of the 63 (41.17 %) erythromycin-resistant S. aureus isolates, 14 (9.15 %) showed inducible resistance [P = 0.0002, odds ratio (OR) 18.30; 95 % confidence interval (CI) 8.72-25.77), 20 (13.07 %)] showed constitutive resistance (P = 0.002, OR 14.38, 95 % CI 5.33-21.49), while the remaining 29 (18.95 %) showed inducible phenotype. Inducible and constitutive resistance was found to be higher in MSSA when compared with MRSA. Clinical laboratories should perform D test routinely to guide the clinicians about the inducible clindamycin resistance and to prevent misuse of antibiotics.

Copper, Zinc-Superoxide Dismutase from Clinically Isolated Escherichia coli: Cloning, Analysis of sodC and Its Possible Role in Pathogenicity.

Superoxide dismutase has been discovered within the periplasm of several Gram-negative pathogens. We studied the Cu,Zn-SOD enzyme in Escherichia coli isolated from clinical samples (stool samples) collected from patients suffering from diarrhea. Antibiogram studies of the isolates were carried out to determine the sensitive and resistant strains. The metal co-factor present in the enzyme was confirmed by running samples in native gels and inhibiting with 2 mM potassium cyanide. A 519 bp sodC gene was amplified from resistant and sensitive strains of Escherichia coli. Cloning and sequencing of the sodC gene indicated variation in the protein and amino acid sequences of sensitive and resistant isolates. The presence of sodC in highly resistant Escherichia coli isolates from diarrheal patients indicates that sodC may play role in enhancing the pathogenicity by protecting cells from exogenous sources of superoxide, such as the oxidative burst of phagocytes. The presence of SodC could be one of the factors for bacterial virulence.

Degradation of h-acid by free and immobilized cells of Alcaligenes latus

Alcaligenes latus, isolated from industrial effluent, was able to grow in mineral salts medium with 50 ppm (0.15 mM) of H-acid as a sole source of carbon. Immobilization of Alcaligenes latus in Ca-alginate and polyurethane foam resulted in cells embedded in the matrices. When free cells and immobilized cells were used for biodegradation studies at concentration ranging from 100 ppm (0.3 mM) to 500 ppm (1.15 mM) degradation rate was enhanced with immobilized cells. Cells immobilized in polyurethane foam showed 100 percent degradation up to 350 ppm (1.05 mM) and 57 percent degradation at 500 ppm (1.5 mM). Degradation rate of Ca-alginate immobilized cells was less as compared to that of polyurethane foam immobilized cells. With Ca-alginate immobilized cells 100 percent degradation was recorded up to 200 ppm (0.6 mM) of H-acid and only 33 percent degradation was recorded at 500 ppm (1.5 mM) of H-acid. Spectral analysis of the products after H-acid utilization showed that the spent medium did not contain any aromatic compounds indicating H-acid degradation by A. latus.

Detection, amplification & sequence homology of sodC in clinical isolates of Salmonella sp.

BACKGROUND & OBJECTIVES: Periplasmic copper and zinc superoxide dismutase (Cu,Zn-SOD or SodC) is an important component of the antioxidant shield which protects bacteria from the phagocytic oxidative burst. Cu,Zn-SODs protect Gram-negative bacteria against oxygen damage which have also been shown to contribute to the pathogenicity of these bacterial species. We report the presence of SodC in drug resistant Salmonella sp. isolated from patients suffering from enteric fever. Further sodC was amplified, cloned into Escherichia coli and the nucleotide sequence and amino acid sequence homology were compared with the standard strain salmonella Typhimurium 14028. METHODS: Salmonella enterica serovar Typhi (S. Typhi) and Salmonella enterica serovar Paratyphi (S. Paratyphi) were isolated and identified from blood samples of the patients. The isolates were screened for the presence of Cu, Zn-SOD by PAGE using KCN as inhibitor of Cu,Zn-SOD. The gene (sodC) was amplified by PCR, cloned and sequenced. The nucleotide and amino acid sequences of sodC were compared using CLUSTAL X. RESULTS: SodC was detected in 35 per cent of the Salmonella isolates. Amplification of the genomic DNA of S. Typhi and S. Paratyphi with sodC specific primers resulted in 519 and 515 bp amplicons respectively. Single mutational difference at position 489 was observed between the sodC of S. Typhi and S. Paratyphi while they differed at 6 positions with the sodC of S. Typhimurium 14028. The SodC amino acid sequences of the two isolates were homologous but 3 amino acid difference was observed with that of standard strain S. Typhimurium 14028. INTERPRETATION & CONCLUSIONS: The presence of SodC in pathogenic bacteria could be a novel candidate as phylogenetic marker.

Degradation of h-acid by free and immobilized cells of Alcaligenes latus.

Alcaligenes latus, isolated from industrial effluent, was able to grow in mineral salts medium with 50 ppm (0.15 mM) of H-acid as a sole source of carbon. Immobilization of Alcaligenes latus in Ca-alginate and polyurethane foam resulted in cells embedded in the matrices. When free cells and immobilized cells were used for biodegradation studies at concentration ranging from 100 ppm (0.3 mM) to 500 ppm (1.15 mM) degradation rate was enhanced with immobilized cells. Cells immobilized in polyurethane foam showed 100% degradation up to 350 ppm (1.05 mM) and 57% degradation at 500 ppm (1.5 mM). Degradation rate of Ca-alginate immobilized cells was less as compared to that of polyurethane foam immobilized cells. With Ca-alginate immobilized cells 100% degradation was recorded up to 200 ppm (0.6 mM) of H-acid and only 33% degradation was recorded at 500 ppm (1.5 mM) of H-acid. Spectral analysis of the products after H-acid utilization showed that the spent medium did not contain any aromatic compounds indicating H-acid degradation by A. latus.