Bacterial Infections

a) Sepsis

  • SIRS (systemic inflammatory response syndrome)

SIRS is an upregulated inflammatory which affects the whole body.

– It can be due to both infectious and non-infectious stimuli e.g. bacteria, surgery, PE, anaphylaxis

– The term used to be used commonly but has now fallen out of favour.

– It is now more used to ensure that patients who are septic receive care as quickly as possible

 

Criteria:

i) Temperature <36ºC or >38ºC

ii) Heart rate > 90bpm

iii) Respiratory Rate >20/min

iv) WBC < 4 x 109 or >12 x 109

 

  • Sepsis

Sepsis is caused by a dysregulated response of the host’s own immune system responding to an infection and can lead to potentially lethal organ-dysfunction1.

– Usually due to a bacterial infection which enters blood from lungs, brain, UTI and skin

– This leads to unregulated inflammation leading to release of cytokines giving vasodilation

– This reduces blood pressure decreasing flow to kidneys (AKI) and other organs giving organ failure

– It is then followed by a prolonged period of low functioning of the immune system

 

SymptomsThese are red flags for sepsis

– BP –> <90mmHg or (- 40) than normal

– HR >130bpm

– RR > 25/min

– Non-blanching rash

– Urine output <0.5ml/kg/hr (AKI)

– Acute confusional state

 

Diagnosis – Originally it was defined as having 2 or more criteria for SIRS with a proven infection

– It is hard to diagnose so we use a screening tool –> quickSOFA score:  if 2 or more, then think sepsis

i) Respiratory rate > 22/min                    ii) Altered mentation                        iii) BP <100mmHg

 

Management – start Sepsis 6 protocol

  1. Give Oxygen
  2. Take Blood cultures
  3. Broad spectrum antibiotics
  4. Give IV fluids
  5. Measure lactate
  6. Measure urine output (catheter)

 

N.B. If left untreated, sepsis can progress to septic shock – where there is circulatory and metabolic compromise, patients can become unresponsive to fluids and needs to be managed by ICU.

 

  • Neutropenic sepsis

This is a complication of chemotherapy which results in sepsis due to the fact that you have destroyed a significant part of your immune system with cytotoxic drugs.

– It usually occurs 1-2 weeks after chemotherapy and is usually due to bacterial infections

 

Diagnosis – Defined (NICE)2 as neutrophil count of <0.5 x 109 who is having chemotherapy + at least:

i) Temperature > 38ºC                          or                          ii) Symptoms consistent with sepsis

 

ManagementCarry out the Sepsis 6 with a few modifications

– Start empirical antibiotic treatment immediately before getting blood test results –> 1st line is Tazocin

– If still unwell after 48 hours –> Try meropenem with optional vancomycin

– If not responding to treatment –> investigate for fungal infections with high resolution CT

 

N.B. If it is suspected that chemotherapy with reduce neutrophil count <0.5 x 109, you can give the patient prophylactic antibiotic treatment with fluoroquinolones

b) Other bacterial conditions

  • Toxic shock syndrome

This is a condition which is due to an inflammatory reaction to bacterial toxins.

– It is caused by S. Aureus or S. pyogenes usually and the toxin is usually TSS Toxin – 1

– This acts as a superantigen meaning it can stimulate T cells directly and does not need initial processing by an antigen-presenting cell –> T cells are activated giving a cytokine storm and unregulated inflammation.

 

Risk factors: Tampon use, skin lesions in young children

 

Symptoms – Diagnostic criteria (NNDSS)3:

– Fever –> Temperature > 38.9ºC

– Hypotension –> Systolic BP < 90mmHg

– Diffuse red rash- typically like a ‘sunburn’

– Desquamation of the rash occurs after 10+ days (affecting soles, palms and lips)

– Involvement of 3 or more organ systems e.g. GI (vomiting or diarrhoea at the start of disease), Kidney (urea or creatinine raised, indicating an AKI), Liver (abnormal liver function tests)

 

Treatment – Admit to ITU. IV antibiotics + removal/draining source of infection (e.g. remove tampon)

 

  • Lyme disease

The pathogen responsible for Lyme disease is the bacteria Borrelia burgdorferi.

– Transmission is via the Ixodes tick bite, so a major risk factor in the history is wondering in the forests

– It initially gives expanding area of redness on the skin at the site of the tick bite

– The bacteria can become systemic and spread to heart, joints and CNS where they can persist for years

– It is thought that due to molecular mimicry, it induces an autoimmune disease which leads to symptoms

SymptomsFever, arthralgia, malaise

– Starts with erythema migrans (rash at bite, ring of erythema with central clearing)

 

Complications:

– CNS –> can develop after a long time: meningitis, Bell’s palsy and neuropathy

– Polyarthritis –> lasts even after the bacteria have been eradicated

– Cardiovascular –> heart block, acute myocarditis

Diagnosis – Can be diagnosed clinically if erythema migrans is present

– 1st line is ELISA for antibodies –> if positive do immunoblot test for Lyme disease

 

Management – Patients should start treatment if suspected disease before the ELISA results come out

– If early disease –> Doxycycline                                                     – If late –> Ceftriaxone

           

  • Leptospirosis

This is an infection due to the bacteria Leptospira which cause a systemic infection

– Transmission is via contaminated rat urine infected through breaches in the skin/mucous membranes

– The bacteria spread to all organs, especially the liver damaging hepatocytes giving raised LFTs

– Upregulated inflammation to kill the bacteria also leads to interstitial nephritis giving AKI

Weil’s disease –> most severe form which gives jaundice

 

Risk factors: Sewage workers and farmers particularly

Symptoms:

– Fever + flu like symptoms

– Liver –> Jaundice + elevated LFTs

– Kidney –> AKI

– Bleeding (depletion of platelets) –> from lungs, gut, mucous membranes

– Subconjunctival haemorrhages

 

Tests – Serological testing for IgM to bacteria          

– FBC –> high WBC, low platelets, raised ESR and CRP

 

Management – Benzylpenicillin or Doxycycline

 

1. https://cks.nice.org.uk/sepsis#!scenario
2. https://cks.nice.org.uk/neutropenic-sepsis#!scenario
3. https://wwwn.cdc.gov/nndss/conditions/toxic-shock-syndrome-other-than-streptococcal/case-definition/2011/
4. James GathanyContent Providers(s): CDC/ James Gathany / Public domain
5. Cerevisae / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

 

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