Chapter 29: Baffling bacterial infections

Bacterial infections can present diagnostic brain-teasers, and a high index of suspicion is needed to pinpoint the diagnosis. Many are rarely encountered, thus making diagnosis more difficult yet demanding vigilance and clinical flexibility.

The list includes:

• tuberculosis

• infective endocarditis

• syphilis

• septicaemia

• the zoonoses (e.g. brucellosis, Lyme disease)

• clostridial infections: tetanus, gas gangrene, puerperal infection, botulism, pseudomembranous colitis

• hidden suppuration: abscess, osteomyelitis

• mycoplasma infections: atypical pneumonia

• Chlamydia infections: psittacosis, non-specific arthritis, pelvic inflammatory disease, trachoma, atypical pneumonia

• legionnaire disease

• Hansen disease

Chlamydia and rickettsial organisms have been confirmed as being small bacterial organisms.

Tuberculosis

Tuberculosis (TB), caused by Mycobacterium tuberculosis, still has a worldwide distribution with a very high prevalence in Asian countries where 60–80% of children below the age of 14 years are affected.¹ This has special implication in Australia, where large numbers of Asian migrants are settling. The WHO estimates that one-third of the world’s population is infected by the tubercle bacillus. It remains a deadly disease with about 2 million people worldwide dying of TB every year and 8 million new cases a year.

Clinical features

TB can be a mimic of other diseases and a high level of suspicion is necessary to consider the diagnosis, especially if there are only extrapulmonary manifestations. There may be no symptoms or signs, even in advanced disease. Ideally patients should be referred early for specialist management.

High risk people/situations

• newborn and infants

• adults over 60 years

• patients with HIV/AIDS

• chronic disease, e.g. diabetes

• crowded or unsanitary living conditions

• people affected by alcohol and drugs

• immigrants and refugees from endemic countries (especially Indian sub-continent, Papua New guinea, South East Asia, Sub Sahara and South Africa)

Primary infection

The primary infection usually involves the lungs. Transmission is by droplet infection. The focus is usually subpleural in the upper to mid zones and is almost always accompanied by lymph node involvement.

Erythema nodosum may accompany the primary infection (see FIG. 29.1). Primary TB is symptomless in most cases although there may be a vague, ‘not feeling well’ illness associated with a cough. In most people this pulmonary focus heals but leaves some surviving tubercle bacilli, even if it becomes calcified (the Ghon focus).

Progressive primary tuberculosis

If the immune response is inadequate, progressive primary TB develops, with constitutional and pulmonary symptoms. Rarely, haematogenous spread can occur to the lungs (‘miliary tuberculosis’), to the pleural space (tuberculosis pleural effusion) or to extrapulmonary sites such as the meninges and bone.

Latent TB infection (LTBI)

LTBI is the presence of infection without evidence of active disease (contained by the immune system) and inability to transmit the infection. However, reactivation may occur if the host’s immune defences are impaired (occurs in about 10%). LTBI is very common in children in and from developing countries. Consider HIV in these people. The tubercular skin test is primarily intended to identify these people with a view to prophylaxis therapy. The standard preferred regimen is isoniazid (10 mg/kg up to 300 mg (o) daily for 6–9 months). This decision should be made by a consultant.

Post-primary or adult-type pulmonary TB

Most cases of TB in adults are due to reactivation of disease some years later and not to re-infection. Symptoms of active TB include persistent cough, sputum production, haemoptysis, fever, sweating, malaise, weight loss and anorexia. The factors causing this include poor social living conditions with malnutrition, diabetes and other factors lowering natural immunity, such as immunosuppressant drugs, corticosteroids, lymphoma and HIV infection (later stage). The chest X-ray is usually abnormal—classic apical disease with infiltration and cavitation with fibrotic changes.

Reactivated pulmonary TB

This usually presents with constitutional symptoms of poor health and night sweats, and a cough that is initially dry but may become productive and be bloodstained (see CHAPTER 42). Sometimes the infection will be asymptomatic. The natural history of TB is illustrated in FIGURE 29.2.

Extrapulmonary TB

The main sites of extrapulmonary disease (in order of frequency in Australia) are the lymph nodes (the commonest, especially in young adults and children), genitourinary tract (kidney, epididymis, Fallopian tubes), pleura and pericardium, the skeletal system (arthritis and osteomyelitis with cold abscess formation), CNS (meningitis and tuberculomas), the eye (choroiditis, iridocyclitis), the skin (lupus vulgaris), the adrenal glands (Addison disease—see CHAPTER 23) and the GIT (ileocaecal area and peritoneum). This is increasing, especially in HIV patients.

These sites are illustrated in FIGURE 29.3.

Miliary tuberculosis

This disorder follows diffuse dissemination of tubercle bacilli via the bloodstream especially in those with chronic disease and immunosuppression. It can occur within 3 years of the primary infection or much later because of reactivation.

The symptoms, which are insidious, include weight loss, fever and malaise. Choroidal tubercules are pathognomonic. The classic chest X-ray is multiple 1–2 mm nodules in lung fields. It is fatal without treatment.

TB in children³

Children living in close contact with people with smear-positive pulmonary TB are highly vulnerable to acquiring the primary infection. A possible complication is miliary TB. The lifetime risk of TB disease in children with LTBI is in the order of 5–15%.⁴ Children with LTBI should be considered for prophylaxis with a course of isoniazid.

Primary disease is the more common form in young children. Reactivation is more common in adolescents.

Diagnosis²

A high index of suspicion is critical for the diagnosis of TB. Tests include:

• Mantoux tuberculin test (TST) (a guide only)

• chest X-ray; CT scan if doubtful

• sputum or bronchial excretion or gastric aspirates for stain (acid-fast bacilli) and culture (takes about 6–8 weeks but important). Ideally requires 3 specimens over 3 days including one early morning

• immunochromatographic finger-prick test (new and promising)

• interferon gamma release assay (IGRA)

• NAAT/PCR test—less sensitive than culture

• biopsies on lesions/lymph nodes may be necessary. The hallmark is caseating granulomata

• fibre-optic bronchoscopy to obtain sputum may be necessary

• consider HIV studies

Tuberculin (Mantoux) testing and BCG vaccination

A tuberculin (Mantoux) test should be performed prior to BCG vaccination in all individuals over 6 months of age. (It is read at 48–72 hours.) It is not a good test to diagnose TB.

If area of induration:

• <5 mm—negative (note: may be negative in presence of very active pulmonary infection)

• 5–10 mm—typical of past BCG vaccination

• >5 mm—significant in immunocompromised, close contacts and HIV infection

• >10 mm—positive = tuberculosis infection (active or inactive)

• >15 mm—highly significant for ‘normal’ people

The BCG vaccination should be given if the reaction is <5 mm induration. Do not give it for a reaction >5 mm.

BCG vaccination is recommended for:

• ATSI neonates in regions of high incidence

• neonates born to patients with leprosy or family history of leprosy

• children <5 years travelling for long periods to countries of high TB prevalence

BCG vaccination should be considered for:

• neonates in household with immigrants or visitors recently arrived from countries of high prevalence (e.g. South-East Asia) (note: tuberculin test not necessary for neonates <14 days)

• children and adolescents <16 years with continued exposure to active TB patient and where isoniazid therapy is contraindicated

• others at increased risk (and where value of BCG vaccine uncertain), such as health care workers, travellers >5 years with significant exposure

BCG vaccination is contraindicated for:

• tuberculin reactions >5 mm

• immunocompromised or malignancies involving bone marrow lymphatics (can disseminate infection)

• high-risk HIV infection

• significant fever or intercurrent illness

• generalised skin diseases, including keloid tendency

• pregnancy

• previous infection

Areas of concern

Drug resistance

This includes the increasing emergence of forms resistant to two or more front-line drugs—multidrug-resistant TB (MDR-TB). TB is much more aggressive in the immunocompromised and if not adequately treated can be fatal in 2 months, especially if they have MDR-TB. Treatment compliance is a huge issue and so the directly observed therapy (DOT) strategy for isoniazid in children is a WHO priority, as is ‘DOTS plus’ to control MDR-TB. TB is a more pressing problem in children requiring early treatment.

Management and treatment^5,6

Referral to experienced specialist care is appropriate. The current antimicrobial treatment is to use four antituberculous drugs initially (rifampicin + isoniazid + pyrazinamide + ethambutol) daily for 2 months, then rifampicin + isoniazid daily for a further 4 months. The usual precautions with adverse reactions are required. Pyridoxine 25 mg daily is recommended for adults taking isoniazid. A 3-times-weekly regimen is also an option if DOT is employed. Corticosteroids may be prescribed. Notify appropriate jurisdictional public health authorities. Promote healthy lifestyle advice.

Syphilis

Although syphilis is uncommon, it is increasing in the general population. It is extremely common in certain Indigenous groups and is frequently acquired from sexual contacts overseas.^5,8

It presents either as a primary lesion or through the chance finding of positive syphilis serology. Family physicians should be alert to the various manifestations of secondary syphilis, which can cause difficulties in diagnosis. Congenital syphilis is rare where there is general serological screening of antenatal patients. Early syphilis—less than 2 years duration and based on positive serology—includes primary, secondary and latent syphilis.

Clinical features^7,8

Primary syphilis

The primary lesion or chancre usually develops at the point of inoculation after an incubation period averaging 21 days. The chancre is typically firm, painless, punched out and clean (see FIG 29.4). The adjacent lymph nodes are discretely enlarged, firm and non-suppurating. Any anorectal ulcer or sore should be considered as syphilis until proved otherwise.

Untreated, early clinical syphilis usually resolves spontaneously within 4 weeks, leading to latent disease, which may proceed to late destructive lesions.

Secondary syphilis

The interval between the appearance of the primary chancre and the onset of secondary manifestations varies from 6 to 12 weeks after infection. Constitutional symptoms, including fever, headache, malaise and general aches and pains, may precede or accompany the signs of secondary syphilis.

The most common feature of the secondary stage of infection is a rash, which is present in about 80% of cases. The rash is typically a symmetrical, generalised, coppery-red maculopapular eruption on the face, trunk, palms and soles and is neither itchy nor tender. It can resemble any skin disease except those characterised by vesicles.

Latent syphilis

Positive serology in a patient without symptoms or signs of disease is referred to as latent syphilis and is the commonest presentation of syphilis in Australia today. Possibly because of the widespread use of antibiotics, the infection often proceeds to the latent stage without a recognised primary or secondary stage.

Late (tertiary) syphilis

Tertiary manifestation of syphilis (follows >2 years latency), which is very rare, may be ‘benign’ with development of gummas (granulomatous lesions) in almost any organ, or more serious with cardiovascular or CNS involvement. Benign gummatous disease is rare but cardiovascular disease and neurosyphilis occasionally occur. Careful management and follow-up of patients with early or latent disease is essential to prevent late sequelae. It can only be detected by blood tests.

Neurosyphilis includes:

• meningovascular (e.g. cranial nerve palsies)

• tabes dorsalis (e.g. sensory ataxia, lightning pains, Charcot joints)

• general paresis of the insane (e.g. dementia, psychosis)

Think of syphilis

Syphilis should not be overlooked as a cause of oral, ocular or anorectal lesions. The diagnosis of syphilis depends on a detailed history, careful clinical examination and specific examinations.

Underlying these approaches is the need to think of the possibility of syphilis with concurrent STIs.

Syphilis and HIV infection⁸

HIV and syphilis are commonly associated. In patients with AIDS and syphilis, standard regimens for syphilis are not always curative. Seronegative syphilis has been reported in patients with HIV infection. Lymphadenopathy in a patient with HIV infection may be due to coexisting secondary syphilis.

Diagnosis

Dark field examination⁷

Spirochaetes can be demonstrated by microscopic examination of smears from early lesions using dark field techniques and provide an immediate diagnosis in symptomatic syphilis. The direct fluorescent antibody techniques (FTAABS) can be used on this smear.

Serology

Serological tests provide indirect evidence of infection, and the diagnosis of asymptomatic syphilis relies heavily on these tests. The main types of tests are:

• reagin tests (VDRL and RPR)—not specific for syphilis but useful for screening

• treponemal tests (TPPA, TPI, EIA, FTA-abs)—specific tests, with the latter being sensitive and widely used

• PCR (blood or CSF)—very sensitive

Treatment

Refer to CHAPTER 117.

Infective endocarditis

Infective endocarditis, although uncommon, has high morbidity and mortality. It can be a difficult problem to diagnose but must be considered in the differential diagnosis of fever, especially in patients with a history of cardiac valvular disorders. It is caused by microbial infection of the cardiac valves or endocardium. Previously referred to as bacterial endocarditis, the term infective endocarditis is preferred because not all the infecting organisms are bacteria.

It may present as a fulminating or acute infection but more commonly runs an insidious course and is referred to as subacute (bacterial) endocarditis. Its incidence is increasing, probably due to the increasing number of elderly people with degenerative valve disease, more invasive procedures, IV drug use and increased cardiac catheterisation.⁹

Risk factors

• Past history of endocarditis

• Rheumatically abnormal valves, especially ASTIP

• Congenitally abnormal valves

• Mitral valve prolapse

• Calcified aortic valve

• Congenital cardiac defects (e.g. VSD, PDA)

• Prosthetic valves, shunts, conduits

• IV drug use

• Central venous catheters

• Temporary pacemaker electrode catheters

Note: Only about 50% of patients with infective endocarditis have previously known heart disease.⁷

Responsible organisms¹⁰

• Streptococcus viridans (50% of cases) most susceptible to penicillin

• Streptococcus bovis

• Enterococcus faecalis

• Staphylococcus aureus (causes 50% of acute form)

• Candida albicans/Aspergillus (IV drug users)

• Staphylococcus epidermidis

• Coxiella burnetii (Q fever)

• HACEK group (Gram –ve bacilli) (5–10% of cases)

Presentations

• Acute endocarditis

• Subacute endocarditis

• Prosthetic endocarditis

Infective endocarditis without cardiac murmur is frequently seen in IV drug users who develop infection on the tricuspid valve.

Warning signs for development of endocarditis

• Change in character of heart murmur

• Development of a new murmur

• Unexplained fever and cardiac murmur = infective endocarditis (until proved otherwise)

• A febrile illness developing after instrumentation (e.g. urethral dilatation) or minor and major surgical procedures (e.g. dental extraction, tonsillectomy, abortion)

There is a significant high mortality and morbidity from infective endocarditis, which is often related to a delay in diagnosis.

Clinical features

The classic clinical features are summarised in FIGURE 29.5.

The patients are often elderly, appear pale and ill, with intermittent fever, and complain of vague aches and pains. The full clinical presentation takes time to develop. A febrile illness of 1 to 2 weeks duration is a common presentation.

Investigation

This includes:

• FBE and ESR: ESR ↑, anaemia and leukocytosis

• urine: proteinuria and microscopic haematuria

• blood culture: positive in about 75%⁷ (at least 3 sets of samples—aerobic and anaerobic culture)

• echocardiography—to visualise vegetations (TOE more sensitive than TTE)

• chest X-ray

• ECG

Consider kidney function tests and C-reactive protein.

Management

The patient should be referred because optimal management requires close cooperation between physician, microbiologist and cardiac surgeon.

Any underlying infection should be treated (e.g. drainage of dental abscess). Bactericidal antibiotics are chosen on the basis of the results of the blood culture and antibiotic sensitivities. Four blood cultures should be sent to the laboratory within the first hour of admission and treatment should seldom be delayed longer than 24 hours.

Antimicrobial treatment^10,11

Consultation with an infectious diseases physician or clinical microbiologist should be sought.

Empirical treatment¹¹

Once cultures have been taken, prompt empirical antimicrobial treatment should be commenced, especially in fulminating infection suspected to be endocarditis (usually due to Staphylococcus aureus). Benzylpenicillin, gentamicin and flucloxacillin/dicloxacillin are recommended, for example (adults):

• benzylpenicillin 1.8 g IV, 4 hourly

  plus

  flucloxacillin/dicloxacillin 2 g IV, 4 hourly

  plus

  gentamicin 4–6 mg/kg IV, daily

• Vancomycin is indicated in certain circumstances

For specific organisms isolated on culture and prosthetic valve endocarditis confer with a consultant.

Prevention

Antibiotic prophylaxis^10,11

The evidence for prophylaxis of endocarditis is not clear, and current international practice is not to treat low-risk cardiac abnormalities having procedures with a low incidence of bacteraemia.

It is advisable to discuss the relative risks with patients.

If in doubt, discuss the issue with the patient’s cardiologist or an infectious diseases specialist.^8,10

References for specific conditions: see References^5,12 and see also http://circ.ahajournals.org (Paediatrics).

Low-risk patients

These include patients with murmurs not due to valve disorders, isolated secundum ASD, pacemakers, implanted defibrillators, previous rheumatic fever without valve dysfunction, previous CABGS, mitral valve prolapse without regurgitation, complete surgical or device closures of congenital heart defects.

No prophylaxis is recommended in these patients.

High risk of adverse outcomes¹¹

These include past history of endocarditis, prosthetic heart valves, most congenital heart disease especially cyanotic types and those with repaired defects, hypertrophic cardiomyopathy, cardiac transplantation recipients who develop cardiac valvulopathy, rheumatic heart disease in Indigenous patients, all acquired valvular heart disease, mitral valve prolapse with regurgitation and surgically fashioned systemic-pulmonary shunts.

Procedures requiring prophylaxis¹¹

• Dental: invasive dental surgery—any procedure causing bleeding from gingiva, bone or mucosa, for example, dental extractions, drainage of abscess, osteotomies, dental implants, replanting avulsed teeth, periodontal procedures including probing, endodontic surgery, intraligamentary local anaesthetic injections, root canal work

• Other procedures—examples are:

  • – genitourinary procedures in the presence of infection, for example, D&C, IUCD, urethral dilatation, circumcision, prostatic surgery, vaginal delivery in presence of infection or prolonged labour

  • – gastrointestinal tract procedures in presence of infection

  • – respiratory tract procedures—tonsillectomy/adenoidectomy, rigid bronchoscopy, nasal and sinus surgery

  • – incision and drainage of local abscess, for example, boils, perirectal, dacryocystitis

Recommended antibiotics

Dental procedures and URT interventions (S. viridans and Streptococcus cover):¹¹

• phenoxymethylpenicillin 2 g (child 40 mg/kg up to 2 g) orally 1 hour before procedure

  or

• amoxycillin 2 g (child 50 mg/kg up to adult dose) orally 30 minutes beforehand (if not on long-term penicillin)

  or

• amoxy/ampicillin 2 g (50 mg/kg up to adult dose) IV just before procedure commences or IM 30 minutes before if having a general anaesthetic

  or

• if hypersensitive to penicillin: clindamycin or lincomycin

Genitourinary and gastrointestinal procedures¹¹

Enterococci prophylaxis

• amoxy/ampicillin (child: 50 mg/kg up to 2 g) IV (just before procedure)

  or

• amoxy/ampicillin 2 g (child 50 mg/kg up to 2 g) IM 30 minutes beforehand

If hypersensitive to penicillin: vancomycin or teicoplanin plus gentamicin.

Zoonoses are those diseases and infections that are naturally transmitted between vertebrate animals and humans (see TABLE 29.1). Zoonotic diseases (which are not restricted to farming communities) can present as a mild illness but are prolonged in duration and can have debilitating sequelae.¹⁴ There is a long list of diseases, which vary from country to country, and includes plague, rabies, scrub typhus, Lyme disease, tularaemia, hydatid disease, orf, anthrax, erysipeloid, listeriosis, campylobacteriosis and ornithosis (psittacosis).

Diagnosis¹⁵

If a zoonosis is overlooked in the differential diagnosis, many will remain undiagnosed and untreated.

Fever and sweats (flu-like illness)

Any patient with undiagnosed fever should be questioned about exposure to animals, recent travel both in and out of Australia, animal bites, cat scratches, consumption of raw milk, mosquito and tick bites, pets and occupation.

Rash

• Consider rickettsial illness such as leptospirosis, Q fever, Lyme disease

Cough or atypical pneumonia

• Consider Q fever, psittacosis, bovine TB

Arthralgia/arthritis

• Consider Lyme-like disease, Ross River fever

Meat workers

• Consider Q fever, leptospirosis, orf, anthrax

Papular/pustular lesions

• Consider orf, anthrax (black)

Brucellosis

Brucellosis (undulant fever, Malta fever) has diminished in prevalence since the campaign to eradicate it from cattle. Entry is mainly by the mouth, or abraded or cut skin.

Clinical features (acute brucellosis)

• Incubation period 1–3 weeks

• Insidious onset: malaise, headache, weakness

• A prolonged febrile illness

• The classic fever pattern is undulant (refer to CHAPTER 53)

Possible:

• arthralgia

• lymphadenopathy

• hepatomegaly

• spinal tenderness

• splenomegaly (if severe)

Complications such as epididymo-orchitis, osteomyelitis and endocarditis can occur. Localised infections in sites such as bones, joints, lungs, CSF, testes and cardiac valves are possible but uncommon.

Symptoms of chronic brucellosis are virtually indistinguishable from chronic fatigue syndrome and can present with FUO.

Diagnosis

• Blood cultures if febrile (positive in 50% during acute phase)^10,13

• Brucella agglutination test (rising titre)—acute and convalescent (3–4 weeks) samples

• Brucella PCR testing—sensitive and rapid

Treatment³

• Adults: doxycycline 100 mg (o) bd for 6 weeks + rifampicin 600 mg (o) daily for 6 weeks

  or

  gentamicin 4–6 mg/kg/day IV statim then daily for 2 weeks (monitor)

• Children: cotrimoxazole + rifampicin

  or

  gentamicin

• Relapses do occur (10%)—prolonged therapy

Prevention and control

Involves eradication of brucellosis in cattle, care handling infected animals and pasteurisation of milk. No vaccine is currently available for use in humans.

Q fever

Q fever is a zoonosis due to Coxiella burnetii. It is the most common abattoir-associated infection in Australia and can also occur in farmers and hunters. It usually resolves spontaneously within 2 weeks. Rash is not a major feature but can occur if the infection persists without treatment.

Clinical features

• Incubation period 1–3 weeks

• Sudden onset fever, rigors and myalgia

• Dry cough (may be pneumonia in 20%)¹³

• Petechial rash (if persisting infection)

• ± Abdominal pain

Persistent infection may cause pneumonia or endocarditis so patients with valvular disease are at risk of endocarditis (culture is negative). It is a rare cause of hepatitis. The acute illness may resolve spontaneously but a chronic relapsing disease may follow. Untreated chronic infection is usually fatal.

Diagnosis

• Serodiagnosis is by antibody levels in acute phase and 2–3 weeks later (4-fold increase)

• Coxiella burnetii PCR

Treatment³

• Doxycycline 100 mg (o) bd for 14 days

• For endocarditis or chronic disease: prolonged course of doxycycline plus clindamycin or rifampicin

• Children: >8 same antibiotics according to weight; <8 cotrimoxazole (instead of doxycycline)

Prevention

The disease can be prevented in abattoir workers by using Q fever vaccine.

Leptospirosis

Leptospirosis follows contamination of abraded or cut skin or mucous membranes with Leptospira-infected urine of many animals including pigs, cattle, horses, rats and dogs. In Australia it is almost exclusively an occupational infection¹⁴ of farmers (especially with flooded farmland in tropics) and workers in the meat industry. There is a risk to dairy farmers splashed with urine during milking. Early diagnosis is important to prevent it passing into the immune phase.

Clinical features

• Incubation period 3–20 days (average 10)

• Fever, chills, myalgia

• Severe headache

• Chest pain (possibly haemoptysis)

• Macular rash

• Light-sensitive conjunctivitis (marked suffusion)

Some may develop the immune phase (after an asymptomatic period of 1–3 days) with aseptic meningitis or jaundice and nephritis (icterohaemorrhagic fever, Weil syndrome) with a significant mortality.

Diagnosis

• High or rising titre of antibodies: can be cultured

Treatment⁵

Mild cases may not require treatment (adult doses shown).

• Doxycycline 100 mg (o) bd for 7 days

  or

• benzylpenicillin 1200 mg IV, 6 hourly for 7 days

  or

• ceftriaxone 1 g IV daily for 7 days

Lyme and lyme-like disease

Lyme disease (known as Lyme borreliosis) was first described in 1975 and named after the town Lyme in Connecticut (US). It is widespread in the US and is now appearing in other countries but is not endemic in Australia. Sporadic cases are seen in visitors or travellers. The illness encountered here and in other countries is described as debilitating symptom complexes attributed to ticks. Traditional Lyme disease, which is highly infective, is caused by a spirochaete, Borrelia burgdorferi, and transmitted by Ixodes ticks, so that people living and working in the bush are susceptible. It has been reported in deer farmers. Lyme disease presents in three stages. If suspected refer to an infectious disease physician for expert advice.

The pathognomic sign is erythema migrans—a characteristic pathognomonic rash, usually a doughnut-shaped, well-defined rash about 6 cm in diameter at the bite site.

• Stage 1: erythema migrans, flu-like illness

• Stage 2: neurological problems such as limb weakness and cardiac problems

• Stage 3: arthritis

Diagnosis

• Clinical pattern especially rash of erythema migrans + serology and PCR

Treatment

• Remove tick

• A typical regimen for adults is doxycycline 100 mg bd for 21 days or amoxycillin

Psittacosis (‘bird fanciers disease’)

Most patients are bird fanciers. Psittacosis accounts for 1–5% of hospital admissions for pneumonia. The disease may follow a low-grade course over several months but can have a dramatically acute presentation of flu-like illness. It is indistinguishable from other atypical pneumonias except for history of contact with birds.

Clinical features

• Incubation period 1–2 weeks

• Fever, malaise, myalgia

• Headache

• Cough (usually dry)

• Minimal chest signs

• Splenomegaly (sometimes)

Mortality can be as high as 20% if untreated.

Diagnosis

• Serology—rising antibody and PCR

• Chest X-ray

Treatment³

• Doxycycline 200 mg (o) or clarithromycin 250 mg, 12 hourly for 14 days (o)

Listeriosis¹⁵

Listeriosis is caused by Listeria monocytogenes, a bacterium widespread in nature that can contaminate food and has been found in many fresh (e.g. fruit and vegetables) and processed foods (e.g. dairy products, especially unpasteurised milk, soft cheese, processed meats and smoked seafood). Its significance lies in the mortality rate in high-risk groups such as pregnant women, the immunocompromised, frail aged, and very young but especially neonates and fetuses. Babies may be stillborn or aborted.

Clinical features

It may be subclinical but possible presentations include:

• influenza-like illness (usually mild)

• food poisoning, gastroenteritis (atypical)

• meningitis, especially infants, elderly

• septicaemia (in susceptible)

• pneumonia (in susceptible)

Diagnosis

• Microscopy, culture or isolation of organism from infected site or blood

• Serological tests available

Treatment

• Amoxycillin 1 g (o) 8 hourly or IV for 10–14 days^5,13

Other zoonoses

• Mosquito-transmitted infections: Murray Valley encephalitis, Ross River virus, Barmah Forest virus

• Infections from bites and scratches: cat-scratch disorder, rat bite fever

• Hydatid disease, orf, milker’s nodules

• Toxoplasmosis, histoplasmosis, hookworm

CLOSTRIDIAL INFECTIONS

Tetanus

This sometimes misdiagnosed bacterial infection (Clostridium tetani) can appear from one day to several months after the injury, which may have been forgotten. A total of 10–20% of patients with tetanus have no identifiable wound of entry.¹⁶ Neonatal tetanus can occur from contamination of the umbilical stump. It is a significant cause of postpartum maternal mortality worldwide.

Clinical features

• Prodrome: fever, malaise, headache

• Trismus (patient cannot open mouth)

• Risus sardonicus (a grin-like effect from hypertonic facial muscles)

• Opisthotonos (arched trunk with hyperextended neck)

• Spasms, precipitated by minimal stimuli

Differential diagnosis: phenothiazine toxicity, strychnine poisoning, rabies, dental abscess

Management

• Give tetanus antitoxin and human tetanus immunoglobin

• Refer immediately to expert centre

• Intubate and ventilate if necessary

Gangrene/Gas gangrene⁵

Gangrene (necrotising soft tissue infection) can involve skin and subcutaneous fat, fascia and muscle.

Gas gangrene (clostridial myonecrosis) is caused by entry of one of several clostridia organisms, for example, Clostridium perfringens, into devitalised tissue, such as exists following severe trauma to a leg.

Clinical features

• Sudden onset of pain and swelling in the contaminated wound

• Brownish serous exudate

• Gas in the tissue on palpation or X-ray

• Prostration and systemic toxicity

• Circulatory failure (‘shock’)

Management

• Refer immediately to surgical centre for debridement

• Start benzylpenicillin 2.4 g IV, 4 hourly + clindamycin

• Hyperbaric oxygen if available

Botulism⁵

Botulism is food poisoning caused by the neurotoxin of Clostridium botulinum. It can be infant botulism, of wound origin or food borne. From 12 to 36 hours after ingesting the toxin from canned, smoked or vacuum-packed food (e.g. home-canned vegetables or meat) visual problems such as diplopia suddenly appear. Suspect botulism if cranial nerve weakness with normal sensation. General muscle paralysis and prostration quickly develop. Refer immediately for antitoxin and intensive care.

PNEUMONIA

Surprisingly the initial presentation of pneumonia can be misleading, especially when the patient presents with constitutional symptoms such as fever, malaise and headache rather than respiratory symptoms. A cough, although usually present, can be relatively insignificant in the total clinical picture. This problem applies particularly to atypical pneumonia but can occur with bacterial pneumonia, especially lobar pneumonia (refer to CHAPTER 42).

The atypical pneumonias^5,12

Refer to CHAPTER 42.

Clinical features

• Fever, malaise

• Headache

• Minimal respiratory symptoms, non-productive cough

• Signs of consolidation absent

• Chest X-ray (diffuse infiltration) incompatible with chest signs

Serology tests and treatment

Blood tests and PCR tests are available for all the following causative organisms:

Mycoplasma pneumoniae (the commonest)

• Adolescents and young adults: treat with doxycycline (first line) 200 mg statim then 100 mg daily for 14 days

  or

  with roxithromycin 300 mg (o) daily for 14 days

Legionella pneumophila (legionnaire disease)

• Related to cooling systems in large buildings

• Incubation 2–10 days

• Diagnostic criteria include: prodromal-like illness; a dry cough, influenza-like illness, confusion or diarrhoea; lymphopenia with marked leukocytosis; hyponatraemia; PCR test and urinary antigen assay

• Treatment for mild disease: azithromycin 500 mg (o) daily for 5 days or doxycycline 100 mg (o) 12 hourly for 10–14 days

• Patients can become very prostrate with complications—treat with azithromycin (o or IV) or erythromycin (IV or o) plus (if very severe) add ciprofloxacin or rifampicin for 14–21 days

Chlamydia psittaci (psittacosis)

• Treat with doxycycline 100 mg bd for 14 days

Coxiella burnetii (see Q fever section)

Part of this text, on the clinical manifestations of syphilis, is reproduced from the Handbook on Sexually Transmitted Diseases⁸ (copyright Commonwealth of Australia, reproduced by permission).

World Health Organization. Guidelines for national tuberculosis programmes on the management of tuberculosis in children (2nd edn). Geneva: WHO, 2014. Available from: <http://apps.who.int/medicinedocs/documents/s21535en/s21535en.pdf>, accessed February 2018.

National Heart Foundation of New Zealand. Guidelines for prophylaxis of infective endocarditis associated with dental and other medical interventions.

Royal Children’s Hospital Melbourne. Guidelines for prophylaxis against infection in asplenic children. Melbourne: RCH, 2010.