Kegg Pathway: Streptomycin biosynthesis

Redox Rep. 2009; 14(4): 159-66
Luo S, Wehr NB

Protein carbonyl content is widely used as both a marker for oxidative stress and a measure of oxidative damage. Widely used methods for determination of protein carbonylation utilize the reaction of carbonyl groups with 2,4-dinitrophenylhydrazine (DNPH) to form protein-bound 2,4-dinitrophenylhydrazones. Hydrazones can be quantitated spectrophotometrically or, for greater sensitivity, detected immunochemically with anti-dinitrophenyl antibodies. Attention to methodology is important to avoid artifactual elevation in protein carbonyl measurements. We studied extracts of Escherichia coli to identify and eliminate such effects. Nucleic acid contamination caused serious artifactual increases in the protein carbonyl content determined by spectrophotometric techniques. Both in vitro synthesized DNA oligonucleotides and purified chromosomal DNA reacted strongly with 2,4-DNPH. Treatment of cell extracts with DNase+RNase or with Streptomycin sulfate to precipitate nucleic acids dramatically reduced the apparent carbonyl, while exposure to proteinase K did not. The commercial kit for immunochemical detection of protein carbonylation (OxyBlot from Chemicon/Millipore) recommends a high concentration of thiol in the homogenizing buffer. We found this recommendation leads to an artifactual doubling of the protein carbonyl, perhaps due to a thiol-stimulated Fenton reaction. Avoiding oxidizing conditions, removal of nucleic acids, and prompt assay of samples can prevent artifactual effects on protein carbonyl measurements.

BMC Microbiol. 2009; 9: 165
Gillor O, Giladi I, Riley MA

BACKGROUND: The ability of a bacterial strain to competitively exclude or displace other strains can be attributed to the production of narrow spectrum antimicrobials, the bacteriocins. In an attempt to evaluate the importance of bacteriocin production for Escherichia coli strain residence in the gastrointestinal tract, a murine model experimental evolution study was undertaken. RESULTS: Six colicin-producing, yet otherwise isogenic, E. coli strains were administered and established in the large intestine of Streptomycin-treated mice. The strains' persistence, population density, and doubling time were monitored over a period of 112 days. Early in the experiment only minor differences in population density between the various colicin-producing and the non-producing control strains were detected. However, over time, the density of the control strains plummeted, while that of the colicin-producing strains remained significantly higher (F(7,66) = 2.317; P < 0.0008). CONCLUSION: The data presented here support prior claims that bacteriocin production may play a significant role in the colonization of E. coli in the gastrointestinal tract. Further, this study suggests that the ability to produce bacteriocins may prove to be a critical factor in determining the success of establishing probiotic E. coli in the gastrointestinal tract of humans and animals.

BMC Microbiol. 2009; 9: 160
Rathbun KM, Hall JE, Thompson SA

BACKGROUND: Campylobacter jejuni is a gastrointestinal pathogen of humans, but part of the normal flora of poultry, and therefore grows well at the respective body temperatures of 37 degrees C and 42 degrees C. Proteomic studies on temperature regulation in C. jejuni strain 81-176 revealed the upregulation at 37 degrees C of Cj0596, a predicted periplasmic chaperone that is similar to proteins involved in outer membrane protein folding and virulence in other bacteria. RESULTS: The cj0596 gene was highly conserved in 24 strains and species of Campylobacter, implying the importance of this gene. To study the role that Cj0596 plays in C. jejuni pathogenesis, a mutant derivative of strain 81-176 was constructed in which the cj0596 gene was precisely deleted. A revertant of this mutant was isolated by restoring the gene to its original chromosomal location using Streptomycin counterselection. The cj0596 mutant strain demonstrated a slightly decreased growth rate and lower final growth yield, yet was more motile and more invasive of human intestinal epithelial cells than wild-type. In either single or mixed infections, the mutant was less able to colonize mice than 81-176. The cj0596 mutant also expressed altered levels of several proteins. CONCLUSION: Mutation of cj0596 has an effect on phenotypes related to C. jejuni pathogenesis, probably due to its role in the proper folding of critical outer membrane proteins.

RNA. 2009 Sep; 15(9): 1693-704
Gregory ST, Demirci H, Belardinelli R, Monshupanee T, Gualerzi C, Dahlberg AE, Jogl G

The RsmG methyltransferase is responsible for N(7) methylation of G527 of 16S rRNA in bacteria. Here, we report the identification of the Thermus thermophilus rsmG gene, the isolation of rsmG mutants, and the solution of RsmG X-ray crystal structures at up to 1.5 A resolution. Like their counterparts in other species, T. thermophilus rsmG mutants are weakly resistant to the aminoglycoside antibiotic Streptomycin. Growth competition experiments indicate a physiological cost to loss of RsmG activity, consistent with the conservation of the modification site in the decoding region of the ribosome. In contrast to Escherichia coli RsmG, which has been reported to recognize only intact 30S subunits, T. thermophilus RsmG shows no in vitro methylation activity against native 30S subunits, only low activity with 30S subunits at low magnesium concentration, and maximum activity with deproteinized 16S rRNA. Cofactor-bound crystal structures of RsmG reveal a positively charged surface area remote from the active site that binds an adenosine monophosphate molecule. We conclude that an early assembly intermediate is the most likely candidate for the biological substrate of RsmG.

Wei Sheng Wu Xue Bao. 2009 Apr 4; 49(4): 504-11
Cheng Y, Zhu W

OBJECTIVE: A molecular-based approach for anaerobic fungal community analysis was developed. The diversity of anaerobic fungi in the co-cultures with or without methanogens was analyzed by amplified ribosomal intergenic spacer analysis. METHODS: Co-cultures of anaerobic fungi and methanogens were obtained from rumen digesta using anaerobic fungal medium and the addition of penicillin and Streptomycin and ampicillin alternatively and then subcultured 15 times by transferring cultures every 3 d separately for each replicate. At the end of the third subcultures, the co-cultures were inoculated to another bottles adding with chloramphenicol to obtain fungal cultures without methanogens. Total DNA from the original rumen digesta and subcultured co-cultures and fungal cultures was used for amplified ribosomal intergenic spacer analysis. RESULTS: The diversity of anaerobic fungi decreased corresponding with the subculture of the co-cultures. The anaerobic fungi represented by 354-375 and 425-438 bp in the amplified ribosomal intergenic spacer analysis profiles were not deteched in the co-cultures after the second subcultures and the anaerobic fungi represented by 383, 389-391 and 413-418 bp were dominant along with the subcultures. The community of anaerobic fungi was different in the co-cultures with or without methanogens. The anaerobic fungi represented by 383.51, 391.44 and 413.55 bp in the amplified ribosomal intergenic spacer analysis profiles were dominant in the co-cultures with methanogens, while the anaerobic fungi represented by 415.80, 425.66, 437.46 and 438.47 bp were dominant in the co-cultures without methangens. CONCLUSION: The molecular-based approach amplified ribosomal intergenic spacer analysis was suitable for analysis of anaerobic fungi in the environmental samples. The diversity of anaerobic fungi decreased along with the subculture of the co-cultures and the anaerobic fungal community became stable after the 4th subculture of the co-cultures. The anaerobic fungal community was different in the co-cultures with or without methanogens.

BMC Microbiol. 2009; 9: 142
Spriggs AC, Dakora FD

BACKGROUND: Symbiotic N2 fixation in legumes is constrained by many factors, including the paucity of suitable soil rhizobia To maximise growth of legume species therefore often requires the application of effective rhizobia as inoculants. But where native strains out-compete introduced rhizobia for nodule formation, it is important that the competitiveness of selected strains is tested in the field and glasshouse prior to their recommendation as commercial inoculants. However the methodology for strain identification inside nodules has often proved difficult and thus limited this field of research. In this study, the suitability of the antibiotic resistance technique (both intrinsic low-resistance fingerprinting and high-resistance marking) and the serological indirect ELISA method were assessed for their ability to detect selected Cyclopia rhizobia under glasshouse and field conditions. The four rhizobial strains that were used, namely PPRICI3, UCT40a, UCT44b and UCT61a, were isolated from wild Cyclopia species growing in the Western Cape fynbos of South Africa. RESULTS: The test strains formed two distinct groups with regard to their intrinsic resistance to the antibiotics Streptomycin sulphate and spectinomycin dihydrochloride pentahydrate, making it impossible to use intrinsic antibiotic resistance to distinguish strains from within the same intrinsic resistance group. The use of strains marked with double antibiotic resistance was also investigated. A number of these strains lost their antibiotic marker tags after one plant passage; and some also lost their competitive ability. The indirect ELISA technique provided a more satisfactory method of identifying selected Cyclopia strains under both field and glasshouse conditions. The primary antibodies raised against strains UCT40a, UCT61a and UCT44b gave absorbance readings that were unambiguously negative (0.30 OD405), while those of strain PPRICI3 were ambiguous (0.50 OD405) with many false positive readings (1.0 A405). The indirect ELISA method showed a high level of analytical sensitivity in glasshouse experiments and there were no cross-reactions between the four test strains. The method was also suitable for detecting three of the four test strains in competition studies under field conditions, and can also be used to identify some strains under field conditions. CONCLUSION: The antibiotic marker method was found unsuitable for identifying Cyclopia rhizobia in competition experiments in both glasshouse and field conditions. However, the indirect ELISA technique was found suitable for identifying these strains in glasshouse studies. The method was also appropriate for identifying strains UCT40a, UCT44b and UCT61a, but not strain PPRICI3, in field competition studies.

Electrophoresis. 2009 Jul; 30(14): 2454-9
Liang J, Niu Q, Xu X, Luo Y, Zhou X, Deng Z, Wang Z

Nucleic acids remaining within bacterial protein samples from Streptomyces lividans and Escherichia coli were found to interfere significantly with blue native polyacrylamide gel electrophoresis (BN-PAGE), a technique used frequently for analyzing bacterial protein complexes in proteomics studies. We have used ultracentrifugation and/or precipitation of cell lysates with Streptomycin sulfate to eliminate nucleic acids from total and/or membrane protein samples. Nucleic acid-binding proteins were first enriched by precipitation with Streptomycin sulfate, and contaminating nucleic acids were then eliminated by precipitation by adding polyethyleneimine. The performance of BN-PAGE was found to be dramatically improved by these sample preparation steps.

RNA. 2009 Aug; 15(8): 1597-604
Llano-Sotelo B, Hickerson RP, Lancaster L, Noller HF, Mankin AS

Measuring the binding of antibiotics and other small-molecular-weight ligands to the 2.5 MDa ribosome often presents formidable challenges. Here, we describe a general method for studying binding of ligands to ribosomes that carry a site-specific fluorescent label covalently attached to one of the ribosomal proteins. As a proof of principle, an environment-sensitive fluorescent group was placed at several specific sites within the ribosomal protein S12. Small ribosomal subunits were reconstituted from native 16S rRNA, individually purified small subunit proteins, and fluorescently labeled S12. The fluorescence characteristics of the reconstituted subunits were affected by several antibiotics, including Streptomycin and neomycin, which bind in the vicinity of protein S12. The equilibrium dissociation constants of the drugs obtained using a conventional fluorometer were in good agreement with those observed using previously published methods and with measurements based on the use of radiolabeled Streptomycin. The newly developed method is rapid and sensitive, and can be used for determining thermodynamic and kinetic binding characteristics of antibiotics and other small ribosomal ligands. The method can readily be adapted for use in high-throughput screening assays.

PLoS One. 2009; 4(6): e5958
Bonnedahl J, Drobni M, Gauthier-Clerc M, Hernandez J, Granholm S, Kayser Y, Melhus A, Kahlmeter G, Waldenström J, Johansson A, Olsen B

Extended Spectrum beta-Lactamase (ESBL) producing Enterobacteriaceae started to appear in the 1980s, and have since emerged as some of the most significant hospital-acquired infections with Escherichia coli and Klebsiella being main players. More than 100 different ESBL types have been described, the most widespread being the CTX-M beta-lactamase enzymes (bla(CTX-M) genes). This study focuses on the zoonotic dissemination of ESBL bacteria, mainly CTX-M type, in the southern coastal region of France. We found that the level of general antibiotic resistance in single randomly selected E. coli isolates from wild Yellow-legged Gulls in France was high. Nearly half the isolates (47.1%) carried resistance to one or more antibiotics (in a panel of six antibiotics), and resistance to tetracycline, ampicillin and Streptomycin was most widespread. In an ESBL selective screen, 9.4% of the gulls carried ESBL producing bacteria and notably, 6% of the gulls carried bacteria harboring CTX-M-1 group of ESBL enzymes, a recently introduced and yet the most common clinical CTX-M group in France. Multi locus sequence type and phylogenetic group designations were established for the ESBL isolates, revealing that birds and humans share E. coli populations. Several ESBL producing E. coli isolated from birds were identical to or clustered with isolates with human origin. Hence, wild birds pick up E. coli of human origin, and with human resistance traits, and may accordingly also act as an environmental reservoir and melting pot of bacterial resistance with a potential to re-infect human populations.

Zhongguo Zhong Yao Za Zhi. 2009 Mar; 34(5): 611-4
Yang S, Wen H, Zhang G, Zhao S, Luo Y, Lu Q

OBJECTIVE: The effect of triptolide on the DNA methylation level of MMP-9 gene and the mRNA expression of tissue inhibitors of met-alloproteinases (TIMPs) were examined in human fibrosarcoma HT-1080 cells to explore the molecular mechanisms involved in the anticancer activity of triptolide. METHOD: HT-1080 cells were cultured in MEM containing 10% newborn calf serum and 1% penicillin-Streptomycin. Triptolide was dissolved in dimethyl sulfoxide (DMSO) at a concentration of 1 goL-1 and stored at -20 degrees C. Triptolide was freshly diluted with culture medium perior to use and directly added to cell cultures at the indicated concentration, and incubated for 72 hours at 37 degrees C in a humidified atmosphere with 5% CO2, with changes of reagents every 24 hours. Methylation specific PCR (MSP)was applied to assess the methylation status of MMP-9 gene promoter, and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was employed to measure the mRNA expression of tissue inhibitors of metalloproteinases (TIMPs) in human fibrosarcoma HT-1080 cells after 72 hours of treatment with 6 nmol x L(-1), 12 nmol x L(-1) or 18 nmol x L(-1) triptolide, respectively. RESULTS: The methylation index of MMP-9 gene promoter was statistically elevated in HT-1080 cells after 72 hours of treatment with 18 nmol L(-1) triptolide, compared with those in controls (0.61 +/- 0.10 vs 0.39 +/- 0.10, P < 0.05), while no significant difference was noted between 6 nmol x L(-1) or 12 nmol x L(-1) triptolide treated HT-1080 cells and controls (0.40 +/- 0.15 vs 0.39 +/- 0.10, 0.46 +/- 0.20 vs 0.39 +/- 0.10, respectively, both P > 0.05). The mRNA expression of TIMP-1, -2, -3 or -4 was not significantly changed in HT-1080 cells after 72 hours of treatment with the indicated concentrations of triptolide, respectively compared with those in controls (all P > 0.05). CONCLUSION: The results demonstrated that triptolide upregulates the methylation level of MMP-9 gene in HT-1080 cells in vitro.

Recent Pat Antiinfect Drug Discov. 2009 Jun; 4(2): 123-9
Savini V, Catavitello C, Bianco A, Balbinot A, D'Antonio D

Staphylococcus pasteuri is a coagulase-negative, Gram positive organism which is emerging as an agent of nosocomial infections and a blood derivatives contaminant, though its role in causing human disease mostly remains controversial. Despite the paucity of isolates recovered, this bacterium has recently appeared to express resistance against several classes of antibiotic compounds, such as methicillin/oxacillin, macrolides, lincosamides, streptogramins, tetracyclines, chloramphenicol, Streptomycin, fosfomycin, as well as quaternary ammonium compounds. Also, authors will discuss some essential patents related to the topic reviewed.

Roum Arch Microbiol Immunol. 2008 Jul-Dec; 67(3-4): 81-4
Măruţescu L, Sesan TE, Manole F

The fire blight disease was described for the first time in Romania, in 1992. Since then by continuous spreading, this disease has caused severe damages of the fruit trees production, particularly of the pear and quince orchards in different regions of the country, being advantaged by certain weather conditions (high temperatures and humidity). An epidemiological surveillance of this disease that was spreading over different regions of the country, has been instituted since 2002. During the year 2005 a total number of 785 samples were collected from the affected areas. The isolation and identification of Erwinia (E.) amylovora were performed on NSA and King's media and by indirect immunofluorescence (IFA) assay using monoclonal antiserum. Four hundred and fifty strains proved levan-type colonies on sucrose nutrient-agar and were IF-positive. Biochemical characterization of 46 selected strains, by help of the API 20E system, revealed a great homogeneity, for 80% of the strains, belonging to one of the two major API 20E profiles described for E. amylovora, the 20% remaining strains showing minor differences. Hypersensitivity test performed on tobacco leaves was positive. Six of the selected strains were susceptible to Streptomycin. The present study can be considered as the first attempt of phenotypic characterization of E. amylovora strains isolated from Romanian area.

ORL J Otorhinolaryngol Relat Spec. 2009; 71(3): 157-62
Kimitsuki T, Wakasaki T, Nawate A, Komune N, Takaiwa K, Ohashi M, Komune S

OBJECTIVE: This study evaluated the ability of dihydroStreptomycin (DHSM) to go through the mechano-electric transduction (MET) channels in hair cells under physiological conditions. Materials and Methods: Tall hair cells were isolated from the chick basilar membrane (cochlea). Mechanical stimulation was applied by a glass rod attached to a piezoelectric bimorph, and MET currents were recorded with a whole-cell patch technique. The voltage-dependent block of DHSM to MET channel was estimated by calculating the relative conductances (the ratio of MET current in DHSM saline to DHSM-free saline) at various membrane potentials. RESULTS AND CONCLUSION: At membrane potentials between -100 and +50 mV, DHSM behaves as a voltage-dependent blocker according to a partial block model. At membrane potentials more negative than -100 mV, however, DHSM blocking decreased. This finding differed from the partial block model, but indicated that DHSM escaped through the channel pore into the cytoplasm by acting as a permeant channel blocker due to the large electrical driving force.

J Bacteriol. 2009 Aug; 191(15): 4896-904
Tezuka T, Hara H, Ohnishi Y, Horinouchi S

Small noncoding RNAs (sRNAs) have been shown to control diverse cellular processes in prokaryotes. To identify and characterize novel bacterial sRNAs, a gram-positive, soil-inhabiting, filamentous bacterium, Streptomyces griseus, was examined, on the assumption that Streptomyces should express sRNAs as important regulators of morphological and physiological differentiation. By bioinformatics investigation, 54 sRNA candidates, which were encoded on intergenic regions of the S. griseus chromosome and were highly conserved in those of both Streptomyces coelicolor A3(2) and Streptomyces avermitilis, were selected. Of these 54 sRNA candidates, 17 transcripts were detected by Northern blot analysis of the total RNAs isolated from cells grown on solid medium. Then, the direction of transcription of each sRNA candidate gene was determined by S1 nuclease mapping, followed by exclusion of four sRNA candidates that were considered riboswitches of their downstream open reading frames (ORFs). Finally, a further sRNA candidate was excluded because it was cotranscribed with the upstream ORF determined by reverse transcription-PCR. Thus, 12 sRNAs ranging in size from 40 to 300 nucleotides were identified in S. griseus. Seven of them were apparently transcribed in a growth phase-dependent manner. Furthermore, of the 12 sRNAs, the expression profiles of 7 were significantly influenced by a mutation of adpA, which encodes the central transcriptional regulator of the A-factor regulatory cascade involved in both morphological differentiation and secondary metabolism in S. griseus. However, disruption of all 12 sRNA genes showed no detectable phenotypic changes; all the disruptants grew and formed aerial mycelium and spores with the same time course as the wild-type strain on various media and produced Streptomycin similarly to the wild-type strain.

Pol J Vet Sci. 2009; 12(1): 9-13
Kizerwetter-Swida M, Chrobak D, Rzewuska M, Binek M

We have evaluated 102 Staphylococcus intermedius isolates of canine origin for susceptibility to antimicrobial primary agents, i.e. penicillin, amoxicillin, amoxicillin with clavulanic acid, cefuroxime, trimethoprim/sulfonamides, neomycin, Streptomycin, gentamicin, norfloxacin, tetracycline, vancomycin, erythromycin and secondary agents, i.e., chloramphenicol, ciprofloxacin, lincomycin, teicoplanin, rifampicin, imipenem, mupirocin. Antimicrobial sensitivity was examined using the disk diffusion method and performed according to NCCLS quidelines. Methicillin resistance was detected using the disk diffusion method with oxacillin, and the occurrence of mecA gene was detected by PCR. Resistance to Streptomycin, penicillin, amoxicillin, neomycin, followed by tetracycline was predominant. From 14 mecA-positive strains, 12 were multidrug-resitant, and the remaining two showed atypical susceptibility. One strain resistant to oxacillin in the disc diffusion method was mecA-negative, suggesting a different mechanism of resistance. Our results indicate that the emergence of S. intermedius resistance to methicillin may be underestimated. In case of clinical multidrug-resitant S. intermedius isolates, resistance to methicillin should be considered.

Antimicrob Agents Chemother. 2009 Aug; 53(8): 3302-7
Fujiwara K, Shin M, Matsunaga H, Saita T, Larsson LI

Gentamicin (GM) is a widely used antibiotic but shows renal toxicity. We produced a serum against GM (anti-GM) conjugated to bovine serum albumin with N-(gamma-maleimidobutyryloxy)succinimide. The antiserum was monospecific for GM and did not cross-react with the analog Streptomycin, tobramycin, kanamycin, or amikacin. The antiserum also detected glutaraldehyde-fixed GM, and this enabled us to develop an immunocytochemical method for detecting the uptake of GM in rat kidney. Twelve hours after a single intravenous administration of GM, immunocytochemistry revealed that GM accumulated in the S1, S2, and S3 segments of the proximal tubules, as well as in the distal tubules and collecting ducts. By 12 h after injection, the drug was detected in cytoplasmic granules of the proximal tubule cells. However, early (1 h) after injection, drug accumulation was detected in the microvilli of these cells. The distal tubules and collecting ducts contained scattered swollen cells, reminiscent of necrotic cells, in which both the nuclei and the cytoplasm reacted strongly with GM. No staining occurred in the kidneys of saline-injected control rats. These results agree with previous studies showing that GM is endocytosed in the proximal tubules and accumulates in lysosomes. Additionally, our results show that GM also accumulates in the distal tubules and collecting ducts. This was achieved by systematically varying the pretreatment conditions-an approach necessary for detecting GM in different subcellular compartments. This approach should be useful for accurately detecting the uptake and toxicity of the antibiotic in different tissues.

Infect Immun. 2009 Jul; 77(7): 2932-42
Haneda T, Winter SE, Butler BP, Wilson RP, Tükel C, Winter MG, Godinez I, Tsolis RM, Bäumler AJ

Salmonella enterica serotype Typhimurium elicits acute neutrophil influx in the human intestinal mucosa within 1 or 2 days after infection, resulting in inflammatory diarrhea. In contrast, no overt symptoms are observed within the first 1 or 2 weeks after infection with S. enterica serotype Typhi. Here we show that introduction of the capsule-encoding viaB locus of serotype Typhi reduced the ability of serotype Typhimurium to elicit acute intestinal inflammation in a Streptomycin-pretreated mouse model. Serotype Typhimurium requires a functional invasion-associated type III secretion system (type III secretion system 1 [T3SS-1]) to elicit cecal inflammation within 48 h after infection of Streptomycin-pretreated mice, and the presence of the viaB locus reduced its invasiveness for human intestinal epithelial cells in vitro. However, a reduced activity of T3SS-1 could not account for the ability of the viaB locus to attenuate cecal inflammation, because introduction of the viaB locus into an invasion-deficient serotype Typhimurium strain (invA mutant) resulted in a significant reduction of pathology and inflammatory cytokine expression in the cecum 5 days after infection of mice. We conclude that a T3SS-1-independent mechanism contributes to the ability of the viaB locus to reduce intestinal inflammation.

Biochem Cell Biol. 2009 Jun; 87(3): 517-29
Nichols ER, Shadabi E, Craig DB

The role of translation error for Escherichia coli individual beta-galactosidase molecule catalytic and electrophoretic heterogeneity was investigated using CE-LIF. An E. coli rpsL mutant with a hyperaccurate translation phenotype produced enzyme molecules that exhibited significantly less catalytic heterogeneity but no reduction of electrophoretic heterogeneity. Enzyme expressed with Streptomycin-induced translation error had increased thermolability, lower activity, and no significant change to catalytic or electrophoretic heterogeneity. Modeling of the electrophoretic behaviour of beta-galactosidase suggested that variation of the hydrodynamic radius may be the most significant contributor to electrophoretic heterogeneity.

Appl Environ Microbiol. 2009 Jul; 75(14): 4919-22
Tanaka Y, Komatsu M, Okamoto S, Tokuyama S, Kaji A, Ikeda H, Ochi K

Certain Streptomycin resistance mutations (i.e., rpsL and rsmG) result in the overproduction of antibiotics in various actinomycetes. Moreover, rpsL rsmG double-mutant strains show a further increase in antibiotic production. rpsL but not rsmG mutations result in a marked enhancement of oligomycin production in Streptomyces avermitilis and erythromycin production in Saccharopolyspora erythraea, accompanied by increased transcription of a key developmental regulator gene, bldD, in the latter organism.

J Antibiot (Tokyo). 2009 Jun; 62(6): 319-23
Saeed MA, Haque A, Ali A, Mohsin M, Bashir S, Tariq A, Afzal A, Iftikhar T, Sarwar Y

Escherichia coli are one of the leading causes of infection in wounds. Emerging multiple drug resistance among E. coli poses a serious challenge to antimicrobial therapy for wounds. This study was conducted to ascertain a baseline profile of antimicrobial resistance in E. coli isolates infecting surgical wounds. A total of 64 pus samples from hospitalized patients were screened and 29 (45.3%) were found to have E. coli, which were identified biochemically and confirmed by molecular methods. Using the disc diffusion method, antimicrobial resistance was observed toward tetracycline (100%), cefradine (100%), nalidixic acid (93.1%), ampicillin (86.2%), gentamicin (86.2%), cefixime (82.8%), ceftriaxone (82.8%), aztreonam (82.8%), ciprofloxacin (75.9%), Streptomycin (72.4%), cefoperazone (65.5%), chloramphenicol (58.6%) and amikacin (58.6%). In an effort to find relevant genes, 11 different genes were targeted by PCR. Among these, the mutated gyrA gene was found to be the most prevalent (82.8%), followed by the TEM (72.4%), catP (68.9%), catA1 (68.9%), tetB (62.1%), blt (58.6%), bla(CTX-M-15) (27.6%), bla(TEM) (20.7%), bla(OXA) (17.2%), tetA (17.2%) and aadA1 (13.8%) genes. The presence of integrons was also studied among these isolates. The prevalence of class 1 integrons was the highest (44.8%), followed by class 2 (27.6%). Three (10.3%) isolates carried both class 1 and class 2 integrons (first report from E. coli infecting wounds). The high incidence of integrons points toward their facilitation for carriage of antimicrobial resistance genes; however, in nearly 37% isolates, no integrons were detected, indicating the significance of alternative mechanisms of gene transfer. Another salient finding was that all isolates were multidrug-resistant E. coli.