Tags: Penicillin G

Borrelia & Leptospira Species

BORRELIA SPECIES RELAPSING FEVER Essentials of Diagnosis The most common presentation is fever with rash, headache, shaking chills, myalgias, arthralgias, and — during the acute phase — hepatosplenomegaly. Louse-borne relapsing fever (LBRF) is epidemic, caused by B. recurrentis, and characterized by one or two relapses. Tick-borne relapsing fever (TBRF) is endemic, caused by several Borrelia species, and characterized by multiple clinical relapses. Organisms can be visualized in blood smears of febrile patients, unlike other spirochetal pathogens, using dark-field microscopy or Giemsa or Wright stains. Helical (3-10 spirals) spirochetes, 8-30 um × 0.3 um, motile (flagella). Weil-Felix reaction: Proteus OX-K agglutinin titers are elevated (this is more common in LBRF). General Considerations […]

Lyme Disease

Essentials of Diagnosis Most common in the northeastern, upper midwestern, and western parts of the United States. Borrelia burgdorferi is the longest (20-30 um) and narrowest (0.2-0.3 um) spirochete member of the Borrelia genus and has the fewest flagella (7-11). Erythema migrans (EM) is a red expanding lesion with central clearing that is commonly seen during the early stage of Lyme disease. The most common systems affected are the skin (EM), the joints (arthritis), the CNS (facial palsy), and the heart (conduction defects). Serology is not standardized; it is insensitive in early infection and does not distinguish active from inactive infection. Grows in Barbour-Stoenner-Kelly medium from skin biopsy and other specimens. […]

Treponema Pallidum

Essentials of Diagnosis Spiral, motile, coil-shaped, elongated (0.10 um × 5-20 um) spirochete. No reliable method for sustained in vitro cultivation. Direct detection with darkfield microscopy or immunofluorescent antibody in early syphilis. Nontreponemal antibody tests (rapid plasma reagin, Venereal Disease Research Laboratory [VDRL]) for screening, treatment follow-up. Treponema-specific antibody tests (fluorescent treponemal antibody test, microhemagglutination-T pallidum test) for confirmation. Cerebrospinal fluid (CSF) lymphocytosis, elevated CSF protein, or reactive CSF VDRL test suggests neurosyphilis. PCR, DNA probes, and immunoblotting techniques promising in congenital syphilis, early syphilis, or neurosyphilis. All patients with T pallidum infection should be tested for HIV coinfection and vice versa. General Considerations The term syphilis was first used in […]


Actinomycetes are variably acid-fast, gram-positive bacilli that are sometimes filamentous and branched. Originally thought to be fungi due to their hyphae-like appearance, they are now recognized as bacteria based on their cell wall components, reproduction by fission without sporulation or budding, inhibition by antibacterial agents, and molecular phylogenetic analysis. The actinomycete chromosomes contain a high content of guanosine and cytosine. The actinomycetes include the genera Mycobacterium and Corynebacterium, which are discussed in site and site, respectively. The actinomycetes also include the genera Nocardia, Actinomyces, Rhodococcus, Tsukumurella, Gordona, Actinomadura, and Streptomyces, as well as the Whipple's disease bacillus Tropheryma whippelii. Of these, members of the genus Nocardia are the most significant from […]


Essentials of Diagnosis "Sulfur granules" in specimens and sinus tract drainage: hard, irregularly shaped, yellow particles measuring from 1 to 5 mm in size Gram-positive branching filaments arranged in ray-like projections under the microscope Colonies with characteristic "molar tooth" appearance Production of extensive fibrosis with "woody" induration No specific antibody or antigen detection tests General Considerations Epidemiology The Actinomyces species are facultative anaerobes that commonly inhabit the oral cavity, the gastrointestinal tract, and the female genital tract, where they exist as commensals. Diversity within this genus is broad, which has led to taxonomic revision and reclassification of some species as members of the Arcanobacterium genus, eg, Actinomyces pyogenes. Disease occurs when […]

Important Anaerobes

Essentials of Diagnosis Foul odor of draining purulence Presence of gas in tissues No organism growth on aerobic culture media Infection localized in the proximity of mucosal surface Presence of septic thrombophlebitis Tissue necrosis and abscess formation Association with malignancies (especially intestinal) Mixed organism morphologies on Gram stain General Considerations Epidemiology and Ecology Anaerobic bacteria are the predominant component of the normal microbial flora of the human body. The following sites harbor the vast majority of them: Skin Mostly gram-positive bacilli such as Propionibacterium acnes Gastrointestinal tract In the oral cavity Prevotella spp., Porphyromonas spp., Peptostreptococcus spp., microaerophillic streptococci, and Fusobacterium spp. are the most important anaerobes found; they significantly outnumber […]

Toxin-Mediated Infections

TETANUS Tetanus is a disease of global incidence produced by the toxin of Clostridium tetani. The risk of acquiring it increases in people > 60 years of age and in neonates, especially in Third World countries where poor sanitary conditions predispose to umbilical stump contamination. Immunization campaigns have played a crucial role in bringing about the observed decreasing incidence in the United States. The pathogenesis of tetanus involves the absorption of preformed toxin, or, less commonly, invasion of toxin-producing organisms from contaminated wounds; it may complicate surgical wounds colonized with C tetani. Incubation periods vary depending on the portal of entry. The toxin tetanospasmin blocks the transmission of inhibitory neurons, which […]

Neisseria Meningitidis

Essentials of Diagnosis Transmission in crowded or closed populations. Meningitis most common, but bacteremia, pneumonia, and other syndromes can occur in absence of meningitis. Disease often associated with petecchial or purpuric rash, which may involve palms and soles. Neutrophil-predominant cell profile in CSF, with low-glucose and high-protein concentrations. Gram-negative diplococci inside neutrophils on stained smears of CSF and aspirated skin lesions. Fastidious organism requires special media and growth conditions. Blood and CSF most useful specimens for recovery of organism. Improved sensitivity of detection with PCR in CSF, but not widely available. General Considerations Epidemiology N meningitidis is found only in humans and is a member of the normal oropharyngeal flora in […]

Gram-Positive Aerobic Bacilli

LISTERIA MONOCYTOGENES Essentials of Diagnosis Incriminated foods include unpasteurized milk, soft cheeses, undercooked poultry, and unwashed raw vegetables. Asymptomatic fecal and vaginal carriage can result in sporadic neonatal disease from transplacental and ascending routes of infection. Incubation period for foodborne transmission is 21 days. Organism causes disease especially in neonates, pregnant women, immunocompromised hosts, and elderly. Organism is grown from blood, cerebrospinal fluid (CSF), meconium, gastric washings, placenta, amniotic fluid, and other infected sites. General Considerations Epidemiology L monocytogenes is found in soil, fertilizer, sewage, and stream water; on plants; and in the intestinal tracts of many mammals. It is a foodborne pathogen that causes bacteremic illness and meningoencephalitis, with few […]


Essentials of Diagnosis Contact with infected animals, carcasses, hair, wool, or hides from goats, sheep, cattle, swine, horses, buffalo, or deer. Incubation period lasting 1-7 days, usually 2-5 days, after exposure. Painless lesion progressing to papule, to vesicle, to necrosis, and to eschar. Rapid development of chest pain, dyspnea, and circulatory collapse after brief flulike syndrome. Direct gram-stained smear and/or cultures of lesions or discharges. Widened mediastinum on chest radiograph in inhalational disease. General Considerations Anthrax is primarily a disease of herbivores, but humans acquire the disease through contact with infected animals or animal products. Epidemiology Historically, anthrax has been an occupational disease of persons who handle animal hair, skin, and […]